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- Permanent Link:
- http://ufdc.ufl.edu/AA00055512/00005
Material Information
- Title:
- Electric power wheeling and dealing: technological considerations for increasing competition: volume II--contractor documents Part B
- Series Title:
- Electric power wheeling and dealing
- Creator:
- United States. Congress. Office of Technology Assessment
- Publisher:
- U.S. Congress. Office of Technology Assessment
- Publication Date:
- 1988-03-18
- Language:
- English
- Physical Description:
- 514 pages.
Subjects
- Subjects / Keywords:
- Electric utilities -- United States ( LCSH )
Electric power transmission -- United States ( LCSH ) Electric power distribution ( KWD )
- Genre:
- federal government publication ( marcgt )
Notes
- General Note:
- This report discusses the temporal and economic factors of electric utilities in United States that make transmission constrains vary with time, and material specific to the individual cases. A particular focus of the investigation was the degree to which the transmission system would limit, or be affected by, the various scenarios.
Record Information
- Source Institution:
- University of North Texas
- Holding Location:
- University of North Texas
- Rights Management:
- This item is a work of the U.S. federal government and not subject to copyright pursuant to 17 U.S.C. §105.
- Classification:
- Y 3.T 22/2:2 El 2/9/v.2/pt.B/elect. ( sudocs )
Aggregation Information
- IUF:
- University of Florida
- OTA:
- Office of Technology Assessment
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PAGE 1
ELECTRIC POWER WHEELING AND DEALING: Technological Considerations for Increasing Competition VOLUME II CONTRACTOr, DOCUMENTS Part B 1. Ca~e Studies on Increasing Transmission Access 2. Case Studies of Transmission Bottlenecks 3. Technological Considerations in Proposed Scsnarios for Increasing Competition in the Electric Utility Industry 4. Technical Background and Considerations in P. oposed Increased Wheeling, Transmission Access an Non-Utility Generation These Contractor Documents were preoared by outside con~ractors as an input to an OTA assessment. They do not necessarily reflect the analytical findings of OTA, the Advisory Panel, or the Technology Assessment Board.
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CASE STUDIES ON INCREASING TRANSMISSION ACCESS Prepared By: J.A. Casazza H.D. Limmer AJ. Schultz Casana. Schultz & Associates, Inc. 1901 North Fort Myer Drive Suite 503 Arlington. Virginia 22209 (703) 841-9644) March 18, 1988 This is a DRAFT OTA Workina Paper. It is beina circulated for review only and should not be quoted, reproduced, or distributed. The conclusions expressed in this report are those of the authors and do not necessarily represent the views of OT A. This report h3S not been reviewed or approved by the Technology Assessment Board.
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ACKNOWLEDGEMENT Casa~ Schultz & Auociatcs, Inc. would like to thank the personnel of the Southern California Edison Company, the Pennsylvania-New Jersey-Maryland Interconnection member companies, who devoted considerable time and thouahtful effort in providina information used in this report. While we cannot name them all, we do wish to partic:ularly thank: For the Southern California Edison Company Mr. Vikram Budhraja Mr. Arthur B. Cannina Mr. Ian Strauahn For the Pennsylvania-New Jersey-Maryland Interconnection Mr. Grayson E. McNair, Pennsylvania Power & Liaht Company Mr. Wayne G. Thompson, Baltimore Gu & Electric Company Mr. Thomas P. Welch, Philadelphia Electric Company We would also like to express our appreciation to the followina individuals in the Office of Technoloay Assessment for their con:structive advice and auistance: Mr. Alan Crane Dr. Robin Roy Ms. Karen Larsen
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TABLE OE CONUNTS I. EXECUTIVE SUMMARY . II. NATURE OF TRANSMISSION CONSTllAINTS A. Importance or Traumission Comtraintl . 1. Economic DiJpatcb . . . 2. Control Areas and Functions . . 3. Plannin1 and Opcntin1 Constraints 4. Ovenll National Picture . B. Technical Limitations to Tnnsrers 1. Individual Line Constraints . 2. System Constnints . . .. 3. Interrelationship or Constraints . 4. Preventive and Corrective Modes ,. Need for Reserves for Emeraencies . C. Temporal and Economic Facton Affectina Constraints Ill. BASIS AND APPROACH FOR CASE STUDIES . A. The Five Scenarios . . . B. Factors Investiaated and Buis for Sclectina Case Studies C. The SCE System and Tnnsmission Constraints. . D. Description or the PJM System and Transmission Constraints IV. SOUTHERN CALIFORNIA EDISON CASE STUDY ..... A. Means or Increuina Tnnsmission Capability .. B. Problems with Transmission Access and Wheelin1 C. Implementation or Dcre111lation Scenarios. . V. PJM INTERCONNEcrION CASE STUDY A. Means or lncreuina Tnnsmission Capacity B. Problems with Transmission Access and Wheelin1 C. Implementation or Dereaulation Scenarios. . APPENDICES A. Summaries or Transmission Conditions Around Country B. Expandina Transmission Capability: Corrective Technoloay Applications C. Expandina Transmission Capability: HVDC Terminal Expansion Project D. Expandina Transmission Capability: Use: or Phase Shifters I I I 3 s 8 8 8 11 12 14 14 IS I I 7 14 16 I I 2 s I I 7 8 E. Expandina Transmission Capability: Alternatives to Devers-Palo Verde 500-kV Line F. ~xpandina Transmission Capability: Rapid Adjustment of Network Impedance ACKNOWLEDGEMENT
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L EXECUTIVE SUMMARY The ability or the Southern California Edison Company and the Pennsylvania New Jersey-Maryland Interconnection (PJM) to meet the requirements or various proposed dereaulation scenarios bu been examined. (PJM is a contractual relationship amon1 ei1ht utilities ha the middle Atlantic area.) The technical implications or Cive alternative scenarios. each reprcsentin1 a diCCerent dearee or change in the rc1ulatory process or the electric power industry are reviewed. The scenarios arc a distillation or a variety or r,:oposals for in~!'easina competition in the industry. The Cive alternative scenarios ranae Crom what are essentially the existing utility circumstances with some modifications; throuab scenarios or expanded access to transmission and mandatory wheclina; to Cull competition Cor bulk power supplies and disa11re1ation or utility (unctions, which consists or separating the present vertically-intearated utilities into separate entities pcrformina, respectively, generation, transmission, and distribution (unctions. The scenarios arc shown in dct:iil in T:ibte III-I. A. particular Cocus or the investiaation was the dearee to which the transmission system would limit. or be affected by, the various scenarios. The report includes both aeneral material, in particular a discussion or the temporal and economic factors that make transmission coastraints v:iry with time, and material specific to the individual cases. The case-specific m:iterial includes a review or what can be done to increase transmission capability in the are:i involved, and an examination or what chanacs in plannina and operatina procedures :ind utility racilities would be needed in order to implement each or the rive scenarios. The analyses or both the SCE system and the PJM system have been conducted based on two rundumental around rules: I. The advantages or increased competition should not result in a decline in the reliability or the systems. 2. The present economic benefits rrom intercompany coordin:ition, which Casazza, Schultz & Associates, Inc. 1-1
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produces tbe areatat ovenll 1enentioa savinp compatible with reliability, aJaould not be aivea up i11 any or the scenarios. Thae arouad rules were chosen i11 order to show the consequences or the proposed dere111tatioa sccnarioa. ud to keep diem separate Crom the consequences or other decisiou which arc not neccuarily related to dere1ulation. For example, service reliability could be reduced u a delibente decision, in order t 1 reduce the cost or sc"icc. II the around rules were violated by accepti111 a redu tioa in reliability with one scenario bat not with another, it would be impossible to compare these two scenarios 011 their merits in other rapccts. such u their effect on plannin1 and opcratin1 procedures and 011 the physical system requirements. When either reliability or iatercompany coordination benefits were deemed to be arrected by a scenario, thorou1h discussions and i11vesti1ations were made of technical and procedural chan1es which mi1ht overcome the loss of these important economic benefits. For bodl systems investi1atcd, the utility participants stated that in discussing the diCCereat sceuri01 they were usumi111 that necessary le1islative chanaes would be made so that the utilitia would not be subject to retroactive prudency tests by future rea.ulaton after they implemented the scenarioL Consistent conclusions were reached for the two systems which were investigated, in spite or their very diCCerent locations. or1anization~. and technical situations. Both systems now have transmission limitations which advenely atrect the degree to wbicb optimum e11er1y transCen can be accommodated by their power supply systemL They ha vc ucd a areat variety of old and new technologies to increase their ability to transCer power for maximum economy. Althou1h there were some diCCereaces ia the expectations and concerns of the two systems about the various dere1ulation scenarios, the Collowina major conclusions were reached in both cues by the investiaators, with substantial aareement of the utilitia studied: Casazza, Schultz A Associat~ lac. 1
PAGE 7
1. IC the present level or reliability and present economics due to inter-utility coordiutioD are to be maintained. all units not owned by utilitia must be daianed, maintained. and operated in the same way that a similar utility-owned unit would be. nis requires that non-utility aeneraton (NUGs) should be subject to: direct opcratiJl1 control by providina ror the riaht or the utility (and the co11tract11al aad physical tools to implement such riaht) to connect. dilconnect. aad CODtrol power output ud voltaae or all connected units. reprdlca or ownenhip. to protect the reliability or the transmission system; central economic dispatch based on unit incremental ener1y production costs; tie line and frequency r,ontrol requirements; maintenance sched11li111 determined by the utility; operation so u to provide spinnina and rc1ulatin1 capacity; providina system reactive power requirements; and providina aeneration 111d connecti111 transmission desianed, operated, and maintained to utility standards. Failure to apply these rula i11 existi111 systems i11 which the non-utility units only amount to a small traction or the total system capacity may not have serious consequences. These concerns become particularly important. however, as non-utility generation becomes a more sianiricant portion or the total generation supply or larger NUG units arc installed. Theoretically, most or these requirements could be satisfied by includina appropriate provisions in all contracts between non-utility aenerators and the utility, transmission company, and/or distribution company, as applicable for each scenario. However, there are 1rounds Cor concern that present or future laws or re1ulations mi1ht not permit the utilities to require the needed provisions in the contracts, or that the contracts miaht not be effectively enforceable if it becomes advantaaeous to a non-utility power supplier to default on the contractual obli1ation. Even damaaes, it collected, do not replace required Casazza. Schultz & Associates, Inc. 1-3
PAGE 8
power supplia wbe11 power is needed. This leads to a aeneral conclusion that. even iC the utilities or their succcuon were to obtain the proposed contractual terms ill power supply contracts. the ultimate efCect would be a reduction in the reliability aad overall economy of the electric power supply. 2. Sceurios that involve mandatory wheelina without adequate notice. or that permit cutomcn to shop for suppliers. will require substantial additional trammissioa facilities. Present transmission systems are desianed to carry reuoubly predictable amounts from predietable sources to predictable loads. When these quantities and term.iuls become lea predictable, a much more extemive transmission system is needed to open additional markets to many diCCereat potential suppliers. Much or this additional transmission will not be used the majority or the time sine~ of tbe many potential sources ror which transmissio11 must be provided so that they can enter competitive biddina. only some will bid successfully to become reaular supplicn over the transmission system. 3. Competitio11 amoaa utilities to sell to customer loads and to buy from economic supplien will severely restrict inter-utility excbar:ae or inCotmation. and will make it diCCicult or impoaible to develop aeaeratioa plans coordinated on a reaional buis. and to plan and desian a well-i11te1rated reaional transmission system Cor maximum reliability and economy. Compctitio11 between utilities for power sources may also impair the coordination or operations Cor reliability and economy. Also, scenarios in which tbe customers are permitted to shop for suppliers will require laraer 1eneration reserves to be available to supply possible future loads. as uncertainty arows concernina the plans of customers and non-utility 1ener1tors. This will tend to increase aeneratioa requirements to maint:iin service reliability, since utilities. which currently have an obliaation to serve. must protect aaainst failure or non-utility aenerators to fulfill their capacity commitments. 111d must provide tor unexpected loads. by increasina their reserve 101ls. Casazza, Schultz A Auoci:ites, Inc. 1-4 0 4
PAGE 9
4. The cha111a ia utility plaui111 aad opcrati11 procedures which arc needed to maiAtalD euti111 reliability aad coordi1atio11 bcaerits would be substantial. especially tor the more radical dere111lation scenarios. and their costs could exceed 111y economic erricieacy benefits. Control or the system ror reliability 111d economy bccoma mach more comple1 u the 1111mber or parties involved multiplies due to the entry or maay small producen into the system. The number or control centcn would have to be iacrcucd, u well u their comple1ity and cost. Evea with couiderable expa111io11 ia the 1111mber or control centers. personnel usi111ed. computen and software and special trainina. the ability to maintain reliability remaiu questionable. 5. The various dere1ulatio11 scenarios will tend to result in increased dependence on natural aas and oil u fuel. and hence reduce the security of electric supply durin1 times or scarcity or these fuels. 6. Transactions that do not result in a chan1e in the aencration pattern cannot arrect the overall economic efficiency or the opcratin1 system; they only represent a reallocation of costs and benefits. This is not to say that there may not be some other 10111 ran1e effects Crom these tramactions. includin1 some socio economic chanaa and cun1a in iAcentiva. Table 1-1 summarizes the most important conclusions obtainec! in the case studies. A deliberate reduction in the accepted service reliability standard would reduce the aced for some of the chan1es which would be needed to maintain the uistina level or reliability. While 110 quantitative evaluation wu made of this relationship, it is the invcsti1ators' judaement that only a very serious reduction in service reliability would 1i1nificantly cbanae the conclusions or this report as to the chanaes needed to implement the dcre111lation scenarios. Such a reduction would have far-reachin1 consequences. aCCectina both the industrial eCCicicncy and the aeneral standard of livin1 of the nation. Casazza, Schultz A Associates, Inc. 1
PAGE 10
II
PAGE 11
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PAGE 12
. 111 J Ii~ ,~ -al i ; -I ~;U ~, ii I-7
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IL NA TUJlE OF TJlANSMJS-,ION CONSTRAINTS Transmission constraints can have a serious impact on the reliability and economy or power system operation. nil section discusses the nature and errect or transmission constraints. A. Importance or Trammission Constraints The errect of transmission constraints is to reduce reliability or increase reserve requirements u compared to the situation with no transmission constraints. They may also interfere with economic power system operations and, in particular, with the practice or economic dispatch. Some examples or the impacts or transmission constraints are: 1. On reliability: In determinin1 1eneratin1 capacity reserve requirements, the planned capacity and projected loads or adjoinin1 power systems are 1cnerally reco1nized. If a transmission constraint prevents the full amount of capacity needt Crom bein1 imported or available 1eneratin1 capacity from bein1 exported, the reserves IIUllt be laraer to maintain the same level or reliability. 2. On economic dispatch: economic dispatch based on incremental production osts is the universally reco1nized principle Cor lo1din1 the 1enerators or an electric system. nis metJlod produces the lowest total cost of energy production. Transmission constraints can result in uneconomic dispatch to alleviate line loadinp. 1. Economic DIJpatch Today's electric power systems are bcin1 dispatched and operated based on the incremental costs or production. This 1ener1l practice often results in one utility producin1 electricity ror use by anoth~r utility's customers since the first utility can produce the power at a lower cost. This Jcds to ma,dmum, economic eCCiciency in the uao of the invcacmcnc and in the c;ou or opcrarin1 thcac svuems, No other industry in the United States operates in this way, whereby alternate suppliers all Casazza, Schultz & Associates, Inc. 11
PAGE 14
work toaether to produce a common product. usina plants which have the lowest incremental cost to produce the additional units needed reaardless of plant ownership. The only exception to this production based on incremental costs has resulted Crom the recent addition or coaeneraton 111d qualiCyina facilities. The proposed addition or independent power producers could increase further the amount or generation that is not economically operated based on incremental production costs. The incremental production cost of a 1eneratin1 unit is the additional cost per kilowatt-hour or 1e11eratin1 a small additional quantity of eneray from that unit or the cost reduction per kwh due to 1eneratin1 a lesser quantity of energy. Generally, this incremental cost consists mostly or additional fuel costs, but it also includes any other operation costs that vary with the level of power production. The incremental cost or a aenerator is affected mostly by the cost of its fuel and by how efficiently it converts this fuel into electric power. For a typical thermal unit, the incremental cost increases as production increues Crom the minimum to the maximum rated output. The incremental cost or a unit is not the same as its averaae cost. which aenerally decreases as its output increases. Fi au res 11-1 a and lllb illustrate this point Cor a typical aeneratina unit. Fiaure II-la is a simplified input-output curve, which shows the total cost or operatin1 the unit. in dollars per hour, as a function or the output in meaawatts. Fi1ure 11 b shows the average cost lsolid line) and incremental cost (dotted line) Cor that unit. The average production cost at any output level ia obtained by dividing the cost by the output; this value generally decreases as output increases. The incremental production cost, however, is represented by the of the input-output curve, because it indicates the additional cost or increasing output by one megawatt. This quantity generally increases as unit output increases. Economic dispaJch consists of supplyin1 th, system's total power rtquirtments at any litrN by loadint 1ach a,ailablt unit 10 th, point whert its incrtmtnlal cost is th sam 41 that of all tht oth,rs. Units whose highest incremental cost is lower than the common incremental cost are, of course, loaded to their maximum c:ipability. In performing economic dispatch to minimize total power production costs, the limitations on the transmission system's capability to transfer power reliably must CHazza, Schultz A Associates, Inc. 11
PAGE 15
be observed. If economic dispatch causes too much power to be transferred from one area to another, it is necessary to reduce the output of units in the sending area. and increase the output of units in the rcceivin1 area. This deviation from economic dispatch in order to observe transmission constraints causes a cost increase due to those transmission constraints. The prinr.iple or economic dispatch is almost universally observed within individual utilities, which frequently implement it with automatic computer control of generator outputs. The same principle is also very widely applied in inter-utility transactions. IC one utility is operatin1 at a hiaher system incremental cost than another, the former will buy cncray from the latter until the incremental costs arc matched or until transmission constraints are reached. This type or transaction is sometimes very hiahly automated, as in the case of the PJM Interconnection. In other cases, the process is 1~ automated and is carried out throuah brokcra1e systems or through individual transactions neaotiatcd by system operators using telephones or small computer networks. It is important to note that inter-utility transactions arc implemented simply by incrcasina the aeneration of the selling utility and decreasing that of the buying utility. When two systems are connected to each other by more than one transmission link, whether directly or indirectly throuah other utilities, it is not possible to direct a power interchanac along a specific link. The power flows between the systems in accordance with the physical laws that 1ovcrn the flow of electricity. The importance of this fact, and the existence of one exception, will be seen in the discussion of the nature and causes of transmission constraints. 2. Control Area.s and Functions In the United States, all electric utilities are connected to neighboring utilities throuah one or more links. Except where contrary arrangements are specifically made, it is the responsibility of each utility to provide the power used by its customers without absorbing power from its neighbors or sending unwanted power to them. This acncral principle is implemented through the institution of control areas. Casazza, Schultz & Associates, Inc. 11-3
PAGE 16
, / / MW output (a) Total Production Cost Curve --------, __ MW output (b) Incremental Cost Average Cost Incremental and Average Production Cost Curve FIGURE II-1 Casazza. Schultz ct Associates, Inc. 11-4
PAGE 17
A control area is a utility or aroup of utilities with the following characteristics: The power now across every transmission link between the control area and neia,hborina control areas is monitored by the control area operating center. Automatic controls adjuat the output or aenerators inside the control area in such a way that the total power transferred across the borders or the control area is equal to the net sales or purchases transacted between the utilities inside and outside the control area. Every utility in the United States is, or is part of, a control area. The operation or control areas ensures that the utilities within the control area, taken as a group, will fulfill their responsibility or providing for their own loads and carry out scheduled transactions. While, as mentioned earlier, they cannot ensure sp~cific flows along specific transmission line~ they do provide a form or control in the sense that the flows over aiven transmission lines can be predicted for a given transaction schedule, usina the control computen ot the various control areas. A map of the principal control areas or the United States is shown in Figure 11-2. Control areas also cooperate with each other to maintain the power supply frequency at 60 Hertz by adjusting their aeneration whenever the frequency begins to deviate Crom the standard. Transmission capacity must be reserved for this function since sianificant frequency deviations are generally caused by the loss of a major power source, such as a complete power plant, and this will cause major power in rushes throughout an extensive geographic area. 3. Planning and Op~raling Constraints Transmission constraints affect both the operation and the planning of power systems, but do so in different ways. Most utilities have developed system pl:inning criteria which set the conditions that must exist on the system if various contingencies occur. For example, the planning criteria might specify that norm:il economic disp:itch should be possible without exceeding transmission limitations both when the transmission system is in a normal state (all facilities in service), and also under certain continaencies, such as the loss of specific individual facilities because of maintenance Casazza, Schultz & Associates, Inc. 11-5
PAGE 18
II II
PAGE 19
.. ii ~ I I ., i i 4 I ., ,, ., ii \ ..a 0 0 u Q Ill t u .. Ill z .. z 0 'II u Ill t.. !: a i z I !::! .. Cf: .-4 Ill :I ... 0 ... ... 0 a z N I M M I a, ,.. ::, -"' .-,i f&e I / I i II lij I Ii: I J~! I : i i jl' g i rn; ; ,. .. I s d1 01+ .. A ,. I I I
PAGE 20
or forced outaaes. The specific conditions under which economic dispatch is to be feasible would depend on I number or factors. including: the cost or additional facilities needed to remove the transmission limitation; the likelihood or the continaency; the probable duratioa or he continaency; and the economic penalties which would result from deviatina from economic dispatch. Most often, systems are planned to operate with economic dispatch under any single continaency, that is with the loss or any one element. Some multiple contingencies may also be contemplated. In system operation, the problem is different: ,, The fundamental criterion is to achieve econo~y within the established reliability constraints aimed at maintaining continuity of service. Economy or operation. will be modified as necessary to maintain adequate system reliability and resultina continuity. The operator is limited to the use or those facilities which are installed and available at the time (not under1oin1 maintenance, and not out or service because or forced outaacs). He can only operate those aenerators which are connected to the system; other units would require time periods ran1in1 Crom a Cew min~tes to several days to be pla..ced in operation. Service reliability requires that the system should be able to continue functioning without overloads, excessive voltaae drops, or instability even iC any single component should Cail without notice due to equipment breakdown, li1htnin1 strikes, etc. This is called the principle of n-1 operation: and it applies at all times, even when some elements are already out of service. For example, if three lines are out of service, the system's operation must be adjusted so that it will be able to stand the loss of a fourth line. Thus, transmission limitations in system operation change whenever a component or the system fails, is taken out or service, or is returned to service. The location Casazza, Schultz A Associates, Inc. 11-7
PAGE 21
or transmission limitations will also chanae due to variations in generation output ... and area loads. 4. 0,1rall Nalional Pictur, The pace or transmission construction in the United States has slowed steadily over the last Cew years. Fiaure 11 shows the ten-year forecasts or transmission additions or U.S. and Canadian utilities Crom 1914 through 1987. For each year, the amount or transmission planned to be built in the United States in the next ten years bas been reduced. There hu not been as sianiCicant a trend in Canada u in the U.S. There are many possible reasons for this trend. One or them may be the decrease in the amount or utility-planned aeneration over the same period. However, there may be other reasons such as the difficulty or getting lines built due to sitina and other environmental requirements, and a reluctance to take the risks involved in buildina trinsmissio~ when after taking these risks, the owner may be Corced to make transmission capacity available to competitors r or their transactions. B. Technical Limitations to Transfers The technical limitations to transf'en are related to the need to maintain reliable service and prevent damaae to the transmission equipment. Each component or a transmission syste~ in particular, transmission lines and transformers, have individual limitations on their capability to carry power. However, the system as a whole has its own limitations which are considerably less than the sum or the limitations or individual components. I. Individual LiM Constraints Every transmission line has a limit on the amount or power that it can transmit. One or the factors that causes. the limitation is a thermal consideration. Current causes heating in the conductor. Excessive current may he:u the conductor to a point at which the metal characteristics are aCCected, leading to brittleness and a shortening or expected life. In other cases, overheating of the conductor may cause the wires to sag excessively, brinaing them too close to the around and creating a Casazza, Schultz & Associates, Inc. 11-1
PAGE 22
Source: FIGURE II-3 PLANNED TRANSMISSION ADDmONS NEAC-U.S. NERC-CANADA QZZ
PAGE 23
safety hazard. At other times, the thermal limitation may aCCect a relatively minor element or the transmiaion line: a disconnect switc~ a wave trap at one oC the terminals, or some meterin1 equipmenL A thermally overloaded component will reach its critical temperature within seconds. minutes, or hoan. dcpendina on its s,revioas temperature, its physical characteristics. ud the amout or the overload. ncreCore it may be able to carry a heavy current Cor a short time. a laser one Cor a lonaer time, and a still lesser oac indefinitely. The latter current will be treated u a normar ratina. applicable to operation without contin1cncics. 9Emcracncy ratinp are currents that can be carried Cor shorter times, 011 the unmption that the loadinp can be relieved by chanaes in 1encration dispatch within the usipcd time period. Thermal ratiDp arc usually established Cor loadinas occurrin1 for different periods of time 10 minutes, 30 minutes, .C boun. etc. Sianificant variations in the ratina of identical physical transmission facilities arc possible. These differences may be due to: ne electrical/physical characteristics of the equipment includina equipment coolina. etc.; nc ambient weather conditions incladin1 temperature, insolation, and wind speed; The loss-of-life considered acceptable by the utility for the transmission equipment; Seasonal weather variations; Expected circuit load and loss facton; The type of contin1c11cies that it is reasonable to assume; The impact of a aeneration continaency venus a transmission continaency; The duration of the loadina. due either to the contin1ency or the type of transCer that may be considered; Availability of potential adjustments for 1eneration redispatch and changes in system confiauration; and Expected loadina conditions prior to the continaency on that circuit Casazza, Schultz cl Associates, Inc. 11-10
PAGE 24
ne tnamiaioa 1J1taa couilts or muy compoaeaa which are hnercouected widl acll ott.: ia a UJ complu way. n. liaitatioa oa bow m11cb power can be trullcrnd rroa w ana to uoocr bJ CM mU1Diaioa 1mm is die smallat power traUlcr at wuc:11 oac or tM coapoacaa raclla its iJadividul thermal ratina. or at wlucla uy portioa or die 1JSta1 rcaclaa a oltaae coutraiat or a stability liait. Voltaac liaitatiou apply wllca. U I renlt or llayY power nows. tbc volta1e at tJac rec:eiriaa area rcaclaa a llliai acceptable level ud caanot be raised by iacreuiaa voltaic ia die sndiaa area. lccauc or tlac complex rclatiouhips between oltaaa at all poiaa ia the tno,.iaioa system. vol~I limitations must be trcucd u system problems, rather tJau auociated witb oae specific component. Stability limits are or two typa: steady state and transient. Ia a normally opcrati111 system. all acaeraton operate in 17acllroaism. i.e.. at euctly the same speed. A saall distarbuce iacreuia1 or dccrcuia1 the speed or one 1caerator will cauc ...U clauaa ia power O11tsnat -~ ill tead to bria1 tlaat 1cncrator back to tile coemo~ spad or ~ 1J11C1L Steady-aatc iutability ii a condition ill wlaicJI. U a renlt or ucaaive power nows. tlUI stabilizilll procca doa IOt occur, aad some aeacraton ss,Nd -.ap witll respect to the others. causia1 the transmission system to rail apart. Trauicnt instability is a more common pbcnomcnoa. ia which a similar loa or syachronou operation results Crom i severe disturbance such u a short circuit aad loa or a tnnsmiuion liac. or the suddca Joa or a aeacrator or or a larac load. (Tlac loa or individual 1cacnton or trallSlllission lilla arc relatively (rcqaeat eveats; u a rault or system dai1n and opcratin1 practices. however, they rarely arrcct service to the cutomcr.) In sammary, transmission capability may be limited by thermal, vo1ti1e. or stability constraints. nae may be cloae toaether so that relier or one constraiat may only increase the system capability by a small amount. Similarly, a consuiint due to one particular outa1e contia1ency may be close to a constraint due to a diUercat contin1cncy. Thus a substantial invatmcnt to relieve tbc most critial constraint Cua~ Schultz & Aaociata, Inc. 11 l
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may aot ralllt iJa macJa improvemc11t. Allo the coutnction or 111 additional line may improve da systaa's capability by oaly a Crac:tio11 or that line's individual capacity. Tu tran1JDipi4>a capability or a system may be limited by normal or emeraency c:oasictuatiou. la tlN rormcr cue. the llmitatiou occur in the system as it is coatiared. Either oae or more compoacatl laave reached their thermal limit. or die IJ'ltC1III u a wlloa. reaclla a voltaae limitatio11 or a stability limiL However, IIIOlt or the time. tJac limit oa die tranmia,oa capability concerns a possible coatiapacy. For ple, ca1C111atiou _., sJaow that witJa a system carryi.111 a ai..a aaoaat ot power, ii a si,ccillc luae were to trip out. another line would be loaded beyond ils emerpaey rati111-Smee the opcnti111 rules require that the system 1111111 be able to npply scnicc even ii 111y oae compo11e11t should rail suddenly, the system may aot be loaded beyoad s11da a coati111cney limiL Thus the tnasmission system's capability or carryi111 power ii limited not by the actual nows. but by the nows tut woald exist if a aivea coatia1c11ey shOGld occur. Por 111wple. tJac very liwplilied sjstna iJa Fi111r1 II-la shows three lines linkina die ... entor oa die left to die load on die ript. lccaue or diCCerent path le111ths. tM total power tnuained dlvida aaeqaally on tllc three lines. In the example, it is aaamed tlaat tJae division is in tJac ratios or 10:9:1. Eacb individual line is capable or carryi111 100 MW. Witll all lines in service. wben Line A carries its rued power or 100 MW, tlle total power tnulcr is 270 MW because Lines B and C carry only 90 MW and IO MW respectively; any attempt to transmit more power would i11cr1UC tlle loadi111 oa all the liaa and overload Li11e A. However, tile are traummioa limit is much less. Ir Line B were to trip out, Line A would be loaded to UO MW 111d Linc C to 120 MW (sec Fi1\;re ll-4b). In order to pr1veat 111 overload uader the a-1 operation principle, the power tr~nsfer must be reduced to 110 MW. Then the normal loadinp are limited 10 only 67, 60, and 53 MW respectively (Fi1ure II~) and the emer1ency lo1din1s do not exceed the ratin1 or 100 MW (Fi111re 11-'d). The three 100-MW lines Corm a system c3p1blc: or 11Cely c1rryi111 only 110 MW. Casazza. Scbultz & Auoc:iata. Inc. 11
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l .~ .. I -A ,~ = 100 FIGUllE II-4 r, :; s ..... .',.) ~I., -.. _..., I B ""f'-=-,-zc, -:> TJlANSMISSION SYSTEM LIMIT A TJONS (ALL LINES 1lA TED 100 MW) A 100 90 C 80 270 Kt (1) All Una in service. System loaded without comidcri111 con tl111cncia. Lint A. at rated loadi111B C (c) All lines in. 67 60 53 System loaded to -1 co11ti111c11c:y limit Cuam. Schultz A Associates. Inc. MW 11 A 150 B C 120 (b) Outa1c or Linc B 270 !-Ii System loaded without cocsidcrina co11 d111encies. Ll11cs A and C overloaded. A 100 .. C 80 (d) Oucaac or Line B System wu loaded to nl co1nin1cncy limit betore Linc I tripped. Line A ac limiL No overloads.
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4. P,~,,nti',, and Corr,cti,, Mod~s The concept of n-1 opention: wu defined earlier as opcratina in such a way that after any sinale continaency, the transmission system would still be within, at least, emer1ency ratinp. This mode of operation is sometimes referred to as preventive to indicate that all provisions to protect the system arc taken before any continaency occurs. Preventive operation is the rule in the great majority of utilities in the United States. It provides the best reliability of service. There ar'9 however, some situations in which the preventive mode is not applied, and the system relics on immediate automatic action after the contingency occurs to prevent overloads that will damaae equipment or threaten human safety, or excessively low voltaaes that would cause damage, or malfunctions, to utility or consumer equipment. Such a mode of action is referred to as corrective, remedial, or reactive. Corrective action miaht involve such measures as tripping a generator, sheddina some customer load, or rearran1in1 transmission by connecting two buses toaether, when a specific continacncy occurs. It would be used when preventive mode operation would entail a heavy economic penalty. It is much more common in the western part or the United States than in the cast, but is increasina in use everywhere. Corrective action is less common than preventive operation because it is considered more risky to depend on action after the fault. An accumulation of different corrective actions for different continaencies is considered even more risky because malfunctions or these schemes could have consequences that are hard to predict, including the possibility or causina interruptions when no hazardous conditions exists. S. N~,d /or R,s,n,s for Em,rg,nclts In order for the system to be operated safely, it must have reserve c:ipacity both in the acneration and the transmission facilities. This principle :ipplies both in the operation and the plannina of the system. The absence of sufficient reserves exposes the system to service curtailments in excess or the levels considered reasonable, to major system disturbances or blackouts, or to unfair dependence on neighboring systems. Casazza, Schultz ct Associates, Inc. 11-14 ,.. 021
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In operatina the system, it is necessary to provide aeneration reserves capable or providina additional power if any 1eneratin1 unit, or an entire plant, were to be lost. Since the time required to start up a unit ranaes from minutes to many boun, depcndina on the nature or the unit, this reserve capacity must be available immediately or on very short notice, and is referred to as operating reserves. Some or the opcratina reserves must be actually connected to the system as spinnin1 reserves. Some systems will permit a portion or the reserve to be in the form or quick-start operatin1 reserves consistina or units capable or being started and connected in a matter of minutes. System operation also needs reserve capacity in the transmission system. These reserves arc represented by the difference between the capacity needed to satisfy current conditions, and the facilities needed to operate under the n-1 operation criterion. In the planning of the system, it is necessary to provide reserves not only for the requirements or actual operations, but also to allow for scheduled maintenance to be performed on the aeneration and transmission system components, and also to allow tor the possibility that actual loads may turn out to be greater than those forecasted. Such reserves are called installed reserves. Some, or all installed reserves are not operated when the combination or electric use levels, including system exports, and generation forced outages are low. C. Temporal and Economic Factors Affectina Constraints Transmission limitations have been shown to involve the interplay of the physical characteristics or the system and the actual flows. Both of these change with time and with economic conditions and economic conditions also change with time. As a result, the amount or power that can be safely transmitted between two areas keeps changin1. Casazza, Schultz & Associates, Inc. II-1.5
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I. Patt,rn of D,mand The customen' loads vary constantly. Much of the time variation can be ascribed to cycles or nature (time or day, season or the year) and or human activity (day or the week). Other chanaes are due to chanaes in economic activity which happen in irreaular cycl~ or to weather conditions. chanaes in fuel costs and electric rates and random events which are not cyclical at alL A strikina real-life example or power transfers chan1in1 with a temporal cycle can be seen in the transmission between the Pacific Northwest and California. The Northwest has a peak load in the winter, due to electric heating; California's peak load is in summer, with air conditionina an important component. The transmission system joinina them generally sends power north in the winter and south in the summer. (In addition, considerable transfen occur because of temporal variations in the availability of hydroelectric energy as discussed later.) As the loads change, the power aenerated in each area of a system also changes, but not necessarily in proportion. Instead, the aeneration at each plant changes accordina to its incremental cost or aeneration, in such a way as to minimize the total aeneration cost oC the utility. As the total system load increases, for example, the aeneration at a aiven plant may increase a lot, a little, or not at all. The transmission system which joins the different areas carries the net difference between the aeneration and the load of each area. Thus, the power transmitted between any area may inc;rease, decrease, change direction, or remain the same, as the loads chanae. Power transfers in some lines may actuatly be greater in medium or low load periods than at peak times. Figure II-5 illustrates such a case. At light loads, the net power transfer for economic dispatch is 200 MW Crom area B to area A. At a hiaher load level, area A generation has increased more than that or area B, and the flow between the areas has both reversed and decreased in amount. 2. w,ath,r The weather affects constraints on transfer capacity both indirectly, by arr ecting loads, and directly, by aCCecting the capacity of individual components. Casazza, Schultz & Associates, Inc. II-16
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AR.EAA AREAi FIGURE II-5 INCREMENTAL PBOQUCTJQN COSTS Area Area A Arc:i B Qeoeration 300 700 900 1000 1100 Generation 2$ 30 35 37 40 Qenensioo 20 25 40 so 60 L Liah t Load Period. System Incremental Cost 25 S/MWH AR.EA A toad 1000 Gen. 1100 100 AR.EA B I.ad 1000 Gen. 900 b. He:ivy Load Period. System Incremental Costs 40 $/MW_H Casazu, Schulcz & Associates, Inc. 11-17
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ne effect or weather on loads is complicated by differences in weather in different locations; this is another reason why economic power interchanges may increue or decrease u the weather changes. In the summer, power will Clow more heavily towards an area which is surrerin1 Crom a heat wave Crom neighboring areas with milder weather. In addition, weather conditions directly arrect the capability or individual components or the power system, and, as a result, that or the transmission system. Warm weather reduces the effective capacity or most thermal aeneration sources. ne eneray u well as the capacity of hydro raources depend on seasonal precipitation and evaporation patterns, and by competina uses for the water. The thermal capacity of transmission lines varies with the ambient temperature; when the weather is hot, it takes less current to heat conductors to a given maximum permissible temperature, so that many utilities use lower ratinp in summer than i'n winter. Extreme weather conditions may actually disable certain components. Lightning is the primary cause or transmission line failures, and extreme cold weather hu interrupted the flow or coal supplies for some 1eneratin1 stations, thus restricting their production and causina other stations to increase theirs. 3. Systm Confi,uralion The transmission system's transfer capability is arr ected by changes in the confiauration or the transmission and generation systems, which may be due to maintenance, to transmission and generation forced outages, or to the deliberate switchina or transmission system components. Every time that a component is added to or taken out or the system, r or whatever reason, the operator is dealing _with a new. system; the actual flows chanae, and so do the potential effects of any continaencies. A different continaency may become the limitina one, and the total transfer capability may chanae very substantially. 4. Production Costs Casa~a, Schultz & Associates, Inc. 11-18 I
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Variations in production costs. whether caused by changes in fuel cost or by any other causes that do not apply equally to all sources, result in decreases in the output of those aenerators whose costs increase more than the others', and subsequent increues in the output of the other aenerators. The basic economic nows in the transmission system chanae u a result. This in turn changes the constraints on the capacity of the transmission system to carry power for economic transactions and emeraencies. The chanaes in relative costs may have many causes: Fuel price fluctuation; Availability of compctina power sources from neiahborina electric systems; Variations in hydro conditions which change the amount of available hydro eneray; or Shortaaes of specific fuels due to various reasons. Before the 1973 oil supply cr_isi~ the effective costs of coal and oil were reasonably balanced. The relative production cost of steam units depended more on the efficiency of their desian (often a matter of aae) than on the fuel they burned. The mid-western reaion9 near coal mines tended to burn coal; the northeastern and Atlantic states burned more oiL Incremental fuel costs were reasonably balanced, and the economic power nows between the Midwest and the East were related as much to temporary situations such as unit outages and load variations as to basic cost differentials. There was some constant west-to-east Clow because some eastern utilities participated heavily in mine-mouth coal plants in western Pennsylvania. Beainnina about 1973, however, the cost of' .oil began to soar relative to that of coal. A permanent cost dif'ferential arose between the Midwest and the East; transmission between the two has ever since been Cully loaded almost all the time in order to carry power from the low-incremental-cost Midwest to the high incremental-cost East. S. Loop Flows When one utility, or area, sells power to another, this transaction is implemented by the seller increasina its generation and the buyer decreasing its generation by an equal amount. The ef'fect is that flows increase alona all the paths between Casazza, Schultz & Associates, Inc. 11
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the two parties, reaardless or ownership or the lines, and includina indirect paths throuah third parties. The distribution or the increase in flows depends on the impedance or the various paths (impedance is a characteristic or a transmission line, and depends on the line's voltaae, lenath, and desian details). A path with a low impedance will pick up a areater part or the total transfer than a path with a hiah impedance. Some pools, recoanizina that power nows are aoverned by physical laws, and with the assumption that all parties would share fairly in terms or contributions made and benefits received at different times. have instituted free-flowing ties amona themselves. They do not charae each other for the use or the transmission they own in intercha111in1 power amona themselves. However, in the absence of a specific rree-Clowina tie agreement, it is the practice in many reaions of the country that two utilities will not schedule the transfer or a block or power between them unless they establish, throuah ownership or le3sing or purchase or transmission service, a contract path of sufficient capacity le3ding from one to the other. While this concept at least ensures that the total schedu!ed transactions between two systems do not exceed the sum of the individual capacities or the lines linkina them, it docs not at all ensure that the total flow is within transmission limitations as they have been explained earlier in this section. The transmission limits between two areas are always less than the sums of the capacities of the individual lines linkina them, for three reasons: The r act that power flows according to Une impedances and not according to line capacities; The fact that some lines have hiaher capacities than others, but do not draw current in proportion: and The need to load lines at less than their emergency ratings to provide for increased flows due to possible continaencies. When two or more paths carry power flows different from the amounts 3ssigned to various contract paths, the difference is often referred to as toop flow, because the difference is in one direction on some paths and in the other direction on some Casazza, Schultz & Associates, Inc. II-20
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others. Loop now is the result or many different transactions going on at the same time. Since all control areu in the U.S. are connected directly or indirectly to many othen, the same physical laws will cause part or the transactions between two adjacent areas to Clow throuah the transmission systems or third, (and fourth, etc.) parties. These aenerally unwanted nows are also referred to u oop flows: or sometimes circulatina nows. or unscheduled nowL Fiaure 11-6 shows some control areas in WSCC, with their loads. aeneration. and interchange at one instant in time. The circulatina flows (CF) in each link arc the differences between the actual interchange (AI) and. the scheduled interchanae (SI) between the control areas involved. A line which carries circulating current due to other parties' transactions cannot be Cully used Cor the owners' transactions. Loop Clows are an important aspect of the operation or both the WSCC system to which SCE belongs, and the PJM Interconnection. Fiaure 11-7 illustrates loop nows in the Northeastern. V.S. when Ontario Hydro sells power to New York State. 5C)q( or such a transaction can flow through PJM lines. 011 the other band, a PJM west-to-cut transaction will, in part. now through the Ontario-New York paths, which tends to reduce the effect of the west-to-east loop now on the PJM lines. However, the two effect3 are rarely completely cancelling, and the net result is a decrease in the effective transmission capacity available for west-east transfer within PJM. which varies with the amounts of the transactions between all the parties involved. Fiaure 11 shows loop flows in the WSCC system. The transmission between the Pacific Northwest, the Mountain states, and Arizona and California has been described as a doughnut which carries coa~!1erable loop flows in addition to scheduled flows. These loop flows depend on the transactions between the various parties, and vary in amount and in direction; sometimes they go clockwise, and sometimes counterclockwise. At all times, they affect the a.mount of power that can be safely transmitted between two parties in the system. Casazza, Schultz & Associates, Inc. 11
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II II
PAGE 36
0 I: N = (II n ::r C: .. N ,_. > ... .. ft Ill c:, p -- t-., t-., PG&E SCE NORTHWEST TO DC HYDRO WESTERN TO CONTROL AREAS MONTANA I> 1eu IIJt ..--.-,-c, Al TO UTAH &.NEVADA TO NEVADA au/111 111/1 Al .. TO UTAII & COLORADO SDG& E TO FlGURE II 6 CONTROL AREA ILLUSTRATION NEW MEXICO
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FIGURE D-7 INTERCONNECTED SYSTEM RESPONSE FOR OH TO NYPP 1000 MW SCHEDULE (Aapol'IM In Megawatts) ICU'n4PN
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II Ill
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--C c..=-C-:s--------~ 3.! C :S --= u. 0 3 0 u. Casazza. Schultz & Associates. Inc. CD C 0
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6. Coruqwnc,s of T,mporal and Economic Factors All the temporal and economic factors that have been discussed have one thing in common: they cause the effective capability or the transmission system to carry power between two areas to vary. Some of the factors are reasonably predictable, and some are not. Neither the contract path concept, nor any other method, can auarantee that a transaction that can be made reliably on one day (or at one hour) can be reliably carried out at another time. The transmission system needs to be constantly supervised and controlled for reliable service to all users. When an unsafe situation happens, the operator of the transmission system must have the right and the technical means controls and communications to correct it; the correction most often consists of increasing the production of some generators and reducing that of others. Utilities, working together, have developed rules for indemnifying a party who may bear the brunt of adjustina power Clows for the sake of reliable service for all parties using the transmission system. The essential point is this: when the transmission syst~m is directly or potentially overloaded, the system operator gives instructions for the relief of the system and these are followed at the expense of economics. Economic adjustments are made afterwards. Until recently, non-utility aeneration (NUG) has been a relatively small portion of the total aeneration supply. If a NUG was not under control of the system operator to the extent that a similar utility-owned unit would be, it did not matter much because the effect was small. As the proportion of NUGs becomes substantial, however, the need for their control and cooperative operation as participants in the overall -electric system becomes critical. SCE, which contains a high and growing proportion of NUG resources, reports a number or problems in this area and expects more in the future. The integration of the NUGs into the system, taking their full share of its obligations, will be indispensable if the reliability and economy or the entire system is to be preserved. Casazza, Schultz & Associates, Inc. 11-25
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III. BASIS AND APPROACH FOR CASE STUDIES A. The Five Scenarios The eCCects on utility plannin1 and operation of Cive scenarios or regulatory chan1e were studied. The five scenarios are u follows: scenario 1 Status Quo Plus Romo, Prud;ncy Reviews Scenario 1 continues the existing regulatory scheme and electric power industry structure and reaffirms the reaulatoryutility bargain with minor modifications of reaulatory rules and procedures to improve the ability of utilities to attract capital for construction of new facilities and to assure a reasonable return to investors (e.g.. rolling prudency reviews). Modifications of PURPA rules to correct perceived imbalances in avoided cost pricin1 rules Cor QF power would also be allowed. Many utilities will continue to rely on QFs and IPPs r or a portion of new power needs. Transmi~ion access would remain on a voluntary basis to be negotiated between the participants. FERC would retain its authority over transmission rates and wholesale power sales. Scenario 2 Expandina Transmission Ac;c;ess in the Existina Institutional Structure In this scenario, the number of bulk power sellers and the number of potential bulk power buyers is increased by 1) removing some of the size, technology, fuel, and ownership limitations for qualifyina facilities through legislative modifications to PURPA and the Public Utility Holdina Company Act; and 2) changing the mandatory transmission access provisions or the Federal Power Act to a broader public interest standard to make utilities and larae retail customers eligible to apply for mandatory wheeling orders. Policies intended to encourage bulk power sales and wheeling will be continued and expanded. The IPPs and QFs would be assured a market under the States' implementation of PURPA. Casazza, S~hultz & Associates, Inc. 111
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Scenario 3 All Source Competitive Biddina for New Generation with Mandatory WbeeU01 Scenario 3 establishes an institutional structure to allow all source competition Cor new bulk power supplies with market based pricina. (The scenario is loosely bued on the Keystone and Hesse proposals.) Transmission access is included as a prerequisite Cor participation in the competitive system. Mandatory transmission access under the public interest standard or Scenario 2 is also available Cor bulk power transactions by utilities. Provision or wheeling services to retail customers remains voluntary. Utilities are able to participate in bidding for new capacity within their own service territories and those or other utilities with appropriate saCeguards established by the states to limit problems of self-dealing, conflict of interest, etc. Scenario 3 creates a two-tiered bulk power supply system: new power supplies under a minimally regulated, workably-competitive market; and existing generation remainina under current state-federal scheme oC regulated entry and pricing. The electric power supply industry will gradually evolve to an all competitive generating sector u cxistina plants are replaced. Transmission and distribution services remain regulated as at present. scenario 4 Generation se1re1ate4 from Transmission and Distribution services Scenario 4 would create a competitive system for electric power supplies. Existing and new sources would compete to sell power to regulated transmission and/or distribution companies. Integrated utilities would be required to segregate generation activities both institutionally and operationally from transmission and distribution through creation of separate subsidiaries or corporate divestitures. Transmission and distribution activities would be heavily regulated. Modifications to PURPA QF requirements and PUHCA restrictions allow broad participation in generation markets. Local distribution companies would be primarily responsible for securing adequate power supplies from competing supplies. The transmission company would provide wheeling services for utilities under re1ulated rate schedules and could also act as a power broker linking local distribution Casazza, Schultz & Associates, Inc. III-2
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companies with power suppliers. Distribution companies could obtain mandatory transmission orden Crom FERC on a public interest standard. There would be no mandatory wheelina ror retail custome~ but it is expected that generators and transmission companies would enaaae in direct sales to large retail customers, with local distribution companies providina distribution wheeling on a voluntary basis and receivina bypass or standby payments. Scenario Common Caaier Inosmi33ion Services in a Disaggregated, MarketOriented Electric Power Industry The electric power industry is divided into institutionally separate 1eneration, transmission, and retail distribution segments. The major difference between this scenario and scenario 4 is that separate transmission companies would explicitly be required to provide transmission services as a common carrier i.e., non discriminatory service based on approved wheelin1 tariffs to all parties requesting service including large customers. The transmission company would have an obligation to provide adequate transmission capacity. Distribution and transmission services would remain reaulated, but in the electric aeneration seament, market entry and bulk power pricina would primarily be left to market forces. Federal and state policies might encourage greater aggregation in transmission services to create coordinated large regional transmission systems; either through mergers and acquisitions or through operational agreements among neighboring systems. The five scenarios are summarized in Table 111-1. The procedural changes and system technical cbanaes, includina reinforcements, which would be required with each scenario, were determined. As discussed earlier, the overall objective was to maintain the reliability presently being achieved in its planning and operation and the savings presently being achieved in the operation of the system through coordination procedures within the system and with other utilities. This essentially meant estimating what technical system and procedural changes would be required to maintain the existing reliability and coordination benefits to consumers as they Casazza, Schultz & Associates, Inc. 111-3 ........
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... E .. f ::r C -... N pP > g n ; ... n j' ::a IIIIUSIII IIIUCIUIE !) aIAIClll/lllllH -I .,,111 (0tller than fr r91Ulatad utllltl> IIAIIINIIIICII ACCSS Clitleellne) JAllE 111-1 CMtvlEV Of PWIOI HI DH(QUJlflll MID )!AltSNISSICII ACCESS KflfAfllQ J ltrenetlMn Ille lqulatory Utility lar .. ln with ol l Ina Prudency levl ..... Gf end IPP can Hll only 10 utility. Vartlcelly lntqratad IOU., Nunlclpal1, Cooperatlva, federal Syt-Conti,.. .. prn1nt leneratlon1 1 Utllltla1 1 Gfa Ca la ,._,A) 1 IPP Cat utlllty option, or u per atate c-1 .. 1on Hll lne to utllltl> All aal .. are to utllltla1. Salf-.... ratlon 11111 poaalbla. Prnent cuet.ara fr local utility IMII the local utility..,. .. otherwlH. Utllltla1 are only cu11 .. r1 of nonutll lty eanentlon. ICJIIAIIO Z Eapand lran111l11IC111 ~NI to Qfl end IPPa to Sall to Utllltlaa and 10 certain Lar .. latall 1:u11 .. r1 -alllYI urvqulatad utll hy Ml>aldlarld General Iona 1 utllltl 1 Qf1 CPUIPA 111,t f..,. raatrlctlone) by IPP IN'qulatad utll Uy ..-ldlarla1/afflllata1 Utllltl and lar .. retail cuet .. r1 Y wly fw aandatory .... line order under a "broader .-.11c lntara1t atandard. E11antlally vol!Mltary bv Utllltla and lar .. retail a,tuel .. raaaant. cuet.ara can petition fllC nae can order Mhen requeatad for _.tory Mhael Ina l.ftder ,uapA rulH. ordera for e:rlpctl uo,r1tor1 ad on a new p.J>llc lntareat 1tandard. KENMIQ J SCCNMIP t CCllllflltltlw llddlna laqi,lrad AllICU'ca eo.w,.t111 .. fw for All ..... Utility All lulk Power 11.fpll, Ganer1tlon. llo tran1111Hlon with Ganeratl Sqr ... tad ac:ca11 to cuu .. ra. fr lranulHlon and Dl1trlbutlon Sarvlca1 -11 Z RlJa Generation 1qra .. tad. utility .Jidcilarla1 cC111p1te 1-,ulacad traN11l11I In other utllltlaa blddlna. end/or dlatrlllutlcin cmpenle1. Generation by1 Generation by1 utllltl Utllltlea lfe ... U Z Qf1 IPPI ...... z IPP CClllpltltlva blddlna r..,lrad All cmpatlna fw .. 1 .. (lncludlne nonprlca factor 10 11D utll ltl... an, In evaluation). ...-rator can Milt retail Ut 111 Cy CIR be a CUlt.ar but M Mndatory CCllllflltltor In C111n vet. .....line. Dlatrlbutlon Ut II Icy CIR fora CClllplRI .. plan for W1rqulatad IUllldlarln requlr-.11. to eanerata In other ,,.,..IHlon CClllplnl .. my ay1t1N. and broker power. -aa Z, but aa:ludlna lar,. retail cuat.ar1. IID Utll ltle1. Lar,. retail cuet .. r1. ICJIYIQ S Caaan Carrier ,,.,..IHlon larvlc: In 011111, ... ,ad NarkatOrlentad Electric Power IIIIMltry AnVaM Cen Generate MVGM Can lur fr Ant 11.fpllar llneretlon ..., ... tad. lr.,...la1lon ratulatad u c:-cerrlara. lqulatad dlatrlbutlon C:Olllpalll-1 .. u 4. Ant tanerator an Hll te .,,,, eiu,.r. Alff c:uetcaar CIR fr .,.,, ..,_rat or. lr1n1al11lon CC1111p8RV .,., provide tr..,..l11lon. -.. 2. ,,.,..IHlon dlvl1lon1 or Separate tr.,...laalon Al IOI llandatory wheal 1111 anler ...-ic lnteralt aundllrd for bulk power t,.,.acclane 1 utllltlea. Utllltln .,.t 1lve tran111laalon ace If they want to participate In the eaneratlon blddlnt. ..._ldlarlaa provide cmpanlaa -t provide wheellna for ucllltln under 1arvlc to ll partlaa. reeulatad rate achacl,le1. "'"' lne cuet .. ra could lo lllfldatory Mheellne for contract for different retail cua1.ar1 CvollMltary level of 1arvlce. ok).
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1 .... l .. I ~ti i !.-1 le':: u .1 ----:: t &I &I l .. i u -1:1:1. i i.:S--~-,; !I.: ::.1. 1..: :1s: :n: .... :. c! o ........ u & -:: u ll I i 1 ,.; .. ,= Ji i!1 I 0 ..... i~.t -1;1 ll.!.! i~11 -..... 1 i a1 u-= .!J .. I l~ .. tJ=-.c: l"Ei lt-.. t= .... .!. W IIIUWIII .... -,, .. s.:UI I I I i i i -I i .. 1110 ii II Casazza, Schultz cl Associates, Inc. 111-S N : I I 1 .: J. u-,. -1--1,:;:a. 7-":.1?-_, ...... ,.. .,_ ........ -.. = & =-.ou.0..,,t ... ,_. l=-Ji.! u -. =;i~&~ ,.. .. a ,.. c -,. Ii.: c: _, ,__ OIO -.... --.. .. ... .. C: .. ---!a !!1 C.., ._ == :s.1, ...... --c .. 5liil! .! I I I I .... 1:s I.! il"1 i-u. .. .tll s I 1, 11 ....... c;: .,,._ .. --1 --&J I ls .. Jill' .. .. ,:1 l li:I ...... !. .. .. .. ... --JI --~ .. :~1oa I ..... u ..... 2ii1 ... u u
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j ] -l 1 ,,._ i ii. l! I .. = .. !; 4 1 ... i -& '- !i ... i :: 1; 11 .. I J Casazza, Schultz & Associates, Inc. III-6
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presently exist. with the various alternative dereaulation and transmission access scenarios. B. Facton Investiaated and Buis for Sclectin1 Case Studies I. K~y Factors and Qulstio,u In perCormin1 the cue studies, the Colloin1 information was obtained and reviewed: The present capacity or the transmission syste~ both in the internal network areas and in the interconnection and interties to other systems in other reaions; The critically loaded facilities and the critical continaencies determinina the limitations in transfer capability; The system conditions causin1 maximum loadina; Ways that the present transmission capability can be increased; Existina qu1liCyin1 facilities or other non-utility aenerators; Potential future non-utility 1eneraton; The municipals. REAs. etc. that presently obtain power; and Also, any utilities Cor whom wbeelina service is presently provided. The analyses obtained answers to a number of key questions relating to operations of the systems. a. What information will be required concernina aeneration schedules of non utility aeneraton and consumption of loads supplied by others? For what seasons, times of day, etc., will data be required? b. How far in advance will this information be needed? c. IC additional tramCen are needed by non-utility aenerators or larae customers. how much advance notice would be necessary to provide for such chanaes in operations? d. What clianaes in procedures are needed for handlina the additional information requirements? Casazza, Schultz A Associates, Inc. 111-7
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,. e. Who should be respomible ror makin1 the necessary opcratin1 decisions ror coordinated operation or the overall system with the various scenarios? C. How should the output or the varioas aoe-utility units be scheduled and CODtrolled? 1-Is iacnmeatal cost dispatch Ceasible at present with existin1 NUGs? IL Will the system be able to coatiaae to perform incremental cost dispatch? L Who lllould determine the availability or traasmiaioa capacity? j. If there is a shorta1e or traaaniaion capacity amoa1 the various potential ascn. who should determine the priorities for use? k. At what load levels are the areatest trammiaion restrictions anticipated? L How will the ability to control voltaic and provide necessary reactive support be aCCected? How will this problem be bandied? m. How will the provision or spianin1 reserve and reaulatina capacity be chan1ed with the advent or non-utility aeneraton under the various sceurios? L How will the ability to maiataia rrequency control and tie line schedules be arr ected? o. What chan1es in commuaicatiom will be necessary with the various scenarios? p. What special control technolon will be required with increased transmission accca aader the variou sccurios? Will contractual arnnaements alone be sarricieat to cover operatiom. or will the ability to physically control the use or transmiaion by the system operator will be necessary? What types or physical controls will be needed. and what should be controlled? q. How will 1caerator maintenance schedules be established and approved? r. Will QFs and IPPs be eliaible to participate in pool activities? Should they be? L What potential new technolo1ia could be valuable in helpina to meet the new opcrat1n1 requirements with the various scenarios? L What improvements are needed in the various types or control? With reaard to the errect or the potential scenarios and the plannina of the future development of the electric system. the followin1 key questions were asked: Casana. Schultz A Aaociata. Inc. 111
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L What new data and procedures will be necessary in order to make load projections for the future? b. How will the possibilities or losin1 loads and 1ainin1 loads through the competitive process made possible by transmission access be evaluated and treated? c. How will the potential information needed for makin1 your plannina studies be obtained, concernina new 1eneratin1 1ources both within and outside the utilities' systems includin1 QFs and IPPs? What sort or data will be needed and how can it be obtained? d. In plannina transmission, would utilities provide for potential mandatory (or non-mandatory) wheelina requirements? How would they include this in their plannina? e. What chanaes in sites for future aeneration may result? r. Would the systems' load projections be as certain as they were before? Would increased reserves be required to cover these uncertainties? a. Would the service dates for future aenerating capacity additions be as certain as with present conditions? Would potential changes in construction schedules r or QFs and IPPs be areater or lesser than the potential changes in the schedules r or the utilities' own aeneration? la. Would the reliability or the new units be as 1ood or bad as the present utility units, and would arcater or lesser reserve capacity be required? i. How would. utility commi:sioa involvement affect planning decisions? j. Would lead times be increased or decreased? How would utilities' plans be affected because of the such changes? k. Would reserve requirements be increased with the various scenarios and why? 1. Should plannina criteria be revised and if so, why a-nd in what direction? m. In plannina transmission, how would the additional transmission that may be required for future wheelia1, either mandatory or voluntary, be determined and provided. n. What chanaes would be required in the reserves provided in the transmission systems? o. What chan1es are foreseen in Cuture additions to the transmission system? p. What chanaes in plannin1 procedures, pool activities, or reliability council activities would be required? Casazza, Schultz cl Associates, Inc. 111-9
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The potential for existina and/or new technologies to solve some of the technical problems raised by the new scenarios was carefully checked using the best of technologies aiven in Table II1. Specific questions addressed were: L What new technoloaies arc available to help maintain existing system reliability and existina inter-company coordination benefits with the addition of larae amounts or QFs and IPPs and the ability or large customers to switch supplicn? b. Arc any new modeling approaches needed and possible? c. Arc any new types or system racilitics possible? d. If technical changes must be made to the transmission system, including possibly adding additional circuits, how should the investments required in these facilities be allocated among the various users? 2. Crittria Usd in Stltctin1 Systtms to b~ Studitd A number of criteria for selecting the systems to be studied were reviewed and discussed. The criteria selected arc shown in Table 111-3. The transmission conditions in the various systems in the U.S. were also reviewed and summarized, as shown in Appendix A. Based on this information, the systems selected were the Southern California Edison system (SCE) and the Pennsylvania-New Jersey-Maryland Interconnection system (P JM). Casazza, Schultz & Associates, Inc. 111
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TABLE 111-2 POTENTIALLY APPLICABLE MEANS OF OVERCOMING SYSTEM LIMITATIONS 1. Overcomina Line Limitations L Volta1e upratin1 b. Current upratin1 Increase temperature rise Saa assessment and monitoring Dynamic conductor ratinp Resagging Restringina (including bundling) c. New towen on existing rights-or-way Underbuild or overbuild Conversion to multiple-circuit towers Hiaher phase order 2. Overcomina System-Related Limitations a. Load division among circuits Phase anale reaulators Series reactance or capaciton System reconriauration HVDC Redispatch or generation b. Voltage profile limitations Reactive power management Shunt capacitors Series capacitors Static VAR compcnsators, synchronous condensors Transformer tap changina under load (L TC) Line sectionalizing 3. Overcoming Transient and Dynamic Stability Limitations Reducing clearing time Series capacitors Rapid adjustment or network impedance Generator tripping and Cut runback Fast valving Braking resistors and load switching High-speed reclosing Advanced excitation systems and stabilizers Transient excitation boost Fast acting phase angle regulators Generator reactors SVCs and synchronous condensors Adding switching stations (sectionalizing) Special switching schemes HVDC Casazza. Schultz & Associates. Inc. 111-11 ,.. .....
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TABLE 111 (Continued) 4. Minimizing Power Plant Response Limitations Speed up response Increase maximum output S. Improvements in System Control On-line security analysis Additional monitoring and control Casazza, Schultz & Associates. Inc. 111-12
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TABLE 111 Criteria for se1ectin1 Two svuem3 to be Studied I. The selected candidates should be in separate regions of the country in order to acquire a diverse view of the problems. 2. The two candidates should be able to supply the data and specific information necessary for the analysis. 3. The candidates must be willina to participate and cooperative in supplying input. 4. One candidate should be a non-integrated system and one should be a member of a tight coordinating council or power pool. S. At least one of the candidates should have prior experience with cogenerators and qualified facilities. This experience should be as extensive as possible. Casazza, Schultz ct Associates, Inc. 111-13
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3. Procedures Used in Meetinas with Utilities In making the case studies, meetings were held with key representatives of the utilities. Discussions at these meetinss were based on an open-minded and constructive approach to makin1 the various dc:reaulation scenarios workable while maintaining the present standards or reliability and the expected level or coordination benefits. The procedural changes to achieve these aoals arc summarized in the subsequent sections or this report. During the discussions, every attempt was made to review the reasons behind the views and conclusions or the representatives or the systems involved in the case studies. While this report is the responsibility or its authors, the specific material included and many of the conclusions reached were, in large measure, those of the members of the utility systems that were analyzed. C. The SCE System and Transmission Constraints The SCE system supplies an area covering about S0,000 square miles with a population or about 10,000,000 (Sec Fisure 111-1). In 1987, it had a peak load of 14,775 MW and supplied 65 million MWhrs of energy to its customers. SCE supplies about 3% or the electric eneray consumed in the U.S. Figure 111-1 also shows the SCE transmission network and the key transmission lines involved in the import of power into and the export of power from the SCE control area. The 1986 limitations on imports to SCE are shown on the diagram. Casazza, Schultz A Associates, Inc. III-14
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d Casazza S chultz & A ssoc1a tes, Inc. 111-15
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It should be pointed out that these are non-simultaneous limits, and that imports across one limiting corridor arrect the limits across other limiting corridors. The Southern California Edison Company (SCE) is a member or the Western Systems Coordinatina Council (WSCC). Hydroelectric generation Crom the Pacific Northwest plays an important role in the energy supply picture in the Pacific Southwest. The primary reliability-related concern in the West is a disruption nr the Pacific North-South Intertie. Loss or both SOO-kV alternatina current (AC) lines or of both poles of the high-voltage direct-current (HVDC) line will result in serious bulk power supply problems within WSCC. These contingencies will adversely af r ect the SCE service area by requiring the use or higher-cost energy, or under severe conditions, temporary load curtailments. The NERC 1986 Reliability Review shows that over 31% of the planned WSCC capacity additions between 1986 and 1995 will _be non-utility generators.1 The size and location of these non-utility generators will be closely watched by the utilities within WSCC to ensure that the transmission system is capable of handling this diverse capacity source. The California-Southern Nevada area is predicting the highest growth in non-utility generation. A primary concern in this area is that, in most cases, the utility has no control over non-utility aeneration operations. The utilities are required to absorb the energy into their system whenever it is delivered by the non-utility generators. This requirement further complicates the overall operation and planning or the bulk power system in the WSCC. Over the 1987-1996 time frame, the WSCC has several transmission projects. planned, or in progress, to alleviate its current transmission constraints. These arc discussed in Section IV or this report. D. Description of the PJM System and Transmission Constraints The Pennsylvania-New Jersey-Maryland Interconnection (PJM) is a power pool consisting or eight utilities serving all or most or New Jersey, Pennsylvania, Maryland, Delaware, and the District of Columbia. All 1eneration is centrally controlled for 1. NERC, 1986 Reliability Review; Table 7, Pg. IS. Casazza, Schultz & Associates, Inc. 111-16
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economy and reliability. In 1986, PJM members served over 8,300,000 customers and a population or 21 million people over an area of 48,700 square miles, and sold 186 million MWhrs or electricity. Tlie 1987 summer peak load was 40,526 MW and the installed capability was 49,489 MW. A map or the PJM system and its major transmission facilities is shown in Fi1ure 111-2. The members or PJM own 1eneration resources usin1 nuclear, coal, oil, and ps fuel as well as other ener1y sources including a moderate amount or hydro power. The resources in the eastern part or the area contain a larger amount of oil and gas fueled units. Also, all members own shares or coal-fired units located in the western part. The members of PJM are connected with each other and with outside pools by a transmission system composed of lines at 500 kV, 230 kV, and various lower voltages. There are ties at 500 kV, 345 kV, and lower voltages with all the neighboring pools: the New York State Power Pool, the East Central Area Reliability Coordination Agreement (ECAR), and the Virginia-Carolina Pool (V ACAR), a part or the Southeastern Electric Reliability Council (SERC). PJM operates on a poolwide central economic dispatch basis to meet customer needs Crom the most economic generation available recognizing established reliability criteria. With this arrangement 7 the lowest-operating-cost generators available anywhere in the power pool produce power without regard to individual company requirements or individual company ownership of generating facilities. In any given hour, some utiHties will generate less than the requirements of their own customi:rs, and some generate more. Therefore7 in any hour, some utilities automatically buy power from member utilities and others sell power to member utilities. Similarly, the member companies or PJM. when economical, purchase power from or sell power to systems outside PJM. Thus, the transmission system operates to move power among utilities such that the most economic combination of generating units is operating at any given time (consistent with reHability requirements) and the minimum fuel or operating cost is incurred by the utilities and their customers in aggregate. The savings that result from such pool-wide optimization of generator loading -that is, the difference between what it would have cost each utility to generate all of its own customers' power requirements and the actual pool Casazza, Schultz ct Associatcs 7 Inc. 111-17
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. I J I I I ,I I 11" I II '1' I I 111 I I" !111 I II z 0 t; z z 8 = z -I < ,Z < > ..:I > en z z w i:i..
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costs under the optimum arrangement described previously are split equally between buyina and sellina utilities and with the New York Power Pool and other pools. These savinp are reflected in each of the utilities' customer rates. Since the poolwide central economic dispatch results in the lowest possible total energy cost to the memben or the pool, this metbod maximizes the savinas achievable in the market; the transfer or more or less power amona the members would be less than optimal and would result in increased overall fuel costs for the power pool. Power transactions between individual PJM members and utilities which arc not members or PJM in many cases. utilities several states removed from PJM occur in a hi&hly competitive markcL System operation is continuously monitored to maintain reliability while opcratina to achieve economic efficiency. The objective of PJM is to operate in such a manner as to achieve the lowest possible costs whil~ maintaining the highest practical degree of service reliability to the customer loads of the member systems. To meet this objective, PJM operates the system on a sinale-contingcncy basis. which was described in Section n. Actual power nows on all major facilities arc continuously monitored by the PJM operations computer at the PJM Interconnection Office. The loss of each major facility is periodically simulated by the computer and the redistribution or power flow on each of the major facilities is calculated. Impendin1 overloaded facilities are identified and appropriate adjustments arc made to internal 1encr:ition and to imports from outside PJM to prevent an overload from occurring. This philosophy of operation is consistent with the philosophy of planning the bulk power system. The PJM operations computer constantly interchanges information with the individual members' operations computers. This includes the data needed for economic dispatch, monitorina the transmission system, monitoring operating reserves, scheduling maintenance, and other functions. The economic dispatch of the PJM generation, in addition to purchases or power by the members from pools to the west. result in heavy flows of power from the west to the cast which arc or near the capability of the transmission system. One transmission-related concern of PJM. both reaardina operation and planning, is the ref ore Casazza, Schultz ct Associates, Inc. 111-19
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to maximize the amoant or economic power, within reliability constnints. that can be transmitted Crom the western part or PJM and Crom non-PJM utilities west of the pool to the eastern load centers. Daria1 1917, the PJM system wu loaded to the limit or its capability to transfer eneray wat to cut acroa PJM 96.ltt or the time. The limitin1 nows are the result or: economic purchases Crom utilitia west or PJM; internal PJM economy transactions; unscheduled Clows tbrou1h the PJM system resultina Crom transactions by other pools. An example of this is circulatin1 power Clows which result Crom the transfer or eneray Crom Ontario to New York State. However, analyses conducted in 1914 and 1915 by ECARMAAC for DOE showed that the existin1 transmission system provided an estimated 90% or the economic benefits compared to what could be realized if the ed1tin1 transfer capability were doubled. Casazza, Schultz A Auoclata. Inc. 111-20
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IV. SOUTHERN CALIFORNIA EDISON CASE STUDY A. Means of Incrcasina Transmission Capability The Pacific Northwest and the Arizona-New Mexico region are the Southern California Edison (SCE) Company's major sources of economical power imports. SCEs efforts to increase its import capacity mostly concern the paths from these two areas. They aenerally involve cooperative studies and actions by various members of the Western Systems Coordinating Council (WSCC). which includes all the major utilities in the western states. Recent steps to increase the total intertie capability have included: Upgrading the transfer capability of the Northwest to California 500 kV AC Pacific lntertie from 2,800 MW to 3,200 MW in 1987. Increasing the Arizona-California transfer capability to S,S40-5,100 MW from its current 4,900 MW in 1987. Completion of the 1,920 MW lntermountain Power Project in Utah and the associated ,500 kV DC line to California in 1987. Steps beina planned for the future include: Completion of the DC Terminal Expansion Project in 1989 which will upgrade the Celilo-Sylmar kV DC line terminal from 2,000 MW to 3,100 MW. Completion of the third Northwest to California 500 kV AC Pacific Intertie in 1991, which will increase the Northwest to California AC transfer capability from 3,200 MW to 4,800 MW. The addition of phase shifting transformers in southwestern Colorado in 1988 to partially control the loop flow problem the WSCC has been experiencina. Addition of a second Devers-Palo Verde S00-kV transmission line which will increase the Arizona-California transfer capability by 1,200 MW. Table IV-I presents data showina the larae costs of providing these increases in transmission capacity. Obviously, the systems who have made these investments are reluctant to sec these facilities used by others without appropriate compensation. Casazza, Schultz & Associates, Inc. IV-1
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In the past, SCE and the other WSCC systems have utilized almost all or the methods outlined in Table III-2 to increase transmission capability or ;::idividual circuits, overcome system related limitations, and reduce transient and dynamic stability limitations. Fast valvina, variable series capacitors, braking resistors, load switching, and dynamic system stabilizers on AC systems and HVDC systems have all been pioneered in the U.S. by WSCC systems and have involved SCE. Operation using corrective technology to limit overloads when abnormal contingencies occur have been frequently used by SCE. Appendices B, C, D, E, and F provide five specific examples or methods used to increase transmission capability. New technologies being considered for future application include controlling the loading or AC lines during normal and emergency conditions by using more phase shifting transformers and solid state phase shifters; rapid adjustment or network impedance; use or static var compensators (SVC); and the use or NGH devices to permit increasing series compensation without causing subsynchronous resonance. B. Problems with Transmission Access and Wheeling SCE presented a number or specific illustrations showing the effect of additional transmission access and wheeling of power by non-utility generators and by other utilities. A large industrial cogcncrator is located near a SCE hydro station, both or them connected to the SCE system through two transmission lines. The cogcnerator takes his unit oCC-line, at a time when SCE takes one or the lines out or service for maintenance. The cogenerator comes back on line without warning. The remaining line is overloaded, and SCE must curtail its economic hydro generation to eliminate the overload, increasing its costs. In planning generation resources, SCE has had many cogenerators coming on the system with insufficient warning, resulting in excess resources and extra costs to consumers. SCE is concerned that cogenerators could similarly shut down without notice, resulting in capacity shortages. This Casazza, Schultz & Associates, Inc. IV-2
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TABLE IV-I SUMMARY OF COSTS AND BENEFITS TECHNICAL MEANS USED BY SCE FOR JNCJlEASJNQ TRANSMISSION CAPABILITY INCREASE IN COSTS TRANSFER LIMIT Increase AZ-CA $232,000,000 1200 MW transfer capability DC Terminal Expansion $163,000,000 ll00MW Project Third NW-CA S00-kV SS34,000,000 1600 MW Pacific lntertie Phase shifting $45,000,000 200 MW* transformers in Colorado COST/MW of INCREASE S 193,000 /MW S 148,000 /MW $334,000 /MW S225,000 /MW Phase shifters will reduce transfer capability but will also block loop flow. The net result is an increase in scheduling capability. Casazza, Schultz & Associates, Inc. IV-3
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could have any adverse effect on their ability to meet future consumer needs. There are now situations in which, as a result of loop flows on the WSCC syste~ SCE bas to curtail its participation in the Four Corners plant in order to prevent overloading a transformer there. With more participants and more deliveries made through the WSCC, these situations would become more frequent and more severe, again increasing costs to consumers. A customer connected to the distribution system generates DC photovoltaic power which is converted to AC through an inverter. Inverters can reduce the line voltage, and generate harmonics (alter the AC wave shape), which can cause TV and radio interference and overheat appliance motors in other customers' houses, and may also cause misoperation of SCE's protective and control devices, reducing reliability and increasing costs. A cogenerator in an industrial park serves most of the other customers in the park, while the others receive service from SCE. All share a distribution system in the park. SCE has sized its transformers and distribution circuit to the park to serve the SCE customers, not the whole park. If the cogenerator's unit fails, the entire load will be drawn from SCE's substation, resulting in an overload which will trip the line, cutting off service to the SCE customers and the cogenerator's customers as well. A large induction generator (typical of NUG equipment) is connected to a 33 kV distribution line. IC this line should be disconnected from the system, overvoltages ashigh as SOO volts could occur on the 120 volt outlets of the customers left on the line. This would damage apparatus and appliances and could endanger the safety of customers. Wind generators also use induction generators, and involve risks similar to those mentioned above. In addition, the output can change rapidly from nothing to large amounts. On one windless day, SCE took one of two lines out of service for maintenance. These lines served, among others, an industrial customer with wind generation. Later that morning, the Casazza, Schultz & Associates, Inc. IV-4
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wind increased and the remaining line became overloaded. This resulted in an interruption of service to an SCE industrial customer, causing economic losses. Many or these problems are not impossible to solve technically. However, their solution is often difficult and will impose operating burdens and increase costs to SCE and the consumers it serves. It will require the active and knowledgeable cooperation or the operators of non-utility generators, as well as, in many cases, special controls. communications equipment, and switchgear to prevent malfunctions, overloads, and accidents. The availability or such skilled personnel is extremely doubtful if a large number or NUGs develop in the future. Contracts with non-utility generators should provide for the necessary equipment to be installed so that SCE will have direct control of the NUG generator units if a large amount or such capacity is added to the system. Re1ulatory provisions did not permit SCE to require the NU9s in these cases to provide the needed controls and operating. procedures to avoid these problems before they occurred. C. Implementation of Deregulation Scenarios Each of the five contemplated deregulation scenarios requires certain changes in SCE and WSCC procedures. and in the SCE system, so that it. may be implemented in accordance with the ground rules assumed for these studies, which are: 1. no decline in reliability of service to the ultimate customer; 2. keeping all the benefits which are presently derived from interutility coordination and interchan1e or economy power; while 3. providing Cor the changes in the overall system dispatch and in the type, size, and location of generators from the way they would be under the present regulatory rules (If there were not changes in these, then the changed regulatory scenario would not change the overall operating and production economy). In this section, the changes required to implement each scenario are presented as they were developed by SCE in discussions with the investigators. They are divided into regulatory and legislative changes, procedural changes affecting either the operation Casazza, Schultz & Associates, Inc. JV-S
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or the planning or the system, and technical changes involving changes in physical equipment requirements. In examining the various scenarios, it was pointed out that only those changes in procedures that result in a change in the physical generation pattern how much power is produced where can possibly affect the overall economic efficiency or the system u a whole. Any chan1e that docs not alter the physical generation pattern does not change the amount or fuel used, the loadings on transmission lines, the losses, or anything else or a physical nature; any changes in payments, costs, etc., that would result would therefore only represent a redistribution or the previous costs and benefits; such a redistribution may be considered good, bad, or indifferent, dcpendina on one's point or view. They will have no immediate effect on overall economic efficiency. This is not to say that there are no other effects from such transactions. They may indeed have desirable or undesirable long-run socio-economic results and they may atfect the incentives various future suppliers receive. scenario 1 -Status Quo Plus Rollin1 Prudency Reviews In tirief (a more detailed description is shown in Section III), this scenario consists or maintainina the present situation, except that rolling prudency reviews arc instituted. I. Regulatory and LegislatiYt Changes No basic changes would be contemplated in present regulatory procedures including PURPA or its implementation. Some modifications or present PURPA procedures would be required to eliminate unrealistic evaluations of avoided costs which represent subsidies at the expense of the ratepayers. The cstabHshment of rolling prudcncy reviews may require legislative changes, however, to provide more frequent reviews and approvals of project progress by the regulatory commission. This will help to ensure that a decision of a present commission (particularly the inclusion in the rate base of expenditures which had been approved under the rolling prudency review process) will be binding on future commissions. Casazza, Schultz & Associates, Inc. IV-6
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2. Proc,dural Changes O~raling Under this scenario. no system operatina chanaes rrom present practices are contemplated. 3. Proc,dural Changes Planning The institution or rollina prudency reviews would require periodic reviews or the utility's plans. its latest revised requirements, and the status or its major projects with the reaulatory commission. Except for this addition. SCE's planning procedures would remain substantially as they are at present. 4. Syst,m Chang,s No substantial system changes are seen to be needed under this scenario. Scenario 2 -Expandin1 Transmission Access in the Existin1 Institutional Structure In this scenario, transmission access is expanded to QFs and IPPs to sell to utilities and to certain larae retail customers. so that some customer shopping is possible. IPPs and QFs are assured a market under the states' implementation or PURPA. l. Regulalory and L1gislative Chang1s In order to implement this scenario effectively, SCE requires flexibility in establishina its rates so that it may compete ror the load of large customers who are contemplating obtaining their electricity from other suppliers. Without such flexibility. many customers could be lost to NUGs, with a consequent increase in cost to the remainina SCE customers. The requirements for implementing the sc,nario depend to a great deal on the actual amount of qualifying facilities (QFs), independent power producers (IPPs), Casazza. Schultz & Associates. Inc. IV-7
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and large customers involved in power transactions. compared to the overall actual size or the system. 2. Proc1d11ral Chang,s O~ralion la order to maintain the reliability of the system, the responsible utility must monitor power flows and adjust generation in various locations so that the nrst contingency criterion is observed. SCE must also have the ability and authority to control all generation regardless or its ownership. This control is required, both under normal conditions and in emergencies. to maintain system reliability and economy. a. Information Required by SCE To operate reliably and economically, SCE will require detailed advance information concerning operations and requirements of IPPs. QFs, and large customers. Specifically, QFs. IPPs and large customers would have to provide their hourly load and generation schedules to SCE one or two days in advance. IPPs and QFs would have to provide projected generating costs on an hourly basis. Also, Qfs and IPPs would have to keep SCE informed or any changes in the capacity of their units as soon as they arc aware of them. This necessitates communications with the QFs. IPPs, and large customers who may be transacting power with outside suppliers. b. Determination of Generation and Transmission Adequacy Based on this advance information and as part of its operations planning, the utility will determine which units should be run, which units should provide spinning reserve, and which units should provide rcgulatin1 reserve. They will also check the loadin1 conditions on the transmission system for various contingencies, as well as for various other scheduled tran'sfcrs. This check will involve review of voltage and reactive conditions to make sure that reactive capacity is adequate, to maintain good voltage at heavy load, and what steps arc needed so as not to produce excessive voltages at light load. The utility will also investigate proposed maintenance schedules as well as ensurin1 that sufficient capacity is available on the system at all times to meet area control requirements including tic-line and frequency controls. Casazza, Schultz & Associates, Inc. IV -a
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c. Ability to Perform Incremental Cost Dispatch Maximum economy in system operation is obtained if all generator units operating at any particular time are operating at the same incremental costs. Dispatch should also be scheduled among the various thermal units so as to make maximum use or available hydroelectric energy. The necessary incremental production cost data will be available Crom the Southern California Edison units. Such incremental production cost data is also required from the various IPP and QF units if overall optimum system scheduling is to be achieved. If such information is not available from the IPPs and QFs. but rather only the price or electricity to Southern California Edison is available, incremental cost dispatch based on this information would not necessarily minimize total fuel costs on the system. We conclude that maximum economic efficiency requires true systemwide incremental cost dispatch and that this efficiency cannot be achieved unless the IPPs and QFs provide incremental cost dispatch data to SCE. Similarly, when generation is adjusted, up in one place and down in another in order to change transmission system loadings to meet safe transmission limitatio .. s, there are usually a number or choices of where to make these changes, but only one of these is optimal in that it causes the least increase in total fuel costs. If this optimal choice could not be carried out because, for example, it requires reducing the output of a generator that is not under the control of the utility, then the utility and its customers would be paying an additional cost penalty to protect a transmission system which they share with the independent producer. d. Complexity or System Control The addition or a large number of small power producers to the system would greatly increase the number of individual generating sources that must be controlled by the utility. The complexity of operation increases geometrically with the number of points to be controlled, and the difficulty of operating the system would increase dramatically. Casazza, Schultz ct Associates, Inc. IV-9
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There is a limit to the number of generators and wheeling transactions that can effectively be handled Crom a single control center. If these increase significantly, more control centers would be needed, and the hardware and software of each would have to be more complex. Even with such a costly expansion of the control system, it is questionable whether the system reliability could be maintained because there is no experience available in the control of a system with an explosive growth in the number or small sources. The problem of increasing system complexity can be illustrated by an analogy to the traffic control at an airport, and the problems that would come from replacing larae airliners by small private planes carryina the same total number of passengers. The suggestion was made that in order to limit the number of players to a practical number, transmission access should be limited to producers that meet some minimum size requirement, such as perhaps 10 MW. e. Remedial and Emergency Procedures Where transactions by QFs, IPPs, and larse customers could cause safe transmission limitations to be exceeded, it may be necessary for SCE to chanse QF and IPP generation outputs on short notice. Direct control of the QF and IPP is required to achieve this if appreciable amounts of such generation exist. It is also important during system restoration after a major interruption that the utility have direct control of all IPPs and QFs. With such control restoration of service could severely hampered, personnel safety jeopardized and risks of damage to equipment increased. The need for such direct control will increase as the number of NUG genera tors increase. f.. Contract Requirements with NUGS As part of the implementation of the utility's control authority, the NUG should be required to: Provide telemetering, controls, and voice communication; Casazza, Schultz cl Associates, Inc. IV-10
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Provide necessary advance warning of chanaes in future operation; Provide incremental energy production cost information to the utility; Employ qualified operators and maintenance personnel; Permit the utility to directly control operation of the unit, including disconnecting the unit if reliability requires it; Install and set relaying and protection schemes in accordance with the utility's specifications; permit the utility to test them as required. This includes underfrequcncy relays to protect the NUG unit, whose settings should be compatible with the utility's load shedding program. 3. Proc~dural Changes Planning a. Advance Notification Required Because of the Iona lead times needed to build aeneration and transmission facilities, the plannin1 of a utility's generation and transmission requires adequate advance knowledge of the plans of other providers of generation and of any of their larae customers who may wish to obtain their power from outside sources. Therefore, advance notification in the order of at least three to five years would be required for QF and IPP installations, and for large customers who intend to change to another supplier or to return to the SCE system. The notification must include adequate technical details, including the projected capacity and energy to be supplied, and scheduled service dates. Contractual provisions should define the conditions under which changes in service dates would be allowed and the penalties for non-compliance. b. Provision of Adequate Generation and Transmission Capacity Without such notification, alternate aenerating facilities will be under construction and sufficient time to add the necessary transmission facilities will not be available. The NUGs would have no capacity value and firm transmission service usually could not be offered in such a situation. Casazza, Schultz & Associates, Inc. IV-11
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Also, SCE would have to increase its generation and transmission reserves (build facilities not otherwise needed) in order to maintain acceptable service reliability in the face of greater uncertainties in load projections and greater uncertainties in future wheeling requirements. In addition, where the required additional generating capacity is expected to be provided by a NUG, uncertainties exist concerning both the completion date for the project and the future availability of the additional generation. This uncertainty will also increase required generation reserves. c. Impact on Operation of Pool and Reliability Council While a relatively small number of NUGs will not significantly affect the functioning of SCE, the California Power Pool, or WSCC, the situation will change as the percentage of generating capacity provided by non-utility generators increases. It is essential for the maintenance of reliability that all generators comply with the operatina criteria and control and design auidelines of WSCC. This raises the question as to whether the owners of NUGS should become participants in activities of pools and reliability councils. Their role could have adverse effects on the functionin1 of. these organizations. The owners of the NUGs will be primarily concerned with the optimization of their earnings Crom their own facilities. The utilities, however, have a larger viewpoint and arc concerned with the overall functioning of the system. Having the NUG owners participate in the deliberations and decision-making of the pools and reliability councils could therefore lead to a change in focus from the optimization of the entire system to optimization of individual profits. This would have a serious deleterious effect on system reliability and overall system costs. 4. Technical Changes Planning Depending on the nature, amount, and location of potential QFs, IPPs, and larae customers shopping for power supplies, the utility may need to make some of the following technical changes: add transmission facilities to provide for greater uncertainties; Casazza, Schultz & Associates, Inc. IV-12
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install special devices Cor reducina the QF or IPP generation very quickly iC certain continaencies occur; add devices (remote control or circuit breakers. phase shiCters, etc.) to control individual circuit loadina under various conditions and contingencies, or provide extra generatina capacity to maintain quality of service under greater uncertainty. Scenario l -All Source Competitive Biddin1 for New Generation with Mandatory WbeeU01 The essence of Scenario 3 is that competitive biddins is required for all new utility aeneration. Utilities may participate in the biddina both to serve their own loads and those of other utilities, with, transmission access as a condition for this participation. Unlike Scenario 2, this scenario does not provide for supplier shoppins by customers. 1. R1,u/alory and u1islati,, Chan11s Reaulations promul1atin1 procedures to evaluate competitive bids for potential new aeneration will be required. It is anticipated that the all-source competition for providins generation will be based initially on the utilities' determination of how much base load, intermediate, and pcakins capacity is required, and when. Because diff crent types of aencration acnerally involve different lead times for construction, the competition for diCCcrcnt types of capacity should be timed according to these lead times. Another factor in detcrminina the timing of the all-source competition should reflect the fact that the process of state participation and approval of the decisions involved will normally require additional time, increasina lead times. The requirement for mandatory wheeling docs not presently exist and can only be implemented throuah legislative or regulatory changes. 2. Proc,dural Chang1s -Operation Casazza. Schultz cl Associat,s, Inc. IY-1 J
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The same chanaes in operations procedures as were discussed for Scenario 2, apply to this scenario also. 3. Procd1,ral Chan1,s Plannin1 The procedural chan1es in the plannin1 process which were indicated for Scenario 2 also apply to this scenario, with the exception to those referring to larae customers, whose riaht to chanae supplien is not included in this scenario. Because lead times are 1reater, however, uncertainties in future requirements and costs will also increase. This will increase the required aeneration reserves. As in Scenario 2, uncertainties will continue to exist concernin1 the service dates for the NUGs that arc selected and the future availability o_r these generator units. DiUiculty will also be experienced in determinina the optimum amounts of base load, intermediate and peakina capacity to be added to the system because the optimum mix of 1eneratin1 types depends on the cost and performance differentials which will not be known until bids have been received. 4. Ttchnical Changes The technical chanaes associated with Scenario 3 are expected to be the same as those listed for Scenario 2. Scenario 4 -Generation seuented from Transmission and Distribution Services In brief, this scenario calls for separation or the generation function of utilities into separate deregulated companies, with transmission and distribution companies remainina reaulated. The distribution companies would be responsible for securing power supplies from competina suppliers. Generation and transmission companies could sell directly to larae customers. 1. Rttulatory and L1gisla1iv1 Changts Casazza, Schultz & Associates, Inc. IV-14
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For this scenario, the tra4smission company (or transmission/distribution company) would be responsible for the reliable delivery of power from the generation companies. This means that it must have the authority to adjust the scheduling and dispatching or generation in order to maintain reliability of service in the face of existing conditions and possible contingencies. Legal or regulatory procedures to establish this authority are needed. The deregulation of generation and the separation of integrated utilities into generation and transmission/distribution companies, would also involve extensive regulatory and legislative changes. 2. Procedural Changes Operation a. Responsibility for Control and Scheduling I For this scenario, it was considered evident that the transmission company (henceforth referred to as TRANSCO), in order to carry out its responsibility for the secure operation of the transmission system, would have to ensure that the totality of the power transaction schedules developed by the generation and distribution companies do not result in power flows which conflict with the limitations of the transmission system. It would, in effect, inherit the basic system control responsibility f ormcrly held by SCE as an integrated utility. As a result, TRANSCO will need to have the right, and the tools, to adjust these proposed schedules and actual deliveries when necessary in order to maintain service reliability and to assign control functions to specific generation units. This authority should be specifically defined as part of all contracts between TRANSCO on one h:ind, and generation and distribution companies on the other, in accordance with legal or regulatory requirements. b. Information Required by TRANSCO In order to perform its function of controlling power flows for system reliability, TRANSCO will need all the scheduling information required from generators, as explicitly listed for Scenario 2: hourly generation schedules, and the state and capaci.t_y of all generating sources. Casazza, Schultz & Associates, Inc. IV-15
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c. Determination of Generation and Transmission Adequacy TRANSCO, as the single central authority available, would have to determine whether the generation and transmission systems can reliably serve actual and projected loads usina the schedule acneration. Specirically, th.:y would have to ensure the availability or adequate spinnina reserves, other operatina reserves_. and regulatina capacity. Also, they would need to monitor the transmission system and determine whether it is capable or carrying present and future loadings including provision for possible contingencies. d. Tic Linc and Frequency Control TRANSCO would need to arrange at all times for the control of the system, including in particular, for Automatic Generation Control (AGC). This can only be done by assigni~g to a larae number of generating units the task of increasing or decreasing their output to match the constant rise and fall of customer loads and occasional changes in generation output, and to adjust output as needed to maintain the system frequency at a constant 60 Hertz. Participation in this regulating duty reduces a unit's fuel efficiency and tends to increase its maintenance requirements; so that generation companies can be expected to participate in area control only to the extent that they arc required to by contractual arrangements, and to the extent that their participation is verified by TRANSCO. c. Ability to Perform Economic Dispatch In order to maintain the benefits of economic dispatch based on incremental costs as a means of minimizing overall generation costs, TRANSCO would need contractual agreement of its suppliers to operate under such a system. The TRANSCO would have to have communications with each of its supplying generation companies to notify them of the required generation. The generation company would have to supply its incremental cost data to TRANSCO. This implies a complex and frequently changing data communications system. If, as seems likely, agreements with suppliers providing for economic dispatch Casazza, Schultz & Associates, Inc. IV-16
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by TRANSCO may not be feasible, a considerable loss of economic efficiency would result. r. Remedial and Emergency Procedures System restoration in the case of a full or partial system collapse will involve particular difficulty as responsibility for aeneration is scattered among a large number of independent parties. The time required to restore service, the possibility of a new collapse in the course of restoration, and the danaer to personnel and equipment. will worsen to the extent that a common control of the transmission and generation systems is diffused. Direct control by TRANSCO is therefore essential. If TRANSCO found threats, present or future, to system reliability based on its evaluation of system adequacy, TRANSCO would need the authority to determine the best remedial measures. and to carry them out. The latter would include reducing or increasing aeneration of specific units, including starting up units not in operation, to provide the necessary operating reserves and to adjust transmission loadings. The arrangements for prompt or immediate action when a TRANSCO is supplied by a number of individual 1eneration companies. and when these in turn may be dealing with several transmission companies arc particularly difficult, and may in practice be unworkable. One of the last extreme measures in preventing an imminent system collapse, or in reducing its extent, is to shed load, that is, to deliberately interrupt service to some customers. selected with a view to potential eff ccts of interruptions and to geographical dispersion. This is gcnenlly done with pre-planned automatic control action. TRANSCO needs the authority and physical means to shed loads on an equitable and technically justified basis, without regard to which distribution company serves these loads. 3. Procedural Changes Planning a. Load Projections and Power Supply Planning Casazza, Schultz & Associates, Inc. IV-17
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Under this s.:enario, the distribution company or transmission/distribution company will be responsible for assuring a reliable generation source for its customers. To do so, it will have to obtain advance information on its future loads and make advance arrangements with generation companies in sufficient time to provide for the lead time needed to build these facilities. Adequate methodologies exist for forecasting distribution loads but not Cor predicting future customer switching. It should be the responsibility or this distribution or transmission/distribution company to arrange for different types of generation (base load, intermediate, and peakina). Reasonable lead times for this activity would be: ten years for base load generation; seven years for intermediate generation; (our years Cor peaking; and three to ten years (concurrent with the lead times r or generating units) for any units whose location would require reinforcements of the transmission system. IC this schedule is met, and the transmission/distribution company correctly projects its future needs, no increase in generation reserve requirements is theoretically needed. On the other hand, there will be strona incentives for the transmission/distribution company to underf orecast long-range needs. This would keep their advance financial commitments to a minimum and avoid risk of fu:ure excess capacity. It will, however, resuu in excess amounts or short lead capacity being installed at considerable economic penalty or a decline in reliability. Present utility practice in generation planning is to require a diversity of fuel types, to avoid excessive dependency on one type of fuel whose sources may be interrupted, or whose use may be limited by environmental or other situations. Scenario 4 provides no defense aaainst this. IC one fuel should become cheaper than others in a region for a long period, such as a decade, there would be a strong tendency for all the generation companies to build generation using this same fuel, and no NERC reports show a range of lead times for the planning, s1t1ng, and construction of transmission lines or three to ten years, with an average or S years. Casazza, Schultz & Associates, Inc. IV-11
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one entity responsible to prevent it. National dependence on oil and gas would undoubtedly increase because of the lower capital costs of plants burning such fuels. b. Transmission Plannina It will be the responsibility of both aeneration and distribution companies to make arranaements with TRANSCO to deliver the power from aeneration to distribution. TRANSCO will require adequate notice of these requirements so that any necessary facilities can be built. This notice requirement corresponds to the notice of three to ten years referred to in Section 3a above. Lackina adequate notice, TRANSCO would be limited to in transmittina the power on an as-available, or interruptible, basis only. TRANSCO would plan the expansion of its transmission lines and substations in accordance with present plannina techniques, but based on the requirements defined by aeneration and distribution companies. This would include providing transmission for contracted services, that is, buildina a transmission system capable of carrying out contracted transactions under reasonable contingencie~ based on reliability standards similar to tho,e in use today. It would also be essential that facilities installed by TRANSCO to meet specific requests of aeneration and distribution companies be paid for, whether ultimately used or not, i.e~ a take or pay arranaement. TRANSCO would not be likely to install any facilities for unexpected needs not specifically contracted for by aeneration and distribution companies. c. Certainty of Load and Generation Projections Individual load projections made by distribution companies may be wrong. Generation contracted for by distribution companies may be late comina in service. While these occurrences are not unknown in present utility planning, the responsibility for maintaining service lies with a sinale organization, the supplying utility. A distribution company that overestimates future loads will pay for unnecessary commitments. If it underestimates its loads, it may suffer occasional interruptions but more often the effect will be that it will have to purchase the deficient power at a higher cost on some type of spot market. Either of these cost increases Casazza, Schultz cl Associates, Inc. IV-19
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will be renected in the customers' rates. Increased interruptions would increase consumers' economic penalties. A 1eneratin1 coa:pany may Cail to produce the capacity and energy for which they have contracted. IC the deficiency is larac. in power interruptions will occur. IC it is small. power may be available Crom more costly units in the same generation company, or Crom other companies. How the additional costs will be borne will depend on the contncu between the aeneration and distribution companies. These possible unexpected chanacs in aeneration or loads will have an impact on the power transferred by TRANSCO. This could affect the reliability of the transmission system. and TRANSCO may have to order chanacs in generation at diCCerent locations. Any costs should be borne by whichever party is not meeting its contract requirements. d. Maintaining Reliability and Coordination It may be noted that in discussing Scenario 4, the ground rules or maintaining existina levels or reliability and inter-utility coordination cannot be met. Lowered reliability will result with this scenario. This will result since there is little expectation that the aeneration and transmission functions can be separated into organizations with diCCerent 1oals without a loss or coordination. While TRANSCO may build a transmission system that meets present standards for operability under ordinary contingencies, it will be very difficult under this scenario to obtain quick coordinated action under severe contingencies. particularly those more severe than provided for under plannina standards. In addition, the diffuse responsibility for planning generation is likely to result in undesirable mixes of generation types and excessive dependence on one type of fuel in a region. 4. Technical Chanres The technical changes associated with Scenario 4 will consist of changes in the aeneration mix toward smaller units and increased dependence on the fuei that is cheapest in the region. Casazza, Schultz cl Associates, Inc. IV-20
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System controls, such as AGC, may become even more complex due to the proliferation or small units which will have to be controlled and participate in area rcaulation. Scenario s -Common Carrier Trapsmipion Services in a Piaa11re11ted. Market-Qrieptc4 Electric Power Industrv nis scenario varies Crom Scenario 4 in that transmission companies are completely separated Crom distribution companies as well, and arc required to provide transmission services as common carriers. 1. it.platory and u1isla1i,t Changts Scenario 5 would require the same regulatory and legislative chan1cs as Scenario 4 establisbina the control authority or. the transmission company, deregulating the acncration and disagareaating the utilities -and also provisions to define the responsibilities of transmission companies as common carriers. 2. Proctdural Chan1ts Op,ratinr For this scenario, the opcratina chanaes would be the same as for Scenario 4: the transmission company, bein1 responsible Cor the reliability of the transmission system, needs the authority and the tools to adjust proposed schedules and actual deliveries in order to keep power flows within reliability limits. The definition of the transmission company as a common carrier cannot make much of a difference in operation: TRANSCO will handle those transactions that it can without jeopardizing reliability, and presumably not Jthcrs, with or without this designation. 3. Proctdural Changes Plannin1 ne planning chanacs involved in this scenario depend entirely on whether the term, common carrier, is interpreted as meaning that the transmission company must stand ready to perform any requested transmission service on s~ort notice, i.e., within less time than that needed to build additional transmission facilities (typically three to ten years), or whether it must only be ready to provide firm Casazza, Schultz cl Associa tcs, Inc. IV-21
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transmission upon sufficient notice and subject to a financial commitment (take-or pay). and transmit power on an as-available basis in the meantime. In the second case. the technical chanaes are similar to Scenario 4. The followina discussion applies to the first case. in which TRi. NSCO is expected to accommodate any transmission request without previous notice. or perhaps somethin1 in between, in which TRANSCO must be ready to accept some short-notice tnnsfen but not to satisfy unusually sudden and large transactions. The transmission company will have the responsibility for providina transmission capacity to supply any potential consumers from any potential source. This will require studies of all reasonable combinations of source and consumption points. Taken to its loaical extreme. this would require a arossly overbuilt and costly transmission system. whose actual utilization would be very low. 4. Technical Chan1ts Additional transmission lines. compared to the requirements of S:enario 4, would be needed to provide common carrier service if the advance notice provided in Scenario 4 would not be provided. Transmission facilities that would make possible a full spectrum of sales between suppliers and purchasers would be needed. This would involve a very major expansion of the transmission system; many of the additional facilities would be under-utilized most of the time. Casazza. Schultz & Associates. Inc. IV-22
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V. PJM INTER.CONNECTION CASE STUDY A. Means of Increasing Transmission Capacity The economy of PJM acncration is frequently limited by the transmission system's capability to transfer power Crom west to cast while observing their rules of safe operation. Because or these limitations. PJM has taken a number of steps in the past to increase the transmission system's capability, and is considering additional ones. The tnnsmission system's capability to transfer power is usually limited because of a continaency consideration: the fact that if one line were to be suddenly tripped out, another line would be thermally overloaded or, more often, subject to excessive voltaic drops. Thercf'ore, methods to increase the capability of the system may fall into one of two categories: either to remove the bottleneck by increasing the capability of the individual line which would be overloaded during one of the continaencics. or to chanae the power nows on the system in such a way as to alleviate the limitation with this amount or power transfer. The following arc some steps that have been taken in recent years in order to increase transmission system capability: I. Corurol of lndiYidlUll Lin~ Loadin1s For a aivcn pattern of generation, there arc three methods in which transmission limitations can be relieved without actually building new lines or removing lines from service. One method is to use phase-shiftina transformers (phase shifters) to chanae the way the power flow divides alona different paths, decreasing the flows that are too hiah and incrcasina others that can safely be increased. PJM intends to install two 345-kV phase shifters at Ramapo substation, near the border between New Jersey and New York State, that will control loop flows through the PJM system. (While, in some situations, phase shifters can increase system transmission limits by changing the division of power flows, they are not a universal cure because of their cost, and because control problems can arise if they were applied in many phases. Also, the indiscriminate use of phase shifters to resolve specific Casazza, Schultz & Associates, Inc. V-1
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problems may give rise to other problems at other locations that are equally severe. Another way is to change the impedance of a transmission line. The impedance of a circuit is a basic characteristic of a line depending on its length and confi1uration. Power nows on parallel paths divide on these paths according to their relative impedances; more power flows on the paths with lower impedance. The impedance of a line can be increased by inserting series reactors in them. This was done by Philadelphia Electric Company on the Graceton-Nottingham 230-kV line and by Public Service Electric & Gas Company (PSE&G) on 138 kV circuits in several Northern New Jersey locations (Figure VI-I). Another way of increasing the impedance of a circui~ if it is directly connected cin series) to a transformer, is to order a specially-designed high impedance transformer. PSE&G has done this in two locations to limit the current through 138-kV cables. A third method consists of using special measures in a corrective mode to change power flows after a contingency actually occurs. Special measures arc used relatively rarely on the PJM system as compared to SCE and the western systems. Recently, however, when a major transmission line crossing the Delaware River was put out of service for a long time due to being hit by a ship, arrangements were made to trip a generating unit at the Salem nuclear plant if a specific transmission line (Salem-Deans) was lost. The loss of the Salem-Deans circui~ with both generators at Salem operating at full load, would have caused the instability of generation in the eastern PJM area. Classic preventive mode operation would have required reducin1 the level of output of the Salem or Hope Creek nuclear units for the duration of the outa1c of the river crossing, and would have caused a much larger economic penalty than the relatively rare tripping of the Salem unit. Casazza, Schultz & Associates, Inc. V-2
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1 j..., ----FIGURE V-1 SERI ES REACTOR SITES .. ..... -,~ --~ -=--,', I'. \ ....... -r I Bergen Area (PSE&rG Co.)
