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大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究IntegrationofGeomagneticDisturbance(GMD)Modeling

intothePowerFlowThomasJ.OverbyeFoxFamilyProfessorof

ElectricalandComputerEngineeringUniversityofIllinoisatUrbana-Champaign

March13,2012大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究2OverviewGeomagneticdisturbances(GMDs)havethepotentialtoseverelydisruptoperationsofthe

electricgrid,yetpowerengineers

currentlyhavefewtoolstohelp

themassesstheimpactofGMDs

ontheirsystemsGoalofthethisworkistoperform

theresearchnecessarytohelpmove

GMDassessmentintotherealmofpowersystemplanningandoperationsengineersGuidingmotto:“Allmodelsarewrongbutsomeareuseful,”GeorgeBox,1979GICimpactiscertainlystillanareaofresearch,butpowerengineersneedtoolstoconsideritsimpactontheirsystems大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究3

NERCInterimGMDReport

OnFebruary29,2012NERCissuedanInterimGMDReportavailableatInsectionI.10oftheExecutiveSummarytherearefourhighlevelrecommendedactionsImprovedtoolsforindustryplannerstodevelopGMDmitigationstrategiesImprovedtoolsforsystemoperatorstomanageGMDimpactsDevelopeducationandinformationexchangesbetweenresearchersandindustryReviewtheneedforenhancedNERCReliabilityStandardsIhopethisprojecthelpswithatleastthefirst3ofthese大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究4MyBackgroundinGMDMyinterestcomesfromPSERC’sDOEfunded“TheFutureGridtoEnableSustainableEnergySystems”projectInJune2011IattendedtheJASONGMDbriefingRealizedGMDcalculationscouldaddedtothepowerflowImplementedthesecalculationsinPowerWorldSimulatorwhileworkingtherefull-timeinsummer2011PresentedresultsinNovember2011atNERC’sGeo-MagneticDisturbanceTaskForce;basedonfeedbackchangedGMDmodelingapproachIn2012startedEPRIlarge-scalesystemstudyandalsoworkingwithseveralotherutilitiesforstudies大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究5GeomagneticDisturbances(GMDs)Solareventscancausechangesintheearth’smagneticfield(i.e.,dB/dt).ThesechangesinturnproducesanelectricfieldatthesurfaceChangesinthemagneticfluxareusuallyexpressedinnT/minute;froma60Hzperspectivetheyproduceanalmostdcelectricfield1989NorthAmericastormproduceda

changeof500nT/minute,whilea

strongerstorm,suchastheonein

1921,couldproducemorethan

5000nT/minutevariationStorm“footprint”canbecontinentalinscale,forexamplecoveringmuchoftheU.S.Forreference,Earth’smagneticfieldisnormallybetween

25,000and65,000nT,withhighervaluesnearthepolesImagesource:J.Kappenman,“APerfectStormofPlanetaryProportions,”IEEESpectrum,Feb2012,page29大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究6March8-9,2012“Event”Forecastedsolarstormlastweekwasnotnearlyaslargeassomethought(graphisdB/dtatOttawa,45.4N)Imagesource:Lessthan

100nT/

minute,

compared

to500nT/

minutefor

the1989

eventand

5000in

1921

大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究7ElectricFieldsandGeomagneticallyInducedCurrents(GICs)AsdescribedbyFaraday’slaw,changesinthemagneticfluxintensityproducea(non-uniform)electricfieldonthesurface;valuesareimpactedbygroundconductivityElectricfieldsarevectorswithamagnitudeanddirection;valuesareusuallyexpressedinunitsofvolts/mile(orvolts/km);A2400nT/minutestormcouldproduce5to10volts/mile.Theelectricfieldscausegeomagneticallyinducedcurrents(GICs)toflowinelectricalconductorssuchhasthehighvoltagetransmissiongridFromamodelingperspectivetheinducedvoltagesthatdrivetheGICscanbemodeledasdcvoltagesinthetransmissionlines.Themagnitudeofthedcvoltageisdeterminedbyintegratingtheelectricfieldvariationoverthelinelength大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究8GeomagneticallyInducedCurrents(GICs)大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究9PowerSystemImpactsofGICsThedcGICsaresuperimposedupontheaccurrents.Intransformersthiscan

pushthefluxinto

saturationforpartof

theaccycleThiscancauselarge

harmonics;inthe

positivesequence

(e.g.,powerflowand

transientstability)these

harmonicscanberepresentedbyincreasedreactivepowerlossesonthetransformer.

