exhibit no.5 atc/ttc calculations andmethodology ... · atc = a service above the ttc for agiven...

Exhibit No.5

ATC/TTC CALCULATIONS AND METHODOLOGY STATEMENTSFROM ISO-NEAND PJM

ISO-New England - TTC/TRMIATC Document

Total Transmission Capability (TTC),

Transmission Reliability Margin (TR1VI), andAvailable Transmission Capability (ATC)

Introduction

This documentincludesthe following information:

• Basic explanationsof TTC, ATC, andTRM

• List ofNEPOOLinterfacesandforecast/postingresponsibilities

• Methodsof determiningTTC andTRM for eachinterface

• Informationaboutthepostingof TTC andATC valuesfor theNEPOOLinterfaces,including the timeframesandfrequencyofupdates

Basic Conceptsand Definitions

Total Transfer Capability (TTC)

NERC Definition The TotalTransferCapability(TTC) for aninterfaceis thebestengineeringestimateofthe total amountof electricpowerthatcanbetransferredoverthe interfacein areliablemannerin agiventime-frame.

Basisfor TTC TTCs forNEPOOLinterfacesareforecastby the ISO basedonthermal,voltage,orstability limitationsoftheties thatcomprisetheinterface. Powerflow analysisis usedto ensurethatphysicallimitswill not beviolatedfor crediblecontingencies.

FutureForecasts The TTC forecastfor periodsbeyond35 daysout is basedon seasonaloperatingstudiesthattakeinto accountanticipatedpeakloadsandgeneratormaintenanceschedules.

Within 35 days,abaseTTC is calculatedfrom historical“all linesin” datathattakesinto accountseasonalloaddistributions. The baseTTC is adjusteddaily into aforecastvaluethat accountsfor:• forecastloads• actualandscheduledtransmissionandgeneratoroutagesin

NEPOOLandneighboringsystems

Revision#2, April 2000

ISO-New England - TTC/TRMJATC Document

• changesin facility ratings• anticipatedloading of generators• anticipatedinter-Areaschedulesusedfor daily andweekly

securityanalysis.

Variationsacross Factorsusedin calculatingTTC for eachof theNEPOOLinterfacesinterfaces vary. Briefdescriptionsofthesemethodsaregiven in Section4.

ISO/Transmission TheISO calculatesthe forecastTTC fortheNEPOOL interfacesonProvider behalfof the transmissionproviderswithin NewEngland.Responsibility

Individual TransmissionProvidersusethe forecastTTCs accordingtotheir OASISpostingrequirements.

TransmissionReliability Margin (TRM)

Definition The TransmissionReliability Margin (TRM) is the portionofTTCthat cannotbeusedfor reservationof firm transmissionservicebecauseofuncertaintiesin systemoperation.ISONew Englandusesthe TRM to minimize theneedto curtail firm transmissionservice.

TheTRM is availablefor reservationofnon-firmtransmissionservice.Note thatwhenTRM = TTC, no firm transmissionreservationscanbemadeon the tie. Non-firm reservationscanbemadeup to the valueof TTC.

Variability of TRM TheTRMs areinterface-dependent,direction-specificandtime-dependent.Methodsusedto determineTRM vary for eachof theNEPOOLinterfacesaredescribedin Section4.

ISO/Transmission TheISO calculatestheforecastTRM for theNEPOOLinterfacesonProvider behalfof the transmissionproviderswithin New England.Responsibility

Individual TransmissionProvidersusethe forecastTRMs accordingto theirOASISpostingrequirements.

Available Transfer Capability (ATC)

Definition Firm Available TransferCapability(Firm ATC) for an interfaceis theof capabilityfor firm transmissionreservationsthatremainsafterFirm ATC allowing for existingfirm commitmentsandthe TRM.

Mathematically,Firm ATC is calculatedusing the equation:

Firm ATC = TTC — TRM — Existing Firm Commitments*.

Revision#2,April 2000 2

ISO-NewEngland - TTC/TRM/ATC Document

* Existing Firm Commitments consistof, Firm transmission

requestsin the following status,Confirmed,AcceptedandStudy.

