An Impedance-based Protection Principle for Active Distribution Network

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2018ChinaInternationalConferenceonElectricityDistributionTianjin,17-19Sep.2018AnImpedance-basedProtectionPrincipleforActiveDistributionNetworkGuobinChen,YiqingLiu*,QifanYangSchoolofElectricalEngineering,UniversityofJinan(*Correspondingauthor)(1)ThetraditionalprotectionprinciplebasedonlocalAbstract—Inordertoaddresstheproblemsencounteredbytheinformationhasbeenimproved.Theadaptiveprotectionprotectioninactivedistributionnetwork,particularlytheabsenceprincipleisusedtoimproveprotectionperformancebyoftheselectivityandreliability,animpedance-basedprotectionchangingprotectionthresholdaccordingtoDGfaultoutputprincipleisproposed.Afterdefiningthedifferentialimpedancecharacteristic[4]-[7].Althoughthiskindofmethodeffectivelyandrestraintimpedance,thispaperestablishesanovelprotectionsolvesthesensitivityproblemoftheexistingprotection,therecriterionaccordingtothesignificantdifferencesbetweenthedifferentialimpedanceandrestraintimpedancewhennormalarestillproblemsofprotectiondelayanddifficultcoordinationoperation,externalfaultorinternalfault.Furthermore,theafterthehighpermeabilityDGaccess.auxiliarycriterionisconstructedonlybytheamplitude(2)Thepilotprotectionbasedondouble-endedinformationcharacteristicoffaultcurrenttoovercometheexistingdead-zonehasbeenintroducedintoactivedistributionnetwork[8]-[10].ofimpedancedifferentialprotection.TheproposedprotectionAlthoughthisprincipleofprotectionhasgoodselectivityontheprincipleisverifiedbydigitalsimulation.Comparedwithcurrenttwo-terminalpowerline,itisdifficulttoapplydirectlybecausedifferentialprinciple,theimpedance-basedprinciplecaneffectivelycompromisethelevelofdatasynchronizationandthethecurrentautomationlevelofdistributionnetworkcannotband-widthofdatatransmission.Thesecharacteristicsplayanmeettherequirementsofsamplingvaluesynchronization.Thenimportantroleinadaptingtothecommunicationinfrastructureofprotectscholarsputforwardaseriesofpilotprotectiondistributionnetwork.principlebasedonthedouble-endedinformation,whichhavelowsynchronizationrequirements,suchaspositivesequenceIndexTerms—Activedistributionnetwork;Impedance-basedimpedancedifferentialprotection[11],faultcomponentphaseprotection;Differentialimpedance;Restraintimpedance;Datacomparison[12]-[14],currentamplitudecomparison[15],andsynchronizationenergyfunctionpilotprotection[16]-[17].However,theseI.INTRODUCTIONmethodsdonotconsiderthecomplexfaultcharacteristicsofDG,andtheirreliabilityneedsfurtherstudy.ITHtheincreasingenergycrisisandenvironmentalW(3)Inordertoadapttothedecentralizedaccessofalargepollution,distributedgenerator(DG)basedongreennumberofDG,aclassofcommunication-basedprotection,energyhasattractedextensiveattention.However,withalargeusingnetworkedthinkingofmulti-pointinformationinthenumberofDGaccess,thetraditionaldistributionnetworkhasdistributionnetwork,hasbeenproposedtorealizerapidfaultbecomeamulti-sourcenetworkwithbidirectionalflowofidentificationandlocation[18]-[20].However,suchprotectionpower.Asaresult,thecurrentprotectionperformanceofthehashighrequirementsforthecoverageofcommunicationsdistributionnetworkfacesseverechallenges,andevenappearssystemsandalargeamountofengineeringmodifications,anditthephenomenonofunwantedoperationorrefusingoperationisdifficulttoachieveapracticallevelintheshortterm.