大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究10MappingTransformerGICstoTransformerReactivePowerLossesTransformerspecific,andcanvarywidelydependinguponthecoretypeSinglephase,shell,3-legged,5-leggedIdeallythisinformationwouldneedtobesuppliedbythetransformerownerCurrentlysupportdefaultvaluesorauserspecifiedlinearmappingForlargesystemstudiesdefaultdataisusedwhennothingelseisavailable.ScalingvaluechangeswithcoretypeStilldebateintheindustrywithrespecttothemagnitudeofdamageGICswouldcauseintransformers(fromslightlyagetopermanentlydestroy)大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究11TheImpactofaLargeGMD

FromanOperationsPerspectiveTherewouldbeadayorsowarningbutwithoutspecificsontheactualmagnitudeItcouldstrikequickly(theymoveatmillionsofmilesperhour)withrisestimesoflessthanaminute,rapidlycoveringagoodchunkofthecontinentReactivepowerloadingsonhundredsof

transformerscouldskyrocket,causing

heatingissuesandpotentiallarge-scalevoltagecollapsesPowersystemsoftwarelikestateestimationcouldfailControlroompersonnelwouldbeoverwhelmedThestormcouldlastfordayswithvaryingintensityWaitinguntilitoccurstopreparemightnotbeagoodidea Imagesource:J.Kappenman,“APerfectStormofPlanetaryProportions,”IEEESpectrum,Feb2012,page29大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究12GMDEnhancedPowerAnalysisSoftwareByintegratingGICcalculationsdirectlywithinpoweranalysissoftware(likepowerflow)powerengineerscanreadilyseetheimpactofGICsontheirsystems,andconsidermitigationoptionsGICcalculationsusemanyoftheexistingmodelparameterssuchaslineresistance.Butsomenon-standardvaluesarealsoneeded;powerengineerswouldbeinthebestpositiontoprovidethesevalues,butallcanbeestimatedwhenactualvaluesarenotavailableSubstationgroundingresistance,transformergroundingconfiguration,transformercoilresistance,whetherauto-transformer,whetherthree-windingtransformer,generatorstep-uptransformerparameters大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究13GICG-MatrixWithknowledgeofthepertinenttransmissionsystemparametersandtheGMD-inducedlinevoltages,thedcbusvoltagesandGICflowscanbecalculatedbysolvingalinearequation

I=G

V

TheGmatrixissimilartotheYbusexcept1)itisaugmentedtoincludesubstationneutrals,and2)itisjustconductancesThecurrentvectorcontainstheNortoninjectionsassociatedwiththeGMD-inducedlinevoltagesFactoringthesparseGmatrixanddoingtheforward/backwardsubstitutiontakesabout1secondforthe62,600busEasternInterconnectModel大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究14FourBusExampleThelineandtransformerresistanceandcurrentvaluesare

perphasesothetotal.Substationgroundingvaluesaretotal

resistance.BrownarrowsshowGICflow.大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究15DeterminingGMDStormScenariosThestartingpointfortheGICanalysisinthepowerflowisanassumedstormscenario;thisisusedtodeterminethetransmissionlinedcvoltagesMatchinganactualstormcanbecomplicated,andrequiresdetailedknowledgeoftheassociatedgeologyFeb2012NERCreportrecommendedforplanningpurposesasimilarapproachcouldbeusedUniformelectricfield:Alllocationsexperiencethesameelectricfield;inducedvoltagesinlinesdependonassumeddirectionMaximumvaluein1989was1.7V/km(2.7V/mile)Wealsoconsideramoredetailednon-uniformmodelNon-uniformelectricfield:Magnitudeofelectricfieldvariesaccordingasomefunction;inducedvoltagesinlinesdependonmagnitudeandassumeddirection大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究16East-West(90Degrees)Non-uniformGMDScenario,Centeredat42N,88.5W;5volt/mile大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究17NE-SW(45Degrees)Non-uniformGMDScenario,Centeredat42N,88.5W;5volt/mile大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究18IntegratedGeographicInformationThepotentiallytime-varyingGMDinduceddcvoltagesaredeterminedbyknowingthelatitudeandlongitudeofthetransmissionlinesJustknowingthegeo-coordinatesoftheterminalbusesshouldbesufficientHencebusesneedtobemappedtosubstations,andsubstationstotheirgeo-coordinatesForthisprojectsubstation/geographicdatawassuppliedbyPowerWorldBusesmappedtosubstations;notebusnumbersdovaryevenwithincasesinaparticular“series”likethe2010MMWGcasesLatitudeandlongitudeprovidedforsubstationsDatacaneasilybeimported/exported大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究19ImpactofElectricFieldAngleonGICsAsmentionedearlier,the