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PJM is very concerned with possible malfunctions of special remedial measures, and particularly with potential unpredictable interactions between them if there are many of these schemes. Network rearranaements. Sometimes. openina a transmission circuit is an effective way or reducing transmission limitations. This is particularly true when the loss of a high-voltage line would result in overloading a lower-voltage line. In the summer of 1987, the Hosensack-Buxmont 230-KV line was opened 25 times in order to eliminate the transmission limitation which existed because that line would have been overloaded if the HosensackElroy 500-K V circuit, running approximately parallel to that line, were to trip out. This is an err ective step when other transmission routes to the load centers are available. 2. lncr,asing Uncontrollabl, Jloltag, Dtcay Limit When the P JM transmission system is the limiting factor, 85% of that time the limitation is due to voltaae-related factors and 15% of that time it is due to thermal limitations. If the transmission limit is exceeded and certain contingencies (aenerator, line or transformer outaaes) occur, the voltaae in the receiving part of the system would drop to such an extent that uncontrollable voltaae decay would occur. The effectiveness of many reactive power sources would be reduced at the same time that additional reactive power would flow on transmission lines. These increased reactive power flows would in turn cause additional drops in the voltage with the effect that system voltage would collapse. Such sequences of events have happened a number of times in the past, especially on foreign systems. It was the cause or a blackout of a large part of the Tokyo area in 1987. A number of measures were taken in order to alleviate the limits on the PJM transmission system related to uncontrollable voltage decay. 2945 MVar of capacitors were installed on the PJM bulk power transmission system. Voltage profiles were chanaed. 230-kV lines were upgraded Casazza, Schultz & Associates, Inc. V-4
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3. lncrtasin1 Thtrmal Limits Thermal limitation (danger or overheating a component or the transmission system due to excessive current flowing through it) in the case or a contingency is the limitina factor on the transmission system 15% of the time. The following steps have been taken in order to increase the thermal limits or the transmission system: Chanaina ratings with ambient temperatures. The thermal limitations on a component depends on the ambient temperature. In cold weather. a component can safely carry more current before it reaches a given maximum permissible operating temperature, than in hot weather. In the past, components were rated based on the highest ambient temperature which was likely to occur. Typically, three separate ratings might be used for summer, winter, and sprin1/fall. It hu no_w become possible to make the ratinas vary with the actual ambient temperatures by entering the relationship between the ratings and the ambic-nt temperatures, as well as the ambient temperatures, in a dispatch computer. This has permitted increasin1 the thermal limit or the component whenever the weatheris relatively cool. Replacing the limiting components. Sometimes the thermal rating or a transmission line or transformer is limited by the thermal limitation or a relatively minor component, such as a wave trap, a metering device, etc. In these cases, the capability or the transmission system was incr~ased at relatively little cost by replacing these minor components. Basing thermal ratings on four-hour limits instead of longer-term ratings or continuous limits. Since thermal ratings arc based on limiting the heating of a component, and heating is a gradual process, an overloaded component can safely sustain a heavier loading if this loading will only continue for a short time. Therefore, the thermal rating or some components was increased by basing it on the amount of load the. component can carry for four hours without overheating. This rating, if used in connection with contingencies, is generally sufficient to permit the system operator Casazza, Schultz & Associates, Inc. V-5
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to make ch1n1a in the aeaeratioa pattern and thus relieve the overload on the component ia the time allottea. Rcsa11ia1 circuits. Oa some traaamiuioa lines, the thermal limit is determined by the amountor 111 ia the conductor when the conductor e1pandl as a rault or overhoati11, When the saa 11 exccuive. the conductor may come too close to the around and create a safety hazard. Some compaain have round it possible and cost-ertcctivc to increase the thermal ntina or some tran1miuioa liaa by reducin1 the SIi on critical spans. The feasibility or this technique depends oa the construction or the tower and the amount or increased tc111ioa that is permissible. Ba1ia1 line radap on bi1her conductor temperatures. As mentioned earlier, tnumiuion line ratinp arc aenerally based on the maximum temperature that a conductor is permitted to reach when carryina the Cull ratina. The hiper the temperature, the arcatcr dam11e can be done to a conductor whenever the ntin1 is reached. Typically, the duration or operation at hi&b temperatures durina the lifetime of the line results in annealing of the conductor metal. leadiaa to brittleness and possible shortenin1 of e1pccted conductor lire. Since some lines are not expected to operate at hip temperat11ra very ortea. some companies have iacreucd their thermal ratina in such a way as to permit the conductor to reach the relatively hiah tempcnture or 160C without causina an excessive accumulation or annealina. In these cases. the structures were modified to increase the conductor hei1ht to permit the increased SIi at 160C. 4. 011-llu com,nur contin1ncy analysis The dispatch computen or both the PJM Interconnection and the individual membcn coutantly monitor the actual currents flowina on all transmission lines. Periodically, depcndin1 on the capability or the computer, the effect or various continaencics arc calculated to determine whether any or the continacncics would lead to overloads or c1ceuivc voltaic drops ir they occurred. The frequent recalculation or these coatin1encics permits lo1din1 the transmission system to the Cullat S1re limits. instead or havin1 to rely on pre-calculated limitations which must Casazza. Schultz A Alloclata. Inc. V-6
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include a substantial safety ractor to account ror pouible variations between actual and expected nowL B. Problems with Transmiuion Access and Wheelina PJM bu accommodated the addition or a number or non-utility aeneraton (NUGI), representina a relatively small part or the total aeneration or the PJM system. Based on their experience with these NUO.. and otben that are proposed, PJM expreucd a number or concerns about the errecu and the costs to utilities and their customen or requirina the utilities to buy power aenented by the NUGI, and to wheel power ror them. The Collowin1 are some or the specific concerns expressed: Difficulties in keepina the system operatina while makina reinforcements needed because or the addition or NUG racilitiCL For example, one typical system reinforcement consists or circuit breaker repla~ements. Addina aeneration to the tnnamission or distribution system increases the short circuit currents that circuit breaken must be capable or interrupting. These circuit brcaken were ori1inally selected based on the utility's aeneration expansion plans. with the expectation that they would not need replacement tbroupoat their normal expected lire. IC a NUG is added where no aencration bad oriainally been planned, hiaher short-circuit currents may occur, requirina replacement or the edstina circuit breakerL Also, conductors may have to be replaced by larger ones. and other system rearranaements made, to accommodate lar1er currents resulting from additional, and oriaiaally unplanned, aeaeration sources. The application or avoided cost pricin1 as a requirement of the Public Utility Reaulatory Policies Act (PURPA) has brou1ht about some unreasonable ud uneconomic requirements on the members. In one case, due to peculiarities or the way that avoided costs are calculated, 1 member is payina more ror eneray (i.e.. without auarantee or availability) than for combined capacity and ener1y (i.e. with some auarantee or availability). Inconsistency in avoided coat definitions between the different states is expected to make both plannina and operation more complex. Cuam, Schultz .t Aaociates. Inc. V-7
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The impact or non-utility 1cncnton on the operation and pl1nnin1 or the PJM system ls illutnted by a situation in tbc Northern part or the Pennsylvania Power and Liaht Company (PL) service territory. A number or new 1encraton proposin1 to burn culm (anthracite minin1 waste) have emeried in that area. The calm ls considered ID environmental hazard and probably a safety hazard also. Tbe transmiuion tyiDI this area to the rat or PL and PJM wu not desi111ed to accommodate the expected amount or NUG 1eneration. some 100 to 1000 MW, in addition to the existin1 PL 1eneration. Studies indicated that a stability limit would restrict the amount or NUG 1encration in that area to 465 MW. Even at this level, it will be neca1Iry to limit the output or NUGs under certain conditions and PL 1eneration in the area will have to opcnte with certain minimum reactive power outputs to maintain stability. This limit on NUG output ii a function or load level in northern PL As load 1row'9 the amount or NUG 1eneratio11 that can be accommodated will increase. As a result or neaotiatiom between PL and prospective NUGs. an understandina has been reached about ratrictiom on the amount or NUG to be installed, and on operatin1 procedures and financial arranaements to curtail production when conditiom 011 the electric system make it necessary. The Pennsylvania Public Utility Commission wu petitioned for a declaratory judament endorsina tJw aareement. The Commission round the terms or the Joint Petition arc jut, reasonable and in the public intef'esl C. Implementation or Dereaulation Scenarios Each or the five contemplated dereaulation scenarios requires certain chanaes in PJM's and individual memben' procedures and in the PJM physical system so that it may be implemented in accordance with the around rules assumed for these studie'9 which arc repeated here for convenience: I. no decline in reliability or service to the ultimate customer: 2. keepina all the benefits which are presently derived from interutility coordination and iaterchanae or economy power; wh,ile 3. providina for the chanaes in the overall system dispatch and in the type, size, and location or aeneraton Crom the way they would be under the Casazza. Schultz A Aaociata. Inc. V-1
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present reaulatory rules (Ir there were not chanacs in these. then the chaaacd rcaulatory scenario would not chanae the overall operatina and production economy). Apia. ia this section. the chanaa required to implement each scenario are presented as they were developed by PIM in discuuion1 with the investiaaton. They arc divided into reaulatory and leaislativc chanacs. procedural chanaes arrectina either the operation or the plannina or the system. and technical chanaes involvina chanacs in physical equipment requirements. Sc;c;narig 1 scuu3 Quo PJu3 Rolling Prudepcy Beview1 1. R1platory and IA1islatiJt Chan11s Even thouah Scenario I represents the present reaulatory and legal situation. with the exception or the institution or rollina prudency reviews. there is a need expressed ror two chanaes: ne institution or rollina prudeacy reviews: in itself. appears to need lcaislative support in biadiaa later utility commissions to accept the decisions or the previous ones. Lackia1 this. rolling prudency review could not be errective. A number or opcratina requirements (see below) and plannina requirements may need rcaulatory or leaislative backina. The petition of PL and NUGs Cor a declaratory judament discussed earlier in this section. is a good example or such a need ror reaulatory backina. 2. Proc1dural Chan11s 01MrtUin1 While present operatina practices have been reasonably adequate until now (see concerns in Subsection B above. however). PJM is concerned that problems that can be lived with when there is only a small amount of NUG generation can become major problems as these resources arow propartionally more. Therefore. even under an expanded Scenario 1. in order to maintain the existina benefits of reliability and Caazza. Schultz .t Associates. Inc. V-9
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economic opcntion, NUOs should be subject to the same operatina rules as if they were under utility ownership. Specifically, the PJM member utility to which the NUG is connected should have the authority to do the followina for these units: One to two workdays in advance: Schedule unit commitment; and Schedule unit output, in accordance with system economic dispatch. Continuously: Schedule spinnina and re1ulati111 reserves; Subject the unit to tie line and frequency control, on the same technical basis u a similar utility-owned unit would be; Schedule unit voltaic and reactive output; Include the unit in a remedial mcuurcs proaram. if needed; and Curtail unit output if necessary for transmission reliability. As part or the implementation or the utility's control authority, the NUG should be required to: Provide telemeterina. controls. and voice communication; Provide necessary advance warnina of chanaes in future operation; Provide incremental ener1y production cost information to the utility; Employ qualified opcnton and maintenance personnel; Permit the utility to directly control operation or the unit, includin1 disconnectina the unit if reliability requires it; and Install and set relayin1 and protection schemes in accordance with the utility's specifications and permit the utility to test them as required. This includes underfrequency relays to protect the NUG unit, whose settinas should be compatible with the utility's load sheddina program. The implementation of utility control of NUGs may not be necessary to its fullest extent in Scenario l as Iona as NU Gs do not form too large a por~ion of all aeneration sources. However, sians of their future need are seen in some areas Casazza. Schultz A Associates, Inc. V-10
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or PJM, 11 in tbe case or the culm-rueled NUGt in the northern section or PL. It is important to establish tbe basic principles early, since otherwise too many of the early NUOI mi1bt be eKempted Crom the rule as part or their contracts with the utility. IC these conditions are not met, the consequences would include some or all or the Collowins: Loa or service reliability; The utility takin1 up a burden at a cost wbicb should properly be part or the cost or 1eneration; and The utility reducin1 some or its 1eneration which would have cost less than the price it is p1yin1 for power purchased Crom NUC s. Both reductio~ in service reliability and unnecessary costs to the utility are eventually renected in cost and inconvenience to the utility's customers. Even at present. some PJM utilities report that the implementation of PURPA rules. which require the utilities to buy QF power even when this power costs more tbaa the current incremental cost, ii 11aderminin1 the rundameatal around rules of maintainia1 reliability and ecoaomic benefits. 3. Proc1dural Chan1ts Plannin1 The institution oC rollin1 prudency reviews would require periodic reviews of the utility's plans, its latest revised requirements, and the status of its major projects with the re1ul1tory commission. NUGs must notify the host utility of their plans for uait iutallation and retirement, and for wheelia1 or power to customers other thaa the host utility. Generation reserve requirements may be subject to chanae as a result of a substantial amount or NUG installations: increasing reserve requirements to make up Cor the areater uncertainty in loads and 1eneratiQn supplies, both in the near term and the Iona-term; decreasing reserve requirements as a result of smaller average unit sizes (a minor effect, quantitatively) and shorter construction lead times. Casazza. Schultz cl Aaocia tea. Inc. V -I I
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Utilitia may be rorced to build smaller units 111 respouc to the need for shorter construction lead times. This may came increased fuel costs since the types of units that can be built quickly are 111ually thou with hi1h. and potentially much lliaher, ruel coats such u au 111d oil-bur11i111 comb111tioa turbiaa. Internal PJM plaa11i111 procedures may have to be modified to renect the need ror i11cludi111 NUG data 111 pool capacity pl11111in1-4. T1el111ieal Cluul111 Depe11dini on the nature. amount. and location of potential NUO.. the utilities may need to make some of the followina technical cb1111es: Add trammiaion facilitia that would otherwise not be required; Install remedial meuura for reduci111 either the NUG or utility aeneration under variou co11ditio111 and contia1e11cies; Add devices (remote control or circuit breakers. phue shiCters. etc.) and ezpaad the ruactiou or the l11terco11aectio11 Control Computer to control iadlvidual circuit loadln1 under various conditlom aad co11tin1encies. or lacrcue 1eaeratio11 racna to provide equal quality or service under areater uncertainty. Scenario Z Egpapdin Tragsmissioo Acc;ns ip the Existio1 Institutional Structure R1pltUory and u1islall,1 Cluul111 This scenario carria the poaibility that the number or NUGs could become much areater than for Scenario 1. and may result in 111 unpredictable amount of customer shoppi111 for lower cost supplierL The chan1es referred to ror Scenario I, to provide re1ulatory and leaislative backi111 for operatina control or NUO units by the utility, are therefore more uraently needed in this scenario. Casazza, Schultz cl Auociatcs, Inc. V-12
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The coatrol or NUG opentioa by utility operators, described for Scenario 1, to emure ovcnll system reliability and economy is made more acceuary by the potentially laraer amount or NUO aeneration aad the potential Cor substantial customer 1boppiaa. ne potential competition between utilities, includina members or PJM. for ind111trial c111tomen raila the 1troa1 probability that many rorms or cooperation between utilities that have been customary in the put may become weaker or disappear. These rorma or cooperation ranae Crom the rree exchaaae or information to scadina work crews to help another utility which bu surrered severe storm damaae. Coacernina the latter however. some PJM members reel that this pnctice would remain, because in tima or natural disaster we appear to pull toaether. 3. Proc,dural Cluvr11s Plallllin1 la addition to the chanacs indicated ror Scenario I, there would be a need for a PJM procedure, or protocol, to report customcn' plans ror chan1in1 suppliers. Care mutt be taken to avoid erron or omiuion or duplication. so that the needed capacity will be provided. but will not be provided twice. by both the present and future host utilities. la plaanina as in operation, inter-utility cooperation may become a victim of competition Cor customers. The exchanae or plans to acquire customers from third parties, Cor example, is most unlikely, as it miaht endaaaer the proposed deal. Competition for low-priced eaeray suppliers would entail similar problems. 4. Ttclulical Cluut11J Auumina laraer amounts or NUG aenentioa than with Scenario 1 and a substantial amount or supplier shoppina by larae customers, the changes described for Scenario 1 would also apply, but" on a laraer scale. Cuam. Schultz A Auociatcs, Inc. V-13
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Ss101do 3 An Source Cgmpetitjye li44ia Cor New Atoen&ioo with Mao411on DeeUa Lqislatlve or re111l1tory cbanaa would be needed to define rules to protect all concerned. includlna utility cutomen. Sucb ch1n1a are always very complex becaue tbeJ are applied to many dlCCerent 11t11atloas. and they often have unexpected raaltl. While tbae cue 1t11dia were intended to examine the techaoloaical aspects or lmplementina the Cive re111l1tory cbanae scenarios. the tecbnoloaical scenarios are impacted by public lnterat and public policy considerations. and it is impossible to keep tbe two typa separate. Certain or the Collowia1 points involve tbe interface between tbe technical and DODtechaical areas. but they were mentioned by the utilities. The utility lllould be responsible Cor writina detailed desi1n specifications to be used in preparin1 bids. The utility's service reliability, for which it bu Cull rapouibility, will be impacted by a plant's reliability tbrou1hout the plut'1 liCetime; the utility bu the experience to know what plant daip Ceatura are needed to produce reliability in the short and Iona nDL ne requirements ror capacity and ror eaer1y should be specified separately. The utility commialoa 1bo11ld review and approve the utility's specifications. (Not all membcn or PJM aaree that the commission should do this.) The utility should be responsible Cor selectina the best bid. The possibility or ne1oti1tin1 with several or the bat bidders should be left available. A time limit should be set on opportunities for losina bidders to appeal to tbe commission. (Some PIM members question whether there should be an appeals process at alL) The Cinal contnct should be submitted to the commission for approval. The approval or the contract by the present commission should be bindina oa future commissions. This provision should be fixed by appropriate le1islatioa. Casazza, Schultz ct Associates. lac. V-14
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2. Proc,durlll CluutlfJ Op,ratlo" The procedural cbanaes ia operation that are called for in Scenarios 1 and 2 also apply to Scenario 3. The potentially lar1c number or pouible bilatcnl aad multilateral 1rr1n1ements will increase the diCCiculty or opcratin1 the tnn1miuioa 1y1tem reliably. 3. Proc,durlll Cluut11s Pl1UU1in1 E1pcrience indicates that PJM membcn ca11 need 11 much u eiaht to ten yean' lead time to build a new transmiuioa line; there have been cases, such as the Wasbin1toa 500-kV loop (sec Appendix A) in which much more time has been needed. TbercCore firm wheelina requirements oC NUOI and 1upplier-1hoppin1 customers must be applied Cor. and the uscn' Cinancial r:espouibility firmly committed, sufficiently in advance or when the wbceliaa is to be provided. so that iC additional facilities are required. the needed system additiou can be made. The advance notice required will obviously be macb loaaer for larae wbeelin1 requests which will require the addition or new lines. 4. T1t:lmlt:lll CluurlfJ The technical cbanaes associated with Scenario 3 should be substantially the same u for Scenario 2. except that in the absence of supplier shopping by customers the amount or aeneration reserves needed to provide for load uncertainty would be less. Sseodo 4 Qencratiop se,re111ea from Transmission and Distributiop Services l. R11ulmory and u1lslatl',1 Cluln11s For this scenario, leaislative or reaulatory chanacs may be necessary to establish the responsibility and authority or individual transmission, or transmission/distribution, companies to provide Cor the reliability and economic dispatch or the power (lowing Casazza, Schultz A Associates. Inc. V-15
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tbrouall the area, tn111mlalo11. Speclrlc rapo111ibilitia and authorities will be dilc1aaed with the procedural ch1111a below. ne 11Nd ror a particularly c1teasive tnasmiuioa system would particularly emplaulze I problem that already e1ilt1 110w: the dilrle111ty and delays involved la tbe environmeatal review procaa. nen 11 110 b11rde11 placed on caviroamcatal review 11111cia to approve at leut one alteraate, nor to produce a rinal ~ecisioa wlthia I nuoaable time. Eacb or the proposed accaarioa. i11 MQacncc, implies arcater problem la obtaiai111 approval ror coutnactiaa the traumiuioa accdcd to support it. It would aot be poaible to keep tile de1ree or reliability aad or production cost avlap that arc due to PJM'1 ti1htly coordinated or1aaizatio11, without inte1ratin1 th individual tr1111miaioa/dl1tributio11 companies into 111 equally iate1r1ted Transmission Pool This pool would pcrrorm eaeatially those overall reaioaal control (unctions now performed by the latercon11cctio11 <;oatrol Center, but it would apply the same operathaa nala. coatroll. aad requirements to utility mcmben and to NUGs. Control laactiou over iadividual 1111it1, whether atility-owned or NUG, would be throuah the membcn aader the same co11ditio11s u they are now. All c11er11 purchases would be made by the Pool, but each member would be responsible ror providina his own 1eneratin1 capacity resources. Crom rirm contracts, futures aroups and brokers, and the spot market. 3. Froc,dural Clum111 Plannin1 Eacb traasmissioa/distributioa or distribution company would be individually respomible for 1uuri111 its own 1c11eratioa capacity resourceL Backup contracts would be aeedcd to provide reserves to back up ener1y purchases made by tbe Traasmiuioa Pool. Al to tnasmissioa pl111nin1, the Transmission Pool would have to supervise and coordinate transmission plannin1 by the transmission companies usina procedures similar to those used by the PJM latcrcoancctioa today. Cuazza. Schultz cl Auociatcs, Inc. V-16
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4. Tluucol Clu&l,111 n1 tecl111icar chaa111 aaociated whb Scenario 4 are c&pected to be essentially t111 u tbOM aaociated whb Scenario 3. ktPldA Cgmmoo Cttril' Ira11mie!o1 Scaisa lg I Dipl[CIICC4. Mfckt1:Ati1Qlc4 EJcmic; rocc 114,asa ID addition to cbaa1a called ror la Scenario 4, tbe derinition or the rapolllibilitia or transmission companies u common Cl"rien would require le1i1lative and re111latory cbaa1es. 2. ,roctlural Cluut1 Op,ra1l111 ne operatlD1 chan1a dacrlbcd 111 Scenarios I to 4, (orpnization or an inte1ratcd Traa1miaon Pool. widl authority to control 11neratia1 units ror -reliability and overall economy) would be required r or Sceaario 5 u well. ne Traumislloa Pool would, u a common carrier, have to inte1rate all the demands made 011 it by 1eneratio11 companies. whatever their oriain, and others requiri111 wheelins. and to make whatever adjustments are needed to maintain the reliability or the traumillion network. In orde~ to do this. it may be necessary ror the Traumillion Pool to be iatearatcd horizontally into an area-wide Transmiuion Company which would own all the transmiuioa or what is now the PJM service area. ne procedures ror coordination between 1011eration, tnn1mission, and distributi~n companies would have to be very carefully defined in their various contracts with each other. Casazza, Schultz .t Aaociata. Inc. V-17
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,. """'"' c,,.,,,., "'"""'"' Tia poaible Deed for a laorizoatally l1111ra11d PJM Tran1miaioa Compaay laaa beeD dilcuNd la tlae previou 1abNctioL nil ii a pl111i11 con1identioa u well For Ille traamlaloa company to be required to provide rlrm acrvlce whhoat btla1 al noap aotice to allow coutnctioa woald probably require a dear or traalaioa overbaildia1 tlaat ii lfOIIIJ aaecoaomic. aillcc 11111 would Imply baildiaa a traamialoa Jttm tlaat caa traufer uakaowa amoaa11 or power rrom aaywlane 10 aaywller .. bat tllat ii ued 10 perfona ODIJ a fnctiOD or what it ii capable or dolaa. It ii allo uallkely to be (euible. aivea laow mucla ju1tiricatlon 11 needed la order to be permitted to balld aew liaa. A more practical approach would be: To 1111111 "lee ii' aivn 1atrlcie11 aotice to provide adequate lead time to baild or rel.Cora racllitia u aeeded. To reqaln tlae traumlaioa compuy to show caue iC other tnnsmiuion ands canaot N accommodated. It aciditioul tnamialoa mut be ballt la order to accommoctale reqaa11 ror ratve NrYice. coatribatiou la aid or coutnctloa llloald be required rrom the nqaator, the amoaat cS.pndla1 01 the project COit aad: Whether the racilitia would have beea built otherwise; and Otlau poteatial uacn or the additioul racilitia. 4. Ttclutlclll CluJlllfl TIie 1Nd to provide commoa canier 11"ice could. dependin1 on the precise derlaitioa or tlae reqairemea11 ror advance aotic., require a moderate or very Iara lacraM in traumiaioa racilitia. Lacki11 lo11-na11 aeaeratioa plau u prcacatly prepared by electric utilities, the needs for future traa1miaion service cannot be predicted accurately, and the Cam, Scllaltz & Aaoclata, lac. V-11
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COit or maiataiaia1 duplicate tacilitia to provide service to all comers instantly woald be 1:1orbhaat. Tia Neded traumiuioa tacilitla can be built. aiven: Adequate time; SaCCicieat moaer. and Raliltic and efticieat raohation or environmental restraints. Cuaaa. Sclaaltz A Auoclata, lac. V-19
PAGE 102
APPENDICf.S
PAGE 103
APPENDIX A TRANSMISSION CONDITIONS IN VARIOUS AREAS The Collowina aeneral review or transmission conditions in various parts or the United States is based particularly on material published by the North American Electric Reliability Council (NERC). The areas discussed are those Cor which traumission constraints have been identified in NEllC reports. 1. re11sv1x1oi1-lenex-Maal1nd Jotercoooectioo The PennsylvalliaJeney-Maryland (PJM) Interconnection constitutes the majority or the NERC Mid-Atlantic Area Council (MAAC). The 1916 and 1917 NERC reliability reviews indicate that the primary transmission constraint in the area is the major west-to-east traumission path. Durina 1987, the PJM system was loaded to the limit or its capability to transfer eneray west to east across PJM 96.Sq& or the time. However, analysa conducted in 1984 and 1985 by ECARMAAC for DOE show that the existina transmission system provided an estimated 904MI or the economic benefits compared to what could be realized iC the existina transfer capability were doubled. All illcreue in nuclear capacity in MAAC in 1915-16 and the declining differential la oil/pa and coal prices have reduced the overall transfer or economy eneray from reaiom to the west or MAAC, primarily the Eut Central Area Reliability Council (ECAR). However, internal transfers of eneray alona the west-to-cast transmission path to serve the load centers in the East have maintained a high utilization or thil path. This is especially true durin1 daily pea.le load periods. The future chanaes in thil trammiaion Clow pattern are diCCicult to predict since they are heavily dependent on the cbanae in oil prices. Relatively hiah oil prices would tend to incrcuc the need r or west-to-east trans( ers. Utilida are Cindina it more and more diCCicult to expand the transmission system to meet Cuture needt due to len1thenin1 licensina processes, uncertainty reaardina the cost/benefit relationship, conClictina jurisdictions, and a lack of incentives. A perfect example or this is the attempts to complete the Baltimore-Washinaton 500 kV transmission loop. Approximately 82% or the loop is currently in service APPENDIX A AI
PAGE 104
with only two seaments rema1n1n1 to be completed. the Chalk Point-Calvert Cliffs circuit and the Bripton-Wauah Chapel circuit. nc Baltimorc-Wuhinaton 500-kV loop is intended to fulfill two roles: to provide a path ror economy power interchan1e, and to enhance system reliability by providina a path ror emer1ency power transfen which may be required durin1 major aeneration and transmission failures. The problems in obtainina the required authorizations for completin1 the loop represent an impediment to power transfen that has existed since at leut 1979. These delays have been due to a series or maneuven in reaulatory and lepl proccedinp which have successfully delayed the arantina or required autborizatiou Cor this entire period. ne difficulties experienced with the Baltimore-Wasbin1ton loop will be complicated i11 the period between 1911 and 1996 due to the increased reliance on non-utility 1eneraton for new capacity. By 1996, approximately 6.241_ or the total generating resources in MAAC could be non-utility 1enerators. The location or these non-utility 1eneraton will be critical to the overall utilization or the west-to-east transmission corridor in MAAC. As this non-utility aeneration is added to the reaion, reliability could be impaired if 1i1nificant non-utility aeneration is installed in areas where the utilities have not planned for the transmission capable or bandlina these capacity additions. 2. Southern Cali(orgia Edison Compagy The Southern California Edison Company (SCE) is a member or the Western Systems coordinatina Council (WSCC). The primary concern in the West is a disruption or the Pacific North-South Intertie. Loss or both 500-kV alternating current (AC) lines or both poles of the high volta1e direct current (HVDC) line will result in serious bulk power supply problems within WSCC. Hydroelectric aeneration from the Pacific Northwest plays an important role in the ener1y supply picture in the Pacific Southwest. The loss or either the AC or HVDC transmission lines will adversely arr ect the SCE service area. APPENDIX A Al
PAGE 105
ne NERC 1916 Reliability Assessment shows that over 31% or the planned capacity additions in WSCC between 1916 and 1995 will be non-utility generators.1 As in MAAC, the size and location of these non-utility generators will be closely watched by the utilities within WSCC to ensure that the transmission system is capable or handlin1 this divene capacity source. The California-Southern Nevada area is predictin1 the liiahest 1rowtb in non-utility aeneration. A primary concern in this area is that. in most cues. the utility has no control over non-utility generation operations under current arranaements. The utilities are required to absorb the eneray into their system whenever it is delivered by the non-utility aenerators. nis requirement further complicates the overall operation and plannina or the bulk power system in the WSCC. 3. Hgpstgg Light & Power Hoastc,n. Liaht cl Power (HLctP) has very special considerations when addressina transmission constraints. HLclP is a member or the Eneray Reliability Council or Texu (ER.COT). ER.COT is effectively isolated from the remainder of the transmission system i11 the U.S. One DC tie exists between ER.COT and the Southwest Power Pool (SPP) that can cany 200 MW or encr1y transfers. and will be up1raded to a 300 MW line i11 1919. An additional 600 MW HVDC tie to eastern Texas is beina studied and. if installed. could be in place by 1990. Other than these tie lines. ER.COT relies totally upon internal aeneration for its eneray. A major concern for HL&P currently is the 345-kV transmission line to the Lower Colorado River Authority (LCR.A), the Salem-Zenith line. This line is critical to support the bulk power transten between HL&P and the LCR.A. The Public Utility Commission of Texas rejected HLctP's request for a Certificate or Convenience and Neceuity in November, 1917. HLclP bas appealed the PUC's decision in the courts but a quick resolution is not anticipated. Another concern is the de-ener1izin1 or the 345-kV line between HL&P and Texas Utilities (TU). This line was ordered de-eneraized in November, 1985 due to questions concernin1 the methods used by HLclP in obtainin1 the transmission I. NER.C, 1986 Reliability Review; Table 7, Pa. 15. APPENDIX A A-3
PAGE 106
ript-oC-way. In April, 1917 HL&.P received Commission approval for rerouting the portion or the line that is beina questioned and the new segment is anticipated to be in-service in late 1917. 4. IcPPCPCC YUex AutJ,qrity There are several e:dstina transmission constraints beina experienced by the Tenaeaee Valley Authority (TV A). The TV A interface with the Mid-America Interconnected Network (MAIN) is a primary concern. This area (Joppa-Shawnee Paducah) bu experienced extremely hiah loadinas in the past which have resulted ia limitations on TVA's imports Crom MAIN. These limitations result Crom the larae load at the DOE uranium enrichment facility in Paducah, Kentucky, aeneration levels at various nearby plants, and interreaional and intrareaional ener1y transfen. Currently, the problems are beina mitiaated by operational procedures that require trippiaa certain aeneraton when line loadinp act too hi&h. Transmission additions could alleviate the problem, but none are planned due to the uncertainty or the ruture loads at the DOE facility. The TV A-SOuthwat Power Pool interface in Memphis. Tennessee is sensitive to both west-to-cut and north-to-south transrers. or primary concern is the heavy loadina or the Cordova-Wat Memphis 500-kV line. Some major EHV reinforcements planned durina the 1917 to 1996 time period should reduce, but not eliminate, this constrainL 5. Soptbetn EJectric compox The Southern Electric Company has two primary transmission areas or interest, the Southern-Duke interface (to Duke Electric Company) and the Southern-Florida interface (to Florida Power Corporation, Florida Power &. Liaht Company, and Tallahasee Electric Department). The Southern-Duke interface in the area or the Savannah R.iver is beina arrected by eneray transfers between other adjacent and non-adjacent systems. Some transmission system enhancements in 1986 mitigated some of the problems, but operating procedures to reduce line loadings will be in effect for the Coreseeable future. APPENDIX A
PAGE 107
ne Southern-Florida interface is not currently a constraint but rather presents an area or surplus transmission capacity. Florida still plans to import approximately 2400 MW across this interface (total capability is 3500-4000 MW) throu1h the 19871996 time frame. However, if oil prices increase sianiricantly in the future, this interface will apin .approach maximum allowable loadina ror most hours in the year. 6. De Sgpthwest Power Pggl nc Southwest Power Pool (SPP) currently hu no transmission constraints other than the Cordova-West Memphis line previously mentioned. In addition, current plans call Cor the installation or two new major interconnections. A third 500-kV line between SPP and SERC and a second HVDC line to ERCOT arc planned for the 1917-1996 time period. nesc two lines. alon1 with planned additions within the SPP, will areatly enhance the pool's import/export capability. 7. De East ceatuJ Ara BeUhiJity council ne East Central Area Reliability Council (ECAR) has adequate transmission capacity in place to serve the next ten years with the addition or almost I 00 miles or 500-kV and 300 mila or 3-15-kV lina planned. ECAR hu an extensive 765-kV network which provides which provides hiah reliability within their reaion. ne major problem within ECAR is the need to increase their transfer capability for exportina eneray to MAAC. a. De Mid-Cgptipent Area Power Poot ne Mid-Continent Area Power Pool (MAPP) anticipates no major transmission bottlenecks in the next ten years. The primary concern is that eneray transfers to the MAIN have occasionally been limited in order to ensure secure system operations. MAPP hu plans for almost 2000 miles or additional transmission lines in the next ten years. APPENDIX A A-5
PAGE 108
9. De Northeast Power Coordigatio council The Northeast Power Coordinatina Council (NPCC) is in the process of adding a major U.S.-Canada intertie. Phase I hu been completed and interconnects Hydro Quebec (HQ) to New Hampshire and is nted 690 MW. Phase II will up1nde the laterconnection to 2000 MW and extend the line to eastern Massachusetts. Of major concern is the efrect of the HQ-NEPOOL interconnection on the operation or the tnumlaion systems or the PJM and NYPP. Operatin1 auidelines are beiaa developed jointly to ensure adequate reliability in the event or a trip on the HQ-NEPOOL interconnection. Heavy nows rrom Canada to NEPOOL are expected to continue for at least the next ten years. There are two transmission concerns in New York. The first is the increased level or power traulen Crom upstate New York and Canada to Southeastern New York. A planned 200-mile k5-kV reinforcement -will permit increased displacement or oil-fired 1eneration in the southeastern part or the State and improve reliability. Second. a k5-tV cable reinforcement to Lona Island is planned for 1991/1992 installation ii needed to maintain reliability of service to the island. APPENDIX A A-6
PAGE 109
APPENDIX B EXPANDING TllANSMISSION CAPABILITY: CORRECTIVE TECHNOLOGY APPLICATIONS Corrective tech11olo11, also called remedial measures: are me:isures taken a!.1tt a co11thl1e11cy occun to prevent overloads, or excessive voltaic drops, Crom iJnerrupthla or enda111erin1 service reliabili~. They are i11 contrut to the usual practice or preventive mode operation. i11 which operation or the system is restricted so that conditions alter any si111le continaency will remain acceptable. llemedial measures arc aenerally aimed at a specific continaency. or at most. at a aroup or similar conLi111e11cics wbich have a common errect. such as overloadi.111 the same line. Fiaure B-1 repracnts a section or the SCE 220-kV system. A larac Quali!yin1 Facility (QF) (an enhanced oil recovery project) wu installed at Sycamore/Omar, with a Cirm output or 500 MW. The numbers with arrows alona the various transmission liAcs show the loadin1s in meaawacu. Under normal conditions, there are no actual overloads. However, it one or the three lines between M:launden and P~toria subst:atious trips out. the loadina or the remainina two lines increases to 380 MW each. wbich represents a 20'1 overload, u shown in Fi1urc B-2. A prevcnfrve approach would c:ill Cor reducin1 the 1cneratio11 in the North by approx'.m:uely 200 MW so that the post-contin1ency now or the two remainin1 lines would not exceed their ntina:sInstead, a remedial me:isure was instituted so that SCE"s hydro aener:uion would-be immediately reduced as required, and operators alerted to initiate manual action. SCE indic:ates that the eftic::acy or this scheme rem:iins to be demonstrated when the QF project is completed. APPENDIX I Bl
PAGE 110
... ... LIZm I ... APPENDIX I B ,. .. ... ---.. -BIG CREEK HYDRO 220kV SYSTE.~ TOTAL GENEAATJON 1000 WI Solllh,rn 'ali/of11UJ Edison ... 102
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LOADED 1'0 12a CJCIHl.dDf o-~ APPENDIX I FIGURE B-2 PASTOIL\ r B-3 BIG OlEECHYDRO 220kV SYSTE.~ TOTAL GENERATION 1000 WI Soutla6rn California Edison 103
PAGE 112
APPENDIX C EXPANDING TRANSMISSION CAPABILITY: HVDC TERMINAL EXPANSION PROJECT nc ISi-mile Hiah Voltaae Direct Current (HVDC) line Crom Celilo, in Oreaon, to Sylmar, ill Southern CaliCornia (see Fiaure C-1) ii one of the most important means oC brinaina low-cost power Crom the Pacific Northwest to CaliCornia includina Southern California Edison Company (SCE). At present the capacity or this line is 2000 NW, but the limitation is not i.D the line itself but in the terminals. ne line itself would be able to carry 3100 MW based on its thermal capacity. The terminals or the line convert the power it carries from AC to DC at the sendina end, and Crom DC back to AC at the receivina end. Adjustment or the controls permit the sendina and receivina ends to be replaced, thus revenina the sense or the power now. HVDC lines are different in function and economic characteristics Crom hiah voltaic AC lines in several important ways: o ne power carried is controlled at the terminals and is not directly affected by conditions on the AC parts or the syste_m. o Because the now on the HVDC line is controllable, an increase in its capacity directly increases the transmission c:apacity of the system as a whole by the same amounL o The terminals or an HVDC line represent a much larger fraction of the total cost than do the terminals or an AC line. In the case or the Celilo-Sylmar line, the capacity or the line wu increased by 1100 MW by addina DC terminal equipment (see Fiaure C-2). This brings the terminal capacity to match the line capacity, increasina the line capacity from 2000 MW to 3100 MW. APPENDIX C Cl
PAGE 113
FIGUllE CI H VD C EXP AN s ION PACIFIC NORTHWEST SOUTHWEST INlERTIE LEGEND mm11 *" ,.,,,,,,, flltt ... 0 ANITWN APPENDIX C alaO,a,DC r Cl
PAGE 114
> ... ... "' a )< n n w PICURE C-2 HVDC Expansion Celllo --,r 1.,.1 Terminal I : Proposed Capablilty of 2,000 MW ~-------.: 1,100 MW Addition In 1985 851 MIies Terminal Capability of 2,000 MW In 1985 Line Capablllty Is 3,100 amps Now using only 2,000 amps ......... Proposed I : 1,100 MW Addition .... ., __ .,,. __ Sylmar
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APPENDIX D EXPANDING TRANSMISSION CAPABILITY: USE OF PHASE SHIFTERS IAPPIOPbY AC the wscc $YJtcm The WSCC transmission system. taken u a whole, bu the 1encral shape or aa clon1ated doualunat includi111 l western section or lines joi11in1 Orcaon and California. and an. cutern scetlon runnin1 1encrally Crom Montana to Arizona; these sectiou are joined. and the doa1hn11t completed. by traumission in the Northwest aad ia Southern California ArizonL Fiaure D-1 shows a simplified view or the WSCC do111bnut. L99p EAWJ Bccause or the 1bapc or the trammiuion system and or the laws or electricity, wbeacver power b MIit Crom oae part or th& doupnut to 111otber, the Clow is split two ways; some 10 clockwise. and some couterclockwisc. The proportion 1oi111 ach way depeadl oa the relative impedance or the two paths. This impedance may be thoaaht or u an electrical len1t11. which depends on the actual lenath and the voltaic or the path (a mile or .500 kV line will have approximately one fifth the impedance or a mile or 230 kV line). For example, iC 1000 MW or power is sent Crom the Monca11a-Wyomin1 ar to the Pacific Northwest, only 510 MW or this power will now alon1 the relatively direct co1111terclockwise path. 11 seen in Fi111re D-2. and the remainina 420 MW will Clow clockwise throuah California and aortb tbro111h the western lines. The nows due to simultaneous tnnsactions carried 011 at Uac time will be superimposed o,s each other dependin1 on their amount and dlnctioL For example. a ale lrom the Northwest to California would reduce (or revcnc) the Clow in the west and between the Northwest and Montana-Wyomina. 111d iacreasc the Clow Crom Montana-Wyomina to California on the eastern lineL APPENDIX D D-1
PAGE 116
II \ _,
PAGE 117
APPENDIX D D!
PAGE 118
> .... .... ... ti :-< Clockwise Loop Flow Montana/Wyoming 0 Coal Schedules to the Northweat Schedule: 1000 MW FIGURE D-2
PAGE 119
Ir the Montana-Wyomina to the Northwest transaction used a scheduled or contract path directly joinina the two areas, the, 420 MW flow not usina that path is called a clockwise 91oop now. Appliqtiop or Phu Sbiftea Phase shiCtin1 transformers, commonly called phase shifters, are transformer like devices -which inject a voltaae in a line which Corms part or a transmission loop. ne effect or the phase shifter is to induce power nows in the loop, so that the power nows in the loop are in~eased or decreased. dependin1 on the setting or the transCormers. For example, in the situation shown in Fiaure D-2, phase shifters could induce a counterclockwise Clow or, say, 100 MW which would increase the nows on the scheduled path to 680 MW and reduce the nows on the rest of the loop to 320 MW. The amount or power Clow that is redirected depends on the size, number, and locations or the phase shiCten: and on the impedances or the lines forming the loop. Purpgse or the Phase Shiflet Study ID 1916, a WSCC task Corce performed I study of the effect oC phase shiftina on tr1111Cer capabilities throuahout WSCC. The Western Area Power Administration had plans to install phase shifters on two lines in Western Colorado. the task force studied the errect or installin1 two or four phase shifters in the eastern side or the doughnut. The studies concerned the errect or the phase shifting on clockwise loop nows. Transient stability was the limitina consideration or transfer consideration. Conctusign or the Study The studies indicated that the phase shifters would improve the ability to schedule power Crom Colorado and Utah to the southwest, and they would not reduce the transfer capability between the Northwest and California, but they would have some neaarive errects also. Specifically, the study found: No reduction or NW /CaliCornia transfer capability with two or !our phase shifters !or the conditions studied. In addition, Northwest remedial actions may need APPENDIX D
PAGE 120
to be reviewed. For constant schedulins levels, there will be more reliance I on Northwest aenerator droppina. A reduction in the Arizona/Calitornia East or the River (EOR) transfer capability or O to 300 MW Cor tour phase shiCten and 0-150 MW ror two phase shifters. These reductions depend on the phase shifter anales, the NE/SE actual flow, and schedules between areas. No reduction in either the Utah or western Colorado portions or the NE/SE transfer capability. Armin1 or the Huntin1to11 unit trip scheme (a remedial meuure9) will be required more olten with two phase shitten than with none. The transfer limit in western Wyomina may be reduced up to 30 MW with tour phase shilters. There is no reduction in the transfer limit with two phase sbilten. Other impacts or pbue sbiCters based on the condi tioos studied are as r ollows: IA1ll WSCC losses 10 up u the phase shiCter anales are increased in the direction so u to reduce clockwise loop now throuah Utah/Colorado. Individual area losses may 10 up or down depe11di111 on the redistribution or the nows due to the phase shiCten. In aeneral, two or lour phase shifters can be used to increase schedules by the amount or loop Clow reduction up to the transfer capability of the path. Study resulu indicate two phase shirters can chanae the loadina of the lines Crom Colorado and Utah to the southwest by at least 300 MW and four phase shiCten can chanae this loadina by at least 500 MW Usina two phase shitters in Colorado to redirect loop flow of C of the Colorado lines could cause a reduction in Utah's scheduling capability to the south. Reductions in transfer capability miaht be offset by an increased ability to carry scheduled power across a boundary. For example, assuming operation or the four phase shifters reduced EOR capability by the maximum noted above, APPENDIX D
PAGE 121
300 MW, studies indicate at the phase shifters maximum anales the clockwise loop now across the EOR. would also be reduced by approximately 500 MW. nis would result in a net increase or approximately 200 MW in the system's ability to carry asbcdglgd power across the EOR. path. APPENDIX D 1).6
PAGE 122
APPENDIX E EXPANDING TR~SMISSION CAPABILITY: ALTER.NATIVES TO SECOND PALO VER.DE DEVERS SOO KV LINE A recent study by SCE considered a number or ways to increase import capability Crom ArizoDL The method or the study was to compare a number or alternatives to the bue project. which was to build a second 500-kV line Crom Palo Verde, Arizona to Devers, California. -Eipt alternatives were considered. Their nature, and the conclusions reached about them, were the Collowina: I. Loop Clow corrective measures: a 1000 MV A phue shiftina project at Vincent Substation 2. Measures to prevent subsynchronous resonance (SSR.) while increasing series compensators 011 the lines between Arizona and California. 3. l11terconnectioa with the -SOuthwcst Powerline 4. Usina available capacity on the existina Palo Verde-Devers line (now being used ror cost-cCCective short-term transactions with Southwest utilities) 5. Increasing toad management and conservation 6. Increasing the implementation of minimum-load corrective measures 7. Converting the existing Palo Verde-Devers line to 165 kV AC I. Converting the existing Palo Verde-Devers line to 500 kV DC or the eiaht alternatives, rour (Nos. 5-1) were determined to be unreasible: Table E-1 gives the reasons. The capital costs and associated transCer benefits Cor strategies identified as being Ceasible arc summarized in Table E-2. In addition, APPENDIX E El
PAGE 123
a aumber or mixed stnteaies i11volvin1 two or the feasible alternatives were evaluated, with raalts shown in Table E-3. The study concluded that the mhed strateay or increasina series compensation ud intercouecti111 with the Southwest Powerline wu the best or the alternatives couidered. However, it was still round inferior to the proposed DevenPalo Verde project 011 the buis or Increased Transfer Capability Cost per kW oC Increase Transfer Capability Environmental Impact APPENDIX E PexeaP,v, Z 1200 MW S206/kW Deven P.A. #2 E-2 Mixed Strateay Alternative 700 MW S509/kW ValleyMiauel line (shorter, but wone impact)
PAGE 124
' II Ill
PAGE 125
> .,. .. "' t, ... TADLB E-1 _s_IRATEGIESJDEH.IIEIED AS NOT FEASIBLE_ filllATEGY REASON FOO DESlr-.NATIQN AS NOT FEASIOLf CONYE0TING OEVEnS-PALO VEOIE II 1 TO 7651 T DE lPGllADED TO 7651<\J; IT WOULD I-IAVE TO DE AEDUIL T" AEQUIAING A TWO YEM OUTAGE ':' CONVE0TING DEVEAS-PALO VEAIE #1 TO 500KV DC COST OF A 2500MW CONVERSION (ADDING 1300MW CF TRANSMISSION CAPACITY) \IIOULO DE $747 .5 MILLION. (SE TADLE 10-10) w INCnEASING LOAD ~t-'l:NT #11 CDNSEAVATION ~ASUlES INCAEASIN IM1LEMENT /\TION Of MINM.M LOAD ConnECTIVE M"":ASUlES INCREASING LOAD ~fvlENT ANl CONSERVATl'-1 IS NOT COST-EFFECTIVE WITHOUT PflOPOSED PAO.ECT. MINI~ LOAD COflRECTIONS WILL NOT ltOlEASE SClJTlIWEST ECONCMY EtRGY PU\ClIASES
PAGE 126
> .. .. ... >< ... 'l'ADLB E-2 MIXED._s_IBAIEG_Y_ALJRNAil~E EEASIDLE Sl])AIEGIES TllANSMISSION BENEFIT (MW) INCfll:ASEO FIRM USE Of filOAlEGY CAPI\OltlTY EXISTING CH-ACITY LOOP FLOW 127 COAAECTIYE MEI\SlffS ssn COAAECTIVE ~ES 400 WITH SERIES COM> INTEllCONNECTINO WITH CAPITAL COST (SEE NllE 1) Ml.I .IQN $/KW 60.3 (SEE tlllE 2) 117.8 475 295 f SOUJHWEST POWERLIN< 200 (SEI! tGlE 3) 230.2 1191 USING AVAILABLE CAPACITY CN DEVERS-PALO VEADE # I NOTES 321 I. COSTS CF LOST POWER ~CHASE orronTLt-alTIES ON EXISTING TRANSMISSION CN>ACITY Nlf NOJ 11-CLUlED IN TIESE ESTIMATES. 2. COSTS ANl nEQUIAEO LEVELS Of AIDITIONAL VOLTAGE SlFPCllT HAVE NOT DEEN DETfOMltEO. 3. SAN DIEGO GAS I ELECTRIC INJICATES NO ADDITIONAL CAPACITY IS AVJ\ILAOLE ON SOUTHWEST POWEOLN
PAGE 127
> .,. .,. tj )< M "' VI TAPJe 1-3 MIKED STRATEGY AL TERNATIVE-DENEFITS AND COSTS INCA[ASCD IAANSflR CAPABILIIY INCRfASCO rlRH USE Of EXISIINO lRANSf(R CAPABllllY 111 a-Sa ~IRAIUll 321 127 illlAllOICi I. LOOP rtow C0NIROLS 160.3 2. SSA CONIROLS SEAICS cot1P. 3. 11[ 10 s.w. POW(RUNIC 1. USE AYAllAllE D-PY I CAPY. TRANSt11SSION OCNCFITS (t1W) 100 321 DMICOlll 2&1 200 321 :i IIIA I COi[~ 3&1 CAPIIAL COST HILLION S S 117.8 1238.2 700 ~IRAILOl[S. 2&3 1117.8 238.2 I0IAl 160.3 I 117.8 1231.2 ll56.o HOIC: IIICSC COSIS PO NOi INCI.UD[ lOSf OPPORlUNIIY COSIS OH CXISIINO IRANSHISSION CAPACIIY.
PAGE 128
APPENDIX F EXPANDING TRANSMISSION CAPABILITY: R.APID ADJUSTMENT OF NETWORK IMPEDANCE As was discussed in Section ID. electric power nows divide alona parallel paths in revme ratio to the impedance celectrical len1th8) or the paths. The Bonneville Power Administration hu studied a proposed technique for increasin1 power transfer limits on power systems. contemplatin1 its application to the Pacific Northwest Southwest 500 kV AC huerties. ne technique is called 9R.apid Adjustment or Network Impedance (RANI): Jt has the potential to improve AC power transmission practice in terms or increue in transter capability, better transient and dynamic stability performance, improved dampina or unwanted oscillations. control or power on transmission lines to aet optimal powernow conditions and to minimize unscheduled powernows, and reduction in transmission lines. RANI would be used OD Iona transmission lines which already have a substantial amount or series capacitor compensation. Series capaciton are devices installed OD tnnaniaion lines which reduce their apparent impedance and make them behave u throap they were much shorter. It would make it possible to chanae the errective impedance or the line, based on automatic controls, very rapidly, presumably in a small Craction or a second. R.ANI consists or a reactor (a device which increases the errective impedance or a line) which is controlled by thyristors (an industrial electronics device which permits stoppina and startina currents at precisely timed intervals). The thyristors control the fraction or the time that the reactor carries current, and thereby control the eCCcct or the reactor, which in turn controls the errective impedance or the line to which it is connected. The thyristors are controlled Crom automatic sianals indicatina the line impedance that is wanted. APPENDIX F Fl
PAGE 129
ne study indicated that the RAtn device would iacreue transfer limits by coatrollia1 loop nows aad also help i11 dampin1 oscillations that have interfered with WSCC traasmiaioa op:cration ill the past. .,, APPENDXX F F
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CAii lTUDID o, TRANllIION IOI ILINEICI Prwated to die Oft1ce of TecluaOIOff MMIINA.t U.S. Coasna Br. Clm. ScJaalts A Allociata. Ille. 1901 Morda Port Myer Dri Salte 503 Arllaatoa, Viqiaja 22209 (703) Ml.-W FAX: 703/141"49 NOYalber 30, 1911
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PRIFACE At die nqaat or die ornce or TecllllolOff Allcament (OTA) or the Uait.cl Slates Coaana. Clm, ScJaaltz & Aaociata, Ille. (CSA) hu pedonllld two cue Shditl illatratia1 two cypa or proble aad solutions 111DCiatlld wida tra-iaioa bottlaecb. OTA_..... two c:ua rroa a Ult or poteatial cues provided by CSA. 1'11111 were Cul 1: Cul 2: lmpordas Pow From Cuacla to New Eapaad (na ....._ D Project') Tnftlfflillkrl to Deliv Low-co.t Power to II Puo Eltctric Compuy n.. CUii were lected becaw die, illutratecl specific tran1miaioa bocdaeca ,rdy r&Cld by die U electric power iadutrJ. nae bait ot tu 1111d caae troa .._.. ia die public domaia. altlloaall ...._. lad1111r7 apouapenolll ....atec1 tor clarificatiom aad additional illloraadoa. Neitller die OT A. or CSA specifically eadona the sohatiou tllal..,. cJaolll. Nor doll eidNr o,pniatioD o1aim dlat these soccilic .. a1mpla an repratad or otber dtuadom in the United States.
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CAIi sniff NUIIIIR 1 Ofl'lce oC Tec:IUlololJ AIIIHIMDt U-1. CoDlftll Clm, Sclaaltz & Aaoc:iata. lac. 1901 NortJa Fort Myer Drive Salte 503 Arllqtoa. Viqiaia 22209 (703) 141-9644 FAX: 703/klM9 NOYemlNr 30, 1911
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CAla l1'UDY NUll8IR 1 IFOHIM PCMiR MOIi CNIADA TO N8W INGUND TAIILI! 01' CONTINTS ~y .......... . . . . . . . . . I TRB PROBLEM 2 '\ 12 IEND'ffl OP THE PROPOSED SOLUTION 15 COSIS AND NET IENEPITS OP THE PROPOSED SOLUTION 17 INTEIUlEGIONAL IMPACT OF BYDR0-QUDEC TO NEPOOL TllANSPEllS 21 BcollOmic CollllqllellCel of Tralllf'er Lilllitatiou . 15 CONCLUSION .. .. 26
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CU. Stady No. 1 CAIi STUDY NUll8l!R 1 .. CR,ING POW& MOIi CANADA TO NIW ENGLAND SIJMIA&Y TIN aftilabWtJ of low-oaat laydro power ill Quebec Province 111d the relatively laip COit.i ol power iD New EDalud mate die importation of power Crom Quebec to New EaalUd ecollOlllicaUy attractie. A BipVoltap DC couection is aeedcd bccaau the Bydro-Qabeo s11tca ii. aot syacJaroaized wida tile US-C.ada Eutenl 1Dterco11nectioa. TIie "Pllall Jr aar---t bltw ... Bydro-Qubec ucl die New Eaaiand Power Pool (NEPOOL) calll t die laport of a macll 2000 MW or power. ID order to implemat CIiia alfN ... t. die capacity ot die aiada1 DC couection w to be iac:reued. becaue die PJIIIDC de capacity ii lilllitad to 80 MW. la addldoa. tu 345-kV A-C tranmiaioa ,,_ ia New laaJud ... to be apaaded to carry die addidoaal power to cntral and IOlldNn New E"llad. TIN iacnuld 1IIIPOl1,I flOIII Clad1 woald bft aa Impact oa die operation or OtMr repoll1I 1t nnltia1 ia a NCOBd tnnmlai limitadoa. Under certain coaclidolll, die Canadfa 1IIIPOl1,I -be ratrictld iD order to avoid potential tn-iai problam iD tile MiclAdutic area aad, perlalps later, in New York State. n. iaportl of Qaebec power iato New EDIIUd are ati-ted to produce capacity aacl ...., YUIii to New Eaataact witla a praat valu or Sl,149 million over the period 1990 to 1999. ne total capital COit to New EDal&Dd atilitia or importia1 this --.,, npn1atin1 die coa or "'8miaioa appada ud relocatiou ud new facilities, all ia die Uaited Stat11, Le.. S547 mi11ion. ne prcsat worth or usociatcd revenue nqairematl is $90 I millloa. Hydro Quebec, the Canadian utility that is sell.ill1 the cner1y, will pay for the NCl1liml apusion or Cuadiu racilitia. nae consilt or acceleratia1 the b11ildi111 or, ,...,.tioa Cacilltia hi the Jama Bay area or northern Quebec province acceleratina the apauioa or the traumiaioa system ill Quebec, 111d bllildilla additional AC-to-DC coaenio tacilidct. C r ....... as .. \111d11u1 r.. I
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CUI ShdJ No. 1 TBB Pll0111BN 111a aortlaaltenl Uaitld Sta an Cacia1 s1aorta1a or power raomca. and PMi1Hy ol 1ow-CGlt ow. ia tlae aat r.,, yean. n.r. are. laowever. ample raoarca of nladwly 1ow-CGlt power ia CaaedL n. electric: traaniai" s,uema or Quebec ud Nffl Eallaad operate -s,antely ud c:uaot be linked ucept by lup-volta1e D-C (HVDC) d& Table 1 slaows die peat load ud tJae comooaats of 1eaeratill1 capacity expected to be ia llffice ia 1990. ucl auul capac;ic, maqiu ror Nffl Enpaad alld aeipboria1 anu. nae. anu an slaowa ia Flpn 1. Table 1 slaows tlaat New EllaJud will UYI reladelJ low paeradoa rlllff aaraiu ia 1990. iadicatill1 tlaat addidoaal capacity ill be __. .. IOOII alter to ten addidaal load powdl. It allo slaows tut New :EaaJud will sdl1 llaw a pudnlarly Mp proportioa or oil-rued paeratioa. wluc:Ja procl11ca llip COIC ... .,. TIie caa1 1111d tor awratioll la Nffl Eaalud ii reladYelJ upemive became ot CM call ot ltl ,..nspar1adoa ad die Mid to bull low-nlplav r11111 ror cmviroamcntal Ne-. AD tlalll faclOrl iadicate New Eallud'I INled tor acldidoaal capacity and ... ., nao--. preferably at a lower wt dlu tlaat obtained rrom New EaaJud oil or caa1 ..... tioa. n. Cendi ,ro,,iw ot Qatbec U1 .,_., 1arp llydro-power rao11rca. n, JUIII Bay ana ia tte Nortll. ia putialar. U1 bea clcveloped ia uticipation or a lfOWUII Med tor electric power. Byclro-Qubec ii die province's maia electric: adlity ud deft10I* of electric power. SollN or Qablc's llyclro power exceeds its pracat ads. ud ii aftilable at a lower CCIII dlu dNnDa1 power la die aortheut Uaitod Stata, even whca tu wt ot tnnmiaion trm tu dlltlat pneratioa sita to New Ellalud ii iac:l11dcd. n. ProYince of Quebec and Byclro-QMbec uve made it a policy to export power to the Uaited Stata at prolitable rata. u loq u th .. exports do not interf'ere with iadastrial cleYtlopaat ol die proYillce and an witlaia tJae ratrictiou imposed by the Canadiaa adoaal penuaat. Gu ....._._ laud a,-. 2
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I 1 ,~ 51 r!CCU cc i .:i I -I !!ii. 1 c c55c~ cc -=. I ., .: = ---5 -; I I I 111::: i :;c ~c .p p 111:. i I ..... -. ia;;, i i -" I a I t ii I \!;l~, ;: !' 1~c~c~ ~-J i-..: _., ___ i I p p l i ... I I 1 I i~ltl u I 1cc~~c ~c I iti "i .:p I I -p p -. ". I -I I -r I I -l~~-~-{' !~~etc 5c ] p,_,__p I ixi i I PPP -I I I ~=! ~I u ac~c~c ~c J I I ,___ .. ; .... -1 I I .. -J 11 a _I J I 11111111 I I l111llu J 3
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wC 1'i9UJ: 1 Alfec:tac! lec;iou r 127
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Cul Sbldy No. l TIie New York Power Pool (NYPP). wida tJae New York Power A11daority, operates dN "'9-itsion 1,1te111 la New York State. New York atilitia import .111bltutia1 qaudda or power from Oatario, rroaa die Midw..c (Eut Catral Area llcliability Coordlaadoa A11mat [EC.UJ naioa~ aacl rrom Hyclro-Qaebec. n. .....,lftlliaNcw J--,-WU,lud latacouectioa (PJM) repoa coen most or all of .....,,...._ New Jena,, Delaware, Muylud 111d tile District or ColambiL 1 .. reaioa llal mbaudal coal-banill1 aaeratioa. but die eutern anu still illclllde a aood deal or oil ucl ....,-ind paeradoa. Colllequady tllen arc sabltutial COit illcadva to tnamit coal-teaaated power rrom the waterD PJM area ud tile BCAJl npoa to tile IUtenl put ol PJM. Power trom aaclar souca, wllicJl Jau the IOWtlC iacnmntal prodacdoa caac ot all acept for hydro power, ii normally aot iatarchaapd; it ii aud by owaia1 ,,,w to NrYe tlleir owa loacll. n. tn-wioa .,.._ ol the ftrioa anaa an coaaected witll each other ia ordG' to permit die iatacllaa .. of power tor ICOIIOIDY ud rellabWcy. Hyclro-Qubec opera tu tw11011Diaioa 1y1ta1 ia tile proYillce, bat dua system ii aot opentad ia ayachroaiaa with tllat ol die Eutffll latercoaaectfoa 1 wlaicb iaclada all i .. Mipbon. Plpn 2 alaowl ia limplllied Corm die laipat volta1e lilla (765 kV, ,00 kV, UICI 345 kV) aacl die IIVDC till wh.icla form tile backbone or tile cransmiaioa 171ta11 or Bydro-Qaebec ud ot tile areu IIIC-' dinctly attected by its exports. Not llaowa an uclerlJiDI tnamiaioa Uw operada1 at 230 kV ud lower voltaPL ne 345-kV, 500-kV, 111d 1,s-tV llaa npraeat die broad avcnaa or iatcr-reaioaal power iacercbaap. "n.. ........ II et I hB1 If ........ .,.._ fll 1M .. NUllltell ........ c..da wl _,.._._.,.M,ut ..... ._ca--_.__._,T-. n.,111 ... 1h1tr111U, ws:dwilll ..... odw *' qi& a ....... .t AC tr I hn ..... IUI ....... e,a .,... la .,,,.,.., ...... ., Czn ......_ ~dI, 1M.