Definition Non-Firm AvailableTransferCapability (Non-FirmATC) for anof interfaceis thecapabilityfor non-firmtransmissionreservationsthatNon-Firm ATC remainsafterallowing for existingcommitmentsin theConfirmed

andAcceptedstatus. Mathematically,Non-Firm ATC is calculatedusingtheequation:

Non-FirmATC =

TTC — ExistingFirm & Non-Firm Commitmentsin theConfirmedandAcceptedStatus.

StudyReservations Requestsfor servicethatarein the Study StatusareexcludedfromthecalculationofNon-FirmATC.

Non-Firm TheISO will onoccasionallow Customersto reservehourly non-firmATC = a serviceabovetheTTC for agiven interfacein orderto minimizethenegative degreeofnon-use,aswhenenergyflows arenot scheduledagainstanumber transmissionreservation.In suchcases,theNon-Firm ATC equation

would yield anegativevalueforNon-Firm ATC.

ATC Releasetiming Thevariousclassesof TransmissionServicehavedifferenttimingtables constraintsassociatedwith each.For informationon thewindowof

time openfor requestingeachclassof TransmissionServicepleasereferto TablesTi (Firm Service)andT2 (Non-FirmService)of TheGeneralBusinessPracticesfoundat,http://www.iso-ne.com/transmissionservicesand generationinterconnection/documents/TariffSpecific BusinessPractices/GeneralBusinessPractices/index.html

Additional Release Hourly Non-FirmServiceis releasedpertableT2 of the Generalof Hourly Non-Firm BusinessPractices.Additionally, asofthe noondaily tradingService deadline,calculationof ATC forNon-Firm Hourly Serviceis based

on themaximumavailability of theenergyto bescheduledasopposedto the reservedtransmissionservice. This effectivelyreleasesanyunscheduledtransmissionserviceup to the TTC (nooverbookingis allowed).


ISO-NewEngland - TTC/TRMJATC Document

Capacity BenefitMargin (CBM), NotIncludedin NewEngland

ForNEPOOL,‘Existing Firm Commitments’meanstheexistingfirmtransmissionreservations.NEPOOLdoesnot includeaCBMcomponentin anyATC calculations,becausetheCBM is reflectedinthecapacityrequirementsof load-servingentities.

If thecapacityplanningmethodsatNEPOOLchangein thefuture,• the valueoftheCBM componentin theATC calculationswill be re-

evaluated.

ISO/Transmission TheISO calculatesandupdatesFirm andNon-FirmATCsfor serviceProvider with theNEPOOLRTG. ATC for theotherinterfacesis calculatedResponsibility andupdatedby thetransmissionproviderswho postthoseinterfaces.



NEPOOL Interfaces

Thetenexternalinterfacesfor whichATC valuesarecurrentlypostedon theNEPOOLOASISnodearelistedin thetablebelow. Someoftheseinterfacesconsistofasingletie andothershavemultiple ties.

TheISO determinestheTTC andTRM for eachinterface.TheTransmissionProvidersdeterminethe ATCs basedon existingcommitmentsandpost thevaluesfor TTC andATCs on theirindividualOASIS sites.

Table: NEPOOL Interfaces and TransmissionProviders

Interface TransmissionProviders Comments

NewYork/New England NEPOOLRTG

NYPA/Vermont NEPOOLRTG PostedassubsetofNY-NE

LILCO/Connecticut NEPOOL RTG PostedassubsetofNY-NE

Hydro-Quebec-SandyPond Individual ownersofthehydetie PhaseII, ATC forecastedbyindividual owners

Hydro-Quebec-Comerford Individual ownersof thehydetie PhaseI, ATC forecastedbyindividual owners

NewBrunswick-MEPCO Maine ElectricPowerCompany(MEPCO)

ATC forecastedby MEPCO

NewBrunswick— MPS Maine PublicServiceCompany(MPS)

TTC andATC are forecastedby MPS

Hydro-Quebec-CUin VT CitizensUtilities (CU) HQ Block Load;TTC andATCare forecastedby CU

llydro-Quebec-}lighgate CentralVermont Public ServiceCorporation(CVPS)

MEPCO- New England NEPOOLRTG; MaineElectricPowerCompany(MEPCO)

Separatepostingsby NEPOOLRIG andMEPCO

Revision#2, April 2000 5


Thissectiondescribesconsiderationsusedin determiningTTC andTRM for eachofNEPOOL interfaces.