resultantGICsdependupontheelectricfieldangle;differentangleshavedifferentsystemimpactsTheresultsshowntotherightgivethetransformerMvarGIC-inducedlossesbyareaintheEasternInterconnect(usingpseudo-IDsforconfidentiality)assumingauniform2V/milefield.大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究20GettingAccesstotheResultsGICstudiesinvolvethetraditionalpowersystemresults(voltages,flows,etc.),alongwithanewsetofvariablessuchasEstimatedparameters,suchassubstationgroundingandtransformercoilresistanceSubstationneutraldcvoltagesBusdcvoltagesGICflowsinbranchesGICinducedreactivepowerlossesintransformersProvidinguserswitheasyaccesstotheresults/dataiskey,asisgoodwide-areavisualization大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究21PerUnitVoltageDropsCausedbyEast-West5V/mileGMDStormScenarioTheseresultsarejustillustrative.Actual

modelparameterswill

helpgivebetterresults.大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究22GIC-enhanced

PowerFlowListDisplay大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究23PowerFlowConvergenceIssuesIntegratedGICmodelingcancertainlyimpactpowerflow

convergencesincetheGICinducedreactivepowerlossessimultaneouslyaddlotsofreactivepower.SeveraltechniquescanhelppreventdivergenceJustcalculatingtheGICswithoutsolvingthepowerflowNotcalculatingGMDinducedvoltagesforequivalentlinesGraduallyincreasingtheassumedelectricfieldstoavoidsimultaneouslyaddingtoomuchreactivepoweratonetimeOnlycalculatingtheGICtransformerreactivepowerlossesforspecifiedareas;reactivepowerdoesn’ttendtotravelfarFreezingthetransformertapsandswitchedshuntsincertainproblematicareasSolvingintransientstabilityforagraduallyincreasingGMD大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究24IntegratingGICCalculationsinto

PowerSystemPlanningAlargeGMDcouldcausesubstantiallydifferentpowersystemflowsandvoltagesStudiesallowfortestingvariousmitigationstrategiesOperational(short-term)changesincluderedispatchinggenerationtoavoidlongdistancepowertransfersandreducingtransformerloadingvalues,andstrategicallyopeningdevicestolimitGICflowsLonger-termmitigationactionsincludetheinstallationofGICblockingdevicesonthetransformerneutrals(suchascapacitors)and/orincreasedseriescapacitorcompensationonlongtransmissionlinesDeterminingrelaysettings–whentotripthetransformer大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究25ResearchExample:ShouldtheLowerVoltageNetworkbeIncludedNERCreportstatedwithrespecttoGICcalculations,“Transmissionlinesbelow230kVaretypicallynotmodeled…”O(jiān)urresearchindicatesignoringtheselowvoltagelinesmightsubstantiallyunderreportthetotalGICflowsandtheassociatedincreaseinreactivepowerloadingForEasternInterconnectcasewithauniform2.0volt/mileeast-westfieldthetotalGICrelatedreactivepowerlossesare64,525Mvarconsideringalllines,44,341Mvariflinesbelow150kVareneglectedandjust40,984iflinesbelow200kVareneglected.NoreasonnottoincludetheselinessincetheyareinthestandardpowerflowmodelsComputationallyneglectinglinesisfaster,butthecalculationsarequitecomputationallyefficient大規(guī)模電力系統(tǒng)地磁干擾引起的GIC可視化分析與計算研究26ResearchExample:DeterminingMitigati

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