[1]-[3].ConsideringtheaboveproblemsoftheexistingprotectionInordertosolvetheprotectionproblemofdistributionandthecomplexfaultcharacteristicsofDG,thispapernetworkwithDG,scholarshaveconductedextensiveproposestheimpedancedifferentialprinciple.Basedtheresearches.Theachievementscanbedividedintothefollowingdifferentcharacteristicsoftheinternalandexternalfaults,thisthreecategories:paperestablishestheimpedancedifferentialcriterion.ThentheauxiliarycriterionisconstructedtosolvetheproblemofManuscriptreceivedJuly10,2018.Thisworkwassupportedinpartbytheprotectiondeadzone.Eventually,sufficientsimulationsbasedShandongProvincialNaturalScienceFoundation,China,underGrantZR2018MEE039.onPSCADverifytheeffectivenessoftheproposedprotectionG.CheniswiththeSchoolofElectricalEngineering,UniversityofJinan,principle.Jinan250022,China(e-mail:18366101539@163.com).Y.LiuiswiththeSchoolofElectricalEngineering,UniversityofJinan,Jinan250022,China(e-mail:cse_liuyq@ujn.edu.cn).Q.YangiswiththeSchoolofElectricalEngineering,UniversityofJinan,Jinan250022,China(e-mail:yang7f@163.com).CICED2018PaperNo.201804030000002Page1/51241

12018ChinaInternationalConferenceonElectricityDistributionTianjin,17-19Sep.2018II.IMPEDANCEDIFFERENTIALPRINCIPLEWhereUMandUNarethebusvoltagesmeasuredatMandA.DifferentialimpedanceandrestraintimpedanceN;IMandINrepresentthecurrentsmeasuredatprotectionMTheprotectedlineMNistakenasanexampletoillustratetheandN,respectively.impedancedifferentialprotectionprinciple.Fig.1showsHence,thedifferentialimpedanceandrestraintimpedanceequivalentcircuitofdistributionnetworkwithDGwhenarecalculatedasfollowswhennormaloperation:normaloperation,externalandinternalfault.ZdifZMZNZL2ZloadEMMNP(2)ZLZresZMZNZLLoadIMIBecauseZloadZmin,Zmaxwhennormaloperation,theNEDGrangeofdifferentialimpedanceispresentedasfollows:(a)ZL2ZminZdifZL2Zmax(3)EMNPMZZLK2)ExternalfaultLoadWhenanexternalfaultoccursatk2inFig.1(b),theIMINk2Emeasuredimpedancescanbeexpressedasfollows:DG(b)UMEZMZLZKMMNPIZ(1)ZMLL(4)ULoadZNZIkNKM1ININEDGThen(5)givesthedifferentialimpedanceandrestraint(c)Fig.1Principlediagramofimpedancedifferentialprotection.(a)Normalimpedance:operation(b)Externalfault(c)InternalfaultZdifZMZNZL2ZK(5)InFig.1,EandEaregridsideandDGsideequivalentZresZMZNZLMNpotential;ZListheimpedanceoflineMN;istheratiooftheWhereZK0,,andtherangeofdifferentialimpedancedistancefromfaultpointk1toMsidetothetotallengthoftheis:line,where0，1.ZloadistheequivalentloadimpedanceZLZdifZL(6)connectedtobusN.Assumingthattheloadpowerisdelivered3)InternalfaultfromtheMsidetotheNsideinnormaloperation,thentheForthefaultpointk1inFig.1(c)occurringintheprotectednormalloadrangeisZloadZmin,Zmax,whereZmin,ZmaxarefeederMN,themeasuredimpedancescanbeexpressedastheminimum,maximumequivalentloadimpedance.ZKisthefollows:equivalentimpedancebetweenbusNandexternalfaultpointUMZMZLk2,andZK0,.IM(7)Basedoncurrentdifferentialprinciple,differentialUNimpedanceisdefinedasZZZ,andtherestraintZN1ZLdifMNINimpedanceisdefinedasZresZMZN,whereZMandZNThenthedifferentialimpedanceandrestraintimpedancearearethemeasurementimpedanceofMandNside.calculatedasfollows:B.PrincipleanalysisZdifZMZN21ZL(8)ThecharacteristicsanalysesofdifferentialimpedanceandZresZMZNZLrestraintimpedanceinFig.1areasfollows:Where0,1,andtherangeofdifferentialimpedanceis:1)NormaloperationZLZdifZL(9)ThemeasuredimpedancesZMandZNwhennormalTableIliststherelationshipofdifferentialimpedanceandoperationareexpressedasfollows:restraintimpedanceunderthreeoperatingconditionswiththeUMZMZLZloadabovediscussion.Therefore,thefaultlocationcanbeIM(1)determinedbytheamplituderelationshipbetweenZdifandUNZNZloadZres.INEspecially,ZdifandZrescanbecalculatedbyZMandZN,CICED2018PaperNo.201804030000002Page2/51242