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Cue Stady No. I At ,r t. die Byclro-Qabec: 1J1t11D ii COIUlected to die rat or die Eastern latarcollN:doa t11roaaJa n BVDC da: J,optJgp aa .... Blpaate Del Caatom Mlldawub lel ll1ffl" C&amn 1,000 MW 200 MW &OMW JSO MW ,,o MY( 2.,S90MW nm locado are uowa la Flpn 3. Eac1a ot di ... tia ii adjustable to transmit any aaoat ol power ap to itl capacity. It llaoald be aoted tJaat die Proiace or New Bralwict. alib Byclro-Qaabec. eperaca 1a syac:Jaroailm witJa New Eaalud. nereore die latercoauc:doal betwND Qublc ud New ln1111Wick mat be BVDC. or die two PrllDt BVDC COIIMCtiOIII bit-Qublc and tile NEPOOL system. w ii a de at Blppea la Vermoat, wlaicll npplia 11p to 200 MW to tile state or Vmt u4 ... Vaoat dllti& n. otller ii die BVDC tnnsndaioa aaodated with .dle ..... lprojlc:t. n. Pllul I project colllilll or a Cormal aanemat tor tile le by Hydro-Quebec to NBPOOL or 33 lllillloa MWla or sarpl llydnHJcctric acrn over u I I-year period 1Mlii ia 198', ud ror proylclia1 tM aei:111111 tnain,oL nil is an enern parcJaw-&ll'Nmat. wlaic:Ja doll DOt panatee that NEPOOL will obtain uy specified Ullftllt ol power at die dm ol its _. cridcal aadl. However, NEPOOL does treat tlail lfmat u nliable CIIOIIP to jadly aot bailcHa1 600 MW or capacicy2 \ I addldoa. the PlaaN I a.,..._c provides tho opportuity tor ner1y ba11Jdn1, i.e. die cleliery or ,..., Crom HQ to NIPOOL wlloa HQ Jau 111rplu IDfflY, to be ntuaed wlaeD NEPOOL loadl are lower ud HQ loacll are bi1Ja. ...... bl' 1/'ls* Qa1t11 z kY Ta I In LIM 1Mn11ni8111 ,._ 11, n..a ._,b n ,,..a ........ t ,,. VI D,, t "....,, I ........ :a,nrt I I ,et ... om..,,_.'""" AuCUII lllr, a 3 .Ills .... d I 'f.1 ) f I 1 I Min ........ lp1 -rlt, VA mil. C 1 ....,,_ A1111fslH, 6
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-.. .. 7 ... ... ,.,,,a...--, .. ~-
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(.) 3 en < 35 1.wc= It %Cl 09 =2 tJ'J < 2 -~ t5 2. % w z en .Z. C, .; 0) .. .,.: 10 > .0 N I = ""' 0 a: D 0 0 w .. > I-CO za:,_ .I-::t -CD i I "' (.) ,... I e = la C 0 < 0 s ... (.) % ..J a 12 > :c a, -:c I
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CU. Stady No. l na. Pbw I iDlpor1I. nuuua1 to a mzima of 80 MW or power. are taken Crom die Byclro-Qublc 7'5-kV.syatGID at DII Cutoa (SN Fipre 4). COnYerted to: 450-kV DC dlaN. 111d lnUlllitted "" a 107-mile IIVDC llae darollp nordleutern Vermont to Coaat..a. New Rllapahin. At tlUI poiat, die power II converted back to AC ror tnemieioll to die YUiou loadl ia New Eaalud Oftl' NEPOOL'1 kS-tV ud loworYOllql tnNffliaicna lia& n. capacity of tlae Del Caatou aad Comerford converten ii 80 MW eacJa. ne capacity of tile IIV1)C tnnsminfon llao itself' ii sufficient ror it to cur, die power nows of up to 2000 MW wbicla will implemat the Phase II project. TIie term % 450-kV IIVDC' daotll a tnnmiai411 lia coaisti111 or two conductor wires. ou cur,iq 450 kV paaidw wida rPICt to poacl. ud die otlaor 450 kV aeptivo. IIVDC del are nq1lired be:Cwta tJao HQ ud NEPOOL 1J1tem1 bocaw tbae two syste1111 cuaoc be operated bl 1J11CU01U1111 tor teehaical nuou. AC tia are Caliblc only ...... .,... tlaat operata ia syacJarolUI& TIN ,._ I project. u die .... illlplJa. wu conceived u die Cint step iD iacnuiaa power truaf'en rroa Qaebeo to New EAaled. Uader it. the BQ-NEJ'OOL tl'IIIIIGI an lilllitad by: Lack of aa ap1a1at to tralllf er mon power. n. limited capacity or tJao aistia1 ACDC converters at Des Cutom aad Comlrford. Lbniiatiou ia die AC QlteDII wbicla llriD1 power Crom tbe pncratioa to Del Cutou. ud from Comerford to tile vario111 load ccaten in New Eaalud (catered ia eatma MamcJuasem). lacnued impora cu obviouly aot be c:anied oat oYer the ezistia1 Phase I system. a, ......... ..:\mltn,r.. 9
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Figure 4 PHASE I HVDC INTERCCHECTJCN Power 1'1"011 Hydro-Quabec: 7&5-kY AC syst M>eSS. Des Cczratuus \ \ Comerford I ...... -~.... ,.. 133 10
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CU. Shady No. I n. Pllw I project tJl'lumini nrren Crom uodaer drawback: with tho present uraqemat. aboat 15 percat or die pow1r tnllllerred at peat load times is diaipated ia tn-ieion l:aL Tlaia ii u umally Jaip amoui. aad reduces the ecoaomic badltl of tM ti& It wowlcl ...,.... tll&C die AC QStall OIi boela sides wtre apuded oaa, to die atac aecnn,y to au die Pllw I project Yiable. la the apectadoa or -kiI aore acaliYe UIIPl'OYemlatl ia couectioa wiela die Plaue D doYolopmat. n. N..., laslud adllda Ila sm,a11d to elimiaace die bottloaeck to tho sale of addidollal low-colC aaern to NEPOOL Crom Hydro-Quebec by lnaildill1 the m-inioa tacilida nquind to accompliala dais ale. nil propmcd trumtioa is COlllaOIIIJ nfened to u ,... D. le PfOYida tor a total aclditioaal euru parcllasc or 70 aUJioa MWla '"' a tlll-,-r period. cammdy ICJledllled to bqia ill 1990, ud tor 1NMl die uc II ry l"lneheloe facillda tor its deliery. BJdro-Qaebec ii .....,..u,._ f ... blfMi11 tile aed111 or moatlaly dcllffries of tu 7 .Ulloa MWII ol IIMlqJ "' eacla coatrac:t year, wtaUe obm ,ua, coatrac:tul aoadaly wiaim11111 aad i lliaitL Ia aaeral, NEPOOL is aatided. to schedule cleliftria ia uy llov ap to die 2000 MY capacity or die d& There are lilllicatioas on dN rate of chan .. ol delieria Crom ou laov to die ant. aad Rydro-Qubec may iatar,apC clelierill dvill1 limited periods or time. nia mates tho Phuc D aareemeat uidaer a completely iatamapdble acrv pvcJwe, ncll u Pbue I, aor a firm capacity pmcllal armac, wlaicJa woud paraata tile availability or spccitic: deliveries when req1lind by tile lna,er, 1abject oaly to forced ocaaes ud tnnsmiaioa limicatiom. In Yia-# or tile cam ud practical apectatiou or tho Phase n aareement. NEPOOL COllliclen tlaat it repraats a reliable capacity sorce or 900 MW. a.a.d that the combiacd Plwe I ud Pllw D a.,.._.11 cu be treated u a replacement tor UOO MW or addldoaal iutalled capacicy1 nil. ma111 that NEPOOL is contideat tlaat durilla its peat lo.de ud other times or critical need, Hydro-Quebec will supply at leut 900 MW .... _..,_.Tl r r :a-.c..,Amzf tlehppf 11C1or.o.,. ..... ..... af111'11N T .. Y .. ,.._ IIN-1111, M llllt Mz v ...., ...._ S1t:1ac Ceactl, .., ir UM, v ..... I.,... .. Cr ......_ II .A111dzt11, 1M. .. ,,. II
PAGE 145
C... Stlld1 No. 1 ol power 1111cler die Pllul D ll'mat, at a reliability lnel compatible with that or -... NEPOOL power n1DUC1L n. ,rol,lal. or die tnnmfsioa lilllitadoaa oa Plaue D importa is bem1 resolved "7 M!w1 boda RVDC ad AC coapoaaaa. la Cinda, die BVDC compoaats coasist ol a ... 700-n BVDC Dae rroa a,c11.-oa Jama lay to Da Cutou oa a aew ripe-of-way. ud aa AC-DC tenlliaa1 (coacrter) at Radflloa rated at 2000 MW. There will allO be a DCAC coa"'10r at Nicolet, acar Moatnel. but dlil is ollly or iatcnaal sipif'icuce to Bydro-Q1ulblc. la die Uaited Stata. dlere will be a 133-mile extcasioa ot die BVDC 1iu rroa Comorf'ord to aa llOO MW BVl>C termiu1 at Sudy Poad ia MewdallllUL TJaia Uae ia die Uaftad Stata ii eadrely oa czistia1 oce11pied ripta-ol way. acept for a sllort amat wlaicJa is oa aiatf111 tility property. The locatioa ot. dlell facilidll an slaowa ia Fipre 5. la addidoa. tile NEPOOL AC system Ila to be apeacled ia order to alllorb die Plaase D power aad distribute it to die YUiou laacl eaten ia N.,. Eqld. n. A-C apusioa co .... of comtnactia1 two aew 345-kV AC "-faioa\ U... witla a coabiud lasda of 51.1 mila, aloa1 wstia1 treeheknt dptl-Ol-way. 0.. will Im from die Sucly Poad sabltldoa to Millbury lllladoa la MillbuJ. Mewdl~ ud die odaer rroa Sudy Poad to tu. Wat Medway ..... doa la Midway, Ylwcllwns. w die Dode Jsllnd border. A1lo, mbstaatial -beladoa niiatorcemat1 en nqafnd ,t die Sucly Poacl. Mlllbuy, ud West Medway ..... do ... u well u dis IDOYial or .... low-YOlta .. AC tnaiaiqa OD the Sandy Poiat to Mllllnuy ript-ol-way. ud other miscellanena wort. M will be dileuNd later. die 1Ctnata1a to New EaaJaad from this proposed IOladoa coald be otr by iaCNlllld CGICI aad tnnnnitlioa coastraints iD neipboria1 npoaa. nae dflCtl adaiiM till importuce or couidmll1 the impact or cha111a ia uy ou repoa oa botll tllat repoa aad odaa repOIII dlat _, be aCCected. The costs ud baellta or die propoud Pllw D project will rust be clilcuaed Crom the perspective oC New EaaJaad aloae. Sableq-tlJ. tile adYena impactS or thil project on nei1hboria1 mttm will be dacribld. ud the UIOC:iated COltl and operatin1 constraints will be &c:uNcL C ........ 1, ......... ... ,.. 135 12
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... < Figure S' PHASE I HVDC INTERCCNECTIQ\4S 1990 ., \ QUEBEC Phase I :t 450 KV DC Line PENNSYLVANIA NEW YORK \ \ \ 700 Mf \ \ \ N.H. CONN. Comerford \tHfi -126 13
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CUI ShdJ No. 1 TM price at wMcla tu --u ii to be Id ia eacJa year ii a specifjed Cractioa ot NUOOL.'I a..a11 tOllil t..i (caal. oil. aaaanl pa} COit ia die prnio111 year. nil fncdaa lc _. dllriaa die nnc nw ,-,. or t1ae c:oatraet;, ad tAdariaatlNaadfiwyan. MIGldla1 to dae Plaa111mroe ... ta1 Impact Smtemat (FEIS) tor tllc Plaw D pro,ilct pnpanc1 bJ Illa Bcoaoaic ReplatorJ Admilliltracioa or die U.S. Deputmcac or Bwu": 9tlle ,ropa 11d acdaa dloald pnmcle IOOIIOIIUc baclla to CM New Eaalud ,... la *-ways (l) rldllcdoa ia rut CGltl drmllp redllCtioa ia die 1--,t ot oil wd ..... ta ... u; (2) a redacdoa ot 900 MW ia ..., ......_ ...,11,,..... aaiataia die cltlind leftl or nliabillsy die ND00L ,,_ clariaa die 199Crl; ud (3) a ndacdoa la die tllllaiaal ._ ...,,. .... t"leittill1 electric aau to die load --....... New ......... Sim dlaa aYill11 depad 1NaU1 the can price or oil, die FEIS praatcd the 1Nmd1II ot die Pllue D project calCIIJatld ror a ,._. 11111111pdoa coacmwl1 die ratve ..... ia fOIIII tMI prica. ..... oa tMI cat projecdom dneloped ror NIPOOL by Daca a ... --. Ille.. lffilld ia 111rc1a or 1914. ad ror roar odler altcnad crnds (raaaial tram 6A below to U.. abo die projected bue tread). For the .,._. ,_mpdoe u to tllel CGlt tracll, Illa,, .... wortll or tile .,._. baclits (wlaida do not nn.c tM CGIII of die projla) an calcalated to be MJJUeu oC DglJa 1.4U 407 Z7 '-Is.' ""'*a Q: h I s kY Tn I I a LIM lat n r ti ,._ llt 1lal v11 1.a ...... &, UI D ,rm & rl -.,, l1 II s I I ., I I Is, tt1 om.., hll PNp ..._. 1111', -n t! ........... 'II t I I I 91 n Hr ...... I; I dsld, VA ma. C 1 ...... A111d1&11, Ism. 14
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Cw StadJ No. 2 All npns aboff repn11at die praat wortJa or die iDdicated qautitia oer tho contract period. n., ... PJ 111atad by die appl1cut ror die Praidadal Permit to implomat die Pllw II laporta, Vaaoat m.ctric T .. mieeio-. Compuy. a .... or NEPOOL. ud rlewd ud toad to -..,.u co be reuoa..bJ tu U.S. l>eputmat or Eacru.1 n. l*lltJ am11 r.n.ct die COIi ol iemlli 900 MW or combutioa hlrbiaa ia New 1a1nc1 Coabudoa hll'biw ..,. eouidend to be a nuoablo sccoadbat" .&tenad ... la die ... ol die FEJS: "liaca Pl narbiw Ila" a rclatiely low capical c:oa. are qmctly illltllllcd. ud an int111ect (laerally) tor reliability ,.. .. oaly. Fvtlaermorc, iC die PlaUI D projlctl..,. aot adertaka. Pl tvbiaa an WI ollly central aadoll apacic, 11U01 tllat COllld bl iw1llcl ia tlN nqaind time period. n. talnllatecl p..-baelitl do DOC nllecc die COIII or tu projact. wluch wiU be c:GYSed .... B,clro-QMINc. ol c:oane. allO Nlldltl tl'OIII die P1lue D trulletioL It ii scllial ......, Idell woaJd otMrWill bl .......,.._ 111 POii. beuflt1 colllilt 111C11tially or die price NNlwd tor die IMl1Y IOlcL It ... bla carrec:dy tad. oa _,, occaliou, tlaat tor tru ball to be obtained troa uy llec:bic po._ tw'llnaioa.. mil tramcdoa mat raalt in a pllysical cbaa1e bl die ff.all cUlpatcJa. widl puntioa iacnuld at a lower-caat soarcc, ud decreased at a lliper-cGlt ..,_ Lactia1 tlaia coadidoa. tJaere an 110 real avill11, bat merely a ndlltriblldoa ot caas. Tu Pllw D project c:Jeuly pena dlil tat. Compari111 the Plaue D project widl its altanaatie, ia wucla New Entlaad woald iutall mon combastioa narbiaa.; uder PlaaN D. tun will bl more (low-coa) bydro power p11erated at Jama Bay. &Del laa power paeratad Crom tlaermal 1aeratioa iJa New EaaJud 111d 1111y odlcr locacioa trom wlucll NEPOOL woald Ila parcll1111 daermal 1en1ratioL 'Plul Eaviroamental Impact Statement. op. cit.. p. I -5. C 1 111 ......_ .\and1ea, r.. u
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TIie cl1nct calC to NDOOL ol die ,.._ D tramacdoa colllim or the capital coses. ud opaadq ... ol die tn-feeioe s,aaa ~panaioa reqaired to implcmeat the projlcL TIii capical aa111 wlliell.,. a,, tar die mGIC dpitlcuc. iaclllde oaly thou for flcdllda Wbwcted ia die New laalUd sca111; C1a1di1a transmiai'la com are to be --bJ BJ~bec. TIie capital COICI ror die U.S. put oC die project are estimated at S47 million cloUan. nil reor11m .. 9mad,..,..-atimta tllat an coaidered accante to oaly :t 2ft. Table 2 lllowl die pr1111t wonla of die ma reqainmeaa aaociaced with the but ol ma coa ud witla die two acnme Yalw oC laiper ucl u lower c:al!I. aiq dN ...... baa Cul caa trad. Yuaally, Tabl 2 sJlowl die aet beaclia to New ....... ol die ..._ D projla. n. ut balefia are positive. ruaia1 rroa S723 co Sl,165 wiPioa ill pr11ac wonla ot NYIIIM NN111inmnt1 redac:doL Similar calahdoa. f odla' dlu die ..-mid bul tul tnadl, all allowed some advuca1e or CM ,.._ D projact o..-die pMVbiM a1-..dff. ucapc ror ou very atreme oaalllndoa ol lllllmPdoa laY01Yill1 oil prica aca!sd111 6ft Im dwa the base -pdoa ad. 1c tlMt w d-. ,.._ D capital COltl blia1 more tllla estimated. AD OCMr coaldadolll ot uaapdoas prodace aet baelia rupa1 Crom aearly break..,.. to u mllcJa u 1,527 willioe doUan ill praac wortJa or rnau reqairemcaa. n. CGIII ot dN project to Bydro-Qubec are more dilClc:lllt to evalacc. This ii ._._ Bydro-QNINc couiclan tllac aGIC ot tu 1J1ta1 compoaaa iavolvcd would Jaave ball nilt la UJ CUI oaly a Cew ,-n later. Ia 1916. ic WU atimatld that the Plluc D project nqund die 9La Gruda 19 projlct (1200 MW capacity, with 6,000,000 MWH/ ,-r ol --.,) to be advaaced ia dal Crom a previouly planald year 2000 to 1997. SiJlce m-. Hydro Quebec's load powtk as,eetatioa lau increased.. and the pn,ject may be adnllCld to III earlier date Jct. n. DC line Crom Radilton to Da Caatom is also ... u u aoaalcradoa of a llae wlucla wu oriaiaally planned. bat u 111 AC lia~ for co111b'11Cdoa la 1994. C 16
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i fif .a~ I ii' JI!!! I .. 1 J I I J iii 17
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Cue Stlldy No. 2 A collQNlriloa by Byclro-Qaeb.ec or the present worth or their total costs. Cor iavatmaa aad operatio~ or all aaaation ud tnaaniaion elements affected by the Pllue D project. llaowc Wltlao11t the Plaue D project: Wida the Phase D project Iacr ... dae to Phue II project Cole iacnaes Cor other tnnaninion liaa: COIT CCIP14ilP Dgll1n) 7.24M million z,111 million 633 million 13 millipn 716 lllilllon nae Fillal EavirolUIIODtal Impact Sbltement poiats oat that, in additir to the economic baelita that were couiclend hi mkia1 the estimates shown here. there are otlaer baefita, DOC ,et qaudllcd, that coald be derived Crom the Phase n racilities. Al IIIIIUIIUiZld hi die Fhla1 Eaviroamatal Impact Statements. n.. oppoatuAity ror iacreued eneray bukiaa. whereby NEPOOL mcmben could transmit rdadvely iDcxpeuive ener1y DOrtla to Quebec ud receive eqaa1 amouta or 111er1y durina oa-,.u paiodl wlaa 1aeradon caas in New Eaatand are mllcll lliper. ne buie EaeraJ Bankin1 Aanement was atablished under Phue I. bat the amount or aero ban.ldn1 wu llmitcd to power levels or 690 MW by die capacity or the Pbal I Cac:illtia. Collltnction or the Pbue D facilities woald raile the potential level or aeru banJdn1 to almost 2000 MW. Acldidoal opportuida ror encru hlterchanac. whereby if Ryclro-Qubee laaa additional sarplua of eneray, it could sell the IIU'Plua to New Enaland at a fraction or New E111la11d's avoided rael cost. Iac:nued ability to make emeraeaey tralllf'ers or power to lidler side or the border ror mutual reliability p11rp01CL C11-, ......_ 11 .. \cu llmtn, 1M. 11
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Cue Stllcly No.. 2 INTDUGJONAL JMPACf OP BYDRC>-QUEBEC TO NEPOOL TRANSFERS -r-. larp apected lmpcnu tram Qaebeo iato NEPOOL. New York, and New Bnuwict raile tlN qusdoa or wlaat wollld laappa to die Eutorn Interco1111ection iC the imports from Quebec ,,.. lllddalJ lolt. eidaer from a failure or the Phase II tnnmillion s,stem, or froa a collapae (blackoat) or die Hydro-Quebec system. Hydro Quebec coald be uportiaa u lll1ICJa u 3900 MW at one time throap its various tics into die Eaten lllterco1111ectio11 u--. However, only some 2000 MW or imports cu be lost du to uy continpac:,, became the vario111 system have 11rced 011 some special operatina procedans wllic:Ja an explained iD Appacliz A. Since NEPOOL. NYPP. P JM. ECAR. ud odaer QltOml dlat make P or tJae Eutma Intercoucctioa are all illtercoulCted ud operatiD1 in spclaromm. scriOIII diltarbuccs could b& propapted Crom oae or tJae system to its aeipbon 111d even to more distant systems. 111a Joa or a llu or converter carr,iD1 2,000 MW Crom Quebec to NEPOOL would laave die ame effect u tu loll of a 2,0QO.MW 1aeratill1 llllit ill NEPOOL The laraest ailtiaa ...-adna uitl iD die Hrtlulutlna s71tem1 are rated at 1,300 MW, and the laqat ult 1D New Eaalud ii rated at 1,253 MW. Th111, die loa or die Phase II tn-hli woald raut iD a cliltlanuca macla ~one tJaan the loa or the lariat pnerator oa UJ 1J1te1L SimHrly, a collapu of tJae Hydro-Quebec system could cause tJae llldda loa or all dae imports from Quebec to New York, New Enpand, 111d New B1'11111Wict. except tJae Plwe II importa. totalln1 u macla u 1,900 MW. Wlaa tJae power npply iD New Enalud ii saddcaly reduced by 2000 MW. this loss ii immediately replaced b1 power 1aeratcd iD New En1la11d and in all the ueas COIWICtld witla New Eaalucl. from dae Rocky Moantaim and the Gair Coast to Nova Scotia. Malt of tJail power ii paerated iD ueas to the west or New York State ud PJM, ud pean daraap tJaae on the way to New !Aaland. These lar1e power nows are added to the predominantly eutWard economic power nows in the PJM and NYPP areas wllicla are du to dae eute111 area' purcbua or lower cost power Crom ECAR. ud other mid-watern area. The very Iara combiaatioa or thae eastward power nows throu1h PJM ad NYPP can ca1111 thmaal overlook, voltaic iaadcquacies. and possibly instability. These problcm1 are dilcuaed in Appendix B. c,._, ........ .A.111 lletr, 19
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Cue Shlcly No. 2 Ia rapoue to these co11cerm. a study wu coad11cted by the "MEN Study Committee9, a po11p repnsatill1 PJM. ECAll 111d NPCC. The latter is the Northeast Power Coordiaatia1 Coucil -. repr .... till1 tho New York Power Pool ud NEPOOL The Connnittan Ulfp1M11t wu to stlldJ tho impact or die plaaaod iacnue in imporcs 011 die nliabilitJ ol tho repou it npr11111tec1. iacllldia1 the impact or B1dro-Q11ebcc NEPOOL traufen OD otlaor trulfer capabilitia. Thar reYiow iavatipted both stady aaco-coadltiou, i.& tJa .erect or the loa or tile Cuadiu imporu 011 power nows and voltaps la the rqioa, ud dJIWIUc ualysis9 wlucla coacerned uy threats to system stabilitJ rrom these coatiapacia. Ia both para. die aoal was to determine any llmitatiou OD s,stem ooeratioa wllich woald be necary ia order to maintain adequte system rellabWtJ. Tho rud11110Dtal priaciple ia dcterminill1 these limitations wu that ,,... 011tlido or NEPOOL slloald aot llavo to restrict their trulf'en more severely in co11taaplado11 or tJac loa or Caa1diu importl to New Eaawad tha11 tlaey already do in coatemplatioa oC co11tu11acia ia their own systems. This principle will be illustrated later ia coucctioa with die presentation or the MEN study remits. n. MEN madla coaCirmad that die 011ta1 or tho Phase D tie, which would iatemapt a ffllxlm'UII ol 2,000 MW or puratioa supply to NEPOOL, could cause volta1e problelBI aad OYedoacll oa uaYilJ loaded cimaitl ID PJM ud NYPP. nae errects clcpead oa laow aacll power wu behl1 tramlerred rrom Hydro-Quebec to NEPOOL. and allo oa laow macla power wu bcin1 tralllt'erred eutward ac:raa PJM and NYPP, beCore tJae Pllue D tie 011ta1e. ncretore, they vary Crom one time to aaother. It was round that the pre-coatiapaCJ couditiou 1ovomia1 the errect or Phase II imports on PJM. and NYPP traumiaioa can be dcf"'med uiaa two key variables: Tu "NYJ'P Total Eat Trauten. This is the S1llll or the west-to-cut power nows over 16 tTlaaninfoa Una ud tnasf'ormen that liAt a western and u eutera rqion within the NYPP. The 9Total ECAll to PJM Trauten. nese ue the west-to-east power nows over 19 traasminioa Una and tramCormen coanectin1 the ECAR and PJM systemL ne potential errec:ts or the Phase II imports on the PJM and NYPP systems were analyzed tor peat load tima ud also Cor conditiou tJpical or wbea loads are approximately 75 or peak. ne "7511ft or peat conditions occur more frequently than C:11 rsa, ......_ .\an 11 tu, 1M. 20
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Cue Study No. 2 peak periods. ud cu at tima involve more serious tnnsmiaion problems than the peak period; it la therelon importnt to determine wlaat tnuler llmitadou are needed durina "'7,.. of peak9 coadido-. u well u uder peak loacliaa. IIICNUld power nows aaerally iacnue the risk that a pven co11dn1eacy, 111ch u loa ol a b'ln1mwioa Utae. or or a larp pnerator, would caw overloads, voltaae in1deqacia, or imtability. Therefore, eaeJI area limits its power truslen to the levels at wbicla th .. system railura will aot occ:ar. For uamplc., the ECAR.-to-PJM traasfen mut be limited to 3950 MW uder typical coaclitioas, because with biper trUSf'en c:ertaia oata .. in PJM woald nnlt ia iaadcquata voltaaa within the PJM system. nenton. die buie priaciple or the MEN stady woald require that the loa or the Phase D imooru slaoalcl not caw uacceptablo coaditiou ia PJM wbea die ECAR.-PJM trulf'en are 3950 MW or lea. Jatercoauc:ted atilitia ....,.Uy make it a practice to restrict their 0W11 opcratioas 10 u w to iacnue risk ud apa to their 11cipbon. They do so primarily in recopid or die tact tlaat tlala matul coopendoa ii the Ollly practical way in which the larae latercoaucdoa ol die Nortll Alllaicu coatilumt cu be operated in the 10111 naa. nil ....,a1 attitlldo or coopendoa ii, to some atat, embodied in formal armats ud nala ncll u thoae which aovena 11dllties' membership iD the North AIMricu Electric Reliability coancil (NER.C) and the variou rqioaal reliability councils tlaat mate 11p tJlil o,aaaiution. ne rollowilla qaotadon Crom tbe NER.C Opcratiaa Muaal. whic:ll sea oat basic criteria and nala ror iatercouccted operation, illustrates th.ii approach: -wJaa atablislai111 normal ud emeraeacy trauler limits, the seadi111, iaterYaina, ud rcccivina control areas sllall consider the errect or power now throap their OWD ud other parallel systems or control areas based on matully acceptable reliability criteria. However, the aareemnts ud nala are only the moat formal manifestation or the prevailiaa attltado or utility pluacn, wbo 11ndentaad tbat mutual respect aad couideradoa are the necanry bail Cor obtaiaiaa the benefits or interconnection, matual aailtance in emeraencia, ud economic iaterchaaac. C r n ......_ Arrntat, la&. 21
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Cue SbldJ No. 2 nae MEN stady roud dlat Phase D imports or lea dwl UOO MW do not require PJM or NYPP to ratrict tlaeir power tnlllf'en more snerely tlau they must do tor coadapacill hi dudr owa ,,seem. aad dlat laqer imports, ap to 2000 MW, would atrect PJM ratrictiou bat aot tloN or NYPP. n. MEN tiadiJl11 may be smamarized by the tollowiaa table No Phue U ,, NYPP Total East Traasf'er Limit MW 5600 ECAll to PJM Truster Limit MW laitial ..... u LoadiDI 1500 p Pt lep 5600' 39,o(t) Initial Phase II Loadin1 2000 fl 5600'1 3250<1> (JJ luld OD NYPP hltenal stability limit (tJ luld Oil PJM hltenlal steady-S1atl limit luld oa die steady-ltate impact or the coatia1eacy Joa or the Phase II tie. nil table hldicata dlat. u madoaed aboYC, ;r the Pbue D imports are limited to 1500 MW, tu claalG' oC die loll of die Plwe D de doa aot reqmre PJM or NYPP to restrict their operadoa more tllu di-, wnld beca8N or potatial coatiapada iD their own system. Bowner, with 2000 MW or Pllw D imports, PJM would laave to reatrict their imports rrom ECAJt. mon strictly (3250 MW) tlwa they woald aeed to do in coatempladoa or a coatiapacy ia their s,stem. or rbt seven oltap problems in cue NEPOOL IOlt itl Phue D imports. TIier.Con. the Phase U impons may not be iacreascd to 2000 MW 1Ullea PJM ii iaportia1 3250 MW or las Crom ECAR. n. table slaowa that Plluc D impora ap to 2000 MW do not arrect NYPP's ability to tnlllf'er power bctwca itl westera aad euterD pans. However, NYPP is investi1atin1 ways or iacreuilla their trud'er capability. IC they do so, the Plauc D imports may become a llmitiDa factor, aad woald thca have to be restricted accordiaaly. All altenaative soladoa ((or which DO data are available) woald be to install additioaal traamiaioa Cacilida OD lither tho PJM or, eventually, NYPP systems. The t1Chaical details aad COltl or nch c~1es have Dot baa determined; ud the allocation or aliy COltl would have to be aqotiated amoaa the parties involved. C I ................... lac. 22
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Cul Stllcly No. 2 Bc1NNlllia Ca1paca ot Tnmfar Limitatioa la paaaJ. it woald be IIIGlt adftlltaaeou for NEPOOL to import u much ener1y u poaible to nplace its _. apeuive iDterul soarces. wlucJa an ill heaviest ue duriD1 peak loacl timll aad wlaa Iara amoua or low-coat 1aoratioa ue oat or senice. As wu a,laiecl tarller, the Phue I ud Pllw II contracts provide, basically, ror the sale ot a pYIII amout or aero per year. Row macla or it cu be imported at times when it ii IIIOlt baef1cia1 is limited by tho MW capacity or the HVDC tie. ne additional tl'Uller llmitatiou Curthc ratrict the amout or power that cu be imoorted at cenain d11t1, ud tlau tJacy restrict NEPOOL's abWtJ to optimize the scJacd1111D1 or imports. Som of tlae coatractcd aaeru imports will llave to be taken at tima when they replace cJaaper aeru tllu tlaey woald laave it NEPOOL coald laave schecl111cd them whenever it waated to. nil will raile NEPOOL's total r11e1 COit. nerc is also a sccoadary efrecc liwco die price or die imported power is a pvea Cractioa or NEPOOL's avera1e fuel cost oer die pnio111 ,-r, die iacrcue ill NEPOOL'1 total C11Cl COit (ud therel'ore or its ...... tNI COIi) will iacnul die price daat NEPOOL will llave to pay tor the imported ...., la tile aat year. All admate ol tile elfect or thae cast iDcrcua is not aftilable. WIIJle tlMlre uve baa some couideratiou or what trananissi411 reinf'orccmcnts wo111d be U(:11111'7 to remove ail'bal limitatiou oa tile ECAR.to-PJM ud NYPP Total Eut Traulen. both tllON d to illtenal limitatiou ud tllOIC due to the Canadian im,oru, tlae aact aatun or thae reialorcemats, their COit, and tlae IIDOllllt by which tll lilllitadoa would be relieved an not aY&ilable because studies llave been, ror the IIIGlt put, illformal ud pnlimiaary. ne iDCormal 1eneral comemu amon1 system plauen iD tile rqion sama to be that the COit or illcreasia1 tramt'er capabilities by sabltaatial amouts is likely to ezcced the economic pia producecl by these i11creucs. at the praat COit cW"CerentialL C .................. 23
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Cue Stlldy No. 2 CONCLUSION TIN ...... --., COit badita wida a pr11at wortla or 1,149 million dollan. at u atimted cost ol 941 lllillloa dollan. n-baef'lts will bl ndac:ed soacwbat by dao 11oed to limit die total impora to Im tllu dae f1111 capacity or dao RVDC ties. wbonr,er importi111 more wollld dareata tho reliability or systems in New York State or in the Mid-Atlantic (PJM) area. TIN Plauo D illcreue or power imoorts Crom Quebec to Now ED&lud race daree separate tnnlffliaioa bottlaecb: I. BVDC tics bad to bl iac:nued in order to carry dac power bctwcea the 11111J11cbrollized Byclro-Qaobec ud NEPOOL systems. HVDC tn11aniaio11 lillCI wore ataded 700 mila iD Quebec ud 133 miles ill New EaaJud. 2. la order to ablorb tlMI addidoal power iato dao NEPOOL systm. aclditioul 345-kV AC tnnmiaioll had to be atondcd SI.I mila iD New EnaJud. 3. 'l'llla ECAllto-PJM tnulcn arc at or near dacir sale limits, tbc Canadian importl mut 1M ratric:ted below their muimam capacity ia order 11ot to bnpaa additional ratricdoa OD the ECAll ud PJM. Similar restrictions related to NYPP west-to-eat traaf'crs may become crrcctive i11 the ratare. (' I ......... .\ar11I la&, 24
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Cue SC11dy No. 2 APPENDIX A OpwallltU lladee to Reduce AamD of Conanger-.cl Wida WI poaibWCJ or u mllCJI u 3,00 MW beiaa imported illto New York, New Eapud ud New Bnuwict Crom Qaebec tlaroap die ftriou DC tics shown ill Fiaure J. special proyiliou 111111t be made blcaw a c:ollapN or die Hydro-Quebec tna1miaio11 ..,._ wcnald renlt ill WI lllddea loll or 3,900 MW to thae area. This coaclitioa is u11UC1ptable. Malt or the miaina 3900 MW woald nu ha Crom the rat or the Eastern llltercoDUCtioa tlaroup die three areu' tia to the rest or dae United States and Ontario. oerldiq lin 111d cauilla inltability ill die teeeiill1 area. Ia order to reduce die ma zbnma amout that cu be Ion at one time to III acce,cable value. it hu been aareed to operate the Quebec impora ill one or two poaiblo modes: 1. Ou mode COllmtl or separada1 WI aaenton 111pplyhl1 the Pbuc D power from dae nst ot dae Rydro-Qubec system. nil is called isolated Phase 0-operadOL Tu Bydro-Qublc: syltal would in e!Cect bo split illto two pu11. Oae. die Plaue D System, woald supply no more than 2000 MW to NEPOOL OYer dae Pllue D tie. n. other. couislill1 or all the rat or Bydro-Qllebec. woald be 111pplyin1 DO more thaD 1900 MW to New York, Vermoat. ud New Bnauwict. 2. n. IICOlld operada1 mocle. appllcaba. oaly to periods or lower total imports. _, be called die .,..... D ded mode. It colllial or leaYilla the allits nrriq die nu. D Qltal COIUhlCtld to dae rat or the Hydro-Quebec ., ... at Radiaoa. "Pllue U ded9 operadoa is limited to tima wben the toc. Bydro,Qubec aporu are ao aore thaa 2.200 MW. 111d thererore ia ... ;,.._ a -zimaa loll or 2.200 MW to dae Eutena lllcercoiulccdoa. This 1,: .,_ ~. woald lea saiolll .rrccta tJau the 2000-MW loa ill ,, .tOlated Pllue 0-operadoa, bccaue die lost imports would be located ill iclely separated area. nae choice or operatin1 mode is rundamaually up to Hydro Quebec, except that the ratrictiou or 2200 MW or total imports ror the -Phase II tied mode mut be adhered to. C K ....... 6 .\1111ll1IM, 1M.
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CUI Stady No. 2 APPINDIX I c .. of n .,., LIil ,,.,.. S,stem pfnnen aad ooeraton are CODCenlld wida Com typa or events wluch eoald renlt ia Joa or senice qaalltJ, senice iat1m1pdo111, or poaibly, uteBdcd area black-oats: 0YerlNdia1 or tw'ln1PDiaioa llw hi aormal service. 0Yerloaclla1 of U... u a remit Gt a system contiJl1ency. When a tnnlfflimc,a U.. fails. power carried oa tut llll immediately starts nowill1 oa odulr 1iaa Jinkins tu same 1cura1 areu. When a 1eaerator Cails. the oatpat or dlat aeaerator is tatea 11P by other 1eaeraton, resultiD1 in c:Jaaa .. ia 1J1t6111 power no.._ n.. c:Jaaa1 may renlt ill overloaclill1 IOIM llaa after tile c:oatiDaacy. la IOIDe cues. die overloadiJla. and comequat Joa. or 101111 lbaa may ca-die oYCrloaclia1 aad Joa or odlen, renltiaa ia cucaclia1 oataaa" aad paaible area blactoats. Voltaae oa areas or tile tnaanhaioa system may be reclaced below acceptable scnica staaclardl. or may actally collapse ia voltaae iastabiliey. a a nnlt or cu ... coadapacia madoud above. Slaort c:ircaitl oa t.Nnnifli~ liaa or die nclcla Joa or major 1rmtill1 IOUCa maJ rmlt ia lfltaili iUlabilitJ. Ill tlUI sitatioa, some paeraton die ,,... an acceJerated. aad C8cn decelerated or accelerated at a dllfaat sp11d. m11da daat die aaeraton cuaot repin dleir aormal .,..,___ Eacla of tllae OCCVNIICII ii ...,.Uy IIIOCiatld wida die truller or larp IIII01111tl or power OYer tnnlfflimoa ,,,... becaw wida Iara power nows die 1J1tC111 is opcntiD1 aear to its pJlical liaits, aacl diatarbuca ii more likely to take it beyond diem. The mtcm breakdowa caa be avoided by limida1 die power trauf'cn to pven ftlaa.. 26
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CAal'IUDY .... 2 TMJlll 111110N TO Dl!LIVIR LOW C08T POwER TO IL PAIO ILIC1RIC COMPANY Pr II mtld to tu Of'nc. ol TICIUlolou ADlltMO U.S. Coaanu By: Clam. Scl11altz A Aaoc:iata. lac. 1901 Norda Fort Myer Drive Saite 503 Arlia.-, V"upaia 22209 ('703) 141-9644 PAX: 703/141-9649 NOYGDbcr 30, 1911 r 150
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CAla ITUDY N"."C IIR a 111M1111110N 10 DIUVIII LOW COIT POWSI TO IL PAIO ILICTIIC CCIIPMY TAIi.a OP CONIMII . . . . . . . . . . . I -rm R0111'N I I ECONOMIC IENUITS OF THE A-IZONA INTDCONNEcrION PROJECT 9
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Cul Shldy No. 1 SUIIIM&Y CAii lTUD'I NUIIIIIR 2 TRANIIIIIIION 10 DILIVIII LOW COIT POwER TO B. PAIO ILICTIIC caAMY 1'lle !I Puo !lectric Comouy (EPE) provida electric service to cutomcn in parts or N.,, Maico &lld Tau. It ii tied darolap ollly two EBY lilla to other utilities in N.,, Maico ud Ari--. aacl alto maiataiu oae HVI>C de, or limited capacicy, to uocller Tau dllty. a.cam ol tnmimoa coutrailla oa ia owa syncm ud 011 Mipboria1 Qltema. IPE a111t Corqo die pvcllue of Iara quatitia or low-cost ICOIIOlll'J --u available ia die Soadnrat power market ud nbltitute hither cost prod..S 1ocally widl au-111d oil-Clnd puradoL Adclitioaally, the ooapuy91 load ii powias. ucl it .... to obtaia addidoaal paeratiaa capacity. Surplus ... ,rat1a1 caoacit7 ii aftilable fro11 odNr Soatllwat adllda at a lower cost thu EPE COllld lclaw#e by baiJdin1 ..,, ....,.., facilld& Bowffer, aa iacr.. in EPE's a:ilda1 d8-UM capacity W09ld bl nqaind to cleliver tJail lower COit capacity. A .propa11d "-iaioa project. die Arirm. Iatm:ouecdoa Project, would proYide the acldidoul capacity llllded ia die ftue, aad woald a1ao mblc the company to import 1aqe qaaadtia or low-priced -IIUIJ to replace biper-cost iaterul aaeratioL TD Pit.OWEN n. tlcctric power npply sitadoa ia the Soathwest is characterized by remotely sited bueload 1ncratioa, loaa tn1aPDiai.,_, Uaa, ud a sparsely developed transmission arid. While low-cost economic power ii prodaccd by these larae base load facilities. there oCtn ue lipil'icuc distuca involved in traumittina this power to load centers. n.reton. it ii common ror atilltia to "back-ap the Jars low-cost racilitia with locallysited oilud au-tired aaeratioa. The popaplaic area se"ed by El Puo Electric Company ia southera New Maico ud Car watera Texu provides an e:zcellenc example or botll die problems 111d the bnefita aaociated with 1ddi111 transmission capability to import lower COit economy eaeru. Cu ......_ II ~11dat. lac. 1
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Cue Study No. 1 El Puo Electric Compuy serves 220,000 customen with ua annual peak load (in svmm) or 931 MW. EPE's senice area ii 1coaraphically located in the southeastern conaer or the Watena Systems Coorcliutilla Council (WSCC). As Fiaure 1 illustrates, EPE's primary tia to the rest or WSCC illcl11d1 two 345-kV transmission lines, one coucctill1 to the PNM system iD Alb11q11crq11e uad the other coucctina to Tucson Electric Power i11 ArizoDL There is u additional 115-kV tic (not shown oa the map) to Alb11q11crqae throup the Plains Electric G&T system. EPE also is tied via a 345-k V AC line ud a HVDC tic to Southwestcna Public Service (SPS) Company in the Southwest Power Pool; however, the capacity or the AC/DC/ AC inverter terminal presently limits the amount that cu be imported Crom SPS to 200 MW. l11 summary, EPE is tied to the rest or the US by oaly three EHV lines and one 115-kV line. Altho11p its principal load area ii in Texas, EPE hu 110 interconnections with any other Tau utility except ror the DC link with SPS. Its most importaDt interconnections are with Arizona and New Mexico utilities only. EPrs problem is quite simple. Witbout-expanded transmia~on access to remotely sited ~nomical acqy sources. the utility ii rorced to supply lar1e portio111 oC its native load Crom lush-cost. locally sited. au-ud oil-rired aeneratioL Table 1 summarizes EPE's load and 1neration resources projected tor the ycan 1990 throup 2000. Approximately two-thirds or the utility's total 1111eratioa resources are au-and oil-fired aeneration located near El Paso. While existin1 transmission tics are marainally surficie11t to import EPE's shares or the Four Cornen coal plant and Palo Verde Nuclear Units 1 and 2, there are sipifica11t opportunitia iD the Southwestern bulk power market to purchase additioal economy ener1y Crom other utilities in New Mexico, Arizona. Nevada. and Colorado. EPE decisioa-makcn are coavinced that the savinp to be obtained Crom these additional economy cneray purcbua more than offset the cost of b11ildin1 the transmiaioa required to deliver this ener1y. Additional savinp would result from rcductiou in the amounts EPE would otherwise pay PNM Cor wbeclin1 across its system rrom the Four Cornen coal plant or to Arizona utilities ror wheelia1 power rrom Palo Verde Nuclear Generatin1 Station. Other 1dv1nta1cs or exp1ndin1 EPE's transmission tics to the rat or WSCC include i11crcucd reliability and decreased losses. r .. -.... 2
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... \ ... MEXICO ..... Figure l. MaFC!xit b0Uflliar1.,.,_.I' of E1 PUO ectr1 e Co. ser ea te1"'1"1 to\9Y. .. E1 Paso E1ectr1 e tota9&11Y 1.0c&t1on &1111 rrans111ss1on Ties \ \ \ \ \ \ I \ .. 3.
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TABLE I II, PMQ EtlCTIW: COMPANY LQADI AND BESOUBCP JIIO ., 1111 1111 11N 1111 1111 1llf 1111 1111 2000 LO ca II 1.111ea,_..ca..oa Ml ,. Ml -Ml -Ml -241 HI HI Ulfe a.aoa fff "' fff '" '" '" '" '" '" '" ,n 1.s,-c....-c..a ua uo ua uo uo ua uo ua 110 110 110 UC..,.G u ...... c. II I ao ua ao ua ao 410 ua 410 uo 410 410 "--Tola& ca a Hn 1111 ma 1IU ma 1SU WI 1311 1JU IJU WI ISU UTolel 111 ...... (lala) -41 .. -41 .. .. -a .. -a -a .a -a Ill 0 0 0 0 0 0 0 0 0 Ulletl _._D UM ma 111'1 ma ma ma 1ffO ma 1ffO mo 1201 U.,.._D I Ll If.._ It r ntD t Ill -... .. ---MIii 1121 1111 1171 120I I.JU.. r. I I I I I I I 1,_..D 117 -... ., *' ION uor 1111 1111 1111 1214 11 " 71 T .0 Tolel .,.._ D JIii 1111 MIN 1121 1111 un 1D UM 1211 1219 Ll ...... 0..-T...aD I lff Ml m lff lfl 111 a .. MW U ...... 09wT...aD d PCT -.. Id Id 1'5 "' .. 311 1'5 "' u--,c ... I ,.1r.w---.... m tu m m 211 m m 2U 2U 21J 213 I.J 111 etT...a D d IO 11 u II .. u a a 14 T--, I ... ,. a -m m m m ffl m 10.0 MRlata 09w I r r1 .... MW .. II ... ... -m .114 -n1 --' ... No&e: A. ,,. ..,. ........ ,. I 1,-p1 I-,, LIM U ...... pa nllrn NP1' tr Pale V .. (G MW) 111d p_. C(110 MW) adJaled ._ .,,,.. Jnlpllr Dtromo (DD) Ille (100 MW) ...... a ,_. IP 1111 C ,.,
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Cue Study No. I At praat. EPE"s total act tie line transmission capability is estimated at 400 to 500 MW. Bowner, projections by EPE plauen show that additional aeneration resources will N ueded by the year 1990 to satisf'y the WSCC requirements Cor adequate rcse"e capacity. EPE atimata that approximately 152 MW or additional capability will be aeeded by the year 1995, ud woalcl be bat provided Crom remote 1e11eratio11 resources. sacJa II tlal Palo Verde 11ac:leu plut in Arizona ud the Su J11&11 coal plant in 11ordawesten1 New Muico. nil would require a conapondi111 increase in transmission capacity. More importudy, the uistin1 tnnsmiaion system rorces EPE to rore10 the purcJaue or sipif'icaat amounts or economy 1ner1y Crom remote sources. ne amount of economy aero that would be available but undeliverable (to EPE) due to transmiaioa colllU'allla ii projected at SOO Gipwatt-hoan(GWH) in 1990, but is expected to increase by the year 2000 to level betwea 1200 ud 2500 GWH. ne savinp associated with pvclluia1 dais economy eaeru provide the primary incentive ror buildi111 a new tnnaniaioa lhao called the Arizou lllterco1111ectio11 Project (AIP), which is described rart1aer ill the tollowiaa NCtioL El Puo Electric CompuJ propa1a to proviC,c the additional trallllllissioa capacity nade.;t to import low-cast economy aero ud additional 1encrati111 capacity Crom Arizoaa aad DOrtllcna New Mu.ico by baildiAa a new trananiaioa line. to be called the Arizona llltcrcoucctioa Project, wlaicll is descriNd u follows: 9E1 Puo Elecuic Company (EPE) is proposina to construct approximately 210 miles or male circ:uic 345-kilovolt (kV) craumiaion line between the cxisti111 Sprill1enille switchyard near Spri111erville. Arizona and a Luna substation near Da11ai11a. New Mexico. The li11e. kllowa u the Arizo111 l11terconncctio11 Project. would be co111tr11ctcd usi111 wood H-rrame structures approximately 75 feet in beipt. ne project would also require additions to the Luna sub-station, jointly owned by EPE, Public Service or New Mexico (PNM), and Texas-New Mexico Power (TNP), and the Sprin1erville switchyard, owned and operated by Tucson Electric Power (TEP). 1 'Sx. 1,,. fNm AriNea l&&m1mldlaa PNject, PNPmil plaa 1m 1m I al au& EIS, Pnpand Irr tbe US Deprtn I rl lat.._, ...._ ol Lad Nra1 m a,, LM c,_. D..._. Ot11a, M Mmco, Muell 1, 1911. c-. Sclmlla a& A__., lac. s
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Cue Stady No. 1 The propaud tnnaniaio11 liJle would iDtercoDDect with the emtina Arizona and New Mexico tnnmiaio11 system u shown iJI Fipn 2. Accorclina to EPE estimates. the additioa or the A1P llae would incnue EPE's 11et tie-lille capacity or 400 to 500 MW by 111 acldltloul 400 MW. DariD1 Jaearinp beCore the New Mexico Public Service Commiai911 (NMPSC) reprdia1 EPE'1 reqaat Cor a Certil'icate or Con-.eaiaace ud Need (CCN) to build the AIP. u alteraative sohatioa wu propased. Specifically. it wu suuestcd that 111 additional kS-kV line Crom GreeDla to L11aa (u illuuated i11 Fiaure 2) would be sufficient. AccordiD1 to 111pporten or the altenatie. a second Greclll to Luu line woald COit oaly a tJaird to a llalC u macJa u die SpriaPffille to Luna alternative. ne Greeal to Luu lille woald be considerably shorter i11 lea1tJa. uad there would be no need Cor the series capaciton that arc required Cor the Sprinae"ille to Laaa li11e. El Puo Electric Compuy opposed the Gnelllee to Lau alternative. co11tendin1 that. it the Grml to Lua lilae were lnailt. 111 addltioaal tnnanaiaioa line would also have to bl bailt betwea SpriaprYille IDd Grealee. n. COit or this additional line woald be approzimataly 40 million clol1an. Wlaa added to the cost or the Grealee to Laaa U... tla total COit woald come to 75 miWoa dollan. vemas 70 millioa dollan estimated tor die AIP liae. Ia addltioa. El Paso Electric cited the Collowin1 rcuoas Cor sclectia1 the SpriA1erville to Lau altcnaativc nc Arizona Iatcrconncctioa Project orrcn hiper reliability than that or tile Greenlee to Lana alternative. Reliability or service to New Mezico is improved became the Spri111ervillo station ii a stron1 source and an approved achu1e point Cor Palo Verde power. ne AIP alternative is Clll'tlaer prerenble Crom a reliability sca11dpoint because it provides trammiaioa over a path thr.t is physically scpante from other existin1 traumiaion ripes-or-way. nc A~ results in laraer total import capability Cor the entire state of New Mu.ico. Specifically. the total New Mexico import capability with the AIP line would be 2205 MW venu 2061 MW for the Greenlee-Luna altenativc. c,mw. lcludla .Aln 11. lac. 6
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... I ._,.. I ::,,:.,j FtGURE 1 Ar1zona 1nt1rconnect1on project l"1P) and areen'ee to Luna A1ternative MEXICO --' """" \ \ \ \ \ -... 7
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Cue Shldy No. 1 nae A.IP otrfln better YOlta10 porf'ormaace ia soathena Now Mexico. IA coms,uia1 tho two alterutia. it wu road that tho AJP option resulted Ja New Maico oltaps wbicJa won approximately two porcat bipcr dwl die Onal to-Lm altmaatie. TJaia Ja apecially importut since impon c:apabillty aloa1 dlat corridor Ja curady olta10 limited. TIie A.IP olCfln lower 1J1tn1 loaa dlall the 111aatcc1 alterutic Cor the adre New Maico system. Specif'lcally. total Now Muico trusmission loaa an approximately 92 MW with the AIP versus 103 MW with the Grealce-to-Lm alterutive. For all or tlae abo reuom. EPE contiaucl to ncommnd the Sprin1erville to Laa tNnPDillioa llae. lmOWII u die Arizoa Iatercouectioa Project to accomplish the 11eeded ,..nanieioa systam PlftCI& ne Now Mezico PSC 111blcq11e11dy conc,arred and ia 1917 putad EPFs reqaat tor a CCN to bllild the proposed AIP Ihle Crom SprinprYille to Laa. Accord1a1 to c:urat adlllata. the total AIP project COit will be 7L7 million dollars. bued oa the tollowill1 COit bratdowu: Capital coas or tNnaniaio11 liJla in nbltadou R.ipt-ol-way acq1Ulitioa COltl Allowaace tor Cuda ued dmia1 C0111tr11Cdoa (AFUDC) (Buecl on aa Ul1UIUld iatcrat rate or 11-'tl-) Oare lclllllla ~'- d11u, lac. 65 millioa dollars. 5 million dollars. L 7 million dollars. I
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Cue St11dy No. I 1111U11Pdoa'). EPE Ibo atimata daat approzimately 51 million dollan would be saved iD avoided wbeelha1 cosu oYer the aut ta yan u a rault or the operation or the AIP. Mon Sl*ifically. acconlilla to F.E. MattlOD or EPE: .,._ AIP will allow EPE to avoid payiaa wbeeliaa chars to otber electric dlida aad wm lower Q1ta1 tnnmiaioa Joa& For ez1mple, Public Scrvice Coaoaay of New Naico'I tnaani11ta11 wbN11a1 nte ii aow S3/tW-month. wbich WOllld aaout to SJ.A00,,000 11111ully tor 100 MW or capacity without the AIP. la adclitioa. witlloat tu AIP tbe TIICIOa lxclwl.. Aareemat woald ba ve to be naeaoda~ wlaicla coald req1lire EPE to pay SCYeral miWoa dollan per year to t1ae ArimDa utilities tor Palo Verde wbeelilla. _. ne ecoaomic ualylil paf ormed by EPE unma that the AIP would permit iDcnued ICODomy aeqy pucJaam ud aaociated prodactioa cost saviap aader nro parcllue unmpdo111. TIie tint unmpdoa ii that 400 MW or additioaal economy eaeru coald bl. imported; die -=oad 11111111Ptio11 ii that only bait thil amoaat could be imported. Ecoaomic ICID&rioa np.aatiaa tlaae two 11111111ptiou were compared with a base tcenno ia wlucJa it WU UIIIIIMld tile AIP woald DOt be built. ne amounts or power baportad rrom l!Pr1 ponioa or t1ae Palo Verde ud Four Coraen uia remained the ... ia all tlane rcaarioL Tu two 111D1Ds,tiOD1 rcprclin1 the 1111011at or adclitioul ecoaomy --., oaly arrectec1 die time to ecoaomic breakevea by a rcw months. Row..,... die pn11at wortJa ot C111111alative aet ia11 iacrcucd Crom 101 to 164 million dollan wlaa dut addidoaal ecoaomy parcbi..ses were iacreased Crom 200 MW to 400 MW, respectively. Ia IIIIIUIIU'J. EPE coatiaaa to believe that the beactits or the AIP to its customers aad to odaer New Muico rate-payers will Car oatweip the costs or the project. EPE comJ1M11iCld ia active pamait or tile AIP liae ia 1912. Aa E11viro11mental Impact Statemat (EIS) wu prepared by the Barca or Laad Ma1111emcat ia 1916, and the pracat line ro11ti111 wu approved ill Spria1 or 1917. Request Cor I CCN Cor the line wu made to the New Maico PSC in 1916 and aranted in Summer or 1987. At the pracac time. liae coutnaction ii uaderway. and the line is projected to be in service by November or 1919. iu ....... ..,.._.,...._ ... ..a p,ahdlaa ... ....... Jiu.cl wWa 111 r...., lnrnd:, ve ..... ......,.....,_..,__....__ n.,...llllrlwww a.&collplml0'5otU........, ........ ., ..... ..,.,. tel ...... '" .......... "a1-1Nal Twtl r Sled W of IP& br Q.1 N;Nn (1)ocut Mo. *4). CII Ml ...... 6 .UH 11. fM. 10
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Power Teclaaolopn, lac. TECHNOLOGICAL CONSIDlllA TIO NS IN PROPOSED SCINAlllOS FOR INCREASING COMPITITION IN THE ILICTRIC UTILITY INDUSTRY R17A-11 Prepared by: Allen J. Wood Hyde M. Merrill Power Technolo1ies, Inc. Schenectady, NY March 30, 1988
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Power Tec:baolo1les, lac. JAILI Of CQNDNJS
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Power Tecllaoloala, lac. JABLI Of CQN'JINJS PUFACE CHAPTER 1 INTllODUCTION AND PROPOSED SCENARIOS 1.1 INTRODUCTION ..... 1.2 SCIN.ARIO DISCDPTIONS 1.2.l 1.2.2 1.2.3 1.2.4 1.2.5 Sceaario I Stren1tbenin1 the Existin1 Rer,ulatory Utility Barpia . . . . Scenario 2 Expuadin1 Transmission Access in the Emtin1 Institutional Structure . . Scenario 3 Competition for New Bulk Power Supplies . . . . Scenario 4 -All Source Competition for All Bulk Power Supplies with Generation Sqrepted from T,aD11Diaion and Distribution Services Scenario 5 Common Carrier Transmission Services ID a Desepepted, Market-Oriented Electric Power Industry . . . . PI\GE 1-1 1-1 1-2 1-3 1-S 1-6 1-8 1-11 1.3 INDUSTRY sntUCTUU AND TECHNICAL RESPONSIBILITIES 1-13 1.3.1 1.3.2 Physical Limitations . . . Industry Structure and Institutional Relationships 1.4 TECHNICAL PROBLEMS POSED BY SCINAlllOS . CHAPTER 2 NEW GENERATION SOURCES . . . 1-17 1-17 1-19 2-1 2.1 ACCOMMODATION OF NEW SOURCES UNDER EACH SCENARIO 2-1 2.1.l 2.1.2 2.1.3 2.1.4 2.1.S Comments on Scenario I -New Sources and Related Technical Problem Areas Scenario 2 .. Scenario 3 Scenario 4 Scenario 5 -i -r 2-1 2-2 2-2 2-4 2-7
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Power Tecllaol01lt1, lac. IAILE Of CQNIINJS Cc;o1U111tO 2.2 SIGNIFICANT SUPPLY CIIAJlACTIRISTICS . 2.2.1 2.2.2 2.2.3 2.2.4 2.2.5 2.2.6 2.2.7 Heat Rates and Control Raaaes . . Maintenance and Unavailability Characteristics Unit Response Rates . . Fuel and Environmental Considerations Lead Time Requirements . Lona Term Availability of New Sources Plant Location and Transmission Access 2.3 CONTRAcruAL ARJlANGEMENTS wrrH NEW GENEllATION sou.as AND IFRCTS ON SYSTEM OPEllATION AND PAGE 2-7 2-10 2-12 2-13 2-17 2-18 2-19 2-20 ENGINEEUNG . . . 2-20 2.3.1 2.3.2 2.3.3 2.3.4 2.3.5 Scbeduliq and Dispatchability . AGC System Control or Generation . Economic Sttucture for Operatiaa Controls. Contnct Provisions for Coordination of Bulle Power System Plamliaa . . Contnct Provisions For Resolution of System Enaineeriaa And Operatiaa Technical Problems 2.~ TECHNICAL PROBLE~ AND ~IBLE SOLUTIONS 2.4.1 2.4.2 2.4.3 2.4.4 2.4.5 TechDical Problems in New Source Generation Scbedulina . . . Generation Dispatch and Load Foll9win1 AGC Systems . . . Generation Plannina and Capacity Reserves Solution of System Enaineerina Problems 2.5 TECHNICAL ANALYTICAL ~UES 2.5.1 2.5.2 2.5.3 2.5.4 2.5.5 Security Based Dispatch Overall Economic Effects Unit Commitment Schedulina Economic Framework for Non-Traditional Generation Services AGC System Desian . . ,. ii 164 2-2t 2-23 2-24 2-25 2-26 2-27 2-27 2-29 2-30 2-31 2-32 2-33 2-33 2-34 2-34 2-34 2-35
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Power Teclaaoloala, lac. IAILI Of CONJINJS Ccontlaucdl CHAPTER 3 INCU:ASID TRANSMmION AC~ AND WHEELING 3.1 WHIILING AS AN &UE .............. 3.1.1 3.1.2 3.1.3 Wheelin1 Practices . . . Difference between Supplied and Delivered Power Possible Problems and Solutions . . PAGE 3-1 3-1 3-2 3-4 3-5 3.2 ~DILi EFFECTS Of CONTllACTUAL ARRANGEMENTS. 3-5 3.2.1 3.2.2 3.2.3 3.2.4 3.2.5 Money Wheelina . Loop Flows . . . Contract Types . . . Effectl on Operations . . Contnctual Eff ecu on System Evolution 3.3 ~DILE OPERATIONAL AND PLANNING PROBLEMS 3.3.l 3.3.2 3.3.3 3.3.4 3.3.5 3.3.6 Real-Time Control . Scbedulina Problems . . Masimizina Network Use . Transmission Plannina Problems Solvina System-Enaineerina Problems Emeraencies . . . 3.4 ANALYTICAL PROBLEMS 3.4.1 3.4.2 3.4.3 3.4.4 CHAPTER 4 Def'lnition of Available Transmission Capacity Reliability and Security Issues . The Transmission Schedulin1 Problem Costina, V aluina, and Pricin1 . SUMMARY Of TECHNICAL WUES AND POSSIBLE SOLUTIONS . . . . 3-5 3-6 3-9 3-11 3-123-13 3-13 3-16 3-17 3-19 3-20 3-22 3-24 3-24 3-27 3-27 3-29 4-1 4.1 SUMMARY Of TECHNICAL PROBLEMS POSED BY SCENARIOS 4-1 4.2 MEASURING TRANSM&ION SYSTEM CAPABILITY . 4-2 ,. iii -1 ,, -! ..., .a. t., V
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Power TeclaaoloslN, lac. IAILI Of CQNJINJS PACE .. .J SPINNING RESERVES AND UNIT COMMITMENT 4-3 ... 4 AGC SYSTEMS AND FUQUENCY CONTllOL 4-4 .. _, SCHEDULING TRANSMISSION SYSTEM USI 4-7 ... aULK POWla SYSTEM PLANNING PROBLEMS 4-9 ... 7 PROBLEMS ULA TED TO DISPATCHING 4-10 .... SOLUTION OP SYSTIM-WIDI noaLIMS 4-1~ ,. 1 ,.. 6 ~"' > iv -
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Power Teclaaoloal .. lac. rllfACI
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Power Tecllaolopn, lac. PREFACE nus report ii one oC two submitted to the Office of Technolosy Assessment of the U.S. Coqrea (OTA) by Power Tecbnoloaies, Inc. (m) u part of the effort of OTA to provide information to the Conpea in tbe potential restructurina of the electric utility industry. nus report deals with tbe tecbnolop:al blckaround of the industry in the U.S. The companion report. -Yeclmical Backaround and Comidentiom in Proposed IDcreaed Wheeli.q, Trammiaion Accea and Non-Utility Genention, discusses the aeneral teclaDical pects of tbe electric utility industry Uld those technical issues speciCJcally related to iDcreued transmission access, wbeelina, and non-utility aeneration. A number or unresolved techDoloaical issues are set forth in this repon. The autbon wish to express their appreciation to the various enaineen in the indllltry who have been kind enoup to supply data for these reports and who have reviewed tbe drafts of tbe texts. Specuacally, we wish to thank the American Electric Power Service Corporation, the staff of the North American Reliability Council (NERC), various memben or the NERC Operatina Committee and the Electric Power Research lmtitute (EPRI.)
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Power Teclaaoloala, lac. QMlOIJ
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Power Tecllaoloaln, lac. CHAnER 1 INTRODUCTION AND PROPOSED SCINAIUOS 1.1 INTRODUCTION This nport extends discussions contained -Yecbnical Baclc1round and Considerations Transmission Access and Non-utility Generation. in the nport in Proposed submitted Increased to OTA, Wheeling, The cumnt report presents five scenarios developed u a result or a workshop sponsored by OT A in the fall or 1917, summarizes the expected industry structure under each. e:itplores major technical problems. and discusses possible solutions. This chapter describes the five suuested scenarios, postulates resulting industry_ structures that would satisfy the conditions or each scenario. and outlines the sipiflcant technical problem ueas resultin1. In the scenarios which depart the most from emtin1 industry structure, the industry structure arrects the feasible solution mechanisms to some or the technical problems. As each successive scenario assumes mon competitive forces in the industry, the existin1 verticaliy integrated utility beains to disappear from the scene, The responsibilities and functions necessary to make the utility subsystems and interconnected power systems function properly in a teclmical sense are usiped to the successor entities. The broad cluses or technical problem areas of concern an those raised by new generation sources and those associated with the transmission systems. These are discussed in the second and third chapten, respectively. The fourth chapter summarizes the technical issues and possible solutions. The technical problems associated with dispersed generation sources (DSGs) which an connected to the distribution systems an independent or the structure or the industry for all practical purposes and an not treated in any depth in this re~rt. The previous OTA report. cited above, summarizes the technical problems associated with these smaller. dispened non-utility sources conn9':ted to the distribution -1-1-
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Power Tec:llaoloal11, lac. system. The technical. problems raised by the five scenarios that are discussed are primarily 1110Ciated with bwk power systems, 1eneration, and transmission systems. Tbroupout these reports the terms wheelina. wholesale wheelina and retail wbeelina an used. The def"mition or wheelin1 used is that aiven in the glossary appended to the recent report "Some Economic Principles For Pricing Wheeling issued by the National Rqulatory Research Institute: "WhNling -The use of the transmission facilities or one system to trammit power or and for another entity or entities. The two subclasses or wbeelina an defined u shown below: WJacmeJ, WbccJia -The wheeliD1 of power for delivery to a utility system. Retail Whg)ip -The wheel.in& or power r or delivery to a retail customer. 1.2 SCENARIO DISCRIPTIONS Five alternative scenarios were developed u a consequence of the OT A Workshop held in the fall or 1917, and are described below. Each scenario description outlines the industry structure envisioned, the rqulatory structure, the degree of transmission access, the modes r or 1CCOmplisbin1 system operating and planning f unctiom and suuested pricin1 mecballisms. Possible industry structures under each future an discussed in section 1.3 in order to define terms and to further specify the structure iD the scenarios which are the most diver1ent from the current structure. -t-2-
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Power Tec:llaoloal, lac. 1.2.1 Sceurlo 1 s1na1tll ,11. lxllda ........ ,, Udllty aarp1. Scenario I continua the 1Jtiatin1 rqulatory acheme and electric power industry 1tnactun aad rarranm tbe naulatory-utility barpia. Minor modifications of rqulatory rui. and procedure1 improve the ability of utiliti to attract capital for construction of new facilities and to uaure a reuoaable return to iaveston (e.1., ro11in1 prudence reviews). Modifications of PURPA ruin to correct perceived iJnbllances in avoided cost pricin1 ruin for QF power are also allowed. Many utilities continue to rely on QFs and IPPs for a portion of new power needs. Trammiaion accea remains on a voluntary basis to be neaotiated between the puticipu111. FERC retains its authority over trammiaion rates and wholesale power.._, iualtry 1tnctlln: Then is a mix of vertically-intqrated utilities; investor-owned utilities; public power, cooperatives, aad federal power authorities; self-aenenton; qualifyina facilities (QFs), and independent power producen (IPPs). Trends of internal realipmentl and restructurinp and merpn and acquisitions continue within limits of existina laws. 8eplatory ltnctlln: The existin1 f edenl and state rqulatory scheme continues, with no cban1es in PUllPA, FPA, PUHCA. Minor modiflcatiom/ldjustments an made u noted above. T111aloa Accea: Utilities may provide ICCIII votuntarily for wholesale and retail customen. No new NRC wbeelin1 orden part or new nuclear plant approvals an likely, since there are no new nuclear plants. Strin1ent standards r or FERC wheelina orden also likely to preclude mandatory wheelin1. States have limited jurisdiction. -1-3-
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Power Tecaolosl, lac. S,ste O,.ndoa: $nM nDa,mb 114 CAAnlJ11&Jo1 is maintained by the local utility control center. For non-utility power 1uppliN, opentionai nspomibllldel are bued on contnct terms with the local utility. DltNtclt ii determined by the local utility (perbapl Wider a power pool qreement) for utility owned or leased units. For QFs IDd IPPs, dispatch depends on contnct terms with the local utility. lm11c1 cwdflJII are allocated accordina to state-reaulated curtailment policies. Pluala1 ..t 0.lo,la1 RNOIIICe Addldou: GnmU nrr!m Utilities develop capacity eKpusion plans with state reauJatory ovenipt. QF1 are mured market for their power under the state's implementation or PUJlPA and are a component or the expansion plu. IPPI may be included ill the Hpusion plan u determined by the utility and state reaulaton. QFs, IPPI, and self-1eneraton plan and build capacity bisect on their own perceptions or need and profitability. In-= edd1U1u reauJatory approval. tnmmiaion lines, but nplatory ltltul. are developed by local utilities subject to Some non-utility entities may build private bave no eminent domain authority and uncertain Dltlddt edd1dou are the responsibility of local utilities with nauJatory approval. Ceersdo Md Jud & proarams are developed by local utilitiel with rqulatory approval. Prlclaa: Prices an set by utilities in naulatory proceedinp. Most retail services are bundled, but states allow utilities to offer s~ ,cial ntes bued on difr erent reliability levela IDd services to larae retail customen in respome to competitive pressures. Tnumillion prices are rqulated by FERC. States have limited jurisdiction over transmiaion. -1-4-
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Power TecllllOlotlN, Ille. 1.2.2 Scnarlo 2 1.,....., T,....luloa AcCfll la tl1e Exlldaa la1dhldoaal Stnctan Scenario 2 ii intended to iDcreue both the number or bulk power sellen and the number or potential ~ullc power bu yen by I) removina some or the size, technoloay, fuel, ud ownenhip limitations ror qualif'yina facilities throuah leaislative modifications to PURPA and the Public Utility Holdina Company Act; and 2) cbanain1 the mandatory transmission access provisions or the Federal Power Act to a broader public interest standard to make utilities and larae retail customen eliaible to apply ror mandatory wheelina onten. Policies intended to encouraae bulk power sales and wheelina are continued 111d expanded. ladutr, 1tnctan: The emtin1 mix or utilities, self-pnenton, coaeneraton, independent power producen continues. Unreaulated utility subsidiaries or affiliates increase participation in bulk power supply. Current trends or restructurina, mer1en and acquisitions continue. R .. latorJ 1tnctan: The existina federal-state rqulltory scheme continues, with wider eliaibility for QFs under PURPA and broader FERC authority for illuina mandatory wheelina orden for utilities and lup retail Cllltomen. Traualaloa acceu: Utilities 111d Iara retail customen can petition FERC for mandatory wheelina orden to non-local aeneraton bued on I new public interett standard. S,ate 0,.radoa: $nit n11, .. 11tx cooallto is maintained u in Scenario I. Qlfutcla
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Power Ttcllaoloal, lac. lnt"Y ClrS&Uta ue allocated curtailment poUciel, u in Scenario I. wbeeled power. curtailment and backup Nrvice contncll with the loc:al utility. Plualaa alMI O.elo,1 .._ra .w.ldou: accordi111 to state re1ulated for outaa of non-utility or power are bued 011 standby GtvnU qpglty; Same u in Scenario 1, with one addition. IPPs (u well u Qf1) an 111und a market for their power under the state's implementation of PUllPA and an a component of the capacity expansion plu. Toewtn,, eddt!lolF Same a iD Scenario 1, with the r ollowin1 exception. Slatll may requn that utilitiel include provisions for adequate trammiaion capacity for wheelin1 Nrvices in system plannin1. PllldMlkt eddU19M Same u in Scenario I. CeerU u !ned t; Same u Scenario I. Prlcla: The eutia1 1tructun of price and service rqulation ii Jaraely left undisturbed. Prices paid to power supplien under PURPA ue bued on states' avoided cost rules. This includes UN of biddin1 systems by some states. Transmission services and pricin1 an tablished by contract neaotiation under FERC jurisdiction. 1.2.3 Scturlo 3 Coa,eddoa for Ntw Bulk Power S.ppll Scenario 3 establilhN an institutional structure to allow all source competition for new bulk power suppliN with market bued pricin1. The scenario is loosely based on the Keystone and H1111 proposals. Trammiuion access ii included u a pnrequilite r or participation in the competitive system. Mandatory transmission accea under the public interat standard of Scenario 2 ii also available for bulk power tramactions by utilitiN. Provision of wheelin1 services to retail customen remaim voluntary. UtilitiN are able to participate in biddin1 for new capacity within their own Nrvice territories and those of other utilitin with appropriate ---
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hwer TeclaaolotlN, lac. llf'eauardl to limit problems or 11ar -dealln1, connict or interest, etc. Scenario J creat91 a two-tiered bulk power supply system. New power ii supplied under a minimally reaulatad, workably-competitive market with 11istin1 1enention ramainin1 under the current state-federal scheme or rqulated entry and pricina. The electric power supply industry 1radually evolves to an all-competitive 1enerat1n1 sector u eKistin1 plants are replaced. Trammillion Uld distribution 11rvicel remain bi1hly reaulated. la ... try 11netan: n. emtin1 mix or utilities, 11lf-1enenton, coaeneraton, independent power producen ii expuded by entry or unreaulated utility sublidiariel/divisions/spinorrs created to build and operate new 1enerati:11 facilities ud to sell power in coma,etitive market and other new entrants made eliaible by modification or PURP QF requirements and cbu111 to the PUHCA. Replatory 1tnctare: The uaderlyin1 federal-state public utility reaulatory scheme is maintained but entry and pricin1 rqulation for new power supplies is replaced by all source competition. Tbe 11nentiD1 sector aradually is transformed to an all-competitive system u eutin1 capacity is phued ouL Trammiaion and distribution remain hiply replated. Traualuloa accea: Three mechanisms eut r or provision or transmission services: l) voluntary trammillion qreements for utilities and retail customen; 2) transmission access for new power supplies ii mund u a precondition (or utility participation in the competitive biddia1 system; and l) mandatory public interest' transmission orden an available from FERC tor utilities, but not for ntail customen. -1-7-
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,o.., Teclll...._..., lac. s,. ... 0,.,.dom ID,,_ nJlalplllty Mtl ClldlNUM it maiDcaiDld u ill Scewiol I and 2. mere: c,,1,w,w ft 1rd'11> ii the w a ill Scenario 2. lwmw ceueflw!I an the same ill Scelllriol I UICI 2. Plaut ..... Dllofla ..._ra AeWdou: C.pgd Ceeed'Ji Sime iD Scenario 2 with Lbe f ollowill1 eKception. The stalll an required to UN competitive biddin1 iDcludina consideration ol DOD-price (ICtDrl ill Nlectial MW power 1upplill. In11efpl91 eddUSau; Al ill Sceaario 2, tbl public utility tr1111million compuay/divilioa plam ud comtnlCtl .._ummiotl capacity with review ud approval or reaulalory aulboritill. Slare na1e1 may require ulililiel to plu for ldeQUIII capacity for imtate wheelia1 or new power supplies ud to coaider ,eaioDal trammillion DNCII. JMeldr.,,,, dd!tlePF Sama ill Scelllriol I IDd 2. Ceea Mtl Peed eevwac Same u in Scenarios I UICI 2. Prlcls: cr power supplies remain under 1xiltin1 price reaulation. Prices for new power supplies are market bued, set by competitive auction or neaotiation. New power supply prices cua ref'lect level of service 111d other non-price racton. Greater reliuce on tnmmiaion rvicel may iDcreue preaun for tnmmiuion pricin1 baled oa actual COit of Nrvice with allowucea for DOD-price racton. Transmission prices are rqulated by rue. 1.2.4 Sceaulo 4 All Soara Coapedtloa for All Blk Power S.ppl111 wltb Geuradoa Seansated froa Twluloa DlltrllMldo S-nlcn Scenario 4 createa a competitive system ror electric power supplies. Exiltin1 and new IOurcet compete to sell power to reaulated trammiaion and distribution compaaiea. lntepated utilities are required to sqnpte 1eneration activities both illltitutioaally and operationally from trlDlmiaion and distribution, throuah creation of separate diviliom, subsidiaries or spinorrs. Trammiuion and distribution ---
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Power Ttcllaoloal, lac. activities ue heavily .rtaulalld. Mod111catiom to PUllPA QF requirements and PUHCA ratrictiom allow broad pudcipadon ill 1eDention maru11. Local distribution compuiel an primarily nlPC)llllble for NCUriD1 adequate power sappU. from compttiq supplien. Trammillion clivitiom or sublidiary companies provide w11NliD1 NrYica for utilitiea Wider naulatad ra1e schedules ud can also act a power broken linkin1 local distribution compuiel with power supplien. Dittribution compuies can obcaia mndalOry tnmmiaion orden from FERC on a public illterest 11Udard. Then ii DO modlrory wbeelia1 for retail customen, dloup it ii Hpectld that p11eraton &Del tnmmia~n compenies would en111e in direct salll to larp retail customers on a vol111111ry bail wida bypua or 111Ddby payments IO local distribution companies ..... try 11netan: Vertical iatepation or industry ii reduced by separation or utility 1eneratin1 ...-.011 from tnnaniaw,n IDd diluibutioa sqmenta. Sepepled utility 1eneraton, QF1. IDd IPPI competa to provide power supplies to trananiaioll-disuibution and local distribution coma,uill. Some ttulmiaion compeaill allo act u power broken. IDdustry ltnlCtlln ii similar to that or Dlhlnl au iDdaatry. Replatory 1tnctare: Price IDd entry reaulation for electric power supply ii repllced with a competitive market. Scates reaaJata distribution coms,u1ill &Del ncail 111ea. Then is milled federal &Del 1t1te repladoa or tnnaniaioD capacity IDd rvicel. Under this IC8Wio dlll'e is tlll pocndal for iDcr1d federal naulatioa IDd oveni1ht of power ..._ IDd formerly iatn-.,.._ trMlfflilaioa unnpmnll. However, implementiaa lqisladoa could provide for a more bllaDCld feclenl-statf division of reaulatory authority IO pve 1ta111 areater control over iatra-state ICtivitiel. y.,..,,111,_acceu: Wida FERC endonement. 1tate1 make noDdilcriminalOry accea to traumislion NrYicel a precoaclition for 1xiltia1 r91ulatld 1enention. tn111111illion. and distribution compuiel to pardcipale in tlll new competitive 1ys1em. FERC has -1-9..... ""
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Pewn TtcllaolotlN, lac. authority to order wbNlin1 ror customer utilities on a public interest standard. Tl'Ulllliaion accea ror retail customen ii provided on a voluntary buis. s,. ... O,.,.IIN: IDIW Nllalplllty u cadl11U11 ii maintained by the reaulated tl"IDlmiaioa company or trammillion-diltribution company. Operational respomibWtiel or power supplien and the local distribution companies are specirlld iD contnctl. 'lrrklt are determined by various contracts blew pc,wer supplien IDd either. I) the reaulated transmission compaaill; 2) die naulacad distribution companies; or 3) retail customen. lwmw cedlUn11 ror retail customen served by local distribution compuia an allocated accordin1 to 1cate rqulated curtailment policies. For otblr customen. curtailments an specified in contracts with the nmmiaion IDd pnention supplien .... ................... ,a .M.lldou: Gt-enOn nrde:a Electric supply nquinments an determined throuah local distribution company plaania1 proceaes with state oveniaht. Colllpetitioa ror supply contnc11 ii open to all 1eneratin1 sources, u in 5ceDario 3. Tl'IDlmiaion utilities may contnct for 1enentin1 capacity to allow diem to m'YI power broken subject to scate and federal rqulatiota. 1n-rfee ,11:u... n. reaulatld tnmmiuion or trammiuiondiltributioll companiN have tbe obliption to provide transmission CIPICitJ DIC 1111ry to suppon wbeellna needs ror imcate utilities. States -Y nqain tnmmillioa capacity plaaain1 to include comidention and coordlmdoa or rep,ml ,..mmmioa system needs. JNe:dlklr edd1""8; Same u iD Scenariol 1. 2. and 3. Ceerdee IN hid Ii Comervation and load manaaement prosrams an provided by local diltribution companies, poaibly in coeJUDCtioll wlda tr1111miaion companies. Prlclas: Bulle power lllel an Nt !Jlrou1b competitive markecs. Transmission services are r91ulatad by 1cat1 IDd federal autboriti. Power purchases by distribution coaapulll IDd retail n111 are rqulated u now by scate authorities. -1-10-
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I .J.S In 1ufe 5 C.-nea Carrier T.,,rnI Senlcn la a DeNanlatetl, ....... Orlft ... lllclrlc ......... .,, TIii electric power illdustry it divided iato imtitutionall;,r teparate aeneration, 1rUlailliola. ud retail distribution .....-11. Tbe major difference between this ....,. ud Scnario it tbal ...,.,.. trammillioa compujes an explicitly NQ8,ind to provide tnNfflmioll lll'Vicel COIIUDOD carrien--i.e. nondiscriminatory 11nicl bwd oa appro..ct nNliaa lariffa--to all partill reqwtia1 wvice. The IN I ieioll CDIIIPUJ woald M\'9 U oblipdoa to provide ldlq_.. traumiaion capacity ...,,. u n .,nnx rw;Ne, BIAIVIWRII CAt on rnmm;aiQo en, r reM N t st -_.,n IN rn,mpi; Cwibiligy. Retail customen Me ICC8II to ll'llmewioa llffica Diltributioll IDd trlNPDilsioD services remain tipdy .... ,111d, bin ia die IIK1ric .......,. ...... t. market entry wt bulk ...., swiciaa .. priaarilJ Wt to aartet rorc:ea. Federal wt ... policies. auaht --=om 1 .,...... ...,..... ia 1r1.-i11ic,a NrVicer to create coordinated larae repa1II 1nme+-ioe ,,_ eidlll' duoap me,aen IDd ICQllisitiom or throuah openlioal ..,,,., ....... aeipboriq .,... __ ,ar, ----n. QHllplliti,,. ....... ....... iDcludll (ormerty-replaled utility aeneration opendoa, QFs. 111d IPPL Replalld IN- syslam an operated u common carri9n. llaplallrd local diltrilNatioa compea provide retail rvica .... ,.., ........ ir abject to miahne 1 reaulatioa to un existence of n. ,.,_,io ...-t ii reaulated u a common ..,..,_.,_ Local diltributioll companies an Noel dlal dllrl ll8derliMcl planNs ..,. addld to the oripaal ICenario deecl ipdoa to r.crict 1111 lmpUed oblipdom or a common carrier" power tnNPieic,a compuy to levels appfied to other common carrier mepeill (i.e., pr pipellw, railrOldr, airliw, etc.). -1-11-
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Power Teclulolopn, lac. T .. e,w1uloa access: Common carrier transmission accea services available on nolldilcrimiutory basis to wholesale ud retail cmtomen. Wbeelin1 customen could contract for different levels of service. s,.... <>,eradoa: sun nHalpQ1t1 M4 mnl,lutlot is maintained by the separate, reaulaled trammiaion compuy. Operational responsibilities of power sapplien IDd the local distribution are specified by contnctl between diem and the tnmmillion company. PIIM!c CtJesneeac H Peed!> ii cleterm.ined u in Scenario 4. ,,,..,..., cv&eHNIII are allocated II in Scenario 4. G-m#n cerd!Ji Same a in Scenario 4. rn-Hn ,,,,,,._ Tbe tnnun9aioll utility bu an obliption to provide an ldequaCe IDd reliable trlDl!Diail>n capacity weaary to supply die wbeelin1 DNdl of anticipated customen. lleplatory authorities may require comideration/coordinarioD of reaioaal t,aDPD9aion capacity Deldl. PltldM#OI dl!dOlli Same II in Scenariol I, 2, 3, wl 4. Cenm,u,, 1M W .,.,., c Same a in Scenario 4. Prides: Balk power sales are let throqh competitive markets. Transmission services are reaulated by state ud federal authorities on a common carrier buis. Transmission raam include adequate sipals to aaure construction of new trammiaion facilities. Power purclmel by distribution companies and retail rates are reaulated, u now. by state authorities. -1-12-
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hwwTecNIOINI., lac. 1.3 INDUSTRY snucruu AND TECHNICAL RESPONSIBILITIES Table 1.1 summuizm the orpaizatioaal components in the industry structure palhllared in each scenario. Tbe technical fUDCtioa respomibility usignmena to die various entities stated in the previous descriptions are also indicated in this cable. Tbe rqulatory and pricin1 issues in the detailed descriptiom in the previous sublectiom are not included in the cable. They are obviously impor1ant attributes, but Jbey alfect the major teclulical problems only iJldirectly. Several abbreviadom are 1118d in the table IDd tbroupout this report to denote succ1aar ~oindom to the disqanptecl operations of existina. vertically intepated electric utilities. These an: DISCO GENCO TllANSCOT&D Co. tbe distribution company, die paeratjon company, tbe tnmmiaion company, and I combillatioD of the TllANSCO ud DISCO. It is not intended tbat tbele abbreviatiom refer to any existin1 or planned company specuJCally. -1-13-
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,_,.. Tec .. ol..-, Jae. I. :!IE-11a DllTJIII ~ urn.m ...... ,. -,I-'It ___ ... ----NRMJ-. m::,,1111,...,IIU ............ I. U --CDGliJfial All u au,.. ....... Mffll Wll II ... ,_ 11 a WIUIIWDISTUMJGII ...... 1. ... CMUa Tltaama ---. -.T IIINID ILICfllC ............ VIITJCIUY DmaATID D1U11Y 111111 CUIINI' ltU:NII .... w. IXIITINll1al:UI IINIUI 19 a. IXIITINI IIMIIIII -BfflD If Nilf. --.a1'1D curn.m IIBIMIII, 11 C11111111 ,a _, -TUii WII IGTII ... .. ....... WIIYDU.Y DftlaA1'1D unu1Y 11111:1\111 ------TJCll 11 ,_ -NCDalMTDTIU ....... n11n. 1T1UCN11 U11 -' -------.... PP-S MITIC'IPll11 -n WHlllbll. aN\111 IIW1 -TICIN unun .................. .. w,111 aaana IR!l1II 111111 _., N IPP'a OiNIT1NI MIA&. ,m-.&,maATICIN. --UDLunL11Y lllflNIIILl1'f. .... ,. .... ,. .... IPUalMaCO"IMY MITICIPATI a LGIIID MIAEJaf NaNDVan& ...... OIBfflM.LY A alffJNMnlll -1NU11'151IIO\IIEN ,um llffllllff MDnllY llNIGIIICII MXUI. ClllffllUTICII f6 -l1IUCMI 18111 MIDITUlt --Till'I 111111.JNI PIOIJSIN ,. urn.nm uaa U1IIDI ..... INU1l't ff ALLGDI INIIIIUTID Urll.11Y ..... Ill ,. 11D Ill ... -n ..... -ffCIN Tv WHCllllllt EnDG I TO MIMIII mftTITICIN ,a NTN CU N 8 mDATICII. l1IUCMI GWIK IDIMI mDATICII nCIN um.nus IIU.Alll llMaCD'I SDUUI TO MnaM. N PIPII.N a.MIU. 9MATll__...,,_ana iNISII IIW'I. WHTIJICII ,a M.L -TICIN NLID CMllllaPl#AMIDDII ,aa, ..,.,. u..., IMaCD'I TO DCGIPMID. -t-14-
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Power Teclaaolosl, lac. The teclmical problem. areas associated with increased wheeling and transmission access, the potential structural changes in the utility industry. and the increased levels of non-utility generation are related to: o transmission network physical limitations, o system planniag, operations, engineering, and o industry structure and institutional relationships. Table 1.2 summarizes the organizational entities, the assignment of the respomibilities for the three major technical fuactiom under each scenario and indicates the mecbaaisms for institutional relationships. The technical functions fall under three catqoriel: I. operatiDa and control (including the responsibility and authority for scbeduling generation and traasmiaion nows), 2. planning and development (including responsibilities for planning and development of new trammission and generation facilities), and 3. system enpneering (includiaa the responsibility and authority for establishina reasonable enpneerina standards for transmission system access and for seekina solutions to system-wide engineering problems.) Primary responsibility usipments are denoted on the table by an -x with a "C" indicating that responsibilities would be assigned by contracts between the parties. ID Scenarios 4 and 5 the TRANSCOs or T&D Companies would have the option of actina u power broken (denoted by a "B" on the table.) In the last two scenarios the TRANSCO, would take on an ovenipt and coordination responsibility in the aeaeration pl1naia1 area in order to perform the transmission planning and development functions. -1-15-
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Power Ttcllaolot SCDNIO ..... I STIIBtllMIN EXJSTN ISNISIICII Cl:al ,... urn.1m a,s' IITAll. aaTOO I( IP unLIT a,s' IITAIL UTCIUI 1a, DI 1 urnma t ,.,SGUICI ... "' CIMITITICN CIFS I IITAJL UTNII a TU Cl .I I M.L SGUICI TUNICIIII CllftTITiat GIJCIIII I CIMllt CMIIII en, "" IITAJL U1'0IIII DISCIS Twa:111 IINCIIII en, ,,.. IETAII. UTODI DIICXII X PIJNAIY IOI 0 MISIClff II I ,aa IIICIICD C m-.1HD MTOI OGll&IN STMILl1Y, M'UJINfAJl(N IMWIIC:S. r, SO.Ul'ICNS nc. TD fflTDI PIOIUNS X X C C C C X I C C C C X X C C C C C C X X C C C C C C C C X X C C C C C C C C -1-16-
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Power Techaoloales, lac. 1.3.l Physical Llaltadou The basic physical limitations in existina transmission systems are unaffected by the institutional structure of the industry. Barrina any dramatic, major improvements in the technoloay of electric power systems, thermal limits will remain and systems will still need to guard against dynamic problems. Reserve levels of both genention and transmission capacity will need to be provided to ensure system reliability and prevent cascading blackouts and system operators will still need to operate the systems within frequency and voltaae tolerance limits. 1.3.2 ladll1try Stnctan ud Iudtudoaal Reladomblp1 The various changes in the industry posed by the scenarios influence, to varying depees, the accomplishment of the required plannina, development, systell! enpneering, and operating functions. With the current industry structure, the responsibilities and authorities r or these functions are well established and defined. When there is a technical problem involving both the transmission and genention subsystems, the vertically intearated utility can seek a solution and implement it. When technical problems involve interconnected (and aenerally non-competitive as well) utilities, they voluntarily cooperate in order to seek conducted, joint solutions with each participant contributin1 to the solution implementation. The different industry structures affect the nature of the problems in system plannina, operations, and system enaineering. With an industry structure with intearated utilities, the technical problems in plannina and operations are treated as problems to be solved for the aood of the entire utility and its customers. With non-utility aenention competina with utility aeneration r or the market, however, the economic objectives of the various entities may be different. The non-utility 1enerator bas the aoal or maximizina his profit, the TRANSCO may be controllina the system to meet all its obligations with the aoal or maximizing system use within economic and tecbn1cal constraints and the DISCO is interested in -1-17-
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Power Tecbaolo1l11, lac. achieving minimum revenue requirements. The GENCOs and IPPs would wish to produce maximum sales unless compensated for "lost sates (that is, power curtailed for purposes of controllina the system's opentions). The TRANSCO with its responsibility to opente the system reliably and securely has a technical need to control the aenention and transmission network flows. The solutions to the various system planning and system operating and scheduling problems will take cliff erent forms in cliff erent industry structures. For example, as Iona u the existina utilities are on the scene and control the majority of the aeneration resources (i.e., that is throuah Scenario 3), the generation scheduling and economic dispatch procedures may be based on existina methods. When all of the aeaeration resources an under the control of independent GENCOs and IPPs (viz., in Scenarios 4 and S), the schedulin1 and economic dispatch methods may be entirely cliff erent. With tbe disaarepted industry structures envisioned in Scenarios 3 through S, problems involvina more than one seament of the bwk power system will have to be implemented by nqotiation, contract terms, new enaineering and economic techniques for plannina, schedulina and controllina aeneration, and tnnsmission. Technical problems involvina interconnected systems and requiring coordinated enaineerina studies and solutions may need to be conducted in a competitive environment. Cumnt experiences with wbeelina arnnaements shed some light on the effectiveness of this mode of implementation. Informal discussions and surveys of utility oraanizations indicate that where non-competing organizations have been involved in-wheelina nqotiations, there have usually not been insurmountable barrien to the establishment of satisfactory wheeling arranaements. When competition bas entered the scene, arnnaements are f requendy contested and lead to bearinp and requests for reaulatory or lepl resolution. -1-11r
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Power Ttcbaoloaln, lac. Discussions arranaements with utility have elicited people throughout the world concerning wheeling frequent comments to the effect that when legal considerations come into play before enaineering uranaements have been worked ou~ wheeling arrangements ue almost always unsatisfactory. Gentlemen's qreements between utilities that recognize, amongst other things, the physical realities of the systems' limitations appear to have played a luge role in making past arrangements r or wheeling. The intrOduction of competition and requirements for legal consideration as a fint priority have been reported to make these arranaements more difficult to implement in a satisfactory technical manner. (Or as one utility engmeer in Germany stated. ... When contract terms ue dictated by lawyers. they are always unenforceable and impossible.) Be that u it may. the purpose of this report is to explore the technical problems, solutions and requirements for investiption of technical-analytical issues and thtt development of new methods for such things as transmission scheduling raised by the five scenarios set forth. Each succeeding scenario envisions a greater degree of participation in the generation market by non-traditional utility subsidiaries and non-utility entities. Each scenario poses a different level of access to the trammiaion system ud increased wbeelin1 of power. 1.4 TECHNICAL PROBLEMS POSED BY SCENARIOS The technical problems raised by these scenarios may be divided into those IISIOCiated with the increued involvement of non-utility generaton and those caused by the increue in tnRnunisaion system access and wheeling. Each scenario poses diff erina levels of these activitia. The next two chap ten discuss technical problems in this framework. Chapter 2 is concerned with the problems associated with intearatinl non-utility 1eneration sources into the systems and Chapter 3 is concerned with problems and solution, associated with transmission access and increased wheelin1. llf r
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Power Teclaaoloaln, lac. The technical problems are, of coune, closely interrelated: the discussions overlap to some extent. They fall into the broad catqories listed below alon1 with sub areas. l. Problems related to system operations and control; L AGC systems for frequency and tie line control, b. aeneration schedulina and dispatch for system security. spinnina reserves and economy, c. aeneration and system VAR source control for maintainina adequate voltages, and d. schedulina and controllina transmission flows. 2. Problems related to system plannin1 and development; L 1eneration plannin1 and development for maintainin1 adequate reserves, b. transmission plannin1 and development to accommodate new sources and increased transmission uses, and c. identifyina transmission limitations and increasina trammiuion system capabilities. 3. System enaineerina problems; a. definin1 and measurin1 transmission capabilities for reliable power transfers, b. identifyin1 and solving dynamic problems, and c. emer1ency plannin1 and restoration. -1-20-
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Power Techaoloaln, lac. The increued level of_ non-utility aenention in each succeeding scenario affects the relative importance of these problems. At one end of the spectrum in the first scenario, generation ownership, control and responsibilities for system planning and opentions continue u they are at present. In the lut scenario matters are entirely different. There is a real need to define available transmission capacity in a simple form for eue of conducting neaotiations for n,pplies and system access. Transmission system schedulina to accommodate the numerous contracted transactions will be important. The control of the aeneration system will be a divided responsibility that will require new techniques and arrangements to handle unit commitment and spinnina reserves. Economic dispatch u practiced in current systems may vanish and be .eplaced by a new technique to schedule transactions only. Economic models and schedulin1 techniques may be needed to compensate independent 1enention entities for providina reserve service, participating in voltaae control, and for allowina system control over aeneration levels to aid in system security and transmission system schedulina. As wbeelin1 and transmission access increase in each succeedina scenario a similar increase in the nature and volume of technical problems occurs. Unambiguous definitions of transmission capability will be required. ID the first scenario where the increases posed are modest, technical problems are similar to the current set of problems. In all the scenarios, line capabilities and transfer capacities may need to be increased to accommodate increased demands for wheelina. The uncertainties associated with planning problems wo-ald increase u the number of entities involved in wheeling increased. These would be incremental increues in the technical problems associated with plannin1, opentina, and system en1ineerin1. In the last scenario the entire system is operated on the buis of transactions neaotiated with the various parties. Tnnsmission system schedulina may replace the economic dispatch of generation u the primary control mechanism for the independent transmission companies. They will need to devise control schemes to accommodate the numerous short and Iona term arnngements for delivering power from multiple, independent services to the purchasers, over transmission systems -1-21-
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Power Tecbaoloaln, lac. with limited capability. Coordination or operation between interconnected trammilsion networks may play an even anater role in Scenarios 4 and 5 than it does at present. -1-22-
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Power Tecllaoloaln, lac. CIJAPJIIP
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Power Ttcllaoloaln, lac. CHAPTIRl NIW GINIRATION SOURCES 2.1 ACCOMMODATION OF NIW SOURCES UNDER EACH SCENARIO Each 1c:11Wio raises III increuin1 number of technical problems u the conditions postulated depart further from the existin1 industry sttucture. The increasing freedom of trammillion acceu ud levels of wheelin1 required are accompanied by an iDcreaed Dumber of entities participatin1 in the supply of 1eneration. The coaditiom or oacb 1eenario releVIJlt to the expected new sources and associated teclmical problems related to tbe new 1eneration sources are summarized below aloaa wida III introduction to tbele problems. 2.1.1 Coatl oa Sceurlo I New Soarcn ud Related Techalcal Proble111 Ana The rant acenario does not envision uy drutic cban1e in the industry structure. Noa-utility 1eneration would continue to be developed under PUllPA and IPPs would be allowed to enter the market. New, non-utility puration sources expected, include the existin1 pattern of QFs IDd may also iacludl larpr unics constructed by IPPs specifically to enter the market. The dilpatcbabWty, operation, aad control of non-utility aeneration and tbeir effects OD syttem COltl will become more si1Dificant to more utilities if the level or dais type or capacity OD the systems increues ud is more widespread. Tbis also increuel the uncertainty in 1eneration plannin1 since the independent, DOD-utility aeneration tbat is planned frequently bu not materialized and there is concena oa the pan or utilities about the lonaevity of these new sources. T. tlelmical problems exiltina in today's systems would not be seriously changed by th1a acenario, altbouah their frequency would be expected to increue as the number of DOD-utility sources increased. The mechanisms for implementing solutiou would remain since system plaDDina. operatin1 ud en1ineerin1 functions r -2-1133
