ML19257B609
| ML19257B609 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/30/1972 |
| From: | PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC, PENNSYLVANIA POWER & LIGHT CO., Public Service Enterprise Group |
| To: | |
| Shared Package | |
| ML19257B607 | List: |
| References | |
| TASK-TF, TASK-TMR NUDOCS 8001170776 | |
| Download: ML19257B609 (14) | |
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SCilEDULING AND IJILLING OF llULK POWER TRANSFERS I
PRACTICES OF Tile PENNSYLVANIA-NEW JEI!SEY-MARYLAND INTERCONNECTION PREPARED FOR AMERICAN POWER CONFERENCE APRIL 1972 h
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T. P. UCLCil MANAGER ADMINISTilATIVE ASSISTANT Tile PENNSYLVANI A-Nhu JLRSEY-IfARYIJ,!:D INTERCONNECTION PJh CONTROL Cl.NTER VALLEY FORGE, PENN.'iYLVANI A 8001170 7 76 c-ll
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SCllEDULING AND lill.l.ING _OF llUIK POWER TRANSFERS PIIACTICES OF T!!E PENNSYINANI A-NEW JERSEY-MARYLAND INTERCONNECTION W. S. KLEINFAC11 T. P. WEILH MANAGER ADMINISTRATIVE ASSISTANT I
INTRODUCTION The bulk pcuer supply operations of tucive investor owned electric utilities serving 20.8 million peopic in the states of Pennsylvania, New Jersey, Maryland, Delaware, Virginia, and the District of Columbia are coordinated under the terms of the Pennsylvania-New Jersey-Maryland (PJM) Interconnec tion Agreement. The service area of PJM is shown in Figure 1.
This Interconnection had its beginning in 1928 when three companies of PJM pioaccred the concept of coordinating their bulk power supply operations under a formal agreement.
In 1956, the pool expanded to include the twelve companies listed below in the coordinated operation f PJM.
For purposes of operations some of the companies operate in groups
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as indicated in the listing.
Public Service Electric and Gas Co. (PS)
Philadelphia Electric Co. (PE) Group h
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Atlantic City Electric Co.
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Delmarva Power & Light Co.
Pennsylvania Power & Light Co.(PI,) Group Pennsylvania Power & I,ight Co.
UGI Corporation L917 059 Italtimore Can and Elcetric Co. (BC)
General Public Utilities (GPU) Corp.
Jersey Central Power 6 ! ight Co.
Metropolitan EJ1 son Co.
New Jersey Pouer & Light Co.
Pennsylvania Electric Co.
Potomac Clectric Power Co. (PCPCO) i Perhaps the most important concept of the PJM Interconnec tion is its j
operation as a single system with central dispatch and free flowing ties m
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t between member companies. The PJM Control Center located in the north-
't western suburbs of Philadelphia provides the central dispatch using a high speed digital computer system backed up by an analog computer system. Control signals developed at the Center are transmitted via data links to dispatch centers of the member companies.
Through this control process the operation of 526 generating units at 112 stations throughout the pool is coordinated.
The summer capability of those stations now totals 32,230 FM, 757. of which is fossil fueled steam,
'167. is combustion turbines and diesels, 7% hydro, and 21 nuclear.
The 1971 peak load on the PJM system was 25,529 FM which occurred in July.
i The backbone transmission system of PJM consists of 880 miles of t
j 500 KV lines to which the Keystone (1640 MW) and Conemaugh (1700 FM) i
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mine-mouth generating plants are connected.
Both those plants and the 500 KV transmission system are jointly owned by companies of PJM.
Inter-l lacing the pool are 150 miles of 345 KV and 3600 miles of 230 KV trans-t mission lines.
I PJM has interconnection agreements with four neighboring systems:
The Cleveland Elcetric Illuminating Company (CEI), the Allegheny Power I
i System (APS ), the Virginia Electric and Power Company (VEPCO), and two f
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3 companies of the New York Power Pool (NYPP)--Niagara Mohawk Power Corporation and New York State Electric and Gas Corporation. A total of 23 tie lines interconnect PJM with those four systems, including four 500 KV interconnections - three with APS and one with NYPP.
The inter-connections between companies of PJM and with their neighboring systems are shown in Figure 2.
The Control Center digital computer and data transmission system monitors at approximately two second intervals the power flows on all interconnecting ties to neighboring systems and systen frequency, and from this data develops area control signals.