TheNewYork/New Englandinterfaceconsistsof eight ties:.

1. Plattsburgh-SandBar (PV-20) 115 kV line

2. Whitehall-Blissville(K37) 115 kV line

3. Hoosick-Bennington(K6) 115 kV line

4. Rotterdam-BearSwamp(E205W)230kV line

5. Alps-Berkshire(393)345 kV line6. PleasantValley-LongMountain(398)345 kV line

7. Northport-NorwalkHarbor(1385)138 kV cable

8. Smithfield - Salisbury(690)69 kV line

Basevaluesof theTTC for this interfacearecreatedutilizinghistorical“all lines in” transferlimit data.This datatakesinto accountsuchdiversefactorsasseasonalloaddistributionandfacility ratings,loadlevels,thermalandstability limits, pumpedstorageoperation,andotherfactorsthattypically influenceinterfacetransferlimits.

Historical load data,which is categorizedby day type(weekday,Saturday,andSunday),allowsbasevaluesto bedeterminedfor 24hoursperday for all monthsoftheyear.

TTC & TRM TTC & TRM valuesareshownin thetablebelow.Table: TTC and TRM for New York — NewEngland Interlace

Direction Quantity Value Comments

NY to NE TTC Basedon powerflow studiesorhistoricalvalues

TRM 200MW

NE to NY TTC Basedon powerflow studies

TRM Days I — 12:greaterof 15%or 200MW;

beyond12days: 400 MW

TTC and TRM for NEPOOL Interfaces

New York-New England Interface

Tie Lines

DeterminationofTTC



NYPA-Vermont Interface

Thevaluesof TTC andTRM forNYPA to Vermontasdeterminedbythe methodsstatedbelowarebasedon thecapabilityof thePV-20line. Theyarethevaluesthat wouldapplyto the interfacetakenonits own. However,valuesof TTC andTRM for NYPA to Vermontarepartof theoverall capabilityof theNew York to New Englandinterfaceandmaybe reducedaccordingly. This is explainedwith anexampleatthe endof thesection.

Table: TTC and TRM for NYPA - Vermont Interface

Direction Quantity Condition Value/Method

NYPA toVT

TIC Summer(5/1-10/31) Up to 140MW

Value is basedon operatingproceduresfor PV-20

Winter (11/1-4/30):Highgateto VT> 200MW

Up to 140 MW

Winter (11/1-4/30):}{ighgate to VT � 200MW

Up to 155 MW

TRM Summer TRM =0

Winter: Highgateto VT>200 MW

TRM = 0

Winter (11/1-4/30):Highgateto VT � 200MW

TRM = 0

VitoNYPA

TIC . TFC=0

Flows in thisdirectionareon anemergencybasisonly

TRIVI TRM = TIC

Examplesof TheATC on theNYPA — Vermontinterfacemaybe limited by theLimitation ATC for theNY to NE interfaceasshownin thefollowing firm ATC

examples.

NYPA/VTATC�NY/NEATC

Suppose:. TTC for NYPA-VT Interface= 140 MW


ISO-New England - TTC/TRM/ATC Document

• Firm reservationsonNYPA-VT = 100 MW• TRM for NYPA-VT = 0• Firm ATC= TTC- TRM — Firm commitments

If ignoring theNY to NE interfacecapability• FirmATCforNYPAtoVT=(140-O- 100)=4OMW

If Firm ATC forNY to NE Interfaceis greaterthanFirm ATC forNYPA to VT

If FirmATC forNY-NE is 500 MW• FirmATCforNYPAtoVT=(140-0- 100)=4OMW

If FirmATC forNY to NE Interfaceis lessthanFirm ATC forNYPA to VT,

If Firm ATC for NY-NE is 30 MW• Firm ATC for NYPA to Vermont= Firm ATC for NY to NE =

30 MW, since30 MW is lessthanthe40 MW calculatedabovefor NYPA - VT Firm ATC

LILCO-Connecticut Interface

Thevaluesof TTC andTRM for the LILCO — Connecticutinterface

asdeterminedby themethodsstatedbelowarebasedon thecapabilityof the 1385cable. Theyarethevaluesthatwouldapplytothe interfacetakenon its own. However,valuesofTTC/TRM forLILCO — CT arelinked to the overallcapabilityoftheNew York toNewEnglandinterfaceandmaybe reducedaccordingly. Thetreatmentwith respectto theNY - NE interfaceis similar to thatoftheNYPA-VT interface.

LILCO/CTATC�NY/NEATC

TTC andTRIVI valuesfor this interfaceareshownin thetable.

Table: TTC and TRM for LILCO — ConnecticutInterlace


LILCO toCT

TTC LTC rating ofcable

Thermallimitation for flow onthe 1385 cable.

TRM 0MW

CTtoLILCO:

TIC LIC rating ofcable

ITC is thesamefor bothdirections



TRM TIC-200

New Brunswick (NB) - MEPCO Interface

Basevaluesof theTTC for this interfacearedeterminedutilizinghistorical“all lines in” transferlimit data.Thisdatatakesinto accountsuchdiversefactorsasseasonalloaddistributionandfacility ratings,loadlevels,thermalandstability limits, andother factorsthattypically influenceinterfacetransferlimits.

TheNew Brunswickto NewEnglandinterfacehasaminimumflowneededto maintainsystemreliability for sourcecontingenciesin theMaritimes.

Notethatthis interfaceis not postedby theNEPOOLRTG; it ispostedby MEPCO.

Table: TTC and TRM for New Brunswick — MEPCO Interlace


NB to NE: TTC The TTC is basedon the stabilitylimit of 700 MW

TRM As postedby theTransmissionProvider(MEPCO)

NE to NB TT’C: Basedon powerflow studies

Typically zeroor flows requiredfrom NB to NE dueto minimumtieflow reliability requirements

TRM As postedby theTransmissionProvider(MEPCO)

MEPCO-New England InterfaceValuesof TTC for this interfacearebasedon thermallimitationsderivedfrom powerflow analysiswhichreflectsbothsummerandwinter facility ratings.

Valuesareshownin thetablebelow.

Table: TTC and TRM for MEPCO — New England Interlace


MEPCOtoNE:

TIC Basedonpowerflow studies

Postedby bothNEPOOLRTGandMEPCO.

TRM TRM =ITC-700



Highgate-Vermont

Table: TTC andTRM for Highgate to Vermont


HighgatetoVT

TTC 225 MW limit

TRM As postedby theTransmissionProvider(CVPS)

VT toHighgate

TIC TTC= 0 Flowsin this directionareon anemergencybasisonly

TRM As postedby theTransmissionProvider(CVPS)

Hydro-Quebec to SandyPond

This is the interfacefor PhaseII.

Table: TTC and TRM for Hydro-Quebecto Sandy PondInterlace


HQ to SandyPond

TTC Up to 2000MW

TTC basedon thePhaseII modeofoperation(isolatedor synchronous)andon transferlimitations in NEPOOL,PJM, orNYPP

TRM As postedby the individualTransmissionProvider

SandyPondto HQ

TIC Up to 1200MW

TITCs are basedon theability of theHydro-Quebecsystemto sustainasourcecontingency


NOTE: PhaseI & II cannotoperatesimultaneously.Normaloperationis overthePhaseII facility..



Hydro-Quebecto Commerford

This is the interfacefor PhaseI.

Table: TTC and TRM for Hydro-Quebecto Comerlord Interface


HQ toComerford

TTC Up to 690 MW.