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..._T ...... 1ac. WOllld be balically atilicy r11POmibilitils, except ror tbe operation of non-utility ....... 2.1.2 Scnarle 2 TIii IICODd ICeDllio allo laves tbe vertic:ally iDtepated utilities iD place and does aot altlr die sinaatioa reprdiD1 tbe eatry of aew aeae,atioa sources. The mix of .... DOll-lltility ..-,llioll would be die IIIDe a in Scenario 1. Acc111 to die I"'- syltelll ii npaded by allowiq menctarory wbeelina for boG ldilitill ud larp retail CllltDmlfl (i.e., retail w11eeliq iD die Nase used ._.,_ n.. retail .,._liaa UUIICbOal atrect die l)'ltnl control since the TY1111iaa ldility woald wd to .....,._ atid'actory tenm ud conditions for dftpaldiaa, coauot. 111d ectby nwa ror coatncts between me 1eneraror an
PAGE 205
Power Tecllaolosln, he. New pneration requirements, planned by the utility's staff, would determine the type1 and sizes or tbe new sources. These would be expected to span the complete nap or existina, utility owned, roail rue~ and hydro aeneration u well as the new sources expected in the previous scenarios. ID addition there will probably be GENCO. establisbed to own and opente existing, or u yet ummished, light water moderated nuclear plants comtructed by utilities. J1C1t1lql PmNw The major tecluucal problem area would be in l) tbe scbedulina of aeneration and trammiaion, 2) economic dispatch, and 3) AGC areas. They result from the arowth of noa-utility paeration aad the iDcreaed wbeelina tramletiou. The new paeradoa would supplant the emtin1 (ie., old") pnention after some time and tbe scbeduJina ud AOC problems would involve a much biper portion or non-utility paeradoa plus utility paeradoa that may be located ia iaterconnected utili~ syslellll. Ia the Iona term this scenario evolv to the conditions or Scenario 4, with all of the aeneralion owned by independent entities. Teclulical-ecoaomic questiom that arise iD system planning, opention and control as a result or these new sources include the followiaa. o How do tbe systellll obtaia new resources required for reserve purposes rather tban eneru production? o When wheeled power and non-utility pneration form a laraer portion of the system paeration, what form does the economic model take for the system uait commitment and economic dispatch? o What type of COits and economic models are involved in compemadllg pneratin1 entities r or providina controllable VAR npport, replatin1 duty and spinniD1 reserve service and controllable paeration for stability, security and b'UIIIDissi>n system dispatch purpow? IUJ111t1gg1 Prp1p1,.. Boda Scenarios 2 ud 3 contaia technical problems that are related to the institutional arranpments a well II to the new sources. System dispatch could r 1~5 -2-3-
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Power Tacllaoloal, lac. still be done on the _current economic buis with some modification for the new source pnention contnletl and their terms. MaraiDal opentina costs for pnention would ntain essentially the same meeain1 that they have currently. The dispatchin1 of individual systems and power pools, mechanisms for arranging economy intercban1e tramactions and the operation of power brokers could all continue u at present. 2.1.4 Sceurlo The penultimate scenario extends the competitive market to include all generation supplies required, both old and new. Integrated utilities are 1one from the scene. Independent GENCO. compete with IPPs for all supply contnctl. Transmission and distribution functions are retained in utilities, T&D Cos. for a combination company and TRANSCO. or DISCO. if separated. The TRANSCO (or T in the T&D Co.) hat responsibility for system reliability, and it is usumed that the TR.ANSCOs are usiped the responsibilities for system opentions, 1enention and transmission systems' scbedulia1 and system engineering. System scbecluliaa 111d dispatch are to be performed under contract terms between genenton and TAD Cos. or retail customen. Retail wheelin1 is voluntary and so is not expected to affect operations u much as in Scenario 2. New pneration sources would have tbe same type and mix pattem u in the previous scenarios. Exiltin1 utility generation would initially constitute the vast majority of the pneration capacity. Customer determined needs would dictate the expansion of the system. New IDd specif"JC technical problems arise immediately in the 1enention scheduling and control area. The TRANSCO must establish meam for ensurina a nliable pneration supply ud for scbedulin1 generation to meet load demands on a secure bail, requiria1 a new approach. Existin1 unit commitment schedulin1 methods will require modif"atioa. 1~6 -2-4-
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Power Tecllaoloala, lac. EutiDa methods minimi:re total system opentina costs r or the entire array of units. Schedules are developed for the economic benefi: of the whole system, not for that or any particular wlit or plant. With divided ownenhip of the genention the economic scbedulina or genentiou becomes an entirely new problem where each party ha an interest in mxiraizina bis own benefit. The same teclmical problems arise in Scenarios 3 and 4 except that they would occur more rapidly iD 4. The shift in responsibility for establishing adequate pneratioa capacity reaerv arises in 4. The establisbed pattern of pneratioa scbedulina and economic dispatch by present intepatld utilities would be replaced by one that involved the usianmeat of the responsibility for system control to the TRANSCO iD both 4 and 5. Teclulical problems in this sceauio an also expanded by the requirement to make additiollal specif"'ic arraapmeats for adequate voltqe control. The TRANSCO would have to develop meam r or lfflllainl Uld implementing the economic control of VAR pnentioa. spiDDina reserve service and pnentioa level adjustments for security and tnnsmiaioa system scbedulina. With the pneratioa schedules bued oa the supply contracts, the current meaniaa of system incremental production costs may be lost. Whea contracts between sources Uld CllltOmen an the major part or the resourcei beina scheduled, the goal of dispatchina pneratioa sources to achieve a Wliformity of marainal production costs tbroupout the system may disappear. Schemes with the aoal of schedulina pneratioa to satisfy tbe coatnct requirements, observing the limited transmission 111d security comtraints, will become the new fnmework for aeneration dispatching 111d control. Economic dispatch 111in1 incremental coats miaht only be done by GENCOs and IPPs for aroups or units Wider their individual control. 187 -2-5-
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Power Teclaaolct1les, lac. Tbe possible loa or_ the current commonly accepted meaning or system-wide incremental costs also bu tbe potential for upsetting current contracts for energy purchased by utilities under avoided cost contract terms. TRANSCOs require the ability to monitor and control all or the generation resources. System openting control center software would be redesigned so that power could be transmitted for other parties or brokered by the TRANSCO. Transactions costs, meterina requirements, billing system complexities, and computer resource needs will all increase. TRANSCOs will control AOC systems to ensure the maintenance or constant frequency and control intercbaqe schedules. This function will need to be expanded with the increue in new sources. The effective number or control areas may have to be chanaed dependina upon the nature or the various contracts and the. extent or TRANSCO service areas. The removal of the intearated utility from Scenarios 4 and S introduces difficulties in attackina system enaineeriq problems such u stability. subsynchronous resonance, low frequency power oscillations, and both emergency and post emeraency restoration planaina and operations. Means will be required to ensure cooperative efforts to expedite and implement solutions to prevent the degndation of system performance that could be caused by the lack or a timely cooperative effort. For example, low frequency system power oscillations may be due to the interaction of the system controls, the electro-mechanical parameten or the generation systems, and the particular electrical properties or the transmission system. They may be initiated by electrical transients caused by major load 1witchin1 actions. In u environment such u posed in Scenari01 4 and S responsibility for seekin1 and implemeatina solutions is divided among numerous, independent 1eneratin1 sources, traumiaion companies, ud the customer oraanizatiom. This division of respomibility could lead to chaotic system conditions causin1 frequent system sepuatiom and interruptiom. Institutional arranpments under Scenarios 4 and 5 must be made to prevent this. Arrangements must be such to ensure that some ,.. -2-6-188
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Power TecllaoloSln, Ille. oqanization, probably_ the TRANSCO, has the responsibility for system-wide ~n1ineerin1 and that all other ""IIDizations are required to participate in the required solutions and implementations. 2.1.5 Sceaarlo 5 The last scenario opens trusmission access on a non-discriminatory basis for both retail and wholesale wheeling to all parties. The terms of the scenario require the complete separation of the utilities into GENCOs, TRANSCOs and DISCOs. The TRANSCOs are to be reprded u common carrien with the responsibility to provide for adequate transmission capability. ID order to make this scenario practical the TRANSCO would need to be usiped additional responsibilities and authorities in system operation and pl1anin1 and aaume a role similar to the one played in Scenario 4. The new generation resources and technical problems the same u those in the previous two scenarios. The non-discriminatory requirement to provide wheeling service is extended to apply to both aeneraton and Ddlil customen, reintroducing the opentin1 and control problems usociated with retail wheeling discussed in Scenario 2. All 1eneration planaia1 would be vested in contractual 1eneraton and DISCOs unless the TRANSCOs act as broken. agreements between The TRANSCOs are responsible for supervision or system operations and assume current and expanded control center functions. The nature of the technical problems would be the same u those in Scenario 4, but expanded to include those generation scheduling and control problems due to retail wheelin1. 2.2 SIGNIFICANT SUPPLY CHAllACTIRISTICS Generation supply characteristics are important parameten in usessin1 system control and dispatch. Economic operatia1 characteristics. control ranges, and 1eaeration response data are all important f acton. Loads chanae rapidly and aeaention must be capable of respondin9. Rapid response is needed to restore -2-7,.. 199
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Power Teclaaoloaln, lac. tieliDe nows after ro~ outaae events. Durina liaht load periods, the system may be required to shut down 1eneraton to keep aeneration and load in balance. Under the current arranaements utilities can control these characteristics by installing various typeS or units. The coordination of new generation characteristics with utility aeneration is one technical problem that requires attention, particularly in Scenarios 3, 4 and 5. In the rust two scenarios, the conditions posed do not provide a mechanism for specif yins new source characteristics. The existina array of aeneration will have to accommO'late whatever characteristics the new sources have. This is the situation in utilities presendy when QFs and coaeneraton have appeared. ID the Jut three scenarios, the mechanisms do exist to coordinate the new source chancteristics with eutia1 capacity. ID Scenario 3 the new source characteristics may be specif"'ied u part of the biddina process. The same is true in Scenario 4 as Iona a the TRANSCO bu the responsibility and authority for system operations and pJannina. All source supply coordination would then be similar to that expected in Scenario 3. This is a key question in Scenario S. The ac electric power system with presently available apparatus will not function correctly with proper voltqe levels and frequency un1ea the coordination takes place. For eumple, it would be chaotic to bave all bue load aeneration supplyin1 today's form or highly variable load cycles. Coordination will have to be the responsibility or the TRANSCO. Sufficient plant capacity must be available for frequency control and load following. The level or coordination required is that practiced in current utilities. The pneration system cbancteristics must be able to match the load patterns. Load followin1 must be done by some capacity. Suff"icient capability must be un~er AGC and capacity hll to be available to handle peak loads and outaaes or aeneration. Coordination or fuel supply requirements and other characteristics would be left to the market to be arranaed by contracts. ,.. 2-00 -2-1-
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Power Tecllaolopn, lac. The only other techni~ alternative that appears conceivable is to require sufficient load m1n11ement and direct load control to level the aeneration demand cycle. Even then some coordination of unit cbancteristics and control is required to handle aenention demand level changes due to outqes and fluctuations caused by non-controllable aenention output levels such u in solar, wind, etc., installations. Coordination of planned generation outages is not a serious technical problem when sufficient installed capacity reserves are available. In the different scenarios a number of different approaches to this coordination may be proposed. With mostly utility controlled aeneration the IPPs would be free of constraints. More non utility generation plumed maintenance schedules miaht be established by contract or a biddina process. Unplanned maintenance outqes must be considered in coordinatina maintenance outaaes a a random variable. The ranae of unit sizes and types of new sources in the various scenarios extends from smaller QF units up to the existin1 1000 MW nuclear units constructed by utilities. New f oail f"ued steam units would probably be limited to maximum sizes of 500 to 600 MW 111umin1 continued low load growth rates. Fuels expected for these new sources may be coal, 111, or even oil depending upon the fuel availability, price levels and regulations concerning fuel use and environmental control requirements. Small hydro units and municipal ref use burning plants are possible contributon to the new source picture. Coaeneraton with new plants would be expected to be combined cycle plants burning natural au because of their simplicity, shorter lead time requirements, and relative economic advantages. Cogeneration installations for laraer ref"meries and chemical plants may reach 1000 MW or more. IPPs may be induced to install au turbine peaking capacity burning natural gas. Sizes for advanced design units range up to about 130 MW currently. New source generation characteristics of importance in reviewina the technical problems usociated with the five scenarios are: 201 -2-9-
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Power Tecbaoloaln, lac. 2.2.1 0 0 0 0 0 0 0 0 heat rates and control ran1es, unit availability and expected maintenance outa1e time, response rates, fuel and environmental considentions, lead time requirements, Iona term plant availability of new sources, coordination of plant characteristics with utility, and plant location and transmission access. Heat Rates ud Coatrol Ruses Heat rates for steam units are important determinants in economic schedulin1 (i.e.~ dispatch) of systems. Under some scenarios it is probable that non-utility generation would be controlled economically along with existin1 aenention. Typical net beat rates and control ranaes for fossil fueled steam plants of various unit sizes and fuels are given in Table 2.1. Heat rates and control ran1es will vary dependina on plant desian, auxiliary systems and plant controls,u well u the unit's aae and condition. Heat rate data are all for the hi1her heatin1 values of the fuels. A 1979 EPRI report, "Survey of Cyclical Load Capabilities of Fossil Fired Generating Units, Report EL-975, Technical Plannin1 Study (TPS) 77-732, provides additional data on unit minimum load capabilities and reaulatina ranaes. These data are in aeneral qreement with those on Table 2.1. The survey shows that the exact characteristics depend to a areat extent on plant designs, boiler type.and boiler control systems. Liaht water moderated reacton have typical full load net beat rates of 10,400 Btu/kWh. Control ranaes of nuclear units extend down to approximately 20 to 25 % of maximum capability. It hu not been the practice in U.S. systems to operate ,.. -2-10I)(&') I..,; ,c.,
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Power Tecbaoloaln, lac. these plants u load ro}lowina units. This is apparendy due to the lack or need to do so, since the percentaae or nuclear capacity is not larae, plus the reluctance or nuclear plant ownen and operaton to subject the units to unnecessary power excursions. TABLE 2.1 Typical Foull Geaeradoa Ualt Heat Ratn Unit looq& 804M 60CM, 40% 25% Foail Ratina Output Output Output Output Output unit-description (MW) (Btu/kWh; (Btu/kWh) (Btu/kWh) (Btu/kWh) (Btu/kWh) Steam--coal 50 11000 11088 11429 12166 13409 Steam--oil 50 11500 11592 11949 12719 14019 Steam--ps 50 11700 11794 12156 12940 14262 Steam--coal 200 9500 9576 9171 10507 11,11 Steam--oil 200 9900 9979 10216 10949 12068 Steam--ps 200 10050 10130 10442 11115 12251 Steam--coal 400 9000 9045 9252 9783 10674 Steam--oil 400 9400 9447 9663 10211 11148 Steam--ps 400 "400 9541 9766 10327 11267 Steam--coal 600 1900 8919 9265 9143 10114 Steam--oil 600 9300 9393 9611 10216 11300 Steam--ps 600 9400 9494 9715 10396 11421 Steam--coal 100-1200 8750 1803 9048 9625 Stelm--oil 800-1200 9100 9155 9409 10010 Stwn--au 800-1200 9200 9255 9513 10120Note: Points noted with an asterisk are outside or normal control nnae. Source: Chapter 2 or "Power Genention, Operation and Control" A. J. Wood and B. F. Wollenbera, John Wiley and Sons, Inc. 1984 Plants usina combustion (i.e., gas) turbines have typical heat rates as shown on Table 2.2. -2-11-
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Power Tecbaoloaln, lac. TABLE 2.2 Typical Gu Trblae Plut Heat Rata Heat Rate Plant Type (Btu/kWh) Industrial Existing 13,600 Advanced Desian 9,SOO to 11,300 Jet 16,000 Combined Cycle 8,500 These data are also for the hiaher heatina value of the f uela. They are also approximate, particularly for combined cycle plants where the efficiencies are very dependent on the cycle desian. Control nnaes are from 20 to IOOCN, of rated capacity. Combined cycle plants in modern coaeneration plants are operated to meet steam demands. The control range at a aiven steam requirement operatin1 point is very limited: exact ranaes depend on the specific desip. 2.2.2 Malateauce ud Uaa,allablllty Charact1rl1dc1 The overall availability of generatina units affects aeneration system reserve requirements and operatin1 economics. Table 2.3 shows typical maintenance and forced outqe experience for various typeS and sizes of units. ,. 204 -2-12-
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Power Tecbaolo1l11, lac. TABLE 2.3 Typical Malateaaac, u Forced O.tqe Data Unit Type Size Ranae I Maintenance Requirements Equivalent Availability (MW) (D tv/YNr\ Forces Outaae Factor Rate(%) (%) ... _. 1...41 u .. .... Total Nuclear All 63 9 72 16.7 68 crs All 11 6 17 --90 1-99 25 7 32 10.5 SJ Foail Fueled 100-199 36 9 45 9.5 SI Steam 200-299 41 s 49 9.4 79 300-399 41 s 49 13.1 79 400-599 39 7 46 9.6 76 600-799 43 5 48 12.0 78 ~oo 43 7 50 10.4 81 Table 2.3 Notes: 1. Equivalent Forced Outaae Rate is (Forced Outqe Houn + Equivalent Forced Derated Houn) divided by (Forced Outaae Houn + Service Houn), both taken for the same time period. 2. Availability Factor is the ratio of the houn the unit is available for service divided by the houn in the period. Source: NERC Equipment Availability Report 1985 2.2.3 Ualt R11poue Ratel The power systems' chanaina load patterns, the need to participate in frequency rqulation, and the need to be able to respond to emeraency and other special r -2-13' I' -,I L ''\
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Power TecbaoloSln, lac. situations that arise on_ the system, all lad to nquiremena on 1eneratin1 units r or clwlaiaa load. The key meume of a unit's ability to respond to these requinments is its response rate expressed ill MW /mill or in percent of rated capacity per minute (%/min). Genentiq units 1enerally have the capability of respondin1 more quickly over limited excunion nnaes for shorter time periods. Fiame 2.1 illustrates the power system response requirements, shows the various time periods involved ill various system requirements,and provides a way in which to cbarlcterize a puticu1ar unit's performance characteristics. Note that the scale is Jo1-lo1. The horizontal scale is the required time interval. The vertical scale is the response rate in Cl MW per minute and the diqonal lines connect poina that have identical excuniom. The points labeled A and "B on the fiaure connect performance puameten for small and Iara excuniom for a sinale hypothetical unit. Source: 1000 DAU LOAD Ill i I a-,..;~~----~r-----itr-----.... I 0.1 .......... ~----...... -~-----_.~--~ 10 MNITII PIIII0IIM LOAD F11an 2.1 Power S,ate Rapoue ..... ,. ..... Rei,,...tadH MW Respome of Fouil Fueled Steam Units, IEEE Paper TP 72 633-6, IEEE Workin1 Group on Power Plant Respome to Load Chan111, Presenttd Sept. 1972. ,.. -2-14-
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,..., Tecllaolesl, lac. Ullit commitment duty_ ii taken u any cbanae required beyond 60 minutes in the futm'I. Normal daily load followiq duty requires respoue betwttn and 60 miautll. Tbl blaic 1111d ii to meet normal daily load cycle requirements and ecoDOmic dispatch control sipals. Rtspoue rate requirements ran1e up to about 511/lllia for iadividual llllits even tboup daily peak load cycles seldom exceed rates or cllaap or 2' or daily peak load per minute. TIie AOC system dictated respoue lies between about 15 seconds and minutes. TILil i= tbl time period ill wbich it ii important to readjust tie line power nows to keep dllm below the DOnDal liDe limits. The rqion for normal frequency reautation ii betweea about 3 aad 20 seconds. Special needs are caused by power system 11abWty coa1idendo wlme llllill may be called upon to adjust load rapidly to wilt ill ltabilizin1 systam. 1'11111 requirements .,. aiva to l)l'INllt backaround for summ1rizin1 unit response c:hulc1ariltic data. Thlle data, obtained from published industry surveys, are Ullful iD lllldentaDdiaa the relative capabilities of various type1 of 1enentin1 units iD l'IIPODdiq to tbe DNdl for rapoue. A 196, nrvey, ~ower Plant Reapome: an IEEE Workin1 Group paper on power plut l'IIPODN to load cbana, presented tbe resulll of I survey of the rate of load cllaap ezperieoced IDd tbe respome ralel of various type1 of units. Results an llllllllllriad on Table 2.4. Tbe data sbown are repraentative or the median renlts of tbe survey ud are typical of current power plant response chanc11riltics. The 1979 EPRI survey report cited previously (EPRI Report EL-975) contains additioaal data coacerain1 respoDN nte chancteristicl. The resul11, in aenenl ..,_..at witla tbl IU'lier survey, show the variations in respoue rates due to boiler dllipa ud fuel type. -2-15-
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..._ Tma11..-, lac. Tabll2.4NOCIC TAaLl2A TJl)lalatlf!1llatel Upit IYPI Md 5a Bew Slam Ua.itl (all ) 10-50 MW 60-199 200 ad over Alls.ct Noa-reheat Rellt Hydro Ullitl1 10-59 MW *"960MW All Ua.itl widloat Call d111Ut1neomr11PODN Bcrnne Bate 4.1 '9/miD 3.1 ,,miD 2.1 ,,miD 4.2 ,,min 3.0 ,,min I to 6 'INCODd 4 to 6 .. /NCODd Aboat 5' of tbe units were desi1aed ror instantaneous IIIP(I-. TIie median capability said to be maximum iascatueoas nspo_. was SSCM, olratiaa-Median response rate 0.9 '9/sec I. TIie llydro 1lllit respow ra111 depend 1lpc)II die plant's net held, the type ol llydrulic hlrbille ud die ...... of die penstock. 2. a. blrbi8I IIP'I ,... Yll'J depndiaa apoa die delip of die puticglar ait. n.e dala illdicate that a rllPC)W rate of about 55' per miDIIII ii the mecHn val111. -Pon, PIiat Respow,IEEE Workiq Groap OD Power Plut llelpome to Load Ote..,., IEEE Piper TP 65-771, 1965. ,. -2-1,-
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Power Tecbolopes, lac. Naclelr power plant response rates have been surveyed by CIGRE Study Committee 39 IDd published in PC 15 OJA for a Study Committee 39 meetina in Toronto, Ceneda, held September 16-21. 1915. TIie survey covered units throuabout the world. includina all typeS of commercial power reacton. The results indicate that over of the reacton represented in tbe survey utilized normal loldina rates betw 4 ucl s-./miaute. One coaclusion that may be drawn is that utilities with laqe coacentntiom of nuclear power pluts are aenerally able to use these plants for load followiq ad repladq duty. The dala were DOC reported by couatry so that it is aot f asible to extract specific aameric:al dala CODCel1WII tbe respome rates of liaht water moderated reacton in die U.S. However. in a 111blequeat report of thil same CIGRE Committee (Cycling of Nadear Power Pludl To Meet Grid Operational Requirements: for a meetina of dais poap Tokyo. Japu OD October 27-21. 1917). the situation in the U.S. reprdiaa nuclear reactor power plaat operations WII IUIIUIIUized a follows: 9()peratina ltl'ltlliel in the USA llave, uatil ncendy required NPPs (aaclelr power plats) to operate in a bale-load npme only, althouah _, atilitiel have .. ppd in 11111 on naclear plant in a laid followina ud anentio cycliaa reaime ... caraeady pnention cycliaa (100 65100.) is reported to be a replar occurrence with its BWRs and early PWRa. AGC ii also implemented on NPPs by CE (Commonwealth Eclilon) but only ial'requendy ... at tbe present time the Tuk Force is maawan of puticaJar aaits intended for boltina AGC. 2.2.4 .. 1 ud la......_tal Co..W.radou The new sources would be expected to have the same concerns over future fuel availability ud price levels a exiltiaa utilities. Reaulatiom applyin1 to new source fuel 1111 shoald be tbe 111118 a thole for the utilities. Natural Pl f"ued aeneraton CODltl'IICted for copneration enjoyed a fuel source advutqe denied to utilities. Lona term availability. price levels. and price stability of fuel resources are IIDkDowm for both utilities aad non-utility aeneraton. It appears that coal raoarces are plentiful for the lonaer term. Natural au is cumndy in abundant supply. but it is aot clear if this situation will penist in the Iona run if a larae portion or new aeaeration sources are fueled by ps. ,.. -2-17-
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Oil availability and all_ fossil fuel prices have been tied together by the market and sapply men1pment ICtiom or OPEC. supply with fairly stable price levels. Currendy oil appears to be in abundant Since the U.S. is dependent upon imponed oil for a larae part or its requirements, Ullf'oreseen world events have the capacity to rapidly upset the market. Fuel price levels bave been volatile since the early 1970's. Lona term fuel price forecasll have been somewhat ioaccurate u a consequence. Therefore, it is probable that new source aeneration will be secured under terms that allow for fuel price adjustments ill tbe price of IPP delivered eneqy. Environmental considerations and naulations have affected new 1eneration costs and fuel selectioD. ID tbele ICellal'iol it is to be expected that any such considerations, reqairemeats for control and restrictions would apply UDif'ormly to utilitiesL GENCO., and IPPI. Tbe put impact on utility system plannina bas been the paenl movement to 111ill1 coal fuels for future plants. Environmental COllliderations and added COits for controls have somewhat dampened enthusiasms for coal The planner bas to make the choice amon1 fuels. Coal is ill abundant domestic supply. Prices are relatively stable. Environmental r.osts add to plant costs. On the other natun1 111 availability and prices are more uncertain, but au fired plats are mon environmentally acceptable without major added control costs. Oil availability and price levels are more ucertaiD. Environmental costs are higher thu for III and may evn lppfOICb those for coal. These considentiom will apply ill the future for all new source supplien. With pneration being supplied by IPPs ill some scenarios, ruet planning is decentralized and may lead to more gas fired capacity liDce this fuel appears to orrer the fewest problems. 2.2.5 1AM Tlae ... ..,. ..... Another factor affectilla plllmina and system development is the lead time required for new sources. Utilities have experienc:ed illcreuillaJy Iona time requirements. They race naulatory hurdles u well u the expected requirements for permitting r -2-11-
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Power Tecaolosl, lac. aad comtraction cycles. ID scenarios where new sources are removed from replation, plant lad times would be expected to decrease. The lead times would approach thole for current non-utility plant coutruction. Environmental rqulation would still exist and would be applied equally to all new 1eneratiD1 sources. Copneration plants have been planned. enaiaeered and constructed in 2 to 3 year cycJes or lest for smaller sized pluts. Utility construction has aeneraUy been loqer, nnama from 5 to 6 years or more. With tbe low arowth rates or load in recent yean, lonaer lead times have not resulted in lhonaps or p-..eratina capacity. Wbea requirements for new sources lrile, plaania1 mould be performed sufflciendy in advance to allow selection out of 111 array oa poaible fuel supplies and new source entities (dependina, of course, on the scenario). Without suff"1eieat leld times the choice may be restricted to oil ot Ill ruec1 plants 111in1 combustion turbines. These plants aenenlly have much sbor1lr comtructioa cycles since the waits ue factory usembled 111d do not require extelllive fuel hlndlina equipment, boilen, 111d plant control systems. New source lead times interact with lead time requirements for needed transmission coDltrllCtioa. Non-utility aemraton D"8d to coordioate plus with the utility or TRANSCO to make certain tbat trammiaion will be available on time. Transmission leld time requirements ue hiply system IDcl site specific. 2.2.6 Loaa Tena Aallaltlllty of New S..rces The concem with Iona term availability of new sources is primarily with those to be supplied by QFs and coaen'!ftton. GENCO. 111d taraer IPPs supplying generation could be bound by Iona term contracts. QFs and copneraton may or may not be u Jona lived u put utility generatio~. QFs may f".Uld the business unprofitable if avoided utility costs and their revenues decline. Copneraton may experience economic downturns and curtail the plant operations with short notice to the utility or TRANSCO. -2-19-
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Power Tecbolosl, lac. Tbeu are probably mnpable uncertainties in reasonable quantities, but many will usue over the def"mition of reasonable qURDtities. An increase in uncertainty level means that aeneration capacity reserve levels will have to be adjusted upwards by utilities or TRANSCO. and DISCOs to cope with the uncertainty. ID Scenarios 4 and S, the responsibility for obtainina sufficient reserves to ensure reliability is usiped to the purchasen. The mechanisms for obtaining the required reserves are not clear. Utilities with nuclear capacity actually face the same sort of uncertainties. Unforeseen events cause new reauJations to be applied to operatina plants causina Iona time outaga. The delays in developin1 Iona term means for handling nuclear plaat wate products could conceivably result in future plant shutdowns and even ntirements ahead of schedules. 2.2. 7 Plut Locatloa aad Tnualuloa Accaa Plant locations and the point or accea to the transmission system are system and site specif"JC. Tl'IDlmiaion access should be at subtransmiaion or higher voltage levels to avoid ca111in1 exceaive technical problems in the distribution system, such u blckfeed, excessive short circuit duty requinments, etc. Connection at major substations, or the collltnletioa of new stations t or near new source locations, will facilitate the installation of required bra.ken, protective systems and meterina and communication equipment. If poaible, new source sites should be located near exiltina major substations which may be expanded. with trammission facilities that have sufficient capacity for deliverin1 the power. If not, plant locations and transmission expansion plans require coordination between new source eatitia and the utility or TRANSCO. 2.3 CONTRACl'UAL AllllANGIMINTS WITH NIW GENERATION SOURCES AND IPRCI'S ON SYSTEM OPERATION AND INGINIIIUNG Tbe tecbaical area of concern in contracts between new source entities and utilities or TRANSCOs are: 212 -2-20-
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Ponr Tecolosln, lac. 2.3.1 o scbedulina Uld dispatcbability of pneration, o AGC system control or 1enenton. o the economic structures for service in providina. 0 0 1. capacity reserv. 2. V All scbedulin1 for voltqe control. 3. system security scbedulin1, 4. tnnsmwu,n system schedulina. ,. eneqy, coordination of bulkpower !ystem plannin1, and coordination of implementations to solutions to system enameerin1 and teclmical opentin1 problems. Sc .... u., ... Dla,atc ... lllty Contrletl need to allow system operaton to control the dispatch of a sufficient portion or total paention to follow load cycles and control traumission flows. Lick or control or suff"JCient pneration could lead to 1eneration-load imbalances, mon requent system separation. and gready increued levels of inadvertent iatercballp. Unit commitment and pneration maintenance schedulin1 will both need to_ be covered under the contracts to allow the system control center to schedule suff"icient paeration to cover spinnin1 reserve requirements. Minimum load conditions may require units to be scheduled off line. A solution is to require all new source contracts to allow schedulina of aeneration in a unit commitment conducted by the utility or TRANSCO and to allow restriction or a portion of the capacity towards spinnin1 reserves when necessary. New sources with non-schedulable plants (e.1., some coaeneraton) would be excused, but miaht be required to purchase an equivalent amount or operatina reserve capacity as a condition of access. ID the scenarios with the majority of generation controlled by utilities. current practices can initially be extended. Non-utility 1eneraton have freedom to schedule their own rmources. At some point in the arowth of non-utility capacity the dispatchina and schedulin1 difficulties must be addressed in contract terms. When r -2-21-
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Power Tecbaoloaln, lac. the new sources increue to the point where the minimum load level commitment and dispatch are constrained. contract arranaements should allow the scheduling of new source aeneration. The terms and rate structun for allowina this will need to be addressed in the contracts. ID Scenarios 1. 2 and 3, aeneration scheduling and dispatch might be done under economic terms of contracts. Under Scenarios 4 and S (and ultimately under Scenario 3 when the new sources displace utility 1eneration) the situation is different since all 1eneration is new source. Contnct terms will need to allow the TRANSCO system operaton the ability to schedule sufficient units to follow load cycl and meet security, spinning reserve requirements, and transmission constraints. Contnct terms will need to be set for scheduled maintenanc~ outaae coordination ill order to ensure that there are adequate 1eneration reserv available throughout the year. Solution methods could involve the TRANSCO actin1 u a broker of reserves. Each new source would be oblipted by contract to supply capacity and reserves. When units wen unavailable due to planned outaaes. maintenance outaae caused by failures. or by forced outaa. the 1eneration supplier would be obligated to purchase reserv with the TRANSCO actina u a broker. Another solution would be to have all supply contracts directly between sources and DJSCOs. and retail customen carry an obligation that the source furnish or purchase reserves. Maintenance scheduling would then be left to individual new source entities. In all solutions the TRANSCO would act u a coordinator. keepina track of available capacity, reserve obliptions, and usistina in makin1 arranaements. Present economically determined participation in load followin1 may be replac:ed by specuac contract terms definin1 the operatin1 control ranae and the level of parti:ipation for each 1eneration source. Some units may be base loaded, essential ,.. -2-22214
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Power Tecllaolopu, lac. orr control, while othen may be scheduled off line at low loads and have their output levels controlled when online. Retail wbeelia1 contract terms may be desi1ned so that the supplier is required to dispatch bis 1eneration on the basis or the purchaser's load cycle including spiaaia1 reserve requirements. The supplier could maintain his own control center. but the TRANSCO would require monitoria1 capabilities and the authority to order 11neration cban1es for system security and in system emeraencies. The arran1ements may be similar to those in the current NEPOOL system with different levels or control (i.e., a hierarchical control system structure), with the TRANSCO takia1 the role currendy played by the rqional control center (i.e., the New Eaa1and Power Exchan1e, or NEPEX Center) and the generatia1 entities acting similarly to the current area control centen. Dirr erent independent powei:. producen would be scheduled by the TRANSCO to provide total 1eneration levels. The allocation and scbedulia1 or individual units mi1ht then be left to the IPPs. The major cW'ference between this 111d the arran1ement in NEPOOL is that the loads and 11neration area may not be conti1uous u at present. Net deficits of inadvertent iatercban1e would be purcbued by the source Crom the local utility. Rates would be set by contract terms. Other contract arran1ement1 between individual new sources and retail customen are possible. A supplier, for example, mi1ht be required to purchase reserves in lieu or allowin1 control for dispatch and schedulina. The TRANSCO miaht act as a broker ia this cue, arranaiaa terms between sources for this service. 2.3.2 AGC Systnl Coatrol of Geatrado Contract terms must addreu the subject of AGC system control of 1eneration. In the fint scenarios, control of individual new sources may be handled utilizing the current system of control areas, etc. Retail wheelin1 introduces new AGC related problems and contracts must address load f ollowin1 for specific customen, standby service and inadvertent interchange. Ia the lut scenarios, a global solution needs ,., -2-23-
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Power Tecbaoloala, lac. to be addressed with the definition of control areas and ties between areas requirin1 precise deimition. Contracts betwHD sources and purchasers would contain terms allowin1 for this aeneration control. The lick of tie line control, allowin1 all units to be merely on aovernor control of frequency with supplementary controls to restore set output levels would mean that all 1enerators would attempt to restore frequency in any imbalance between aeneration and demand. The increased frequency or unit output level adjustments would become intolerable to plant operators because or the potential dam11e to equipment, increased levels of unavailability, and the reduced lifetime of the equipment. Tie nows and inadvertent interchanae levels would rise without adequate capacity under AGC control. The terms for bandlina inadvertent interchanae and AGC system 1eneration control are closely related. The implementation of coordinated AGC system controls, similar to those currently existin1, may allow the continuation or the repayment or inadvertent eneray in kind (i.e., MWh for MWh). This is more likely to happen in the f"ust two scenarios umina a modest level or retail whlina. In the last three scenarios the number of aeneratina entities may become so tarae that contract terms will have to address the subject of inadvertent interchanae payments. 2.3.3 Ecoaoalc Stnctlln for Operadaa Coatroll Currently utility aenerators provide VARS r or volt11e control, provide spinning reserve capacity, are rescheduled off-economy for security and transmission loading adjustments, u well u supplyina power and eneqy. Under the first two scenarios they could continue to do so, with new sources supplyina primarily power and eneqy. Contracts for new sources may carry requirements for allowin1 scheduling IDd dispatchina. Economic terms for these services will be set by contract provisiom where needed. Voltaae control issues should be addressed in all the contracts by allowina the system control center the option or specifyina aenerator VAR levels. ,.. -2-24-216
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Power Tecbaoloala, lac. ID the later scenarios,_ the contracts need to address all of these areu. Economic meuures of the worth of these services have to be established to allow the system openton to control the system properly. This is a technical-analytical issue that does not have a current solution. It is not an euy ar to address. In atablishina contracts, quations of the value of these services need to be addressed at the same time u the technical problems associated with the lack of control are considered. The 1eneratin1 source entities and purchllina entities are bound toaether by the trammiuion system. The intearity of this system and its proper operation depend on the actions of all parties. Theref on, there is a hip dearee of mutual self interest involved in preservina the system. For eumple, if aeneration source opentiom must be curtailed because of improper voltaae conditions caused by lack of system-wide coordination of aenerator VAR schedules, all parties may suffer. Controllina aenerator V ARs control really does not affect the operating costs of the aeaentina entity in any material way. Payment terms may not be required in contracts. Contract terms with new sources should atablish the basis for settina the economic worth of providina capacity reserves and allowina aeneration output levels to be controlled to aid in system security and transmission dispatch. In these areu the 1enentin1 entities still have a self interest in preservina transmission system intepity, but they allo may suffer economic penalties if levels of their energy production must be reduced. Contract terms should address the establishment of an economic structure that allows for necessary output level control. 2.3.4 Coatract ProYlslou for Coordlaadoa of Bulk Power System Plaaalaa Bulk power system plannina involves both the aeneration and transmission systems. In the fint three scenarios the vertically intearated utility remains and can continue to coordinate plans for both of these subsystems. In Scenarios 4 and 5, there is no sinale coordinating 11ency. Contractual terms will need to establish means whereby the TRANSCO can participate in aeneration r -2-25-217
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Power Tecbaoloales, lac. plannin1 a well u tbat for the transmission system. The ultimate responsibility r or 1eneration plallnin1 under these scenarios rests with the user orpnizations, but a lack or coordination between usen, 1eneraton, and the TRANSCOs could easily result in the development of inadequate transmission systems. At the least the TRANSCOs should be involved to the extent of beina given an oveniaht responsibility in all bulk power planning matten. 2.3.5 Coatnct Prolalou For Resoldoa of Systea la1laeerla1 Aad Operatlaa Tecbalcal Proltle111 System enaineerin1 and technical operatin1 problems involve both aeneration and trammiaion systems, and perhaps even the distribution system. They include such problems a system stability and dynamic problems, the resolution of the need for new VAR sources and controls, emeraency operations, etc. ID the rust two scenarios the utility remains and has the responsibility for seeking solutions. Implementation may require contractual neaotiations with new sources and customen under retail wheelina contracts to cover VAR controls, excitation system modifications, participation in emeraency operations, and power factor correction in load areas. In the lut three scenarios the contract terms must be broader and must address the responsibility for seekina solutions to these problems. They must establish the buis to usian responsibilities and costs for needed implementations. An example is the solution of system stability problems. The TRANSCO's enaineerina starr would be responsible for detectina the problem and seeking solutions. The potential solutions may involve installina stabilizen on aeneraton, lddina controllable VAR supplies on the transmission system or in the load areu, modu1eation of the aenerator controls, fut run-back of aeneration levels, addition of series capaciton, etc. The selection or the proper method of solution and the responsibilities and costs for implementina the solution require attention in contracts. r -2-26218
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Power Tecbaoloaln, lac. It will prove impossible to roresee all or the specific problems that need attention. Certain areas such u emeraency plannin1 and operatina procedures clearly need to be lddressed in contracts while other area are less specific. The contracts should tablish the mechanisms Cor resolution or unanticipated system technical problems. 2.4 TECHNICAL PROBLEMS AND ~IBLI SOLUTIONS The technical problem areu raised by the new sources involve: o 1euration scbedulin1, o puration dispatch and load followin1, o AOC system and frequency control, o paeratioa plannin1 and capacity reserves, and o solution of system en1ineerin1 problems. Each of these bas related sub-problems that are discussed below alona with sugested methods for solution. They are closely interrelated to the technical problems caused by increased traDsmission access and wbeelina disc~ in Chapter 3. Some overlap occun. This chapter views those related to the new aenention sources. 2.4.1 Techalcal Proble .. la New Source Geaeratloa Scbedulla1 These include maintenance schedulina coordination and schedulina of units for spinnin1 reserve (i.e., unit commitment.) The relative importance of these are related to the particular scenario u discussed above. A sianiricant and difficult technical problem is that of schedulina new source 1euntion to accommodate load cycle variations and the need for adequate spinning reserve mar1ins. ,. 213 -2-27-
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Power Tecllaoloal, lac. Spiania1 reserve duty .could be 111iped to all sources of aenention on an equal bail. Supplien with a fleet of units could atiafy the requirement in whatever way they wished. SiDaJe units would have to be operated below maximum IOldiD1 limits which allow for spiDniD1 reserv. The TRANSCO requires monitorin1 and communication equipment to insure that reNrve requirement obliptiom are beina met. Another solution would be to develop an economic model which allowed the system openton to cost and purchase spinnina reserves from sources. Genentina sources not participatiDa would be allocated these costs by the system control center. Scbedulin1 units on and off line in unit commitment schedulina ii a more difficult technical problem that ii related to contnctual arran1ement1. With a few new source aenenton the ript to schedule a unit by a utility miabt be purchased unde~ contract terms that provided, for eumple, payments baed on what the new source supplier would have received it his unit bad been allowed to opente. Utility schedulin1 software would reconstruct aenention patterns and compute payments to the aew source. This would be an economic penalty iD utility unit commitment determinatiom and would allow system openton to make an economic choice between sbuttina down a new source supplier and allowiD1 him to continue opentina. New source sbutdowm would then only occur when required to mnt utility unit opentiD1 restrictiom. Shuttina down a new source enpaed iD retail wheelina to a specific customer would entail even more of a penalty to the utility if it is required to supply the replacement ener1y. With no iDtepated utility on the scene iD some scenarios, aeneration schedulina (i.e., unit commitment) bu an entirely cliff erent objective from at present. One objective of present schedulin!I metbodl ii to minimize ~tal production costs for the benefit of all of the utility eu1tomen. With no utility and a multitude of supplien and customen, pnention schedullna takes on some of the attributes of an OPEC meetiDa to tablilb market quotas in an attempt to manaae prices. Each OPEC participant ii seek.ins to maximize his profit and therefore bu an interest in -2-21-
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,..., Tecla......_, lac. blpiaa hit productio11 level hip. If tbe aroup does not cooperate in holding prodactioa levell down. tlae price levels may drop, reduciq the profit or the iDdividual partic:iputl. Tbenf'on, iadividual OPEC partic:ipantl may cheat on the ..,..mat to limit production ill order to illcreae their own reven1111 and profits. Tbe Ullit commitment problem with independent entities controllina aenerating IOW'CII is similv ill structure. It is a multi-party, multi-objective situation. Each 10arce atity will with to mJimize hit profit, but if there is no cooperation in ..-,adoa tebedalina, die system Uld comequendy their market will not function comedy. Tbenf'on, 10me 11111111 or 10lution bu to be found to coordinate unit IChedulll to provide lllf'racint c:apacity (or load followina and provide SPIDDlDI w-~ ldlqaata to ha!Klle unexpected load cbanpl and outqeS which suddenly l'IIDOft .. neratiaa capacity. 0111 poaible IOludon ii to require tlae laqer GENCO. and IPPs to provide the requind spinoina n11rv11 for tlae entire system 1111der the control or the TRANSCO. Other puticiputl could be cbaqed (or this service with payments nowina through tlae TRANSCO to tbe GENCO. and IPPs. Another approach would be to develop a new basis r or establishina unit commitmlllt bued on multi-objective fuaction theory ud trlde-orr techniques. This ii not a IOlution, but ii a sugestion for further analytical effort. 2 .t.2 Gneradoa Dll,atcla ud L ... Followla1 Praent pneration system controls establish minimum cost dispatch schedules based on illcremental production costs. Units under economic control are allocated participation ill demaad cbaqa on an economic buis. With a few new IOUICII the utility can continue this practice. Non-utility pneradon NCund under new IOWCI biddin1 could be required to participate as an -tial requinment for biddin1. Smaller QFs and IPPs could dispatch J\dependently. -2-2,-221
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..,._ Teclla1l11N1~ lac. Wida DO vertically iatepated utility ill the later sc:enariol, the technical problems wociated witb dilpatcbiaa are broader. TIie control center for the system needs medlodl 111d ecoaomic models ror controWaa v ARS. raerve service 111d reawatina daty, 111d for allowiq paeration clispalcb sllif'tl for security and trammission tclledulint-TIie baic economic ltnlChUe without the utility is similar to a zero 111111 pme" ia that these services are DICelllry for reliable system operation. but Ollly tbe pnentiq entities are puticic,atin1. Any costs and payment determinariom made by die TRANSCO control center ill sch.xtuliD1 and dispatchin1 mat oriainate from CUllds provided by these participants. Ultunately, of course. the COiii will be tnlllferred to die DISCO. and retail CUit.Omen. Wida.in die operatia1 control environmeat IOIDI bail for tbele COit tramfen must be foud. One solution would be to iacorponte provisions for recoverin1 these COltl ill die rates ror providin1 tnmmiaion service to tbe poentin1 entities blt the TJlANSCO. The Clllldl would then be reallocated amonpt the aeneratin1 entities compemadon for providiq these services. Any solutions will require additional hardware for monitorina 1eneration, metering eneqy flows, and communications to tbe control centen. Billin1 and control center tramletiom costs will increue. bardware will be required. 2A.l AGC 511.,_ Additional personnel, software, and computer Currnt AOC systemS woaJd be adequate in Scenario l. In Scenarios 2 and 5 the iatroductioD of retail wbeeliD1 on a taraer scale complicates the AGC problem in that die loads an ef'(ectively removed from the local utility service territory. Flowl into die load an sbnilar to intercbanp flows over tie liw. With a few retail wlleelina arnqementl, tbe current AGC system cu be expanded to ICCM11110dte dlese retail wbeelin1 contracts. New IOllfCII enppd ia supplyin1 power to the local utility may complicate the AOC system if tbe sources are located outside or the local utility control area. r -2-30-
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Power TecllaoloslN.,, lac. Their input into the system would be treated u a scheduled illtercbanae. If they ue imide tbe area, they may be treated u utility pneration for AGC purpo1e1. Ia later sceaarios, tbe AGC system concepts will probably need revision. The existia1 control ueu are deC"med on tbe buis of utility service area. These Vlllilb in later scenariol. They could be replaced by usill1 the TRANscos service territory to define tbe control area. All pneration within the 1eopaphic area woald be required to be under AGC control un1ea off-control operation (i.e independently C-J.Ud scbedulel) were allowed by contract or the TllANSCO operaton. System operaton could lllablisb sufficient pneration levels under AGC system control to maintain intercbaqe schedules between TRANSCO area. If TRANSCOs ue not tbe buis for redef"'miq control areu. tben source-laid coDfi1urations will be. Arm will be def"'med elecbically rather dwl aec,arapbically. Maiatwiain1 control over tie-line flows is essential to tbe operation of the illtercollMCted synems. If it is lost in any industry reorpnization, tie flows, loop flows. aad inadvertent illtercbanp levels will increase. ,.. flows must be controlled u all other flows mast be. to prevent the overloadin1 of the circuits and permit orderly transmission system scbedulill1. TRANSCOs must have tbe ability to control pnention levels to the extent DICllllry to scbedule tbe trammission system. Security must be maintained. 2.,... Geaendo ........ au Capacity ....... Utility plamlen cua use QF and IPP plants in determinina reserve requirements. Uacertaillties aboUDd with reprd to the actuality of these plants in the current sitaatioll. They would remain under Scenarios l and 2. Ia Scenario 3. the utility plannen will be in position to specify needed capacity to be bid on by GENCOs and IPPs. r -2-31-I)()') I I ',.
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Power Teclmolosl11, lac. ID the last two scenarios the TRANSCO staff would have ovenight responsibilities for securin1 adequate installed 1enention reserves. Two possible arran1ements appear f111ible. I. Tbe TRANSCO. provide transmission services and act as power broken. ID this cue they UIUllle responsibility for securin1 adequate aeneration supplies includin1 required capacity reserves. 2. The TRANSCO. supply trammiuion services only. 1eneration capacity reserves are then established betwn the pnentin1 entities and the DISCOs customers. 2.4.5 Sola& of Systea laaluerla1 Proltle .. Adequate by contract and retail ID tbe lat three scenarios, the responsibility for solution of system en1ineering problems would have to be established on the basis of contracts between all sources and the TRANSCO and DISCO. The TRANSCO would act as a service organization. GENCO. and IPPs would be required to participate u a condition of entry. Since tbe TRANSCO costs would be pused alon1 to both sources and load entities, the TRANSCO could seek minim1UD cost. technically effective solutions similar to the current basis for solving these problems. The typel or system enameerina problems caused by new sources include breaker short circuit duties, stability and dynamic problems, voltaae control, coordination and reliability studies, etc. The study and solution of these problems would be the responsibility of the TRANSCO's en1ineerin1 staff with coopentive efforts required by all entities. Solutions to these problems involve hardware and operating procedures. For example, stability may be improved by addin1 1enerator stabilizers, improviDa trammiuion systems, revisina plant control systems, usin1 fast run-back opentin1 methoc:11, lddia1 series capaciton, etc. Another specific system enaineeriD1 problem which must be addressed is that of the participation by all parties in emer1ency operations plannin1 and implementation. If a system is in an emer1ency state the TRANSCO must be in control or the r -2-32-
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restoration. The TRANSCO staff should uswne the role of current utility staff in emeqency pla1Ulin1, operations, and system restoration. The same conditions requirin1 participation in this system engineering area should be imposed on QFs and IPPs under the earlier scenarios. In these cases, the utility bu the lead role in coordinatin1 plans and procedures. 2.5 TECHNICAL ANAL TI'ICAL ISSUES The techaical problems railed by the new sources or aeneration and the contractual terma which may be required in non-utility 1eneraton include analytical issues which should be addressed prior to implementin1 any major industry restructurin1. This section recapitulates IJld IUIIUIWizes thou issues. Tbele are technical issues that are currendy either not sipificant because present indllltry procedlll'II are satisfactory or issues which do not have solutions applicable under conditions or some or the future scenarios. They should be considered prior to implementin1 the mon extnme del,WtUreS from the current structure outlined in Scenarios 4 and 5. They an all related to the non-utility 1eneratin1 sources. 2.5.1 S.C.rlty Bued Dlapatc The dermition or trllllmiaion capability, discussed in the next chapter, is related to the issues involved in the reliability criteria used in schedulin1 and dispatching aeneration. Security levels are cunendy based on wont case analyses that are desiped to avoid cucadin1 failures. An analytical issue raised by this, is the investiption of the appropriateness of this type of criteria. The occurrences of widespread system failures are so infrequent that no reliable statistical basis exists on which to jud1e the merits or this technique venus othen. An investiption or alternative methods would seem to be fruitful. Reliability criteria based on probabilistic analysis may off er a more uniform level of security and allow areater freedom in aeneration schedulina. This idea has not been carried over into practical application because of the success of current methods. r -2-33-
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Power Tecbaoloales, lac. 2.5.2 OYerall 1co,oalc Elf ects Tbe increued level of non-utility 1eneration and required wbeelin1 will affect the overall cost of 1enention. It ii not at all clear what costs would result since non utility aenention may not be dilpatcbable and may not be controllable under utility unit commitment schedulin1. In earlier scenarios, utility 1enentin1 costs may iDcreue if, for example, they must remove their laraer, more efficient, units during liaht load periods to allow non-utility 1enention to operate. An analysis of the potential ovenll economic effects could be accompanied by the analytical investiption or economic means for payina non-utility aenenton for the riaht to control or temponrily suspend their opentions r or economic dispatch and scbedulina. 2.5.3 Ualt eo .. 1t11eat Scbtdullaa As previously noted the unit commitment problem in the last scenarios is another analytical issue which requires attention. Present methods bued on minimum total production cost may not be suitable r or an environment with multiple 1enerating entities. New criteria and techniques need to be developed that will balance the interests or all parties and result in feasible operatina schedules. ID this same uea, an amlysis of the economic basis for payin1 new sources for the riaht to schedule their aeneration may also be needed. 2.5.4 Ecoaomlc Framework for Noa-Tradltloaal Gea,ratloa Senlcn ID the aeneration dispatcbina uea an economic framework for payina for reserve service, voltqe support services (i.e., VAR aeneration) and the ability to control aeneration for system security and transmission system schedulina is needed. Present dispatchina and aeneration schedulin1 methods do not consider these services. Costs for these non-traditional aeneration services an bom by the utility at present. Whatever non-utility aeneration exists is aenerally not scheduled by the utility control center under economic terms. ,. -2-34-
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Power Teclaaoloaln, lac. 2.5.5 AGC Sy1tea Desl1a AGC system alternatives should be examined and expected performance analyzed under various conditions. The current scheme, based on a clear definition of control areas, is expandable to include new 1enention sources under the fint three scenarios. The separation of the industry into seaments under the last two scenarios implies a tarae number of competina aenention entities and makes the deimition of a control area less clear. In theory, the control area could be defined in terms of loads and sources, but with very many parties involved, the proper functionina of the current desian of AGC becomes less clear and should be investipted to determine if current desians are appropriate under conditions of Scenarios 4 and S. -2-35-227
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Power Techaoloaln, lac. CHAWBW
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Power Tecbaoloales, Ille. CHAPTER 3 INCREASED TRANS~ION ACC~ AND WHEELING 3.1 WHEELING AS AN mUE Utilities aenenlly desian and use their transmission systems to deliver power from their own sources of genention to their customen. They also desi1n and operate transmission for economic interchanae amona utilities and reserve sharing. In power pools, power broker 111'1Dlements, and where interchanae transactions are arran1ed, the network provides wheelina for pool memben, external utilities and independent aenenton. Recall the deimition in Chapter 1, Section 1.1: "WbnJiPI The use of the transmission facilities of one system to transmit power of and for another entity or entities. There are subclasses of wheelina. Two given in Chapter 1 were: "Whotnale whglin -The wheelin1 of power and eneray for delivery to utility system. "Retail wbcclip -The wbeelina of power for delivery to a retail customer. Arranaement for the transmission of power 1enerated by a utility or non-utility aenentor to a local or remote utility is wholesale wheelina. The transmission of power from a remote utility, or a non-utility aenerator reaardless of location, to a retail customer is retail wheeling. These distinctions have technical effects. Retail wbeelin1 may effectively remove the load from the local utility's service territory, displacina local utility aeneration and effectively increasin1 the scheduled net interchanae by the amount of power wheeled to the retail customer. This definition of wheelin1 also includes simultaneous buy-sell transactions. These are very common. For instance, in 1986 one larae utility formally wheeled over 2 -3-1r 229
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Power Technoloaln, lac. million MWh but also JWheeled almost the same amount of ener1y under simultaneous buy-sell transactions. To put this in context, Consolidated Edison's 1986 sales to its customen in the New York City area amounted to about 30 million MWh. For convenience, three roles in wheelin1 are referred to: the seller, the wheeler, and the buyer. Often the same entity fills two of these roles, or several entities jointly fill one of them. 3.1.1 Wheella1 Pracdcn Most wheelin1 in the U.S. and Europe is a ne1otiated rather mechanical application of flat (S/kwh delivered, independent of mileaae) or posted rates. In many countries the rates and levels are not public. In the U.S., the structures and levels are flled with the Federal Eneray Reaulatory Commission (FERC), but there is. usually little indication of exactly how the conditions or numben were determined. ID Enaland, Parliament required that Enaland's CEGB (Central Electric Generating Board) provide posted or flat wheelina rates. This wu done, but they seem to be set at such a hi1h level that no wheelin1 is occurrin1. In New Zealand, the Labor 1overnment wh.ich took office in 1984 turned the 1ovemment-owned aeneration and transmission utility into a somewhat independent corporation. It hu construction, marketin1, and production business units which it considen profit centen. It treats the transmission business unit u a cost center and will facilitate access by competiton to its transmission system on fair and open terms (-Statement of Corporate Intent, Electricity Corporation of New Zealand, Limited: June 1987). As of early 1988, how this was to be done had not been defined. It is difficult to learn how the rate levels are determined because most are nqotiated in private. However, abroad u well as in the U.S., at the beainning of the raeaotiations: -3-2-
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Power Tecbaoloales, lac. o the wheeler -has some indication or its actual cost or wheeling, and o the buyer and seller have some indication of the value of the benefits they will receive r rom the wheelina. For wheelin1 to take place, the parties must negotiate a wheeling rate level which is above the costs and below the benefits. When all parties are re1ulated utilities, common r ormulas r or sharing the operating benefits of wheelin1 are: 0 0 0 A major wheelin1 handled. are: The wheeler has a fixed $kW or $/kWh (posta1e stamp) rate, and the buyer and seller share any savinp above that amount, or 1541 or the buyer and seller savinp are paid to the wheeler, or simultaneous buy-sell, where the wheeler buys at a price midway between its and the sellen' incremental costs, and sells at a price midway between its and the buyen' incremental costs. obstacle facin1 a wheeling utility in the determination of the actual cost of is bow the imbedded costs of existin1 transmission c~pital are to be There are many ways this could be done. Commonly observed patterns o if a firm service is provided, transmission capital cost is often included. o If an interruptable service is provided, transmission capital cost is not included. One fact about today's wheelin1 practices dominates all othen. It is that almost all wbeelina is voluntary and is to the mutual benefit of all parties. That is, there are enouah economic benefits to each transaction to allow them to be shared. And the parties trust each other, so to a great extent operate on the buis of gentlemen's a1reements which would be very difficult to enforce precisely. r 231 -3-3-
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Power Tecbaolo1l11, lac. 3.1.2 Dlffereace betwna Supplied aad Dell,ered Power The difference between what is supplied and what is delivered is a central issue in wbeelin1. Attributes or electricity include: Power (and its integral over time, energy): inevitable electrical losses occur when power is wheeled. (These losses are positive but incremental losses can be negative if wheeling reduces network flows.) Voltqe: this tends to fluctuate more, and less controllably, far from aeneratina units. VAR or reactive power is also absorbed or created by the tnnsmission network. Frequency: physics dictates that the fundamental frequency changes synchronously everywhere in an ac interconnection. But harmful higher-frequency harmonics can be created (by arc furnaces, for instance) or absorbed (e.1. by filten) locally. Reliability: the frequency, duration, and predictability or outa1es differs from point to point in the network. Today's utility structure provides redundancy so that the fairly-frequent outa1es or individual generatina units rarely cause a customer to lose power. Variability and controllability: electricity usen want real-time control over their use of electricity. They want to be able to add or drop load at the flick or a switch. Electricity aeneraton prefer to maintain constant production, and that load increase or decreue production in response to any operatin1 conditions the aeneraton race. All of these attributes or electricity are affected by the network. They are all different at point or supply than at point of delivery. For some attributes, the electricity u delivered is better than the electricity u supplied; for other it is wone. For example, service reliability as perceived by a customer is usually greater than the availability or a sinale generator. And a buyer of electricity can usually vary bis tate much Cuter than a generator can vary its output. But voltqe is more readily controlled at a 1enerator bus than deep in a distribution network. Today's utility industry hu mechanisms to reduce the negative err ects or the network, and to exploit the positive ones. In deregulation, with new wheeling ,. 232 -3-4-
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Power Tecbaoloala, lac. structures, it will be important to develop new mechanisms for pricina, costing, providina, and controllina these effects. 3.1.3 Poalbl Proble .. aad Soladou The balance of this chapter discusses a number of possible problems which increased transmission access and wheelina may brina. Many of these problems have to do with controllina the effects of the network on the attributes listed above. Effects of new aeneration sources alone, which do not necessarily have to do with wheelina, were discussed in Chapter 2. There is a areat deal of overlap, however between technical problems related to the new aeneration sources and those related to transmission access and wheelina. Issues of concern in this chapter are in three beavily-overlappina cateaories. One. set of effects is mainly due to contracts and reaulations. A second, ref erred to as operatina and plannina problems, requires application of existina methods or knowledae. This application may involve variations on standard approaches, but nothin1 fundamentally new is needed. The third area requires new conceptual thinkina u well u development of new tools and methods. 3.2 ~IBLI EFFICl'S Of CONTRACTUAL ARRANGEMENTS 3.2.1 Moaey Whnlla Wheelina uually involves chanaes in eneray flows over a transmission system. But it's possible to wheel money, instead of wheelina power. For example, 1n Figure 3.1 (a) a utility buys power from an independent aenerator u well u producing it at its own plants. It sells to many customen. In Fiaure 3.1 (b) the utility wheels the power from the aenerator to one of the customen. But this wheeling transaction does not chanae any power flows: the aenerator continues to generate the same amount and the customer continues to draw the same amount of power. This wheelina contract itself hu absolutely no physical effect money is being wheeled; eneray is not. ,. -3-5-233
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Power Tecllaoloal, lac. Electric Utlllr, r---------7 I -I I <> WhNllng ~D0rS6itOfar10~ .... D0 uav w '' ..,., .. an; ~(N:luellnOIOall~ Flpn 3.1 W11Hll II Pllyslcally tbt Sule u a sa ........ Parclaue/Salt, So Soaed a wH Trauacdoa O.ly WIIHII MoHJ, Not 1 ..... ,. Source: H.M. Merrill and F.C. Schweppe, wheelina, A Primer for Enaineers," Inmmiyion el Qilqibution. October 1917. 3.2.2 too, flon In Fi1un J.2, some of the transacted interchanae between Systems A and B flows throu1h System C. This utilization of the transmission of other systems for intercban11 schedules is often called loop now, panllel now, or circulatina power now. It is a phenomena of interconnected operation and is an inherent characteristic of ac power systems. 234 -3-6-
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Power TecllHloal, lac. NET l~HECICHAl~GE A 50 B ~ ::': ..,_ __ ,_o __ _. 20:~ \ 1500 '1W C ,soo ~ N t.OAD WW NET INTERCHANGE 0 flpN 3.2 nne lattrcoaaectltl Syste1U Loop flows amoq interconnected utility systems are usually not considered wbeeliq. Tbele flowa have traditionally been ianored unless they cause difficulties iD tbe systems not party to the tnDIICtioa. They are accepted u one of the unavoidable, uDdirable eff ectl or iaterconnectio1a. However, u transactions and loop flows are iDc:naiDa, some actions are beina taken. Some yean qo, the mast bothersome United States loop flows were around the "Wtern Dou1hnut, the trammiuion network linkin1 the Pacific northwest and southwat. Nevada wu the douahnut hole; there wu strona north-south trurtrion throuah California and weaker transmission throuah Idaho, Utah, and Arizona. When Jara blocks or power were wheeled from the northwest to southern California, loop flows caused excessive network loadina east or Nevada. The network hu been stren1thened, but loop flows still constitute a sianificant problem iD the wt. -3-7-
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Power Tecaoloales, lac. With increases wheelina in recent yean, the loop flow problem has become more widespread. For eumple, the Pennsylvania-New Jersey-Maryland interconnected companies (PJM) recently complained that perhaps 40% or a New York utility's purcbues from Ontario Hydro were flowin1 westward throup Michigan and the northeast throuah PJM. (See Figure 3.3.). Also, some western New York power flows throuah Penmylvania. It was agreed that the New York Power Pool would (l) pay r or the use or PJM9s transmission and (2) install a phase angle regulator to control flows throup PIM. New York bas the riaht to use up to 400 MW of Pennsylvania -rransmmion through about 1993, and declinin1 amounts thereafter. CONTRACTUAL PATH ACTUAL PATH Fl1re 3.3 -Loop Flows Whe 1000 MW of Oatarlo Hydro Power 11 WhHled to lastera New York Source: R.M. Maliszewski, American Electric Power Service Corp. -3-1-
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Power Tecbaolo&ia, lac. 3.2.3 Coatract Types Fiaure 3.4 summarizes some of the contract elements which reflect time and opentina conditions. Each class of contract implies a different level of reliability and use of the network, so each aenerally has a diCCerent price. FillM CONTRACT: Wheeler 1uarantees to provide wheelina services. Contract specif"aes conditions such as: Rate Renegotiation Interval (how often rates are renqotiated, based on system conditions), for example: Annual 24 hour I hour Period Deimition (when rate renqotiation interval is not specified) Flat Rate (no time diCCerentiation) Time of Use Rate (houn within day. day of week, season of year) Penalties for curtailment by the wheeler. INTEUUPT ABLE CONTRACT: Wheeler provides wheelina service subject to availability of network capacity. Contract specifications include rate reneaotiation interval or period definitions. RESERVATION CONTRACT: Wheeler aarees to provide wheelina service if buyer and seller want to use it. Flaure 3.4 Coatract llemeats which Renect Time aad Operada Coadltlo Figure 3.5 summarizes some of the different ways network flows can enter into the specification of wheelina rate structures. In aeneral, it can be shown that the -3-9-
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Power Tecbaoloala, lac. mepwatt-mile approacl) is a special case of the marainal cost approach. The contract path approach is a special case of the mepwatt-mile approach. The rate level is of prime importance in establishina the desired wheelin1 rates. The rate level determines how the Iona term costs and benefits of wheelin1 are shared between the wheeler, the seller, and the buyer. Fi1ure 3.5 lists various types of wheelin1 rates and their parameten. POST AGE ST AMP: Rate does not depend on network flows or distances e CONTRACT PA TH (RED LINE): Rate depends on specified nominal path throuah network (sometimes drawn with a red pencH!) MEGAWATr-MILE: Rate depends on line-by-line results of load flow analyses. Three different approaches. Net Effects (consider both increases and decreases in line flows) Positive Difference (consider only increases line flows) Vector Difference (assume an empty system with no other flows) MARGINAL COST: Rate based on marainal costs of wheeler as determined by load flows. Includes two types of costs: Losses Quality of Supply (costs of system reliability) Line Overloads Cost of New Lines Flaure 3.5 Dtff enat Ways or Renectla1 Network Flows la WhHllaa Rates The most prevalent structure is the posta1e stamp rate, followed by the contract r -3-10-
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Power Techaoloaln, lac. path (redline). Both _have been accepted by FERC. Most wheelina in the U.S. is short-term. Wheelina throuah several utilities alona a contract path may be done usina a postqe stamp for each utility. The mepwatt-mile method is presently beina used in Texas and is receiving increased interest (e.1., in California) because of pressure for mandatory open access to the transmission system. There are no known situations where the most general marainal cost procedures are actually implemented. Practical details (including FERC acceptance) still need to be worked out, but studies of their implications are under way in the U.S. 3.2.4 Effects oa Operadoa1 Different wheeling contracts can effect system operations in different ways. For example, Figure 3.6 is a simplified representation of a situation where two potential sellers comf,ete for a sale. In the area in question, wheelina contracts are by contract path. Utilities A and B both want to sell to the buyer. Both would have bad to wheel throuah essentially the same intermediate utilities. Because of pre-existina commitments, seller B wu able to assemble a contract path, while A was not. Assuming coal is cheaper than ps, the overall economics \tOuld probably have been better had A been able to do so --which would have happened with different procedures for acquiring wheelina riahts. SELLER A (Coal) ,, BUYER WHEELERS SELLER B (gas) F11ure 3.6 Two Sellen Competed to Wheel Power to a Buyer See "Terms and Conditions of Existina Transmission Service Agreements and Tariffs, Edison Electric Institute, Washington, D.C., December 1984. r -3-11-
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Power Techaoloaln, lac. As another example, one contract provides two ways of calculatina wheelina rates. The transaction can be treated u a simultaneous buy-sell by the wheeler, which collects approximately 50% or the spread between the buyer and seller incremental costs, with the buyer and seller essentially splittina the rest. Or it can be treated as a wheel, with the wheeler charaina only I 5% of the spread between purchaser and seller. The contract allows the buy-sell option only when the wheeler hu aenerating capacity that could be backed off to accommodate the purchue. When it does not, the transaction must be treated u a wheel. The wheeler hu obvious incentive to avoid operatina conditions where the 15% rate applies. One active wheeler provides transmission capability at a fixed rate for a contracted amount or capacity. The charaes do not vary if the buyer and seller reduce the amount wheeled for a period or time. This means that bu yen and sellen have an incentive to wheel at close to their contracted amounts. Their aeneration patterns would probably be different could they pay only for the MWh actually wheeled. But this flexibility would affect the wheeler's ability to sell network access to other parties. 3.2.5 Coatractual Effects oa System l,oladoa In some areas utilities can reserve wheelin1 capacity at relatively low rates, payina additional charges if they actually wheel power. This facilitates transactions where a utility with excess generating capacity sells reserves to a deficit utility. Beina able to make reserve transactions allows utilities to take turns addina capacity in relatively large blocks, takina advantaae of presumed economies of scale. In Texas this is harder, and utilities are more likely to meet their reserve obliptions with smaller increments of their own capacity. This is because Texas uses a meaawatt-mile method for wheeling rates with no provision for reservation contracts. This means that utilities which want to traffic in reserves must pay for wheelina service even if they never use it. r -3-12-
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Power Tecbaolo1l11, lac. Each of these patterns_ of system expansion has its own advantages: one is cheaper. the other more flexible. The salient point here is that the wheeling contracts influence which or them a utility chooses. 3.3 ~IBLE OPERATIONAL AND PLANNING PROBLEMS Problems in applying today's operations and planning methods under increased competition and deregulation are discussed in this Section. The emphasis here is on problems which must be solved with extensions or modifications of existing methods. These problems include: o maintaining adequate real-time control, o solving a variety of scheduling problems, o maximizing the use of the network, o planning network additions, o solvina certain system-wide problems, and o developing and applying emeraency procedures. In Section 3.4, other technical problems, which seem to require some new and different approaches, are discussed. Both sections talk about problems that have not yet been solved. We suspect that they are solvable. 3.3.1 Real-Time Control Nad for flow Coatrol Transmission line flows must be maintained within the line ratinas and, in general, flows must be kept within secure operating limits. If tfte network is heavily used, this means that inadvertent interchange must be kept at low levels. ,. 241 -3-13-
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Power Techaoloale1, Ille. Generation shifting is the most common way to allow for system security in the aeneral sense in ac systems control. Another way is circuit switching but this is usually not done because it tends to reduce security. A third way to control flows is to control load. Again, this is not practiced widely. Ned tor Gc11utlo1 co,trol Since controlling transmission flows usually means controlling generation. methods for accomplishina this are discussed under various scenarios. relevant portions from the scenario descriptions are repeated. For convenience, Under Scenarios 1. 2. and 3, the buyen and sellen become somewhat independent of the utility they happen to be connected to. Existing AGC systems allow interconnected utilities to operate independently, yet in coordination. Each utility operates as a control area. and is responsible for matching generation to load within its area. Coordination of interconnected operations is through several media. One is the telephone: operaton of neighboring systems talk very frequently, perhaps hourly or even more often. A second is automatic generation control (or as it used to be called tie line bias control.) This requires metering flows on each tie line and sendina data in real time to the computen of the two control areas the line connects. If loads and aeneraton become independent under retail wheeling contracts, they can in concept become separate control areas. This will require some additional metering and telemetry for the AGC. It will also require some additional telephone communication. Neither presents a theoretical problem. But if the number of meterina points or telephone calls becomes large, utility control centen will need upgrading. and more dispatchen may be needed. And there is not 100% reliable way to accomplish this electronic removal of loads. In Scenarios 4 and S (and to a more limited extent in Scenarios 1-3), especially as the amount of power bouaht. sold, and wheeled increases to significant levels, present AGC concepts become strained. ,.. -3-14-2.:2
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Power Tecbaoloaln, lac. In particular, an individual IPP or QF miaht wheel power to an individual customer. Each could constitute a control area. But they are much less able to hold to a constant interchange schedule than are normal utility control areu. Possibly telemetry could keep the seller informed about the buyer's instantaneous load. But 1enentin1 to match that load could be impractical fo~ the seller. If the seller tripped for some reason, telemetry in the other direction could inform the buyer, who could trip his load as well. This would cleuly be an unattnctive way to opente. To avoid this, present AGC concepts could be extended to allow non-contiauous control areu, different applications of the concept of inadvertent interchanae, and tnffickin1 in variability and controllability. For example, suppose a aenentor and a load, both within a utility's service territory, enter into a transaction involvina wheelina throuah the utility. The utility's AGC could treat them like a sinale external utility. The line to the aenentor and the line to the load would be tie lines. Of course, it would be difficult to control the aenentor to exactly match the load, so there would be considenbly more inadvertent interchanae than a utility normally deals with. Perhaps payments or penalties would need to be provided for 1eneraton that track the load well or poorly. Los of Cogtrol Lack of control over line flows may cause overloaded lines or stations. It will increase inadvertent interchanae. If it gets too bad, it will require mandatory corrective action or ntes for payment in dollars by offending parties. This requires methods for determinina who the offenden may be. The control center in Lauf enbura, Switzerland, performs some policing of interconnected utility opentions over much of western Europe. There is no national control center with this function in the United States. Instead, problems are identified by individual utilities, or sometimes through NERC activities. This -3-15243
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Power Tecbaolo1l11, lac. policina role would have to be assumed by some entity or entities under the more extreme scenarios. Proper voltaae control is essential to system operation but represents a cost to whomever provides it when separate voltaae control devices are used. Lack of control causes poor voltaae profiles. In the extreme, this could result in poor customer voltaaes if local voltaae control devices are out of control range. In very extreme situations this could cause a system voltaae collapse if V ARs start flowing to support MW flows, which in turn cause further voltaae declines. Again, some entity or entities would need to coordinate:, voltage control. And the embedded cost of existina devices, u well u the cost of new ones, would have to be allocated amona those who benefit. 3.3.2 Schedullaa Problem, Schedulina is concerned with a time frame areater than an hour and less than a year or so. It includes forecutina, shuttina down and startina up aenerating units (the unit commitment problem), schedulina fuel and hydro resources, maintenance schedulin&, and schedulina wheelina, purchases, and sales. Scheduling also includes assessing network capacity; this is discussed in Section 3.4. Wheelina transactions that are under utility control are options which utilities can consider u they plan operations. Existing methods for unit commitment, maintenance schedulina, etc., may need to be modified if wheelina increues. This is because these methods are not now able to include wheeling u alternatives. If wheelina transactions are uncertain, and the uncertainties are significant, fundamental new approaches to solvina operations plannina problems will need to be developed. One issue which will have to be resolved is providing even-handed treatment to utility-owned resources and independents as they compete with each other. This would be a particular problem in Scenarios 3 and 4. r -3-16-
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Power Tecbaoloaln, lac. Some of the challenaes described above depend on the extent of wheeling and transmisson access. Things work (although there ue strains) at today's levels. If wheeling and transmission access increase, the strains will become more troublesome. For instance, there are many wheelin1 transactions, especially wheelina transactions whose levels chanae frequently, the wheelin1 utility may have to train and add more personnel just to handle the interchange reschedulina. This hu already happened to at least one utility in the United States: Houston Liahtina and Power hu added an eneray scheduler to the dispatch staff. That utility estimates that over one-half bis time is dedicated to handlin1 the effects of coaeneration on system operations. The utility anticipates staffina about five additional people in the future to accomplish this function for all shifts. 3.3.3 Maxlmlzla1 Network Use Gt11ratlo1 Shl(tln The fint and euiest mechanism to allow increased transmission system use for additional wheelina flows is to shift aeneration, when required9 to alleviate transmission overloads. This is done occasionally in the United States. European practice is to reduce the wheelin1 instead. Constrained economic dispatch programs or optimal power flow proarams are used in the New York Power Pool and elsewhere to shift generation in real time for security dispatch purposes. Redispatchin1 to recoanize constraints causes the wheelina utility's operating costs to 10 up. These increases are fairly well-defined and are not hard to compute. It is reasonable to expect the buyer and seller to cover these costs. It may also be appropriate to reduce third-party aeneration or other wheeling transactions in order to alleviate network overloading. This option is likely to be more important under Scenarios )9 4, and 5 than under Scenarios 1 and 2. There are three conceptual problems in doina this. Fint, assessina the costs to the parties curtailed is not easy: they may include ill-defined opportunity costs. Second, this lack of definition makes it hard to define an optimal curtailment policy or method. r -3-17() .1 ... ,..._ ..