The computer system also monitors the power flow at approximately 300 points throughout the Interconnection approximately five times each minute.
Four times each hour the computer performs an analysis of system power flows by simulating the effect of outages of selected generators and transmission lines to j
t determine whether, overload conditions would exist should such outages occur.
l This analysis routine can be performed more f requent ly at the option of the j
dispatcher. The PJM Control Center is responsible for advance approval of planned maintenance outages of generating units and transmission lines.
Ilefore approval is given, this same computer analysis routine is used to evaluate system operating conditions assuming the outages as planned.
I Additional applications of the Pat computer systen are described in y
Reference 2.
I OPERATIONS AND ACCOUNTING U
The PJM Interconnection is operated at all times to maintain a bulk power supply reliability such that the failure of any one facility will not result in cascade trippin>; of other generation or transmission IJ917 061
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facilitics. Available generating units are scheduled for operation in advance of specific daily peak periods to supply the load and to provide sufficient operating reserve, adequately distributed throughout the pool, and with a mix of unit types such that the pouer requirement of the pool can be generated at the lowest possibic cost.
Of f-line computer analysis of expected system conditions provides the guidance required in the scheduling.
There is no advance scheduling of energy interchange between companics of PJM.
Energy flow throughout the pool results from the loading of scheduled generating units as directed by the Control Center - by control signals and voice dispatch.
Generation is controlled to supply the pool load requirements at the lowest overall cost to the companies operating I
as a single system.
Such economic dispatch is at all times subservient to operating constraints determined by the computer system monitoring program described above.
Outages of generating units and transmission lines may at times constrain economic dir. patch, in which case un economical generation is operated to maintain a reliable bulk power supply system, f
Under the terms of the PJM Interconnection Agrecment, two types of power interchange - operating capacity and energy - are accounted for.
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Operating capacity is scheduled before-the-f act and is accounted for on 1-.Ll ll(Vi !
the basis of the capacity scheduled to operate on cach member company's
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- gj system, each company's own estimate of its peak load in a given period, 3,bi l '{P[
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and cach company's share of the PJM operating reserve requirement based on forecast conditions. Energy interchange between companics is determined I
and accounted for hourly aftet;-clye-fact. The basic principle of PJM accounting procedures is that the savingn resulting from the coordinated scheduling and single-systna operation are shared equally by the t
< suppliers and receivers.
OPERATING CAPACITY SCllEDULING AND IUI.t.ING Available generating units are scheduled for operation each day to peak load and reliability requirements while optimi: ing economy of meet power supply during four periods of the day - morning, afternoon, evening, and after-midnight.
(Three periods on Saturdays, Sundays, and holidays -
daytime, evening, and after-midnight.) The scheduling is coordinated by the PJ!1 Control Center which receives estimated peak loads for those periods from each company together with each company's determination of its capacity which must operate. The Control Center then calculates the Interconnection peak load for each period to which it adds a component for operating reserve.
The operating reserve required in cach period is pre-determined, for the season of the year and the magnitude of the load, by probability calculations which consider past experience of load f orecasting error and forced outage incidence of the equipment availabic for generation.
The Control Center then determines the amount and type, if any, additional capacity which must be operated to maintain reliabic system operation while optimizing economy, and requests the companies to operate such equipment for the Interconnection.
Schedu12s are revised as necessary in advance of peak periods to reficct changes in load estimate or capacity availability so as to begin a peak period with the required operating reserve.
As a result of such scheduling, some coupanics vill provide more than their share of the Interconnection operating capacity requirement and other companics Icss.
Such interchange is accounted for daily on the basis of the cost to operate the scheduled equipment in excess of the ovaer company requirement, compared to t.he cost which would have been incurred by the f
4 ' company operating less than its requirement.
Billing for such tranactions is midway between the two costs and results in the savings being divided equally between supplying and receiving companies.
If a receiving company has no equipment available on which to determine its rcplacement value, it will use the weighted average cost of the highest cost equivalent capacity operated on the PJM system or received by PJM f rom neighboring systems to meet its requirement, p lu s 2 07..
The costs involved in the accounting for operating capacity are daily costs of start-up, operation at minimum energy output, shut-down, maintenance and operating labor.
