The purpose of this paper is to discuss the factorWord格式.docx
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1.Determinetowhichtypesofthermalgeneratingunitsambienttemperaturede-ratesshouldapply.
2.
Keyinputsandfactors:
∙thecauseofambientweatherde-rates
∙
Workgroupdiscussionandoptions:
Thegroupagreedthatthetwomostaffectingweathervariablesaretemperatureandhumidity.Thethermalgenerationtechnologymostaffectedbytemperatureandhumidityiscombustionturbines.Combustionturbines’outputdependsonairdensity,whichissignificantlyaffectedbyairtemperature.Thegroupdidnotbelievethatsteamturbinecapabilityissignificantlyaffectedbyambientweatherconditions.Theworkinggroupconcludedthatambientde-ratesshouldbeappliedto
(1)combustionturbines,and
(2)plantswhichintegratecombustionturbinesintotheirtotaldelivery,suchascombinedcyclegasturbinefacilities.
PossibleAffectsofAmbientConditionsonthermalresourcesotherthangasturbines
Ambienttemperatureaffectsallthermalgeneratingunits,althoughtheeffectwithtraditionalthermalunitsisusuallylessthanthatfoundwithgasturbinetechnology.
TraditionalthermalunitsorRankineCycleUnitsusuallyinvolveaboiler,steamturbinegeneratorandsometypeofcondenserandcoolingwatersystem.Boththeboilerandcondensermaybelimitedbyambientweatherconditions.Fortheboiler,thesizeoftheFD(forceddraft)fansorID(Induceddraft)fansmaybealimitingfactorforaunit’scapacity.
Theboilerrequiresairtobemixedwiththefuel.TheFDandIDfansprovidethisair.FanshaveaCFM(cubicfeetperminute)rating.Iftheboiler’sfuelsystemrequiresthemaximumCFMfromafantoreachcapacity,theboilerisfanlimited.Theactualheatinputtoaboilermaystillvarywithambienttemperatureinafanlimitedboiler.Densityoftheairisafunctionofambienttemperature.Thehighertheambienttemperature,thelowertheairdensityandhencethelessairisavailabletomixwiththefuel.Thefuelflowmayneedtobereducedduetothecreationofpollutantsinanoxygendeficientatmospherewhichisexacerbatedathigherambienttemperature.
Theresourcemayalsobeconstrainedduetoincreasedcoolingwatertemperature.Togenerateusefulpower,asteamturbinerequiresacondensertoremoveheatfromthesteam.Thecondenseriscooledusingcoolingwateroritmaybeanaircooledcondenser.Eitherconfigurationwillbeadverselyaffectedbyincreasedtemperature.Aswithafan,apumphasamaximumGPM(gallonperminute)rating.OncethepumpisatmaximumGPMflow,theonlywaycoolingmaybechangedisthatthecondenserissubjectedtohigherorlowertemperaturecoolingwater.Thetemperatureofthecoolingwatermaybeaffectedbythevolumeofwaterwithinaclosedloopedsystemorthedepthofawatersourceforoncethroughcooling.Ifcoolingwatertemperaturelimitsaunit’soutput,theunitissaidtobe“backpressure”limited.
ItispossiblethatthemaximumoutputofaRankineCycleunitwillnotvarywithambienttemperature.Instead,aboilermaybefuellimited.Infuellimitedoperation,themaximumflowoffuelhasoccurredbeforetheunitbecomesfan,backpressureorlimitedbyothermeanssuchaspermitrestrictionsorotherequipment.Inthiscase,theboilerhasadequatefanandcoolingwater,butmaynotgeneratebeyondagivencapacityduetofuelinputrestrictions.Ambienttemperaturewillnotsignificantlyaffectaunitthatisfuellimited.Itisalsopossiblethataunitmaybefuellimiteduptoapoint,thenbecomelimitedbyanotherparameter.
Duetothesevariability’s,aRankineCycleunitshouldperformacapacitytestasmayberequiredofgasturbinetechnologyunits.
EffectofAmbientTemperatureonDuctFiring
Ductfiringcausesacombinedcycleunittooperateinamannersimilartothatofaboilerunitandmaybesubjecttothesameconstraintsasaboilerunit.TheFDfanisreplacedbythecompressoroftheCT.SufficientairisavailabledownstreamoftheCTcombustionsystemtoallowtheductburnerstohavesufficientoxygentocombustwiththeductburnerfuel.ThefuelinputfromtheductburnersisusuallysmallascomparedtothefuelinputintoaCT.Steamturbineconstraintsaresimilartothoseexplainedabove.