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Power Tecbaoloale1, lac. Third, u discussed in_ Chapter 2, this really is not an optimization problem but rather a problem with multiple and conflicting objectives. Bclaxlp1 Security Cop1tralpts Today, United States utilities have plannina and operatina procedures to avoid cucadina outages under specified continaencies. Applyina these procedures provides reliable electric service. There is no indication that current rei iability levels are unnecessarily hiah, but relwna constraints, or fine-tuning them, could provide additional transfer capability. Some of these actions would reduce reliability; othen would not. For example, the thermal ratina or limit of a transmission line is bued on stringent ambient conditions: hot day, little wind, etc. Often weather is more favorable, and the line has hiaher capability. A real-time thermal-ratina method could increas~ transfer capability durina much of a year, with no loss of reliability. There is obviously a limit to the amount of additional capability that can be provided before reliability suff en. Relaxina or fine-tunina constraints may conflict with solvina a problem discussed in Section 3.4: with increued wheelina, it is important to be able to objectively and simply define and measure transmission capacity. Sulfa Bcl1(orccmc1J A third important way to increase transmission capability is to add lines and other equipment to strenathen weak spots. Sometimes this can be done quite inexpensively. For instance, a study of a major pool found that transfer capability could be increued substantially by addina capaciton at certain substations. Capital and operatina costs for doina this were low, and there wu essentially no environmental impact. Under other circumstances it is necessary to do more expensive thinas (which may be hard to do in a timely fuhion), such u; o add lines, -3-18-
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Power Tecbaoloala, lac. o uparada existina lines, o increase voltaae levels, o convert single circuit lines to double circuits, and o provide de or high-phase-order ac lines, etc. 3.3.4 Traualuloa Plaaalaa Proble .. One major effect on plannina is due to the great uncertainty in arowth of non utility aeneration. For example, Fiaure 3. 7 shows the published forecasts of QF and IPP capacity issued by the WSCC reaion of NERC. The data show the forecasts for the total aeneration expected to be in service in 1992 by year that the forecast was published and the year to year variation in the forecast. The uncertainty presents a difficult f orecastina situation for plannina staffs of the utilities reminiscent of the problem of forecutina loads u part of aeneration plannina. It takes several years to construct new transmission facilities. If the QFs and IPPs actually do appear on the system, new transmission facilities may be required for wheeling. If the utility system construction is bued on the early forecasts and the IPPs and QFs do not appear, the utility may have excess transmission capacity. On the other hand, if the plannina enaineers wait to see what QF and IPP generation is actually constructed, there may not be sufficient transmission capacity available for wheelina. The cost of this uncertainty may be sianificant but would probably not be unbearable for an intearated utility (Scenarios I, 2, 3) because transmission facilities are less expensive than aeneration plant and hence represent a small fraction of total plant. But in Scenarios 4 and 5 the transmission is owned by an independent entity and constitutes most of the entity's assets. Uncertainties, u a fraction of their total assets, may represent unacceptable risks. The TRANSCO is assumed to have an obliaation to provide an adequate and reliable transmission capacity necessary to supply the wheelina needs of anticipated customers. Reaulatory authorities may require consideration and coordination of reaional transmission capacity needs. Reaulaton may penalize TRANSCO as reliability is poor. r -3-19~, '7 4,
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Power Techaoloal, lac. 8 -7 .. 1 8 5 .c 4 t:. 3 -2 Cl I 1 Cl en 0 G 2 -1 -2 1983 WSCC cogeneratlon + OtherCapability five Conaecutlve l'orecaata for 1992 1984 1985 Year of Forecast 1988 1987 l'orecalt Capablllty + Change In l'orecast F11an 3.7 Foncutl of Noa-Udllty Geaendoa la WSCC. Upper cn II total capacity foncut. Lower Is year-to-yeu ,arladoa oa the foncut. The TRANSCO would have less capital than an intearated utility servin1 the same area, and the uncertainty in transmission requirements could be burdensome. The uncertainty could be reduced in all scenarios by providin1 a role in the plannina process for the QFs and IPPs. Some institutional barrien would have to be overcome, u these entities will be in competition with the utilities and data exchanae may not be u open u at present. 3.3.5 Sol,1 S11tea-la1laNrln1 Problem, Certain technical (e.1., stability, voltaae-V AR control, etc.) problems involve broad system analyses. The resolutions of these problems are usually handled routinely by utilities today. Some problems ue not handled routinely today. For example, major transfers from one area to another may cause operatin1 problems which could be rectified by network modifications in neiahborina systems. If the neiahborina utilities do not r -3-20-
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Power Tecbaoloal11, lac. choose to make th~ cbanaes, the trans en cannot take place. There is no convenient mechanism r or one system to undertake internal improvements r or the benefit of another. Certainly the ratepayen in one uea do not wish to finance improvements for the benefit of another utility's customen. And a utility wanting to pay r or improvements to another utility's system would have to overcome serious reaulatory hurdles. If the industry becomes more f raamented, this type of situation will be more common. YAB-Y1l1Mt Cogtrpl The flow of V ARs bas two major effects on the transmission circuits and system. It uses up a portion or the physical capacity of the circuit, causing real power losses. It also effects the voltaae maanitudes in the circuit. This later effect is complex and depends upon the exact circuit conditions. In some situations, VAR flow will cause the voltaae to rise alona the circuit. Sometimes the flow uf V ARs will cause a voltaae drop at the receiving end. The rise or the drop may be beyond acceptable system operatina standards. V AR-voltaae control is important r or the overall system, but is achieved by devices or actions at specific locations. When a sinale utility owns and operates all aeneration and transmission facilities in an area, it takes action to solve this system problem. But in a fragmented system, none of the individual independent entities can solve its local problem: they have to work together to solve .he system-wide problem. This miaht be done by aiving the transmission utility a way to charge for VAR voltaae support. In real time, the transmission utility could have authority to schedule aenerator V ARs. But this is a difficult technical problem. Even today's fully integrated utilities seem to have problems with it. System Stability 114 Qygamlc Problem Stability problems, and various types of dynamic problems, involve both generation and transmission systems. These are studied on a broad system basis today. This r -3-21-
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Power TechaoloCies, lac. needs to continue, an4 requires a mechanism for data exchange and joint studies. Fixes are also coordinated efforts, and include fast run-back of generation, series capacitor installations, added switching stations, intermediate controlled supplies, generator stabilizer, etc. ()peratina fixes may involve controls or limits on power transfen. Since both hardware and control fixes require cooperative efforts in study and implementation, a systeD'.-wide mechanism is needed. TRANSCOs should probably have the responsibility here under Scenarios 4 and S with authority established by contracts. Integrated utilities could continue to do this under Scenarios l, 2, and 3. 3.3.6 lmeraeacles ETJ1er1encies involve three time periods. Before an emeraency occun, preventive and limitina measures art.: taken. During the emeraency, real-time responses take place. Afterward, the system is restored to normal operation. In Scenario l, utilities are responsible for actions in all three time periods. In the other scenarios, other panies are involved to varying degrees. But under all scenarios, it is important that actions be coordinated. This might appropriately be done by the utility in Scenarios 1, 2, and 3, and by the TRANSCO in Scenarios 4 ands. For example, relays and other kinds of protective equipment need to be coordinated. The approximate amount of load which needs to be shed if frequency decays by 0.05 Hz, for example, is known to the utilities. The under-frequency relays set O.OS Hz value need to control, in the aggregate, the right amount of load. The sy:,tem operation function includes the authority for and capability of tripping aeneration and load, if needed, to prevent line overloading or system collapse. This function must coLtinue even under deregulation. -3-22-
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Power Tecbaolo1le1, lac. Restoration is the pro~lem of restarting a blacked-out island. QFs and IPPs can be of benefit; they can also constitute a problem. Whether they make things better or worse is ;ndti.,lndent of whether they are wheeling, selling direct to the utility, or simply supplying their own load, connected in parallel to the utility. One step in restoration is to provide electric power (to run pumps and other equipment) in blacked-out power plants. If QFs and IPPs can start in a blacked out system~ they can in tli~ory provide this power. They also provide incremental load-carrying capability within an island. However, studies have shown that the most frequent problems in restoring service have to do with load and generation coordination. (See Table 3.1.) These problems will be increased by having to deal with non-utility operaton, so utilities may discount QFs and IPPs as resources. The QFs and IPPs may even introduce additional switching and coordination complications, for instance if they need to be switched out in early stages of restoration and then switched in and synchroniu.d later. The significance of IPPs and QFs in system restoration has to do purely with the number and types of generation facilities in an island, and so is independent of any particular deregulation scenario. But authority and the means to use this authority will need to be provided, probably to the TRANSCO in Scenarios 4 and 5. TABLE 3.1 Restoradoa Proble i,y frequency of Occuneace I DESCRimON NUMBER Switching operation 8 Procedure out of date 7 Supervisory control/data acquisition inadequate 7 Dispatch of rice coordination 7 System status determination 6 Sustained overvoltage 5 Synchronization location and facilities 5 (Based on 48 major disturbance reports, cited in "Power System Restoration: IEEE Trans, Power Systems, PWRS-2, No. 4, Nov. 1987.) -3-23-
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Power Tecbnolo1les, Inc. 3.4 ANALYTICAL PROBLEMS Section 3.3 discussed transmission access and wheeling problems that involve presently-performed functions and that can be solved with relatively straight-forward extensions of today's methods. In this section four problems are discussed that seem to loom over increased transmission access and wheeling and for which new solutions need to be found: 0 0 0 0 3.4.1 definition of available transmission capacity, reliability and security issues, transmission scheduling, and costing, valuing, and pricing wheeling. Definition of A,allable Tran1mluloa C11paclty How Jrag1ml11log Capacity MC1auu4 Today There is no simple equivalent of the telephone company's busy signal on a power network. Transfer capacity is not the rating of a single line or a few lines. It is a function of the strength of the network u a whole. It is defined in terms of reliability criteria, which themselves are objective and somewhat imprecise. It varies u switching operations occur and u demand, generation, and wheeling patterns change. Even loop flows and actions taken by operators of other system affect the available transfer capability. Figure 3.8 attempts to define how much power system X can transmit to system Y. with a simultaneous transfer from X to Z. For instance, the Y to X transfer capability is 6200 MW when X to Z transfer is 5200 MW. On the other hand, if the transfen are in the opposite direction, with Z transmitting 2600 MW to X. X can only transmit 1300 MW to Y. -3-24-
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7000 Y to Power Techaoloaln, lac. Three such diaarams are required to represent transfer capabilities for a three area (X, Y, and Z) system. Each diaaram is valid for one specific operatina condition and a particular set of reliability criteria. These diagrams are developed using load flow proarams, which simulate the flows on the network. Developing sets of these diaarams for even a three-area system, for a spectrum of operating conditions, takes a lot of enaineering time and inter-utility cooperation. Transfer capabilities for systems with more complications (due to a variety of possible wheeling transactions, for instance), are much harder to model. 6 X -,_ --N 5QQQ 3000 2000 l000 X IMPORTS 0 :,c 4000 3000 lOOO 1000 1000 )C 0 3000 N X EXPORTS 2000 3.000 4000 Fl1ure 3.8 -Typical Bl-Axis Transfer Capability Poly1on Source:EPRI EL-3425 ,... -3-25-,/ I
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Power Techaolo1le1, lac. Effecu of Igcuue4 Whc,ll11 Today's methods for measuring transmission capacity work, but only because o the parties all have larae enaineerina staffs, o they are willina to exchanae data and cooperate in studies, and o they are not in serious competition, so utility-to-utility differences in definina transfer capabilities are not seen as competitive ploys. Under the dereaulated scenarios, particularly Scenarios 4 and S, only the first of these conditions is likely to hold for the GENCOs. The TRANSCOs may have an adequate staff, but the cooperative nature of today's environment will be lost. Since under some of the scenarios the entity ownina the transmission may compete with IPPs and Qfs who want to wheel, the definition of transfer capacity may be a bone of contention. Accordinaly, today's methods for measurina transmission capability will probably not work under dereaulation and sians of this are already occurrina. What 11 Needed Under dereaulation and increased wheelina, a new method for definina transfer capacity is needed, with the following characteristics: o it should require straight-forward calculations, o it should represent an objective, defensible, standard, O" it should not be so conservative as to unduly limit wheeling, o it should represent variations in operatina conditions and network changes due to maintenance, switching, etc., and o it should lend itself to on-line use in control centers as well as consistent application in planning. It is particularly important that this method be so clearly acceptable to all parties that the courts and commissions will not have to spend inordinate amounts of time r -3-26-
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Power Tecbaoloalu, lac. reviewing and redefining transmission transfer capability. Such a method is not available today. Some creative thinking will be needed to create it. 3.4.2 Rellablllty aad Security luuu Reliability and security issues are closely related to transfer capacity. Today recommended criteria are developed by NERC, by each reliability area, and in some cases by power pools. The criteria are interpreted and applied by each individual utility. These criteria are different for different parts of the system. For example, reliability of satisfying expected loads by a utility's set of power plants is expressed as loss of load probability, expected unmet demand, reserve marain, etc. The reliability of the transmission network is defined in terms of the number and type of contingencies it is designed to withstand. There is no accepteq_ method for expressing generation reliability and transmission reliability in equivalent terms. Today's level of reliability is one of the bundled attributes of electricity. It is provided to the customer as part of a package by integrated utilities. Under deregulation, with this package unbundled, ways of measuring, equivalencing, costing, and pricing reliability and security will be needed. 3.4.3 The Traa1mluloa Sched11lla1 Problem With few exceptions, scheduling use of transmission capacity is not a problem today. If a utility has an internal bottleneck, and many do, it simply redispatches generation so as not to overload it. The costs are shared by all of the customers and are not perceived by them. The few exceptions --harbingers of what may occur under deregulation and increased competition involve multi-company transactions. Two examples involving loop flows were mentioned earlier in this chapter. When loop flows hit transmission constraints, attempts were made to negotiate ad hoc solutions. For the PJM problem discussed earlier, the solution included cash payments, and a r -3-27-
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Power Techaoloaln, lac. modification to the _D.'ltwork. continues. Around the western doughnut. the negotiation Several methods have been proposed for scheduling around transmission bottlenecks. Schweppe et al have proposed methods based on marginal cost pricing theory (e.g., see F. C. Schweppe, R.E. Bohn, and M.C. Caramanis, "Wheeling Rates: An Economic-Engineering Foundation," MIT Laboratory for Electromagnetic and Electronic Systems, report TR 85-005, September 1985). The New York State Energy Research and Development Authority sponsored work which led to a similar but somewhat different solution involving bidding (H.M. Merrill, "Economically Efficient Allocation of New York's Transmission and Distribution System," Power Technologies, Inc., June 1985). Figure 3.9 is an initial view of two dimensions of the transmission schedulin~ problem. Faced with two possible transactions, both of which cannot be accommodated, which should the: TRANSCO accept? With costs known, this is a classical integer programming problem known as the knapsack problem. MW 600 400 200 I 3 It Transaction A I I 4 5 6 X to Y Transfer Capacity Transaction B I I I 7 8 9 10 11 Day Flaure 3.9 Two Dlmensloas of Traa1ml11loa Schedulla1: 1,me and Capacity r -3-28-
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Power Techaolo1le1, lac. This simplified problem is not very useful, however. In reality there may be many more dimensions, because wheeling can cross the network in a variety of paths. With wheeling to or from three entities, Figure 3.8 becomes a three-dimensional venion of Figure 3.9, with time the third dimension. The scheduling problem is further complicated by uncertainty. In Figure 3.9, the TRANSCO might prefer transaction B. But if A applies today, and B is anticipated but not guaranteed to apply tomorrow, should the TRANSCO tum down A and wait for B? 3.4.4 Costla1, Valula1, and Prlcla1 Economic issues underlie the reliability and schedulina problems described above. These issues are somewhat beyond the scope of this report, which is on engineering topics. But the economics and enaineering are so entwined that this discussion would be incomplete without raising these economic issues. The utility industry and its reaulaton have developed a workable regulated monopoly where o prices are somewhat but not precisely cost-based, o the industry is close to but not economically efficient, and o utility ownen generally recover costs and earn an approximately fair return. As was mentioned earlier, bundling a variety of services and charging for them as a package has made present pricing and regulation much easier than it would otherwise have been. These services will be unbundled under deregulation and increased competition. But even under. Scenario S, the most extreme scenario, the industry will include reaulated monopolies (TRANSCOs and DISCOs). This mixed market/monopoly system will present unusual pricing and costing challenges. One proposed approach is to charge for wheeling services on the basis of marginal costs (Schweppe et al, op. r -J-29-
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Power Technoloales, Inc. cit.). This is attractive from the economic viewpoint. Methods are being developed to test and implement these ideas. But there are issues which present theory has not yet fully resolved, such as reconcilina marginal cost pricing and revenue recovery. These methods are based on classical economic dispatch theory and would need to be rethouaht for applications in Scenarios 4 and S. A Ions-term marginal cost theory may be needed in those scenarios: classical economic dispatch theory uses short-term marginal costs. For example, Figure 3.10 compares short-term marginal wheeling costs and changes in wheelina utility operating costs for identical transactions wheeled through two utilities, A and B. Both A and B have transmission capital costs to recover. ~otal Operating Costs C.5 { ce:,IIIIM'I\ Shon-erm Morg~"IOI Wl'\Nling Ccst Flaure 3.10 Short-term maralaal wheellaa costs and cbaaaes la total operatlna costs, per kWh wheeled, for two hypothetical wheellaa utilities Source: Schwepp'! and Merrill, Op.Cit. ,.. -3-30-
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Power Tecbnoloales, Inc. Table 3.2 shows that_ both transactions more than recover changes in operating costs caused by the wheeling. But, utility A under-recoven fixed costs, while utility 8 over-recovers. TABLE 3.2 Traa1actlon1 Ia,01Yla1 Two Different WhHllaa Utilities Wheeling Wheeling through through Utility A Utility B Wheelin1 rate (marginal wheeling 1.0 cents/kWh 1.5 cents/kWh cost) Less: Total change in wheelin1 utility's 0.5 cents/kWh 0.8 cents/kWh operating costs Change in net operating income +0.5 cents/kWh +0.7 cents/kWh to wheeling utility Less: Fixed capital costs 1.5 cents/kWh 0.5 cents/kWh Change in total revenues to -1.0 cents/kWh +0.2 cents/kWh wheeling utility (under-recovery) (over-recovery) I I I I I I I This can be fixed by adding "revenue reconciliation" to marginal costs. Unfortunately, this gives wheeling rates that do not always encourage an increase in production efficiency. For instance, suppose the marginal wheeling cost is I cent/kWh. Revenue reconciliation can be eith(e~ positive or negative, depending on whether the utility would otherwise under-recover or over-recover. Considering utility A, which under-recovered, let the Wheeling Rate 2 cents/kWh (Revenue reconciliation of + l cent/kWh). -3-31-
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Power Tech11olo1l11, lac. Ncw suppose the buyer and seller are also utilities, with marainal operating costs of 6 cents/kWh and 4 cents/kWh, respectively. If the wheelina rate is the muainal wheelina cost of 1 cent/kWh, the buyer and seller can afford a deal which would increase overall production efficiency and cover the wheeling utility (A's) operating costs, but not its fixed costs. If the wheeling rate is 2 cents/kWh, the buyer and seller have no incentive to wheel even thouah doing so would improve overall production efficiency and recover A's fixed costs. -3-32,, .~ ln ~_..,,<
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Power Tecbnoloales, Inc. CHAfilB IY
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Power Techaoloales, lac. CHAPTER 4 SUMMARY OF TECHNICAL muES AND POSSIBLE SOLUTIONS 4.1 SUMMARY OF TECHNICAL PROBLEMS POSED BY SCENARIOS The major specific technical problem areas which are affected by the increasing amounts of non-utility generation and requirements for wheeling are: 1. measuring transmission system capability, 2. ensuring adequate spinning reserves for the generation system, 3. maintaining adequate control of generation, frequency and interchange flows, 4. establishing methods for scheduling transmission use and controlling transmission flows, S. planning the bulk oower system, 6. system dispatching and operation, and 7. solving system-wide technical problems. Note that this list does not include those technical problems and solutions associated with transmission system limitations that are due to inherent physical limitations. These were discussed in the first report of this sequence and reviewed briefly in Chapter 3. They will continue to exist and be solved by the methods discussed. The scenarios do affect the intensity and complexity of these transmission system limitations by the level of non-utility generation capacity in the first three scenarios, the shifting of responsibilities in the last two scenarios, and the growth of transmission access and wheeling in all of the scenarios. The list of transmission system limitations and solutions is long. Existing technical problems and future ones are highly system specific. Engineering approaches exist to solve problems such as increased breaker short circuit duties, requirements for added capacity in lines, breakers and transmission networks, etc. The scenario conditions do not change the basic nature of these problems nor their ~olution. -4-1-
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Power Techaoloaln, lac. They do cbanae the economic Cramework and require the clear estabt.shment of responsibilities in the diCCennt institutional structures. 4.2 MIASUlllNG TRANSMmlON SYSTEM CAPABILITY Under the present, cooperative mode or plannina and operating interconnected electric utility systems, available transmission capacity within a system and transf t.r capability between systems is defined by complex system studies. These studies are based upon reliability criteria established by mutual aareement amongst power system enaineen and performed by en1ineerin1 study committees. This is a satbfactory arranaement since the enainnn undentand and trust each othen' judaments. The transfer limits defined in various reaions or the country are bued upol! different security-reliability criteria. Within the current industry framework this is acceptable; the e!laineen involved have cooperated in establishina the acceptable criteria and understand their implications. Criteria used are bued upon wont case evaluations usumina sinale contin1enci11 in some naions and on double continaency evaluations in other areu. Limits are atablilhed bued on normal and emeraency circuit ntinp and voltqe limits at various points in the system. As the number or non-utility 1eneratiD1 entities increases and both whnlina and trammiuion accea incnue in the various scenarios, then is a areater and areater need for simple definition or available transmission and transfer capability and the adoption of aenerally acceptable and undentood criteria ror use in establishing specific limitations. 1 he entrance of competina entities envisioned by the scenarios means that there will need to be a simple scheme ror definin1 the transmission capacity that may be Uled without the need Co,. complex, cooperative en1ineerin1 stlldiel. The electric power system needs a quantity ana101ous to the busy sianat in the telephone system. This technical problem ii intimately nlated to the reliability criteria adopted to euun system security in system operations. Present practices have arisen since the 1965 Northeut blackout. credible continac.ncies are analyzed and system -4-2,.. 2C3
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Power Tec:baolo1ln, Ille. opention limits are 14t based upon def euive opentina tactics. These procedures tablish transmission reserves required to cover potential emeraencies. Criteria r or transmission system security analyses miaht be baled upon probabilistic reliability indicm u they may be in aenention plannina. This would lead to a more uniform level of system security and opentina reliability. But the adoption or this type of approach would tend to result in a more complicated technique for Ntablishin1 available capacity limits in the transmission systems than those presently used. This would def eat the purpose of establishin1 a simple definition and euily rodentood method for measurina this quantity. This is an issue under all 5""tnarios. 4.3 SPINNING RESERVES AND UNIT COMMITMENT In the current industry structure the utilities have qreed upon openting auidelines which require each utility control area to maintain adequate spinning reserves. This is accomplished by usina unit commitment pnctices which minimize total system opentina costs for some time period. The need for spinnina reserves increases the aeneration production costs since more units must be operated than are required to meet peak loads. Many of the units runnina must be kept at lower output levels than those dictated by a pure economic dispatch. The benefits or this type of operation are increased system security. better frequency control and reaulation, and the ability to mnt temporary aeneration shortaaa within local control area nther than relyin1 on the interconnected systems to provide support. These arnngements facilitate the functionin1 of the AOC systems. As the non-utility aenention levels increase in the various scenarios, it becomes increuinaly important to ensure that spinnin1 reserve levels are maintained at reuonable levels. Total reserve maraim u well u the distribution of spinning r -4-3-
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Power Tecbaoloales, lac. reserves amongst indi~idual units must be defined and controlled. This raises technical questions concemina the value of supplyina spinnina reserve to the system and how the spinnina and ready (i.e., rapid start) reserves are to be measured. The securing of aeneration supplies under contract terms off en the opponunity to establish a defined cost for providing this service. Selected sources for all generators could be required to supply or purchase this service u a condition for entry into the market. Current unit commitment practices may be extended in the first three scenarios with the utility schedulina its own generaton. If scheduling control of non-utility generation is required in the fint three scenarios, it could be the subject of contract terms that might, for example, require utility payments for energy unsupplied because of unit commitment scheduled shutdown of non-utility generatio~ (i.e. payments based on defined opponunity costs). In Scenarios 4 and 5 a different approach is needed. IPPs and GENCOs with a group of units could be required as part of the contractual agreements to supply a given spinning reserve schedule. They could satisfy the requirements as they wished using their own commitment schedules. Metering and communications are required for monitoring to ensure compliance. Individual IPPs could be required to furnish or purchase spinnina reserve capacity from the larger aeneratina entities. The TRANSCO could act u a broker. 4.4 AGC SYSTIMS AND FREQUENCY CONTROL AGC systems used to control system frequency and interchange are based on the current structure of utilities where control areu are clearly defined. Metering of tie lines into each area is an integral part of these systems and is easily accomplished. Control actions of the interconnected utility areas are coordinated by mutual aareement so that each control area is responsible for supplying its own load demands. Each area must keep enough capacity online under AGC control so that it -4-4-
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Power Ttcbaoloaln, lac. is not dependent on s~pport Crom interconnected systems for lonaer than the period that emeraency circuit ratinp apply (i.e., 15 minutes). The level of inadvertent interchanae may be expected to increase under some of the scenarios unless proper contractual arranaements exist to require reaulation to be supplied by non-utility sources u well u utility aeneration. Retail wheelina could increase inadvertent flows even more under Scenarios 2 and 5 without proper contract terms and control actions. Sources enpaed in retail wheeling should be required to schedule 1eneration to mfft the requirements of the load cycle of the purchaser or to purchase load f ollowin1 aeneration from the local utility if they lack the ability to follow the customer's load cycle. If inadvertent interchanae levels increase to the point where they interfere with system opentions and control and cause uncontrollt loop flows, the current syste~ of repayment in kind should be replaced by one requirina direct payments in dollars. The rates should be hiah enouah to encouraae the 1eneratin1 entities to install better control practices and systems. Technical problt1ms ue posed by the various scenarios related to AGC system functions. With laraer levels of non-utility 1eneratin1 capacity connected to the transmission systems, remainina utility generaton will be required to assume more of the re1ulatin1 duty unless the supply contracts enable the control of this capacity by the utility AGC system. If these units are to be treated as being outside of the existing AGC control areas, the number of meterina points needed for the AGC system increases. With unrestricted access to the transmission system the very definition of a control area becomes fuzzy. Under scenarios that allow wholesale wheelina only, the larger sized non-utility aeneraton may be treated as scheduled interchange by t~e AGC systems. Retail wheelina is allowed under some of the scenarios where both utility and non utility aenenton serve specific retail customen located locally or outside of the local control area. With a few such arranaements, the AGC systems can treat these -.c-5-
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Power Tecbaoloala, lac. u scheduled interc~ae transactions. Contract terms that specified the responsibility for the mismatch between the aeneratina source and the retail customer would be required. Theoretically. it would be possible to treat each retail wheelina arranaement u a separate intercbanae transaction by requirina the aenerator to match the retail customer's load at all times. This complicates the control or the aeneration, requires additional meterina and communications, and may make scheduled interchanae vary at the same rate as the retail customer's load cbanaes. It may require that the parties to the retail wheelina arrangement purchase reaulating supplies Crom the wheeling utility. or the utility in which the retail customer is located. In the last scenarios, the whole buis or current tie-line control becomes undermined since it presumes well defined control ueu in which sufficient aeneration is under AGC system control. Under these scenario conditions, th~ current AGC system concepts could be extended if contracts between generation entities and the TRANSCOs responsible for system operation contained requirements for control of units by the AGC system. It is possible that control areas may be def"lned electrically, matchina sources and load areas. Also in the last two scenuios the number of independent 1eneratin1 entities increases and the AGC problem becomes more important to resolve. The current voluntary cooperative uranaements would have to be replaced by contractual arranaements which provide for required amount or generation control to ensure both frequency and interchange control. Metering and communication systems would need to be expanded to allow the monitorina or these arranaements to make certain that the vuious parties did not cheat. Under the condition.'l of the last two scenuios, it might be desirable to consider sepuating the current luge eastern and western interconnections into smaller synchronous interconnections to facilitate the monitorina and control or required generation performance. This would, or course, require the investment in appropriately sized de interconnections to permit interchanaes to take place between these new. smaller sized interconnected systems. The advantaaes would be larger. transient frequency excursions, permitting the easier detection or insufficient _,._,_ 2C7
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Power Teclaaolopa, lac. rqulatin1 capacity _and the direct control of interchanae between the iAtercollDICtiom over the de ties. It would also reduce the extent of the coordination required by confinin1 requirements to smaller interconnections. Tbe disldvuuqa of this proposal are mainly with reprd to t 1e limitations it mipt impose on economy intercbanae transactions. With oil prices hiah relative to coal fuels, there hu been a 1eneral increase in the economic interchange from the mid west to the eutern areas of the country. Openina the ac ties and replacing them with back-to-back de interconnections miaht severely limit this flow. The separation of tbe ac interconnections would require the openina of a larae number of exiltiq tie lines and would undoubtedly reduce the opentina reliability of systems on the boUDdaries of the new reduced sized interconnections. Finally, redaciq tbe size of the interconnections would severely limit the aeoaraphic extent of the markets for eneray. For these reasons, this possibility seems only of tbeontical interest. 4.5 SCHEDULING ~ION SYSTEM USE Curnnt eneray control systems schedule and control power aeneration to maintain frequency, control scheduled interchanae levels, and realize optimal e~unomic operation. ne trammission systems constrain this control. Transmission losses may affect the economic schedulilla. Transmission system limitations and system security considerations are all recoanized in the desian of modem energy control systems. but II constraints to the primary control objectives. Increased trammissio~ access and wheelin1 and the entry of Iaraer amounts of non utility 1eneration would chanae the buic nature of the scheduling problem. With tarae blocks of aeneration and retail load beina supplied under wheeling contracts, it becomes necessary to be able to schedule and control the required transmission flows over the limited transmission capability for both Iona and short time periods. The lonaer periods (e.a weeks up to yean) are needed to establish non-conflicting wheelin1 contracts and the need for new transmission -apability. The shorter transmission schedulina function would be desirable to maximize transmission system use, permittina optimal use of a limited resource within security constraints. ,... -4-7-') ()8 '-\., )
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Power Teellaolol,ln, lac. A simple example wo~d be the supply of a load area over a sin1le transmission path under conditions where 1eneration is obtained under a number of different contracts. acb with a cliCf erent capacity and duration. The transmission system should ideally be scheduled to minimim the total cost supplyin1 the load demand recopizin1 the limited transmission system :apability. The problem u stated is similar to the classical. one dimensional tnapsack problem in operations research. Under ideal conditions of well defined capacities and durations it is solvable by various methods. Unfortunately, in actual electric power systems these ideal conditions do not exist. Traumiaion system1 are complex and power nows obey physical laws and not contract terms. The trammiaion scbedulin1 problem is therefore multi-dimensional with power nows extendin1 over multiple transmission paths. Transmission capabilitia vary with time due to cliff erent load and 1eneration patterns an
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4.6 BULK POWER S~M PLANNING PROBLEMS nlaled to the scenario conditiom an caused by the increased UDCertaintiel that arise with reprd to the need for new bulk power system facilities ud tbe ~..a ucertainties that non-utility aeneration will. in fact. materialize U IIUIOunced. The current industry structure vests the responsibilities for forecutina and planning in tbe utilities with rqulatory ovenipt and de facto participation. Utility plamlina staffs foncut loads. evaluate the need for new facilities. and stan the implementation proc:ea carried out by their utility orpnin.t.ions. They an faced with levels of UDCertainty in load foncatina and in forecutina the future costs and service dates of planned additions. As non-utility aenenton (Qfs) have entered the market in the past. a new dimension bu been added to tbe uncertainty. Generatina capacity announced and planned by non-utility entities must be recopized in the utility plumina process. The level of unc:enainty mociated with these new 1eneratin1 sources has been demomtrated to be very hip. In both California and Teus the level of planned non-utility aenention roN rapidly u hip fuel price levels and PUllPA avoided cost levels appeared to be on the rise. When fuel market prices declined. reducing expected payment levels for non-utility aenerated eneray. many previously announced plants failed to materialize. With existina, or even modif"aed utility structures, thls increases the difficulty in the centralized plnnina process. Under conditions of increased transmission access and separated utility functions, the uncr.rtainty increases u separated functional make forecasts of load, local dispersed aeneration. and needs for transmission system facilities. The usiamnent or part of the centralized plannina responsibility to the market place, or coune, bas merit in that competitive market price levels would determine the entry or new supplies or aeneration u load increases required and prices responded. From a technical viewpoint and assumina currently available ,.. -4-9-270
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Power Tecllaoloala, lac. tecbDoloaiel, this may _lead to periods or tKea and defic~ont capabilities because of time lqs inherent in pluulin1 and construction cycles for bulk power system facilities. ID all or the scenarios, responsibility for system reliability and security ii vested in the trammiaion utility entity in the more extreme cues, or in r-m1inin1 utility institutions under the more moderate departures from the present industry. These orp.nizations will need to plan system expansions to accommodate future non-utility resources and requirements for the transmission systems. The results or market directed fluctuations in the pllDDed resources and transmission needs may cause excess facilities to be constructed in some periods and insufficient facilities in other periods. ID the plannina or interconnected systems, cooperative plnnina studies are carried out by non-competitive utilities to determine intersystem transfer capacities and needs and to perf'orm coordinated, reaional plannin1 studies. Data are exchanae
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,_.., Tecll ........ lac. Carrnt economic d-.,,ccbiq metbods control power aeneration levels to minimize die COit of real power production ror die whole system. Security COastraiatl IDd t"!nmitlic,n loael may be illc:luded Uld tnmmiaion sys11m incremencal losses may affect the schedules. ~,iDDiD1 reserve requinmnts Rn used in developin1 unit commitment sclledales. VAR scbedulel may be ircorponted in the economic clispacclun1 software IDd valued iDdirectly by their effect on tnmmiaion system loael. Wida independent power producen rormiq a larp pan or the 1enention resources under some or the scenariol, the economic dispatchina alaorithms will need to place a value on the worth of VAR 1eneration. spinaia1 reserve service, reaulatin1 duty service IDd the rmclledulill1 or 1eaeration ror security IDd tnmmission schedulina. Contnct tenm widl aenenton will determine the depee of dispatchability or the supplies IDd dl111 dictate the modelina or these resources ill the dispatch and unit commitment software. Meteriq, commUDication, IDd tnmletion accountin1 systems will need to be expanded ill Cuture control systems to bandle the Iara iDcrelle in volume or traDIICtions and controlled variables. Accountina for system losses and the allocation or responsibility for transmission oystem losses will be more complex. Data transmission systems between sepanted GENCOs, TRANSCO. and DISCOs will need to be developed or expanded and interora1niz.ational billin1 systems will need to be developed. Thele will require the need for installation of taraer, more powerful computer systems ud data communications systems. As the various scenariol depart from current conditions, more and more of the aenention is supplied under contract terms. If the contracts are such that the majority or the power demands are supplied under non-dispatchable contnct terms, the nature or the dispatchiDa problem will evolve to one where contract schedulina is of primary importance and mjnimizi1t1 the system production cost is not. When this happens, the very nature of economic dispatch chanaes. System incremental opentina costs (i.e., the marainal costs) will not have the same meanina they have currendy. Currendy system incremencal cost represents the marainal production cost of aenenton Cree to be scheduled, unconstrained by loldina limits or ,.. --11272
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hww Tee ... lac. tn-iMioll capacity. If coanct ud tnDIIDinioD IChedulia& become puamouat in die Ila dine tenariaa. ma,paat COIII _, raprwnt die con ol 111bltinatiq one t"I rarioc for uotber ID dlCJIUI prodactioll or NNmislioa flows. 4.1 SOLUTION Of SYSTDI-WIDE PaoaUMS The last -;or area of teclulical problems lriliD1 from die scenarios is that relaled to tbe 11111,sil. solutioll IDd resolution ol sys1n1-wide techaical problems. These problems are thole dlac iavolve die eatin balk power Sys18ID such emerpncy openbOll ud the solution or 1ys1n1 d,-mic problems. ID..,....S utility syll8IDI pnsendy bave the respomibility to iavestipte these problems. 1eek appropriate IDd economic IOlutiom. ud implement die solutions. Emeqncy openbll1 procedu.res are developed by iDdividual companies and aroups o{ coopendq utilities to prevent CIIC8din1 outqa ud ID develop methods to restore service rapidly IDd tf'f'ICiendy after major emerpncies. Trmint slability problems ud low freq-u.11C)' power oeciliatiom an stadied ud mMClill applied to prevent future occurraces. Witb i.DdepeDdeDt ~izltioas respomible for pneration and tr1asmiaio111 eutiq ill a competitive eavirownt. the voluntary coopentive efforts to solve these problems will need to be replaced. Tbe expansion of trllllmillion accea IDd the nstr1ICtllrill1 of the industry will not cause time system-wide leetmical problems to disappear. Pat problems will reappear. perhaps ill new locatiom. IDd new problems will develop as systems evolve. The structures envisioned in tbe scenario delcriptiom will produce a mon difficult environment ill whicb to anack IDd implemeat 10lutio111 to system problems. The interconaected power system1 an extremely complell ud systems ill one locality may interact with nmote systems ill 1111111ticipated ways. The divi~ad nspomibilities which accompany scenariol with separated functional responsibilities will make it mon difflcult to anack system problems and assian the costs of implementiq needed solutions. -4-12-273
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..._Tl1 ... ,lac. "Bl _.... ia 1119 1111 rwo 1e1wa ii ID lllip me 19111wibiliry ror dlele problla .alllioal ID die nANSC0 Slaff. All ..-,uiaa parties. DISC0I ad retail cu1aa1n nr1 d ia f'llail _.Hliaa coatnca WOllld be oblipled ID pan:ic:ipl ia IOlviae dlele Pl'MII ,.,,.,,rt COllaact --woald be 1111111 1d ID 1111 rwwcn ror ;ap11_ .... CD111 ia IOlviaa die problems. la die rarsc rwo -=-1111 atility ,..._ dlil ,___.biliry. QFs. IPPI. and GENCOI sltoeld bl boeed by coacnct w ID aaill ia IOlviq ad implemeatiq .,_ M1fs11rma cliff"'ICllltia a NQllirwat ror --. marbt. -,-13-,.. '>.,4 '-.
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..._ Tut 11h9' ,. lac. TICIINICAL MCl:GllOUND AND COi g...-4TJONS IN PWOIMD OIO!IASIIIP WHIII !NG. TUllllllalONACCIMAND NON-ITl'ILl'l'Y GDDATION U'7-II Au.J. Wood Hydl M. Merrill Power Teclulolotia. lac. SclllDICtldy. New York Mardi 30. 19U
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,.._T11 rhll, lac. ItNcl Of CCIOINXS
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Power Tecllaoloala, lac. UILI or CONTENTS PUFACE CIIAPTIJl 1 STRUC'l'URE OF ELECTRIC POWEil SYSTEMS 1.1 A -YYPICAL SYSTEM" ... 1.2. BISTOIUCAL PEltSPECTIVE 1.3 SDVICE STANDARDS 1.3.1 1.3.2 1.3.3 Voltqe . frequDCy ... Service Reliability 1.4 GENDATION SYSTIMS 1.4.1 1.4.2 1.4.3 Hydroelectric PlaDII Foall-F'ared ud Nuclear Steam Generation .. Combuation Turbiml ud Combined Cycle Plants 1.5 DANSMJSmON SYSTIMS . . . 1.5.1 1.5.2 1.5.3 1.5.4 1.5.5 1.5.6 1.5.7 Overbeld. Altenlati.D1 Current Trammiaion Sabstaiiou . . .. VAR. FloWI Hip Voltqe Direct Current Systems Subtnmmillion System . Undeqround Power Tnmmiaion 9Typical Trammiuion Systems 1.6 DISTIUBtmON SYSTIMS . 1.6.1 Syscem Confiauratiom and Customer C1aues 1. '7 INUaCONNlcrIONS . . . -l -277 PAGE 1-1 1-1 1-6 1-12 1-13 1-15 1-15 1-17 1-19 1-21 1-23 1-27 1-27 1-32 1-33 1-36 1-38 1-38 1-41 1-43 1-45 1-47
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Power Tecbaoloala, lac. TABLE Of CONTENTS Cco1U1ue4l CHAPTER 2 PAGE ECONOMIC OPEllATION OF GENERATION CONTROL AND INTDlCONNECTIONS . . . 2-1 2.1 INTJlODUCTION 2.2 SYSTEM OPDATIONS 2.2.1 2.2.2 2.2.3 2.2.4 2.2., Load Patterns Unit Commitment . Ec:onomic: Dis'paatcb Ef'fectl of tbe Transmission System on Economic Dispatchin1 . . Summary or System Operating Considerations 2.3 D'FICTS OP NON-UTILITY GENERATION ON SCHEDULING 2-1 2-2 2-2 2-S 2-7 2-10 2-11 AND DISPATCH . 2-12 2.4 POWIJl INTERCHANGE 2.4.1 2.4.2 2.4.3 Ecoaomy Intercbanaes WheeliD1 lnldvertent Intercbanae 2.5 POWD POOLING AllllANGltMENTS 2.6 POWIJl BJlODIIS . . 2. 7 INTIJl-UTILITY TECHNICAL ULA TIONS NERC CHAPTltll 3 GENERATION CONTROL FOR FREQUENCY, VOLTAGE AND SYSTEM SICUJllTY . 3.1 INTJlODUCTION . . . r .. 11 -278 2-13 2-14 2-15 2-17 2-17 2-19 2-21 3-1 3-1
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Power Teclmoloales, lac. TABLE Of CONTENTS
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Power Techaoloaies, lac. TABLE Of CQNJINTS Cc;o1dn1c4l PAGE 5.l IMPROVING EfflCDNCY BENU'ITS OF POWER POOLING AND BROURS . . . . . . 5-2 5.3 POSSIBLE IMPROVEMENTS IN SYSTEM OPERATIONS AND CONTROL . . . S-5 5.3.1 5.3.2 System Operatina Reliability Criteria . 5-6 Poaible Improvements in Systems Operations and Conttols . . . . s1 CIIAPTl!R 6 PROSPECl'S FOR INCREASING TRANSFER CAP ABILITY 6-1 ,.1 INTRODUCTION . . . . 6.2 LOAD DIVISION LIMITATIONS . . 6.3 VOLTAGE LIMITATIONS . . . 6.4 STABILITY RELATED LIMITATIONS . . 6.5 SYSTEM CONTROL LIMITATIONS 6.5.1 6.5.2 6.5.3 Security Related . Power Plant Raponse Deliberate System Separation 6.6 TRANS~ION cosrs . 6.6.1 6.6.2 6.6.3 6.6.4 6.6.5 Line Costs Circuit Breaker Costs . Tramf ormer Costs . . . VAR Supply and Voltage Control Apparatus Miscellaneous Costs . . 6. 7 APPROXIMATE COSTS FOR NEW AC TRANSMISSION iv -. . . . . 6-1 6-3 6-5 6-6 6-9 6-9 6-12 6-14 6-15 6-17 6-19 6-20 6-21 6-21 6-22
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Power Techaoloales, lac. TABLE Of CONTENTS Cc;o1U11edl CHAPTER 7 WHEELING AND NON-UTILITY GENERATION 7 .1 INTRODUCTION 7 .2 WHEELING 7.2.1 Technical Considerations in Wheeling 7.3 NON-UTILITY GENEllATION . 7.3.1 7.3.2 7.3.3 ECCects on Utility System PJaooio1 ECCects on System Operations Disbuned Generation Sources 7.4 WHDLING OF NON-UTILITY GENERATION 7.5 A CAVEAT ............... CHAPTER 8 SUMMAllY 8.1 GENERAL BACKGROUND 8.l ASPECfS OF SYSTEM CONTROL 8.3 TRANSMISSION LIMITATION AND TECHNICAL REMEDIES 8.4 WHEELING AND NON-UTILITY GENERATION . RERUNCES -V I) f) l '-IJ PAGE 7-1 7-1 7-4 7-7 7-17 7-18 7-22 7-26 7-28 7-33 8-1 8-1 8-6 8-11 8-15
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Power TecllaoloSI, lac. lllFACI
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Power Techaoloaln, he. PREFACE This report is one of two submitted to the Office of Technolo1y Assessment of the U.S. Conaress (OT A) by Power Technoloaies, Inc. (PTI) as part of the effort of OT A to provide information to tJw Conaress in the potential restructurin1 of the electric utility industry. This report deals with the technoloaical backaround of the industry in the U.S. The companion repo"9 -Yechnoloaical Considerations in Proposed Scenarios for IDcreuiDa Competition in the Electric Utility Industry, discusses the aeneral technical aspects of the electric utility industry and those technical issues specifically related to increased transmission access, wheelin1, and non-utility 1eneration. A number of unresolved technological issues are set forth in this report. The authon wish to express their appreciation to the various en1ineen in the industry who have been kind enoup to supply data for these reports and who have reviewed the drafts of the texts. Specifically, we w:sh to thank the American Electric Power Service Corporation, the staff of the North American Reliability Council (NERC), various memben of the NERC Operatin1 Committee and the Electric Power Research Institute (EPRI.)
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Power Techaoloales, Ille. CIIAfill I
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Power Techaolopa, lac. CHAPTER 1 STRUCTUlllt OF ELECTRIC POWER SYSTEMS 1.1 A "TYPICAL SYSTEM" Electric Power systems in the U.S. are quite diverse in both size and structural components. subsystems: A "lertically integrated electric power system includes three basic 1. generation, 2. tnnsmissil>n, 3. distribution, u well u the utility's loads. A utility system may contain all or only one or two or these subsystems. The power generation systems are the devices and apparatus used to convert one form of primary eneraY into electrical eneray. Conventional generation includes steam powered plants that use coal, lignite, gas, oil or a nuclear fission reactor for the sources of energy. In addition there are hydroelectric power plants that convert the energy in falling water to electrical energy and plants that use combustion turbines or internal combustion engines to drive electric generators. Unconventional types of aeneration are based on the convenion of solar energy to electrical energy, the generation of steam r rom wute materials and the use of fuel cells in an electrochemical cycle that generates electric power. These systems generate alternating current (ac) electric power that varies at a frequency of 60 cycles per second (i.e., 60 Hz.) Generation reserves (or capacity marains) are the difference between the total installed capacity and the annual peak load and are necessary for maintenance of the generating units and to meet unanticipated events such as higher than expected loads or the sudden forced outage of one or more of the generating units. -1-1 r
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Power Techaoloaia, lac. Fipre 1.1 shows a simplified electrical diaaram of the power system. The generaton used will produce power at voltages in the order of 12,000 to 30,000 volts (or 12 to 30 kV where tvdenotes 1000 volts) which is too low to transmit efficiently for any distance. Therefore, the aenerator voltages are raised using power transformen to the transmission system voltage levels that range from 110 kV up to 765 kV. Transformen and associated switching devices (circuit breaken and switches) ve contained in substations which also contain various metering, control, protect. system devices and data communication equipment. The c:listinction betweeL these subsystems varies from system to system and with time in the same utility. What started u transmission may be relegated to subtransmission u the load has grown and higher volta1e circuits added. Volta1e range, in the three subsystems are shown in Table 1.1. TABLE 1.1 Voltap Ru1 ,_, la Variou S.bsystems Subsystem Tnasmissic>11 Subtraasmiaion Distribution Primary Secondary Voltage Ranae 110 to 765 kV 23 to 138 kV 2.4 to 34.5 kV 600 volts and below I I I Transmission systems transmit power to the loads from generation sources and permit the intearated operation of the power system. They allow the sharing of aeneration reserves and the interchanae of power and eneray with interconnected systems. Subtransmiaion systems deliver the power from the transmission system to c:listribution substations for ultimate delivery to the customen via the distribution system. The demarcation between subtransmission systems and transmission sy.i1tems is not consistent in the utility industry. 1-2 r
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Power Teclaaolosl, lac. n, __ --DlfflllUTICII flSl'III fflTDI fflTD .....,._ t ~I 0--11 I L 0 A D I r l t 11&1aa ............ DISTitlauTNa DIITllteuTIC* ITIP-W .-ran. IUNTATIC* TIH ID ..... .,.,....., Tllt .... llUII TII ........ Plpn 1.1 SlapllON Power Systea Sabtrensmissic,11 system vol.._. levels nap from 23 kV to 138 kV and overlap the tNnaniMiots voltqes. A 115 kV line in a Jaraer system will serve as sub tNnanilliots while in a small system. a 69 kV line may be a major transmission line. Oaly )up cmtomen SIICb a major industrial plants an served directly from tbe tnNmitlion. or sub,...nsmitlio1' system. Power is c:Ustributed to tbe ultimate, retail CODSWDerS over the distribution system. Voltap levels of die COIIIIIIDIIS' devices 1enerally ranae from 600 volts for larger moton down to die t1miJiar 110 to 120 volts used for li&htina and household applience, Trullf ormen cbanp tbe voltqe levels sevenl times. The distribution s,stem itself uses voltqe levels in the ranae of 2400 up to 34,500 volts and includes all voltqe. levels below the nnae used in subtrammission. These voltaaes bave to be tnmformed apin prior to connection to the customers' devices. In residential distribution systems these transformers may be in substations for the laqer loads or in smIJer pole-top or pad-mounted transformers found in residential ana. The daily system load patterns found on U.S. utility systems aenerally have the appearance of the pattern shown on Fiaure 1.2. This is a simplified presentation which shows the mtepated toad for periods of two hours. That is, the power demand in mepwat11 (MW) in each period of two hours is shown as one half of the 1-3 r 237
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Poww Tee~ Ille. total wqy (MWh) .....,nded for the two boar period. A strip chart or the load paU8nl (tbat is. a chart with imer time divisions showina the system MW load venas time) would be quite noisy' (Le., it would contain a Jarae number or small variations at random. hip frequencies) with numerous small peaks and valleys. The repnsatation shown is typical and is adequate for eix1minin1 phenomena that take place over a loq period of time. Tbe system load is t!han1in1 continllllly and in order to have a constant frequency, the pwation lee1 mlllt also dwnp continuously in order to keep tbe two in belence at Ill timlL Wbell pneration exceeds the load the system aeaeraton accelerate IDd came the Creqwy to rise. A shortqe or p-ueration, on the odm bud, will came tbe system frequency to drop. Usen' equipment is dmiped for wtially a coastat frequency so tbat the utility's automatic aewadon control (AGC) system must keep the paeration and lOld in blJ1nc11 at all timlL Eslelltial fllDCtiom tbat an also incorporated in tbe control or the paeratioD system an tbe ecoaomic 1ebeclu1ina of the pnentioa for minirn1UD operadaa COltl Uld tbe IChecluliq of tbe local pneration to keep tbe interchange of powa witb intercouected sysW OD the scbedule that bas been established. Chapter 2 reviews tbele aspects of electric utility operation. The charlcteristks of power sysW an quite diverse in tbe U.S., because or diverse historical development patterm, available ellfflY sources and tile nature of tbe load. Systems in laqer metropOlillll areas may have extemiv,a underground subtnmmiaion IDd distribution systems and very little Jocal aeneration. In indmtrialized portions of the country the patterns may be closer to those that are frequendy labeled a typical. Power plants may be dispersed throupout the system's service territory ud load and pneration are interconnected with higher voltap lines. In still otber utilities such u rural cooperatives and some municipal system, oaly tbe distribution system may be present u the utility purchases all of ill ellel'IY from an interconnected system. [I 3) r .... I)'.: 8 ._ '-
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hw Teclla1l1 ... lac. 2000------------------------... 18000 16000 12(X)0 3 2 -10000 Q C 0 .J 8000 6000 4000 2000 0.0 0.AY I DAY 2 DAY 3 Plpn 1.2 Dally I.OM c.,.. r 1-5
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1.l. BISIOaJCAL PUSnCl1VK n. U.S. .. cttic powu s,-a. bepa lakilla ill CVNllt sbaoe about 1905 with the arty orpeinn-,a .A 9T1la Gnll Soladllr1I Grid. ( .. 1 nus wa tbe nm time a p.., ol ;M1111ar:: pcwu CDIIINIII wn broapt toptber ill a regional illllrcneerliaa. Piaaured by die Soadm1I Power Compuay, tbe illtercoDDeCtion ._.reed amcla ol die caroliall. Oeaqia. ad Tenn1111. It wa the precunor of lladndl ol sieiJrr iatl.coeeectioa fonmd by die 1930'5. 111d t a pattem for a Nmda A ..... dlal ii lrqllJ plranecl ad operalad roar ayDChronously cne.,,.... wwwa. wla ooalliaa IC 60 Hz (60 c:yda per woad). These are llOO Municipal systems, 121, OYW 900 po,.. c:ooperatiws, and nearly s,-IC dla cma ol Illa ClatDI'/ ._. larply ancipal lialltma companies, the _. ...,.. ol wu:la WII by Ecliloa's ,_,. SCrw Sladoa ill New York er,, coeeieri101II ia 1112. SU.. railway COIIIPIIDill allo IOld alw:bicity IS a side biewi w n. aodllcdoa ol ..,.,; .. cmrlllt (IC) 11. sa,mnd by Tesla's iatioll ol pnpt;,:, IC aoear, iac11u111 die rap of cntnl systems aready siace dllll ... w .........S _, ... aoc,licatioal ot elecbic power. The rirst sipamt IC 1,W carrild ~ydnwlac:bic power at 3.J kV from Willamette Falls to Po.dad., 0np. I 4-Mre of 13 lllillL n. powu ......., at die Niapn Falla project wa trlllllllinad 22 miles to laffalo Yia a 3 s,11111 (or polyplml) IC .,. ... wllicla incorporate 3 trammission wirll phw a Mlllrll ID deliww die power. The S1ICCIII of tbe Niapn Falls project sipetle,4 die ,,_,., aai"'911 ldoptiOII ol a 3 IC a tnnsmmion mediwn in die U.S. widl IC ... pinecl. tM oriaimllY Nlactad 2' Hz system pw way 1D 1Dday'1 60 Hz SMndard. flCilicaciDa 1x1emive synchronous n. powda ill U.S. lecbic 1)1111 wa drivt11 ill larp mwure by illnovations in 11tHinrioe dlYic:a SCartiaa widl die oriaiaal impetaa aivn by Edison's carbon nJe...., lipt ill 1179, a 1tnu1 or illvntiom followed. The earliest were in 1-, ,..
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Power Tecbaolosl, lac. primary devices such a 1eneraton. lamps. moton, transformen, etc. These, supplemented by a baqeolli.q control technoloay, led to a host of new power uriJinrioa devices. principally i.Ddllltrial driv and appliaces. At die same time teclmoloty improvements spurred by power demands also made poaible laqer turbillel, 1eneraton. and steam supply systems, allowina utilities to tchieYe economies of scale and nsultiD1 in a continuous drop in the real price of electricity. Tbele scale economies fostered the comolidation of the smaller local 11tiliti81 into tbe Jaraer systema of today. Laraer blocks of 1eneration and the eq,andecl popapb.ic blle of power b'Ullletiom led to hither and hiaher VIDlffliaioa 1)1111111 voltq11. Voltqel for rqioal U.S. tnaanisaion systems ...,.Uy follow one of two sequeDCel, 115 kV/230 kV/500 kV or 138 kV/ 345 kV/765 kV. The two bipest voltqel, 500 kV and 765 kV, were introduced nearly simaltueolllly in tbl l 960s. 1'blle different patterns of voltaae levels do not pnclade syachroaom intercoDDeCtiom since tc tramformen are used to connect ac circuia of dilf ereat voltqe levels. The powth in pnencor aw ud traaaniaion voltaa seemed to be inexorable But the 1000-1300 MW supercritical 1eaeration units of the 1960's ud 1970's have appuendy hlrlled out to be m11im\Jm, both technolop:ally and economically. Fipre 1.3 ill111trat11 the historic powth of sinale 1enentor and single plant size as well a sillale tninaniaio circuics. The f"ipre shows the mxim-,m capacities with tbe tl'MIPDMlioD. capability of ua overbad circuit meuured in terms of "Sur1e Impedance LOldin1 (SIL). The surae m"pedace lotdin1 of ua overhead tnnsmission ii a meuun of a circuit's effective capacity. Tbe current tecbnicel limits to 1eneratin1 unit size are set principally by properties of available materials Ul8d to build 1eneraton and turbin. Steam turbine pnera&or roton for imtance are limited by the stren1th of the f orainp. Economic limitadom result from the hip capital COit and the effects of the unavailability of some Iara uni11 plus the drop in the rate of lotd 1rowth since the 1970's. The ldvutqe of smaller 1eneratia1 UDics in ua environment of uncertainty concernina price levell and lotd powtb ii apparent comiderin1 the constraints on capital 1-7 ,..
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Power Tec:haoloal, lac. resources faced by some utilities and the need or flexibility in planning and comtructin1 new facilities. The upward march in tramm.iaion voltaaes and generating units sizes halted at the same time, due to a combination of economic and environmental influences. Rights of way bave become increuinaJy hard to obtain with costs rising dramatically. Line comtruc:tion costs have escalated with the general inflation of utility construction COIU. Environmental consideratiom conceroiog the effects of line construction, coDCerDS over land use and potential health effects have led to the current situation where 765 kV c:1111 circuits ue the maxim'IID ac lioe voltaae in use in the U.S. and Cned1 ID some areu such u the interconnection of the Hydro Quebec system to the U.S. sys1em1 hip voltaae direct cumnt (HVDC) bas often demonstrated advantages by virtue of opentill1 characteristics and decliDio1 installed costs. Direct current systems allow the direct control of power nows over the transmission circuits. This allows tbe four major networks in North America to be interconnected as well as permittiD1 the express" delivery of power and eneray between remote areas. Fiaure 1.4 shows the patterm or extra hiah voltage transmission circuits that exists in the U.S. and Canada today (1917) (Source: American Electric Power Service Corporation). 9Extn hiah voltage, or EHV circuits are those operating at 345 kV to 765 -kV. This map ii not intended to be precise but shows the major transmia~n corridon where circuit voltqes are 345 kV or higher. Underlying all of these EHV networks are extensive &rids of lower voltage transmission and subtransmission networks. A map which included all of these low voltase lines would show the divenity of systems in the country, rosing from small consumer owned cooperative systems to the laqe utilities that serve major metropolitan centen. (Note that the North American Electric Reliability Council (NERC) in Princeton. New Jeney, bas a similar map available that shows all circuits at or above 230 kV.) 1-1 -
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Power Techaoloales, Inc. 10000 1000 ;: 2 100 I C, z cc 10 --1110 1900 J -J r' ---r I I I I I I I I .,.~ ~J I I I L--1100k ... V --r J f ,. ... ---------_Li -: .J I .. --LARGEST GENERATOR ---------LARGEST PLANT SIZE ---S.I.L. OF HIGHEST TRANSMISSION VOLTAGE 1980 1980 2000 2020 YEAR Flaan 1.3 Patteru of de,elopment of maximum aeaeradon and traumlulon capacity. Traumluloa circuit capablllty meuared In terms of Sara lmpeduce Loadla1 (SIL). SIL la MW equal, a constant times the 14aare of the Hae ,olta11 la kV. n, coa1taat factor ran1es between 0.0025 ud 0.004, depeadlaa upon the number of coaducton per pb .... 293 1-9 -
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Plpn 1.4 AEP Map of Traa1ml11lo Conldon IXTAA-HIGH-VOI.TAGI TAANIMIHION LINH IN IERVICI IN NORTH AMERICA JAMJAfltY1tll ---HI.VLINII ---11eaYLINII ---141KYLINII \wJl 'II ,r HUI e ~H ..................................... ......... .,. .. -
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Power Techaoloales, Inc. The four major synchronously interconnected networks in North America are: I. The portion of the U.S. and Canada East of the Rocky Mountains except for Quebec and portions of the State of Texas. Referred to frequendy as the Eastern Interconnection. 2. The system in Quebec, the Hydro-Quebec System (HQ). 3. The system #hlch serves a large part of the state of Texas. It is commonly referred to as the ERCOT system, the Electric Reliability Council of Texas. 4. The systems in Canada and the U.S. generally West of the Rocky Mountains. This is referred to as the WSCC system, standing for Westem Systems Coordinating Council. The reasons for this separation into four major interconnections are technical, economic and institutional. The Hydro-Quebec electric system contains a large block of remotely located hydroelectric plants. Figure 1.4 shows the long EHV circuits in this system that connect the remote hydro generation to the load areas. Because of these long transmission circuits it would be difficult and very expensive to interconnect the HQ system with the Eastern Interconnection with ac transmiuion lines. Therefore, transmission ties to HQ are all de so the power flows may be controlled. The WSCC system is separated from the Eastem systems by large areas of the U.S. and Canada from are quite sparse. much larger than synchronism. the Texas Panhandle north where the population and load densities Any ac interconnections between these regions would have to be economically justiriable just to operate the systems successfully in The ERCOT system is interconnected to the Eastern Interconnection with relatively small de circuits. The reasons for lack of synchronous interconnection are technical, historical and institutional. A synchronous interconnection between ERCOT, WSCC and the Eastern Interconnection would tie all of the U.S. into one synchronous arid throuah the Texas systems. To be effective these ties and the transmission system within ERCOT would need to be much more extensive than is required to serve the systems in ERCOT. A synchronous tie between ERCOT and 1-11 ,..
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Power Techaoloales, lac. the Eastem Intercomaection system is tecboically feasible, but tbe opinion of many en@ineers in some or the utilities in ERCOT is that the system operating and relia bility characteristics are better than they would be if the ERCOT system operated in synchronism with the Eastem Interconnection. Institutional considerations, primarily concerned with rqulatory jurisdiction, have also led to the present situation where ERCOT operates separately from the Eastem Interconnection. This then is the interconnection situation as it exists. Transmission of power between the four major interconndCtions is limited by the capacity of whatever de links ue installed between them. With the exception or the ties between HQ and the Eastem Interconnection, these are relatively small compared to the size of the systems. Interconnections between the Eastem Interconnection and HQ are fairly substalltial and have grown as the eastern utilities have made arrangements to import CaaacUan eaeray to displace more expensive oil-fired generating capacity. 1.3 SDVICI STANDARDS The subject or service standards in the electric power system is an important topic when reviewina typical system characteristics and considering the possible effects and potential technical limitations to a restructuring or tbe industry. The growth or the U.S. electric power system is due in a large measure to the 1rowth in the availability of low cost~ efficient utilization devices. Motors, appliances, heating devices, lighting as well as a multitude or electronic devices are all based upon the maintenance of relatively constant voltage and a constant frequency. These standards are taken for granted, but without these service standards for the supply of electric power to the retail customer, the manufacturers of electric devices would have to install power cooditionin1 equipment to make certain that the devices would function properly aad the utilization devices would become more expensive. Power quality is another aspect or service standards. Electric power cannot contain harmonics aad voltage surges must be prevented Crom damaging customers' equipment. ,. 1-12 -
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Power Teclaaoloafes, lac. Reliability of supply i! not a standard in the same sense as voltage and frequency since there are no published requirements. Nevertheless it is an important attribute of the power systems and deserves discussion alon1 with the more formal standards. 1.3.1 Voltaae Controllin1 the voltage mapitudes supplied to utility customers is as important as supplyin1 the correct amount of load power (MW) at the proper frequency. Voltage mapitudes must be within rather narrow ranges to ensure that the customers' electrical equipment as well u the utility system equipment will function properly and not suffer damage. Excess voltqe levels, for instance will shorten expected service levels of incandescent liaht bulbs and may burn out appliance motors. Volta1e standards have been adopted for transmission and distribution voltage levels. Standards are published by the American National Standards Institute (ANSI) in their standards publication C84.l -1980 and C92.2 -1981. (5) For distribution and lower subtransmission volta1es (34.5 kV and below), the ANSI standards 3pecify one range for normal system conditions and a different, slightly expanded range for emeraency conditions. These volta1e limits may be expressed in percent of the nominal system voltaae. Table 1.2 below gives the allowable voltage limits for nominal voltqes of 120 volts to 34.5 kV. These voltage limits are for sustained conditions. Momentary volta1e variations lastin1 only a few seconds that result from switchin1 operations, motor start-up, and so on are excluded from these standards. Note that the difference in allowable voltage range between the normal and emer1ency system conditions is not large. To provide room for responding to emeraencies, power systems are usually designed and operated so that the volta1e variations stay within a narrower range than the standards allow. r 297 1-13 -
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Power Techaoloala, Inc. TABLE 1.2 ANSI Studanl Voltaae Limits throu1h 34.5 kV Voltage Limits in Percent of Nominal Normal Emeraency Voltqe Class Ooeratina Conditions Conditions (Nominal Voltqe) Minimum Maximum Minimum Maximum 120 throuah 600 volts 95CJ& 105% 91.7% 105.8% Above 600 volts throuah 34,500 volts 97.5% 105'Mt 95% 105.8% Voltqes hiaher than 34.5 kV are not normally supplied directly to customers' vtiJinrion equipment. Therefore, the ANSI standards only specify maximum voltages for these voltaae classes. When customers do receive service at these higher voltaaes it is assumed that they will supply whatever voltage control may be needed. Table 1.3 below aives the maximum allowable sustained voltages for nominal voltqe levels above 34.5 kV. Maximum voltaae is aiven in both kV and percent of nominal. TABLE 1.3 ANSI Studard Voltaae Limits aboYe 34.S kV Nominal Voltaae Maximum Voltage (kV) (kV) % of Nominal 46 48.3 105 ~-----------------------. -------High Voltaae 69 72.5 105 115 121 138 145 161 169 230. 242 Extra High Voltaae 345 362 105 500 550 110 165 800 105 Ultra High Voltage 1100 1200 109 1-14 -
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Power Tecluaolopes, lac. Transmission system equipmen~ such u power tnmsformen, may be damaged by sustained high voltages. Low voltage limitations on the system are set by voltage control capabilities and the system's operatina practices. It is not unusual to imd sustained voltages u low u 92 to 9S% of nominal at a few points in the transmission system. 1.3.2 Freqaeacy A constant frequency supply at 60 Hz is actually taken for granted in the desian of utilization equipment. The aeneral public relies on this constant frequency for timekeeping functions. In actual fact frequencies on electric power systems do deviate from 60 Hz, but rarely beyond 59.9 to 60.1 Hz. A small error in frequency causes the automatic aeneration control systems to function. Generation control systems are desiped to hold frequency constant by adjusting system generation to meet the demand euctly. Frequency standards are not subject to formalized codes but are set by the practical limitations imposed by system operations and limitations in both aeneratina equipment and customen' utilization equipment. 1.3.3 Senlce lllllaltlllty Given the various kinds of events (e.g., equipment failures, lightning strokes, storms, etc.) that may cause service interruptions, there are at least three physical dimensions that may be used to measure service reliability: L the mapitude of the outage (MWs of load interrupted, MWh of load energy not served, number of customen interrupted, etc.). b. the frequency of service interruptions (expected number of occurrences per year). c. the expected average duration of the outages. [6 9] These measures are in fact interrelated. In the past, electric system customers have exhibited a tolerance for frequiiint interruptions if they are of a short r -1-15 -
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Power Techaoloala, lac. duration. When the average duration becomes too long, the perception of service quality declines. ID the future u commercial establishments (i.e., business offices, stores, etc.) become more dependent upon electronic systems, even short duration outages may become intolerable. The system itself (that is, the operators, managen and owners of the system) can only tolerate interruptions of a large magnitude if they occur very infrequendy. One would expect that a utility executive would respond with "Never!" jf asked how frequendy the system could stand a widespread blackout or wished to experience the effects of a widespread outqe due to storm damage. The establisbment of absolute standards of service reliability using these three measures is duiJ.CUlt given the subjective nature of the varied views of the importaDce and economic value of reliable service ay the customers of the electric systems. There are no comprehensive published service reliability standards: only the de facto standards that have arisen over the yean in the industry. Efforts to place an economic value u determined by the retail consumers on the loss of service have not resulted in the establishment of universally acceptable, qwmtitative criteria. Engineering planners use various service reliability criteria measures to develop alternative plans which exhibit similar levels of expected reliability indices. Probably the best known is the "loss of load (or energy) probability' which .is a measure or the cumulative duration of the expected, long term average capacity (or energy) shortage of the system u a whole. Indices such as the expected number of customer or customer-hours of interruptions per year may be used in evaluatina distribution system design alternatives. Engineers who develop and use these measures are making comparative analyses of expected service quality. The deimition of reliable service is a subjective matter. What is acceptable to a residential consumer may not be to a large retail concern. In developing the plans for the electric systems to serve these two classes of retail customers the utility engineer may recognize this difference by designing highly redundant supply circuits to the large retail concern. ,.. 1-16 3CO
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Power Techaoloala, lac. The service reliability levels must be acceptable. They have not been quantified and codified to date. Exactly what levels are tolerable and how they are to be meuured is still not f"'irmly established. The service reliability levels of today's systems in the U.S. and Canada do not appear to be unsatisfactory in general. Whether these de facto standards that exist an too high or are minimum levels of service quality is unknown. These service reliability levels are also quite important determinants of the usable transfer capability of the transmission systems, and thus play an important role in any discussion of the ability of these systems to wheel power to a greater extent than they already are doing. 1.4 GENlllA TION SYSTEMS The mix of generation types and fuels sources varies in U.S. power systems from year to year as new capacity goes online and older units are mothballed or retired. Currendy (1987) the nuclear and hydroelectric capabilities are each about one-eighth of the total U.S. capacity while the steam plus combustion turbine segment represents about three quarten of the total capability. Table 1.4 shows the estimated total U.S. iDstalled capacity by type as of the end of 1986. [10 13] The electric energy sales in 1986 were about 2,360 billion kWh. The generation totals by various fuels are shown for that year in Table 1.5. The generation total in Table 1.4 does not equal the reported total sales because of a number of f acton including the energy losses, the reporting of imports and exports of energy and the discrepancies that arise because of different reporting periods r or generation and sales. r 331 -1-17 -
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Power Teclaaolopa, lac. TABLE 1.4 U.S. Total Ganado Capablllty u of Deceaber 31, 1986 TYPE MWim1alled CMt or Total Hydro 85,193 12.0 Foail Steam 474,063 66.9 Nuclear 93,112 13.1 Combustion Turbine 51,649 7.3 Internal Combustion 45,007 0.7 Tocal Capacity 709,094 MW 100.0% Source: E1ectrica1 World, Statistical Issue, April, 1917, pqe 52. TABLE 1.5 Electric Eaeru Gentloa By Varloa fael Types for 1986 Fuel Type Hydro Nuclear Coal Oil Gas Other Total Source: Billions or % or Total kWh Generation Shown 290.8 11.7 414.0 16.6 1,315.8 55.7 136.6 5.5 248.5 10.0 11.5 0.5 2,417.2 100.0% U.S. DOE/EIA 0035(17 /06), Monthly Energy Report, June 1987. 1-18 -
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Power Teclaaolosla, lac. 1.4.1 B,.,_.ectrlc Plua Hydroelecbic power plants convert tbe eneqy stond in water at a higher elevation by reJenina it throqh a hydraulic turbine to a lower elevation. The power available is proportional to tbe product of the flow rate times the net elefttion that the water Calls. Plants may be classified by the relative magnitude of the plant's "bad" (i.e.. apprn,:imately equal to the vertical distance that the water falls) and type of turbine or by tbe nature or the associated water stora1e System. The latter is more convenient for cliscussin1 the role or hydroelectric power in 1Chedulin1 or tbe system operation. ID some watenbedl there are very larp reservoirs that can store the inflows or water for a seuoa. a year or even loqer. These. as well as plants with smaller reservoirs. are clasluied a storqe hydro plants. They can usually be scheduled in a flexible maan so that the water is released in a pattern that is most adY111tqeoas for servina tbe electrical demand patterns. There are. however, many coastraints in operatiD1 stonae plants. ID some cases water must be released OD a iued schedule to acc:ommcvtate the requirements for iniption or the spawnin1 of f'"JSIL "Run-of-river" plul11 are dependent on tbe flow in the river for the flow throu1h the turbine and unally have little or ao storqe capacity. Plants of this type are Crequendy found on river systemS where tbe elevation drop is modest. Other types of hydro plants bave been constructed where the water is pumped into elevated raer,oirs and then releued later throqh hydraulic turbine aeaeraton. The merit of this type of plant. known as a pumped storaae plaat, is that water m..iy be pumped durina off peak load houn at a relatively low cost for the electrical energy requjnd and tben releued aenen.te power to displace relatively high cost energy dwiq periods of peak loads on the system. From an operational viewpoint hydroelectric plaats have a number of desirable f eatuns. They may be started relatively rapidly and they respond to load chanae requiremen11 rapidly when compared to laqe steam turbine aenerator units. Pumped storaae plan11 may contribute to the spi.nnina reserve capability or the system. ,.. 1-1, 383
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..,._Teclll ... ,lac. Spinnina r ... .,. ii die diffenac:e batwn tbe total 1eneratin1 capacity that is beiaa operalad ud die apK1ld peak load ud ii required to meet unexpected load dln1u11 and ll'Cldea fGn*I oa&:1111 or pnaruion. Plants tbat ue in a pumpina moda may ba slaat off rapidly to redace die system load. Pumped stonae plants mac an ia a IIUI ._. ..._ ii ia tbe stonae reservoir may be started and broa&ht up to load fairly r ... TIii two basic type1 of operadoaal 1ebeduliq (viz.. 1oq and sbon term scheduling) UI aciallld witla ba ICGDOfflC opendoa of storqe hydroelectric plants are CODCIIMCI wida dlil opdmmD -of tbe ..._ ia tbe aaention or ellctric energy. [ 14) Tbl IODa ._. ICbadaliaa or tba raoarce ii coac:erned with tbe prediction of die Gl*1l9d mf1owl iato dla nurvoir IJ'ltllll ad tbe optimum scbedulina of water -a.. a loll& tilDI s,11iod (i.e .. mwdoWII of tbe reservoir) so tbat power procbagiaa wdl 11'1 mat widloal Wllblll .,.. ud tbe reservoirs will be at the praoer leYell to KC9PC a ..., inflow Illa tbe cycle is to be repeaced. Water iDflowl an llri-tlld COlllidariDa fllCtorl such as tbe depth of tbe mow and the wadllr tildc:I of tba rep,11. 1'111 Nllllt ol die ICheduliq ii a panern or water 111111 a.. die nut moadll, ...,. ud poaibly ,-r(s). In a repon ndl tba PaculC Nortllweat where tbe area is dependent upon a reliable source of bydro power. oparatina policies must be developed so that both die probability or WlltUII wa11r by aot scbedulilla enoup 1eneration ud the risk of rvnnina oat of wa!lr by aaiDa too mucb of it are bll1ncecl Hydro system o,eruon bave developed modell IDd scbemll ror scneduliq the drawdown of the r ... 'IOirs in optimal rwuom. TIii odm type of ldledulina problem ii the sbort term problem that is concerned witJa developina optimum power production scbedulel for a day, wNk or month so mac tba 1ebedu.lld amowat of wuar ii 1111d. In tbe sbort 1'1111, storaae plants are tcbeduled ia ndl a way dlal a set. total, amowat of water is released for the P11 iod ia ncb I (uu,n that tbl COl1I of alternative electric tn1qy sources are minimized Tb.ii mlllt bl doDI obNrvina all tbe various typeS of constraints that may tut on tbl plant'1 operation 111eb u tbe requirement to releue water for irriptioa. for f1lh ladden, ecc. 1-20
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Power Tecbaoloala, lac. The 1Cbedulin1 or pumped storqe plants ii done on a similar basis with the intent or miaimizina the overall total COit or production durina a aiven short time period such a a day or week. In tlUI cae, however, the operaton usually have complete control over the inflow or water into tbe storqe reservoir. 1.4.l POIIII-Plnd ... Nllclear Sleul Geaendoa Tbe vat majority or the electric enel'I)' in the U.S. is produced in steam plants where a stam turbine ii med to extnct eneray from hiah temperature, high preaure steuD that ii produced di either a Coail-C"U'ld boiler or by a light water moderal8d nucleu reactor that serves tbe same function a the boiler in a fossil plult. n.e units ranae in size up to 1300 MW and an located in fairly large plants. The avenae sia ii IPPfl''limabtly 600 MW. Temperatures and pressures are di tbe ruae or 1000 dqrees F Uld 2400 pounds per square inch gauge for modem Coail-C"ued units. The bllic componatl or a foail-C"U'ld plant are indicated in simplified form on F"ipre 1.$. The rurmce Uld boiler serve the functions or fuel combustion and the conversion or tbe t Jedwater into biah temperature, hiah pressure steam. Bollen are very errlCient (12 to 90+41) 111d are or two buic desip typeS, the drum boiler and the once throup boiler. In the drum boiler, steam is sepanted from the heated water ill a laqe drum located on top or the boiler. The drum stores both water and steam. In tbe once throup type, steam is created in the tubes which line the boiler flll'DICe wall: and ii fed dinctly into the turbine. In both types the boiler controll are desiped to maintain ste.llll temperature and pressure, provide the control or the fuel and combustion air u well u ensure the protection of the boiler ill the cue or faillll'II and when the unit ii required to drop load and be tripped Crom the line. The turbine extnctl eneraY from the steam and drives the turbine 1enerator that produces the electrical power. Coal fired plants of recent vintaae may have flue au scrubben installed on the fUl'DICI to remove tbe sulfur Crom the stack pses. All coal fired plants have some sort of system attached to the furDICI euauat to remove fly-uh from the ltlek ...... In a coal fired plant the coal must usually be pulverized before beina ,.. 1-21 385
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Power Techaoloala, lac. blown into the furnace for combustion. The furnace auxiliaries and fuel handling equipment are simpler for a ps or oil iued unit. MAIN STUM LINE ELECTRICITY t----- TO POWER AIR STUM GENERATOR ,uRNACE. AND BOILER CONDENSATE. COOLING WATER flpn 1.5 Slapllfied Dlqna of a Steam Power Plot SYSTEM ID a liaht water moderated. nuclear power plant the reactor uses the heat released in tbe nuclear illlion procea to produce steam to drive the turbine generator. There are two buic types or li&ht water reacton in use in U.S. plants, the pnaurized water reactor (PWR.) and the boilini water reactor (BWR). In the PWR there are two isolated paths for the hot water in the reactor and the steam flowing in tbe turbine. Heat is transt'erred betwn the two isolated loops to generate the steam to expand in tbe turbine. The water which is in the reactor core and is expoaed directly to the various rmion products is contained in a separate path. In the BWR the water in the reactor core is transformed into steam within the core and allowed to expand throuah the turbine. The reacton are controlled by: 1. Usina movabl~ control rods made up of neutron absorben. 2. Controllina the concentration of neutron absorbina material that is dissolved in the water in the core (PWR). 3. Chanaina the reactor recirculatina water flow rate (BWR). The turbine aeneraton of steam plants ue controlled by a sequence of systems. To alter the eneray flowina into the turbine, steam admis.don valves are controlled. The turbine speed is controlled by the 1overnin1 system that has a characteristic that caUHS the speed to drop when additional load is applied to the turbine. This speed droop is required in order to permit 1enerating units to share load when ,.. -1-22 -
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Power Techaolopes, lac. operated in parallel. The governor characteristic is adjusted by the control that sets the required output Crom the unit. This is under the control or the automatic generation control (AGC) system that includes both the economic dispatch system that sets the optimum economic generation levels of the units and the supplementary control system ensures that the proper level of total generation is held within the area under control. Ultimately the changing of the output level of a steam generator requirei that the rate of fuel entering the furnace, or the reactivity level or the nuclear reactor core, be adjusted so that the required steam may be generated. The fossil iired plant boiler may be controlled using various control schemes to control temperatures, pressures, and the fuel feed to the furnace. In the nuclear reactor basic load level changes are accomplished by the manipulation of the control rods. Withdrawal of these rods from the core allows the fission process to increase, augmenting the production of steam. In the BWR the recirculation water flow rates may be controlled to permit load following. Nuclear reactor units in the U.S. are normally operated at ether iixed load levels or else the load levels are changed at a gradual rate to facilitate the management of the nuclear inventory of the core and avoid potentially damaging power transients. Larger Cossil rued steam plants are normally allowed to change load levels at maximum rates which are approximately 1 to 3% of the machine's rating per minute in order to limit thermally induced stresses. Both types of steam plants require time to bring them online and up to load when they are first started, or are restarted after being off line long enough to cool. Nuclear reactors that have been tripped ofC line and bad neutron poisons (boron) injected into the water in the core to stop the rission reaction will take over a day to bring back online if they are not restarted fairly soon after being tripped off. 1.4.3 Combudoa Turblaes ud Combined Cycle Pluta In a combustion turbine plant the working fluid (usually air) is compressed and heat energy is added to the working fluid by the combustion of fuel within the working fluid. The resulting hiah temperature gases are then expanded in a turbine which drives the compressor and the generator. The exhaust of the combustion turbine f"' 1-23 -
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Power Techaoloalu, lac. may be discharged directly into the atmosphere (a simple cycle) or cooled by passina the exhaust gases through a heat exchanaer where the available heat energy is used to create steam that is expanded in a steam turbine (a combined cycle). Simple cycle combustion turbines are normally applied in utility systems for peaking duty and for emergency reserve capacity. Typically they have been units with relatively expensive fuel costs and low installed, capital costs, characteristics which make them suitable for applications where they will be expected to operate only a relatively r ew number of hours per month. Efficiencies are typically in the range of 25 to 304I& for older units but are expected to be over 30% for advanced design units which will use hiaher operatina temperatures. Unit capacities range up to over 100 MW for the advanced desian combustion turbines with the averaae size of the installed simple cycle units being much smaller. Combined cycle plants aenerally have much better efficiencies than simple cycle units, approachina or even exreec:Uoa the efficiencies levels of the large steam turbine units. Fiaure 1.6 shows a block diagram of a combined cycle plant with r our combustion turbines and one steam turbine. The exhaust of each combustion turbine flows throuah a ht recovery steam generator (HRSG) that creates steam r or use in a steam turbine. Plants may be designed so that a steam turbine boiler may be separately iued to increase the plant's capacity and to ensure operation of the steam turbine durina outages of the combustion turbines. Combined cycles have been desiped with one to u many u r our combustion turbines. The output level of the combustion turbine driven units is controlled primarily by controllina the fuel input into the unit. Some degree of control may be provided by control of the gas paths in the system. Fuels may be oil or gas. Combustion turbine power plants may be started and brouaht up to load rapidly. A new type of combined cycle plant, the intearated gasification combined cycle (IGCC) plant has been demonstrated recently on the system of the Southern California Edison Company [ 1 SJ. This plant, the Cool Water Plant, converts coal to medium BTU gas for use in a combined cycle plant. This type of plant has the advantaae of using a low cost and abundant fuel in a plant cycle that offers the 1-24 ,... 308
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Power Teclaaoloales, lac. opportunity to achieve high plant efficiencies in relatively modest sized capacities. ID planning for system growth an advantage claimed for this type of plant is that it may be constructed in modular stages starting with simple cycle units, progressing to a conventionally fueled combined cycle plant and ultimately to a coal consuming IGCC plant. flpn 1.6 A coablaed cycle plut with foar combudoa turblaN and a ...... tubl 1eaentor. Grr deaotN a combudoa, or IU turbine aad T the steam tarblae. Although there has only been limited experience in operating this type of plant, one might hazard the opinion that commercial plants of this type will probably be operated u base load units because of the complex interactions of the chemical pJants used for coal gasification and scrubbin1 of the fuel gas with the power generation cycJe. Theoretically there is no reason why this type of plant could not be used for supplying varying loads on the electrical system, but because of the complexity of the plant and the time required for start-up it is doubtful that an IGCC plant is suitable for two shift operation (i.e., daily economy shutdowns) much less for peakin1 duty. Cogeneration power plants which produce both industrial process steam and electric power are expected to supply a significant portion of the future demand growth for electric ener1y [16). With the enactment of the Public Utility Regulatory Policies 1-25 3C9
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Power Techaoloales, lac. Act of 1978 (PURPA), industrial concerns were offered an added economic incentive to establish new coaeneration plants and the opportunity to sell excess generation to utilities at avoided cost". ID industries requiring steam for their processes, the installation of new co1eneration facilities: 1. Provides a supply of process steam. 2. Offers the opportunity for self-generation of the electrical energy requiremen11 of the planL 3. Offers the opportunity to sell the excess power generated to the local utility and recoup the investment faster. Smee 1978 many concerns have constructed new cogeneration plants based on the use of combustion turbines in combined cycle confi1urations that produce both process steam and electrical eneray [ 17]. The particular cycle design used in a given plant is dictated by the need for a reliable source of process steam as well as the economic considerations involved in sellin1 the excess electrical energy and capacity to the local utility. From a technical point of view, assuming that all the possible problems reprdin1 the electrical interconnections, etc., have been solved, a major potential utility operatin1 problem associated with these plants is that the level of the cogeneration plant electrical output is dictated by the need for process steam. The resultina power generated must be absorbed somewhere. The earliest types of co1eneration plants used automatic extraction steam turbines where the level of electrical output of the unit may be controlled over a wide ranse while still satisfyina the need for a siven level of process steam generation. The level of steam generated by a co1eneration plant using a conventional combustion turbine is dictated by the eneray in the exhaust pses from the combustion turbine and there is usually only a small nnae of control of the electrical generation level for a aiven rate of steam production. This may complicate the coordinated operation of a utility's power aeneration facilities with cogenerators if the utility area bas too many co1eneration plants of this type of design. 310 1-26 -
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Power Tecluaoloala, lac. 1.5 TRANSMIMION SYSTEMS Power trammission circuits are aenerally in the 110 kV class or above. Most of the transmission in the U.S. consists of three phase, ac overhead construction with some hiah voltaae de used for special situations. There are segments of underpound cable used r or transmission, but t.hese are relatively rare when compared to the installations of overhead transmission lines because the cost of underpound transmission is usually much more than for overhead transmission. At the end of 1986 there were approximately 612,000 circuit-miles of overhead lines in the U.S. with voltaae levels at, or above 22 kV [10]. Of these, about 315,000 circuit-miles, a little over 50%, were at transmission voltage levels, 110 kV and above. The EHV transmission system shown on Figure 1.4 represents about 12% of the total circuit miles of the transmis.,iQD system with most of the circuit-miles of lines at voltqe levels of 110 to 230 kV. 1.5.1 O.erlaead, Altenaada1 Caneat Trammluloa Figure 1. 7 illustrates the construction of two types of towen used in the building of 500 kV circuits. The towen support the phase conducton using insulaton to keep the energized conducton away from the tower structure and from each other. Ground, or shield wires are supported at the top of the structure to protect the phase conducton from direct liahtnina strokes. The spacings and dimensions of the tower structure and the width of right-of-way required are determined by the voltqe class of the circuit considering the need for air insulation to prevent the enerpzed circuits from flashing over (i.e., arcin1 between the energized conductor and tower), the allowable electromaanetic field strenaths on the ground and the prevention of hiah levels of radio interference patterns and audible noise. The reason for the hiah voltaae is the need for high capacity, low loss lines. The power transmitted is proportional to the product of the circuit voltaae and the phase current. Power transmitted may be increased by raisin& the current while usin1 larger conductor diameten to hold down the losses. In fact, at the extra hi&h voltaae (EHV) levels of 34S kV and above, it is usual to find circuits r, 311 -1-27 -
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Power Techaolqles, lac. constructed with 2, 3 or 4 conductor bundles used in each phase. This method of increasina circuit capacity by raisina currents has its limitations, both technical and economic. It is mon practical and economical to increase transmission voltage levels u the need for hiper capacity circuits has grown. For all practical purposes the ma:Jimn.m loadina capability of a given voltage class of circuit is proportional to the square of the nominal voltage. "' '\ 15' C b u a: ,. ... io Flpn 1.7 Typical 500 kV Pole-Type Structures used oa Preseat Systems The concept of Surge Impedance Loadina (SIL) is useful in discussina the limitations of overhead ac transmission circuits. The sidebar on SIL loading limitations points out that. these are determined for idealized, straight away, express transmission. SURGE IMPEDANCE LOADING RATINGS FOR OVERHEAD TRANSMISSION LINES The concept of Surae Impedance Loadina (SIL) ratinas for three phase, overhead power transmission lines is a convenient and shorthand way of recognizina the 1-21 -
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Power Techaolo1la, Ille. effects of voltage class, distance and loading as parameters of an overhead circuit [11, 19]. r~ the surae impedance of a circuit is related to its physical parameters: conductor diameter, spaciq between phases, number of conducton used in each phase "bundle, and height above the ground plane of the conductors. It is also the value of the resistance that may be used to terminate the circuit so that no reflections take place of transients such as caused by lightnina or circuit switchina. ID the ~teady state on an ac circuit, terminating the line with a load demand where the load power is equal to the square of the voltage divided by the surae impedancei results in a situation where no additional voltaae support need be supplied at the load end of ~e circuit. This loadina is sometimes referred to as the natural loading of the line. When studies are made by electric power engineers of the maximum feasible circuit loadinp for different voltaae levels and straiaht-away transmission distances, line limitations are surprisinaly independent of the circuit voltaae rating when the loadinp are expressed in normalized power units based on the SIL for that voltaae clul of circuit. (The maximum feasible loadina levels in MW9s are normalized by diviclina the MW value by the SIL of that voltage). The maximum feasible loadin1s are determined by limitations imposed by: 1. Thermal characteristics of the phase conductors. 2. Voltage limitations of the circuit terminals and the related requirements for V ARs. 3. Various typeS of system stability problems that may arise for Iona distance transmission. Because of practical constraints on the physical characteristic parameten of overhead, hiah voltaae line construction (i.e., spacings required for safety, insulatina strenath, etc.), the surae impedance values of overhead, three phase ac transmission circuits are almost independent of voltage level and are, in fact, mostly dependent upon the number of conducton used per phase. Lower transmission voltaae level ,.. 1-2, -
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Power Techaolo1ln, Ille. circuits, below the threshold of extra high voltage (EHV) lines are usually coDStrUCted with a single conductor per phase with the resultina surge impedance varyina between 366 and 400 ohms. At and above 34S kV, two, three and four conductor bundles are used in order to reduce the impedance of extra hiah voltage circuits and increase the current carryina capacity of the line. The table below shows typical surge impedance and SIL levels u a function of the nominal voltage class of the transmission line. OVERBIAD LINE SURGE IMPEDANCE LOADING DATA FOR TYPICAL CONSI'RUCJ'ION PRACI'ICES Nominal Voltage No. of Conducton Surge Impedance SIL (kV) per Phase (OHMS) (MW) llS I 400 33 138 I 400 48 161 I 400 65 230 1 400 132 345 2 283 420 500* 3 248 1010 76S* 4 258 2270 Reprded u EHV levels. Practical economic loadina limits for overhead transmission circuits are bued on both the technical limitations discussed and economic evaluations of required voltage suppo~ additional switchina stations, etc. Typical loading limits are independent of voltage level when expressed in terms of SIL ratinp. They are dependent upon the transmission distance. The table below indicates these limits. Distance (Mi.) 50 or less 100 200 More than 200 PRACTICAL ECONOMIC LOADING LIMITS FOR STRAIGHT-AWAY TRANSMISSION Loadina Limitations Limitation Cause (Normalized in SIL Terms) 3 x SIL Thermal 2 x SIL Voltage-V ARs 1.45 x SIL Voltaae-V ARs approximately Ix SIL Stability 1-30 314
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Power Techaolo&les, lac. These data provide gllidelines for system planning engineers in selecting transmission voltqes.. Circuit capacity requirements are the primary determinant of the required transmission voltqe level Specific circuit requirements and limitations must be investipted and determined in terms of the actual system and its operating and reliability-security practices. These guidelines are a useful concept in transmission planning. Suppose we wish to consider alternative voltages for the reliable transmission of 1000 MW out of a power plant for 100 miles. This distance is convenient since the maximum loading is twice the SIL. Reliability practices in this example are taken to mean that the power must be transmitted even when a single circuit is lost. Suppose we use the data in the rust and second tables to determine how many circuits of each voltage class are required. kV Class 2 x SIL Number of Circuits (MW) (MW) Needed for 1000 MW 115 66 17 138 96 12 161 130 9 230 264 s 345 840 3 soo 2020 2 165 4540 2 Under normal circumstances a system designer would not wish to use a transmission voltaae level less than 230 kV and would probably sugaest that an EHV level be used. r nl ,._ ""I V '-' 1-31 -
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Power Tecbaoloales, lac. Express transmission is seldom the case in actual systems as circuits are used to deliver power to !Dtermediate loads, interconnect adjacetnt systems to facilitate the sharing of economy eneray and system capacity reserves and to bolster up the system in the case of emeraencies. guides in pJaooiog transmission systems. 1.5.2 Subltadou Even so, the Sil. concepts provide useful Power transmission substations are an integral part of the transmission network. These stations serve four basic functions: I. They switch elements in and out of the system using high voltage circuit breaken that can interrupt load and fault currents and various disconnect switches that are not intended to interrupt high current levels. Protective relayin1 systems are connected to the circuit breaken and are used to sense abnormal circuit conditions and initiate the circuit openings. 2. They contain the various types of transformen that are used to step up or step down the voltages in the system. 3. They contain various devices used to regulate the system voltaaes. These include tap chanaen on the transformen and various types of VAR compensating devices. 4. They contain meterin1 and communication devices and systems to collect and transmit data to control centen and to provide information to local protective relayina systems. Different types of stations will have different names accordina to the intended function of the station. Thus there are switching stations, step-up or step-down stations and distribution stations. The configuration of any station may be simple or complex with the difference bein1 due primarily to the level of redundancy required in the switching arranaement. The level of redundancy in the switching scheme may be due to circuit confi1uration requirements and station reliability considerations. The electrical connector used to interconnect the various devices within the station itself is known as the busbar. Where space is not a limiting constraint on the 1-32 316
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Power Tecluaoloala, lac. station layout, air ii used u the primary insulatina medium. If space is a limitation (which is frequendy the case in urban areas). au insulated substations may be constructed. Substations that contain measurin1 and communication systems provide information to the system operations center which needs to have up to the minute data on the system's power and VAR flows, circuit confiauration (i.e which circuits are closed and which are opened), and the voltaae levels at various key points in the network. These data are used in the real time schedulina of the system. 1.5.3 VAil Flow R.elctive volt amperes, or V ARs, are aenerated, absorbed and flow in ac power circuits. Real power that accomplilhes work in the physics sense is measured in terms or MW Uld ii the power delivered to the load to be transformed into beat, liaht or physical motion. The ac circuits used to transmit this power all suppon electromapetic rldl that ston eneru temporarily and that are requind to accomplish the trlmmit!don of power IIDd the transformation of the electrical power into some other form. For eumple, overhead transmission lines are surrounded by m1netic rieldl which ston eneray. They an in proximity to around, an imperfect conductor. so tbat electric rieldl exist between the phase conducton and around u well a between the conductors. ne.. electric fields ston eneray u well. The m11imum rate of cban1e of the stored eneqy determines the V ARs stored in these electric and mane~ fields. V AU A NON-MATHEMATICAL EXPLANATION Perhaps one of the most difficult chores that can face a power system enaineer is that of explain.ins the concept of "V ARs to the non-technical person. 317 1-33 -
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PowwTec ......... ,Iac. AA ualou may belp to UDdenlaDd thil pbellomena. Suppose you were to use a wmlburow to move a load or bricks aloq a level road. To do so, you must rust raill tba lwnd,_ or die wmlbarrow. Wbea you do you are storina potential IDIIIJ ill tba sy1111111. (It ii wily dilcbaqed by droppiJla the badles.) Next you tpply a rorce to tbe bind,_ ill a horizontal direction to move the load. You are doiaa work ill tbe pb,aicl IIDl8 by applyina th.is force to a mus to move it. SIDriq pol8Dtial IDll'IY ill tbe system by raisiq the bandies was not your intent; bat it WII 11ecry ill order to do tbe aaef'ul work. The beiaht of the wbeelblrrow lwnd,_ ii ualoto to tbe power system volt:qe. A.I you move the w-1burow ap 111d dowll hil1I tbe beipt cbana-just a voltqes cbanae ill power sysW Ilea poww no ... tbroap tbe circuitL Sacla ii also tbe CIII with VARI. It would be nice to be able to transmit power over u IC 1J1t1111 without beiq concerned with V Alls. But they are necemry bec:1-die circuit elemall Ill illvolw me form or wray storqe. The term VARI ltudl ror Volt Ampens Ractiw and ii a short band way or delcribina the 1'&11 of IMIIY S10rap ill a lllctric circuit that ii subject to siDUIOidal varyin1 cmr111t no.... (Cunat no... are IIIIIIIU'ed in Amperes and electric potentials in volts.) ID a de elactric circuit wi.ere die voltlpl and currents are constant after tbat tab place have settled down, there is no cban1e in lllll1Y stonp ill t!ae cin:ait. Tberef'ore, ill a de circuit the VARs bave no usual meenina. Molt electric power circuia are alternatina current (tc) circuits where the currents 111d voltlpl 01Cillate siDU10idally at a comtaDt (requency of 60 cycles per second (or Hz.) Therefore ill an IC circuit eneray is beina stored in and discharged from circuit elemllla VITY cycle. Collducton store eneqy in the maanetic fields which surround tbe conductor and. aeray ii allo stored in the electric fields between the condacton 111d between the conducton 111d polllld. Beca1111 tbe IC current ii not comtaat but ii cban1in1 continuously the rate of eaeray storqe ii allo cbanaina. VARI are defined u the measure flf the maximum rata of eneqy storqe ill the rieldl usociated with the circuit elements. ,, 318 1-k
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Power Tecbaoloal, lac. All overhead trammission line, for example, stores eneray in the magnetic fields that surround the conducton and in the electric fields that exist between the conducton IDd the around. A power tramformer or motor stores eneray in the strona maanetic fields that ue an intqnl part of these devices. When power is transmitted over the line there will be a flow of V ARs u well. The VAR flow is necessary to support the stored eneray and occun because the eneray storage in the electric and manetic fields is cbangina each cycle. heavy, the stored eneray levels are hiah and the power circuit may need to supply ldditional sources of V ARs. When the power flow is system at the ends of the The flow of V ARs alona the circuit causes voltaae maanitudes to cbanae. The v AR flows interact with the natural chll'acteristics of the circuit that impedes the current flow to cause these voltaae changes. Under light loading conditions VAR flows may came voltqe rises. Under heavy IOldina conditions they will cause voltqe decreaes. External VAR supplies ud voltaae control devices such as tramformen with controllable turns ntios (i.e., tap chlDama trlDSformen) may be needed to keep the voltaae levels within reasonable tolerances (e.a., :t 5% of the nomiml voltqe.) The current required to support the constandy charaing and discharaing energy storqe must now Ilona the same circuit paths u the real power component of current This flow of V Alli bu two major effects on the transmission circuits and system. It UNS up a portion of the physical capacity of the circuit causina real power loaes ud heatina of the circuit elements. The second phenomena that results from the VAR flow is the effect on the voltaae magnitudes in the circuit. This later effect is complex and depends upon the exact circuit conditions. For eumple, durina very liaht loadina conditions on a Iona EHV line or on a hiah voltqe underaround cable, the flow of V Alli required to store eneray in the electric r.elds surroundina the tctive conducton will cause the voltage to rise along the circuit in the direction of the real power flow. For very Iona circuits this voltaae rise may cause the receivina end of the circuit to exhibit voltages higher than those allowed by voltaae standards, endanaerina the circuits and apparatus in 1-35 -
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Power Tecbaoloala, lac. the substation. On the other band, when the circuit is carrying a very heavy flow of real power, the accompanying flow of V AR.s will cause a voltage decrease at the receivin1 end which may require the supply of V ARs at that point in the system to boost the voltage. These VAR and voltage phenomena ue particularly important considerations in el\ablishin1 system design requirements and allowable system operating procedures. When systems ue bein1 desi~ transmission engineers may specify the installation of various VAR compensators to 1enerate additional V ARs to boost voltages or to absorb excea V ARs to reduce the voltage. Shunt connected reacton will absorb V ARs and prevent abnormal voltage rises for light loads. Shunt capacitors will supply VARI to support terminal voltqe levels during heavy loadings. Devices such as static VAR compensators or synchronous condensers (a rotating machine similar to a aenerator that only supplies VARs, not MWs) are controllable devices that may be med to supply VARI at one time and absorb them at another. Voltage drops alona an overhead line may also be compensated to some extent by installation of series capacitors in the line itself. These devices will automatically reduce the mqnitude of the voltaae change alon1 the line. Undeqround cables store more ener1y in the electric fields surrounding the conducton than in the case with overhead circuits. The reduced spacings between the conductor and the effective around, the external cable covering, and by the insulatin1 materials used with high dielectric constants, (a measure of the medium's ability to support an electric field) cause this phenomena. Therefore in cable transmission systems the heatina effects due to .,ower losses and use of circuit capacity caused by the flow of V ARs are much more important than in overhead lines. 1.S.4 Blab Voltaae Direct Cuneat Sy1tem1 Although the vast majority of the transmission circuits and capability are ac, there are some important installations of high voltage de systems [19, 20). These are special situations such as the requirement for the delivery of blocks of power from remote sources to load centers and the interconnection of asynchronous systems f"\ 320 1-36 -
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Power Techaoloales, lac. such as the ERCOT re1ion of Texas and the Eastern Interconnection or the interconnection of the Hydro-Quebec system to the Eastern Interconnection. Direct current overhead circuits consist usually of a positive and negative conductor opented at high de volta1es such as 400 kV. The terminal stations include rectifien and associated controls at the sending end and inverton and controls at the receiving end. Some de circuits are designed so that the power flows may be revened while others are intended for flows in only one direction. In some cases where asynchronous systems are interconnected via de, there will be only a "back-to-back installation of rectifier and invertor without the need for an actual de transmission line. The advantage of de transmission is the inherent ability in the de system to control the level of power flow throu1h the circuit. In ac systems this type of control is indirect in that power flows may be adjusted by shifting generation levels or effecting switchin1 operations to readjust power flows. In an ac system the power and VAR flows will distribute themselves automatically to conform to the laws of physics that aovem the behavior of the currents and voltages. In a de installation power flows may be controlled precisely by controlling the rectification and invenion processes. Direct current circuit capacities are limited by the thermal capacities of the transmission circuits and the capacities of the terminal equipment. VAR supplies enter the picture only in the interconnected IC systems. Direct current systems that parallel high voltage IC interconnections may be used to reduce, mitigate or prevent the dynamic instabilities that may arise in the ac system [21). This capability may play a significant role in a decision to use a de link instead or IC if stability problems are important in the particular region. In many parts of the world underwater de cables interconnect power systems that are sepanted by large bodies of water. These installations are preferred over ac cables because of the desire to interconnect asynchronous systems, control power 1-37 r~ ')1 '-...,
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Power Tecbaoloales, lac. flows, and because the transmission distance may be too Iona to be practical for an ac cable system. 1.5.5 S.btruamluloa SystelBI Subtransmiuion systems are exactly what the name implies, transmission systems that are "below' the transmission systems. They serve the function of deliverina power from the high voltaae transmission system to the major distribution substations. Voltqe levels are less than 115 kV and areater than the usual hiahest distribution system voltaae level. The distinctions between subtransmission and transmission varies from system to system. A 69 kV class circuit may be a subtraasmiaion voltage in a large system with a relatively hiah load density while a 69 kV class circuit may be a major transmission link in a rural area with sparse load density. The components of the subtraasmission system (i.e., lines, transformers, breakers, etc.) are the same u those of the transmission system, althouah of a different voltaae class. ID utility systems where increasinaty hiaher transmission voltaae systems have been installed u the load bas arown, the subtransmission circuits may parallel the hiah voltaae circuits and become overloaded if power that is intended to flow on the hip voltaae lines divides and flows over the lower voltaae, subtransllUSSion circuits. In some systems this has caused subtransmission circuits to be opened at one end to avoid parallel operation with transmission circuits. This results in servina load area substations radially. 1.5.6 Uadersrouad Power Trusmiuloa As of 1982 there were approximately 2900 circuit miles of ac underaround cable in the U.S. operated at voltaaes of 69 kV and above [22). Table 1.6 shows the estimated distribution of these installations for transmission voltaae levels for various regions of the country. The applications are, for the most part, in densely populated metropolitan areas where it is increasingly difficult, if not impossible, to install overhead power transmission circuits. 1-38 -
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Power Techaoloales, Ille. The loading of underground cable circuits is dependent upon thermal limits primarily. These in tum are a function of the cable design, the cooling system, the thermal characteristics of the soil that the cable is buried in, and the length of the circuit. Typical cable circuit maximum ratings as a function of cable nominal voltage class are shown in Table 1.7. Ratings of overhead circuits of the same voltage class are shown in the last column for comparison [23). TABLE 1.6 Cumulad,e Ol'Clllt MIies of Hl1h Voltaa Power Traa1mluloa Cable la tbe U.S. (Esdaate u of 1982) REGION CIRCUIT MILES 115-161 kV 230 kV 345 kV 500 kV New York-NJ Metropolitan Area 700 100 200 Philadelphia-BaltimoreWashingto~ de Area 300 200 -Great Lakes Urban Areas 400 so 20 New England 100 -20 Los Angeles 200 35 San Francisco 150 75 -I I Urban Areas in Florida 150 50 -I I Other Areas 100 20 10 Totals 2100 555 250 Source: "Underground Cable Systems", Coune notes, Power Technologies, Inc., Schenectady, NY, 1982 revision, unpublished. f', -1-39 323 ------6 6 I I I I i I I i
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Power Techaoloaln, lac. TABLE 1.7 Typical Uaderaroaad Cable Ratla1s Voltaae Class (kV) Typical Rating (MW) Ratings of Typical Overhead Lines (MW 115-161 220 100 200 Source: 230 330 200 400 345 450 400 1000 500 700 1000 2500 "Underground Power Transmission, Report prepared by A.O. Little, Inc., Oct. 1971, published by the Electric Research Council, 90 Park Ave., New York, NY 10016. The four basic types of cable systems suitable for use at voltages of 69 kV and above are: 1. Oil-filled, pipe-type cable in which the cable is installed in an oil filled pipe. The oil, used as the coolina medium, is under prwure within the pipe. 2. Oil-filled, self-contained cable where the cable is directly buried in the ground. 3. Solid dielectric cables where the insulating material is solid and the cable is direcdy buried. 4. Gas-insulated cables where sulfur hexafloride is used as the insulating and cooling medium. These are used primarily in gas insulated substations. The type of cable, its specific desian and the heat transfer characteristics of the soil surrounding the cable in each underaround installation affect the cable rating. (' 1-40 -
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Power Techaoloales, lac. Cable transmission systems are generally several times more expensive to install than overhead circuits. Because of the close spacing between the active conductors and the cable sheath (or ground) the electric fields in a cable are very strong and they aenerate many more V ARs per mile than an overhead line [24]. This means that the reactive component of the flow in the cable, the V ARs, are much higher even under normal loading conditions so that cable capacity is limited by this phenomena. System operating requirements may dictate the need for VAR compensation at the tennioals of the cable. 1.5.7 "Typical Trusmluloa Systems From this brief introduction to the generation and transmission systems, it should be apparent that there are many combinations of components that may make up a bulk power system. As a matter of fact, there is no single "typical system" pattern that represents the large variety of electric utilities in the North American systems. Northeut In the oortheastem portion of the country, there are EHV circuits used to interconnect systems u well u to permit the importation of blocks of power from Caaada Much of the EHV network is essential to the operation of the three centrally dispatched power pools, PJM, NEPOOL and the NYPP. Along the seaboard the urban areas have very hiah load densities and contain underground transmission to deliver power to urban centers. The load densities in the other areas away from the large urban population centers oo the seaboard are much less and the transmission systems are used to connect power generation stations into the network, provide interconnection capability and enable express delivery of Canadian energy to the U.S. systems. Sou&bcu& In the Southeast regions load patterns are mixed. Generation stations are located throupout the reaion and the EHV network has grown to interconnect the region, facilitate power transfers and the operation of centrally dispatched, holding company operated power pools, and connect generation to load areas. EHV lines from (' 325 1-41 -
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Power Tecbaoloales, lac. southern and central Florida allow the interchange of power between the systems within the state and the states to the north. Mldpst In the midwest and Great Lakes areas the systems are interconnected with an extensive EHV network. Major load areas are concentrated around the Great Lakes region industrial belt. An extensive EHV network permits the integrated operation of the systems within the American Electric Power Company. Ima In the Texas area the major load areas are near the Houston and Dallas areas and the other cities in the state. The transmission network is a 345 kV "backbone" system that ties toaether the major systems in the state. The western part of the state is served by lower voltage lines. The systems that belong to ERCOT are interconnected uynchronously to the other systems in the Eastern Interconnection by means of de ties. PJ1l11 Statc, In the plains states the load centen are 1enerally located in or near widely spread urban areas. The transmission is more sparse and has been installed primarily to interconnect load and generation. In the northern portion of this central resion of the country there is transmission installed to Manitoba and to the west of Minnesota to connect remote 1eneration to load areas. In the middle of the country, from the Texas Panhandle north, both the population and electrical load densities are low. Transmission is generally of a lower capacity and has generally been installed to interconnect load and generation. There are few EHV circuits in this reaion. Watcrg Stata The western systems are interconnected extensively. Figure 1.4 shows only the EHV and major de circuits. The western areas are in fact interconnected with a transmission system that approximates the shape of a giant "douahnut." The eastern circuits closina the loop are lower voltage than those on the western side. The 1-42 ,...