ENERGY INTERC11ANGE AND BILLING At the end of each hour each company determines the amount of energy it delivered or received by calculating the net total of the net hourly integrated metered flow on all its interconnections, and adjusting that total for its share of generation jointly owned with other cunpanies and its share of the 500 KV transmission system losses. This information is transmitted to the Control Center together with the cost of energy delivered or the replacenent value f or energy received based on the cost which would have been incurred if generated on its own equipment.
Billing for energy transactions is determined hourly by an accounting procedure wherein a supplying company receives payment at a rate midway between its cost rate and the weighted average replacement rate of all receiving companies and conversely, a receiving company is billed at a rate midway between its replacement rate and the seighted average cost rate of all supplying companies.
(The marhematical procedure is explained in a PJM paper presented at the 1958 American Power Conference - Reference 1.)
If a receiving company has no equipment available on which to determine O
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. 'its replacement value, it will use the weight ed average cost of the highest cost energy generated on the PJM system or received by PJM from neighboring systems to supply its requirement, plus 20%.
The costs involved in energy interchange accounting are the incremental cos ts of fuel, maintenance, labor, and others, such as generation taxes.
INTERCilANGE WITil NEIC11 BORING SYSTDIS All power transactions with neighboring systems are scheduled in advance by the Control Center and are of the same two types - operating capacity and energy. The agreements provide for both economy and i
i emergency operating capacity transactions.
Ilowever, nearly all trans-actions to date have been in the emergency category wherein the receiving system has no available equipment on whic't to determine its replacement value.
Such transactions are scheduled in advance of a peak period by h
the respective system dispatchers and are billed on a daily basis at the f
cost of supply plus 10%.
Energy t an sactions are scheduled in advance of each hour and are either economt, emergency, or a combination of both.
Hourly rates quot.ed by system dispatchers for economy schedules become t.he basis for the billing on a split saving basis.
Emergency energy transactions, wherein the receiving company has no equipment on which to determine its replacement value, are billed at the cost of supply plus 107..
Energy transacticus are accounted for hourly. Changes in schedule can be made at any time and integrated to determine the hourly amount.
Under the terms of the PJM Agreement, all transactions with neighboring l
i systems are considered pool transactions. Consequently, each PJM company is
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'l allocated 1/6 of the out side interchange in bot h amount (MN) and cost or value before the PJH int.erchange accounting described above is computed.
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'fhis procedure has the effect of balanc!ng the interchange between PJM companies.
Since each company is alloca*.ed 1/6 of the outside trans-actions, it is also allocated 1/6 of the bill or payment for such transactions.
INSTALLED CAPACITY ACCOUNTING Each member company under the PJM Agreement is obligated to provide sufficient installed capacity a) to carry its diversified peak load plus its share of the Interconnection reserve requirement, and b) to permit maintenance of its generating equipment.
Determination is made after-the-fact on a veckly basis of each company's position in meeting its insta.lled obligation. Deficiencies are accounted for through payments made to a company having capacity in excess of its installed obligation.
The present rate for such. deficiency payment is $12.48 per kilowatt on an annual basis or 24c per kilowatt on a weekly basis.
This rate represents the net cnnual cost of new generating capacity currently being installed on the PJM system.
Such net cost is the fixed annual charge on the required plant investment less the value of the operating capacity and energy retained by the owning company.
The accounting procedure must recognize a company's obligation to provide capacity to carry its onnual peak load plus reserve and also to permit maintenance.
It is, therefore, separated into two components:
i accounting for annual peak requirements, and accounting for average ucekly load conditions.
In computing the former, each company's peak load during the past 52 weeks, less one-sixth of the PJM load diversity in that period, plus its share of t.he Interconnect ion reserve requiremen t, is compared each week to its total installed capacity.
In computin the latter obligation,
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9 cach company's peak load each week, less one-sixth of the PJ.!' load diversity in that. week, plus its share of the Interconnection reserve resluirement, is at available for compared to its installed capacity less any capacity not service at the time of the Interconnection peak for that week.
This second computation utilizes a moving 52-week average as the basis for determining i
deficiencies.
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?!ONTilLY BIILING FOR INTERCilANGE TRANSACTIONS t
All of the accounting described above is computed on one of the two 1121 360/50 computers at the PJM Control Center.
Daily output sheets summarizing the operating capacity accounting by periods and the energy I
accounting hourly are distributed to the member companies.
