外文翻译-多路受限输入的变压器差分继电器自动测试

英文原文AutomaticTestingofAdvancedTransformerDifferentialRelayswithMultipleRestrainedInputsAbstract:Testingofadvancedmicroprocessorbasedtransformerdifferentialrelayswithmultiplerestrainedinputspresentsasignificantchallengetotheprotectionengineer.Theavailabilityofmultipleprotectionfunctionsprotectingthetransformerfordifferentinternal,externalandsystemfaultoroverloadconditionsmaketestingofmultifunctionaltransformerprotectionrelaysverycomplicatedandtimeconsumingtask,whichrequiresspecializedequipment.Thepaperdiscussestherequirementsforadequatetestingofeachofthespecificprotectionfunctions.Areportorientedapproachtotheautomatictestingofthemultifunction-almulti-restrainedtransformerdifferentialrelayisdescribedaswell.Therelaysaretestedforbothinternalorexternalfaults.Phase-to-phaseandphase-to-groundfaultsareconsidered.Hardwarerequirementsandconfigurationforautomatictestingareintroduced.Definitionofatransformerprotectionrelayasatestobjectispresented.Differenttestmethodsarediscussedinthelastsectionofthepaper.Keywords:TransformerProtection.MultifunctionalMicroprocessorRelays.AutomaticTestingI.INTRODUCTIONTransformersarethemostexpensivepieceofequipmentinatypicaltransmissionordistributionsubstationandareexposedtoawidevarietyofconditionsthatcancausedifferentlevelsofdamage.Transformerfaultsaregenerallyclassifiedintofourcategories:WindingandterminalfaultsCorefaultsAbnormaloperatingconditionssuchasovervoltage,overfluxingandoverloadSustainedorunclearedexternalfaultsAlloftheaboveconditionsmustbeconsideredindividuallyandthetransformerprotectionpackagedesignedaccordingly.Toprovideeffectiveprotectionforfaultswithinatransformerandsecurityfornormaloperationandexternalfaults,thedesignandapplicationoftransformerprotectionmustconsiderfactorssuchas:MagnetizinginrushcurrentWindingarrangementsWindingconnectionsConnectionofprotectionsecondarycircuitsThemultifunctionalmicroprocessorbasedrelaysmustprovideadequateprotectionforanypotentiallydamagingfaultorsystemcondition,optimalperformanceandsecureandreliableoperation.Thismeansthattherelayshouldtripasfastaspossibleforanytransformerinternalfaultandatthesametimeshouldnotoperateforanyexternalfaultcondition.Misoperationshouldalsobeavoidedforanyothernon-faultcondition,whilestillprovidingprotectionforconditionsthatareharmfulifthedurationoftransformerexposureissignificant.Powertransformersdesign,sizeandconfigurationvarysignificantly.This,combinedwiththenumeroussubstationschemesusedresultsinalargenumberofpossibletransformerprotectionapplications.Tosatisfyalltheaboverequirements,todaysadvancedstate-of-the-arttransformerprotectionrelayscombinemultipleprotectionfunctionsandalgorithmswithmultiplerestrainedinputs.Adequatetestingofsuchmultifunctionalmicroprocessorrelaysandthesimulationofthesubstationenvironmentfordifferentfaultandnon-faultconditionsisaverytimeconsumingtaskthatrequiressophisticatedtestequipment.TRANSFORMERPROTECTIONRELAYFUNCTIONSThemainprotectionfunctioninatransformerprotectionrelayisthedifferentialprotection.Undernormaloperationsteadystatemagnetizingcurrentandtheuseofloadtapchangersresultinunbalancedconditions.Toaccommodatetheseconditionsthedifferentialelementhasamulti-slopecharacteristic.Theinitialslopeensuressensitivityforinternalfaultswhileallowingforupto15%mismatchwhenthepowertransformerisatthelimitofitstaprange.Atcurrentsaboverated,extraerrorsmaybegraduallyintroducedasaresultofCTsaturation.Adifferentrestrainedslopecharacteristicistypicallyusedtocompensateforthis.However,misoperationofthedifferentialelementispossibleduringtransformerenergization.Highinrushcurrentsmayoccur,dependingonthepointonwaveofswitchingaswellasthemagneticstateofthetransformercore.Sincetheinrushcurrentflowsonlyintheenergizedwinding,differentialcurrentresults.Theuseoftraditionalsecondharmonicrestrainttoblocktherelayduringinrushconditionsmayresultinasignificantslowingoftherelayduringheavyinternalfaultsduetothepresenceofsecondharmonicsasaresultofsaturationofthelinecurrenttransformers.Toovercomethis,someadvancedrelaysuseawaveformrecognitiontechniquetodetecttheinrushcondition.Thedifferentialcurrentwaveformassociatedwithmagnetizinginrushischaracterizedbyaperiodofeachcyclewhereitsmagnitudeisverysmall,asshowninFigure1.Bymeasuringthetimeofthisperiodoflowcurrent,aninrushconditioncanbeidentified.Thedetectionofinrushcurrentinthedifferentialcurrentisusedtoinhibitthatphaseofthelowsetalgorithm.Fig.1TransformerinrushcurrentwaveformsWhenaloadissuddenlydisconnectedfromapowertransformerthevoltageattheinputterminalsofthetransformermayriseby10-20%ofratedvaluecausinganappreciableincreaseintransformersteadystateexcitationcurrent.Theresultingexcitationcurrentflowsinonewindingonlyandhenceappearsasdifferentialcurrentwhichmayrisetoavaluehighenoughtooperatethedifferentialprotection.AtypicalcurrentwaveformisshowninFigure2.Awaveformofthistypeischaracterizedbythepresenceoffifthharmonic.AFouriertechniqueisusedtomeasuretheleveloffifthharmonicinthedifferentialcurrent.Theratiooffifthharmonictofundamentalisusedtodetectexcitationandinhibitstherestraineddifferentialprotectionfunction.Detectionofoverfluxconditionsinanyphaseblocksthatparticularphaseofthelowsetdifferentialfunction.Fig.2MultifunctionaltransformerprotectiontestobjectTransformerfaultswithveryhighfaultcurrentsrequirefastfaultclearingtoreducetheeffectofcurrenttransformersaturationandthedamagetotheprotectedtransformer.Anunrestrainedinstantaneoushighsetdifferentialelementensuresrapidclearanceofterminalfaults.ThiselementisessentiallypeakmeasuringtoensurefastoperationforinternalfaultswithsaturatedCTs.Thehighsetdifferentialfunctionisnotblockedundermagnetizinginrushoroverexcitationconditions,hencethesettingmustbesetsuchthatitwillnotoperateforthelargestinrushcurrentsexpected.Attheotherendofthefaultspectrumarelowcurrentwindingfaults.Restrictedgroundfaultprotectiongivesgreatersensitivityforgroundfaultsandhenceprotectsmoreofthewinding.Aseparateelementisprovidedforeachwinding.Anexternalresistorisrequiredtoprovidestabilityinthepresenceofsaturatedlinecurrenttransformers.Therestrictedgroundfaultprotectionworksonthehighimpedancecirculatingcurrentprinciple.Whensubjectedtoheavythroughfaultsthelinecurrenttransformermayentersaturationunevenly,resultinginunbalance.CONVENTIONALTESTINGOFTRANSFORMERPROTECTIONItisobviousfromtheprevioussectionofthepaperthattestingofamultifunctionaltransformerprotectivedeviceusingconventionalmethodsisnotaneasytask.Typicallyatransformerdifferentialrelayistestedbyinjectingasinglephasecurrentinthehighsideandlowsideinputsofthedifferentialrelay,orbyinjectingthreephasecurrentonlytothehighside.Thiswillonlyprovethatthedifferentialelementwillpickup,butinnowayitwillrepresentafaultorloadconditioninareallifeapplication.Thecommoncaseofadelta/wyeconnectedtransformer,anautotransformerorathreewindingtransformerwithadeltawinding(Fig.2)cannotbeadequatelytestedusingsuchapproach.Itispossibletochecktheeffectofthezerosequencetrapinthetransformerdifferentialprotectionbyinjectingasinglephasecurrentsimulatinganexternalfaultandcheckingtheratioofthemeasuredbytherelayrestrainedcurrentinthethreephases.Again,thistestisnotrepresentativeofactualfaultconditionsinthesystemforsuchafault.AdequatetestingofatransformerdifferentialrelayusingconventionalmethodsrequiresperformingfirstfaultcurrentscalculationusingafaultanalysisprogramsuchasASPENOnelinerorCAPEandthenmanuallysettingallcurrentswiththeirmagnitudeandphaseangletoperformasingletest.AnalternativeistouseaCOMTRADEfilegeneratedbyanelectromagnetictransientprogram,However,thesearenoteasilyavailableandifitisrequiredtocheckthedifferentialrelaymulti-sloperestrainedcharacteristic,itbecomesaverytimeconsumingtask.IftherelayhasalsoaRestrictedGroundFaultprotectionfunction,thiswillrequirethecalculationandmanualentryofthecurrentintheneutralofthetransformeraswell.Ifoverexitationfunctionisalsotobetested,avoltagesourceisrequiredaswell.Tosuccessfullycompletethetestingofamultifunctionaltransformerprotectionrelayalsoneedsalotofpaperworktowardsthetestsetupandtheresultsfromeachindividualtestperformed.Itisobviousfromtheabove,thatanewapproachthatwillimprovetheefficiencyoftransformerprotectiontestingintodaysworldofcompetitionanddownsizingisrequiredIV.AUTOMATICTESTINGOFADVANCEDTRANSFORMERPROTECTIONThepurposeofeverylestistoverifythenominalsettingsofaprotectionsystembymeasuringitsperformanceunderdifferentfaultandabnormalconditions.Thetestsetupandallresultshavetobedocumentedinsuchaway,thatlaterthisinformationmayberetrievedeasilyandcompletely.Anobjectorientedapproachtothetestingallowstheprotectionengineertocompletelytestinaveryshorttimeacomplexmultifunctionaltransformerprotectiondevice.Differentrelayvendorscombineprotectionandcontrolfunctionsinvariousways.Thisrequiresflexibilityintheconfigurationoftheautomatictestingprocess.Onlyfeaturesthatareavailableinthetestobject,inthiscaseatransformerprotectiondevice,shouldbetested.Otherwise,theresultsarenotgoingtorepresentcorrectlythebehaviouroftherelayfortestconditionsthatcorrespondtoprotectionorcontrolfunctionsthatitdoesnothave.Anotherimportantfactorinsettingupanautomatictransformerprotectiontestprocedureistheavailabilityofdevicespecifictestmodules.Thevarietyofprotectionandcontrolfunctionsandthemethodsfortheirimplementationmakesitdifficulttobuildacompletelibraryofprotectionmodulesthatwillcoverallpossibletransformerprotectionfunctions.Thisrequirestheavailabilityofasetoftoolsthatwillallowtheprotectionengineertodevelopanyneededtestmodule.Theautomatictestingofthetransformerprotectiondevices：involvesseveralstepsconfigurationtestreportingAllthesetasksareperformedinacommonuserfriendlyWindowstestcontrolenvironment.Itisafunctionofthetestobject,i.e.allanaloginputs-currentsandvoltages,thattherelaywillusewhenconnectedinthefield.Anexampleoftheseparameterswillincluderequirednumberofcurrentandvoltagegenerators,aswellasthebinaryinputstobeusedintheinterfacewiththetransformerprotection(Fig.3).二进制输出电压源电流源二进制输入多功能变压器保护测试系统测试对象Fig.3HardwareconfigurationsimplifiedblockdiagramThedifferenttestmodulesareusedfromwithinthecommoncontrolenvironment.Inthistypeofoperation,testmodulesareembeddedasobjectsandseveralmodulescanbecontrolledtogether.Thisway,transformerprotectionfunctionscanbetested,oneaftertheother,whileallcommonsettingscanbehandledgloballyanddonothavetobeinputforeachmoduleagain.Thetestmodulesmayberepresentedastestreportsthisallowscreationofareport,togetherwithtextfieldsandnormaltext.ThisreportisthenworkedthroughbytheControlCenterandfilledwithtestresults.Thiswaythedocument,istwothingsatatime:thegoalofthetest(thereport)andtheteststartingpoint(thetestspecifications).Thisreportcanbesavedandreusedatanytime.Alldifferentialprotectiontestmodulesareincludedinthestandardlibraryoftestmodulesandhaveasimilaruserinterface.Theyusethesamedialogforsettingtheparametersoftheprotectiondevice,thetestobjectandotherrelevantsystemparameters.Thedatasetthereismanagedgloballyandisavailableforuseineachofthetestmodules.V.CONCLUSIONSTestingofmodernmultifunctionaltransformerprotectiondevicesusingconventionalmethodsandtestequipmentisaverytimeconsumingandinmanycasesnotcompleteprocess.Automaticobject-orientedapproachtothetestingofsuchcomplexdevicesallowsforsignificantimprovementintheefficiencyandaccuracyofthetestprocess.Atestreportbasedtestprocedureconfigurationwithembeddedbasicanddevicespecifictestmodulessignificantlyreducestherequiredtestpreparationandresultanalysistimeandallowsthereuseofthedevelopedtesttemplateforanyfuturetestingofsimilartransformerprotectionrelay.Thisfurtherimprovestheefficiencyoftheoveralltestprocess.Testmoduledevelopmenttoolswithdifferentlevelsofcomplexityallowthecreationofanyrequirednewmodule,thussatisfyingtherequirementforadaptabilityoftheautomatictransformerprotectiontestsystem.中文译文多路受限输入的变压器差分继电器自动测试摘要：基于具有多个限制输入端的变压器差动继电器的先进微处理器测试使保护工程面临重大挑战。对于变压器不同的内部，外部故障或者使变压器保护继电器试验变得非常复杂和耗时的过载条件，多重保护功能有效性需要专业装置实现。本文讨论了每一个具体的保护功能大量测试的必要条件。一份报告中也介绍了多功能多限制的变压器差动继电器自动测试方法。对继电器的内部或外部故障、两相和单相接地故障进行测试。对硬件要求和自动测试的组态也进行了介绍。同时还介绍了一个变压器保护继电器作为一个测试对象的定义。报告的最后部分对不同的测试方法进行了初步探讨。关键词：变压器保护多功能微处理器继电器自动测试一、介绍变压器是一个典型的传输或配电变电站最昂贵的设备部分，在暴露的条件下，可造成各种各样不同程度的损坏。变压器的故障一般分为四类：（1）绕组和终端故障（2）铁心故障（3）不正常运行状态下，如过电压、过励磁、过负荷故障（4）持续的或不明确的外部故障上述所有条件都必须单独考虑，变压器保护方案相应地进行设计。为向变压器内部故障和正常运行、外部故障状态下的安全提供有效的保护，变压器保护中的设计和应用必须考虑以下因素，如:（1）励磁涌流（2）绕组布置（3）绕组连接（4）保护二次回路的连接基于继电器的多功能微处理器必须在任何潜在的破坏性故障或系统条件下，为最佳的性能和安全可靠运行提供足够的保护。这意味着，在任何变压器内部故障时继电器尽可能快地动作，同时，不应在任何外部故障条件运行。在任何其他非故障条件下，误操作也应避免，同时，即使变压器暴露持续时间显著，那么在有害条件下仍提供保护。电力变压器的设计，尺寸和结构的变化是极其重要的。这，在大量的可能的变压器保护中的应用中，结合了大量的变电站方案的使用效果。为了满足上述要求，当今先进的最新型的变压器保护继电器结合多重保护功能和有多限制输入的算法。这种多功能的微处理器继电保护的大量测试和不同的故障和非故障状态下的变电站的仿真环境是一个需要复杂的测试设备的耗时的任务。二、变压器保护继电器功能在变压器保护继电器中的主保护功能是差动保护。在正常的操作下，稳定状态的磁化电流和负载抽头的使用导致非平衡状态。为了适应这些条件，差动元件具有多坡特征。当变压器在其抽头变化范围的限制内允许多达15%个失配时，初始斜率保证内部故障时的灵敏度。大于额定电流时，附加错误可能逐渐地作为CT饱和的一个结果被引入。不同的限制坡度特征通常用于对此进行弥补。然而，差动元件的误操作通常可能发生在变压器通电过程中。高励磁涌流可能会发生，这取决于波动转换点以及变压器磁芯的磁状态。由于励磁涌流只有在通电绕组，差动电流结果中流动。在涌动条件下，当严重内部故障引起的二次谐波作为线电流互感器饱和的一个结果时，使用传统二次谐波抑来限制继电器可能会导致继电器显著延迟。为克服这一点，一些先进的继电器使用波形识别技术检测涌流状态。差动电流波形与磁化励磁涌流结合的特点是每个周期持续时间非常小，正如图1所示。通过测量这一时期的低电流时，可以确定涌流条件。在差动电流中涌动电流的检测用来抑制该相的低位算法。图表1.变压器涌流波形图当负载突然从电力变压器断开，在变压器的输入端的电压可能会上升额定值的10-20%，使变压器稳态励磁电流明显地增加。由此产生的励磁电流只流过一个绕组，因此作为差分电流出现，这个差分电流可能会产生一个足够高的值来启动差动保护。一个典型的电流波形如图2所示。这种类型波形的特点是存在五次谐波。傅立叶技术用于测量差分电流中五次谐波的水平。基本的五次谐波比用来检测励磁而且抑制差动保护功能。任一相的过励磁条件的检测限制那个特定相的低配置差分功能。图表2.多功能变压器保护测试对象具有很高的故障电流的变压器故障需要快速故障清除来减少电流互感器饱和的影响和对保护变压器的损害。一种不受控制的瞬时高设置差动元件确保终端故障的快速清除。此元件进行峰值测量来确保饱和CTS内部故障快速动作。高设置差动功能在励磁涌流或过励磁条件下不受限制，因此必须设置参数，这样当在流过预期最大涌流时，它将不工作。低电流绕组故障在故障谱的另一端，限制接地故障保护提供了接地故障更高的灵敏度。因此，限制接地故障保护保护了更多的绕组。每个绕组由一个单独的单元提供。需要一个外部电阻使饱和的线电流互感器稳定。限制接地故障保护依据高阻抗电流循环原理进行工作。当受到严重的故障，线电流互感器可能不均匀地进入饱和，导致失衡。三、传统的测试变压器保护从本文前面部分可以明显地看出，一种多功能的变压器保护装置使用传统方法测试不是一件容易的事。一个典型的变压器差动继电器通过采集高压侧单相电流和低压侧差动继电器输入电流，或只在高压侧采集三相电流。这只证明了差动元件将接收，但在真正实际生活中没有办法在故障或负载条件下应用。一般情况下，一个/Y连接的变压器，自耦变压器或一个带有一个接绕组的三绕组变压器（图2）不能通过这种途径进行测试。通过采集一个模拟外部故障中的单