22018ChinaInternationalConferenceonElectricityDistributionTianjin,17-19Sep.2018whichonlyneedthesynchronoussamplingoflocalvoltageandthepowergridandDGsiderespectively.ThemagnitudeofIMcurrent,withoutstrictdatasynchronizationatbothends.Inaddition,theimpedancedifferentialprotectiononlyneedtoandINisobviouslydifferent,generally|IM||IN|.Hence,exchangethecalculatedimpedancevaluethroughthedatatherightsideof(10)issmallerthantheleftsideof(10)duetochannel,sotheamountofdatatransmissionissmall.therestraintcoefficient.Therefore(10)isnotsatisfiedandtheTABLEIprotectioncanactreliably.COMPARISONOFDIFFERENTIALANDRESTRAINTIMPEDANCESUNDERInconclusion,when0.95|Zres||Zdif|1.05|Zres|,theDIFFERENTCONDITIONSRestraintauxiliarycriteriacanbeusedtodeterminethefaultlocationandDifferentialimpedanceimpedanceComparingeliminatethedeadzone.Moreover,theauxiliarycriteriaonly/Zdif/resultsusedouble-endedcurrentamplitudeinformation,withoutZresNormalZ2ZZZ2Zstrictlysynchronoussamplingofdouble-endedcurrent.LmindifLmaxZLZdifZresoperationExternalZZZIII.SIMULATIONANDANALYSISLdifLZLZdifZresfaultToverifytheeffectivenessofimpedancedifferentialInternalZZZprotectionprincipleandvariousinfluencingfactors,asshownfaultLdifLZLZdifZresinFig.2,atypical110kVdouble-endedpowersupplymodelisestablishedinPSCAD,wheretheMsideandtheNsidearetheC.AuxiliaryCriteriaforProtectionDeadZonegridsideandtheDGside,respectively.PhotovoltaicmodelPVFromtheforegoinganalysis,thefaultlocationcanbeisaccessedfrombusQ.distinguishedbythemagnituderelationshipbetweenZdifandPMNQZ.However,whenafaultoccursattheendoftheprotectedEMENresfeederlineorthebeginningofthenextfeeder,ZdifZresZL.Hence,thereisadeadzoneforimpedancedifferentialprinciple.f5f1f2f3f4Therefore,anauxiliarycriterionneedstobeconstructedtoeliminatetheprotectiondeadzone.PVThemaincriteriaandauxiliarycriteriaofimpedanceFig.2SimulationmodelofdistributionnetworkwithDGdifferentialprotectionareexpressedasfollows:1)When|Zdif|0.95|Zres|,thejudgmentisinternalfault.ThelengthoftheprotectedlineMNis100km,where2)When|Z|1.05|Z|,thejudgmentisexternalfault.r10.1184/km,l11.214mH/km,c10.0096F/km,difres3)When0.95|Z||Z|1.05|Z|,thefaultislocatedatr00.3580/km,l03.8109mH/km,c00.0054F/km.f1~resdifresf3areinternalfaultpoints,whicharerespectivelylocatedatdeadzone,andtheauxiliarycriterionstarttowork.Consideringtheimpedancedifferentialprotectionhasthe30%,50%and70%fromtheMsideoftheline.f4andf5areadvantageoflessdatasynchronizationrequirements,theexternalfaultpointslocatedat20kmfrombusMandN.Theauxiliarycriteriamustalsonotrequirestrictdatafailuretimeis0.800sandthedurationtimeoffailureis0.200s.synchronization.Therefore,theauxiliarycriterionemploysTableIIliststhediscriminantresultsofimpedanceonlycurrentamplitude,asshownin(10).IfIMandINdifferentialprotectionundervariousfaulttypesofinternalandexternalfaults.satisfiescriterion(10),thejudgmentisinternalfault;otherwise,Whentheinternalfaultpointislocatedatthemidpointoftheisexternalfault.protectedlineMN,thedifferentialimpedanceisclosetozero|IM||IN|k(|IM||IN|)Iset(10)andtheimpedancedifferentialprotectionhasthehighestsensitivity.TheclosertheinternalfaultpointistobusMandN,Wherekistherestraintcoefficientandk0.1~0.2;Isetisthelargerthedifferentialimpedanceis,andthelowerthethecurrentfixedthresholdandIset0.05IN(INistheratedprotectionsensitivityis.secondarycurrent).Forexternalfaults,thefartherthefaultlocationisfromtheWhenanexternalfaultoccurs,IMandINareprovidedbyprotectedline,thelargerthedifferentialimpedanceis,andthethesameside,so|IM||IN|.Theleftsideof(10)isclosetohighertheprotectionreliabilityis.Whetheritisinternalorexternalfault,therestraintimpedancealwaysreflectsthezero;therightsideof(10)isthetwotimesoffaultcurrent,protectedlineimpedance.whichismuchgreaterthanzero.Hence,(10)isnotsatisfiedandFig.3showsthewaveformsofdifferentialimpedanceandtheprotectiondoesnotactreliably.restraintimpedancewhenthefaultoccursatf2andf5.WeWhenaninternalfaultoccurs,IMandINaresuppliedbycanseethatZdifandZreswhennormaloperationareCICED2018PaperNo.201804030000002Page3/51243

32018ChinaInternationalConferenceonElectricityDistributionTianjin,17-19Sep.2018significantlyhigherthanwhenafaultoccurs.Fromthedistributionnetwork.comparisonbetweenFig.3(a)and(b),ZdifZreswhenafaultoccursatf2andZdifZreswhenanexternalfaultoccursatf5.Thesimulationresultsareconsistentwiththetheoreticalanalysisresults.Inordertoverifythevalidityofthecurrentamplitudecriterion,thefaultpointsofdifferentfaulttypesaresetupininteriorofMsidebusandoutsideoftheNsidebus,andallfaultpointsarelocatedindeadzoneofprotection.Inaddition,therestraintcoefficientisk0.1.TheactionsituationofimpedancedifferentialcriteriaandcurrentamplitudecriteriaareshowninTableIII.(a)ThesimulationresultsinTableIIIshowthatimpedancedifferentialcannotbeabletoworkproperlywhenafaultoccursinthedeadzone.Atthemoment,theauxiliarycriteriacanensurethecorrectactionoftheprotection.IV.CONCLUSIONThispaperproposedanimpedance-basedprotectionprincipleforactivedistributionnetwork.Thefaultlocationisdeterminedbytheamplitudedifferencebetweendifferentialimpedanceandrestraintimpedance.Atthesametime,thecurrentamplitudedifferenceofbothsidesisusedtoconstructanauxiliarycriteriontoeliminateprotectiondeadzone.Furthermore,digitalsimulationverifytheeffectivenessofthe(b)proposedprotectionprinciple.Fig.3Waveformsofdifferentialimpedanceandrestraintimpedance.(a)afaultImpedancedifferentialprotectionnotonlyhasabsoluteoccursatf2(b)afaultoccursatf5selectivity,butalsoreducesthelevelofdatasynchronizationandtheband-widthofdatatransmission.Moreover,theproposedcriterionisonlyrelatedtothefeederimpedance,hencetheproposedprotectioniseasytoimplementintheactiveTABLEIIIDENTIFICATIONRESULTSOFIMPEDANCEDIFFERENTIALPROTECTIONFaultLocationFaultTypeZMZNZdifZresIdentificationResultAG11.96∠72.6627.80∠72.6915.8139.79InternalfBC11.99∠72.6628.02∠72.6516.0340.02Internal1CAG11.99∠72.6627.83∠72.4115.8439.82InternalBG19.99∠72.6619.89∠72.670.1039.88InternalInternalfCA20.00∠72.6420.00∠72.640.0040.00InternalFault2ABG19.99∠72.6319.90∠72.500.1039.89InternalCG28.00∠72.6611.95∠72.6816.0539.96InternalfAB28.02∠72.6411.99∠72.6716.0340.02Internal3BCG28.01∠72.6211.99∠72.5616.0539.97InternalAG48.13∠72.607.99∠252.6556.1240.14Externalf4BCG48.22∠72.568.00∠252.6256.2140.22ExternalExternalFaultCA7.99∠-107.3848.21∠72.5756.2040.22Externalf5ABCG7.99∠-107.3348.21∠72.6256.2040.21ExternalCICED2018PaperNo.201804030000002Page4/51244

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