The installed 3
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i capacity accounting is computed weekly. A separate billing program combines e
the results of these three accounting procedures and develops the monthly bill which is rendered by the fif th working day of th, f ollowing month.
Total billing in 1971 for all interchange transactions among the member companies of PJM totalled approximately $105,000,000.
The major portion of this total was f or energy interchange which amounted to approximately 7,800,000 FMI.
A total of 689,000 MW of operating capacity was interchanged.
During the past five years the annual total accounted for savings resulting from power transactions among PJM companies averaged approximat.ely $31,000,000 which is c.31e evidence of the value of inter-connected operation with central dispatch and free flowing ties.
FUTURE CONS 111ERATIONS Most of the accounting procedures described above have been in ef fect since 1956 when the present PJM Int erconnection Agreement l>ccame effective.
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. Supplements have been made to the Agreement from time to time to recognine changes, such as the interconnection agreements with neighboring systems which were placed in effect between 1962 and 1965.
In recent years, major changes have taken place in system operation which have increased the amount and cost of power interchange among interconnected systems. Those changes include the higher capacity interconnections; the lower than i
planned reserve capacity caused by unpredictable delays in completing t
construction of new f acilities; the increased installations of combustion i
turbines (which have high operating costs) to of f set delays in construc tion I,
i of base load units; increased cost of fac1 as a result of inflation and pollution regulation; the increased size of generating units; and the 4
increased incidence of forced outages of relatively new generating units.
The following comparfron of the mix of unit types installed and planned on PJM illustrates the size.,ble changes experienced in the past five years
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M4 Intercor.nection Percent of Installed Capacity by Typ_e d\\
qp gh 1966 1%1 1981 Steam - Fossil 90 76 47 9k Steam - Nuclear 2
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Co,nbus t. Turbine 1
14 12 Ilydro 7
7 6
Purchase 2
1 10 7 068 100 100 100 It is the intent of the PJM companics that the accounting procedures for power interchange return cost s to the suppliers plus an equitable share nf the saving, resulting from Interconnected operation.
For this reason,
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. PJM accounting procedures are continually scrutinized and some revisions can be expected in the near future.
The rapid grcwth expected in nt:1 car fueled generat ing unf tu in the near future poses another problem in accounting for interchange.
Those type units require an extended outage (one month) for re-fueling at pre-determined intervals for optimum utilization of the nuclear fuel.
Obviously, such re-fueling outages will be coordinated f or the units installed on the PJM system.
The problem will arise when the scheduled re-fueling of a nuclear unit of Company A must be changed because of system reliability considerations resulting from a forced outage of a nuclear unit of Company B.
Since the cost of energy generated on a nuclear unit is contingent upon the expected fuel burn-up during a current cycle, any change in this cycle can have substantial effect on production costs of that unit for the previous and the next operating cycle.
Furthermore, the mechanics of re-fueling require advance fabrication and enrichment, changes in which may be impracticable, but in any event, could be very costly.
Therefore, the relative ef f ec t on one company's nuclear production costs resulting from changes in schedule caused by another company in the Interconnection appears now to require a special accounting procedure scparate from present procedures for economy or emergency interchange. A special committee of PJM company representatives has been working for nearly a year on the development of criteria for scheduling nuclear re-fueling and the associated accounting requirements.
t917 069 CONCLUS ION The prasent PJM accounting procedures have been proven satisfactory thr<.igh 16 years of experience.
They are concise in that y tuo classer N h 9
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. of power interchange are accounted for - operating capacity and energy.
Accounting procedures must be flexible to account equitably for changing system operations and, theref ore, must be continually reviewed and revised accordingly.
Regional operation of interconnected systems has resulted in increased interchange of power uhich has benefited all, particularly the customer, in maintaining electric service during periods r
of generating outages. Such transfers will undoubtedly increase in the future and accounting procedures for such transfers must also be reviewed j
continually to assure equitabic treatment for both suppliers and receivers f
of power.
REFERENCES on the 1.
Phillips, H. U., " Scheduling and Billing Interchange Pennsylvania-New Jersey-Maryland Int erconnec tion" paper
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presented at the Amer ican Power Conf erence, Chicago, Illinois, j
March 26-28, 1958.
2.
Kleinbach, Steuar t, Uclch, Uooduard, "The PJM Con trol Center" prepared for NAPSIC's Second General Meeting, May 4-5, 1971.
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