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Power Tecbaoloales, lac. EHV lines into Canada connect the Canadian hydroelectric generating plaots to the western U.S. systems. A :t 500 kV de interconnection provides ao express transmission path between the hydroelectric resources in the Pacific northwest and the major load centen in southern California. Southern California is interconnected with areas in Arizona and New Mexico that contain major generating plants. The operating practices, transmission related technical problems and transmission limitations faced by systems in the various regions differ because of these different system configurations and area patterns of load and generation. 1., DISTRIBUTION SYSTEMS There are approximately 100 million customers of the electric utility industry in the U.S. (13). All but about one percent are served from a distribution system. The distribution system is an extension or the transmission and subtraosmission systems designed to transmit power to serve the ultimate customers. The transmission system delivers "bulk power" to the substations where the distribution system actually distributes the power to the various loads. The distribution system voltqe levels include all of those below the range in the subtransmission class. It is not uncommon to have major industrial customers served directly from the subtransmission system. In these cases there is a separate substation dedicated to servina this rum and the customer bas his own internal distribution system. The substation may be owned by the utility or the industrial firm. Metering, protective and switchina apparatus would be located in this station. The distribution system is subdivided into primary" and "secondary" systems. Fiaure 1.8 illustrates the interfaces between the subtransmission, primary and secondary distribution systems. The subtransmission system delivers power to the distribution substation where a transformer reduces the voltage to that of the primary system. The primary distribution system includes all of the facilities between the distribution substation and the distribution transformers. The secondary distribution system includes the distribution transformer and the circuits up to the service entrance point of the ultimate customen. 1-43 327
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Power Tecbaoloaln, lac. TO auuc POWER SUPPLY SUITRANSMI SSION LINES OISTRl!UTION SUBSTATION TO SULK POWEii SUPPLY ___ SECONDARY @:Ci CIRCUITS PRIMARY FEEDER p c p ::::r:.., __ OISTRIBUT10N TRANSFOAMER flaun 1.8 Interface BetwHa Subtraumluloa, Primary aad Secoadary Dlatrlbadoa Systems The subtrammission and primary feeder circuits are three phase circuits. Primary lateral circuits, bnnchin1 off of the primary feeder circuit, are usually sinale phue, as are the secondary circuits which deliver power to the consumen' service entry points. Secondary circuits are laid out to serve groups of customen in a nei1hborhood. Note that the system shown on Fi1ure 1.8 is servina these customen with a radial feed pattem. That is, power is only delivered to the secondary systems throu1h one path. ,1-44 328
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Power Tecluaoloates, lac. The complexity in the subtransmission and distribution circuit configurations arise naturally out of the desire to supply more reliable service. For example. the load area shown on Figure 1.8 might by tied to another substation through a primary feeder circuit and the switch that was normally open. The tie switch could be closed in case that Nrvice to one or the other of the substations was interrupted by the opening of a subtransmission circuit. The configuration may be even more reliable by havin1 major distribution substations fed by at least two subtransmission circuits at all times. Then, when and if a circuit fa ult should occur on any one sub transmission line, it could be removed from service automatically by the protective systems without interruption of service. 1.6.1 Syste Coafipndou aad C111tomer Claues This whole concept of providing reliable service permeates the designs found in the various primary and secondary distribution systems. The primary system contains the hiper nnae of distribution voltqes, typically between 2.4 and 34.5 kV. Small industrial customers and commercial customers may be served directly from the primary i,stem with three phase or sinate phase service. The lower voltage portion of the distribution system, the secondary system serves the residential and small commercial customers at voltages that are typically below 600 volts. Load cateaories and the size ranae of typical loads are: Industrial Commercial Residential 10 to 100 MW 200 kW to 10 MW S to 25 kW per residence Other customer classes may include agricultural loads, irrigation loads, street liahtin1 and service for municipal uses. The service to residential customers may be overhead or via underground systems, known as URD systems standing for underaround residential distribution. Overhead circuits are less costly to install but require poles and rights-of-way and are r 1-45 -
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Power Teclmoloales, lac. subject to outages caused by weather, falling tree limbs and so forth. URD systems are more costly to install but an protected from the elements. Commercial loads are frequectly served by systems which provide alternate feeds through different primary circuits. The degree of redundancy depends a great deal on the size and relative importance or reliability to the load. A shopping mall in a suburban area, for example might be fed by a looped primary system where the load is served by two primary feeden connected to the distribution transformers. The commercial load in a downtown area in a major metropolitan center may require the ins1allation of an undeqround, secondary network configuration such as that shown in simplified form in Figure 1.9. This complex secondary network provides redundant feeds to the commercial customen via the secondary network and the multiple primary feeden delivering power to the network. DISTRIBUTION SUBSTATION NETWORK TRANSFORMERS PRIMARY FEEDERS Flaare 1.9 Secondary Network (Simplified) 1-46 f"' SECONDARY NETWORK II GRID"
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Power Teclaaoloal, lac. Protective systems in the distribution systems range from circuit breaken in clistribution substations that open automatically when faults are detected by the protective relayina system all the way to fuses on secondary distribution circuits that open circuits subject to overload currents. A major task in the operation of the clistribution systems is the desip and operation of the protective systems. Many of the breaken and switches applied in distribution circuits are manually operated devices so that much of the circuit switching required to restore service and to remove circuits for normal maintenance is done manually. Service crews are dispatched to accomplish this with the aim of minimizina service interruptions since remotely controlled breakers and switches are rarely used in distribution systems. The putaps experienced by retail utility customen are usually caused by weather related failures that occur in the distribution systems. In terms of customer-hours interrupted. approximately 10 to 85% of total interruptions occur in the distribution system. Sleet storms, tol'Dldos and other storms that cause widespread damage to the tree limbs overhanainl distribution circuits may cause distribution system outq requirina a week, or lon1er. to restore all of the interrupted customen. Automated distribution systems with remotely opented, automatic and controlled switchin1 opentiom may improve this situation in the future and reduce outaae durations experienced by retail customen. It will not happen overnight, however, u the distribution systems an very extensive and will be costly to upgrade. 1.7 INTERCONNECTIONS The U.S. and Canadian utilities are organized into nine regional reliability councils under the North American Electric Reliability Council (NERC). The nine regions are shown on the map on Fi1ure 1.10. As of the fall of 1987 the total capacities and peak loads of each are u shown on Table 1.a. Within each interconnection there an one or more control areu, each of which is deimed u that portion of the interconnection to which a common aeneration control scheme is applied. There are over 140 such areu in these systems. These control areas 111ist in the application of the automatic aeneration control systems r 1-47 331
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Power Teclaaoloal, lac. dilcuaed ill subsequent chapters. Their existence is essential to the effective control or power illterchallp between systems. They do not impede these illtercbaqe levels, but aid the operators ill keepina the flows within circuit ratings. North American Electric Rellablllty Council .... .. c:..11 ... ,...,Cw._,~ UIOOI' .... --..C....tlTIIAAO ,..,..AlaC.... IIAIII ,.., t= ,,._. NNO ........ ,_Cw c... NIIO ................... Counall ...... ,_,.. waca w eo.-. Counall A#IUATI MOO ...... Cw-eour.. F11un 1.10 Gtoanpblc Anu of tbe NI Realoaal Rellablllty Couacll1 of NERC r 1-41 -
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Power Tecba->loal, lac. Rqion ECAR TABLE 1.8 NEllC Reported CapacltlN and Peaks Al of Sammer 1986 Capacity (MW) Peak Load (MW) 95,201 69,606 ERCOT 43,386 39,335 MAAC MAIN MAPi--NPCCSERC SPP wscc 47,626 37,564 45,351 35,943 35,054 24,935 111,213 85,161** 132,168 105,570 65,102 47,123 142,885 91,768 Includes Canadian Areas Winter peak for 86/87 shown for NPCC Source: 1987 Reliability Assessment, NERC, Princeton, N.J., September 1987. [20] The benefits of interconnected operation are numerous and include: o better frequency control (i.e., tighter frequency tolerances), o access to reserves in the interconnected systems, 3 '.) ') \J'-,, 1-49 -
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Power Techaoloales, lac. o mechanisms for the exchanae of operatin1 data, and o the opportunity to develop interconnection-wide operating guides and standards. The disadvantaaes are few and those cited only seem to include the costs and time required to effect the agreements required. Interconnected systems' operations appear to be very successful with close frequency control. The adherence to a close frequency standard permits the automatic generation controls to function properly. r 1-50 -
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Power Technoloales, Inc. CUAWB P
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Power Techaoloales, lac. CHAPTER 2 ECONOMIC OPERATION OF GENERATION CONTROL AND INTERCONNECTIONS 2.1 INTRODUCTION The economic operation and control of the interconnected power systems represents yean of evolution and development. Modern electric power control centers make use of high memory capacity, high speed digital computers and communications systems to dispatch and control the interconnected power systems to: 1. Balance the generation and load to control the frequency. 2. Provide for reliable and secure operation of the bulk power systems. 3. Schedule the gen~ration resources for minimum operating cost [14]. The order of priority is as shown. Frequency control and generation control for system security are discussed in Chapter 3. They are more important in the overall operations than economy. That is not to downgrade the importance of economic operation, but the systems must be controlled to supply electric power at the correct frequency and voltage for customer use on a secure basis. This chapter considers system operations and the role of system interconnections. Economic dispatch, generation control and the organization and operation of the interconnected system are all interrelated. They are important areas to be considered when assessing the technical problems that are significant in any potential industry restructuring that may disrupt the current control systems and arrangements. The current arrangements work well, due in a large measure to the voluntary cooperative efforts of the system operators. This cooperation is necessary to achieve the level of reliable system operation that exists in the current industry structure [2.S]. r 2-1 -
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Power Techaoloales, lac. 2.2 SYSTEM OPERA TIO NS System operaton, the dispatchen, control center staff and operations planners must decide: 1. How much 1eneration to operate to meet the expected demands. 2. What specific units to run. 3. How these units should be scheduled so system production costs are minimiied while providio& for system security. The first concerns loads and expected load patterns. The second item refers to what is known u wt commitment" and is similar to the types of scheduling processes that take place in a manufacturing operation that hu excess capacity for the production level required. The third item is the economic dispatch of the aeneration, but it must include the system security considerations that take priority over purely economic decisions. Maintenance schedulio& of aeneratiog units affects system operations as well. Units must be removed from service periodically for inspection and for making scheduled repairs. Maintenance scheduling takes place in a lonaer time frame than unit commitment and economic dispatchioa and is frequently done on an annual basis. 2.2.1 Load Pattel'III The total system demand that must be balanced by an equal amount of 1eneration includes the expected system load, the requirement for supply of power outside of the system recoanizing any power imports (i.e., the net interchange scheduled) and the system transmission losses. System loads are always chanaing. Load patterns tend to repeat themselves and will vary not only with the time of day, but with the season, the area's economic conditions and the weather. Fiaure 2.1 shows a weekly load curve for a U.S. utility system. There is a certain amount of load, denoted as the base load that exists all week Iona. The intermediate and peak loads occur r 2-2 -
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Power Tecbnolo&les, Inc. because of the nature of the living, economic and industrial patterns of the area [26]. forecast short System operaton be required. This bas to be done may be brought required units is actually that will be up operated served, plus load well and must patterns to in put be advance OD line large decide how much capacity expected needs so that The total generation will of in the time. enough so that the peak load reserve (i.e., a "spinning capacity demand be to loss able of to handle provide an unexpected peak operating the loads, sudden loss of reserve") the generation, or a major transmission circuit. Figure 2.2 shows the type of pattern that results when the system operaton have satisfied the unit commitment requirement. 11 "' I I F11ure l.1 Wnkly Load Cune l-3 -
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Power Techaoloales, lac. 1aoo---~-------...----...----.~--1200 I 1000 MW I _.J 800 rorAL GENERATING CAPACITY ON7Ut ---+-r -~-, I w I aooa---~i----+---+----+----+---~ 400-----....... --....... --...,_--..,._--..,._--~ 2001---+---.... --...... --_.., __ ___.., __ ____ 0 0000~-04!!"'!"'!!0!!"!!0~~08~0!!'"!!0~"""!'1~20~0~-16~00~~2'"'!'0"!!"00~__,,2 ... 400 TIME OF DAY (HOUR) flpn 2.2 Typical Dally Load Patten and the Total Geaeratln1 Capacity Committed Iacludlaa the System Splnala1 R11ene Marsla The fint step involved in these operatina tasks is to forecast the load patterns. Fortunately, system load patterns tend to evolve slowly and operaton can rely on the repetitiveness of these patterns to predict load shapes and maanitudes. Statistical modellina methods have been developed which make use of past data and take into account the expected weather patterns to predict not only peak loads, but the expected chronoloaical shape of the load. .. 2-oi -
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Power Techaoloales, lac. 2.2.2 Ualt Commltmeat The nut step in the schedulina or the available resources is the establishment of a unit commitment plan for the generation resources available [27]. The ideal unit commitment schedule is one which meets all or the specified reserve requirements and operatina restrictions and supplies the energy required for the scheduling period at a mioim1un total operating cost. The practical solution to this problem involves consideration or all of the resources, hydroelectric aeneration, steam and combustion turbines, contracts and interchange arrangements with intercoDDeCted utilities and non-utility generation from coaeneraton and qualified facilities on the system. It is not an easy scheduling problem to solve in such a way that the optimum production cost schedule is ensured. There are many practical limitations on the operation of various resources that prevent them from beina scheduled freely and other operating constraints that must be observed. These include: 1. The requirement for the aradual heating up and cooling down of laqe units. 2. The requirements at minim11m load conditions where some units must be operated at their minimum loading limits (usually 25 to 35% of the unit rating). 3. The restrictions on the rapid changing of load levels for larger steam units (usually~ 3% or the unit rating per minute). 4. Availability of crews to start units. S. Restrictions imposed by local environmental regulations that may limit the total discharge of pollutants in an area. 6. The need to observe the constraints imposed by long term contracts r or fuel and/or electric energy interchanae. In addition the transmission network limitations may require that aenerating capacity in certain areas be online to provide sufficient resources in case of transmission circuit outages. (' 3JO 2-5 -
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Power Techaoloala, lac. Figure 2.3 illustrates the form of the total production cost characteristic of a steam turbine generator. These costs include the cost for fuel and incremental operation and maintenance charges that may be expressed as a charge per hour and/or per MWh. In addition the unit's operating costs will include co~ts for starting the unit. These include the cost of fuel for heating the unit, extra crew costs associated with starting water treatment systems and flue gas desulfurization systems. For a large unit that has been shut down for maintenance, startup charges may exceed $100,000 [28]. PAOOUCT10. COST ($/HR) 4000 3000 2000 1000 $287S/t-R S0MW 0 ~----i-----i----~----t-------!""---0 20 40 80 100 POWER OUTPUT (MW) Flaun 2.3 Steam Turbine Generator Production Cost Cune Unit commitment schedules computed to minimize total period production costs usually result in the commitment of the larger uniu to serve the base loads with the less efficient, more costly units being added as the load levels increase during 2-6 ('t 3.Jj
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Power Techaoloales, Ille. the day. The least efficient and most cosdy units to operate are usually simple cycle combustion turbines and they are run primarily for peaking duty. The procedure is reversed u the load falls durin1 the day. Unit commitment schedules are usually developed daily and will be redeveloped after major plant outa1es. System dispatches may chan1e unit commitment schedules durin1 the day to permit economic interchan1es to take place. 2.2.3 Ecoaomlc Dispatch Once the unit commitment pattern hu been set, units that are online are economically dispatched. This involves determinin1 the 1enerator operatin1 points at each time interval and load level such that the load is satisfied at a minimum total production cost rate. Economic dispatch schedules are recalculated frequently at periods of 5 to 10 minutes in most ener1y control systems. The easiest case to consider is the system composed of only steam or combustion turbines where the individual unit production cost characteristics are similar to the one shown on Fi1ure 2.3. The slope of the unit's dollar per hour versus MW output characteristic when plotted against the unit's output is known as the incremental cost characteristic. It aives the cost in dollan per MWh of the next MW of output of the unit. The optimum operatin1 points of the 1enerators are at that point where the incremental operatin1 costs of all units are equal. At that point the next MW needed will theoretically cost the same no matter which unit produces it. This theoretical approach must, of course, recoanize the practical limitations of maximum and minimum loading levels of the units, the maximum rate of chan1e permitted for the 1enerator loading levels, and the operatin1 constraints that may be caused by transmission system loading limits. It is this concept that gives rise to the well known system incremental cost that is widely used in the literature when schedulin1, wheelin1 costs, etc., are being discussed [14, 29). There are numerous complications in economic dispatch and scheduling that complicate the practical solution as well as the marginal cost 2-7 3.12
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Power Techaoloala, lac. concept. The rust bas already been discussed and is the result of the unit commitment procedure. (Actually the economic dispatch is a subset of this cost minimiation procedure.) The unit commitment schedule results in subdividiug the time intervals into periods during which the array of units on line is rlXed. The incremental operating cost rate during any one of these intervals will increase as the load level increases. When the array of units running changes, this function also changes. The result is that over the period of a day, incremental cost rates (i.e., the system lambda) may both rise and fall as the system load level increases. When any of the generaton or transmission circuits are constraining (e.g., units are at their operating limits or transmission circuits constrain the generation schedules), theoretically this incremental cost rate changes with location in the system. It is a common practice in the industry to refer to a single system incremental cost that is the incremental cost of the next MWh produced by unconstrained generating units. Another complication is one due to the effect of transmission losses. In a system with widespread generation resources and load centen the losses in the transmission system ma; influence the economic dispatch. In these systems the operaton must include what are known u incremental transmission loss coefficients in the scheduling algorithms. These coefficients are the incremental change in transmission system losses for an incremental chanae in power output from a generator. They are determined by analyzing the flow of power and V ARs in the network and recognizing that the shifting of a MW of aeneration from one location to another affects not only the aeneration production cost rates but may also affect the total demand to be met by changina the transmission losses in an incremental manner. ID systems with both hydroelectric units and steam plants, the dispatch procedures must recognize the effects of the water usage requirements on the schedule. If the hydro plants have sufficient water storage capacities, the hydro plants will be scheduled to minimize the total production costs of the system for some period (typically a week) by usina the hydro aeneration to reduce the costs of operating the steam plants. Typically this results in some portion of the hydro plant being (' f 2-8 -
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Power Ttchaoloal, lac. run to serve bue loads with the remainder bein1 used to reduce the peak loads to be served by the thermal 1eneration. The exact schedules will depend on the blfaace between the storqe capacities available, the nm-of-river component of the hydro plants, the water use requirements and the water rate venus power 1eneration characteristics of the hydroelectric plants. The coordination of the hydroelectric plants and the thermal plants may be a simple task for the operaton in a system with only a sin1le hydro plant or it may be very complex where there are several complex watenheds to be considered. The interaction of the hydro plant operation and thermal plant schedule will also affect the determination of the optimum unit commitment pattern. Economic operation it further complicated by contractual terms for both fuel supplils and the interchaa1e of electrical ener1y with interconnected electric utilities. These area are hard to cate1orize into typical patterns because the power system schedulina. procedures must recoanize the terms established by the various contracts involved. One type of fuel contract that has been fairly common is the type of supply contract that contains a tate-or-payprovision where the purchaser is obligated to purchase a minim1UD amount of fuel in a given period whether or not delivery is actually requested. These are similar to the take or pay supply contracts in the natural ps industry. la the purest sense and i1norin1 any complications caused by fuel storqe facilities, the obliption to pay for a set amount of fuel by the electric utility represents a classical sunk cost. The utility's total operating costs thus include a fixed component; the units bumii,1 this fuel will have a more-or-less fixed operatina cost for some interval. This contract turns the thermal unit into a hydro-like plant with characteristics similar to a hydro-electric plant with storage u far u economic dispatch is concerned. There is a fixed amount of primary energy resource (the fuel in this case, not the water) that should be scheduled in such a fuhion that the controllable total production costs are minimized during the interval. Contracts for interchange may be quite simple such as a fixed charge for capacity plus a char1e for energy at a 1iven rate, or they may be quite complex involving 2-9 -
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Power Techaoloales, Ille. chaqes based on avoided costs of the purchasing utility or energy charge rates which are ratcheted based on the rn11irn1UD power demand in a rnonth. The economic scheclulina of the system may in some cases, be determined by the terms and conditions or contracts. This is frequendy the cue in municipal utilities that have some local 1eneration and contrac11 for partial requirements from one or more interconnected utilities. In some situations that are particularly difficult to schedule, one or the contracts may have a ratcheted energy rate that is retroactively based on the monthly rn11irnu.m demand level. In a dispatch determination by the purchaser's operaton the purchase levels have to be balanced against the costs of local 1eneration recognizing the ratchet effect. Fuel supply systems may play an important role in determining the economic dispatch of the generaton in the system. It has been usual in the past to decouple the fuel supply schedulin1 from the hourly economic operating dispatch of the aeneraton by tacidy usumin1 that the fuel requirements determined by the economic dispatch could be satisfied by the fuel supply system. The fuel supply system and aeneration system should be treated u parts of one larger system th2 t should be scheduled simultaneously. 2.2.4 Eff ectl of the Traumluloa Sy1tea oa Ecoaomlc Dl1patchla1 One effect of the transmission system on economic dispatch procedures has already been noted (i.e., that of constrainin1 the output of a unit or plant). When incremental transmission losses are sipificant, they should be recognized in the dispatchin1 al1orithm. When this is done the operaton can determine the incremental cost of delivered power at various key interconnection points in the network. Some larger systems have interchange contracts that specify that these incremental costs including transmission losses will be used to determine prices. The transmission system plays another key role in the economic dispatch process. Generation schedules will be determined that are off economy (in the sense that they are not the optimal economic schedules) in order to avoid potential cascading outaae situations [14, 30 33). Power flows in ac networks are aenerally not controllable in the same sense that gu pipeline or water pipeline flows are. There .r 2-10 -
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Power Techaoloala, lac. are no simple valves that may be used to re1ulate the flows on particular circuits. What is controllable directly is the level of aeneration at a particular power station. Thlle aeneration levels will indirectly affect the flows on specific circuits and, therefore, provide the power system operaton with a degree of flow control. Most utility control centers have, or are implementin1 what are known as security constrained economic dispatch methods. In these techniques the system is operated in a defensive mode where credible contingencies are not allowed to cause substantial aeneration-load imbalallces, network element overloads or out-of ranae voltqe levels on the system. This is done by using a network model (i.e., a load flow) to examine the what might happen if ... cases that result from a given economic dispatch. and then moclifyina that dispatch so that the resultin1 schedule will not cause potential operatin1 problems in case of the credible contingencies. This procedure places a hiaher priority on system security than on operating economy. Security constrained schedules may be computed at intervals of 20, or 50 minutes, less frequently than the economic dispatch and more frequently than unit commitment schedules. The security constrained dispatch procedure is straightforward to implement. The exact determination of credible <. .. Atingencies is subjective. There appears to be aeneral qreement that all possible sinale continaency events should be considered so that failure of any sin1le 1enerating unit or transmission line will not initiate a ca,cadio1 sequence of outaaes. Many systems are operated more conservatively in that credible outa1es includ" combinations of two events such as the failure of a majo! circuit at the same tim.. as an outaae of a large generator (i.e., they consider double contingencies.) 2.2.5 Summary of System Operatln1 Coa1lderatloa1 We have taken a brief look at what is a complex technical area. The discussion is intended to provide a brief, non-technical overview. For simple arrays of aeneraton economic dispatch is straightforward once the unit commitment has been established. At any 1iven time the system is operated such that the incremental production cost rate is the same all over the system. r,, 2-11 r) f n v'i t)
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Power Tecbaolo1ln, lac. Once eneray storaae in any form (fuel or water) is introduced, the economic operatina problem becomes more complex and the focus of the schedulina problem becomes one of minimizi111 total production costs for some interval rather than merely f"mdina the proper level of system incremental production cost. Contracts for interchange may have a similar effect if they introduce requirements to schedule the system over a time span. The transmission network plays a significant role in the economic scheduling of power generation. Economic schedules may include the recognition of incremental transmission losses. Transmission systems play a key role in the determination of operating schedules that ensure system security when constrained economic dispatch techniques are used. 2.3 EFFECTS OF NON-UTILITY GENERATION ON SCHEDULING AND DISPATCH Non-utility generation includes: o smaller dispersed generation sources (e.g., wind farms, solar photovoltaic, etc.) connected on the distribution system, o self-generation connected in parallel with the utility, o PURPA defined Qualified Facilities (QFs), and o independent power producers (IPPs) supplying power to the utility. Small dispersed power generators are usually not dispatchable and are treated as load reductiom when system operate. "S are scheduling generation and dispatching. Self-@eneration is usually in a commercial facility or industrial plant. Normally it is operated in parallel with the utility system for standby supply in case of an emergency shut-down. It is not expected to supply power to the system, and is therefore not usually considered in the utility dispatch. If it is a large installation, the utility may have to increase the amount of spinning reserve scheduled on the utility system to guard against the sudden imposition of load in case of a sudden loss of the self-generator's in-house capacity. J ,17 2-12 -
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Power Tecbnoloales, Inc. QFs are paid for their power production at "avoided cost" rates. They affect the utility's economic dispatch and possibly the unit commitment if the capacity supplied is Jarae compared to the minimum load levels on the daily load cycle. In small quantities the utility dispatcher can treat the QF operations as load reductions. "A voided costs" are calculated in different fashions, depending upon state reRulations. In some localities, notably in Texas and California, the total capacity of industrial cogeneraton has approached the point where the utility light load dispatch is seriously affected. This happens because the most efficient utility steam plants have normal minimum load limits of about 40 to 50% of their maximum ratings. These units were not designed to be shut down overnight. Therefore, when the total non-dispatchable 1eneratin1 capacity becomes too large, the load remaining to be served by the utility aeneration at ni&bt time minimum load levels is too low to be supplied by the utility's normal array of steam units. The exact point at which this becomes a problem depends on the specific array of utility units and the level of remaining minimum load to be served. It is possible to shut down the more efficient units for longer periods to alleviate this problem, increasing the utility's operating costs. IPPs are relatively rare to date but will become more prevalent as utilities seek additional capacity. Existing IPPs are usually the result of the divestiture of a former utility power plant. They are operated as an adjunct of the utility with exact terms for control established by the agreement between the IPP and the utility. 2.4 POWER INTERCHANGE Power is frequently interchanged between interconnected systems for a variety of reasons. Scheduled interchanges are usually undertaken for reasons of operating economy or requirements that arise due to emergencies. Economy interchanges may be the result of centrally dispatched power pool operations or hour-by-hour negotiations between dispatch centen. Longer term arrangements are made between system opera ton or result from contracts between utilities for exchanges 2-13 -
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Power Technoloales, lac. or wheelina arranaements. Inadvertent interchanae takes place as a result of imperfect aeneration control system actions, failures or other unplanned events that requin time to correct. 2.4.1 Economy Iatercbu1 Economy interchanae arranaed between dispatch centers is of two types. Frequently used industry jaraon separates these into economy A or s transactions. "Economy A transactions involve the sale of eneray from units online, usually for an hour. "Economy e transactions involve a lonaer time period and may involve changes in 1eneratin1 unit .status, brin1in1 units online to sell their output or shut down capacity if an economic purchase can be neaotiated. Pricing of economy A interchange is frequently based on the difference in marginal production costs in the two systems involved (14). For a system that currently has a high incremental production cost rate, the purchase of economy A eneray may be more economic than to increase its own generation to serve an expected load increase. If the selling system is qreeable, the price for the energy may be based on the incremental and decremental cost rates of the two systems. A common pricing formula is one that prices the energy at one half of the sum of incremental and decremental cost rates. This results in the seller receiving all of his incremental production costs and one half of the purchaser's savings. There are other pricing schemes in use where, for example, sales might be offered at a level that includes a fixed profit marain for the seller. Arrangements for economy B transac:tions are a little more i1'volved since the longer term interchanae may involve the recomputation of one or both of the unit commitment patterns of the two utilities. An economy B transaction is usually based on the difference in total production cost that would result from the transaction. Pricina practices will include the cost of startina units as well as the added production costs involved in an economy B sale. In any situation where a dispatch center is involved in more than one economy transaction durina the same time period and prices are based on incremental costs, 2-14 r; .f 0 '-' J. -'
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Power Technoloales, lac. the order in which the transactions are performed may well affect the price. It is usual to find transaction priorities established on a chronological order basis. This situation where the price for a commodity (i.e., electrical energy) increases with the level of production in the short term, reflects the true operating cost changes in a generation system. It is different from the situation in a manufacturing facility where short term marginal costs may decline with increased production levels. When interchange transactions involve more than two utilities the number of possible arranaements increase. Interchanges between systems separated by one or more intervenina systems may be made "by displacement" or simultaneous buy-sen transactions. For example, suppose systems A, B and C were involved in a transaction where A wished to purchase from C, but system B was physically and electrically in the middle. A displacement type of transaction would have B purchasin1 from C and sellin1 to system A. Pricing for a displacement transfer would normally be done on the basis of the incremental cost differences in the systems. If a split savinp pricina method is used, the order of the transactions may be important and more importantly, the price level may be altered considerably if the incremental production cost rate of system B is out of kilter with the other systems. What started out as a lar1e savings for the ultimate purchaser may end up as a minor improvement in the purchaser's production costs. 2.4.2 WhHilDI The other 1eneral method used for multiple party economy interchange is for the intervening utilities to sell wheeling services. These are also qui:e common arrangements with various r:-.. ing schemes used to set wheeling rates. Generally the interconnected utilities have mutually agreed to use the notion of contract paths for transactions. In simple terms two utilities may engage in a direct interchan1e arrangement without paying wheeling charges if one or the other or both own (or have control oO transmission capacity between the two systems that is at least as great as the magnitude of the power to be transferred. This type of arrangement avoids wheeling related problems by ignoring the physical fact that the interchanged power will generally flow over a multiplicity of intervening 2-15 r. 3=r, .... ,.
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Power Tecbaoloal11, lac. circuits, iporina ownenhip considerations. These arranaements have generally worked up to the point where the interchanae flows beain to cause significant power losses in other systems or use transmission capacity needed by its owner. This leads naturally to the problem that has been come to be called the toop flow problem. Because many of the systems are so closely tied together electrically by the interconnections. power flows will flow over unintended transmission paths and may cause actual or potential operatina problems. For example. a large power intercbanae arranaed between an eastern and a midwestem utility will divide over the available transmission circuits with the result that a substantial portion of the flow would probably be over circuits in Caoada These loop flows may cause operatina difficulties for the intervening systems, affecting voltage levels and utilizina tnosminion capacity needed by other systems. Problems of this nature are solved by the close coordination of the utilities operating on a major interconnection. There is at present a movement towards the development and implementation of a system for the rapid exchange of operating data oo a real time basis (i.e.. for currendy existina conditions) between major control centen. This will usist the operaton in monitorina the system cooditions, in avoiding serious problems and iD developina qreements to avoid this sort of difficulty. Lona term supply contracts form another basis for the interchange of power and eneray. The terms and conditions vary, of coune, with the specific agreement. Systems will iDtercbanae eneray under a contract based on selling energy produced by the system's total capacity or on the basis of a specific unit's output. There are diversity iDtercbanae qreements callina for the bilateral exchanae of power and eneray durina cliff erent time periods. Contracts may be made between large utilities and smaller, perhaps municipal systems for the supply of a major portion of the purchaser's requirements. Contracts exist between non-utility generaton and local utilities for the sale of power and eneray. The 1978 PURPA legislation has resulted in many contract sales to utilities by these non-utility sources. There is no simple classification of pricina schemes for these long-term of interchange aareemeots. With the exception of the PURPA based agreementci, the 2-16 r1 r: voJ 1.
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Power Tecluaoloaln, lac. contncts an drawn between the parties and contain various types of rate schedules. Many, if not all, are subject to rqulation by the FERC. Inadvertent intercblnps are a natural consequence of the interconnected operation and operatiq pidelines and practices are designed to minimize their occurrence. The individual systems keep tnck of the inadvenent interchanges and return them in kind, MWh for MWh at similar levels of the load cycle [25]. Inadvenent interchanaes takina place durina periods of high cost production are replaced during similar periods. That is, inadvertent nows that take place during peak load periods are returned dwiD1 another peak period. This generally results in an equitable economic balance without the necessity of intenystem billing for these interchanges. 2.5 POWU POOLING AJUlANGEMENTS The arowth of interconnections fostered the development of various types of power poolina arranaements desiped to facilitate the growth of the utilities on a coordinated basis and to promote operatina economies. There are presently several typeS of arranaements. These include ( 1) centrally dispatched power pools, (2) pools that involve coordinated pl1nnin1 and establishment of operating guides, and (3) pools that have extended the aareements between the interconnected companies to establish and use power broker schemes to achieve production cost economies. Centrally dispatched power pools are characterized by the establishment of a cP-ntral control center that acts as the chief dispatching office of the pool and is responsible for coordinating the operations of the pool members' generation and transmission systems. They are composed of utilities with generation resources. There are three well established centrally dispatched pools in the U.S. that are made up of non-affiliated utilities, PJM in the Pennsylvania-New Jersey-Maryland area, the NEPOOL organization in the New England states and the New York Power Pool (NYPP) in the state of New York. There are centrally dispatched pools composed of the operating companies owned by a utility holding company. These include American Electric Power, Middle South, The Southern Company, Central and -2-17 r ',"':, I \,) ""' t..',,
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Power Techaoloala, lac. South West and others. In addition a new power pool, ENEREX. bu recently been established to coordinate the operations of some of the utilities in Iowa. The centrally dispatched pools schedule the aeneration system operation as though the member O"lanizations wen one system, resultina in a hiah level of power interchanae. The dqree of control exerted by the pool control center varies from pool to pool as does the exact structure of the dispatch and control system. In all cases the operatina savinp achieved by the pooled operation are allocated to the pool member systems. This is a necessary but difficult chore because of the complexity of the intersystem billina scheme required. In all cues the pool agreement specifies in one way or another that the individual operatin1 companies will not have increased production costs because of the pool operation. In implementina the allocation of the savinas due to pool operation, the rust step is to establish the mqnitude of the savinas. This is done by a nconstruction of the individual member's operatina costs u they might have been if the member utility operated its own resources to serve its own load obliaations [ 14 ). (ID NEPOOL this is known as the own load dispatch: a particularly suitable term.) The operatina savinp due to pooled operation are then calculated for an appropriate interval (say a week) u the cliff ennce between the sum of the individual utility's nconstructed production costs and the pool's actual production costs. These total savinp an then reduced to pay for the costs associated with the operation of the pool facilities and in some cases. to pay for the use of the hiah voltage transmission system owned by one or more of the pool members. The remainder of the savinp are then allocated to the pool members bued on formulae which aenerally split the net savinp equally between the net sellers and net purchasers durina the interval. Powe, pools establish requirements for installed 1eneratin1 capacity reserves and various classes of operatina reserve levels that must be maintained by the member systems. In all of the three eastern pools, PIM, NEPOOL and NYPP, any interchanae transactions outside of the pool are coordinated by the pool dispatch center. The current aeneral availability of both U.S. and Canadian energy in the r -2-18 -
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Power Techaolo1les, lac. eastern area means that members of these three pools are able to negotiate for outside energy purchases quite i requently. Centrally dispatched pools have not grown beyond those mentioned for various reasons. One is the practical difficulty in establishing the specific terms of the pool agreement between potential member utilities. In some instances utilities that have approached this type of arrangement have been dissuaded by the appearance that one group of participants would possibly obtain an unfair" advantage over another aroup. In other instances there have been disagreements over the use of transminion facilities. In still other cases movements towards a centrally dispatched pool have been thwarted by fear of regulatory constraints. This is a confusina point since in recent years several state commissions have encouraged the creation of new state wide pools. At the same time regulatory commissions in New EnaJand have been ~nminin1 the merits of NEPOOL membership for the utilities under their jurisdictions. The central dispatch centers do much more than arran1e for coordinated dispatch. They monitor and control the region's entire built power system. They provide a mechan.ism for coordinatin1 reserve requirements, planning functions and the collection and reporting of data as well as the enhancement of the system security. Pools of all types have promoted the practice of joint planning of facilities on a regional basis. The exchange of information concerning load forecasts and plans plus the establishment of re1ional reserve requirements and operating practices all contribute to the successful operation of the interconnected systems. 2.6 POWER BROURS One avenue that has been followed in some regions that has the potential for achieving most of the operating savings of a centrally dispatched pool is the creation of a power broker" system. Power brokers are regional systems set up to organize a market for the interchange of economy energy amongst the members of the broker organization. Physically the broker may consist of a computer program accessed by the dispatch offices of the member utilities. The staffing level required -l-19 -r 3 ~ ,'1 V
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Power Tecbaoloala, Ille. for a broker is much less than that for a centrally dispatched power pool once the m1mber systems have aareec:t upon the running rules since the only function of the broker is to arran1e an organized market for economy interchange transactions. A broker may opente by allowing the member systems to post hourly quotations for the sale of economy energy and bids to purchase economy energy. From here on the opention of the broker systems vary from one to another. The simplest scheme stops at this point. The member systems are free to make use of this bulletin board system for information and then undertake negotiations directly with another member to arnn1e a sale or purchase. This simple system saves the time of the dispatchen in searching the market and gives them access to the current availability of eneray and price levels. The next step in complexity and effectiveness is to have the broker, a computer proaram. match up the buyen and sellen each period and issue a notification directly to the parties involved. In one system these parties are free to undertake the tramletion or not with their only obligation that of reportin1 back to the broker data about the tramaction and operatin1 cost savinp. In another implementation the matched buyen and sellen are under obligation to undertake the transaction and would be oblipted to report the exceptions. The exact pricin1 and matchin& schemes to be used have been discussed, analyzed and the subject of experiments sponsored in part by the FERC. The original broker scheme installed in Florida based the pricing scheme on matchin1 the bids and quotes on the basis of the widest difference between the incremental production costs of the sellen and the decremental cost of the purchasen. Alternative pricing schemes include the adoption of a sin1Ie hourly c1earin1 price to simulate the action of commodity and stock exchange systems as well as the centrally dispatched power pool. Theoretically, the power broker schemes are an imperfect substitute for a centrally dispatched power pool since the power broker operatin1 agreements preclude the participants from acting both as a buyer and reseller durin1 the same period. This has the effect of restricting the transactions allowed. In some implementations 2-20 r r '~ !":, ~ u,.,
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Power Techaoloaln, lac. participation is completely voluntary. The occasional requirement that buyers and sellers under a broker be directly interconnected or have established a contract path also acts u a constraint on the allowable transactions. In contrast, the centrally dispatched power pools interconnections are rree flowing, and there are many interchanges that take place between remote utilities with intervening systems receiving no direct payment for wheeling. On the positive side power broken do off er the opportunity to achieve an overall reduction in production costs without the necessity for establishing a power pool qreement and without the expense of a pool control center. By incorporating some restrictions (e.g., members can not both be buyers and sellers at the same time, purchasers under Iona term contracts with another broker member can not resell the power on a short term basis, etc.) the broker agreement can be established to the satisfaction of all of the potential participants, including both the larger utilities as well u the smaller municipal systems with partial requirement contracts with the Iarae utilities. In viewin1 these market places it is helpful to remember that this industry has a rqulated monopoly structure despite the recent entrance of non-utility generators. The creation of centrally dispatched power pools and power broker schemes have Iaraely (if not all) been the result of utility engineers attemptin1 to produce a product at a lower, total production cost. l. 7 INTER-UTILITY TECHNICAL RELATIONS NERC The NERC organization serves a number of important functions in the electric utility industry. Through their two main committees, Engineering and Operating, they foster the secure and reliable planning and operation of the interconnected electtic power systems. NERC collects and publishes information about the existing and planned bulk power facilities and through the Operating Committee establishes and publishes operating guides for the system operation. The NERC Operating Manual issued by the NERC Operating Committee is a very useful source of data concerning operating guides and practices of the interconnected systems 125]. -l-21 'i r: v '--'
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Power Tecbaoloaln, lac. The most recently available summary of the plans and existing utility facilities is reported in Electricity Supply and Demand For 1987-1996 issued in November of 1987 [17]. This report summarizes the data reported to NERC for the North American systems and coven demand forecasts, supply forecasts and the planned additions to the transmission system. Fi1uns 2.4 and 2.5 are taken from this report. Figure 2.4 shows the demand and supply situation u it existed at the time of the 1987 peak demand in each NERC region u well u the expected situation in 1996 at the time of the expected peak loads. NERC-U.S.(SUMMER) 11201--------------F-t--H~H I ___ MNIGIN I I Flaure 2.4 Eadmated Maralu at the Time of Realonal Peak Demand Figure 2.5 shows the forecasts of the expected transmission additions of circuits 230 kV and above u reported to NERC in 1984 through 1987. According to data accompanying this figure, there were approximately 143,000 circuit-miles of r. -2-22 -
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Power Technoloales, Inc. transmission in the U.S. at voltage levels of 230 kV and above at the end of 1986. The 1987 forecasts for the 1987-1996 period project an increase of approximately 6% in transmission facilities. Note, however, that the forecasts of circuit additions have declined in each of the past 4 yean u load growth rate forecasts and rates of construction of new 1eneratin1 capacity have remained low. It appears from these data that the industry may have to live with the existing stock of transmission facilities in the next 10 yean. NERC-U.S. NEAC-CANADA -UIZ act.~ 1.114 act.~ Flaure 2.5 -Planned Transmission Additions r -2-23 r,,.. ... ( I \..,,,_,
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Power Technoloales, Inc. CHAPTER In
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Power Teclaaoloal, lac. CHAPTER 3 GENlllA TION CONl'llOL FOR FUQUENCY, VOLTAGE AND SYSTEM SICUJUTY 3.1 INTRODUCTION The aneration level ill ID IC power system must be balanced with the load demand in order to bold Crequeacy colll1allt. At uy time there are a Iarae number of paeracon operatbq ill panUel on the power systems so that the 1enerator 10Wlliq 1ysta11 must be deliped to allow the IIDill to sba., loads in a stable mDDM II well II bold COlll1Ult (requency. Voltapl on the system are controlled by vario111 devices which supply or absorb V Alla. Geaeraton are ID importaDt tool for voltqt control since the level of VAR 11neratioa may be controlled by varyiq the 1euracor excitation level (i.e., the lneralDr C-181d CUITOllt.) Ill m ec power synam tnnaniaion liDe nows may be controlled by: o ldjllltill1 pbale-wf'tina cnmrormen, 0 nritcbiaa die trMl'DWioD aetwork, 111d Under normal c~ die ram ii med far more frequeady than the rest. In a few ayslllllll plml ahiftiq tramformen may be used to control nows over specific circaita. ID emeranciel lolda may be shtcl Uld portions or the system nritcbld to reduce liDe flows. Thia chapter will dilcua the UM of aentration power control to pre11rve 1ys11111 security. lbt security dispatch (or security collltniDld dispatch) or 11neration bu 1ii4ificut comequences in the transmission capacity aYlilable. 3-1 3GO
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Power Ttclaaolopa, lac. 3.l PUQUINCY CONTllOL It ii tbe function of the speed aovffllOn oa the 1eneratin1 units to maintain the beWace between the Woad 111d aeneration levels oa the interconnected systems (14, 34 36). IC then were mon 1eneration than load. tbe aeaeraton woud accelerate, tbe Cnquency would tend to rile, 111d additional kinetic eneray would be stored in tbe rotatina men-or tbe machines. The oppositl ii true when the load is greater than tbe aeneraticm; the 1eneraton slow down, tbe Crequeacy drops ud kinetic eneray ia witbdnwn rrom tbe rotatiq machiDel. Except durina emeraencies such as major oa11P, tbe aoverniaa IYlteml keep tbe 1wration-lold belance very well. Small time erron do ICCWllulale due to tbeN freqlllDC)' deviations, but these are corncted periodically by system operaton wbo act iD concert on I rqular basis to correct tbe accumulated time error to zero. Three racton enter iDto tbe actiom wben tbe aeuration is less then the demand. One ia tbe tramieat errect that taka pllce initially -stored eaeray is removed Crom die rotatina menee of tbe aneraton. Tlul nnlll ill I decrease ill system Cnqaacy. Secondly. die total system lold bu a Cnquncy response that causes tbe load to drop tbe rnqaency dl'Ol)I ("load dampma or "load-frequency dampiq. ) Next, tbe speed 1ovll'llill1 systems will incnue the inputs to the prime moven or tbe aeneratiaa UD.itl, illc:nuill1 tbe electrical 1eneration and brillaiDI tbe load ad aeneration into bllaDce once apin, but at I reduced frequeDC:J. The oppoeitl sequence taka place wben 1eneration is areater than the Wold. Frequency iocr111e1, the I.old incnues, and the aovemon reduce the aeaention. Fipre 3.1 shows tbe actions that take piece oa a 6000 MW, isolated system when a 300 MW unit ia suddenly Jolt wbea the system load ia 5000 MW [26). The aovemor cbancterilticl bave I speed droop (i.e., tbe speed declill u the 101dina increases.) Tbe speed droop cbancteriltic:a required to permit stable parallel operation of the pneraton would have caUMd the frequency to decline to 59.15 Hz ia this example. (Thi compoeite speed droop ii mumed to be 5%, meuiaa that the frequency would drop by st. a the load 1011 Crom zero to the full capacity onlille.) In a typical syatna. the lold wW cbulae about ICM. for nch 1% chanae in frequency as motors 3-2 ('t 331
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ud otber frequency dependent lolda decreue. Twna both or these facton into acco1111t, die system frequency will bad (or a new operatina point when the load ud paeration ue be1nced at 4911 MW at a frequency of ,9.16 Hz. The automr.tic paeration control SystmD will tbell challae the set points of the 1overnon to bring tbe (nqaeacy beck to 60.00 Hz. FREQUENCY (Hz) 61 60 EQUILIBRIUM POINT (4988 MW ~LOAD CHARACTERISTIC (J l59. 86 Hz I "-I 4700 L~ 9.SS Hz I I I 4900 SIOO SYSTEM OUTPUT (MW) GOVERNOR CHARACTERISTIC I 5300 I ssoo flpn 3.1 Goftnor ud Load Claaracterladc for a 300 MW C...ndoa Dtftcleacy The overall effect on system frequency of' these actions (which an takina place all tbe time tbe system Jold chin .. rrom minute to minute) ii that the frequency deviatll coatilluouly Crom euctly 60 Hz. 0D the laqe Eutern Interconnection the budwidtbl oburved ue about 0.01 to 0.02 Hz on a moment to moment basis with superimpoNd drifts or lonpr duration that are about + or 0.0 I Hz. r 3G2 3-3 -
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Power Tecbaoloal, lac. 3.l.1 Alltoaadc Geaendoa Coatrol (AGC) Without Curtber moduJCatioa to tbe 1enention controls, when an interconnected system experienced a momentary pneratioa sbortqe due to the loa or a unit or a load iDcrale, all or the 1eaeraton Wlder 1overaor control on an interconnected system would attempt to restore tbe Crequncy to normal. (Some units are not on aovernor coatro'9 but are set to produce a CJ.xed power output to minimize the wear sb-oa laraer units ud to minimi,,e power level ntes of chanae on nuclear Wlill.) Th.ii would ca111e a lot of unaecesa.ey control action and would cause the iatmchalapl between system1 to deviate Crom the values that are scheduled u the diffenat 1111111 ia difCerent 1yste1111 compete to restore the load-1enention balance. Modern automatic pneration control (AGC) systems use a tie line bias 1enention control system where ID area control error (ACE) is computed and used u the error sipal to reset the aovernon set points. The ACE is the sum of the deviation of tbe ICtual ud scheduled net iaterchanae and a term proportional to the deviation of freqaeacy Crom 60 Hz. One or the objectives of this type of AGC system is to haw the uitl within a control area respond to normal, internal cbna-ia requirements ror 1eaeration and not to cbanaes in demand in the exterllll iatercomaected .,.... The AGC requirements for interconnected system operation may be illustrated by a simple eumple of three systems operatin1 initially with no scheduled net iatercban11 [26]. Fi1un 3.2 (a) shows the initial conditions where load and 1enention are balanced iD each area. Next. usume that system C loses a 300 MW WliL The result is shown ia Fi1ure 3.2 (b ). The Crequency be1ins to drop since the total 1enention is 300 MW less than the initial, total load of 4500 MW. Governor action ia all three area will increase the 1eneration in all three areas 1111111W11 that each system his sufCJcient capacity online Wlder re1ulatin1 control. Fi1ure 3.2 (b) illustrates the errec11 or the load frequency response and typical 1overnin1 action after the loss or the aenerator in system C and before any AGC action his taken place to restore the frequency to exacdy 60.0 Hz. The systems are in equilibrium at some Crequency below 60 Hz and the deficiency in system C is bein1 made up by power tn111fen Crom system A to B and from system B to C. At -3-4' -
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Power Tecbaoloal, lac. thia point the openton ill system C could iDcreue the available aeneration to pick up their own load apiD. it then ii surracieat operatina reserve. But in the mean time then ii III umcbeduled now on the interconnections. Without some modif'".acation to the 1ovenaiaa systems, all three systems would stan to reston the frequency to 60 Hz. Modem AGC systems ue desiped to correct this situation automatically and ue deliped to determine the aeneration chaaaes necessary to maintain scheduled net intercbaaae and scheduled frequency. lo I INITIAL C0NOIT10NI -NO INT!IICHANGI (II I LOU 01' JOO MW UNIT IN SYSTEM C Plpn 3.2 latercoaaected System Operado To do so the AGC system must receive sufficient system data to be able to detect both the actual frequency and the actual net interchan1e that is occurrina. Frequency is euy to meuure. The .net intercbanae information must be obtained by meaurill1 the power nows at all of the interconnection points of the systems and trammittina these data to the AGC systems in the control centen. The AGC system then calculates what is known u the area control error, or ACE. ,. 3-5 -
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Power Tecllaoloala, lac. ACE ii the sum of two components. the deviation of the actual interchanae in MW from the scheduled value and a second term, also in MWs. that represena the deviation of the actual frequency from 60.0 Hz. ID mathematical terms: ACE where (ANI NlS) (10B) x (f -60) ANI ICtUal net intercbanae, MW N1S net intercban1e 1eheduled, MW f 1CtUa1 frequency, Hz 8 frequency bia term, MW/0.1 Hz (B ii aepdve. If 8 -100 MW /0 1 Hz, the system m111t raise pneration 100 MW for evwy 0.1 Hz that tbe frequency drops.) To see bow dUI works out let 111 colllider the three system examples on Fiaure 2.6. To do 10, veral numerical 11111mptiom DNd to be made. ID each area usume that tbe load frequacy rNPOW ii such that 141 of the load ii lost for each I% drop in fncruncy IDd that the aovernor replation (i.e., speed droop) is 541. With these 11111111PtioD1 the frequency will decline by about 0.20 Hz after the 300 MW unit is lalt in system C. Tbe intercollDICtin1 tie nows shown on Fiaure 3.2 (b) result. The net intercban1 1ebeduled were all zero. Oae more set of numerical aaumptiom are needed. the values of the frequency bias terms in the AOC systems in each utility control area. Ideally these should be set at a value equal to the swn of the effects of the load-frequency dampin1 plus the replation. Take system A u an example. The 141 load chan1e for each I% frequency cban1e, the load dampin1 response, is 10 MW /0.6 Hz or 16.67 MW /Hz. The 541 1overnor reaulation is 1000 MW /3 Hz or 333.33 MW /Hz. Their total is then 350.0 MW /Hz or 35 MW /0.1 Hz. Similar ideal bias term~ are assumed in the other two area. Based on these 11SWDptiom we may illustrate rhe ACE computation u follows. The frequency cban1e prior to the AOC action is -0.20 Hz. Tie nows are taken u positive when flowin1 out of the system. 3-6 -
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Power Teclllosl, lac. AREA MW Net IDtercbaqe Frequnc:y Bill Term Area Control Actual Scbedaled IO(MW/0.l Hz)( -.2) Error (MW) A +70 -0 70 MW 10(-3')(-.2) -70 MW 0 B 212 -70 -0 142 10(-71)(-.2) -142 0 I I C -212 -0 212 10(-44)(3) -II -300 MW These control sipala ill tbe three AOC systems cause all of the increase in pmntion to take place ill Area C, the area where the shortqe exists. If there is suf'f"lciellt operatill1 11111ne ill Area C, tbe 1eneration in that area can respond. If not. die operaaon may have to purchale the required amount until standby reserve capacity ii broqht OD lim. The UN of tbe ACE error aipal ill tbe AOC system provides a simple way for area ..-,.don control IYllnll to dilcrimiDate betnen 1eneratioa mwnatches in their own 1J1te111 oppoNd to 111d!DIU:bel ill tbe other interconwted systems. When tbe ACE ii neptive tbe area should ics own pnention; when it is positive it should decreae itl paentioD. I 0De additional step ii required, that of allocatiD1 the desired aenention chanae to the 1enenton under control. Three f acton enter into this: economics, reaulation and UlmlllCI. The economic component is a result of economic dispatch computations and ii a control sipal to each unit that is based on the desired economic participation of tbe unit iD the total load china called for. The reaulatilll component ii daiped to allocate more of the desired chan11 to those WLitl that can respolld belt wben aenention ldjuatmencs are required to meet expected cbua ill demud. The milt component is desiped so that those units that cu, will provide the needed aenention cball1es when a larae total chanae is required. (' 3-7 3S6
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Ponr Ttcll ........ lac. TblN AOC :,t81III work quite well ud do so laraely due to the small frequency dnialiom that occm [3']. Thia ii a 1tron1 reuoa to main~n frequency perf'ol"!Dlnce ltududa (e.a.. that could be disturbed by any potential industry l'9ltnlCtllriJI) Another factor that contributes to the success or the illtercollDICtioa operatiom ii tbe coopentioa or the utility system openton in self policiq IDd ill lltablilhina voluntary workina arranaements amonpt themselves C"J. Tbe 11tablilbN11t of qrNmeDtl concernilla the required opentin1 and standby reterve levela ii quite importuat in the reduction of inadvertent intercbanae ill die interconnected system. The introduction of non-utility 11nention into the sy1t1m1 ...,.Uy may inc,.,. naerve requirements if' the non-utility resources CUDOt be cllllif"'led u firm supplies. 3.2.2 Tl"''lllut ()peradaa Pbnoaeaa Wbea a ..-ratinl llllit does Cail lllddenly IDd bu to be taken off line, the other llllitl require time before their aovernon act to iDcnue the units' outputs. In the wtiml, the system will receive power over the tnmmiaion lines which intercolllllCt it with other power systems u all of the synchronously interconnected sylt8III slows down to achieve a belnce between load and 1enention. Tnmiently, the load-aeneration belnce ii achieved by power beina extracted from the collective kinetic aeqy stored in the rotatina maes in the aenenton plus the dec1 in load tbat take piece a the frequency drops. ID the steady state and IIIUllliq that the controls did not act to restore the frequency, there would be a stable belnce between the load and 1enention at some frequency less than 60 Hz became of the speed droop 1overnin1 cbencteristic and because power system loads drop off u the frequency is reduced. This -ioad dampina" effect makes a positive contribution to the ection of the aeaentioa control systems used. In practice, the sudden removal of a leqe 1eneration source from an interconnected system results ill a tnmient drop in the frequency that is eliminated within minutes as the AGC systema come into action and iDcreae the outputs of all of the units under control. Faults oa the trammiaion system.a or in a substation aenerally have the opposite effect to that caused by t~.. sudden 1011 of aeneration. Suppose a hiah voltaae 3-1 -
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Pow Ttcllaoloal, lac. circuit ii struck by liahtnin1 and ii short circuited to around. This short circuit permitl tbe currentl nowin1 on the line to travel directly to around without flowiD1 throup the load. The short circuit chlD1 the electrical characteristics of tbe network and tends to reduce tbe voltqe at the point where the loads are served. The overall errect ii I sudden reduction or the load that is beina served by the 1eneration system. ID this cue the system tends to speed up and would contiaue to do so without some further action. ID the cue of faults (i.e., short circuitl) tbe action that tlkea place ii quite rapid (e.a.. cycles to seconds) when compared with the 1overnor respome or the 1eneraton (i.e., minutes.) Usually a fault will be cleand within I few cyclel of ill initiation by the combined action of the protective relayina system Uld the interruption of the fa ult by the ope Dina of hip voltaae circuit brelken. This action iDcreues the load imposed on the .....-ation. caaain1 it to slow down. This ii a transient phenomena with no built-in puutN tbat the system will return to I condition of stable operation. If the sysaem .._ accelerated too mucb, syncbroum may be lost and the different aeneraton on the system will pull out or step. If there is sufficient dampina in the system, syncbroum will not be lolt IDd the system will resume normal operation. nil ii k:Down the "tnmient stability problem by power enaineen and is one wbicb Im Iona pJaaued systems with Iona lines and remotely located aeneration. Tbe systemS are deliped to survive these short circuits and transient stability problema by extminin1 tbe expected behavior of the system usina computer models and postu.latiD1 vuioaa eventl that can result in the type of system behavior just delcribed. The ability of the system to survive this type of fa ult is a function of tbe capacity and electrical panmeten of the transmission system. System operaton keep some tnnmilli'>n capacity in reserve usina continaency constrained schedulina 1D1111U11 ill order to pnvent widespread system outaaes. It is quite possible that a fault that resultl in the removal of a particular circuit or line section may result in the nblequent overJOldin1 or other circuitl the system loadina pattern adjusts au1t1m1tically. Overlolded circuitl are nmoved from service automatically by the ICtiom or protective devices to pnvent seven d1m11e to lines and transformen. Without proper desip and operation, the occurnnce of a sinale fault could result in c11c1ctin1 of outaa and I widespread system blackout. Several major blackoutl have resulted since 1965 from just this type of circumstance. The 3-t -( 3:a
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Power Tecuolosl, lac. comequeace ii tbat today, 11101t system operaton will operate the system in a def'aaive moc1e wben DO cnclibll failure tvnt will ca1111 a cucadin1 sequence or 011tq11. Thia, probably mon tblll any other factor except the physical limicatiom or tbl circuit. limits tbl loc1in1 or trumnmio11 circuits. 3.3 VOLTAGI CONTROL Vo111.on tbe iDtercouected sys .. m mast be controlled to protect the equipment on die .,..._ ud kNp die voltqe mapitudll within control ranp limits. If the voltqe ftve1 pts too far oat o( raqe dM IO bavy fftnmitta-an flows, outqes, or circaita. die voltap control devicel in die distribution system may not be able to briq tbem to back to die proper vtiJintion levels. Tbe requirement to control the voltqe mapitadll !DNN that tbe supply or V Alls on the system must be nai,..nd properly ud that die 1J1181D operaton must keep voltqes within tolerable limits at die Ylrioa elKtaical b.... iD die symm. When voltaae a,adimm iD die .,..._ BIid aormal rua, it iDdica that VARI are beina tnlllllliUN from remo.. Jocltiom ud tbal the system's loael are probably too hip. Supplyina VARI clotl paaible IO tbe points when they are needed for voltqe control ii a common pnctice to awid trammittina VARI Uld reduce system laael. Voltqel are controlled i.Ddependendy (i.e., they are not controlled u a pu1 or AGC runctiom.) Voltq are automatically tabliabed at die aeneraton by controllina the aenerator r.eld excitation levell with voltqe replaton. (Mapetic r.elds are established in paeraton to 1enerate voltq ill tbe wiDdinp connected to the power system by current flowiD tbroup the field windinp. This is ref'ened to u field excitation.) Voltqe chlDa iD the system iClelf are primuily a result or the flow or V ARs tbroup various circuit elements, die aeneration and absorbin1 or V ARs in the system, aad the erfec11 or vuio111 voltqe nautatin1 and control equipment. Some or these cball1 occur naturally a a comequence or the VAR and power flows while others are a result of control actions that take place automatically or are initiated by system operaton. r -3-10 -
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VARI may bt npplied (or ablorbed) by Nversl meam within the control of the SJllam operaaon IDd by 11110matic vollqe control devices iD the system. Gnlraton cu supply or ablorb VARI well producin1 real power. Fiaun 3.3 ill81tra181 typical capability limitatiom of a 11111ntor. The curve shows the lllowabla operatiaa repme or a typical machine iD tenm of the power bein1 ....,.._ (die MWs) IDd the mllliom or VARI (MV AR) beiD1 1enented or absorbed by tbe wait. Power 011q,ut ii controlled by controllin1 the input to the prime mover IDd the VARI an controlled by the excitation system that controls the vol .... al the pnentor's tnminall. TM llmitatiom lbowa on dlil cuw an tbe l'IIUlt of NYenl physical comtraincs. Wha die llllit ii npplyin1 VARI to the system (the overexcitation reaion on the ripn) tbe ma1imqm outpllt ii limited by tbe temperature rile caused by tbe beatin1 eff lCtl or die cvreDtl flowiD1 ill the armature wiDdin1 or the r.eld windinas of die uit. Wba tbe ullit ii ablorbiD1 VARI (tbe UllderexcitatioD reaioD OD the cmw) die limitaeiom are due to barin1 errec11 of the currnt ill the armature ...tin1 IDd the belrin1 or die maceriall in the end repom of the 1eurator due to tbe electromapetic rieldl. Limits in tbil rep,n may allO be imposed by dynamic stability problems IIIOCiated with system operation. Synchronous condemen are rotatina machin that are also used to aenerate or ablorb VARI. Tbele are machiml, similar to aenenton except that they do not ...,.._ real power, only VARI. The level of VAR 1enention or absorption is automaticllly controlled by the excitation system and may be accomplished utomadcally in order to bold the voltqe mapitude at some point in the system. Tramf'ormen are med tbroupout the power system to chanae voltaae levels when 1oina from one subsystem to another. Th111 tnmf ormen may have automatic or 111111111lly controlled tap cbuauaa devices incorporated iD them SO that voltaaes are tnnlf'ormed with an incnmental voltqe mqnitude chanae superimposed on the nomiDal voltqe transformadon. For example a trauf ormer in a diltribution substation miaht be Ulld to reduce the trlDlmission voltaae of 138 kV down to a level or 34.5 kV for the primary system. 3-11
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10 OVU!XCITATION fl!IION UNDDEXCITATION ll!IION Plpn 3.3 C.aentor Capaltlllty Cne STATO" OVER HlATI NG IIEIION The trllllf'ormer mipt have adjustable tll>I that allow a variation of 5CM up or down iD tbe output voltqe. The tap cbaD1er that accomplish this may be under automatic or manual control depelldill1 on the pudcular tnmCormer desian. Some tralllf'onren incorporate automatic tap cbaD11n while othen do not. Usina this type or device, voltaa may be ldjuated at various 1catiou in the network. 3-12 ('I 371
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ClpacilDl'I. 11111111 rwton IDd llatic VAR 111PPU. may be illlcalled II various nadom ID ablorb ud/Ot ......-VARI ID affect vollqe control. n... devices _, bl coatrolled by 1Witcbin1 diem ln and oat or die network, or ill die cue or 1111 ltadc VAR IOIU'CN, it may bl done by automatic control devices. Tbe various CJPII ol vol .... COlltrol dlYica imllllld ill tnnmiaM>D, sublrlDlmillion, and dillriblldoll .,. .... s,.... pten...,. IDd opll'IIDn lltablilll a ruse or lllowable voltqe levels at vuioa polnll ia die .,, ... bodl for wmal IDd emerpacy coDditiom. Since YOIIIII coatrol iPolfll die flow ol VARI ia die DetWO,k. die sy118111's real power loal IN lfl'ICtlld. Tlllre IN IOIDI .... analytical 18CbaiQuel (e.1-, optimal load flow propw) ia w for ICbldaliq l1q11 IDd VARI dw minimize die real po .. ..,... ia die Dltwor'L J.4 acuul'Y DISPATCH Of GKNDATION TIii bllil fo, 1111 11emity comtrained d.ilpatch or power ..-,atioa ii the IC..,_,... ol ia a dlf'wiwe _,. IO dlat a "wont coatiapncy will aoc rma1t ia Oftllolded c:imait o, a voltap out ol rup on die system. 1111 wont CIII coedllpncy _, bl a linall oatlp eftllt ill tome IJIIIIIII while odllr'I -doable CODdnpDcill lO llll'CII for dll wont CIN, 1111 mdlodl 1111d ia CODtrol Cft181'1 IN bald OD load flow calculatioDI or Dltworlt flows IDd voltlpl (33, 37, 31}. 1111 dilpatcbffl (or die software system icselt) will nm a llrill or coadnpncy C1111 and compata die 1eaeruioa shirts required to pnvat c:ircllit oYlfloadl or oat or rup volllpl. The 1e111ndon shifts are dilplac11MDt1 from die optimal economic clilpltcll IDd may be baed on millimizin1 dla coatrol ICtioll l'IQllirld o, OD miDimizio1 die opentiq COIi penalty. Power .,_ Mli'"'" haw developed toplulticat8d madlemadcal models that mble diem 10 n.d wont call 1 rapidly and to dellr'llliDI what pnendon llairt1111 DNdl IO talr.t place. 1'111 Plll'POII ii to PNYIIII tbe OCClllftDCI or CUCldin1 outaa that are started wblD a aiDale condqency, (1.1., a major uammiuion line ouca1e) ca11111 the f' 3-13 372
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Pewer Teclaaolotl, lac. nbNq11111t overloadln1 or additional circui11. The use of security constrained paendoD ICbeduliq pncticel ii widelprad 111d appears to have reduced the iDcideDcl or major bllcko1111. Tblll "9DII ue so rare that reliable statistical data IN DOC available. AA lmportaat CODllqlllDCe ol th.ii opentia1 pnctice is hat transmission capability ii IIOflllllly beld ill r111rve ror tbe poaible occurrence of a major failurt in the sysllllll. ADOtber, ud imponut comequeace for aay discussion of transmission acc111 by DOD-11cillty ndtill, ii tll&C available transmission capability, itself. is a rUDCtioD of tbe NCllrity dispatcll pl"Kticel 111d allllyses used. The available tl"lnanieio-1 capacity ii a rllDCdoa noc only or the physical parameten of the cimaic ......... but mo tbe loedia1 ,,r tbe DltWOrk. 1'11111 dal cnmf' capability betWND illtercouecied lystllDI will depend OD the f'lowll bltwMD dlall .,.._ ud otblr illtercollD8C18d sys1em1 [39 40]. Within a liaale l'Jll8m die tnnaniMioR lilllill will depnd on tbe load level, the distribution of load ad pDIISdoll. ud tnllllen lakiDa place between the system an
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Power Tecllaoloal, lac. Tbe NER.C publication. -Yruder Capability: A Reference Document. contains dlflaidom ol dif'fernt typea of tnlllf'er capability. simulation techniques to .-dffllla tnllller capability, and pidellw for establisbin1 tramf'er capability objectiVII [3~). NERC def"'IDII tnmf'er capability u incremental or tota1. "IDcrematar' nf'en to capability above tbe normal blle power tramf'en and is a meave of die ability of tbe tnnanwioD network to cope with emeraency coDditiom with all normal power flows considered. -Total tnmfer capability is bMecl oa both normal blN power flows and incremental nows and represents the tocal amo1111t of power that CID be truderred between two area. It is more coaYeDilat to 1111 total tnmler capability tbroqbout tbeN discuaiou. Delillidom are mo aiva la this reCerence for tbe contiqenciel ued in calculatina trud capability. The IDOlt COIDIIIOII convatioa. "First Contin1ency lncrementai Tnmf Capability (FCn"C). ia die IIIIOUt of power (incremental above normal blN power tnmf'en) that cu bl trudernd over the tnnaniaion network in a reliable wnner, bllld oa die followiq coDditiom: Wida all fW'INP9wioa flCilitill in wvice, Ill facility Joedinp are widaia DOrmal ndap IDd Ill vol .... are witbiD normal limits. 2. T1le bulk power .,..._ ia capable of ablorbill1 the dynamic power lwiap and ....,Jnin1 stable followina a diaturbuce renltill1 in the loll ol ay ainale aemratiDI wait. tnnaniaioa circuit or b'llllf'ormer. 3. Altllr die dyauaic power swiDp foflowiaa a dilturbuce rmu&tin1 in die loll or ay liDale ..-,atina wait. tnnsmillioa circuit or tralformer, but before operatOr-directed system adjustments are made, all tl'lnsmwiQaa facility loldinp are within emeraency ratinp IDd all vol-are withia IIDlfllllCY limits. "Slcolld CoatinllDCY lncnmntal Tnmf'er Capability" is defiaed similarly but comklln 11C111Dtial IDd owrlappina oaof two facilida. For ,,.._ wida iacen:ollDICtiom iavolviaa more than two area, effects of limultaDIOIII tramlen mat be recopizad. The aimulcueous tramfer capability from lllnl 1n11 to aa .,. ii clifl'll'IDt from (1eurally I tbaa) the sum of the noa-lillaultlDIOIII tnmler capabilitill from tbe illdividual areu to tbd area. The 3-15 ,-.r 374
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Power Teclaaolopa, Ille. direction or tramfer ii also recopized u from ana X to area Y" venus area Y to uea X. or simultaneous imports or area x venus simultaneous exports of area x. ID multi-uea context. tramfer capability between any two areas depends on trlDlf'en between other pain or 11'111. Some systems show tramr er capability relatiombipa with bi-au polnom like that or Fiaure 3.4. For example, the Y to X trlDlf'er capability ii 6200 MW wbell X to Z tnmfer is 5200 MW. The Z to X tnmler capability ii 2600 MW wbn X to Y tramCer is 1300 MW. The simultaneous wziwam Mt import capability of X ii 4350 MW (not 6200 + 2600 MW), which OCCllrl wllell tben are no tnmlen between X 1111d Z. Two additional bi-axis potnc,m ae nqaind, sbowiq import1/expor11 or Y and Z, for a complete dilcription of die tbnl-uea system. ...... ...... -.. 5000 s ,c 4000 X EXPORTS X IMPORTS S 3000 flpn 3.4 Typlal Bl-Axil Trusler Capability Polyaoa (401 3-16 r, r 375
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Power Tecbaolopa, lac. The ualysis used to determine tramf er capability is based on ac load flow methods, or de load flow simulations if adequate. Computer propams are sometimes used to determine dependent inter-uea transfer capabilities suitable for representation by a polyaon. Two such Proanmt are TLIM (Transmission Limitations), used in the Pennsylvmia-New Jeney-Marylud lntercoDDeCtion (PJM) power pool, and SLANT (System Lhlear Analysis Technique), used in the Mid-America Interpool Network (MAIN) and Mid-Contin~nt Area Power Pool (MAPP) [40). ,.. _, 376 3-17 -
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Power Tecluaolopes, lac.
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Power Tecbaoloala, lac. CIIAPTIJl 4 LIMITATIONS TO TllANS~ION SYSTEMS 4.1 GENEJIAL COMMENTS T"lasmission systems serve at least four basic functions in the electric power system. 1. They transmit electric power from the aeaeration sources to the load and permit the intearated operation or utility systems. 2. They provide a means or shariDa 1eneration reserves amonpt intercomaected systems. 3. They allow tbe interclwl1e or power and eneray amongst iDtercollll8Cted systems on both short and Iona term basis. 4. They provide tnnsmU11io11 service to coaeneraton and other non lltility aenention sources to deliver eaeray to the system and its customen. The limitations to tbe JocHn1 or tnnsmiaiQn systems in the U.S. are due to only a few fundme11tal facton. These ere: o the thermal Cll)ICity of the tnnsmiafon circuits and associated 111bltatioll equipment. breakers, tnmf'ormen and station busses, o the voltap limits that mlllt be held in order to achieve safe system operation, and o tbe system operatin1 rellted problems that must be solved in order to imure economic, secure ud reliable system performance, iDc:ludin1 the establishment of acleqUlte transmission reserve requirements 111d the avoidulce or dynamic operatiaa problems that my ca111e system disruption. Finncial limitatiom ud environmental concerns may preclude or retard the .imtallations of new b'llllllliaion feciliti. ,. 4-1 378
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Power Techaoloal, lac. Transmission systems w~re desiped primarily to meet the requirements im:,osed by the rJrSt funcdon, the colllllCtion of aeneratina plants to load centen, tut the needs in the lat three area have pown steldily in the last 25 years. In that period the number of interchaqe and wlaeelin1 transactions bas arown two ,o four times a npidly a the sales to vldmte comumers. In more recent years the rapiJ cbUl.-in tbe relative prices or fuel, the adoption of environmental re1ulations that bave limited tbe placement or new pnentin1 plants, and the arowth of intercbup trlDIKdom 1111 peady accelerated. All or these chanaes have imposed new requirements oa the trannissic,11 system1 at the same time that rmancial and enviro111D1Dtal com have decelented tbe powth in tbe transminion system. Lold powth nllll have flllen, nuclear comtruction proanms have been delayed or dropped, rae1 prica have chlllaed dnmtically. and non-utility aeneration sources bave arilell a poaible major souice of supply. At the same time the comtruction of DIW major hip voltqe linel bu become more dif'ficult. Line comtrllCtion projects planned (or normal completion in 2 or 3 years have taken up to 10 J9U1 to complete in 11'111 where stron1 environmentally baled opposition has arilen (20). Lille confipntiom, that ii, voltqe levels ud number or circuits and their locatiom on the network, are establilhed by utility pl1nnin1 eqineen to ICCC.'mmodte the expected iJl.-.tlllrion of new aeneration, the expected load growth and the need (or system intep'ation and interconnection. Because power flows are only iDdinctly controllable on ac circuits, plaDnin1 enaineen must consider the poaible comequences or outaps or major system components. When one of a number of parallel circuits is opened, Y due to a short circuit, the power flows on the adjacent lines in the system will installdy be forced to carry increued flows as the power oripnally nowina on the removed line redistributes automatically to satisty tbe laws or physics. This meam that planning enaineen must plan on some level of redvndncy in the network and that system operaton must operate the system with tnlllmission capacity in reserve to allow for system failures. Without these reserve maraim, systems would more than likely suffer many more blackouts due to c11c1tlin1 Cailures initiated by sinale outaae events. 4-2 r 379
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Power Teclmoloal, lac. The a,owth of the interconnected networks bas complicated transmission system pl1nnia1 and opention since power nows do not respect ownenhip boundaries. System operaton must be aware or the operations in adjacent interconnected systemS at Ill times and coordinate their own operations with those or neiahborina Q1t81111 to the extent tbat they avoid mutual interference with each other. Electric power tran,miaiol\ systems are different from other types of transportation networks where nows caa be controlled and capaciti used to maximize the flow throqh the network. la power system the tTlasmissioD capacity that is available cball... with time uad with the puticu1ar opentiq reliability criteria used in operatiDa tbe system. This, of course, complicates the answer to the qution of wbat tnnsmi11ioD capacity is available for additional power nows. Lillel an deliped to bave Jaqe eaoqh conducton to carry the anticipated loads collliderilla tbe ef'fects or conductor size and confiauratioD OD the expected losses in die cucuit 111d tbe impednce offend to the now or power. "Impedance in an electric cucuit is like friction ill a pipe or bottlenecks OD a hipway that reduces tbe f'low. The concept is a little mon complicated beca1111 electrical circuit irnpednce is due to aeqy dmipation uad cbaq ill the ener,y stored in the electric and magnetic f"ields eccompanyill1 the flow of current in a conductor. Voltqe levels of tbe tnnmiaion system are selected on the buis of the expected c:apacity requirements, belnc:ui1 the economic considerations with dian reliability criteria. The rmult is that a pven voltqe level transmission liae may carry quite different loldinp in different systems and at different times in the same system as load uac1 aeneration patterns cbanae. Many, if not most, treamission systems are limited by more than one factor. As systems bave evolved over time they may bave arown out of one type of limitation into another. The 111tern intercomaected systems are one example where external conditions have served to alter the nature of the limitetion u the level of imported power from Caaadia sources bu arown. 4-3 r 330
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Power Techaoloal, lac. Transmission capability limitations affect system plaooioa and operations in various ways accordio1 to the function intended. For example, limited capability on interconnections between systems may: o reduce the ability to enaaae in economy interchanae and wheeling tl"IDIICtioDI, and o reduce the ability of' the systems to share installed generation reserves thas iocreasina reserve requirements for the same reliability level. T"lnmiaion limitations within a sinate system may restrict the system's ability to implement optimal economic aeneration schedules since aeneration schedules will have to be altered to prevent circuit overloads. The material in this report rel!\ted to transmission limits and remedies is based in larp meuure upon the Final Report OD EPRI Project SOOS -Yechnical Limitations To Tnnanmio11. System Opentioos", prepared by Power Technoloaies, hie. 111d submitted to EPRI in Aupst, 1917 [42). One or the aoaJs or the EPRI project wu to cite uas where increased research and development efforts are needed to relieve some of the limitations. That is only subsidiary to this current report and more emphasis is placed in this and the next chapten on currently aftilable means for nlievin1 some of these limitations. 4.2 DANSMJSmON LINE LIMITATIONS T"lnsmitsion circuit limitations are related to the physical characteristics or the network elements (i.e., the cumnt carryina capacities and design voltages of the lines, cables, transformen, breaken, etc.) and the parameten that describe the network performance (i.e., the system voltaae levels and values, currents, and V ARs flowin1, etc.) These characteristics and parameten are interrelated io that the values of the characteristics effectively act u constraints oo the network parameten. These characteristics and parameten include: o the reactances of the circuit elements, r ..... -
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Power Teclaaoloaln, lac. 4.2.1 o the thermal capacity of the circuit elements, o tbe voltqes cbarlcteristics of the netw<'rk elements and the voltqes that occur ia the network, 111d 0 tbe current carryilla capacity of circuit elements (which are mentially determined by their thermal capacities) and the currents actually nowill1 ill the network. lleactaace ID a transmission line tbe now of current is opposed by the impedance of the line. This ii mostly ~to the cbanain1 energy storqe in the magnetic fields surrolllldill1 the conductors and is called reactance (more properly the inductive reactaDce.) The mqnitude of the inductive reactance is a function of the aeometry of the conducton, their spacinp from each other, and above ground plane. The NICtaDCe is desipated by the symbol "X. Reactance is extremely important to power tramf'er tnansmission line limits. This reactance is a major factor ill the creation of two fundlmel\tal limits, voltage drop alona the conductor IDd tbe stability or the system. The voltage drop alona the line is almost directly proportional to the reactaDce. Stady state stability limits the maximum power that can be transmitted ovi,r any tw'lnsmiaion line to a level illvenely proportional to its reactance. This limit appears in the classical power-anaie relationship for ac power transfer over a single tl'IDlmiaion line [40). POWE ANGLE EQUATION Th.it report contains very few equations, but the power-anale relationship is so fvndJIMlltal to undentandin1 some of the limitations to electric power transmission that an exception was r elt to be warranted. 332 4-5 -
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Power Tecbaolop11, lac. ID an ac circuit the voltqes and currents vary with time, oscillatina at 60 Hz per second. A pictme would show these oscillations to be :iinusoidal. The sinusoidal OICillatio or tbe vario111 voltqes 111d currents are aenerally displaced from each other. That ii, tbe maximum value or the various voltqes and currents occur at dif'f'ereat times. These time difference1 may be converted to fractions or a cycle, or dearees for a comtlllt frequency and are nferred to as phase anale cliff ennces. When the phase aaate difference betwn two quantities is zero they an said to be in pbale or in time phase with each other. Voltqes in various parts of an ac circ11it an not nec1111rily in a time pbase with each other nor is the current tbroaah any element nmrily be in pbale with the voltqe. Enameen aacl scienti111 have Iona npresented these sinusoidally varyin1 volta1es and C111'1'8J111 by rotatiq vec10n, called pbuon in modern terminolo1y. The analysis or electric power circuit perfonnaace is pady simplified mathematically if these phllon are viewed from a nfennce frame that is rotatin1 at 60 Hz per secoDd IO the voltqe IDd carrent pbuon an flxed when the circuit is in the steady state. On each end of a tw'laaniaion line the voltqe phuor may be measured with respect to the zero voltqe or the poUDd. Each voltqe will be characterized by a map.itude (V1 and Vi) and anate with respect to the reference frame. On a tnnsmiaioa line the difference between the anaJes of the two terminal voltage pbaon is usully desipated by the Gnek letter de1ta (&) and is called the phase an~ or electrical anate. The t1JJ1c11me11tal equation that relates the power flow over a line as a function of the voltqe maanitudes at the two ends, the line's reactance and the phase angle between the voltaaes at the two ends is called the power angle equation. ,, 383 ,._, -
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Power Teclaaolopa, lac. where P V 1 x V 2 sin (6) p V1 V2 -X the power tnnsf er, the senclin1 end voltqe mqnitude, the receivin1 end voltqe mqnitude, X 6 -the total reactance between V 1 and V 2 and the power anpe between V 1 and V 2 The power ape equation shows that the power now over a line may be increased by: o UICl'IIIUl1 the voltqe mqnitudes, o decreuiq the line's 1'81C11111ce, ad o .iDc:reaiq the phlle anate difference. By iDcreuin1 the voltqes at the two ends of the line toaether, the power tnmmitted iDcrelles by the sqan of the voltqe. By increuin1 the current and keepill1 the l'IICtaDce coastant, the power anaie increases toward its theoretical maximum or 90 depeel. At the same time the voltqe drop alon1 the line increases so that in pnctice this llla)e cannot be nearly that tarae and is usually limited to 30 depees for pnctical operatin1 conditions. Voltaa may be increaed only to the point where they do not exceed the ratings of the equipment and line insulation strenath. This is usually about 5 to 6% over the line's ratin1. Beyond tbat point the line and equipment may have to be chlD1ed to allow the voltqe to increase further. Um reactlllel may be cbanaed by reconductorin1 the circuit. A line with two or mon conducton per pbue, a "bUDdled conductor", bas less reactance per mile than one with a sinale conductor per phase [18). Series capaciton may be inserted into the line and will cancel out some of the inductive reactance of the line. (Reactance comes in two types, inductive due to eneray storage in magnetic fields and capacitive caused by eneqy storaae i.n electric fields. Capacitive reactance is 4-7 334
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Power TecllaoloSI, lac. due to cbln1in1 eneray stonae in electric fields between two conducton or between a conductor and poand It also may act u an in\ped1nce to the flow or current in an IC circuit. Capacitive reactuce and inductive reactance have oppoate sips in circuit equatic,111.) The power aqle equation also sbows that the pbue anate between the voltaaes will 1Dc:r .... u the power now mcreues. but only up to a theoretical m1xim111D or 90 depeel. Beyond that anaJe the sine of the anate decreues,. decreuina the power now. The anplu difTenace .ii calllld by th;e voltap drop Ilona the line in the direction of tbe power flow. Thia in turn .ii directly proportional to the reactance of die line 10 tbat reduciq tbe line reactm:e reduces the pbue anate for a aiven power now. ADotber fmwimntal phyaical limitation to the loldin1 or ID overhead transmission line or otber circuit element ia the tbermal limitation [43]. The nil power losses (MW) in a transmmMHI liDI (or other circuit element) are dae to the resistaace or tbe line. Thia w power to be diaipatld in the form of beat u current flows throqh the line. Generally for modem hip voltqe overhead tnlllmiaion lines the ratio of reactuce to reustuce is in the order or 1 O to 1. Current nowina throuah liDII also ca11111 reactive power loael (V ARs) due to the line's inductive reactance. The flow of current ca11111 MW loael in a transmission line which will increase its temperature. If the temperature rise .is too areat. an overhead line will 111 and may take a permanent set or even sq so Car that it touches the around or a structure under the line. The allowable temperatun rise ii determined by the conductor materials and by local weather conditions (wind velocity, temperature etc.) Static thermal limits are unally calculated usumina standard conditions allow safety maqim. The nnlt is that lines only rarely Cail from excessive saa. Underaround cables and power tramrormen are much more frequently (if not always) limited by thermal considerations. The cables, beina buried under the earth, depend upon the cable coolina system (if any) and the heat dissipation fl r \ -1-1 -
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PonrTec.........,,lac. cblnclmilticl or tbl llln"OUDdiq soil [22, 24). ()peratiD1 these undeqround cabla at e:u111 tamperatara will abortn tblir aervice liva collliderably due to dam11e to tbl imulatiDa mediam. Mer-banic:al problems due to hatiD1 are usually not a limitation. Power trullf'ormen an dlliped to operate at a mwimum temperature rise to procect imulatiDa mediums also. Capabilities may be increased by desianina trullf'ormen with forced cooliq. 4.2.3 Voltap Vol.... limitatiom OD fw'lnaniaioD circuits an primarily mociated with safety stadudl ud the wet to preYellt liDe f'lllboven due to tramients caused by liptlliq strokll or switcbilla OD tbe system. Lim i.mulaton support overhead CODducton ud mlllt klep them ....,.._ mecbanic:ally Crom each other and from tbl tower lb aetun. Clelm an lltablilbed by tbe National Electric Safety Code CJllrlDce lllqsirements for tbe various voltap cllllel. Circuits desiped and combactlld ror om vol .... clal can occaionally be uPlf'lded to a biper volta1e clla to .iDcr1u1 die tnnanmioa capability, but anally only arter a careful study or all of tbe facton involved. Circaits tbat an to be iDcrelled iD volcqe usually reqllin a rebaildiq or t11e town. Low ~ltaae limitatiom renlt Crom operatiDa comideratiom. widwa fllllll that allow voltqe correctill1 apparatus tnlllformen) to maintaill e111tomer volcqa within tolerances. 4.2.4 Cunat Volcqes must be kept (e.1.. tap cban1in1 Upradq a fw'lnanmioD line by iDcrelaiq ill current carryin1 capacity may be a mon pnctical way to iDcrwe liDe capacity than increain1 tbe line volcqe. One metbod may be to iDcrwe tbe allowable temperature rile and bue the time temperatare limia OD more liberal criteria. Another technique ii to use dynamic liDe ratillp that nly on meaunmencs or line saa, temperature and local weather 4-9 -
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hwerT lac. ccmditiom to permit die Um to ope1'll8 cloler to its physical limits for short periodl dmiaa ... rpDCiee (44 ~J. Hi&blr Um curmatl ia ID overbd Um wW probably require that the line be Nib uq (i.1., ._ged) to prwrve die nqaired midspan clearances. Thia can be doM ia IOIIII ca111 (aad bu ben) while tbl llDI ia ltill iD service [47). ADodllr rlllible c.cluaique ror iDcnllilla die curmat carryiD1 capability is to recaadact!N' die U.. wida a larpr CODd1lctor or replace a sinale conductor per .,... .,...pant wida a baadll or two (or more) conducton [II, 41). This Pl'OC*lare ...Uy l'IQllirel die mecbnic:IJ reinf'orcement or the emtina tower 1t1 uc--. TIii Dau Power Compuy ia o or the major U.S. utilities that bas reporllld, chariq die Nlt dom put or die EPRI project referred to previously, tbac tbil ii a very ICODOlllical procedure, COltiq about 40CM or new line COMluciioa. Wida dal iDc"'N1Jn1 dill'icalty of obtliniq ..,, riabts-of-way, one alternative to mcr1 1 die ,.._,ioa capability of a corridor ii to completely rebuild the circllill litblr wida 11isda1 town or wida ..,, collltnletion. Newer line desip medlodl coapled wida Ndaced cllanDc:e reqalwats -Y permit the construction of a COllll*t U.. or ....., voltap or die Jn of a sinale circuit line to a compact doable circllit tower U... 0DI mwer propoal ii to make 1111 of 6 or 12 pbue comtruction rather than the coatioaal 3 pbw llDI CODltroctioa to iacw the line capability. This has bela uplond utnlively iD tblory and in demonstration projects, but has not u yet bin epplild to a major liDe recomtnlCtioa [51 53). Air~ propONd tacbniq111 ror iDcr1i:n1 the capacity of a tr1111million line is to coavert a bip voltap ac llDI to de. Thia bu been propc)led, but not tried u yet [54 56). It would tbeontically allow ID iDcreae iD capability with the same voltap levell with rapect to pound. It would eliminate the problems with ltlbWty and vol .... drop calllld by the lilll reactaDCe. 4-10 r, 337
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E1ildn1 anderpoand cable sy111ma may be uprated by opentin1 the lille closer to itl dmml1 capacity or iDclwiq tbe coolin1 available by treatiq the soil ma10111vlin1 die cable wida matmia1 wllich trlllllllitl beat efiiciendy. 1Dcreuin1 dal coolin1 or die coad1ICtOrl may n.,....t cable ratiDp 111in1 forced cooliD1 in pa of 1111-cooliila by iDlcalliDa c:00Un1 oil circulatin1 pumpa for example [57-59). 4.3 LIMITATIONS IN SUBSTATION EQUIPMENT SabltadoD IQ1lipmlaat limitations are due to current (i.e.. thermal) and voltqe limhl. 1'bl IQ1lipmlaat ia major mbltatiom includes bus work, tramrormen, lwitcbll, relayiq 111d proteetiYe tytltiil IDd power circuit breaken. These are ,,_iped for tbl YOI.... leYeJI IDd c:mmat CIITJUll requirements or the saation. Tblir Joedin1 limitltiom are due primarily to tbe tbermal capability or the IClllilmat. IDc-'-ina tlllll may be PQllibll by applyill1 forced cooliD1 techniques to tnDlform111 ad baNI. Clmait bnuer and nitcb tbermal limits are seldom lilllitma ill a l1lbltatioa [60 64). Wblll non-lltillty ......,_ ii added to a syltlm or vario111 meam are used to 1Dcr1a1 die circ:uit capuilidel or die ,..Dlfflillion network. tbe short circuit duties hPGlld oa die breakm"I mat be carefully checked to make certain that they are not aClldld. TIie breuen illltallld wen lec:1ed to interrupt fault currents (i.e., tMir lllort circuit duty) blled upon die upec1ld conflpration or utility imlalled IIDlddoa 111d circait impede,,.... The mblequent introduction or ldclitional ....-.. may bxr1111 the bnabr iaterraptin1 duty beyond the breaker capability, nq1liriq repllclmeilt or modific:ation of circuits to reduce the fault c:mrent. Gwnlly if a tnnemillio'l circuit ii aoin1 to be uprated by increuina its current C1rrJU11 capacity or 'VOi.... leYel, tbe equipment ill tbe aaoc:iated subltatiou must bl replaced to "*'1ftmodlltt tbe increaed cumtntl or voltqe levell. Tbe hi1her capacity. lliahlr YOI.... replacemeata may not fit the available space in the ltadoL Thil may bl a problem in 1tatiom wbere 11*1 ii limited. 4-11 ,.. ,.3 0 IJ8
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,., LIMITS ULATED TO SYSTEM PDFOllMANCE AND OPERATION A 11amber or lt'lnsmitlic>11 llmitatiom tbat an related to system operation and perf'onnance iDclude; (1) po.,. flow distributions, (2) voltqe-V AR related problems, (3) ayatem dynamjc probllllll (stability, plant response etc) and (4) system operating limitatiom that result (or ue impoaed) because or concerns with system operating security 111d nliability. The luplt poup or limitatiom to tbe effective trammilsion capacity is that related to reliable Qltem performance 111d operations. The electric power network ii a complex syst1m co11taillill1 111111y illtenctill1 electrical and mecballical ,._.,.,...__ Power flows on ID electrical Detwork must now ill patterns that satilf'y tbe pla,sical laWI aovemilla the behavior or electrical systems. This results ill more complex patllnll tbu tbOII found ill trllllportation networks where flows cu be directlcl. stond ad limited to make w of maximum traasrer capacities of tbe varioaa llab ill tbe system. For example, the nows or aoods over a hiahway network via track flel1a may be scheduled in such a fuhion tbat shippina costs are minimized wllile nkin1 maximum 111e or aftilable network IDcl truck fleets. If one rout8 becomll CO.....-., trllCb may be dilpatcbed over alternate routes or sllipmen11 delayed Ill route to allow tbe conpstion to subside. The same is true for airlinll, tnim, 111d III pipeliael wbere Pl may be stored ill reservoin or IY9II ia tbe pipeline itNlf. ID ID elec:bical system the product, electrical eneray, malt be delivered at mentially tbe same instant it is produced and the flow pauerm ill the ac network ldjast imtantaneolllly and automatically to satisfy the pllysical laws aovemiaa their behavior. Perhaps the future will see the development or a pnctical IDcl economic electrical eneqy storaae system usina superconductive elecbom11111tic storqe, but for the fores11111ble future, electrical eneray must be 1111d the momat it is produced. The tnmp0rtatio11 system for electric eaeray u the transmission network. Power flows ill ac systems will redirect themselv if the circuit confiauration chan1es, the load cun111 or the pattern or aeneration ii cbanaed. These facton make the 1Chedulia1 of tbe power system quite complex and further complicate the definition of available t.t'laamiaion capacity. ,-12
PAGE 400
Power Tecbaolosl, lac. The previous section dealt primarily with the physical characteristics of various circuit elements and the limits these inherent characteristics impose on the t.t'IDl!Diaion system. The consequences of violatin1 the various limitations are different and depend upon tbe particular violation. Exceedin1 thermal limitations Y cause severe physical dlm11" to tbe system components such as causin1 an overhead line to sq excessively and may result in equipment failures that isolate stations or ueu of the system or even cause blackouts. Exceedin1 voltaae limits cu cause equipment failures where voltaaes are too hiah or system collapse if the voltaps aet too low. A temponry excea of aeneration will cause the frequency to illcreae and. if prolonpcl, will result in the shutdown of the system due to the action of protective system that will shut down the steam turbine generators to protect them from tbe comequences of overspeed conditions. (Modem steam turbiDel 111d pneraton bave only a very limited ovenpeed capability.) A shorta1e of aemration will cause uaderfrequency operation that will result in the operation of automatic load beddina ~tective systems that attempt to repin the balance between aenention and laid. A prolonaecl generation shortqe may cause system operatOn to impose rolliq blackouts, where portions of the load are deliberately dropped for a time in order to keep the system operating. 4.4.1 Power Flow Dlatrldoa lffectl of Clmalt Outaaa The load division between the circuits on a transmission system instandy adjusts automatically to sadlfy the-laws of physics governina electrical networks. This results in the restriction of power flows on transmission systems because of the need to operate the system with adequate safety margins. Consider the parallel ac network shown on Fiaure 4.1 [42]. This simple system has two parallel 345 kV circuits tbat are capable of transmittin1 1000 MW each without xreec1ina thermal limits. middle of the circuitl. The linel are colllllCted in parallel at the ends and in the Suppc,11 the system operators wished to schedule 1200 MW over these two linel. Aaumina similar electrical characteristics in each line, the load would divide equally with 600 MW on each circuit. This is well within the Jo1c1in1 limitations of the circuits. 4-13 -
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Power Tecboloal, lac. 600 600 600 600 (A) laltlal LIM Loadla1 600 X FAULT I '7 600 1200 1200 MvV (B) Loadla1 After fultetl Sectloa ed l'lpn -1.1 Parallel 3-15 kV Craltl. LIM loadla1 lacruNI wilt faalted secdoa Is naoed. Next suppose tbat the second section of one or the circuits was subjected to a fault and wu removed automatically from service by the combined actions of the protective nlayina system and the circuit bnuen at ach end or the faulted line. The new power now distribution would be approximately u shown OD Figure 4.1 (B) with the circuit puallelina the nmoved line section Dow carrying 1200 MW, a lolding 204N, in excea of its rating. This loading would not be allowed for a prolonaed period, and the second circuit would be opened automatically by the protective system. The system operaton could take two conceivable counes to prevent damages to the network. One would be to attempt to redistribute the power flows, initiating aeneration or switchina chanaes rapidly enoup after the fa ult to prevent serious d1m11e. This is difficult to achieve in an ac network, however, since power flows ('l : -1-1-1 391
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Power Techaoloal, lac. camaot be directed like the now of water throuah a pipe. Conttols that are available are limited to shiftin1 1eneration, switching the circuits to attempt to redirect nows, Uld curtailiD1 lOldl to reduce power nows. A more reliable and secure operatin1 procedure is to limit the initial power nows so that after the occurrence of a fault, the nows are still within the limits of the circuit;s without requirin1 further operator action. bl this case the initial flow would have to be limited to 1000 MW so that after the fault and line section removal, the rem1iain1 section would be carryin1 no more than 1000 MW on a siqle circuit. nus mean, that the effective transmission capacity on each circuit is limited to SOO MW. The situation in ac:tul1 traNnJiaion networks is more complicated, of coune. The circuit confiamatiom are much more complex Uld the redistribution of power flows alter a faalt or line removal are more complicated. Nevertheless, the ideas in operadna a system securely are similar~ Ia the example above, if the circuits were ClffYUII 1200 MW 111d the line section wa removed, the protective systems on the remainin1 section would have removed the 18COlld circuit to prevent damaae to the circuit elementl. The result would have been the complete loss of the transmission path and redistribution of the 1200 MW on other parallel circuits quite probably resultia1 in additional circuit overloads Uld subsequent removal. This is a an illllltntion or a ca-cadin1 failure. This type of cascading failure has caused system blackouts Uld ii one or the major concerns of system operators. Tbe prevention or thele types or possible events seems simple in principle; just operata the system at lcwHn1 levels that will not result in severe overloads or low voltaps in cae of failures. However, it requires the establishment of operatin1 pideliw 111d practices that balanc,, the concerm over system security with the ecoaomic:I of system desip and operation. This technique ii incorporated in the security constraiaed dispatch methods discuaed in the previous chapter and used to prevent widespread blackouts. A key element in the use of this practice is the adoption of a set of pidelines to deime what possible contingencies are to be considered in developin1 a secure system schedule. Once this is done, analytical techniqua are available which allow system operators and plannina enaineen to 4-15 ,.. ,.. 392
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Power Techaoloal, he. deYelop defensive schedulina methods to minimize the possibilities of cascading failures. 4.4.2 Loop Flows Another consequence of tbe iDherent inability to direct ac power nows in a simple fllhion is tbe "loop flow" that oc:cun when power interchanges are scheduled on the illten:ollDICted systems. Ill a tipdy iatercouected system such u that found in the mtem and Wlltenl puts of the U.S. and Caaldian systems these loop nowa will tab place throqb a Jara number of iatefftDina 111d adjacent systems. Fartber complicationa are caued by die fact that a number of transactions usually an taldna place simultaneolllly. The effects or these simultaneous transactions are additiw in die flows over some circuits, increuiaa the power nows on some tr111f1Dillio11 circuits. Ill other circuits the nows due to two simultaneous interehln111 and COIIIIQU8Dt loop flows may be in opposite directions and actually reduce die total power flowiDa over a specif"JC set of circuits. P-1111111 4.2 Uld 4.3 contain a very simplif"lld eumple of loop nows in the Eastem Iatercouectioll usiq hypothetical eumples [65]. The six systems shown are those in Ontario (OH), New York (NYPP), PJM, the American Electric Power system (AEP) in die midwest, the systems ill lilinois and those in Michigan. Several intervening 111d adjacent systems are omitted that would actually be involved in the loop flow eumple below. For plll'l)OIII of illustration aaume that OH is to deliver 1000 MW to the NYPP systemt. Fipre 4.2 (B) shows the approximate paths that this interchange will follow. Only about 500 MW will now over the direct, contract path between the two parties iavolved. The other 500 MW will now largely tbrouah the path between OH and AEP then eat and north throuah the PJM systems to New York. Actually in a cae like this some power would now through northern Ohio to New York and some would now in the systems south and east of AEP in the Virginias and evea further south. ('I r 4-16 333
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Power Tecuoloala, lac. (A) Slaplln.l npnNatatloa of die latercoaaected Systems la die Nortben portloa of die Eaten Iatercoaaecdoa. 500 MW (B) Appropriate later Syatea Flows wh OH schedala a 1000 MW to the NYPP Systea Flpn "4.2 Aa matndoa of Loop Flow, la the laltera Iatercoaaectloa r ,4-17 394
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Power Ttcbaoloala, Ille. 450 MW 125 MW (A) Approxlllate later S11te non wbea AEP acbedala 1000 MW for dellTery to tbe Mlcbl-Syate .. 825 MW (B) Approxl11ate t non n1alda1 rrom the two 1lmalta11eo latercbaa1 achedala. Flpn 4.3 De non ror a schedaled laterchuae or 1000 MW from AEP to the Mlchl-S11tems. (B) ne combla .. ertec11 or the OH-NYPP ud AEP-Mlchlaaa Iatercbuae. 4-11 r nn,-~ .J '1 V V \.,
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Power Tecbaolosla, lac. Next colWder th" second transaction shown on Figure 4.3 (A), the delivery of 1000 MW from the AEP system to the systems in Michigan. In this case about 425 MW would now over the contract path and the remainder would be distributed approximately u shown. Note that about 125 MW ( 12.5%) nows east and north throuah PJM, the NYPP and OH. Apin the illustration is simplified in that some of the systems that might actually be involved have been omitted. 1 both or these tramactions are scheduled simultaneously, the net effect on the individual interclwl1e boundary circui11 between the various systems is shown on Fipre 4.3 (B). Note that in some cues the total nows are additive. For example the nows between _PJM and NYPP, between AEP and PJM and between OH and Mkbipa are all increased to a level of 625 MW. On the other hand, the flows on some paths are decnlled. In this example the contract path between AEP and the Micbipa systems is only carryin1 a now of 75 MW into the AEP system. With a number or intercbaqe tralllletions taking place simultaneously on an intercoaaected system, it becomes an increasingly dif'1Cult task for the system operators to schedule tramactiom in such a way that loop nows do not cause undue hardship on the intercomaected systems that are affected. These nows cannot be allowed to overload circuits nor to constrain the operation of the utilities that own the trammissinn circuits effected by loop nows. This requires that equitable anan1ement1 be in place and that system operaton must have data available concemin1 the scheclulel and conditions OD interconnected systems. The loop now phenomena contributes to the limitations of nows on transmission the difficulties in precisely defining the available, unused transmiaioD capacity. All or thele network related now pbnomeaa, the distribution of power nows, the utomatic redistribution that takes place when system conditions change, and the effects or loop flows resultiq from interchanae transactions are complex, take place rapidly. and require close coordination between interconnected systems. The need for this coordiation and information exchlll1e bu grown u the number of tralllletioDI beint scheduled his iDcreuecl. r ,-1, 326
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Power Teclaaoloal, lac. 4.4.3 Voltqe-V AJl Preble .. When power systems are desiped and operated such that V ARs must be ~tted alona a t,ammission line the VAR now will cause a voltage drop ale 111 the line. The network voltage prollle (i.e., the maanitudes of voltqes at key points in the network such u line, aenerator, and substation buses) must be restricted so that voltaae control devices (i.e., transformer tap chanaen, variable VAR supplies, etc.) are within their control ranaes. If they are not. the voltqes at customer loads may be outside of the ruse allowed by the standards. Voltaae-V AR now problems ma, cause operatina restrictions and circuit loadina limitatioas that arise out of system operatina security practices similar to those dilcuaed above [66, 67). One aeneric" example arises when a system is importina a substantial portion of the power to MrVe the load in its territory. Under normal conditiom tbe circuits ue well within their thermal capacity, and voltaaes are within tolerance. The imported power ii beina transmitted via a transmission link that may fail 111d shutoff the power now suddenly. If the importina system is interconnected with otber utilities, the lost power will be made up in a tarae portion by the inflow or power into the system that takes place automatically u the entire interconnected system attempts to maintain the proper balance between supply and demand. This unexpected heavy now into the area is accompanied by heavy VAR. nows. depnaina the voltage dramatically at the receivin1 system. Given the riaht combination of circuit elements and power nows, the voltaae may be depressed to the point when the entin receivina system collapses. That is, the voltaae declines are accompanied by additional VAR nows which, in turn, result in further voltage declines (61 -71). Power now distribution and voltqe-V AR problems are closely intenelated. For a aiven trammiaion line the mapitude of VAR support requind for the terminal voltaa ii dependent upon the power flow on the line. All example is shown in Fipn 4.4 which demonstrates the total reactive power in terms of millions of V ARs (MV AR) required to transmit a aiven power flow over a 345 kV line which is 100 miles Iona, in order to keep the voltaae mapitudes constant at each end at their nominal levels. r-397 4-20 -
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Power Teclulolopa, lac. Suppose that this represeats tho cbaracteristics of each circuit section on Figure 4.1 and om of the sectiom were to 10 from a situation where it was carryina 600 MW to om where it wu carryina 1200 MW. The total VAR requirement for the section at a power now level of 600 MW is about 80 MV AR. When the parallel section is removed Uld the Jo1ttin1 aoes to 1200 MVt', the VAR requirement increases to about 700 MV AR in order to hold the voltqe at its rated value. Some of these V ARs will be trammitted over the line and some mittt be supplied at the load end of tbe line. Trammittin1 the V ARs increues the currient flowina on the line, usina addidollll line capability. Desipina the network to survive this situation requires a subltalltial imtallation of VAR 1eneratia1 9Ciuipment at the receivin1 end. Failure to mpply the required V ARs will result in a Jowerina of the Joad end voltage. If it is too low, the system may collapse. 1000 750 500 REACTIVE POWER 250 MVAR 0 -250 0 200 400 800 800 1000 1200 1400 1600 LOADING, MW llpn .c., -V All lltqaln at Both ENI of a 100 Mlle Loa1 345 kV Chait. Sus llllpedaace Loadl LtTel (SD.) cornspoadl to zero MV AR. r 338 .c-21
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Power Teclaaoloal, lac. A shniJr situation may arise when hip voltaae traDsmission lines interconnect two systems. rJ1111'9 4.$ shows three iDtercoDDeCted systems. A and B are illtercomaected by two 100 mile Iona 345 kV liw. System B is interconnected to C by a de liDft tbat normally carries 1100 MW illto B. Simultaneously 3 is importing 900 MW f'rom A. System A npresen11 the rest of the interconnection and is very laqe ill comparison to system B. Under normal conditions the 900 MW flowing f'rom A into B nqujns pnctically zero VAR. supply since the 345 kV lines are operatilla near their 1111'11 ll"ped1nce loadina level 1100 MW/ 900MW 2, 345 kV NJ LINES n..,. 4.5 Tlane Jatercouectatl S,..._. 1bowla1 2000 MW Import to S,s1HI B. If die de clmdt II lolt die non oa eacla 345 lr.V 11 will lacnue to allloat 1000 MW. Aaume that the de circuits linkilla systems C and B an suddenly lost. The loadin1 of the 345 kV liD iDterconnectilla A ud B will increase to almost 1000 MW each u the power nows illto A to attempt to brill1 the load and aeneration into balance. The 345 kV circuits an within their thermal limits, but the total VAR requirements to support the voltapl have increued to about 1000 MVAR. If the VAR supply is inadequate, the voltqe iD system B at the 345 kV terminal could collapse, requirina load sheddin1 ud probably system separation f'rom the nst of' the interconnection. Possible cures, or operatina precautions that may be required, may include the restriction of the level of power imports so that the loss of' the source will not cause a major outa1e, the installation of additional emeraency VAR compensation, or r 399 4-22
PAGE 410
hwr Teclaul ..... lac. tbe rb:iction or normal power flowt oD the interconnectina tnnsm.iaion circuits SO tbat ID OCC111'1'8DCI of th.ii type or event will DOt result in I voltaae collapse. 'l1UI type or security comidentioD ii important in current system operatiou. In tbe wtem portion or tbe U.S. laqe blocb or power are beina supplied from a siDa)e Ondin system, Hydro-Quebec. ID the western interconnection. hi1h cepacity de links exist. which ue med to transmit blocks or power between the PlcuJC northwest 111d the southwest UIII. Both or these examp1-require that system operatOn aad plannen aive comideration to this type or situation in order to prevent widespread circuit illtemaptiou [20]. ........ Power systn11 allO may saf'fer from dymmic problems when power nows oscillate at low frequeac:ial [42). Tbe anenton on a syacbrono111ly intercolllltCted system ID l'Olat8 in tueb a way tbat tbe elec:trica1 aqlel between their roton (i.e., betweea die aeaerat8d voltqe pllllon) stay within reuonable bounds nlative to IICh other. Tbe power tnlllf'er over a aivn elemellt or circuit in a ac system dependa apoa this mpler dHTerence. If' .,. sort or disturbuce (e.a.. a line fault near a pneratia1 station) ocean, tbe upler differences will cbanae became power flowa ue altered 111d caw the power output required from tbe aeneraton to cbanp. The eJectrical power nquiremlllt from a aenerator may be suddenly reduced d1le to die fault IDd the mecbnicll power developed by tbe drivina turbine staJS comtut. ca111in1 the aemrator to eccelerate. illcreuina the uaular difference. When tbe faalt ii removed by openina the faulted circuit. the power flows will qaill be altered IDd tbe mplar diff'erence decreued u the unit slows dowa. Thia will raalt in low frequeacy OICilladom or tbe aenerator rotors and po.,. flowa ha the network. If' tb8II an not damped out naturally or by the ICdom or Ylrioaa control systlml, tbe System ii umtable IDd IIIUally requires switcbin1 opendo111 to sepvatl the sy1tem in order to reston normal conditiou. 'l1UI dynamic illltabillty ii like tbe phenomena that may occur OD a heavily travelled bipway. Al Iona u trarfic ii movua1 at a relatively coutant speed. the vehicles will space tbemselva 1ucb that no mterterence results. However, when a sudden 4-23 400
PAGE 411
ctwnae ocean (1.a.. a vehicle deceleral8I npidly because or a tire blowout or to POid IOIDI luddlD lab 111io11 illto the tnlflc patlerll), the spacill1 between vehicles ii DO IOll&er Slade. bllt CMftlM with time a IICh driver responds to the conditions a. ..... TIie Nlllltl cllPIDd on the iaitial spacinp IDd velocities, the speed or 111Pa or tbl driwn IDd a llalt or odllf collditiom. What would be a minor diltarblDce ill the tntrac flow pat1m1 oa a dry, SUIUIY day may be a major ICCidellt dariaa a raiay early "9IUIII pmiocl. IC tnCric volume ii heavy and the ...._, ftllicle spNd ii llip. the miDor diaturbuce may result in a chain of accidnll. TIie .... ii tne ill a po..., syltnl where a minor trllllient event will radt ia a flNtilla diltarblacl with ODI lald-pneratOr pattern and came a major illllabDitJ adlr clifTemat ,,-CODditiom. inlmf'erill1 with system operation is ia-tltll\ld by ,,,_ MSinNn llliDa compln computer propams that must :ep,11111 die ....... CDDtlOII ud load clmlc.,iltics well u the network. For ,,_ wida lolla, llip l'IICtUCI liDII dlil may be a major coacena because of dlil efftet or tbl U.. l"IICtallCI la Jiwida1 power trllllf"er. 0111 IIIChaiqPe to allnlatll die problem ii to reduce the Jo1cHn1 on Iona circuits. Otlllr illldlodl iacladl mini illllfflWtilaa swiecllill1 statiom to reduce tbe shock to tbe ,,_ ... liDI NCdoal mat be remowed IDd to me methods for reducill1 the efflCtiw 1iDI hnpedear-Rapid (Le., hip speed) breakers may be used to clear raa111 mon npidly dlaa normal bnaun [72). Modern control systems on ...-,a ud their priml IDOV9II may mo milt in solvin1 these problems by providlq npid ICtiom to damp oat the OICillatiom [73 -IOJ. Fut valvin1 may be illllalJecl oa tbl w hlrbim to ldjlllt tbe mecunical power input to the unit. Bnlldlla nlilton may be nritcllld in 11111' till pneratc,r to absorb the power C'II .... tbl llllit to ICClllnt8 [II). It Y be illtllll,Y to trip 1eneraton and redw the power iapat noidly to the ait (LI., rat nmblc:k.) Modern excication IJI-wida stabi1lwl CID lllilt ill CODtrolliDI tbeN dyDamic problllDI. SublyDoluoaoal NIN'lnc ii uother type or dynamic problem that occun in lfll I n; ..Uy IYI wida lonpr llw wbicb have rill capaciton installed to redw the overall impedence or till liDI (12 -17). ID some systems that have 4-M 401
PAGE 412
P8ww Teclaaolqlel, lac. ltlllD tmbiDe &aerator plaats at the ends or Iona hip voltqe circuits, low fl'ICIIIID'Y OICIJ11dom are IOllletimll excited tbat IN amplulfld by the resonant iataKtion of the l1Dnd IDll'U tnmf'en betwn the ellctrical system and the rotldnl @?XII of tbl 1181111 tarbim ....,.aon. Thele steam turbine units have ....,.,.. PNCbeic:IJ Cnquencill wbicb an lea tbaD the 60 Hz or the electrical .,-. Occionally, if die electrical network puameten IN or euctly the right mpitade, tbl mechanbJ ad tlecbbl IY'tllDI have resomt frequencies which 11'1 clale IDOUah IO undamped OICilladom may occur. If' these penilt, shafts on die .... tarbiDI mlitl may brat. Thin 11'1 odllf mehniew that may renJt ill this PlleDomena. but the one cited abo99 -tD be die -jor cau11. Time are venl metbodl UNcl to cure this probJe& TIie elecbicel ad/or mecbubl systema may be detuned by chanain1 ....,t diNNiOIII or modif'yiq tbl elecbical network. A Im expensive technique is tD -m... ill dll llec:bicel .,..._ to block tbe low frequency currents or to remoft thaD Crom dll IIMWOrk. The low CIIQiiftCY currents may also be detected 111d wd a lipal tD ,..,.. tbe ........,,.. s,... operatiDa IICllrity COlllideratiom ad policiel on tbe illtercoanected system effect lnNm!aio-. limitadom tD a peat extent. n.e are concerned with wiihla operadaa ...... IIICb dlat inslabillty, 1111C011trolled Sll)ll'ation or systems or CIICMiq out1111 will not nmlt Crom die occurrence or cncl1b~ contiaaency. TIii NEllC pidlliw refer tD liqle, IDOlt served contill1enciel u bein1 a reqairemeat widl multiple contiDpacill beiD1 an optional requinment to be met wlleDpnadcal[25]. 1'11111 pidlliMI nnlt is 111 beiDa operated iD a dereDlive mode with some ,,.._ opea-. 1lliaa IUIIII coadapncy, wont cue conditiom (the N-1 criteria) 111d odllll mna mllltipll coatillpDcill involvina combinatiom or 2 outqes to imd die wont c:111 1Cewiol (till N-2 criteria). Tbe wont cua round by applyina dllll pidllin cben111 witb Joldin1 pattmll, llllit and line maintenance outqes and IO Corda. f' I ~-25 -
PAGE 413
Power Teclaaolosl, lac. Thi adoption of these policies bu iDcrased the operatin1 security of the ia1lll'COIIDICted systems and lllldoubtldly reduced the frequency of occurrence of major cliltarba.,.. Utility opera&on make eYery effort to prevent cascadin1 outlpl from occvriDa llliDa IICIUity comtnined schedulina methods, to conime tbe eff'ICtl of a major balk power ou.... to a rlltricted area by usin1 planned .,.._ sqmadan wben required 111d to develop plam 111d schemes for restorin1 111 rice rapidly when 111d if a blackout or system separation occun. Tblll __. include die provilioa for l'IIIUlina suff"ICient aeneration capability to provide opendaa 111enes; tbat ii, there must be an adequate amount of 1eneration olllhll ia 1c1 or die Joecl demand 111d ia tbe ript locatiom 10 that contin1encies ca bl nrviwcl. Rwti power IOIIICII an made available to bandle emergencies. T...,,,,ieioe QltllBI are operatld witbia normal ratinp and transmission system opeaadoa ii coordinated rmapt iatercoawted systems, control areu, pools and ...... Thi eff'ec:11 of tbell Nq1U1'811181l11 are aaerally to reduce the trammislion system Joeclblp wl1 below dllrmll c:apabilitiel in order to bave the reserve capacity that ii required to bindle COlltiqeaci-. Generation ad VAR. supply scbedules are developed llliDa continpacy lllllym metbodl tbat include consideration of post COPtinpncy oacHna conditio111. Oft-economy locUna of 1eneration is the price that ii paid for tbell dlf'emive operatina 11Ctics. Metbodl for alleviatin1 system otrlolcll are incorpora18d ia many Q118111 control center systems that detect Piltina or pcaible abnormal system conditiom and develop operatin1 cban1es required to nmove tbe problem. Tblle operatiq 1uidelillll are not applied uniformly iD all systems because of the many diff ereDCII betwND individual 1J118111 aeneration transmission, load area diltriblltioa and intercollDICtiom to other systemS. Some systems use the single coatiqeacy criteria to flDd wont litultiom while othen use the double ~tinpncy criteria. Even if tbeN operatiq criteria were to be applied uniformly, tbey would not nnlt in identicll system reliability levels because of the many diff1r111C11 between IYlteml that exilt. 4~3
PAGE 414
Power Tlosl, Ille. The need to be concerned with system security is self evident. Widespread bllckouts, blackouts tbat penist Cor days and outaaes that coincide with severe weather may cause widespread economic loaes and endaaaer the health and safety or wae poups or people. There is a tradeoCC between these security concerns and the economics or the electric utility system. As in any situation involvina a tndeoCC or this nature there are bound to be difCerences of opinion concemina the optimum level of reliability/security. Allowiq that these ditTerellCII may exist and that there may be more than one siqle "best' mode or operatin1 a system, means that the deimition of available t,anmiaion capacity will vary Crom system to system and may even vary Crom time to time OD the same system. The N1101UC11 required Cor determinill1 tramCer capability limitations based on steady-state network conditiom illclude: 1. an adequate laid now computer propam (that is one sufficiendy larp to repri11ent tbe utility network or collClfll and its iaterc:olUleCted neipbon -2000 to 4000 bus models are common), 2. tbe data blle delcribiaa the network, loldl and aeaention system, and 3. a knowledp or the 1eaeration dilpatchin1 pncti~. Studill to determine tramfer capacities are normally conducted by committees of power system a,Jtaain1 enpneen from interconnected companies. Security comtrained c:lilpatebiaa is perfoa'med in the m01t modern control centen by the diapatcben in a real time control mode. r 404 4-27 -
PAGE 415
Power TtclaaolOII, lac. QUPl'IIY
PAGE 416
Power Teclllosla, Jae. CIIAPTla 5 naaOVJNG OPIJlATIONS OF cuauNT SYSTEMS 5.1 JNTaODUCDON The current IU'l'lllpments for pl1anin1, eagiaeerina and operatin1 the power systems have 1YOlved over tbe years in diverse fabions in various parts of the U.S. The lllltbodl 111d lffllllllll8Dtl 1118d vuy tce0rdina to the type of system, the patterns or ...-ado 111d lolda 111d the dearee of participation of a system with its iatem>DDICted neipbon. The indiYidaal utilities ue quite eff"ICient in their operations. Unit heat rates are mcmitmed cueully 111d units 1111U11ained reaularly to keep aeneration capacity in a aood state or repair. All systems with aeneratioa operate with an economic dilpaecla. Then appan to be a nplar and incrwina tendency on the part of 1,stema with hiper openda1 COit CIIJICity to seek out more economic sources or poww to parchue. One well known enmple ii the arowth of imported power from Ctnldwn urces to displace hiaber cost, oil ruec1 aeneranna capacity. M ... pointed out in an earlier chapter, there are a number of rqions where c:atnlly stisPatcbed power pools have been formed to coordinate the plans for SJ1tmD deftlopment and operate the systems economically to reduce both Iona run invt1tmellt COits and short nm operadna costs. These have taken the form of power pool llfNlllllltl tmonpt unaf'f".diated utilities and the coordinated operation Uld rmain1 or the tars utility holdin1 companies. 1'bele exiltina operations offer the outstandina eumple or a practical and tested way of improvina overall ef'ficiency or the utility systems in other areas. 5-1 406
PAGE 417
5.2 JMPaOVJNG lfflCIINCY BENEFITS OF POWEa POOLING AND BROKERS A recent article by Mr. Jobn Casazza presents an excellent summary of the results ud obllpdom of power pools [UJ. To quote: "We bave been tnckina tbe vinp resultin1 from interutility coordilladon ad poollq ner since tbe 1964 National Power Survey which streaed the need for illcnlled coordination. Our most recent evaluation of die benefl showed total national ncluctiom in excess of SU billion per year ua tbe biUI electric comumen paid in tbe last few yean because of intenatility coordination. Thell annnal vinp are expected to JICIIIMI to mon tball S20 bllllon by the mid-1990's. About tbne-quarten of dMlle avillll are dae to reductioas in capital investments and about o-cawter to fllll COit red11ctiom. 1'lllll ICOIIOlllic pim are subltutial and no doubt could be auamented with an nae beufi of poolina are blfnced by respoasibilides of tbe pool memben to deal openly ad fairly with IICh other aacl to exchan11 data freely concernin1 future load projecdom, ftPIDSion planl and operatina COits. Centrally dispatched power pools req1lire die iavtmlllt in a pool control center. co111111unicatioas and computer facilities IDd the support of an adeqaa1e eqineerin1 and dispatchin1 staff. These are not iDcouequential C0111. Ran ... of iaitial COl1S for a farae pool control cen1er bave been informally pvea at levels of 10 to 50 million dollan. A support staff of 30 to 40 profeaioaal level people miaht require an on1oin1 cost of 3 to S million clollan per year. These costs must be compancl to poaible reductions in system expansion cost vinp and annual operadna COS1S avinp that may be obtained from a central dispatch system for a larp enoup pool. A system with a peak load of 10.000 MW and foail rued aeneration would be expected to have an annual fuel bill in excess of a billion clollan per year. An opentina cost savinp of one-half per cent would be million clollan per year, enouah to pay for the pool operating staff costs siahted above. 5-2 -
PAGE 418
Power Teclalosl, lac. Tbe Jaraer block of avinp cited in the article quoted are due to the reduction in flCilitiel nquired to b1ad~ the load arowth in a reaion when the interconnected IYlteml plan uad implement system expusions on a coordinated basis. Generation imtalled reserve requirements are reduced when systems can substitute lower cost intercouection capability tbat llloWI them to share aeneration reserves for new pneration capacity. Thil ii quite feuible and bas been done in all of the power pools over the years. Tbe pool plannin1 '81Dintion, whether a holdina company staff or a committee oqan;-, from unaffWated pool memben, may plan for adequate reliability and lower pneration reserves by taldna advantage of the divenity in loads, the diversity in both planned and forced outages, and by coordinatini capacity additions so uw facilities ue im1alled on a pool need bail rather than by each individual system. Tnmmiaic,n plans can be studied and implementations developed that will provide adequate ,..mmisaio11 for Ui1!b101in1 power and eneray on a re1ular and --IWY bllil. Ill tbe power produc:doa area the coordination of operations on a pool wide basis ratber dla on individual system bail means that the most efricient units within the repon are beina used to produce the eDll'IY required by customen on a planned minimum COS1I bail. The consumers' COS1S are reduced overall by th.is production eff"JCimlcy. Ammpments can be made to allow the 1111 of the entire transmission system within the pool area for the mutual benefit of all of the pool memben. In most pools ties ue "free flowm1 eJimiutin1 the requirement for complex wheelin1 contracts. If tr1DPDitlic>11 ownership ii ll'l'Ullements can be made to share tnNmiaicnl COl1I on a relatively simple bail. New transmission capacity may be 11ilnned jointly to develop optimal systems at the lowest costs. Tbe hldiYidual systems must relinquisb somethin1 for these benefits. They must support the pool operation, both with sufficient fundiD1 and with adequate eqineerin1 support. The opentin1 IITID&ements mean that the most efficient production units in the pool will be operated to supply customer demands throu1hout r 5-3 408
PAGE 419
Power Ttebolosla, lac. tbe power pool The owners of these UDits must receive fair compensation and the parcbllen of the eneqy must be chlqed a fair price. The arranaements to accomplilh tlUI may require some 1111odation uad time to develop and implement. Individual Qltllll memben of a pool must qree to complete exchange of data and forec11~ which bu belll encourqed by the senerally non-competitive environment tbat utilities have been opentill1 in to date. The memben must be willing to coordinate plus IDd system developments. They must agree on generation plans IDd ,..mmiaio11 system collltnlet:ion. They must be willin1 to surrender some of their nspomibilitiel ia operations IDd tchedulina to the pool center. Finally they apee to coordinate pllDI to avoid system emeraencies, plans to coordinate corrective actions dariq emerpncies and plans to reston service after an ...,....,. does occur. It ii losical to Ilk at this point why then are not mon power pools of afrtliated IDd lllllffiJittld utilities. The wwer ii not clear. The potential savinp in operadna COltl do require a fairly lll'p pool size to support the annual costs of tbe pool operation. ne individual utility does not escape the need for its own operatiom control center by belonailll to a power pool or unaffiliated companies. (A boldia1 company may be diffennt with all of the seneration operated by a centraliad stalf of the parent or one of its service company subsidiaries.) A sabstutial portion of the available operatin1 savinp may be achievable by other mnm such u economic interchanae, power broken or long term interchanae qreemeats. There is also the very hWDlll nl11C1111Ce to surrender a portion of the individual sys1ems mamaf'ment responsibilitia and authoritia to a pool structure. This may be ampliiled by tbe replatory structure. Multi-state poolin1 may be discoura1ed by the aatunl parochial interest of state re1ulatory qencies. The coordination of pool operations requires an invatment in manpower for the proper functionina of the various committee structurel. Individual utilities may feel that they are meeting their service oblipdons to their own customen in an optimal fashion and believe tbat a centrally dispatched power pool would be superfluous. ,.. 4no U oJ 5-4 -
PAGE 420
Power Teclaaolosl, Jae. Power broken are one effective response to the reluctallce to Corm additional centrally dispatched power pools. At their simplest. they o.,..nize a regional market ror economic interchanp tbat baa been bandied by direct aeaotiatiom between iacliYidllll buyen and lien. At their IIIOlt complex, they arran1e for intercban1e tnmlCdom UDOqSt tbe participants and monitor the performance of the market in vina production costs. Their advutaaes, compared to a centrally dispatched power pool are the simplicity or the arnaaemeats required, and the relatively low cost of the broker operation. Their chief ctisadvaataaes, apiD compared to the centrally dispatched power pool are in the lack of a method for effectively coordinatin1 planning and system developmnt and the fact tbat participation is aenerally voluntary. In broker scbemll imtaPed to date, some typeS or economic interchange transactions performed routinely in a ceatnl dispatch do not take place in a power broker scheme because or tbe particular operatiq rules implemented. Another option to improve operatina and rJ1nnin1 efficiency ii to Coster the formation or more intqrated utility holdiD1 compenies on a regional basis. These 09ninriom could perform the planning and system development coordination u well tbe ceatnl dispatch of the generation. With a proper orpnin~onal stnlCtlUe 111d replatory eavuoameat. the centralized holdin1 company operations could comolidate many of the pl1nnin1 and operating control functions performed loc:llly at pnseat. 5.3 POSmBU IMPllOVEMENTS IN SYSTEM OPERATIONS AND CONTROL The improvements paaible in individual system's operations and control are hiahly specif"JC to tbe system and its cummt control system. This section will address two braid topics, the effects of reliability criteria on system operations and aenerally 1111ded .improvements in control of system operations. 5-5 ('I" 410
PAGE 421
Power Teclaaoloal, lac 5.3.1 System ()perada1 llellabWtJ Criteria This Sllbject 1111 been discuaed repeatedly in the precedina cbapten since it affects tbe fl'Mtfflismo11 capacity tbat is effectively available for normal system operations wbell 1J1tem1 are dispatcbed in a defensive mode to prevent ca1catUn1 failures. Tbere ii a need ror a simpler technique to cllaify available trammission and trusf'er capacities if tbe "'8mmiaio11 system itself is to be made available for KC8II by non-utility pvties. Even witbout tbat consideration, the adoption of 101111 simple scheme or determillina the available transmia~a capacity would be ......... in developin1 system schedules aad 8ffUII.Ul1 intercballae schedules. This is III analytical iaue that aeedl further attention. The divenity between 1ystem1 111d tbeir pattent or load 111d pneration complicate this issue. Even popapby plays a sipuJCaDt role. Take tbe peDiDlular portion or Florida u an eumple. The eJectric power systems in this naion are interconaected to the north with a limited number or biah voltaae circuits that aenerally are scheduled with beavy ecoDOIIIY intercbaqe power nows. If these should fail, these systems would -dally be isolated from tbe nit or tbe Eastern lllterconaectioa. It is natural tbat tbe operaton in this area would prefer a more conservative approach towards system reliability-llCllrity. One poaible approach to de"min1 available tnnsmiss\on capacity would be the adoption or a sinale security criteria or all or the systems. With the current schemes this would be the sinale coatiaaeacy wont case. Another approach mi&ht be to blle the development or reliability criteria for system security on a probabilistic Ullllllllnt of the reliability level. This requires that system operatina data be collected 111d analyzed in more detail than at present. It also complicates tbe poaibility of developina a sinate, simple criteria. One enpneerina approach that miaht be tried is that of correlatin1 the transmission and transfer capability levels developed 111in1 current schemes with the actual physical capabilities or the circuits involved. It may well be that there is a simple correlation in some systems which can be used to deime transmission capability. 411 5-6 -
PAGE 422
Power Tec ... lopes, lac. There ii ua alternative to defensive aeneration schedulina system operations, that of developina meam for ractina npidly enoqh to prevent casca,Haa failures after a co~rinpncy his occurred. To be effective, corrective actions should be trigered ....,..tically and flow diltributiom should be readjusted rapidly enoup to prevent fmtblt circuit outapl. For example, if emer1ency ratinp are allowed for a 15 miaute period, tbe corrective action should restore flows so that normal ratinp are not uc:eedecl within tbat time period. Corrective actions could involve trippilla units to relieve overloads and alleviate stability problems, automatic load sJtedcHna to relieve aeneration load imbalances or circuit npid imertioa (or removal) or circuit impedances to rediltribute power flows after a contiJlaency. nese methods have been used in specific CINI but bave not been widely applied to date. They must be carefully studied ad applied if they are to IChieve tbe same level of system reliability as ICllined by tbe defensive schedulina techniques. A ncent NER.C publication refen to these reactive protection schemes u "special prctKtioD s,steml (SPS). (20]. The nf'erence points out that these schemes are beiDa COlllidend mon frequendy a aa alternative to defensive aeneration ICblduliDa. The authors note that there is a concern that the widespread application of tblle complu 1ehemes may become a matter or concern ill future power 1J1t1111 nliability since the system security is dependent upon the correct f'IIDCtioaiaa or these special protective rysteml. 5.3.2 PoalMe 1a,........t1 la S11-Opendou aad Coatroll There appems to be a need for better coordination between power plant control ICllemel 111d .,..._ operatina controls. The npid response or power plants aids in the maia1e11111Ce or system frequency, the amelioration of system dynamic problems ad ia die rapid reduction of network overloads by shiftina aeneration. In the past boiler ad plut controll have been fairly slow with the control desian limitina st11am plant respc,1118 rat11 to maximum response rates of 3% of the plant's ratina per minute. With more modern boiler controls this trend does not appear to have 5-1 -412
PAGE 423
Power Teclaaoloal, lac. cbnpd. This observation is based on nports from system openton who have noted (informally) a trend towards poorer frequency control perf onD1Dce. ID tbe system control center and dispatchill1 area then is a need in the Iaraer intmcolUleCtions in the eat and west for the mon rapid, automatic and complete excblqe or current opentina data amonpt systems. There is currently a movement to develop a data excban1e protocol and SJ118m for the excbanae or data betweea intercouected systemi (89]. ID tile pat 15 to 11 years IIUlllY systems have developed improved system monitorin1 ad data c:omn-unicatiom systems at which allow the operaton to use actual network condition da1a in the operatin1 control systems. These systems may be extended so operatOn in one system have the capacity to observe and monitor coaditiom in adjacent systems. Some or this need, if not all, may be satisfied by the development of a rapid data ncbanae system. Table 5.1 below liltl operatiom and control actiom that may be used, or implemented. to enhance transmission system capability. The data in the table .iDdh:I optiom available for central eneru m1nement systems. They are poaped by tbe system sector affected, damaact. power production and the network. The entries in tbe col11111111 iadicatl the primary and secondary purposes of the listed control action [90]. r,. 5-8 -413
PAGE 424
TABU 5.1 0,..dw ... C..tnal Acdw I lauaclq Tn-1 u 1N Ca .. ltUlty ,,. rn rv GWIIGIID ,.. c-=-11 lrATICI ... Plll\9l1al IMWIIC .... ., ... WILT---PU, 1(1) LNIHtUlrt I LN-lff I I ,nm, ......... I ..... IMI. --, ,c WLVIIII ,c lmTATIIII PMDIZW ~vw camwsw P(Z) a BOL DIIMTallt P(Z) ,CZ) P(Z) .. --. ... 11 .. ,CZ) P(Z) wrm.- ,CZ) P(Z) ,.._ ----, I ... AUii----I ..... I LN lilffllGNI I ..... ,w VMN&T-. I ---LU!IUI I .. -I ftff11 (1) P,.,... u ,nary 1'*"' I ta 1111 f i...... .t ..U.v....,..l ftffl1 (Z) ,..,_.. te anlM INr _,Uy ......... (~ ..UCl,aHen) 5-9 f' I WLTMI I I I P(Z) P(Z) P(Z) I I I i l '114. CllffllL. M1DI .,_n.,. IDTCIIAnCII s I s s s s
PAGE 425
CBn:tll YJ
PAGE 426
CBAPna' PROSPECl'S POR INQUSING TRANSR CAPABILITY ,.1 IN'BODUCl'ION Table 6.1 summari.al tbe trammiaion ~tatiom dilculled in Chapter 4. TAIILI 6.1 INl.w.al LIM C..tralam Voltqe Comtn.illtl u. dllip puameten termma1 IQllipmeat ntinp Cumnt Comtnintl ccmdactor naia1 colldactorllfltime tenlWla1 equipment ntinp Diltribatioll or Power Flows Loop FloWI Voltqe-V AR. Comtraintl ad Traulnt Stability Economic Dispatch, Schedulla1 Security Comtrained Dlapatchin1 Poaibll remecliel are IUIIIIIWized 1D Table 6.2 r 416 -6-1-
PAGE 427
Power Tecluaolosl, Jae. TABLE 6.2 POlllble Tecolopcal llnNdla to lacnue Trwmluloa Capabllldes lllMDIKS TO PRYSICAL CONSTaAINTS ...... II ... ,. .... u,, Cgptra1111 VoltapUpradaa Tower Extellliom Improved Imulaton Non-ltllldarcl Voltaa New Terminal Equipment (circuit breaken, relays, tnmformen) Cunat u,rat1111 Dynamic Conductor Ratia1 Sq Aalamellt w1 Moaitorina 1leltriqiq (live-lille restrinain1) CblDaiq 0peradna Standards Toww Dalp ... New U... Convenioa to Multiple CU'C11it Towers Hip Voltqe Direct Current L.ines Multiple Pbae Una Live Line Collltnletion too, now Coatrol/Load Dlrilloa Redispatch or Generation PbueAllalelleplators Seriel R.IICtaDCI aNd Capacitance Sys1em Reconfipration HVDC Control Fatures llactlft Power Muaat Techalqaa Shunt or Series C&paciton Shuat R.acton Static VAR. Compematon Synchronous Co11demen Oeneraton u VAR Sources ri 417 -6-2-
PAGE 428
Power T1elaaolopes, Jae. TABLE ,.1 (coadaaed) ....,.._ IP Puee1s u4 Xntl& SghJJltJ Co11tnJ1g lledacina Clearina rune Series Capaciton Rapid Adjustment of Network Impedance Generator Trippin1 and Fut Runback Fat Valviq Brakiaa llesiston and Load Switchina Kiah-Speed llecloliDg Achaced Excitation Systems and Stabilmn Tnmient Excitation Boost Fut Ac:tiq Phase Anale Reaulaton Generator llelcton SVC, 111d Synchronous Condensers Sectioo1Uzio1 (Addina Switchin1 Stations) The metbodl to nlieve tbe physical tnmmission limitations all involve physically 8111uJia1 tbe ,...,..,,iain capability in a system [47, 48, 50, 91 -93]. They may .iDcrwe b'IDIJDiaic>11 capabilities in some systems by sut,stantial amounts. All of tlllN metbodl ue upemive IDd may require the removal of the circuits involved for a prokmaed period. The comtractioo of aew circuits ha been the preferred method to increue l"IDmiaion capacity tbroupout the PIil development of the utility systems. The current difficulties with ob11inina riahts-of-way and permits to construct new circuits coupled with the decrelliDa load arowth rates of recent yean have made this a more time consumiaa, mon expensive and less likely alternative. ,.1 LOAD DIVISION LIMITATIONS The previous ctilcaaiom point out the limitations that may arise due to the automadc, imtaataoeoua division or power nows amonpt the transmission line in a network. One aaeric problem thlt ha occurred a number or times in the growth or utility networks ii the overloldina of lower voltqe lines that have been penlleled by tbe subsequent comtractioo of new, hiper voltage circuits. These low voltap circuits may be overlolded in normal conditions or when a parallel 418
PAGE 429
Power Tecbaoloal, lac. hiper voltqe line is opened (e.1., to clear a fault) and the power automatically starts to now on the low voltage line. One practical and inexpensive method used to cun thil problem is to open one or more breaken on the low voltaae line(s) and operate them u radial circuits to deliver power to major load stations. This cures tbe overloldin1 problem, but may reduce the reliability of supply to the load subl1atiom since these stations may now be served by only one circuit path instead of two or more. Pbae anate rqulaton, usually in the form of phase shiftin1 transformen, may be imtalled in a circuit to increue or limit the power flow over a given line. Recall that the power now on an ac line is proportional to the sine of the angle across the line. The phase shifter introduces a f"aed an1ular difference in the circuit that mast then be sadaied by the proper power now. Pbale shiftiq tnmformen have not been aenerally applied. They introduce added requirements for VAR supply ad their operatin1 reliability has not been the best. Nevertbelea, in some systems outside of the U.S. they are used quite frequently to control power nows over a few specific lines. Current costs for phase angle replatina transformen (u well u other remedies) are discussed later in the section on transmission costs. It is possible that future developments in high power electronics may see the development of power flow control devices that permit the precise control or power flows over individual high voltage ac lines. Theoretically, this would now be feaible usina existin1 high voltqe, hiah power apparatus similar to that used in de transmission circuits, but the costs would be very high. ADother method that may be used to limit the effecu of load division is to introduce circuit elements in series with the lines to increase or decrease the effective line impedance. This method hqs been used to increase the stability limits of Iona hiah voltaae lines by placin1 series capaciton in the line. The principle drawback bas been where these series capaciton have led to the development of sublynchronous resonance problems. _,_,._ r -41 9
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Power Tecllaol..-, lac. TIie recoDfipration of tbe system on a temporary basis after the occurrence of an oucaae may alleviate the potential overloadiaa or portions of the network. TIie mast widely 1118d technique ii to redilpatch the system aeneration to relieve die load division problems. TIie system operaton must have the system data aftilable on a real time bail in the control center in order to accomplish this effectively and the control center must have the proper computer program routines aftilable. ltedilpatchina the system aeneration increases the system's production costs and requires that enoup capacity be available to shift generation fairly rapidly. Means are available to enbnce tbe nspome IDd control chancteristics of a great deal of uiltina pneratioa. Tbe tecbmque ii quite effective: cost penalties associated with aoa-opdmal generation schedules are highly system specific. 6.3 VOLTAGI LJMITATIONS T"IDRDnm11 limitatiom due to voltap related problems may be alleviated by a number or metal. One larp poup of poaible techniques ii related to increasing tbe availability aad controllability or VAR supplies on the system. Capaciton may be iDi1alled at statiom to incnase the available supply of V ARs. They may be desiped so that wryin1 amounts or V ARs are supplied by switching capaciton bub in IDd out of service. Series capaciton may be installed in series with lines to reduce the VAR IOIIII in the liae and increase stability limitations. Synchronous coDdemen IDd static VAR compensaton (SVCs) may be installed at the eadl or circuits or in intermldiate switching stations on long lines in order to provide a controllable IOUl'Ce (or sink) or V ARs. These devices are also used to illcrNN the stability limits or lonaer hip voltaae lines. These techniques are quite effective. Typictl COits for VAR supplies are discussed below. Addina intermediate switchina stttiom on Iona high voltage lines will reduce the illCJ'llle in VAR losses when a portion or the network needs to be removed to clear a fault. This ii true because the intermediate station reduces the increase in 420
PAGE 431
Power TtchaolOINI, Jae. s,stem impedance resultin1 from a switcbin1 operation. This is an effective but ezpeaaive remedy since additional busworks, protective systems and circuit breaken ue required at each new 11atioa. All operatin1 teclmiq that may be used (or required) is to run 1eneraton in or D8II' tbe lold areas to have available VAR supplies online to handle emergency conditiom. Oftea, these are aeneraton that would not be run under a normal ecoaom.ic schedule so this remedy also increues the system production cost. A .... tecbaique that ii beina more widely applied is to incorporate methods to dispatch VAR supplies at tbe same time that power aeneration is beina scheduled [941 91]. These tecluuqua, called optimal power nows are imbedded in computer propm delianect to develop voltap-V AR schedules simultaneously with the economic dilplt.ch of the aene,ation system. They may be desi1ned to recopize die poaible eff'ecta or coatinpaciel lllcl are, thus, extensions of the security COllltraiDed dispatch tecluaiques mentioned previously. To date (January 1988) these techaiqael have uaually been used in ID off line, or study mode to investipte and determim vol .... -V AR schedules. It ii aaticipated that the future will see more applications in the real time control of the systems. The cost of implementation is tbat related to obtainilla tbe required software. An approximate cost is in the neipborhoocl of $100,000 per installation. This would be expected to decline as mon products enter tbe software market. 6.4 SfABILITY ULATID LIMITATIONS There are a number or techniques that have been used to alleviate stability related limitations. Some or these were mentioned in Chapter 4 when subsynchronous resonance wu dilcusled. Most or the techniques mentioned below are related to the claaical tramient stability limitation or the dynamic problems causing low frequency oscillations or power. Their expected costs for implementation are highly dependent on the exact system conditions. They have all proven to be effective, but each situation requires careful exmiJ,ation. ,. I _,_,_ 421
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Ponr Tecbaoloper, lac. Transient im1ability ii initiated by the occurrence or a fault (i.e., a short circuit). Faults are removed by tile combined actiom of the relayin1 system which detects tbe fuilt 111d si1neh hiah voltaae circuit breaken which remove the short circuit by ope,ain1 the faulted circuit. The leqth or time required to clear the fault is an important determiDallt of tbe eneray available to speed up the 1enerator(s). The futm tbe fault ii removed, the less the aeneraton are accelerated, reducing the chance tbat the system will be unstable. Modem relaying and protective systems which bave fut cleariq times are available. These may be u low u 2 cycles (i.e., I/30th or a second.) These may be imtalled to assist in reducing the effects of stability probleml on ,..nsmwioa limitations [72). Another way to reduce tbe potential errects or faults is to deliberately introduce additional impedance into the Mtwork to reduce the fault current that may flow when a line suffen a abort circuit. Breakin1 resiston may be introduced into the 111twork to absorb some or the kinetic eneray in the aeneraton that would othenrile serve to accelerate the unit when a fault removes the load on the macbioe [II]. The me or series capaciton on Iona hip voltaae circuits is a more-or-lea standard way to reduce the errects or tnlll.ient stability limits. The series capacitor reduces the circuit impedance. allowiq a hiper power transfer at a smaller anale dif'f'ennc:e acroa the network 99, 100). Control schemes to reduce the loldina on aeneraton rapidly durina severe faults will also belp the stability problem [35, 76, 77]. "Fast runback" systems are desipecl to reduce loldina levels while keepina a unit online. In the extreme, units may be tripped. MllluflCtUl'en of steam turbine aeneraton 1enerally do not recommead llllit trippina siDce there is the possibility or dama1e to the shafts of the machines. Another variation of this technique is to combine the introduction of Cuter valvina systems on the steam turbine-boiler system alona with bypass system1 to tramrer steam that would normally be directed to the turbine into a bypua tbat directs it to tbe steam condenser. These methods have proven very effective in systems where severe transmission bottlenecks have occurred. Steam r,;: 492 _,_,_ \ ...,
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Power Tecluaolopa, lac. by-pass systems appear to have been used mon in European practice than in the U.S. The severity of faults may also be reduced by the use or rapid reclosin1 of circuit breaken or siaale pole. circuit breaker switchina schema. Many short circuits that occur on tnmm.ission systems an or very short duntion and are due to liahtning strokes. CleuiDa the fault rapidly and then reclosing the circuit automatically after tbe fault bu been ntinauished by the automatic action of a lightning arrestor reducet the time the 1eneraton an accelerated and increases the chances for the system to rmtore itself to a stable operatin1 condition. Reclosina is widely used OD major hip voltap circuits. One disadvantage is the possibility of causing sbaf't dlmaae OD the steam turbine aenerators if the reclosina is done at such a time tbat severe electrical torques an imposed suddenly on the units. This may bappea,, ror example, if tbe switchin1 isolates a unit and accelerates to the point wbere there is a laqe uplar diffennce between its rotor and the rest of the system at tbe time of nclolina. The 1111111 coafipradon on a biah voltaae circuit breaker installation is such that all three pbllel an interrupted when the breaker is opened to clear a short circuit. n. vut majority of faults on hiah voltaae ac transmission circuits are caused by liahtlWII 111d involve only one phase or the three phase circuits. "Sinale pole switchiD.. schemes may be used when the protective system detects which phase is involved and only opens that pbue to clear the fault [72). This bas the advantage tbat the power tramfer over the line is not suddenly reduced to zero since the other two pbael an still in operation. Then(on the electrical loading on the nearby pneraton is not reduced to zero and the units will not accelerate as much u they would bave if all thne phases bad been opened. These schemes for special circuit breaker actions are not major cost items when compand to the breaker cost. Advanced control systems in the form of modern excitation systems and 1enerator stabilizers are bein1 widely applied to both new and older units to ameliorate dynamic problems [73 75, 80]. These systems contribute dampin1 to the system tbat serves to reduce the risk of instability. Increasin1 transmission system loadin1 always increases the risk of transient or dynamic instability. These modern ()( _,_,_ ,1')<') 'l -'--'
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Power Tecllaol ..... lac. excitation IDd stabilian reduce this risk and allow the increase in effective tw'INJDiaioa capacity. They have proven effective in systems where they bave been applied. COits mentioned by stabilizer manufacturen ranae from S50,000 to S150,000 per 1eaentor unit. AddiD1 controllable sources of V ARs also reduces the effects of stability on limiting tnmmiaioa tnmfen. They ue used fnqueady on 10111 hip voltage lines to support voltages IDd increae the likelihood that systems will remain stable after tbe occmruce of a fault [IOI 103]. Each system tbat 1111 a dynamic problem requires a detailed investiptioa to imd a saitable, economic tbod for nmedyia1 the condition. Care must be taken that the preacribed cures do not cause other problems. The classic case is the iatrod11ctioa of 111bsynchroao111 nsolllllCe problems ia systems that had installed series capeciton to alleviate tnmient stability limitations. The interconnected power system is a complex electromecbaaiCII system with many levels or controls. The opportunities for iaterf ereace and disastrous interaction between these is always I COIICll'D. ,.s SYSTEM CONTROL LIMITATIONS The limitations on transmission transf'en that arise from system control are primarily due to the coacerm with system reliability aact security. These are COIIC8l'IIICl with both dynamic operatin1 problems and static problems that may arise after a coatilapncy bu been survived. If a coatin1eacy of some kind results in a poat-coatiqency condition when elements or the transmission system are overloaded., the system operaton have a maraia in capability which is the excess capability between the sbort term emergency ratiap and the normal capability ratinp of he network eleants. This emergency capacity is generally allowed to be used for 15 minutes after which the loadinp are to be reduced.
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Power Tecbolopes, lac. If ID outqe or otber operatina problem does result in the need for drastic action, die operaton should have a plan for carryina out this in order to minimi:re the comequences to tbe system. 1'hlll emeraency control schemes include: o controlled separation of tbe system (sometimes called is1andin1) tbat attempts to create isolated anu where load and 1eneration are ilP blltnce., o scbecluled trippina of aenention to restore the power balance, o 11N oC fat response VAR supplies, o load sbedd!n1 by nducina system voltage levels, usina load mlJlal8llleDt 1ystem1, appeals to customers, droppin1 interruptable CllltOmer lolds ad direct load sheddina by droppina substations, o redispatch of pneration, and o NICbedulina of intercbanae traasfen. Aftllr die occurrence of a major outaae which may have created islands where there is no pneration. the system operaton need an effective and efficient plan to restore tbe system to normal fut poaible. This must include the capability to restart power plaats that bave no survivin1 connection to the system (i.e., "black S1art capability') that may require the installation of local diesel enaine 1eneraton to provide the un:iJiary power required to restart. Plans must be made and carefully followed so the system can be reconstructed and loads picked up in an orderly fahion that does not initiate further outqes [104]. I A common problem to be avoided is that of "backf'eect where a plant may eneraize the transmiss~on system in areas where operaton and line crews have assumed that they are deeDeramcL This is similar to the backfeed problem that arises in a prolonaed weather induced outqe in a distribution system. It is more than likely to be the cue that one or more of the residential customen will have an emeqency aenerator online. If the customen' connections to the system are not opened, the emeraeacy generator may eneraize circuits that line crews have every right to believe are deeneraized. Line crews attemptin1 to restore service (\ -6-10425
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Power Teclaaolosl, lac. (nq1181ldy must conduct door to door surveys to ensure that the system is not ICCideatally eneqmd. Tu uiateDce of emeqenc:y control systems and restoration plans may make the utility operaton more apeeable to a lea conservative approach in the application or reliability criteria for the development of security constrained dispatches and illterclwlp schedules and thus utiliz.e more of the physically available transmission system capacity. Tu ..,_urioa of these reliability criteria (e.1., the use of a sinale contin1ency cri1eria ratber tbaa a double contia1eacy criteria in developin1 secure 1eneration 111d tnmfer schedules) is probably tbe most effective method to achieve an WD"1 pin in transmittio'l capacity at the lowest initial cost. These reliability criteria establish the balaace point between system ~ty/reliability and .,._. operatilla COl1I 111d t\'anammion system utilization. The limits set by the applicatioa or tbll8 criteria are much lea than the physical limits of the system compoaeats since tbe 1118 or a security constrained schedule keeps transmission capability in reserve to survive tbe wont c:ae coatinaency. Tu other consequences or adoptiaa lea restrictive reliability criteria should be caref'ully COlllidered before they are relued. These criteria have evolved over the pat operatiaa history of the interconnected systems as a consequence of the ezperieacea with several major, widespread blackouts. As with any reliability criteria or standard, the acceptance or any criteria is very subjective and dependent on loc:a1 conditions. TIJe effects or a blackout in a laqe metropolitan area are apt to be much more severe to the coasumen than to those in a small urban area or rural area. The interruption of production at an industrial plant certainly carries Ill economic penalty. But, what is the economic value of electric service where its illtemaptioa may eadaqer life and limb? Certainly these kinds of questions have uswen, but not answers that we can all qree are universally applicable. The recent (1917) concerm over airline reliability and safety are one example of this disqreemnt. -6-11-() .-426
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The ~nae in tbe number or interchlll1e transactions, the introduction or power broker 1ebemel IDd tbe powth or non-utility power 1eneraton (i.e., co1enerators, qaalif'."Jed facilities IDd independent power prodac:ers (IPP's)) have increased the compluities or system opendon and iDcreued the security-related operatill1 concerm. With tbe pneration and tnnsmmion system operation under the conttol of the system operaton, die responsibility for both economic and secure operation is in one place. The introduction of non-utility resources on the system divides thil respomibility. For eumple. a coaenerator that is producing steam for an iDd1lltrial procea usina a combined cycle plant may not wish to curtail its generation became of tbe need for procea steam. The plant may. in fact, not be capable of producias tbe required stllm flow without producin1 an excess of aeneration tbat mast be ablorbed by the rest of the system. ,.s.2 Power flat ..., .... Ia the preyio111 dilclllliom or system dynamic problems and stability effects that may limit tNDlffliltic>'l 11dJintion. the phenomena and control ICtiom all take place in fnctiolll of a second. ID die redispatchina of aeneration to avoid overloads the required actions need to be accomplished witbill tbe time period of the short term emeqeacy overload ratilll of the trMsaission system components, usually 15 minutll. Tberef'ore one of the factors to be considered is the ability of the system generation to be redispatched after a contingency witbill this period. That is, planes must respond unally within 15 minutes to put the transmission circuits within tbeir normal ratinp after an outqe [105). Hydroelectric units and ps turbine plants have very little problem in changing outputs witbill a short period aaumina that they are not at full output. Steam Ullits are generally capable or respondina within this time fnme, but may be limited by their control systems to a slower response rate [ 106, I 07]. Governor response is not releffllt in this connection. On the various interconnected systems the outages or even major power plants will cause only a small frequency deviation and the governor respome is fairly rapid. The transmission overload problems are area problems and are therefore related to the slower control actions of the AGC systems. '127
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hwTec ......... ,Iac. a..,... ,.. or ..... turbine Ullitl .,. limited to minimi:re tbe thermal stresses md PGIII,_ metllharp:al fatipe tbat coald arill from frequnt tbermal cyclina caill9d by rapid ud Creqaent load dwDIM Relpome raam for steam Ullits are typically lim.itld by their CODtroll to a mzimum or about 3'9 or tbe unit's ratiaa per miaat8. At Illy pva tuDI D9t all or tbe uaitl OD a system will be operatina widlia coatrol rap. Some will be at mzimum output because of economic operltiDa ICbedulll while otben may be tun off control by plant operaton to minbnize wear on tbe ait IDd avoid future maiatnaDCe problellll. It is quite likely dlat oaly 15 to 2. ol die capacity oDliDe at any aivea time will be within control nqe. Swppme tbat tbere ii a IOII illlbetnce or paeratioa ud load in III area that bu 2ft al die capacity widaia tbe control nap. At tbe mexim111D response rate of 3% per aia it will take cmr 15 IIWI-to restore tbe pneration load balance. (Tllat ii, (ICM MW)/(0.2 x WI MW /Mimd8) 16.67 mi.Dates.) Protective relayin1 ICN!NI may opea circuits before tbe plants have J'IIPOIMlld to red1lce die tie flows witlaia tbe uea. Theref'on colllideratioa of t11i1 IIPOW ii imr,ortut wbell comideria1 traJllmission Jiwi111kml. One ef'f'ectift tecJmiQue ii to require more Ullia to be under AGC .,_.coatroL Uait loectinp may be reduced rapidly by tbe UN of tbe techniques discussed prnioally (i.e., fut nmbeck, steam by-paa, etc.) Tbe output of a steam turbine may be iDcrwed by several meem Ooi.na to overprman operation or operatin1 wida die ltllm valves wide open may iacrwe the mximum output by 5% each. It is 1a1otit tbat the aenerator bave capacity to produce this increased amount or power. It it is flllible, a hiab pnaun feedwater beater may be removed (i.e., cm oat9) die: 111jn1 die available output by a much 6". The UM of an asillvy boiler ud die Joweria1 or reheat steam prmure oa a reheat unit may illcl die output by about 319 each. It wo111cl not be expected that all of tblll meuures could be Ulld simultaneously on a aiYID uait. But. it would not be uaunal to be able to obtain a I 0'9 iacreue in output. ()penda1 plalltl in dul fubioa may place the plant at a ll'ftter risk of 13-fl r 4 2 8
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Paww Tlmol .... lac. failare. 1111 poaibll cowqm ol iacreain1 plallt output must be weiped c:anlaUy apinet die pill ill trlNPDWion syl18III ntilintion. Tbe immediate cost of ........_ may bl low, bat die 10111 tmm efTectl mlllt bl comidend. 0111 dmrbact to die ialm'C:OIIDeC1ld operatiom of utility systems is the possibility ol ll&Yilla to sban lald cmtailmentl ad poaible l1lltailled low (requency operation wlllll u iAIMWNCt8d 1)1181D lllfTen a ._. outqe. Tbe AGC system operations (dllcriblcl ill Cllapcm-3) an deeiped with die illtat that acb control area is ,..,...;,. ror atid'yma itl OW11 dlmen Power tbat bein1 sold, parcbwd or 1Y1111lld duoaab die .,..._ oa a ICMdaled balia, or it flowiq tllroup tlle system to lldd'y tbe .......-cy npledoll Dlldl or u edjaceat system, does not illcreue die ... COIIUOI enor loaa die fraqaency deviation small. At some point darilla lfN1'117CJ tbe fnQIIIIICY dffiadoa may came tbe normal system1 to beain to iDC!1u1 ....,._ to add'y die load clemaDd OD die interconnection and altiw-'Y aormal sy1tem1 _, start to abed load to prwrve the iatercollDICtion. ID may np,m IJl&IIII openton ill ldjlceat uw have worked out arnn1ements ror mataal llliltaDCI ill CINI or prolonpcl emerpncy operation. Voltqe red1lctiom bl deliberataly impolld on tlll eatire rqioa to reduce demands. lalll'CHMCtlNI 1J1t1m1 with ldeqaata paeratioa may shed loads in order to pr111r,e die infelrity or tbl entire iatmcouected rqional system. Deliberate ,,.._ IIPll'ltioa. that ii. opllWII circuit breakln to ilolate a system with a wio111 ....,._ sllortap (called Ddia.-in iadustry jaraon), is usually a last naort. It done to pnt die pneration sbortqe or blackout from expandin1. E1118rJ8DCY plaDI will call ror -.,.ratiota sucb that the loed and demand balance can be main1lilled or restored witb.ia acb iaiaDd. ADodler epproach it poaible 111d bel been dilcuaed iaformally by at leut one midwcera utility, ;. to limit tbe sbarin1 or loed loall (i.e., reduced voltaaes and dellbenle load sbedclin1) wbn tbeir system is itself atilfyin1 the native demand witb ill own paention l'IIOun:11. TIie system would use a sipal similar to the ena control error (ACE) to detect and clilcrimiDate between internal aeneration fl' 4 ')Q -6-1,4'-'
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Po__. Tecbaolopel, lac. shortapl IDd prolonaed monaa outside their system. If the frequency remains low iDdicatilla a aeneratioa sbortqe on the intercolllllCtion, and at the same time their internal load and pneratioa ii in blJnc:e,. they would deliberately isolate their 1)'118111 by "l)lllina all or the ties to tbe interconnection to avoid bavina to curtail ~ir own customers. This would be done automatically. There ii merit in both apPfOIChel, slwina in curtailments to preserve the intercoDDection or deliberately ilolatina a sound system to avoid importina a sbortap. The voluntary qreements reached by non-competina, interconnected utilities to preserve the intercomaection 111d share in the emeraency procedures that may require load sbed
PAGE 441
Power Teclaaoloal, lac. Table 6.3 below lists the line desip characteristics affectin1 construction costs (19). TABLE 6.3 Lia Dellp Characterllda Aff ecda1 Coat Line voltage LocUna (mepwatts) Choice of 11111ual c01t or present worth analysis Number of conducton in study Insulation cbaracteristics Pblle bundle confiauration Number of circuits Span lenath ruae Ground wins: diameter, weipt, and cost Pbue IPICUII Number, type, and cost of insulator units Ice thickness Wind preaure on conducton Unloaded 111d loaded tension Broken conducton 111d broken conducton tension Allowable conductor temperature Groud cleuances Tower type Tower 111d foundation weipt flCton Tower 111d foundation steel excavation and backfill costs Tower setup and assembly costs Pullin&, naina, and clippina costs Loa flCtor Plant COit Eneray cost Interest rates Groundina Transpositions The cost dlta in this section are quite approximate and are based upon published survey dlta, manuflCtUrer's price handbooks and experience in assessin1 different proposed tl'IDSmiaion schemes [108 111). The dlta aiven are estimates of costs for various types of apparatus used in power transmission. In most cases a range of dlta are aiven that reflect the extent of dlta from different sources. r j31 -6-16-
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Power Teclaaolosl, lac. The major elements .involved include: lines, circuit breaken and protective equipment, tramformen, and 0 0 0 0 VAR support and voltage control appantus. Liu Coats Lille costs per mile vary with voltqe level, type of tower construction (wood pole, lattice, etc.), number of conducton per phase, conductor size, tower design, etc. No simple estimating formula appean to be accurate for all cases although they may be ror developilla approximate values. The 1917 N1lR.I report "Some Economic Principles for Pricilla Wheeled Power" contains tbe results or a survey of line construction costs performed II part of the reported effort [19). These data were aaalyad and fitted statistically to develop Nrimted costs for various regions of the U.S. and for different voltages, etc. The results are summarized on Figure 6.1 which shows the approximate cost in tbouuds or dollan per mile II a function or the line voltage rating. The heavy line represents an approximate mean values for the various reaional data and the bandwidth represents the range of cost data for different regions. Costs are in 1915 dollan. These data show that the expected costs rise with voltqe rat.ins at a rate which is much lea than one proportio.w to the square of the voltaae level. Since the tnumiaioa capacity does increase approximately II the square of the voltaae level, the cost per MW-mile of transmission Cll)ICity declines quite rapidly with voltaae. The llllll report shows data i.ndicatina that the reported capacity costs declined Crom S1000 per MW-mile at I 15 kV to S 150 per MW-mile at 765 kV.
PAGE 443
Power TtcbolOII, lac. 100 700 i ..... I! / 800 0 / Q II. 500 0 CD // / // Q i 400 0 300 ~;:/ t; 200 0 (J w z 100 :J / 00 100 200 300 400 500 800 700 800 UNE VOLTAGE (KV> Plpn 6.1 Approxlaate ac OYerbud Traualuloa Llae Costs. 1917 NRJU Report So lcoaomlc Prlnclples for Prlda1 WbNlld Power" (19) Direct current line costs are more difficult to classify since there have been so few eumpl. ID some recent eqineeriD1 pl1aaia1 studies estimated costs ranaed about the same tbole for the IC lilles shown on the previous fiaure except that the line voltaae bll to be UDderstood to mean the positive or neaative de voltage rating or the line. For example, a 138 kV IC line may have an estimated cost of about 130 to 150 thousand dollars per mile. A de line with a positive and negative voltaae to around of 150 kV could be expected to have about the same range of costs per mile, 130 to 150 thousand dollars. -6-11-
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Power Tecbaoloal, lac. These data are in reasonable aareement with the data in the 1987 Oak Ridge National Laboratory Report [101). Tbat report presents an example showin1 that ac line COltl are approximately S1,000 per kV per mile, where tvrefen to the line voltaae ratina in kilovolts. They further cite an example of de line costs that are approximately $800 per kV mile, where in this cue the tvref en to the de voltqe to around. Usina these data a 131 kV ac line would cost S138,000 per mile and a :t. ISO kV de line would have an estimated cost of S120,000 per mile. These 111d 1imilr data should always be used with caution since the cost of right of-way can influence actual costs aready. 6.6.2 Chcalt Bnabr Coltl The iDstalled costs of ac circuit breakers includes the cost of associated protective relayiq and instrumentation systems. Data available are limited [108, 111). Approximate installed costs are shown on Fiaure 6.2 u a function of voltaae rating. Actual costs for specific installations will vary with the type of breaker, its interruptina duty ratina, etc. Data obtained from plooioa studies show ranaes of COit estimates. that vary by 50 to 75% from the typical data on Fiaure 6.2. 1100 l00 l00 8 I 400 i zoo 0 L-,..J.._..___.... ______ ..._ __ 0 100 HO HO 400 IOO HO 700 100 KILOYOU'I flpn 6.2 Approximate Iutalltd Costs or ac, Hlah Voltaae Orcalt Bnaken u a Fuacdoa or Voltaae Ratln1 r -6-19-434.
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Power Techaolopa, lac. ,.,.3 Trauforaer Costa Tramf'ormer costs are also a CWICtion or many puameten besides voltaae. Some are two wiDcliaa tnlllf'ormen. some have three or more windinp and some are auto-tramf'ormen in which a sinale winclina is tapped to transrorm voltqe levels. Tramf'ormer COit data were obtained Crom manufacturer's standard. published data. (The specific tramrormer cost data below were obtained Crom published price data Crom Westinpouse. Cataloaue price levels were adjusted to reflect current (I 988) market conditions and are. therefore. typical, data.) The costs given are the estimated purchued cost. Installed costs would ranae Crom 125 % to 200 % or the tnmf'ormer cost itself. Fiaure 6.3 indicates the ranae or costs expected and how they vary with size and the hipest voltqe ratina. For a given transform.er desian type and ratina in millions or volt-amperes (MV A). the cost per thousand volt-amperes (kV A) iDcreuel with the voltqe level of the hipest windina voltaae. The upper curve on the C"ipre ii shown for a two windina transformer rated 120 MV A. The cost per kV A at a aiven voltqe level declines with the ratin1 or the transformer. The bottom carves indicate a very approximate ranae for transformer sizes which are appropriate for each voltqe class. Generally two winding transformen are more expensive than auto transformen. Phase shirting transformen are a special desi1n of transformer and have a higher cost. Imtalled costs or reautar transrormen, includin1 tap chan1en for voltage control. may range between a low of about 1.00 $/kV A up to 7 to 9 $/kV A. Phase shirting transf ormen will run in the neighborhood or 7 $/kV A and up. Again. it should be realized that these costs are quite approximate and the cost of any particular transformer has to be determined considering a number of factors that may influence the desian and therefore, the cost. ( -6-20-
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Pow Teclaaolosl, lac. 1 3 a 0 ...................... ...... ________ 0 100 100 300 400 500 IO0 700 100 KILOVOLTS flpn 6.3 ApproJdllate PuclaaN Price of ac Power Trauformen. lmtalW Cola llu1e froa 125 to 200~ of die hrcbue Price. 6.6.4 V AJl S.pply ud Voltqe Coatrol Apparatu Shut nacton that are applied to limit line volta1e rises cost between 5 and 1 S S/KVAR installed. Shunt capaciton may cost u low u about 4 to 5 $/IC.VAR for the capaciton alone. In switcbed banks. the installed costs are typically in the nap or 13 S/KV AR. Series capaciton used to nduce series reactance effects cost between 8 and 13 $/KVAR. Static VAR compematon (SVCs) are currendy reported to cost 25 $/IC.VAR for sizes in excea or 50 MVAR and 30 S/KVAR for smaller sized installations. The costs for de terminal apparatus. converten. inverton, harmonic filters, controls. etc. have run between 40 and 65 S/K.W in recent studies based on manufacturer's data. -6-21-
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Power Teclaaoloal, lac. Undeqround hiah voltqe, ac cable costs for hiah capacity installations run about 7 to 10 times the cost of an equivalent voltqe class overhead transmission line. Ulldeqround cable costs an very site specific [23, 112]. 6.7 APPROXIMATE COSTS FOR NIW AC TRANSMISSION These cost data may be used to develop approximate installed costs for new ac t11nsmiaion circuits. Fipre 6.4 shows typical circuit capabilities u a function of the ac line voltqe ratiDa for 50 and 200 mile Iona ac overhead circuits which are blled upon the surae impedance loldill1 discussions in Chapter I. The capabilities of die shorter lenath an typically limited by voltqe-V AR limits and those for the 200 mile lille by stability considerations. 8000 5000 4000 3 2 3000 2000 1000 0 0 100 200 300 400 500 800 700 800 KILOVO&;.TS flpn 6.4 Typical ac
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Power Tecluaoloala, lac. rJIUN 6.5 shows the approximate installed costs as a function of voltage for each cUatance. These wen timatecl usina the cost data above and do not include costs for any additional VAR suppli that miaht. be required. The costs for the 200 mile lines do not .include any intermediate switching stations nor series capacitor compemations. These "typical" C0l1S would be expected to vary widely depending upon the costs of ripts-of-way. 140 120 100 a, 200 MILES cc C 80 IL 80 0 a, 40 3 2 20 0 0 100 200 300 400 500 800 700 800 KILOVOLTS flpn 6.5 Approximate Total lutalled Coat of ac Tnumluloa Circuits The COl1S may be interpreted in terms of a capacity cost index, dollan per MW-mile by dividin1 the installed costs of Fiaure 6.5 by the respective line capabilities on Fiaure 6.4. The results, shown on Fiaure 6.6., demonstrate the decline in trammission capacity costs with ac line voltqe level. r, -6-23-
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Power Techaolosl, lac. 1000 900 800 700 800 w _, :I 500 I 3 :I .... 400 co a: C 300 0 200 100 0 0 100 200 300 400 500 800 700 800 KILOVOLTS flpre 6.6 Capacity Coats la Dollan per MW-mile for ac Traumluloa Circuits -6-2 .. -
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Pow Teclaaolosl, lac. CIIAPTEJl 7 WHEELING AND NON-UTILITY GINEllATION 7 .1 INTllODUcrION The previous Chapten provide a ,urnmary of the sipificant technical aspects of existina power systemS and their operation that may restrict or limit the use of hip voltap tran,miaic,11 systems. TechDical remedies are available that may allow iDcremental incre in the capacities or existina transmission facilities. Major traDUDiaio11 capability increaes require the buildina of new facilities or major reconstruction of existiq circuits. In the aeneral review or wheelina and non-utility generation in this chapter it is assumed tbat the current industry structure remains basically as it exists today (January 1911) in order to review currnt and expected technical issues concerning wheelina and non-utility aeneration. Transmission access is presently generally limited to electric utilities and non-utility aeneraton. Electric utilities are taken .to .inc:1ude all typeS of utilities, those with generation, transmission and distribution as well u utilities which oialy distribute. Non-utility generation includes qualified facilities (QFs), coaeneraton and independent power producen (IPPs). Dispened aeneration sources (DSG's) are a subclass of non-utility generation, usually of smaller capacity and are connected to the system at distribution voltqes. Utilities' transmitldon systems have been desiped primarily to deliver power from their own sources or generation to their custornen with consideration given to economic intercbanae and aeneration reserve sharina. In power pools, power broker arranpments and where interchanae tramactiou are arran1ed, the transmission Q1te1D1 are med to provide wheelina. "Wheelina between systems is accomplished by increllin& pneration in the sellina system and simultaneously decreasing it in the purchuilla system. The term -Wheelina bu had many definitions. In this report the def"wtion adopted is that aiven in the glossary appended to a recent report issued by the National Rqulatory Research Institute [ 110). -7-1440
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Power Tecbaoloal, lac. "WJaMlip The use of the tn1nsmiaion facilities of one system to transmit power of and for 1110ther entity or entities. With this deilnition wbeelina ia another word for tnnsmmon, differentiated from it by tbe introduction of more tbaa one entity. ID the current discussions over b'alllmission access a variety of definitions of subclases of wbeelina have been used. For the purposes of this report, these are aeneralized a: T:r!m!t wbcflips Tbe wbeelina of power and energy for delivery to a utility system. "BAH wbteJip The wbeelina of power for delivery to a retail C1llt0mer9. n...e def"lllitiom illdade ailtiDa or potential arranaements for the transmission of power pnerated by a utility or aoa-utility pnerator to a local or remote utility (wholesale wbeelina) 111d tbe tnnsmktic>I\ of power from a remote utility, or a non utility paentor, reprdlea of location to a retail customer (retail wbeelina.) The distinctiom do af'f'ect tbe technical f acton involved since retail wheeling would effectively remove the load from tbe local utility's service territory and the scheduled power tl'llllf'erred would become part of the scheduled net interchange used in the local utility's AGC system. The growth of utility-to-utility wbeelina, the prospect of mandated wheelina, and the iacreae in the non-utility aeneration sources plus the movement towards increased transmission access all pose a number of technical problems for the electric: utilities. This chapter will discuss these technical problem areas and their relation to the current industry pnctices. The extension to consideration of specuJC f onm of industry restructurilla is taken up in the OT A report, -Yeclmoloaical Considerations in Proposed Scenarios for lncreasina Competition in the Electric Utility lndustry9 [113]. -7-2-
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Power Tecluloloalel, lac. Molt wbeeliq arraqementl under the current industry structure are made between -tially DOD-competina utilities. Tbe wbeelill1 of QF 1eneration under PURP A prOYilioal ii die major ucepdon. There is cooperation hetween utilities to sapport the opentiDa intepity of the intercouectiom, to minimize inadvertent bden:twnp and to allow IICh utility die opportunity to make the most economic arnnpnmts poaible. The current AGC desips and NERC operatina 1wdelines reflect dlil cooperation. The introduction of mandatory wbeelilla requirements and c:ompetiq aoa-utility pneration resources complicates these voluntary arranaements. Competitioa betwND utilities may make this voluntary, mutual support less attnctive from a local utility's economic viewpoint, but it does not remove the tecbninll requirements to control the frequency by blancin1 the 1eneration and denwnd. Tbe indatry Ila llwys bad some non-utility pneration connected to the various DetWorb. 1'lllle included indatrial copneraton who have made arrangements to 1111 ac111 power to tbe local utility IDd indllltrial rums which bad internal _... plants to noply tbeir own loldl. With the ellei"IY criles of the early .-S mid 1970'1 tbere wen ldditioml independent pneration sources developed to me .-wable ...,,, resources for both If-me and sale to the local system. The paa .. or PURPA ia 1971 peady accelerated the arowth of non-utility 1eneration. PURPA nqaires tbe local utilities to purcbae the excess output of coaeneraton and tbe output of qaalifyiq facilitiel at tbe utility's avoided com and to wheel this power to intercolllllCted utilities if it cumot be ablorbed locally. Tbe early c:opneratOn of any comequeace on utility systems were mostly large cbemicaJ plants, oil i-ef"meries or food procmina industries; industries with large Tbe 1eneraton imtalled were automatic iteam eztraction 1111.itl when proc:ea steam ii drawn from the turbine at the proper temperatare and preame for the indmtrial process. The plants were, and are normally operated ia parallel with the local utility system and the industrial plant operaton ad utility system operaton cooperated in the schedulin1 of the copnerated power feed into the utility system. The type of aenerator used (i.e., automatic stear:1 extraction units) allows tbe control of the electrical output over a wide ran1e for a aiven steam demand. Therefore the steam demand cycle does not -7-3-
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PowwTKllaolopal,lac. dictate the electrical output or the 1enerator completely and the units are dilpatcbllble by the System operaton. More recent coaeneration plants have used combiDed cycJe pmntorS where the steam is 1enerated usiD1 the exhaust from the combustion turbine (114). ID this type or copneration plant the electrical output is much more closely coupled to the demaDd for process steam. This is an essential difference and aa importut factor when consideriD1 the impact or new coaeneration on utility system operatiom since the electrical input to the local utility by a coaenentor usiDa a combined cycle plant will be dictated primarily by the demand c:ycJe for procea steam and not the system's load demand cycle and marginal operatiqC0111. ID small amoUldl, or with a few predictable Iara plants, non-utility aeneration does not ...,.Uy caw major, 111110lvable teclmical problems for the local utility. SmtlJer Cacilitiel, particuJuly dispened sources or aeneration connected to the distribution system, will require more eapneerina UlistaDce Crom the utility to eDllll'I proper ad llf'e opentiom. Laqer Cacilities, particularly non-dispatchable saeraaoa blocb, may teJld to tu the utility's capabilities (or absorbina the power IDd cleliveriq it to the loldl. But a Iona a there are only a few such laraer resolll'Cel on a pvea system,. the utility and non-utility 1eneration imns' enaineerinl staffs an maally able to develop mutually satisfactory means for bndJina the laqer amounts or power. A large increase in the number or both small and laqe non-utility aeneraton causes an increase in the technical problems for the utility since the amount or aon-dispatcbable power may seriously upset the normal schedulina or utility aeneration and thus restrict the capability to transmit power ror normal UICI ,neqency purposes. 7.l WDlllNG There are various forms that wheelina arranaements take under the present industry structure [29,115]. The most common application of the term involves the trammission or eneray between two utility systems throuah the network or a third. This type or interchaDae is illustrated on Fiaure 7. I where utility A is sellina I 000 MW to C and the intervenina system, B, is proviclina the wheelina. In this transfer the seller will increase his aeneration by 1000 MW and the purchaser will decrease ,, -7-4-
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Power Tecbaoloal, lac. aeaeration by the same amount. The power will be transmitted through the network owned by B. Both loop flows and transmission system iosses are ignored. Note that the wheelina system's (i.e., B) scheduled net interchange is unchanged by the wbeeliD& transaction so total 1eneration dispatched in B is for the same total demand that was prior to the transaction. The amount of wheeled power is usually f"lUCI for a specified time period so the contribution of the wheeling transaction to inadvertent interchange is minimal 100OMW 1000 MW Flpn 7 .1 Ulutndoa of later-Udllty Wheella1 WC The interchange aareement may take a variety of f onns. System B may provide tnnmiaic,11 ser.rice to A. Alternatively, the same result can be obtained by having two separate and simultaneous buy-sell transactions: 1. A sells I 000 MW to B 2. C purchases I 000 MW from B. Broadly speaking, the results from a technical viewpoint are identical, 1000 MW flows from A to C via the network of system B. It bas been common in the industry to refer to the iust arrangement where transmission service is sold as wheelin1. The second type of transaction is usually referred to as "displacement". This report will not make that distinction. It is of coune important in matters involvina transmission losses, VAR support for voltage control, rates, and wheeling charaes, Under the f"ust arnnaement it is fairly common that the seller provides the power which may be required to supply the added transmission losses in the wheeling system, B, due to the transfer. The purchasing system then receives the amount it () : -7-5-
PAGE 455
Power Techaoloala, he. contracted for. The wheelina system may have to alter its aeneration pattern and schedule of VAR resources in order to accommodate the wheelina transaction, so operatin1 cost rates in the wheelin1 system, B, may cbanae u a result of the tramaction. The wheeling transaction may increase or decrease the net power flows on the wheeler's transmission circuits. Power flows are characterized by both a magnitude and direction. AD example of the potential effects of simultaneous power flows was shown in the previous illustration of loop flows. Wheelinl u defined here can involve only two parties under some circumstances. Take the case illustrated on Fiaure 7.2. There are two utilities involved that own a major plant jointly which is located in system B. When A, the co-owner of the plant, schedules generation from the plant, system B is wheeling the power to A. Another two party transaction that fits the wheeling definition adopted is that where a utility system transmits the power produced by a non-utility generator located in its service territory for delivery to the local utility's customers. This is wholesale wbeelina. Wholesale wbeelin1 of non-utility aeneration by the local utility for delivery to an interconnected utility involves three parties. The wheeling deimition also encompasses the transmission of power and eneray to another vurchasina utility located within the boundaries of the aeoaraphic service area of a utility co meet the total or partial requirements of the load demand of the purchasin1 system. This is another common two party wheelin1 example. It is common to refer to thic II a sale to a partial requirements customer, but it actually involves wholesale wheelin1 under the previous definition. F11ure 7 .2 Illu1tratloa of Wb11lla1 of Power from a Jolatly Owaed Ualt _,_,_ ,1 1 ... l'
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Power Tecbaoloal11, lac. The proposed retail wheeling arrangements that are being discussed currently involve the transmission of power to a retail customer where the power source is not the local utility, but another utility or a non-utility generator located within, or outside of, the local utility system. (This is sometimes referred to as customer wheelina instead or retail wheelina.) Wheeling normally involves the utility's bulk power systems but some smaller non utility aeneraton may be directly connected to the distribution system. The connection of the DSG's to the distribution system involves a different class of technical problems and solutions than those due to the taraer non-utility aeneraton. These problems tend to be JocaJized because of the distribution systems' confiauration and the smaller capacity of the individual aeneraton. 7 .2.1 Tecbalcal Coulderadou la Wbeella1 Wbeelina tnmactiom af'f ect the utility in several technical and economic areas. These include: o the d11ttermination of the wheelin1 capability, o transmission system VAR requirements and losses, and o system operation and pJ1nnin1. DnD ct11ltllltJ 114 Itcblql-la0Ac IUtcta When a utility dispatcher decides to undertake a wheelin1 transaction, he must determine tl!e capacity available for the added transmission nows. Power nows are computed by use of cliaital computer IOld now programs that compute the bus voltqes, VAR requinments ud pow and VAR nows in the network r or a fixed confiauration of aeneration, load demands, and intercbanae schedule. The proaram contains data describina the electrical parameten of the network and information about conditiom on interconnected systemS. The results of the computation teJI the enameen and operaton the impact or new confiaurations. The system operaton may carry this a step further and use extended venions of these models to teJI them what miaht happen under wont cue contJnaencies and in some instaJlations, -7-7-,. ,. (. '' ..11 -~ J
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Power Techaoloaln, lac. how to reschedule the generation to avoid the possibility of cascading failures (see the discussion in Chapter 3. Section 3.4.) The decision to undertake any given wheeling transaction depends upon the current and expected conditions of the system. Wheeling arrangements may be made for as short u an hour or for very long periods. The capacity available on the transmission system for wheeling is not a fixed quantity but depends on the network status. distribution and level of load, generation dispatch, and other intercbana currendy scheduled. If, for example, a proposed wheelina arrangement would tend to exceed available transmission capacity under one generation dispatch patte1' the system operator may be able to accommodate the new transaction by shiftina aeneration. This would involve an economic penalty in the form of an increue in generation production costs. The operator must then balance the gains from whatever revenues tbe wbeelina will aenerate apinst the added costs. When utilitiel are involved in wbeelina. the effects of simultaneous transfen must be recopir.ed to determine the tramf er capability limits. Because of power flow. division and loop flows the available transfer capacity between any two areas dependl on other tnmf en cakina place. These capabilities are studied by utility en&ineen Illini load flow PfOll'IIDI to consider the allowable boundaries of tramf'en. The results are frequendy displayed usina a transfer capability polygon diagram. Figure 7 .3 is the three area example of a transfer capability polygon used in Chapter 3 (40). It is repeated here because of its relevance to wheeling and the transmission capability available r or wheelina. The diagram shows how much power system X can transmit to system Y, considerina the simultaneous transfen from X to Z. For instance. the Y to X transfer capability is 6200 MW when X to Z transfer is 5200 MW. On the other band, if the transfen are in the opposite direction. with Z transmittina 2600 MW to X, X can only transmit 1300 MW to Y. Three such diagrams are required to completely represent transfer capabilities for a three area (X, Y, and Z) system. Each diagram is valid for a specific operating ('\ -7-1-
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Power Techaoloales, lac. condition (i.e., load and generation schedule) and an established reliability criteria (i.e., sinate or double contingencies.) X IMPORTS 0 ., S000 >e 4000 .. 3000 1000 1000 1000 3000 X EXPORTS Flpn 7.3 Tnuf er Capability Polno Exaaple for 3 Anu (Soarce: EPRI IL-3.c25) (.COi y System operaton know approximately how much these polyaom chanae under diCCereat operating conditions, ud control the system accordinaly. Utility power systmm enpneen do not qree univerally on how much power a network can tl'IDIIDit reliably under specific conditions. The state of the art is such that determinina this requires fairly complex studies and application of en1ineerin1 judpnenL _,_,_ r 1 .1 u ... .i. (1
PAGE 459
Power Technoloales, lac. If wheelina and transmission access increase (and particularly if utilities become more competitive and the incidence of retail wheeling arows), it will be important to measure a network's transfer capability in tlte short-term to schedule wheeling transactions. Bu yen and sellen will need to know that they are bel 111 treated on a non-CllSCriminatory basis and a utility providing wheeling services may have to demonstrate the equity of various opentina decisions. New methods of analysis will have to be developed to do this. Thue current methods are an ac:cunte reflection of system engineen' concerns over system reliability and security. The utility engineen develop these limitations in coopentive studies and fully undentand the techniques and implications of the results. The techniques are quite involved, however, and it may prove difficult to carry these procedures into an industry that has been restructured. The engineerina judaements that form the basis for these techniques are inherently subjective and in the future the non-specialist may question the fairness and objectivity of these methods. There is no simple IDaloay to the telephone system's "busy sianal" on a power transmiaion network. Tbe capability to wheel additional power on a system's trammiaion network is a function of the existina and expected nows, the pattern of load and aenention on the system, the voltage prof"Jle and VAR support status, the reliability-security criteria used in determinin& the system schedule, and need for tnnsmiaion system reserv. Loop nows and actions taken by the openton or interconnected systems influence the available transmission capability. A system may well have the thermal capacity for carryina additional tnnsmission nows, but these incremental nows may jeopardize the system's security and utilize capacity needed to serve the system's own local load areas. The additional wheeling power to be scheduled, may cause loop nows on interconnected systems which use the capacity needed by these other systems to serve their own loads and the interchanae trlDSICtions takina place simultaneously on other parts or the interconnection. -7-10/I ,1.19
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Power Tecbaoloales, lac. On the other band. an incremental wheelina transaction may very well reduce the transmission system loading, release additional transmission capacity. improve the voltqe prof"lle and even reduce the wheeling system's operatina cost rate. Wheelina large blocks of power may also increase the operating costs of the wheelina utility by requirina additional aeneration to be placed online as spinning reserve. The sellina system's input to the wheeling system looks like another large aeneration source. The NERC auidelines call for each area to supply its own spiDDina reaerve requirements. but local conditions may dictate that the wheelina system needs to increae its spiDDina reserve in order to survive the sudden loss of the seller's input. There is also no direct analoay in the electric power system to the telephone system's capability to switch traffic directly from a conaested line to circuits with available capacity. When an electric power network is loaded to capacity. the rema,Hi meuures available to the operatOn to reduce the network loadina on specif"'JC circuits are indirect, involvina cbanaina the aeneration pattern and possibly switcbina circuits to redirect nows where possible. Power systems may eventually bave this control capability tbrou&h the application of hiah power, high voltaae electronic switcbina devices. That, however, is in the future. Centrally dispatched power pools incorporate a special subclas of wbeelina. ID tbele pooll wbeelina taka pltee u a matter of rqular operation where the more efficient, lea cosdy aeneration resources are scheduled to supply loads throuahout the pool ID these pools the arrangements are usually such that transmission cbaraes, if' any, are bued on some agreed upon formula that essentially amounts to a rental chaqe paid by the other pool memben to the owners of the major tninsmiaion facilities. Schedules are determined by the pool control center based on minimizina the operatina costs to the pool members taken u a whole. without reprd to trammisaion circuit ownership considerations. I -7-11-
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Power Techaoloaln, lac. Inwuo 5ntc YAB Bu11nmc1ta 114 LQIHI Wheelina flows may add or subtnct to the power flows on major circuits. Where they increase the flows they will increase the power losses on the line and usually increue the VAR supply requirements. Apin, the latter is not always the case. Recall the concept of natural, or surae impedance, loadina in an earlier section. When the power flow on a line equals its SD.. rating, the VAR supply requirements are zero. lncr.sina the flow on a line ori&inally below its SIL level may decrease the VAR requirements. Some wheelina ttansaction arranaements require the seller and possibly the purchasing utility to participate in the fumishina of the added voltqe support. Transmission losses on a aiven line will increase approximately in proportion to the square of the power flow. Fiaure 7.4 shows typical transmission line losses u a function of the power flow for a 100 mile Iona 345 kV circuit. A moderate increase in power flow may cause a disproportionate iDcreue in power losses. When more than one tranlletion is flowina on a aiven line in the same direction, it is a straiptf'orward eqineerina computation to determine the total transmission loa. It is a matter of mutual qreement, however, to allocate the responsibmry for the increased loaes amonpt the various flows. It is a common practice to allocate these 1oaes bued on the chronoloaical order that the transactions were established. The immecUate COit of loaes to the wheelina utility is due to the increue in costs to supply tbe 'lllll'IY losses that accompany the power loss in the transmission line. Thenfore the laadina pattern (i.e., the load cycle pattern) of the transmission line flow is also important. In systems that have extenc:led tna1mi11ion systems, incremental transmission system losses may cause shifts in the economic dispatch of the aeneration. Enaineen have developed techniques to take the effects of loaes into account when developina an economic dispatch. These methods may involve the development of what is known u a "loss formula that relates the transmission losses to the power aeneration and the interchanae power flows scheduled. The same purpose may be accomplished -7-12(' 1,... ... j ... u.