Typically zeroif PhaseII is inservice

Basedon the equipmentratingof 690MW for import toNewEngland

IRM As postedby the individualTransmissionProvider

ComerfordtoHQ

TFC Typically zero For emergencyexportsto HQ




Determination and Posting of TTC& ATC

Location ofPostings

TTC andATC valuesfor all NEPOOL PTFinterfacesarepostedontheNEPOOLOASISnode. ThevaluesareaccessedthroughtheOASISsiteoftheTransmissionProviderasidentifiedin thetable,“NEPOOL InterfacesandTransmissionProviders”. Someinterfacesarepostedby morethanoneTransmissionProvider.

Updatesto TTC and ATCTTC andTRM valuesarecalculatedandpostedfor eachofthefollowing time frames:

• Hourly• Daily• Weekly• Monthly• Yearly

BaseTTC valuesforthe longertermpostingsaredeterminedusingan “all lines in” normalsystemconfiguration. Closerto realtime,changesto thenormalconfigurationasaresultofscheduledmaintenanceor unscheduledoutagesareknownandcanresultinmoreor lessrestrictivetransferlimitations.

Shorttermanalysismaybe performedto assesstheeffectsofoutagesandotherchangeson baseTTCs. Adjustmentsto thebaseTTC valuesaremadeto nearertermvaluesasappropriateto reflectthe changesin limitations.

Updatesto TTC The ISO evaluatesall TTC values,with theexceptionof yearlyvalues,for eachinterfaceaminimum of onceperbusinessdayandwheneverchangesin systemconditionswarrant.Forinterfacespostedby providersotherthantheNEPOOLRTG,the ISOprovidestheforecastTTC for interfacesto thetransmissionproviderswithinNewEngland,as indicatedin the tableentitled“NEPOOLInterfacesandTransmissionProviders”onpage5 of this document.

Updatesto ATC TheISO calculatesandupdatesATC for servicewith theNEPOOLRTG severaltimeseachdayfor thenextday andthetime framebeyond,andasneededdue to unforeseenchangesin systemconditions.


ISO-New England - TTC/TRM/ATC Document

TheISO hasaback-endapplicationthatdynamicallyrecalculatestheATC andupdatesthe OASISpostingaseachtransmissionreservationrequestwith theNEPOOLRTG is confirmed.

ATC for the interfacespostedby othertransmissionprovidersiscalculatedandupdatedby thosetransmissionproviders.

PostedTTC and ATC values

Hourly TTCs & Twenty-four(24)hourly TTC andNon-Firm HourlyATC valuesareATCs: providedfor the currentday,plus thenext11 days,for each

interface.

Adjustmentsmadeto thebaseTTC valuesfor postedinterfacescan

beseenin hour-by-hourdetail.

Daily TTCs & TTC, Firm ATC, andNon-Firm ATC valuesfor thecurrentdayplusATCs: thenext34 daysaresummarizedfor all interfaces

TheTTC valuesfor thefirst 12 daysin this groupareadjustedforhourly maintenanceanddetailscanbeviewedin the HourlyTTCsection. Days 13 through35 usehistoricaldatabaseTTC values.

Weekly TTCs & TTC, FirmATC, andNon-firm ATC valuesareshownfor theATCs: currentweekplus thenext12 weeksfor eachinterface.

A weekalwaysstartsat 0001 onaMondayandendshourending24on the following Sunday.The TTC valueshownis the minimumvaluewithin thedefined7-dayweek.

Notethatthe TTC valuesfor thefirst 5 weeks(madeup of thecurrentweekplusthenext4 weeks)will reflectadjustmentsmadefor knownhourly or daily maintenance.Theremainingweeks(6through13) useTTC valuesfrom thehistoricaldatabaseexceptifmaintenanceis scheduledthatwould effectanyofthoseweeksintheirentirety.

Monthly TTCs & Themonthly TTC andATC valuescoverthecurrentmonthandtheATCs: next12 monthsfor atotal of 13 calendarmonths. Eachinterfacehas

minimumTTC valuespostedwhich arebasedon thehistoricaldatabase.