3.Determinethemaximumcapability(MW)ofathermalgeneratingunitthroughaperformancetestunderknown,measurableconditions.
4.
∙usingplantinstrumentationcalibratedtoapplicablestandards
∙using“standard”operatingpracticesduringthetest.
∙thefrequencyoftheperformancetests
Theworkgroup’sdiscussionfocusedontheneedtoestablishthe“baseline”capabilityoftheunitthroughaperformancetestconductedunderknownandstandardconditions.Theperformancetestshouldbeconductedinawaythatdidnotoverstatetheunit’scapabilityundernormaloperatingconditions.Duringtheperformancetest,theunitmustbeoperatedusingonlythecontrolsnormallyavailabletotheoperator,andmustnotbetemporarilyandspecificallymodifiedjustforthetestoroperatedinawaythatcouldnotbeeasilyreproduced.Theperformancetestshouldbeconductedoverareasonableperiodoftime(severalhours)toensurethattheunitcansustainitsmaximumoutputforthatreasonableperiodoftimeandthemaximumcapabilityreportedisnotatransientvaluethatcanbeonlyproducedforaveryshortperiodoftime.
Thegroupalsodiscussedtheimportanceofusinginstrumentationcalibratedtoapplicablestandardstoensurethatallmeasurementsobtainedduringtheperformancetestareaccurateandverifiable.
Theworkgroupdiscussedthat,giventheexpenseinvolvedinsuchperformancetests,thetestsshouldbeconductedonlyperiodically–perhapseveryfewyears,andfollowingamajoroverhaul.Whileoperatingexperiencegainedovertimecouldhelpplantpersonnelunderstandhowtheunit’scapabilityvariedwiththeweather,thegroupstillfeltthatitwasessentialtoperiodicallyconductaperformancetesttoestablishthe“baseline”capabilityoftheunit.
RecognizingthattheCAISOcurrentlyhasauthoritytodocertaintestingundertheParticipatingGeneratorAgreementandCAISOTariffsection40thegroupfeltthatoneoptionwouldbefortheCAISOtoconductthetestsaspartoftheReliabilityRequirementsdetailedinSection5.1.3.2oftheCAISO’sBusinessPracticesManual,andCAISOMRTUTariffSections40.4.3,40.4.4,whichprovidefortheCAISO’sauthoritytoconductphysicalteststovalidatePmaxlimits.TheCAISOhasnotagreedtoperformthistestingfunctionbutforpurposesofdiscussingpossibleoptionsiswillingtoconsiderwhatwouldberequired.AtthecurrenttimethereislimitedtariffauthoritytorequireteststobeconductedforNQCadjustmentsbutthetariffdoesnotlistanyspecifiedintervalsnoranyspecificconditionsunderwhichthesetestswouldbeconducted.Inaddition,theprocessassociatedwithimplementinganNQCtestingprogram,asreferencedintheBPMandtariffsectionsabove,isnotdeveloped.IftheCAISOweretotakeonthistestingprocessforambienttemperatureadjustmentstherewouldbeaneedforastakeholderprocessandpossiblefilingoftarifflanguagewiththeFERC.TheCAISOisgoingthroughastakeholderprocessfortheStandardCapacityProduct,whichislookingatperformancestandards,buttodatethetopicofambientde-rateshasnotbeenincludedinthesediscussions.ThetestshouldbeconductedinaccordancewithAcceptedElectricalPracticesandtheprovisionsofPerformanceTestCodeASMEPTC-46-1996(CombinedCycleGeneratingunit)orPerformanceTestCodeASMEPTC-22-1997forgasturbinepowerplants(SimpleCycleGeneratingUnit).SeeAttachmentAforsampletestingprocedures.
5.Projecttheambientweatherconditionsattheunit’slocationconsistentwiththeweatherassumedindeterminingRArequirementsforthesameperiod.
6.
∙establishingtherelationshipbetweenambientweatherconditionsattheplantlocationandaweatherstationthathasprovidedareasonablehistoryofdata
∙projectingtheambientweatherconditionsatassociatedweatherstationsconsistentwiththeweatherassumedindevelopingtheRArequirements
∙whetherunitqualifyingcapacityvaluesshouldbedifferentforsystemandlocalRArequirements,whicharedeterminedbasedondifferentassumedweatherconditions.
Thepurposeofambientde-ratesistodeterminethemaximumoutputofageneratingunitundertheweatherconditionsthatwillbeinplaceduringthetimeofsystempeakdemand.California’ssystemRArequirementsarebasedon1-in-2yearpeakdemands,whilelocalRArequirementsarebase