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Power Tecllaoloales, lac. usina optimal load flow" models which is a schedulin& proaram that includes the power network relationships IS a set of constraints. In an economic dispatch includina losses, the marginal cost of power is not identical throupout the system. Rather, the system aeneration is balanced such that an incremental iDcreae in aeneration anywhere on the system results in the same increase in production cost rate, includina the effects due to the incremental increase in loaes IS well IS the marginal cost of aeneration. Usina these techniques, the marginal cost of power may be computed at various points in the network. These methods may be med to compute the marginal cost changes at various poin11 in the network due to incremental power nows caused by wheeling transactions. Some utilities use these methods to develop the incremental cost of power at various delivery points in the network when these deliveries are involved in I wbeelinl trallllCtion. 30 25 3 s 20 ,,; Ill en en 15 g Ill z ::J 10 5 0 LOADING,MW Flpn 7.4 Real Power LOINI for Varlou Power Flows oa a Typical 100 Mlle Loaa, ]4t5 kV Traumluloa Chait r r -7-13-
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Power Techaoloales, lac. Ef(ccts of WhceD11 01 5utcw Opcrat101 114 "'''''' Wheelina arranaements aenerally do not cause operating difficulties as long as there are a modest number of simultaneous transactions. These interchanges will be bandied by the eneray control center in the normal scheduling of the system's own generation. Utility AGC systems are desiped to be operated with scheduled net interchange data supplied by the operaton and actual interchange flows monitored on the system and transmitted to the AGC system. The problem of allocatina tbe traosmiait)n network is actually part of a Iaraer problem. Scbedulina aeneration (includina maintenance), purchases, and sales needs to recopia the wheelina trumction options and effects, and vice versa. Today's economic dispatch techniques and prc,arams work quite well, but they generally assume that tbe instantaneous optimization of generation leads to a generation pattern that is optimal over a month or a year. Utilities that face hydro or fuel constraillts optimize scbedulel over a time horimn. Schedulina wheeling tralllletiom, which can be short an hour or u Iona several years, require optiminti,on throup time. Power system enaineen will need to develop practical methods for optimizina this schedulina of aeneration and whaelina. An increase in sheer volume of wbeelina traDSICtions and widespread transmission access will aupaent tecb.nic:al problems in other areas. If the number of non-utility aeneraton' supplien increaes, if they are to be intearated into the AGC system, the telemetry into the utility control center will need to handle more distinct aeneraton. This is not a theoretical Y,!Obhun, but. every control center computer and communications system ha limits 011 the amount of data it can handle. This may require the earlier replacement of the existing control center facilities. If there are many wheeling transactions, especially wheeling transactions whose levels chanae frequendy, the wheelina utility may have to train and add more penonnel just to handle the intercbanae rescheduling. This has already happened to at least one utility in the United States, Houston Lighting and Power, which has bad to add an eneray scheduler to the dispatch staff. That utility estimates that over one-half his time is dedicated to handling the effects of cogeneration on -7-1.C-
PAGE 464
Power TecbaoloSI, lac. system operations. The utility anticipates stafrm1 about five additional people in the future to accomplish this function for all shifts. With the --may be able to increase its capacity to wheel by relaxina tbe security criteria used to schedule the system. This is not a matter to be undertaken lipdy, however, since reducin1 the preset practices may iDcreae the incidence of ca1CWdin1 outaa, system sepaiatiom, and blackouts. This method for iDcreuin& wheelina capacity ii also highly system specific. Each utility or area needs to consider the probable effects of a relaxation of security criteria. One sqaested alternative is to substitute automatic corrective action after a continaency ha occurred. For eumple, a aenerator that mi1ht have to reduce its output llllder security dispatch could be allowed to remain at its economically determ.iDed output level until such time a specified contin1ency (or set of contiDpncies) occurred. The openill1 of a key line, for example, miaht be the automatic reduction of the plant's output level Aaotber alternative that requires further research is to base operatin1 security criteria on a probabilistic 111111ment of the consequences of application of various criteria. This would theoretically allow the development of operatina security criteria baed on a quantitative reliability standard rather than on the bais of the wont cue philolophy curnndy used. DirrJCUltiel in operation may arise if tbe number of wheelina transactions becomes laqe 111d if the nows deviate from those scheduled. With unpredictable trantmiaion flows the AGC system will not have the correct data needed to discriminate between internal and external 1eneration-demand mismatches. Generaton may be required to increase their participation in reaulation causing increued maintenance costl to the utility and increued levels of inadvertent intercbanae. T" liDel may become overloaded and tripped automatically. The trullletion COits of wheelin1 utility include the costs of monitoring the power nows, commllllicatin1 these data to the control center, and preparing billin1 data for the tramactions. Control center costs also involve stafimg and computer costs for dilpatchin1 wheelin1 transactions. These costs are aenerally fairly low for -7-15-
PAGE 465
Power TeclaaoloSles, lac. normal inter-utility wheeling (i.e., wholesale wheeling), but will increase when the number of tramactions and non-utility aeneraton involved increases. The widespread introduction of retail wheelina would increase the transactions costs still further. A Jarae and unforeseen increase in wbeelina transactions may also cause problems in the exJ)llnion plannin1 of tbe entire system, but particularly the plannina for the transmission system. If the demand for wheelina service is sustained and appean to be pan of a loq term powth pattern, system plannen can take these added demands on tbe network into account when plaaaina for system arowth. If the wbeelina requirements fluctuate and are cbancterized by a hiah dearee of uncertainty, tbe pltnniaa engineers face a more difficult task. Part of their problem will be (and ii in some systemt now) the requirement to provide this trwD11Ditliotl aervic:e while still mail'tainina service reliability standards in supplyina tbe system' load. With sbortqel of tnmadssi'>n capacity there will have to be some form of ratimlina impoeed by contract, price, auction p~esses. or direct control JNIN Bef on new facilities an constructecl to handle the expected needs for iDc:reased wbeelina tr'IDl1DWW'l service, the staae will need to be set so that proper economic choices may be made by tbe utilities constructina these facilities. This ii u area outside of tbe immediate scope of this report, but it impinges upon the plannina enaineerin1 required to expand the network if, in fact, there is expected to be a need for these facilities. In this reprd _there is a areat deal or uncertainty today amongst utility plannen concern.ins the mqn..itude, timina and reality of future non-utility aeneration sources. This uncertainty affects traasmission plannina u well since the non-utility aeneration must be transmitted (i.e., wheeling by the local system.) This same cycle may well be repeated because of the poasibility of incni.ued transmission acceu by non-utility parties, inter-utility competition and the possibility of expanded mandatory wholesale and retail wheelina. r @-16-l
PAGE 466
Power Teclaaoloal, lac. 7.3 NON-UTILITY GENERATION Non-utility pneration includes coaeneraton, qualified facilities in the sense that PURPA uses, small power producen, independent power producen (IPPs) and distributed aeneration 10urces (DSG's). That is, it includes all generation not under tbe direct control of tbe utility where it is located. The distinction is deliberately made here between ownenhip and control Ownenhip may affect plallning in the utility in that plant size, type and availability may be different from utility owned capacity and tbe service life of a non-utility resource may be highly unpredictable. But the immediate key techDical questions posed by non-utility generation center on tbe control or tbe aeneration. An IPP plant flnanced and owned by a non-utility entity, but operated and controlled by the local utility, would be no different technically than a plant owned by the utility. Generation plants that are operated by electric utilities IUlder sale-leue back f"mancing arrangements would have the same technical implications that tbey would have if they were utility owned. The technical quemom relatina to wbeelina are closely interrelated with the arowth or DOD-Utility pnendon. With the inc:nued interest in DOD-Utility pneratiOD the demand for wbeelina NrVice iDcnaes. Wbeelin1 becomes a key requirement for the sua:sful operation of non-utility aeneration unless the non-utility aenerator comtruc1S a transmission system to deliver the power. The techD.ic:al area principally affected by iDcnued non-utility aeneration are: o system plannina, and o system operations. ID addition there are different problems associated witb dispersed aeneration. The teclmical problems mociated with cliapenecl sources of aeneration (DSG's) have received a peat deal of put attention. Thme non-utility aeneraton are connected to the utility system at distribution system voltqes and result in a different set of teclmical problems than the hiper capacity coaeneraton and proposed IPP plants. r -7-17-
PAGE 467
Power Tecbaoloales, lac. The technical issues posed by the arowth of DSG's are summarizeti below in Subsection 7.3.3. 7.3.1 Errecu oa Utility System Plualaa One majo~ effect that non-utility aeneration has on planning is caused by the great uncertainty that accompanies the arowth of non-utilicy aeneration. Since 1978 and the passaae of PURPA a tarae amount of non-utility aeneration capacity has been proposed. As fuel prices declined in the l 980's, a lot of this announced car,acity has evaporate<:! u utility operatina costs and therefore avoided cost" levels declined, reducina the potential economic rewards for construction of new nonutility aeneration. This uncertainty continues. For example, according to their annual reports in 1986 Southern California Edison Company had contracts for about 3900 MW of non-utility aeneration. They published estimates that only 60% of this capacity would materialize. In 1987 3500 MW wu still under contract, but the Company expected that only 1400 MW would actually be constructed. Situations like this make it difficult to plan the needed utility facilities to supply the transmission and aeneration needs or the area. As another example, Fiaure 7 .5 shows the published forecasts of non-utility aeneration issued by the WSCC reaion of NERC [ 116). The data show the forecasts r or the total aeneration expected to be in service in 1992, by year when the forecast wu published, and the year-to-year variation in the forecast. The uncertainty is obviously quite larae and presents an extremely difficult forecasting situation or plannina staffs or the utilities. It requires several yean of lead time to construct new traDSmiaion and aeneration facilities. If the non-utility aeneration actually does appear on the system, new transmissicn facilitin may be required and the utility's own aeneration plam may be postponed. If the utility system construction is based on the early forecasts and the non-utility 1eneratin1 capacity actually does not appear, the utility may have transmission capacity that will not be fully required and face a potential 1eneration shGrtaae. On the other hand, if the plannina enaineen wait to see wha, non-utility aeneration is actually -7-11-
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Power Tecbaoloalu, lac. constructed, there may not be sufficient transmission capacity available to provide service to the new non-utility resource. wscc cogeneratlon + OtherCapablllty Five Consecutive Forecasts for 1992 8----------------------, .;; C ca en :::, 0 .c t:. en 7 6 5 4 3 = 2 ca I 1 fll 0-t---===:::;::::_...=-----------,, -1 -2--+-------..-----------~-------1 1983. 1984 1985 Year of Forecast 0 Forecast Capablllty 1986 1987 + Change In Forecast Flaan 7~ Foncutl of Noa-Udllty Geaeradoa la WSCC. Upper Cunt ls total capacity foncut. Lower 11 year-to-year ,artatloa o the foncut. Under today's conditions of high utility generation construction costs, moderate to high levels of generation installed reserves and high levels of interchange, it is likely that the construction of excess transmission capacity would be preferable, from the utility's viewpoint, over the construction of new utility owned generation facilities because of the difference in relative investment required and the added operatina flexibility that may be obtained with the excess transmission capacity. The extra transmission may support increased economy and emergency interchanae levels in the future ud, if necessary, allow time for the construction of new utility aeneration. The utilities constructing this excess tran1mission run the risk that it may subsequently be viewed by regulatory agencies u not required and removed from th" investment base allowed for purposes of earnings and rate regulation. -7-19,..
PAGE 469
Power Tecbaoloaln, lac. The potential effects of the uncertainty of actual future existence of the non utility generation can be recognized in utility generation planning using probabilistic based reserve requirement planning techniques (i.e., the loss of load, or energy, probability methods). As a hypothetical example consider a system with a 2000 MW peak load. With its present generation mix and generation unavailability experience, the planning enaineen calculate a loss of load probability of 1.27 days per year for a aeneration reserve level of 20% of the expected peak load using their generation reserve calculation methods based on loss of load probabilistics. Two alternatives are considered, (I) addina a 300 MW utility unit with a I 0% unavailability or (2) by the utility plannen addina four 75 MW non-utility generaton which may be constructed. These are each expected to have an unavailability rate of 10%. At the time the plannina takes place there is only a 50% probability that they will be constructed. The reliability assessments of these two alternatives using loss of load probability methods shows that the additional 300 MW of utility capacity will support a 214 MW growth in peak load at the present reliability level, while the four 75 MW non utility Jeneraton will allow only a load growth of 107 MW with the same expected generation system reliability. To achieve essentially the same load carrying capacity at the existing calculated reliability level would require about s~.en 75 MW non utility 1eneraton assuming the similar accepted, unavailability forecasts. The differences are due solely to the cliff erences in the expected availability of the future capacities caused by the current belief that there is only a 50% probability that the non-utility generation will be constructed. These are, of coune, plannin1 data based upon current perceptions of the future. But they illustrate the utility 1eneration plannen' dilemma. With current experience based on the actual realization of non-utility generation, overall future generation reserve requirements increase in order to bold current, generation reliability levels. The effect is due entirely to the expectation that half of the announced (i.e., planned) non-utility 1eneration will not be constructed. r -7-20-,1 0 .. ,.,... ''
PAGE 470
Power Tecbaolo1les, lac. If the utility proceeds with its own construction plans for the 300 MW unit and the non-utility 1eneration is constructed, the installed reserve levels may be uneconomic. What appean to be required is some procedure similar to the current biddin1 system for non-utility 1eneration used in some states to secure new capacity coupled with a system for ensuring that accepted bids are actually carried out. Another planning uncertainty caused by the growth of non-utility generation has to do with the longevity of these plants. For example, cogenerators are tied to the need for process steam which in tum is tied to the market place for the particular product bein1 manufactured. Utility planning engineering determinations are generally based on the expectation that 1eneration plants will have averaae service lives of 30 yean or so. A coaeneration plant may disappear from the scene just as rapidly u it appeared. If the local utility bas counted on this as a dependable resource and it vanishes, they may be forced to make an expensive substitution. The potential effects of this particular uncertainty are in the same order of magnitude u that which the utility faces with major industrial customers. The lonaevity of these ill'IDS and the requirements for servin1 their loads are just as volatile u the aeneration supply of the co1eneraton. The essential difference between these situations is that if a major industrial customer leaves the system, the utility is left with an excess capacity as well as a loss of revenue. If an industrial cogenerator leaves the system, the utility may be left with a shortaae of generation capacity that will have to be made up by purchases, the advancement of the next plant to be constructed, or the construction of a gas turbine plant. Non-utility generators may benefit technically from careful cooperation and coordination with the local utility engineering staff. The early notification of the intent to brina a new facility online will allow the combined engineering coordination required to achieve the lowest cost solutions to specific, local technical problems and the development of joint operatina practices and installations to protect both the utility fadlities and the aeneration in the new plant. Studies should be made of circui: breaker short circuit duty requirements, protective systems for the new plant, and operatina procedures in case of system or non utility generator emeraencies. Arranaements for backup supplies and emersency -7-21-r. ,.
PAGE 471
Power Techaoloales, lac. supplies should be established appropriate to the specific situation. An industrial cogenerator or IPP may have the capability of supplying V ARs for voltage support at weak points in the network. 7.3.2 Erreca oa System Opentloa1 The effects on utility system operations of non-utility generation depend upon the number, relative sizes, locations, and dispatchability of the facilitiei. A large number of small sources located near load centers could unload the transmission network, easing the scheduling problems. Smaller facilities such as wind generators would probably be uncontrolled resources insofar as scheduling the utility generation is concerned and are usually connected to the system at distribution voltage levels. As long as the total generating capacity of these uncontrolled sources is relatively small (e.g., less than 3 to 4%) with respect to total demand, these would pose no more of a regulation problem than that faced now by the utility in the uncertainties associated with forecasting load. Certainly the variability and uncertainty of these resources would add to the total uncertainty faced by system operators so that levels of spinning reserve might need to be increased. In some systems where non-dispatchable DSGs are connected to the distribution system, the system operaton may treat these resources as load reductions. Large cogenerating plants, plants burning collected refuse, and plants burning waste products generated by an industrial firm, may have to be operated to serve the demand for steam and the need to consume required amounts of refuse, wood chips etc., on a given time schedule. As such, their electrical outputs may follow a different cyclical pattern than that of the system load demand. This would require the system operaton to consider these plants as must run units in dispatching the system. If wheelin1 is required to deliver the output to utility load centers, this would also have to be taken into account. The utility may be providing backup service in case of a :01enerator plant outage so that the utility system operators will tben need to increase the available spinning reserve levels to accommodate the possibility of a sudden plant outage. This increases load uncertainty effects in system operation. ,. .. -7-12-
PAGE 472
Power Techaolo1le1, lac. The dearee of dispatchability and interruptability of the larger capacity. non-utility generaton may seriously affect the economic schedulina of the utility's own generaton. The utility's own dispatch must be adjusted to accommodate this power delivery, requiring that the non-utility generation be monitored and the dat!l transmitted to the utility control center. The amount of difficulty this may cause and tJ e resulting increase in utility generation operating costs depends, to a great extent on the amount of non-utility generation relative to the system demands. lie liaht load periods may cause particularlv severe operating problems to the utility if the amount of non dispatchable non-utility aeneration capacity online approaches the level where it represents a substantial fraction of the minimum system load level. These light load period load levels vary from system to system and are usually in the order of 30% to SO% of the daily peak load. They occur in U.S. systems generally in the early morning houn between midniaht and 6:00 Lm. The reasons for the scheduling problems during light load periods are related to the utility's generation mix and the operating characteristics of various types of large steam turbine generaton. Many utilities have installed laraer. base loaded steam turbine units with reheat cycles, some incorporating supercritical steam conditions. Most of these units are very efficient and very few of them are desianed to be operated in a cycling mode where they supply varyina outputs, or for two shift operation where they are taken off line for the light load period of the day. Most of the modern, laraer size steam turbine aenerator units are not designed to be operated below output levels of 25% to as much as 40% of their maximum capacities. The utility must operate sufficient capacity to provide the required regulation and to guard against sudden capacity shortaaes, even during light load periods. Therefore, with a larae amount of non-utility aeneration being delivered to the system during light load periods, the system operaton must devise unit commitment patterns and economic dispatch schedules which allow them to satisfy all of the system requirements and unit constraints. .1 r., r; ... ...; I.. -7-23-
PAGE 473
Power Techaoloaln, lac. If tt\e system is operated without capacity sufficient for the adequate control of frequency and voltaae, inadvenent interchanae levels will increase and voltage levels may aet out of their normal ranaes. In an extreme situation of this type it is quite possible that the system may be isolated by its interconnected n~ighbors and even be forced to shut down due to under and over frequency relaying systems. When non-dispatcbable non-utility resources approach 25% to 75% of minimum load demands, the system operators may have to cycle their most efficient plants off for several days at a time to avoid undue thermal cycling of the units and run smaller, less efficient plants to provide the utility capacity needed to supply loads, control irequency and voltaae levels and handle emergencies. The schedules that are f eas;ble may be far from the most economic to satisfy the load since smaller units, capable of providina the required regulation and capable of two shift operation, will have to be run. There are several technical and economic (or contractual) methods to alleviate the problem. One is to nquin a certain amount of utility control over the dispa!ch and operation of the non-utility aeneration, incorporating mutually satisfactory terms in the aareement between the utility and the non-utility entities. If a large per cent of the utility generation is in units that cannot be cycled to low enough output levels or shut down overniaht, the machines may have to be modified to permit this type of operation. This is feasible in some type;; of steam units but is usually expensive. It is not considered to be feasible for nuclear units operated by U.S. utilities. Small amounts of non-utility generation may be considered to be load reductions by the utility d.ispatchen. Larger, non-d.ispatchable units will be treated as must-run capacity. Utility operaton would prefer to have all larger non-utility aeneration dispatchable, and in fact with proper contractual terms, this may be best for some non-utility operaton u well. The dispatch of non-utility aeneration miaht be based on fixed or time differentiated prices for the non-utility eneray or the utility's and non-utility generaton' marginal operatina costs. If the utility is required to modify existina plants to provide the proper type of light load capacity, questions -7-24-,. 1 ... ,' I -1 .. "'"''
PAGE 474
Power Tecbaolo1ln, lac. concernin1 the responsibility r or the expenses are certain to enter into any a1reements for payments for the non-utility 1eneration. Non-utility aeneraton may be located on the system at points where poor volta1e control exists. It may be necessary for the utility t'> require that power factor excitation control systems be installed on the 1enerator to avoid local high voltages or to allow unmanned operation of the generation. These control systems set the level of VAR 1eneration. ID turn these regulaton may limit the VAR support that a non-utility 1enerator may supply in supporting volta1e limited systems. The utility system operaton and plannen must consider the effect of the non utility generaton on system transmission network loadin1 and dynamic problems. In particular locations on systems with Iona lines, the non-utility generaton may require the curtailment or reschedulina of utility generator operation to alleviate local transmission bottlenecks caused by wheelin1 requirements. This may remove 1eneraton that would otherwise contribute to system stab:.Uty. Non-utility aeneration that bu a hiahly variable output may contribute to the system's aiea control error, causin1 .sxcessive regulating action by the utility's 1eneration and increasing the inadvertent interchange. This is, or coune, hi1hly dependent on the total MW or this type or generation on the system. A more frequent operatin1 problem is that or coordinating the non-utility generation with the system actions during emergencies. Typically, a non-utility generator will be connected to the utility transmission system at subtransmission or even lower voltage levels. Underfrequency relays are frequently installed to trip the non-utility aeneration when it becomes islanded with utility load. This serves to protect the aenerator from the harmful effects of sustained underfrequency operation and prevents backf eed, the unexpected ener1ization or the system, with its attendant possibility or hiah voltaaes or safety problems. This same underfrequency relating practice, however, trips the non-utility generation when there is an area-wide aeneration shortaae, further increasing the area's total 1eneration shorta1e. To auard a1ainst this, the utility may have to increase its -7-25-
PAGE 475
Power Tecbaolo1lu, lac. spinnin1 reserves. A better practice would be to coordinate the emergency operation of the larger Sl%ed. non-utility aeneration with that of the utilitys own aeneration. Perhaps laraer non-utility aeneraton could be connected to the system at transmission voltaae levels. Area loads in the local district containina the non utility aeneration miabt have their own separate underf requency relayina scheme so that the non-utility aeneration would not be tripped except under certain islanding conditions. Even then it mi1ht be better. in some instances. to leave the non utility aenerator online to nttempt to balance the local load with the non-utility aeneration capability to avoid a complete blackout of the islanded area. Very larae capacity plants that may be owned and operated by an IPP present another. but similar. set of operatina problems. It may well be that the plants output under normal conditions is not subject to regulating duty under the control of the utility operatina center's AGC system. That is, it is supplying power at a iixed level to the system. Certainly the output would be monitored by the control center and arranaements would need to be made concerning the participation of the IPP plant in voltaae support-VAR supply duty. A Iarae IPP plant would undoubtedly be controlled by a capable operatina staff with en1ineerin1 support, and if there is close communication with the utility control center, there should be no unusual demands placed on the utility to provide additional spiDDina reserves. Emeraency operation and plannina will require close coordination and cooperation between a large sized IPP and the local utility. It would seem in everyone's best interests to facilitate this. When the system is shut down for a prolonaed emeraency, the IPP is out of business. The cooperation to avoid emergencies and to restore the system u rapidly u possible after one does occur would maximize the IPP's revenues related to eneray production and improve the overall utility performance. 7 .3.3 Dllb11ned Geaeratloa Sorc The technical literature bu discussed many upects of the arowth of DSG plants on utility system planoina and operation. (See, for example, a recent summary in Reference 117 .) Many technical problem areu of the relatively small sized DSG's -7-26-
PAGE 476
Power Tecbaolo1l11, lac. are due to the combined effects of the operatina characteristics of these plants and the fact that they are usually connected to the utility network at distribution voltqe levels [ 117 -120). Utility distribution systems were not desianed to handle local aenention, but were intended to serve only for the delivery of eneray to retail customen. The voltaae control devices (i.e., automatic voltaae regulaton and switched capaciton) and protective systems (i.e., relays and circuit breaken) on the distribution system were installed to control voltages and protect the system and customer installations usumina power nows from the substations to the retail customen and relatively low short circuit currents under fault conditions. The installation of generation this far out" in the system creates potential situations that were not intended in the oriainal system layouL These DSG plants may use synchronous aeneraton where excitation of the machine is supplied separately. Some may use induction generaton that must be separately excited, either by a VAR supply transmitted from the system or by a separate installation of capaciton to supply the required excitation. The DSG's may contribute to voltaae control problems and the short circuit interruptina duty of the circuit breaken, fuses and circuit cut-outs on the distribution system. Other DSG's such u photovoltaic units aenerate de power that is chanaed to ac with static inverton. These devices may aenerate harmonic currents and voltages that appear on the distribution system. Technical problems that have been cited include: o neutral shift for some typeS of connections of three phase transf ormen, o harmonic voltaae and current generation where static inverton are used to cbanae the de DSG output to ac, o voltaae flicker on the distribution system, o problems due to the reclosina of DSG units after fault removal that may cause damaae to DSG units, o induction aenenton that may self-excite causing voltage problems, o resonant overvoltaae conditions, r -7-27.1,."'R .......
PAGE 477
Power Tecbaoloaln, lac. o lines and transformen loaded to levels beyond their :apacities requirina reconstruction of lines and transformer chanaes. o capaciton installed for power factor correction causina self excitation of aeneraton resultina in voltaae problems on the system, and o safety problem, frequently usociated with backfeedina the system when a load area containina DSG(s) is isolated. The DSG related problem areu are particular to each loc,tion and system. Some will occur with some typeS of distribution system layout and particular DSG plants. Othen may never occur or may occur in unexpected places in the system. These problems normally have satisfactory technical solutions. The utilities have aenerally worked out minimwn standards for the connection of smaller non-utility sources that are not unduly restrictive. Many of these standards will require the DSG owner to install protective systems that are intended to prevent damaae to the DSG u well II minbniu, potential problems with system operation and safety. There does not seem to be uy aeneral movement on the part of electric utilities to prohibit the connection of non-utility aenention u then was in the put when telephone companies initially made it difficult to -connect non-standard (i.e., utility supplied) equipment to the system. Rather, the electric utilities appear to be establishina reasonable standards that will ensure the protection and safe operatina practices of both the DSG plant and the system. 7 .C WHEELING OF NONUTILITY GENERATION The wheelina of non-utility 1eneration may be wholesale wheeling, transmission of the power and caeray to the local utility, or another utility, for ultimate delivery by the utility to retail customen. The local utility must meter the output of the plant ud for Iaraer 1uppli, traDJmit these data to the operatina control ettnter in real time for use ic the utility aenention dispatchiaa ud AGC systems. This increues the number of meteriDa points and data transmission requirements. For wheeliDa to another utility, the intercbanae levels may fluctuate if the non-utility aeneration level is not constant or on a fixed schedule. r, -7-21-
PAGE 478
Power Tecbaoloaln, lac. Fiaures 7.6 and 7.7 illu.~arate the wholesale wheeling situations where a large non utility aenentor, o is deliverina power to the local utility or an interconnected utility. In the f"ant cue on Fiaure 7.6 the aoa-dispatchable aeneration may be comidered u must run capacity by the local system openton. In the second cue shown on Fiaure 7. 7, the wheelin1 tramactioa is treated u a scheduled interchanae tramaction by the operaton or both utility systems. r -------7 I I I 1 e..... 7 I I~ l:: -_J SYSTEM A L. ------.....J Flpn 7 .6 Wllol...a. wbll of P MW, betwHa a aoa-atlllty ,...,.to, G ... die local adllty 1ystea A. Noa-adllty 1eaendoa co..adend u a t-na It for acbedallI A. r--------7 I I I r~7 I I~ I t.=' ...J I IYITIMA I L------...J -------7 IYITIMa I I l,_ ________ _J Flpn 7.7 Wbolaal wbllI of P MW1 betwH a aoa-atlllty 1entor G located I atlllty 111te A ud u latercoaaected atlllty, 111tea 8. Treated u acbedaled latercbu1e by both 111te... Ill tbe scbedulla1 of A It II betwHa tbe 1erator, G, ud system B: la 111te B It II betwN the two utlllty 1yste ... ,... -7-29-
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Power Teclaaoloal, lac. The requirement for wholesale wbeelina may increase or decrease transmission system loadina dependina on the location of the non-utility resourees and the prevailina power now panerm on the system. In some utility systems new non utility aeneration bu been located where the added power nows contribute to the loadina of critical tnn1miait)D circuits or tramf ormen causin1 transmission bottlenecks. This may ratrict the utility's abilities to dispatch the system economically. to carry out economic intercbanae tramactiom, or to import emeraency eneray in cae of area 1bona111. The remedies are not always apparent and have required 1uu11ted schemes for (or the imposition of) some form of ratioDiDa of the available trammiaion capacity. Rate stnactures and time and load dependent wbeelin& rates have been ngested a have auctions of available tnnsmiaion capacity for wbeelina. The Iona run cure for tbeN traumiaion capacity 1hona1e problems is the coDltnletion of new tnmmiaic,n capacity by rebuildina existina circuits or iDl1alJ.iq new circuits. Tblll an relatively expemive remect. and in some localities may prove extremely dilraculL 0De plalmiaa problem tbal arises ii due to the relative lenatbl of the time periods for plalmiaa and coutructina trammiaion ven111 that for buildill1 new non-utility pnention. The perminina, liceuina, land acquisition and comtnlCtion cycle for tr1111million can be quite Iona (e.a several yean). It is usually much lonpr than that required to construct a combined cycle coaeneration plant. for example. IC the utility does not have sufficient lad time, the needed b'lnsmisaion capacity may not be available when tbe coaenerator ii ready to deliver power. The plannina for tbe needed trammiaion facilities needs to be coordinated with the plau for the non-utility aeneration u soon u possible. The real cure for this pr-;',lem ii probably to rand some acceptable means for speedina up the licemina, permhtin1, and construction cycle for new trammiaion. The introduction of ncaillna wbeelln1 of non-utility aeaeration introduces added teclmical compllcatiom. WbeD the aeneration ii to be wheeled to a retail customer. theoretically the pneration-lold combination ii no lonaer put of the utility's area of responsibility for balancina the load and aeaeration. Laraer amounts of non utility aeneration delivered from one plant to a retail customer would have to be monitored at both IOUfCI and delivery points to provide data for the utility AGC ,. -7-30-
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Power Tecllaoloaln, lac. system. Fi1ure 7 .I illustrates this situation. If the aeneration and load demand are not bllnced at all times, the utility's inadvenent interchanae will increase. If the iDcideDc:e or non-utility aenention bein1 wheeled to retail customers increases, cautiD1 ID 11n1cceptable level or illldvenent interchanae, the arr,naements between die putiel may hive to be altered so that tbe utility's AGC system treats the non utility aneration sources IDd the loads beina served u pan of the utility's respomibilitiel IDd it supplies any mismatches that may occur. This may lead to some rorm or nte 1tn1Ct11r1 ror providin1 this needed rqulatina duty that would motivate tbe non-utility 1nerator to install the equivalent of an AGC system for control or ill pneruion. Apia, this ii not an insurmountable technical problem. It does require tblt tbe utility install additional monitorina and data transmission ror tbe pnention control r I I I I I L -------7 f+ ~--; 7 I RETAIL I CUSTOMER L -_j I I I I SYSTEMA I -------___J Plpn 7.1 a.tall wllNUaa of P MW1 NtwNa a o-dllty 1eaerator, G, ... retall catoaer INttll locall4 la die 1UN atlllty area. Treated by .,.... A tlla,atd1 m AGC u I acll ... led latercbu1e betwN G ud tlN .. 1a11 cutwr. U tllen II a almatcll ltltw ... the aoa-adllty 1wnt1oa m retall cuto.., ...... otller latercoaaected 1yate .. will ca It II CMN4' .,..._ A ... tlley will aot be able to dllcrlalaate Ntweft .,..._ A ... die ntall wllNllI wltllla syatea A. TIii special cue wbere non-utility 1eneratioa source wishes to whffl power over tbl utility network to 11rve tbe loldl in I remote racility belon1in1 to the same ""Pnintioll ii no diCfereat from tbe 11neral case or retail wheelina betwffn a non utility ....,ator IDd any otber load ill tbl IUDt utility system. -7-31-r
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Power Techaoloaln, lac. Retail wheeling to a customer located in one utility system from a source located in another system is a different cue, however. In this situation, shown on Figure 7.9, a non-utility source in system A is selling power to a retail customer in system B. The generation is no lonaer a controlled resource of utility system A and the AGC system of system A would treat the wheeling u a scheduled interchange bet9,en system B and the non-utility aenerator, G. The retail customer load in system B is no lonaer a pan of its load responsibility, so that the AGC system in B would treat the wheelina transaction u 5Cheduled interchanae between A and the retail customer. In theory this is straiahtforward. However, if the load and aeneration involved in the retail wheelina trlDIICtion are not balanced at each moment in time, the inadvertent intercbanae levels will rile and the utility systems may be required to perform additional reaulation to control frequency. r-----7 1 I r;:,.7 I~ t.:: _J L-----I I I SYITIMA -_J r I -----7 I I I I L __ [j:;-; 7 I RITA.IL I CUITOMIR L_ :J I I I I I IYITIMI I -_J flpre 7.t Retail wb11ll Ntw ... a odllty 1ntor, G, locatld la ,,..._ A ud a retail cutoaer located I 111te B. For 1elleull ud AGC ,-r,11 111 A tnatl tbll u a sclledaled laterclau11 Ntw ... G ud 171tea 8 ud B tnatl It u u lat1rcbu11 sclledled betw 111te A ud die retail cutoaer. For a fixed 1ntor oatpllt leHI, P, ud a arlaltlt load of tlle retail e111toaer 111t A coatroll wlll ..... tll1 allaatcb II la 111te B. r -7-32-
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Power Techaoloaln, lac. This is a similar situation to the one discussed previously, except that it now becomes evident that some sort of augmented or modified AGC systems will be needed if retail wheeling serves a significant part of the system load. Without the imposition of some fnrm of control on the generation sources and retail customer load demands involved in retail wheeling, the responsibility for load-generation balance becomes less well deimed. The generation source may be delivering a fixed amount of power to a cyclical load. The load is no longer (under the assumptions made for discussion) the responsibility of the local utility, but is the responsibility of the generatina source. If retail wheelina is to take place on any sizable scale, these control matten will have to be settled. Perhaps aareements may be made such that the local utility containina the retail loac1 provides the regulation needed to handle the retail wheeling of a iixed amount of generation to a cyclical load demand. (That is, it acts in a manner similar to a flywheel.) The costs for this arranaement venus the costs for the installation of a special AGC system control system for the generation source could then be used by the non~utility generator to select the most economic alternative. 7.5 A CAVEAT Althouah this chapter contains an optimistic view of the accommodation between non-utility aeneraton and their need for added wheelina services, the unconstrained connection and operation of non-utility aeneration to transmission and distribution systems could lead to chaos. The present interconnected power systems work, and work well, because the aeneration control systems keep the aeneration and demand closely balanced. If a lafle portion of the system aeneration becomes uncontrollable in the sense that it does not contribute to system regulation and is excluded from control by the utility system's control center, current economic scbedulinl and AOC systems may require major revisions. Similarly, the larae interconnections that exist today, operate successfuUy, permit larae amounts of economy intercban1e to take place, and minimize frequency excunions. They work because of the close frequency tolerance (i.e., load-aeneration balance) that is maintained and the voluntary cooperation of the interconnected systems' operaton. r. 1 .. ') ..... ... -7-33-
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Power Tecbnolo1le1, Inc. A general rise of unscheduled interchange power levels could use transmission capacity already scheduled by a utility. In the extreme it could result in the frequent overloading and opening of key interconnection circuits. If inadvertent interchange eneray becomes very Iarae, the present scheme of makina payment in kind (i.e. returnina MWh for MWh at similar times of the loads cycle) may have to be replaced by additional metering systems and billing systems along with appropriate tariff structures. If the future growth of non-utility generation is such that each independent ope!'ator of non-utility aeneration is permitted to attempt to operate to maximize his output, a revision of the economic scheduling and AGC methods may be required. Reaulating duties imposed on utility controlled generators would increase and a new, more strinaently enforced set of operatina rules might be required to preserve the widespread interconnected operation of today's systems. -7-34-
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Power Technolo1le1, Inc. CHAPJ'IB YID
PAGE 485
Power Technoloales, Inc. 8.1 GENERAL BACKGROUND CHAPTER 8 SUMMARY The purpose or this report is to present an overview or some or the important technical aspects or the U.S. electric utility industry and relate these technical racton to questions regarding: o transmission system technical limitations, o non-utility generation, 0 increased possibilities for wheeling, and o increased transmission access. The industry is extremely divene, with utilities rangina from larae integrated holdina companies which operate in several states to small distribution utilities servina a local community. The divenity is a result of the differences resultina from the historical evolvement of the systems, the nature of the loads, and the availability of various types of resources for the aeneration of electric eneray. The institutional structure includes an equally wide spectrum from J.arae investor owned holding companies and larae state or federal power agencies to small consumer owned cooperatives. The systems are all operated to produce eneray at a standard frequency of 60 Hz which is delivered to the retail customen at utilization voltaaes that must 8-1~ '175 1. Jbe industry 1s extremeJy d1verse. 2. Jbe systems ore oJJ operated to produce energy at o standard frequency at voltages that must toJJ w1th1n narrow, standard1zed 11m1ts,
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Power Technolo1ies, Inc. fall within narrow, standardized limits. These standards have been essential to the growth of the industry. Practically all electrical devices (i.e., moton, lamps, electronic devices, etc.) are designed and constructed to operate correctly only within the very narrow standards that apply to voltage and frequency. An important attribute of electrical energy is its reliability. Although not subject to formal engineering standards, a high reliability of service is a de facto standard in the industry. Consumen have received a high level of service reliability and the industry strives to continue to deliver their product on a very reliable buis. The reliability benefits both the consumen and the utilities. Widespread and prolonged service interruptions may ca~ consumen discomfort and economic losses. In some situations the loss of power may be life threatening. The consequences of poor service reliability to the industry itself are economic. Widespread, prolonged outages are expensive to remedy and may expose the utility to subsequent economic penalties. Electric energy is a unique product in a very important technical sense. It is consumed at essentially the same instant that it is produced. Except for the storage of water in hydroelectric plant reservoirs, there is no storage of the product; no way of building an "inventory" for later consumption. The delivery system (i.e., the transmission and distribution systems) also hu unique technical -1-2-3. A high JeveJ of service reliabiJity is a de facto standard in the industry. 4. Electric energy 1s a unique product in a very important technical sense, It is consumed at essentiaJJv the same instant it is produced,
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Power Technolo1le1, Inc. characteristics that make it different from telephone, gas or transportation systems. The flow of electric power must obey the physical laws that govern its behavior at all times. Power flow patterns will be instantly and automatically redistributed when demands change, generation patterns change, or when the transmission system is altered due to a circuit being switched in or out of service. There is no simple way, in an ac transmission system, to control the redistribution of power flows from a heavily load circuit to one with a light load. Power flows are controlled normally be shifting generation patterns, switching circuits, or dropping customer loads. The power system does not enjoy the same ability u that of the telephone system where communications may be switched automatically from a busy trunk line to a line with spare capacity. The industry is quite large with about 100 million customen being served by over 700,000 MW of generation. The vast majority (98 to 99 % approximl,tely) of the generating capability is owned and operated by the utility industry. Hydroelectric and nuclear power plants, each comprise about one eighth of the total capacity with the remainder beina fossil fueled steam and combustion turbine capacity. The transmiaion system is equally divene and large with about 610,000 miles of circuits lt voltages of 22 kV and above. The systems in the U.S. and Caoda are interconnected in r our large groups. lo each of -1-3r. s. The flow of electric power must obey the phys1ca1 laws that govern 1ts behavior at a11 times, 6. The power system does not enjov the same ab111ties as the telephone svstem to switch flows from busv circuits to circuits w1th spare capacitv, ,! 77 7. The svstems in the u,s. and Canada are interconnected 10 four large groups,
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Power Tecbnoloales, Inc. these the frequency is the same and power may theoretically flow throughout each interconnected area. The four groups, known as interconnections, are located in the western states and western C.aoada, the eastern states and parts of eastern Canada, the province of Quebec and the state of Texas. The interconnections are tied together by de circuits of limited capability which allow the control of the power flows between the larger systems. The reasons for the separation are historical, demographic and electrical. The eastern and western systems are separated by areas with low population and electrical load densities. The system in Quebec is very difficult to control during emergencies because of the very large concentrations of remotely located hydroelectric capacity and the many systems within the. state of Texas have Iona had a preference to remain electrically isolated from the other interconnections. The pattern of transmission systea that exists reflects the development of each reaion. In some areas there are extensive hiah voltage and extra high voltaae systems that intearate large systems and permit the exchan~c of economy eneray over long distances. In other regions, the pattern of development has been such that generation resources could be located close to load centen with the result that less transmission hu been required. The technology of high voltage ac transmission is such that the capability to transmit electric power of individual classes of circuits varies approximately with the square of the nominal voltage l .. vel for a 1-4-
PAGE 489
Power Technoloales, Inc. given transmission distance. The capability of transmission circuits also varies with transmission distance: a shorter line is capable of carrying more power than a longer one, all other things being equal. Longer line capabilities are limited by technical problems associated with the stability of the system while shorter circuits are usually limited by voltage related problems and the required VAR support. V ARs are analogous to MWs in the sense that they will flow in an ac electric power circuit. These are a consequence of the inherent physical nature of ac circuits where energy is stored in electric and magnetic fields. V ARs are required to support these fields and the fields an essential to the operation of the ac systems and consumption devices. The quantity of V ARs required depends on the needs to control the voltage levels in the power system. ID some urban areas ac underground cable systems have been installed. These are expensive installations that usually cost 2 to IS times as much u the equivalent overhead circuit. In urban areas with limited land availability and high load densities, underground cable transmission is the only technically feasible way to deliver the required power. ID a few special situations de transmission has been installed. These are usually circuits that connect the large interconnections or are installed where an electrical express highwayis needed. Direct current has the advantage that the power flows over r -1-5-
PAGE 490
Power Techaolo1les, Inc. circuits may be controlled directly at the terminals. Examples are the Pacific Northwest Intertie and the de ties between Quebec and the eastern systems in the U.S. 8.2 ASPECTS OF SYSTEM CONTROL The control of the power generation is coordinated by the utilities to satisfy the demand cycle of the loads. At all times the demand and power generated must be in balance to hold the frequency constant. System operaton have to place more capacity online than the expected load demands in order to protect against unanticipated load levels and against sudden shortages that may occur if a plant, unit, or major circuit aoes out of service. The generating units in any system are controlled in an optimal economic manner such that the marainal costs of production in the system are u uniform u possible. Centrally dispatched power pools and power broker systems enlarge the economic dispatch area beyond the boundaries of single utility systems. Marginal costs generally increase with demand. Transmission system losses or transmission capacity limitations may bias the generation dispatch such that the marginal costs are not precisely uniform throughout the system, but vary with location. The introduction of storaae (of water or fuel under a take-or-pay contract) complicates the dispatch problem converting it to one that must be solved to minimize production costs over some time period. Long and short term power exchanges with r -8-6-a. The control of cower generation is coordinated by the utilities to satisfy the demond cycle of the loads. 9. Ibe generating un1ts in any system ore dispatched in on optimol economic manner such that the morqinoJ costs ot production in the system ore os un1fonn os possible,
PAGE 491
Power Tecbaolo1les, lac. interconnected systems affect the scheduling of generation as well. Non-utility generation may not be dispatchable by the utility system operaton. In small quantities, this generation is considered as a load reduction in scheduling. In larger quantities the operaton have to assume that the non-utility capacity has to run. Economy interchange of power reducer the cost differences between interconnected systems. Economy interchange between systems has grown greatly in recent yean since the oil price level changes have upset the historical pattern of fuel prices. Environmental concerns and regulations have fostered economic interchanae u aeaeratian has been shifted to sourcea remote from urban load centen. On both coasts, utilities with hip concentrations of oil burnina generation have increased their importation of eneray produced by coal burnina plants and hydroelectric plants. Economy interchanges may be arranged by direct negotiations between system dispatcben or may take place under long term contracts arru.1ed Mtween utilities. In some areas extensive transmission sys~ms have been constructed to take advantqe of eneray price differences. The wheeling of power for economy purposes has been the result of negotiations between utilities except for the wheeling under PURPA reuulations. Wbeelin1 takes place under a variety of rate structures for transmission service. Simultaneous buy-sell transactions frequently serve the same -1-7-10. Economy interchange of power reduces the cost differences between interconnected systems.
PAGE 492
Power Techaoloales, lac. technical pun:,ose of economy interchang~ between systems that ue not directly interconnected and replace the sale of transmission service. The automatic generation control systems in use in the U.S. ue esse:itial to the successful operation of the interconnected systems. They are designed to control the flow of power over interconnections to their scheduled values u well u controlling the aeneration for economic dispatch. Since the transmission systems are owned and operated by several hundred different utilities, this control is decentramed into about 1 SO different control ueas. When a control area experiences an imbalance between load and aeneration. the AGC systems in that area and in the interconnected control ueas ue able to discriminate between locations. The uea with the imbalance is expected to restore the oalance between aeneration ud load without long term dependence on the neighborina systems. lntertie nows have to be restored to normal within the time period of emeraency capability ratina of lines involved. There is no single centralized control of ~eneration in each major interconnection. The coordinated operation of these control areas is essential to the succeuful performance of tarae interconnected regions. The industry voluntarily coordinates and polices these operations under the auidance of the NERC Operating Committee. Without these efforts the interties between the utilities would frequently become overloaded and automatically opened, interruptina the now of sch,,duled power -8-8-11. Ibe automatic generation control systems in use 1n the u,s, ore essent101 to the successful operation of the interconnected systems, 12. Ibe coordinated operation of these control areas 1s essential to the successful oectonnonce of large interconnected regions, 13. Ibe industry volun tarily coordinates and poJ1ces these operations uncter the guidance of the NERC Operating committee, 1 ') r, ... l,,J ...
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Power Tecbaoloaln, lac. tramactions. These intercbanaes ue also used to share aeneration reserves in emeraencies. If the overall control system were to become disrupted, the effects would be to reduce reliability and increue the requirements for aeneration reserves in the Iona nm in order to hold service reliability levels at their current levels. These AGC systems are not perfect, so some level of inadvertent interchaqe will occur. The current practice iD the U.S. is to meter this inadvertent iDterchuae and repay it iD kind at similar times. These arranaements are also part of the cooperation between system operaton. ()peratiD1 errlCiency is improved by coordinated economic dispatch of aepuaaa utilities in power pools and iD markets orpnized Wider power broker schemes. Some utilities are memben or centrally dispa&cbed power pools where the 1eneration throupout the pool ii dispatched on a siDale system bail. These pooled systems, whether umrrwated companies or memben of a boldiD1 company structure, achieve 1 viDp in operatiD1 COl1I and iD the plumiD1 and implementation of system e~pamiom. Power broker systems have been established in venl naiom or the country to achieve operatina COit vinp without I formal pool ltnlCtlll'e. Thell broker system1 fo"DU the market for economy intercbanp, replaciDa the one-on-one nqotiatiom between utility dispatcbm. 14. OQlcatinq 1rr1c1encv 1s imroywt by coordinated economic dispatch Qf sapocote uti]ities 1n AMC pools and 10 Nckets organized under power broker scbne,, I" 1')') --' -,_,_
PAGE 494
Power Teclaaoloala, lac. Generation ii also controlled to usilt in the rqulation of system voltqN. Control of the aeoeration excitation level will provide a controllable source of VARI. The voltaae control devices on the system (e.1 shunt capaciton, sves. etc.) all have a limited control ranae. Supply of V ARs by aeneraton ii an important tool for system voltaae control. Trammiaion line flows are normally controlled indirectly by tbe control of the aeneration. When a tTlmmisaion circuit ii in danaer of beina overloaded, tbe dispatcher lhif'a aeneration to reduce the circuits loadina. Muy systems utilia a preventative (or defemive) system of aeneration scbeduliq to prevent c11cec.Un1 outapl and blackou11 which could result from the occurrence of a llllale faihan ill the tyttem. Tb8le security constrained dispatch techniqaes analyze the pneration schedule ud tnmmillion system power flows, NUCh for wont cae continpncy situations, ud adjust the pneration schedule to prevent the wont cue from occurriDa. This resulu ill an economic cost due to iDcreued productipn eo111 ud mo limits the nows over the transmission system by boldina some level of tnmmiaion capacity ill reterVe. Althoup there ue no n..~ that will prove it, the operatina results appear to bave bin excelleDt due to the adoption of this practice over the pat 20 yean. A comequence of this 1111 of preventative methods of pneration 1eblduliq and similar schemes for tabliahiaa trullf'er capacity limits ii that available 1-10-1s. Jransmiss1on 11ne flows are nonnalJy controlled ind1rect1y by tbe control of generation, 16. Monx systems ut111ze a preventative system of generation scheduling to prevent cascading outages and blackouts, 17. 1 'J 1 .. .. A consequence of this use of preventative generation scheduling and si1111r methods for utablish1ng transfer capab111tv J11its is tt.;t ayaiJable transm1ss1on capacity 1s not r1xect,
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Power Tecllaoloal, lac. trammission capacity is not fixed. It varies with load and aeneration patterns, with circuit and unit availability, and with the different patterns of intercbanae transactions. 1.3 TRANSMISmON LIMITATION AND TECHNICAL REMEDIES Trammiaion systems have been developed to deliver power to load areu, intearate system operations, share aeneration reserves between interconnected systems, and facilitate the economic intercbanae or power. Transmission limitations do occur in all systems. ID some c:ues, these are due to the physical limits, current carryina capability or voltaae tolenncel, while in other cues theN limits are the comequence or operational problems. The potential eff ecta or e:irc:eec1in1 tbeN limitations depend upon the nature or the limit. Exceedina thermal limitatiom of lines and equipment may c:a111e dam11e to tbele elements. Limitations due to opentin1 procedUJ'II affect tbe production costs wben optimal economic dispatch 1ebedules CIDDOt be achieved. Limits affect tbe ability to share aeneration reserves, to enpae in economic: intercbanae tramactiom, and to provide wbeelina services. Trananmio limits, in many cues, are caused by the circuit ractance which impedes power nowt and c:a11111 1iDe voltap drops. Tbe reactuce increues the power ua)el between 1eneraton wben power Volcqe drope must be limited to the nqe tbat by the tap c:han1in1 tnmf'ormen and other voltqe control devices on -1-llr 1s. Jrans11ssion ]imitations occur in oJJ syste,a, 19. L1aits affect the abiJity to share generation reserv.11.& to engage 1n economic interchange transac tions, and to provide wtJnJ1ng services,
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Power Tecbaolo1ln, lac. the system. Power angles cannot become too large or stability problems will result that may cause generaton and power flows to oscillate at low frequencies and ultimately result in system separations. Transmission limitations related to system operations occur u a result or the power now distributions which normally take place on the electric power system. When a circuit is suddenly removed the power nows will redistribute instantly and automatically and may result in an overload. If the system cannot be readjusted rapidly enouah to restore loadinp to normal within prescribed time periods, the alternative is to restrict the nows so that outaa do not result in overlOlded conditions. Hence the development of security bued generation dispatch techniques to prevent these events. Loop flows over interconnected system circuits are another consequence of the natural distribution or power nows. These result Crom interchanae transactions between systems. The power will now where it must to satisfy the physical laws. Simultaneous intercban1 takina place on the Iarae interconnected systems compound the problem caused by loop nows and make life more difficult for system operaton. In some instances, penistent loop nows may interfere with the operation or systems not participatina in the interchana. Operaton may be forced to curtail the interchanges or systems may arran1e for the instillation of special control devices (e.1.. pbue shiftin1 tramf ormen) which will reduet the unwanted effects. 1-12, 20. Transmission limita tions related to system operations occur as o result of the power flow distributions which nonna11v take place on the electric power system, 21. Loop tJows over interconnected systems ore another consequence of tbe natural distribution Of power fl 0WS I 1 0 f~ .. -.
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Power Techaolo1les, lac. Voltage control and potential voltage collapse problems may limit transmission flows. These occur when sudden requirementi for V ARs exceed the available supply. They arise frequently in the systems where large interchanges are scheduled and sudden major circuit outages occur. Systems may suffer dynamic problems which require transmission flows to be limited. These may be transient stability problems which cause low frequency oscillations or subsynchronous resonance problems. These problems usually appear in systems with longer transmission distances and have occurred most frequently in the western part of the country. Based upon considerations of technical limitations to transmission flows it appears that teciJ.nical remedies are available to increase transmission flows by substantial incremental amounts. VAR supplies may be installed to aid in voltaae and stability problems. Intermediate switching stations may be required to cure a stability limited system with lonaer lines. Generator stabilizen, series capaciton, and new turbine and boiler controls may be installed on existin1 plants to increase stability marains and improve power plant response characteristics. Lines may be rebuilt with new, larger conducton to increase current capacities. Line monitorina schemes which allow the use of current local weather conditions to estabU.h dynamic line capacities may be used. Some circuits may be reconsttucted at hiper voltqe levels. Opentin1 practices may be installed to alleviate stability induced limits. -1-13-22. YoJtage controJ and potent101 voJtage coJJopse probJems may 11m1t transm1ss10n flows, 23. Systems may suffer dynamic probJems wh1ch reau1re transm1ss1on flows to be 11m1tect, 24. Techn1ca1 remedies are avaiJabJe to increase transmiss1on flows by substantial 1ncrementaJ amounts, 1 ") 7 '-
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Power Technoloales, Inc. The development of special protective systems to react rapidly to contingencies may allow the increased loading of some lines which would have been limited under a security constrained dispatch. Generation redispatch may allow the increased use of circuits at some penalty in production costs. Phase angle regulators may be installed in a few key locations to prevent loop flows from using transmission capacity. The development of emergency plans, operating procedures, and post-emergency restoration schemes may encourage system operators to operate closer to the physical limitations of the system. All of these technical remedies have been used effectively. There is no universal measure of applicability, cost, or effectiveness of these technical remedies. The limitations which occur are highly system specific and will change with time. In the long run, the most effective remedy for transmission limitations is the construction of new transmission facilities. The costs for high voltage ov,9rhea,sconstruction vary greatly and are very dependent on the cost of securing rights-of-way. Lengthening construction cycles also add to these costs. Line construction costs are presented in the text based on current approximate data. The capacity costs for new transmission construction range from about S1000 per MW-mile at 110 to 138 kV down to about ISO to 200 dollan per MW-mile at 765 kV. 8-1425. There 1s no universal measure of acpJicabi1-1tv, cost or effectiveness of these technical remedies, 26. In the Jong run, the most effect1ve remedy for transm1ss1on 11m1tat10ns 1s the construction of new transm1ss1on tac1Ji t1es, 108 lJ. .J
PAGE 499
Power Technolo1ln, lac. These are for construction only and do not include costs for VAR compensation or losses. The current announced plans of the industry are such that projected transmission construction levels keep dropping. This is caused by both the decline in new generation construction and the effects of environmental regulations. If the current transmission construction trends persist, the industry may have to live with essentially the current stock of transmission facilities. 8.4 WHEELING AND NON-um.ITV GENERATION The wheeling of power between electric utilities for economy industry result of interchange is a regular practice of the Leveli of wheeling have increased as a regional cliff erences in fuel costs. As these price levels chanae the level of wbeelina transactions react accordinaly. Current wheeling arrangements are made between essentially non-competing utilities. These are accomplished technically by having the selling system increase its generation level and the purchaser decrease its level. Chanaes in transmission system losses are usually supplied by the seller. The interchange schedule is supplied to the area automatic 1eneration control and becomes the responsibility of the sellina utility. Wheelina may occuionally cause technically related transmission problems. The most frequent is that of loop nows. In many cues the effects of loop flows 1-1521. If the current transmission construc tion trends pers1st, the industry may have to 11ve with essen tially the current stock of transmjss1on fac111t1es, 28. The wheeling of power between ut1lities for economy interchange is a regular pract1ce of the industry, 29. current wheeling arrangements are made between essentially non-competing ut111t1es, r 1')0 ... ,_.
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Power Techaolo1lu, lac. are acceptable and do not cause operating difficulties or restrictions. In other cases where they do, the transaction may have to be curtailed. The transmission capacity available for wheeling is affected by other transactions taking place simultaneously. Load and aeneration patterns affect available transmission capacity. Transmission circuit availability. transmission circuit losses, and voltage V AR problems also influence this capacity at any given time. Wheeling power is an alternative to generation and the availability of low cost power sources within reach of the system affects both planning and operating practices. Wheeling rates, schedules, and availability vary with the region. Rates are subject to regulation by the FERC. Non-utility generation is not new in the utility arena. Self -generation and industrial cogeneraton have been in existence for most of the industry's history. Since the passage of PURP A in 1978 new qualified facilities, small power producen, and industrial cogeneraton have risen in volume and importance." Recently there have been a number of actual and proposed independent power producen. Non-utility generation sources affect utility system planning and operations. The extent and actuality of proposed non-utility resources causes an uncertainty in utility planDing. The longevity of these new sources is of concern to utility plannen. The connection of these new resources to the system may 8-1630. The transm1ss10n capacity avo1JabJe for wheeJ1na 1s affected by other troosoct1ons tak1na oJoce s1mu1taneous1v. 31. Non-ut111ty generation sources affect ut1]1ty system 0Jonn1ng and operat1ons.
PAGE 501
Power Tecbaoloales, lac. affect transmission planning and system development. If the new sources are located near load centen, they may release transmission capacity and improve system performance. If they are remotely located, they may cause the utility to construct new transmission. The lead time requirements for the new generation are frequently much less than that for new transmission so a coordination problem may arise. Utilities face a hiah level of uncertainty concernina the many of the announced, planned developments of non-utility generation do not actually occur. System operations and economy may be adversely affected by non-utility generation in larae quantities. Many utilities have installed laraer steam units which were not desiped for cyclic operation. If the non utility aeneration ii non-dispatcbable and is large enoup to supply a major portion of the demand at light load periods, the utility may have to devise uneconomic aeneration schedules to accommodate this non-utility aeneration. In some cues, projected levels of uncontrollable aeneration have been such that economic interchange transactions have had to be curtailed. Non-utility aeneration affects the level of spinnina reserve required and may seriously affect the network loadina and security dispatch patterns. Non-utility aeneration requires coordination with utility emeqency operatina procedures. Non-utility aeneration is frequendy shutdown automatically durina system aeneration 1horta1es by -8-17-32. Ut1J1ties face o high JeyeJ of uncertainty concerning transmission system require ments s1nce many of the announced, planned deyeJopments of nonut111ty generation do not actually occur. 33. System operations and economy may be adyerseJv affected by non-utiJ1tv generation 1n Jorge quantities,
PAGE 502
Power Techaoloales, lac. underfrequency relays, further addina to the aeneration sbortaae. Distributed generation sources are smaller units connected to the distribution system. They cause a different set of technical problems than the larger units. Some are induction generators that may become self-excited at the wrong time. Some aenerate harmonics on the power distribution system. All of these technical problems are curable with the cooperative efforts or the utility and non-utility aeneraton. It appean that in many systems, wheeling or nonutility aeneration can be accommodated in smaller amounts. When the requirements for wheelina become laqe it may cause problems with the area control if the non-utility aeneration is non controllable. Large amounts or wheelina or this type or aeneration will increase the requirements for meterina, communications links to the control center, and may increase levels of inadvertent interchange. The same aeneral observation may be made with reprd to retail wbeelina for utilities or for nonutility aeneration. system controls can retail wbeelina. In increue in the In smaller amounts, the current accommodate increased levels of Iaraer amounts and with a large number or retail wbeelina transactions, the current schemes for automatic aeneration control may become taxed beyond their capabilities. A larae increase in the number of transactions would require a correspondin1 increase -8-18-34. In Jaraer amounts and with a Jarge increase in the number ot retaiJ whee]1na transactions, the current schemes tor automatic aenerat1on controJ may become taxed beyond the1r capabiJit1es,
PAGE 503
Power Technoloales, lac. in metering, monitoring, and control points for AGC systems. Arrangements for standby service and contract terms for inadvertent interchange payments may be required, changing the nature of the current systems and arrangements. Retail wheeling in unlimited amounts has the potential for causing serious system control problems. In combination with a large increase in uncontrollable non-utility generation, this could seriously degrade the performance and reliability of the electric power systems. 8-19-35. Retail wheeling 1n unlimited amounts has the potential for causing serious system control problems, Jn combination with a large increase in uncontrollable non utility generation, this could seriously degrade the performance and reliability of the electric power systems, .1 0 ".J "~ i:J'
PAGE 504
Power Technoloales, Inc. BJ;;fERENCES
PAGE 505
Power Tecbnoloaln, Inc. REFERENCES 1. fungauH!PtaJs of Electric Power Systems for System Operators. (2 volumes), Course Notes, Power Technologies, Inc., January 1987. 2. Distribution System Operation Vigeqtraining Workbook, Course Notes, Power Technologies, Inc., 1984. 3. 4. s. 6. 7. 8. 9. 10. Electric Utility smems and Practices (book), 4th Edition, H.M. Rustebakke, Editor, John Wiley & Sons, Inc., 1983. L.O. Barthold and 0.0. Wilson, --rhe U.S. Power System -A Study in Pluralism, article for Power Tec;hnotoay International. Sterling Publications, London, England (to be published), 1987. National Elec;tricaI Sahty Code -1987 Edition. American National Standards Imtitute, ANSI C2 -1987. Published by the IEEE, 1987. R. Juseret, CIGRE Study Committee 37, Working Group 01, "Comparison of the Reliability Criteria Used in Various Countries Synthesis." CIGRE Paper 84-07-101 (E), Provisional. JJ. Archembault, G. Becker, H.G. Bush, U.G. IC.night, P. Feintuch, F. Maury, J.P. Barret, G.H. Cordonnier, T. Jobaosson, G. Nordlof, G. Alfors, TJ. Nagel, R.W. Werts, --rhe Reliability of Large Power Systems." CIGRE Conference Paper 32-16, Paris, France, August 27 September 4, 1980. Reliability Criteria for Interconnected Systems Operation. Operating Committee of the North American Reliability Council, NERC-OC, printed by NERC, Princeton, NJ., Dec 3, 1985. Powe, Syst:m Relia.bility Calcula.tiom (book), R. Billinton, R.J. Ringlee and AJ. Wood, MIT Press, 1973. Statistical Yearbook of the Electric Utility Industrv/1986. Edison Electric Institute, October 1987. 11. Inventory of Power Plang in the United States 1986. u.s. DOE/EIA0095(16), Auaust 1917. 12. Monthly Energy Review, lvoc 1211. u.s. DOE/EIA-003S(87/86), May 1987. 13. Annual Statistical Report", STAFF, Elec;trical World, Arril 1986, pp. 49-64. I
PAGE 506
Power Tecbaolo1les, Inc. 14. B.F. Wollenberg and A.J. Wood, Power Generation. Oof'ration and Control. 15. John Wiley and Sons, Inc., 1983, New York, NY. Cool Water Gasification Program -fiat Annual Progress Report. Bechtel Power Corp., et al, AP-2487, July 1982, EPRI, Palo Alto, CA. 16. D.H. Cooke, combined Cycle Thermodynamic Inquiries and Options for Cogeneration Facilities in the Process Industry, ASME Paper, 87-JPGC PWR-61, presented at the ASME/IEEE Power Generation Conference, October 408, 1987. 11. I 987 EiccU:icity Supply and Demand for 1987-1996. NERC Publication, November 1987. 18. R.D. Dunlop et al, Analytical Development of Luadability Characteristics for EHV and UHV Transmission Lines, IEEE Traoaactions on Power Appantu., and smems, PAS-98, p. 607 ff. 19. Iraoamigion Linc BeCercncc Book. Second Edition, EPRI, I 982. 20. 1987 Bolia,bilitv APCPJPent Ibo future or Bulk Electric System Reliability in North America. 1987-1996. NERC Publication, October 1987. 21. I. Glende and T.O. Berntsen., "Emergency Control of the Skagerrak HVDC Link u a Part of a Coordinated Network Protection Scheme." Paper 3279-00-61, presented at CIGRE Study Committee 32 Meeting, Minneapolis, MN, May 1979. 22. Underground Cable Systems, Course Notes, Power Technologies, Inc., 1982. 23. 24. Underground Power Trammipiop. Arthur o. Little, Inc., Electric Research Council Publication 1-72, October 1971. Standard Handbook for Etecu:icaI Engineea (book), 12th Edition, McGraw-Hill Book Company, 1987. Cable, pp. 14-97 and 14-110. 25. NERC Opeqting Manual. NERC Operating Committee, NERC Publication, revised December 1, 1987. 26. Power System Opeqtion Videotrainin1 Workbook, Coune Notes, Power Technoloaies, Inc., 1982. 27. IEEE Committee Report, "Description and Biblioaraphy of Major Economy-Security Functions, Parts I, n, and m. IEEE Irawctiom on Power APPIRWI and SysttUQL Vol. PAS-100, No. I, January 1981, pp. 211-235. 2
PAGE 507
Power Tecbaoloaln, lac. 21. BcoeOm of 1mprpyc4 Gas Jurbige BeJiabilirv. EPRI Repon, AP-4162, Research Project EP-1187-10, October 198S. 29. R.E. Bohn, and M.C. Caramanis Wheeling Ratn; An EconomicEn1inccrio1 foun4ltion. MIT Laboratory for Electromagnetic and Electronic Systems, Cambrid1e, MA, Report TR 85-00S, September 1985. 30. J.N. Wrubel, P. Van Olinda. B.F. Wollenbera, O.J. Denison, G.W. Woodzell, "Expandin1 an Eneray Control Center to Include a Bulk System Security Package. IEEE Inoernons oD Power Apparatus and $Y1tems, Jan. 1982, pp. 34-42. 31. B. Sto~ "Security Dispatch U1in1 Linear Programmioa: JEll Inoarnou QD Powm: ApPIQtus and $Y1tcJN, May/June 1979, pp. 837831. 32. R. Luatu, "Security Comtrained Dispatch Formulated as Optimization Problem with Line Inequality Con!.traints. IEEE TpDpctiom on Power Appuatus and Systems, March/April 1977, pp. 347-356. 33. S.L. Corey and A. Elacqua, "Security Constrained Dispatch at the New York Power PooL IEEE lPDRsti?U on Power APQl(ltus yd Systems. Au1111t 1912, pp. 2176-llU. 34. SJIDdlrd Hendhgok (or EleetricaJ En1ioom (book), 12th Edition, McGraw-Hill Book Company, 1917. lntercon.nectiom (Section 16) pp. 16-1 and 16-59. 35. F.P. de Mello, D.N. Ewart, M. Temolbo~ and M.A. Euenberaer, 9Turbine Eneray Controls Aid in Power System Performance: Prpcpjipp of the Amcrisan Po,m confcRJA, Vol xxvm. I96'i, pp. 438-i-iS. 36. F.P. de Mello, 9Tbe EC(ecll of Control: IEEE Tutorial Course OD Modern Concepts or Power System l)ynamica, Paper 70M62-PWR.. 1970. 37. T.A. Mikolimm and B.F. Wolleot,era, An Advanced Cootinaency Selection AJaorithm. IEEE Inmstinaa on Powcr hPPIRM yd SJIWDI, Vol PAS-100, February 1981, pp. 608-617. 38. S.C. Thomas, "Normal/Emeraency Operations Utility Needs and Experience. Paper praented at the Workshop on Electric Eneray System1 Research, Natiollll Academy Press, 198', pp. 165-173. 39. Inmfs C,mbWgy A Bofor1PF1 Qgqgpept, NERC Tramf'er Capability TukForce,NERC,PriDcetoD,NJ,October 19IO. 3
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Power Tecbaoloaln, lac. 40. An Appm,sb for Perem;o;o, Ir;wCcr capability Obics;tivcs -Vol, J; Mcthgdol91y IQd Appliqtiop f11m2le, EPRI Research Repon EL-3425, Research Project RP 1960-1, March 1911. "ECAR/MAAC lntenep>nal Power Transfer Analysis. Coordinatina Group, Jwae 191.S. ECAR/MAAC 42. IoFboiql Limiqtiom 1p Imoamipiop smem OQerariom. EPRI Research Project Report RP-.500.5-2, Final Draft submitted to EPRI, August 1987. 43. A.K. Deb, IDd J.F. Hall, 9Prediction of Overhead Line Ampacity by Stocbutic and Deterministic Models. Paper 510-2, presented at the 1986 IEEE T&D Collf'erence. JE:t;t: 5nrdeal rm C,ISPJt.tign C Rm PYcrha4 Copduc;tor JcmommR end AmPIFiSY UP41[ S:Wdy-Sgg Conditigm. ANSI/IEEE Standard 7381916, Publilbed by IEEE, New York. NY. 45. GJ. Ramon, Tllk Force Chairman. "Dynamic Thermal Line RatingSummery aDd Scatul or tbe Seate-of-the-An Technology. IEEE Paper MSM699-1. 46. D.A. Douala, -Weather Dependent versus Static Thermal Line Ratings. Paper 503-7, prwntad at tbe 1916 IEEE T&D Collf'erence. 47. R.C. Black IDd R.S. Throop, A Live Line Method for Retensionina Tnmmwio11 Lim Coadacton. CIGRE Paper 22-10, 1970. 41. J.A. Rob~ --rower Reillforcilla Applied to Rebuilds. Edilc>II Electric Institute, T.,n,mia'n Committee, October 16, 1915, Baltimore, MD. Transmission Line and Distribution 49. !endltd Circpit Qpip (At I U-111 kV Comppct Tpp3migiop Ling, EPRJ Report EL-1314, February, 1980. 50. -C... History Utah Power & Lipt Company Convenion of Double Cimdt 230 kV to J.C5 kV Line. IEEE/PES 9th Conference on Overhead IDd UDder-poUDd .,.,.nm,iaion 111d Distribution, Kanas City, MO, May 2, 1914. 51. IKbnka IIIA Emnemk; Clw::wiJltiUiq of ffisb Phee Order Power TppppipknL U.S. Dlputmnt oC EDeqy Report DOE/ET/29297-2. 52. EBY !Ub nw Anllt Ppwl[ Tpnm,ipiqn. U.S. Department of Eneray Report. DOE/ET/29297-3, September, 1913.
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Power Techaoloaln, lac. 53. ,., 55 56. I.S. Grant and J.R. Stewart, "Mechanical and Electrical Characteristics of EHV Hiah Phase Order Overhead Transmission. Paper 84T&D318-2, preaented at the IEEE/PES 9th Transmission & Distribution Conference, Kansas City, MO., April 29-May 4, 1914. Hybrid ac/dc Operation Appean to be Feasible for Double Circuit Line Uparade. ElOCl[ic Lib& A Power, July, 1986, pp. 18-19. Hybrid Imom>iaion Linos NP4c and I:wo CgnducJCd Linc Corona and field Effect Tests, EPRI Research Project Rtport RP 2472-1, Hiah Voltaae Trammiaion ReNarCh Facility, December 1983. N.G. Hiqorani and L.E. ZafaneUa. DC Lin in Cloee Proximity. Montreal, June 1-12, 1917. corona and Field Effects of AC and CIGRE Study Committee 36 Paper. 57. T.R. Gnve, E. Kallaur, and J.A. William, -Upratina of Hiah Pressure Gu-Filled Feeden by Fluid-Fillina and Rapid Circulation: Paper 16TAD574-I, presented t the IEEE T&D Conference, Anaheim, CA, September, 1916. 51. E.H. Ball, J.D. Endacott. DJ. Skipper, "UK Requirements for Future Prolpects for Forced-Cooled Cable Systems. Proceeding IEE, Vol. 124, No. 3, March 1977, pp. 334-331. 59. M.D. Buctweicz, A~. Dima, J.B. Prime, G.W. Seman, D.A. Silver, and, J.G. Vlldel, "Development of Reduced Wall 131 kV HPOF Pipe Type Cable and Joints for Reconductorina of Exiatina 69 kV Lines on the Florida Power A Liaht Company System. IEEE Tpppctigns on Power APPVIQII IP4 Sys&1m1, Vol. PAS-100, No. 7, July 1911, llWMl 16-3. 60. R.T. Carter, et al. Allalysia of Radio Interference and Substation ModuJCatiom for Upratina 115-kV Substation to 230 kV: IEll Imoestl2P1 AP Power Delivery, Vol. PWRD-2, No. 2, April 1917, pp. 544-550. 61. W.J. McNutt. and M.R. Patel, -nie Combined Effects of Thermal Aaina and Short-Circuit Stnaes on Tramf ormer Lue: IEEE Tpnpctigm on Po:ar ApQIRtm and $DSOIQI, Vol. PAS-95, No. 4, July/ Auaust 1976, pp. 1275-1213. 62. W.J. McNutt. G.H. Kaufmann, A.P. Vitola, J.D. MacDonald, -Shon-Time Failu.n Mode Comidentiona Aaociated with Power Tramf ormer Overloldina. IEEE InnnsrioPI AP Ppwpr AQPIO,QIS yd SVl&olQI, Vol. PAS-99, No. 3, May/JUDI 1910, pp. 1116-1197.
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Power Tecbaoloales, lac. 63. M.D. Germani, G.L. Ford, E.G. Neudorf, M. Vainberg, M.A. El-kady, R.W.D. Ganton, "Probabilistic Short-Circuit Uprating of a Station Strain Bus System Overview and Application. IEEE Transactions on Power Qeliyery, Vol. PWRD1, No., 3, 1986, pp. 111-117. 64. M. Vainbera, et al. "Probabilistic Short-Circuit Upratina of Station Strain B111 System -Probabilistic Formulation. IEEE Tramactions oo Power Delivery. Vol. PWRD-1, No. 3, 1986, pp 129-141. 65. R.M. Maliszewski, -Yransmiaion Made Easy, ~resentation to the Legal Committee or EEi, May 1986. 66. T.W. Kay, P.W. Sauer, R.D. Shultz, R.A. Smith, -EHV and UHV Line Loadability Dependence 01:1 v AR Supply Capability. IEEE Transactions og Power ApQVIQll yd Sysu,1111. Vol. PAS-101, No. 9, September 1982, pp. 3561-3575. 67. Current Operational Problems Working Group, System Operations Subcommittee of the System Engineering Committee, EHV Operating Problems Associated with Reactive Control. IEEE Trapgctiom on Power AQPIRhll end Systems. PAS-100, No. 3, March 1981, pp. 1376-1381. 68. R.G. Carpentier and E. Sc:ano, -Voltaae Collapse Proximity Indicator from an Optimal Power Flow. ProcomUnu or tbe Power Svsu,m Computation Confoma, Hellinki, 1915. 69. J.G.P. Seo~ -nit VCPI Sensitivity Indicator: Application Experience. PrpcerUnu or tbe 19 CIQRE Conference. Discussion of Question 1.4, Group 31. 70. W.R. Lacbs, "Voltqe Colllpse in EHV Power Systems. Paper A78-057-2 presented at the IEEE PES Winter Power Meetina, New York, January 29Febnwy 3, 1978. 71. B.P. Lim and N.D. Reppen, "Predicting the Risk of Voltaae Collapse. Power ])chnoloain, Inc, Newsletter, April, I 984. 72. "Sinale Pole Switchina for Stability and Reliability. IEEE Panel Discllllion Report, IEEE Tpppctions op Power Apparatus apd Systems. Vol. PWRS-1, 1986, pp. 25-36. 73. F.P. de Mello, L.N. Bannett, and J.M. Undrill, -Practical Approaches to Supplementary Stabilizina from Acceleratina Power. IEEE Tc,pgctions op Power ApQVlhll yd System, Vol. PAS-97, No.5, September/October 1971, pp. 1515-1522. 6
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Power Techaolo1ln, lac. 74. F.P. de Mello, L.N. Hannett, D.W. Parkinson, and J.S. Czuba, "A Power System Stabilizer Design Using Digital Control." IEEE Transactions on Power Apparatus and Sv,tems, Vol. PAS-101, No.8, August 1982, pp. 28602868. 75. J.S. Czuba, J.R. Willis, L.N. Hannett, "Implementation of Power Systems Stabillier at the Ludinaton Pumped Storage Plant." IEEE Transactions on Power Apparatus and Sv,tem,s. Vol. PWRS-1, No. 1, 1985, pp. 121-128. 76. R.H. Park, "Fut Turbine Valving." Paper T-72-635-1, presented at the 1972 Joint IEEE/ ASME Power Generation Conference, Boston, September 10-14, 1972. 77. L. Edwards, P. Hughes, J.E. Welsh, "Sustained Fast Valving at TV A's Cumberland Steam Plant Backaround and Test Results. American Power Conference, 1981. 78. IEEE Panel Discussion, "Turbine Fut Valving to Aid System Stability: 79. Benefits and Other Considerations." IEEE Transactions on Power Systems. Vol. PWRS-1, No. I, 1986, pp. 143-153. Tuk Force on Discrete Supplementary Performance Workina Group of IEEE Committee, "A Description of Discrete Stability." JEEE Transactions on Power PAS-97, January-February 1978, pp. 149-165. Controls of the Dynamic Power Systems Engineering Supplementary Controls for Apparatus and Sv,tems. Vol. 80. D.C. Lee, P. Kundar, "Advanced Excitation Controls for Power System Stability Enhancement." CIGRE Paper 38-10, Paris Session, August 27September 4, 1986. 81. M.L. Shelton, W.A. Mittelstadt, P.F. Winkelman, W.J. Bellerby, "Bonneville Power Administration 1400-MW Brakina Resistor." IEEE Trang.ctions on Power Apparatus and Sv,tems, Vol. PAS-94, 1975, pp. 602-611. 82. C. Concordia, "System 1Jannin1 Considerations of Subsynchronous Resonance." Prepared for Subsynchronous Resonance Symposium, IEEE PES Summer Power Meeting, San Francisco, California, July 20-25, 1975. 83. L.A. Kilaore and D.G. Ramey, "Transmission and Generation System Analysis Procedures for Subsynchrooous Resonance Problems. Presented at the IEEE PES Summer Power Meetina, Subtynchrooous Resonance Symposium, July 24, 1975. 84. C.E.J. Bowler, C. Concordia, D.N. Ewart, "Self-Excited Tonional Frequency Oscillations with Series Capaciton." IEEE Transactions on Power Apparatus and Sv,tems, Vol. PAS-92, 1973, pp. 1688-1695. 7
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Power Techaolo1les, lac. 85. Bibliography for the Study or Subsynchronous Resonance Between Rotating Machines and Power Systems. Subsynchronous Resonance Task Force, IEEE Transactions on Power Apparatus and Systems. Vol. PAS-95, 1976, pp. 216-218. 86. D.G. Ramey, "Subsynchronous Resonance Tests and Torsional Monitoring System Verificsation at Cholla Station. IEEE Transactions op Power Apparatus and Systems. Vol. PAS-99, 1980, pp. 1900-1907. 87. R.G. Farmer, A.L. Katz, and A.L. Schwalb, Navajo Project Report on Subsynchronous Resonance-Analysis and Solutions. IEEE Transactions on Power Apparatus and Systems, Vol. PAS-96, 1977, pp. 1226-1232. 88. J.A. CawZD, -Free Market Electricity: Potential Impacts on Utility Pooling and Coordination, Public Utilities Fortnightly. February 18, 1988, pp. 16-23. 89. IEEE Working Group Draft Report, "Proposed Data Structure for Exchange of Power System Analytical Data: IEEE Transactions on Power Systems. Vol. PWRS-1, No. 2, 1986, pp. 8-16. 90. U.G. Kni&ht Convenor, CIGRE Study Committee 32 (Operation), Working Group 01 (Control in Emeraency), Aids for the Emergency Control of Power Systems -Part I, The Present State and Part ll, Near-Term Projections. Papen AI0-002-6 and AB0-003-4, presented at the IEEE PES Winter Power Meetina, New York, February 1980. 91. R.E. Kennon, Upratin1 Options for Lines and Rights of Way, 1987 IEEE PES Winter Power Meetina, Panel Session on 9Technical Limitations to Transmission System Opentions. 92. G.P. Andenon, "Uppade 115 kV Line on Existing ROW. and Disgjbution, May 1985, pp.68-69. Transmission 93. M. Brochat and R.E. ClaytOn, compaction Techniques Applied to Subtransmission Line Uprating, 41.6 kV to 115 kV: IEEE Power Apparatus and Sv,teim, PAS-100, No. 4, April 1981, pp. 1959-1965. 94. J.F. Aldrich, R.A. Fernandes, L.W. Vicks, H.H. Happ, K.A. Wirgau, "Benefits of Voltaae Schedulina in Power Systems, IEEE Transactions on Power Apparatm and SystemsVol. PAS-99. 1980, pp. 1101-1112. 95. R. Mota-Palomino and V.H. Quintana, "Sparse Reactive Power Schedulina by a Penalty Function-Linear Programmina Technique.IEEE Tranyctions on Power Systems, Vol. PWRS-1, 1986, pp. 31-39. 8
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