If maintenanceis scheduledfor anentiremonththeMonthly TTCs



will reflectit here.

YearlyTTCs & Valuesforthe YearlyTTC reflect2 yearsbeyondthecurrentyear.ATCs: TTC valuesfor eachinterfacearenotpostedon aseasonalbasis,but

ratherindicatetheminimal valuebetweenSummerandWinter

analysis.

Referencedocuments/resources

FurtherinformationaboutTTC/ATC andthe criteriagoverningATC/TTC within NEPOOLis availablefrom the followingdocuments:

• NERC Policy 3, Interchange.SectionE: TransferCapability

• AvailableTransferCapabilityDefinitionsandDetermination.NERC,June,1996

• RevisedNPCCMethodologyandProcedurefor theDeterminationandPostingofAvailableTransferCapability.NPCC,1998

• NEPOOLOpenAccessTransmissionTar~ffAttachmentC.

• NEPOOLOperatingProcedure19 (0P19) TransmissionOperations


Calculation of Capacity Benefit Margin (CBM) for NEPOOL

It is the current practice of ISO New England Inc. to use 0 MW for CBM whencalculating transfer capabilities on its interconnections with other Control Areas.This practice is based on the capability of generation located within New Englandto reliably meet load and reserve requirements during most hours of the year andon the relatively low usage of NEPOOL ties for supplying loads outside of NewEngland.

Negative Firm Available Transmission Capacity

Why is the firm AvailableTransmissionCapacity(ATC) postedon the OASISa large negative number?

Earlier this yearthe NEPOOLOASISbecamefully subscribedfor Long-TermFirm IN Servicefrom New York. Additional requestsfor Long-TermServiceon thispatharein the studyqueueawaitinga SystemImpact Study. Currently therearefive requestsunderstudy.

OASISreservationsin the accepted,confirmedand studystatusareaccountedfor in thecalculationofATC. TheLong-TermServicerequestsunderstudymakeit appearthat NEPOOLOASIS is oversubscribingfirm andnon-firmservicewell into the future. This is not thecase. No servicewill be grantedtorequestsunder study until ATC is available. ATC availability couldresultfromtransmissionupgradesincreasingtheTotal TransmissionCapacity(TTC) or thereleaseof a confirmedlong-termreservation.

The studyandtransmissionupgradeprocesstakesseveralmonthstocomplete. HoweverISO-NE is requiredto honorthesestudyrequestsin thecalculationof ATC if theapplicantmeetscertaincriteria. The criteriais outlined inSection33 ofthe NEPOOLTariff andincludeschargesto fund the studyandtransmissionupgradework, bothofwhich couldbe substantial. ISO-NE is alsorequiredto honorrenewalrights for existinglong-termserviceagreementsin thecalculationofATC.

Sincetheserequestsare impactingshort-termtransmissionavailability, theTariff, Scheduling& OASIS (TSO)groupat ISO-NE hasdevelopeda methodtomakethis serviceavailableon a near-termbasis. On the first ofeachmonth, theATC calculationlooks for reservationsunderstudythat would be in servicein thenext month. For instance,on December1, any reservationunderstudywith an in-servicetimeframein themonthof Januarywould not be includedin the ATCcalculation. Only onemonthat a time is released.This openstransmissionserviceto Weekly andDaily Firm aswell asall classesof non-firm service. This calculationdoesnot allow availability ofMonthly Firm Servicesincethetimeframefor thistypeservicehasclosedby this time. Cautionmustbe exercisedin releasingthisservicetoo early sinceit is possiblethat a portionof theselong-termrequestscouldbe grantedin a shorterperiodoftime thanis currentlyexpected.

Requestscurrently understudy canbeviewedon OASIS. The effectiveMWamountsthrough the endof theyearare:

November1999 260 MWDecember1999 460 MWJanuary2000 1260 MWFebruary2000 1310 MWMarch — December2000 1410MW

exhibit no.5 atc/ttc calculations andmethodology ... · atc = a service above the ttc for agiven...

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