外文翻译-基于微处理器技术在继电保护中的应用

英文原文UNDERSTANDINGMICROPROCESSOR-BASEDTECHNOLOGYAPPLIEDTORELAYING1.INTRODUCTION1.1BriefHistoryofMicroprocessor-basedRelaysDifferenttehonlogieshavebeenusedinthepasttoimplementprotectionfunctionsthatproperlydetectdisturbancesinpowersystemsandinitiatethedisconnectionofthefaultedcomponents.Originally,electromechanicalrelayswereusedtoprotectpowersystems.Mostrelaysusedeitherelectromagneticattractionorelectromagneticinductionprinciplefortheiroperation.Plungertyperelaysformedinstantaneousunitsfordetectingovercurrentorover-voltageconditions.balanced-beamrelaysprovideddifferentialprotection,distanceprotectionaswellaslowburdenovercurrentunits.Theserelaysoperatedwhenthemagnitudeofanoperatingsignalwaslargerthanthemagnitudeoftherestrainingsignal.Theserelayswereclassifiedasamplitudecomparators.Singleinputinductiontyperelaysprovidedoperationswithtimedelays.Two-inputinductiontyperelaysprovideddirectionalprotection.Two-andthree-inputinductiontyperelaysalsoprovideddistanceprotection.Theoperationoftheserelaysdependedonthephasedisplacementbetweentheappliedelectricalinputs.Theserelayswereclassifiedasphasecomparators.Whensolid-statetechnologywasintroduced,amplitudeandphasecomparisonwereimplementedusingdiscretecomponentsincludingvacuumtubes.Inearly1960s,advancesintheintegrationofelectroniccircuitsmadethistechnologysuitableforuseinrelays.Themajoradvantageoftheserelayswasthatnomovingpartswereneededforperformingtheirintendedfunctions.Theoperatingspeedsoftheserelayswerealsomorethanthespeedoftheirelectromechanicalcounterpartsand,theirresettimeswerelessthantheresettimesoftheirelectromechanicalcounterparts.Inadditiontothesebenefits,thesolid-staterelayscouldbesetmorepreciselyandneededlessmaintenance.Solid-staterelaysappearedtobethetechnologypoisedtoreplacetheelectromechanicalcounterpartsinlate1960swhenresearchersventuredintotheuseofcomputersforpowersystemprotection.TheirattemptsandtheadvancesintheVeryLargeScaleIntegrated(VLSI)technologyandsoftwaretechniquesinthe1970sledtothedevelopmentofmicroprocessorbasedrelaysthatwerefirstofferedascommercialdevicesin1979.Earlydesignsusedthefundamentalapproachesthatwerepreviouslyusedintheelectromechanicalandsolid-staterelays.Multifunctionrelayswereintroducedinthemarketinthelate1980s.Thesedevicesreducedtheproductandinstallationcostsdrastically.Thistrendhascontinueduntilnowandhasconvertefdmicroprocessorrelaystopowerfultoolsinthemidernsubstations.1.2BenefitsofMicroprocessor-basedRelays.Whilethebasicprotectionpricipleshaveremainedessedtiallyunchangedthroughouttheevolutionofthemicroprocessor-basedrelays,theadoptionofthistechnologyhasprovidedmanybenefits,andafewshortcomings,comparedtotheprevioustehnologies.Thebenefitsandshortcomingsarediscussedinthissection.Theemphasisisoncompatringnthemicroprocessortechnologywiththeelectromechanicaltechnology.Comparisonwiththesolid-statetechnologyisalsoincludedasrequired.1.2.1MultiplefunctionsMicroprocessorrelaysprovidemanyfunctionsthatwerenotavailableinelectromechanicalorsolid-statedesigns.thesefeaturesincludemultiplesettinggroups,programmablelogic,adaptibelogic,self-monitoring,self-testing,sequence-of-eventsrecording,oscillography,andabilitytocommunicatewithotherrelaysandcontrolcomputers.1.2.2CostThecostperfunctionofmicroprocessor-basedrelaysislowercomparedtothecostoftheirelectromechanicalandsolid-statecounterparts.Thereductionincostisduetothelowercostofcomponents,productionequipmentandproductiontechniques.becausemicroprocessor-basedrelaydesignsincorporatecommerciallyavailableelectroniccomponents,theirproductlifeislimitedbytheprodctlifeofthecomponents.Manufactuerscontrol,ithasproventobeasignificantproblemwiththesolid-stateaswellasthemicroprocessor-basedrelays.1.2.3CustomlogicschemesAmajorfeatureofmicroprocessor-basedrelaysthatwasnotavailableinprevioustechnologiesistheabilitytoallowuserstodeveloptheirownlogicschemes,includingdynamicchangesinthatlogic.thisbenefit,however,comesatacostbecausethiscapabilityincreasesthecomplexityofthesystem.1.2.4SequenseofeventsandoscilographyReportingfeatures,includingsequenceofeventsrecordingandoscillographyareanaturalby-productofmicroprocessor-basedprotectionsystems.Thesefeaturesmakeitpossibletobetteranalyzetheperformanceofrelaysaswellassystemdisturbancesatminimaladditionalcosts.1.2.5Self-monitoringandslef-testingAnotheradvantageofmicroprocessor-basedrelaysistheirabilitytoperformself-monitoringandslef-testingfunctions.Therefeaturesreducetheneedforroutinemaintenancebecausetherelaysautomaticallytakethemselvesoutofserviceandalerttheoperatorsoftheproblemwhentheydetectfunctionalabnotmalities.1.3ShortcomingsofMicroprocessor-basedRelaysWhilemicroprocessor-basedrelayshaveseveraladvantages,theyalsohaveafewshortcomingsthatarenotdirectlyoffsetbysoecificbenefits.Majorshortcomingsarediscussedinthissection.1.3.1ShortlifecycleMicroprocessor-baseddevices,includingtheprotectionsystems,haveshortlifecycles.Whileeachgenerationofmicroprocessor-basedsystemsincreasesthefunctionalitycomparedwiththepreviousgeneration,thepaceofchangemakestheequipmentobsoleteinshortertimes.Thismakesitdifficultfortheuserstomaintainexpertiseinusingthelatestdesignsoftheequipment.1.3.2settingsandtestingcomplexityManymicroprocessor-basedrelays,whicharedesignedtoreplacethefumctionsofseveralsolid-stateorelectromechanicalrelays,offerprogrammablefunctionsthatincreasetheapplicationflexibilitycomparedwiththefixedfunctionrelays.Themulti-functionmicroprocessor-basedrelays,therefore,haveasignificantnumberofsettings.Theincreasednumberofsettingsmayposeproblemsinmanagingthesettingsandinconductingfunctionaltests.Setting-managementsoftwareisgenerallyavailabletocreate,transfer,andtracktherelaysettings.1.4MajorFunctionalBlocksofaTypicalMicroprocessorRelayThisrelaysamplesvoltagesandcurrents,which,atthepowersystemlevel,areintherangeofphundredsofkilovoltsandkiloamperesrespectively.Thelevelsofthesesignalsarereducedbyvoltageandcurrenttransformerstypicallyto67Vand5AnominalvaluesinNorthAmerica.2.ANALOGINPUTSThissectiondescribestheprocessofconvertinganalogsignalstosequencesofnumericalvalues.Theneedforpre-filteringisfirstdiscussed.ThesamplingandA/Dconversionarethendescribed.2.1Pre-filteringThemajorcomponentofapowersystemsignasisitsfundamentalfrequencycomponent.However,harmoniccomponentsarealsopresenttosomelevelsduetonon-linearitiesofthesystemandloads.Non-harmoniccomponentsarealsopresentduringfaults;thesearegenenatedbytravelingwavesandtheirreflectionsfromdiscontinuities.2.1.1AliasingItisnecessarythatanappropriatesamplingrateshouldbeusedforconvertinganalogsignalstosequencesofnumbersbecausehigh-frequencycomponents,whichmightbepresentinthesignal,couldbeincorrectlyinterpretedascomponentsoflowerfrequencies.Forappreciatingthisphenomenon,Thismisrepresentationofthehighfrequencycomponentasalowfrequencycomponentisreferredtsasaliasing.2.2SamplingSamplingistheprocessofconvertingacontinuoustimesignal,suchasacurrentorvoltage,toadiscretetimesignal.ThesamplingrateisusuallysetashighasispracticalconsideringthecapabilitiesofthemicroprocessorandA/Dconverter.Thepeakvalueofasinusoidalwaveformofasinglefrequencycanbemeasuredwithasampingrateaslowasthreesamplesinaperiod.Thesamplingrateoffoursamplespercyclewasusedinearlierrelayswhenthecapabilitiesofprocessorswerenotsufficienttohandledataobtainedbyusinghighersamplingrates.Morerecentnumericalrelaysusesamplingratethatareashighas96samplesperperiod.Acontinuoussignalissampledproperlyifthesamplesrepresenttheanalogsignaluniquelyandcontainenoughinformationtorecreatetheoriginalwaveform.Therecreationprocessisnotassimpleasdrawingstraightlinesbetweenthedatapointsbut,withtheuniquecollectionofmumericalvaluesofsamples,itcanbedone.2.3AnalogtoDigitalConversionAnalogtodigital(A/D)converterstaketheinstantaneousvaluesofthecontinuoustime(analog)signal,convertthemtoequivalentnumericalvaluesandprovidethenumbersasbinaryoutputsthatrepresenttheanalogsignalattheinstantsofsamping.3.PHASORESTIMATIONTECHNIQUESSeveralphasorestimationtechmiqueshavebeenproposedovertheyears.Thesetechniquescanbeclassifiedinthefollowingcategories.DiscreteFourierTransformCoseinealgorithmLeastsquaresalgorithmKalmanfilteringWavelettransformInthissection,DiscreteFourierTransform,Cosinealgorithmandleastsquarestechniquesaredescribed.Mostoftherelaysmarketedtodayuseoneoracombinationoftwoofthesetechniques.3.1LeastSquaresTechniqueLeastErrorSquares(les)techniqueisusedtoestimatethephasorsofthefundamentalandharmonicfrequencycomponentsofvoltagesandcurrents.Itisbasedonminimizingthemean-squareerrorbetweentheactualandassumedwaveforms.Thevoletageand/orcurrentwaveformismodeledasacombinationofthefundamentalfrequencycomponent,anexponentiallydecayingdccomponentandharmonicsofspecifiedorders.)sin()(010nNttVetvWhere:v(t)istheinstantaneousvalueofvoltageattimetisthetimeconstantofthedecayingdccomponentNisthehighestorderoftheharmoniccomponentpresentinthesignalisthefundamentalfrequencyofthesystem.03.2FrequencyResponseofAlgorthmsThemajorpurposeofanalgorithmistocalculatethemagnitudesandphaseanglesofphasors.Whilethealgorithmsperformthisfunction,theyalsohaveanaturalpropertyoffilatering.Thispropertycanbedeterminedbymathematicalanylysis,whichisdemonstratedinthissection.4.Microprocessor-basedrelaysestimatepowersystemfrequencyforseveralreasons.Afewofthereasonsareasfollows.1.Powersystemfrequency,alongwithothermeasurements,helpinanalyzingtheperformanceofrelaysaswellastheperformanceofpowersystemduringsteadystateandtransientoperations.2.Powersystemfrequency,estimatedbyarelay,canbeused(andisusedinsomerelays)forcontrollingtherateofsamplingvoltagesandcurrentstoensureaccurateoperationatallfrequenciesincludingtheoff-nominalfrequencies.Frequencyofaperiodicwaveformisaparameterthatisnotusuallymeasuredbutisestimatedfromasystemvoltageorcurrent.Distortionsinthesesignalsaffecttheaccuracyoftheestimatesseriously.Forexample,ifasimplezero-crossingdetectorisusedforestimatingfrequency,azero-crossinganomaly,whenacurrentisusedtomeasurefrequencyandcurrentreversaloccurs,couldhaveagreatimpactontheaccuracyofthemeasurement.Whenavoltageisusedtomeasurefrequency,aCVT-inductedtransientcouldadverselyimpacttheaccuracyofthemeasuredfrequency.Becauseofthesereasons,thealgorithmsformeasuringfrequencyaredesignedtomeasureitfromdataofseveralperiodsofthesignal.Outofthemanytechniquesthatareavailableformeasuringfrequency,zerocrossingandphasortrackingtechniquesaredescribedinthissection.4.1Zero-CrossingDetectionZero-crossingfrequencyestimationtechniqueisapopularmethodthatcanbeimplementedeitherinthehardwareorinthesoftwareofamicroprocessor-basedrelay.Themethodmeasuresthetimebetweentwozerocrossingsandcalculatesthefrequencyfromthatmeasurement.Thetimebetweentwoconsecutivezerocrossingsisone-halfthetimeofaperiodwhereasthetimebetweentwoalternatehalfcyclesisthetimeofoneperiodofthesignal.Othervariationsofthisapproachmeasurethetimebetweenaselectednumbersofzerocrossings.Thesemethodsusethefollowinggenericequation.f（tM）=（M-1）/2*（tM-t1）4.2Phasor-BasedMethodsThevoltageandcurrentphasorsestimatedfromquantizedsamplesbyusingtherelayingalgorithmsrotateattheirradianfrequencyasshowninFigure4.2.Thisfeatureallowsforthemeasurementoffrequencyfromconsecutiveestimatesofthephaseangles.Thegenericequationforthismethodisasfollows.4.3OtherMethodsSeveralotheralgorithmsforestimatingpowersystemfrequencyhavebeenpresentedintheliterature.Theyincludeapproachessuchasalinearregressionwithadaptiveon-linereadjustmentoftheinputfilter,leasterrorsquarestechnique,aNewton-typealgorithm,andaKalmanfilterbasedapproach.5.TIMEDOMAINALGORITHMSThealgorithmsbasedonelectricalpropertiesofsystemelementsareclassifiedasTimeDomainorModelingAlgorithms.Theseincludealgorithmsthatdeterminefaultsontransmissionlinesandtransformers.Whenafaultoccursonatransmissionline,thevoltageonthelinedepressesand,therefore,thelinechargingcurrentsareminimal.Ifthelinechargingisneglected,thelinecanbemodeledasaresistanceandinductanceconnectedinseries.Inthetransformermodel,themagnetizingcurrentsandthehysteresis-losscurrentsarenegligiblecomparedtofaultcurrents.Thetransformercan,therefore,bemodeledbytheresistancesandinductancesofthetransformerwindingsandthefluxlinkageswiththewindings.6.DATABASEISSUES6.1DataRecordingMostnumericalrelaysbeingmarketedatthistimehavebuilt-inwaveformandeventrecordingcapabilities.Therelaysenergizethetripcircuitscausingthecircuitbreaker(s)toopenforisolatingthefaultedelement.Thequantizedvaluesofsamplesofvoltagesandcurrentsareusuallysavedincircularbuffersthataresufficientlylargetorecorddatafromthepre-fault,faultandpost-faultperiods.6.2ManagingRelay-SettingFilesBeforetheuseofmicroprocessorsforpreparingandmaintainingrelay-settingdatabases,theyweremaintainedinsimpleforms.Thedatabasesusuallyconsistedofrelaytypes,purposeforwhichtheywereused,thelocationswheretheywereinstalledandtheirsettings.Theinformationwasusuallystoredatthecentralengineeringofficewherethedataweremaintainedbythoseresponsiblefortheirdevelopment.Therelay-databaseswereimportantbecausetheyprovidedquickoverviewofthesettingsbeingusedandmadeiteasytochangerelaysandimplementchangesintheirsettings.Thedatabaseswereabletogenerateprintedinstructionsforchangingrelaysettingsthatfieldpersonnelcouldfollow.Maintainingasingledatabasebyanelectricpowerutilitymadeiteasytosearchforspecificrelaytypesandothercommoninformation.7.PECIALPROCESSESAmultifunctionmicroprocessor-basedrelaycanhavemanyprotection,control,metering,andcommunicationsfunctionsthatseemtooperatesimultaneously.Generally,asingleprocessorisprovidedtoexecutethecodeanditcanonlyperformonetaskatatime.Thisaffectstheperformanceofanumericalmultifunctionprotectiverelay.Thedesignerstakethisintoconsiderationwhilestructuringtheembeddedfirmwaresothatthepowersystemprotectionfunctionsareexecutedinatimelymanner.8.TESTINGMicroprocessorrelayscanalsobetestedwiththeapparatususedfortestinganalogandelectromechanicalrelays.Thesignalsourcecouldbearelaytestset,playbacksimulatororarealtimesimulator.Incomparisontotheolderrelays,microprocessorrelaysusuallyhavegraphicaluserinterfaces(GUIs)tohelpinsettingtherelaysandingivinginformationonthetripevents.Thisinformationwouldincludeidentificationofelementsthathadtrippedandwhentheyhadtrippedaswellasproviderecordsofthewaveformsthatcausedthetrip.中文译文基于微处理器技术在继电保护中的应用1导言1.1微处理器继电器简史人们曾经利用各种不同的技术来准确监测电力系统干扰，发现故障部分的断开状态，以实施保护功能。起初，人们使用电磁继电器保护电力系统。大多数继电器操作时使用电磁引力或电磁感应原则。活塞型（电磁）继电器形成即时单元，检测过电流或过电压状态。平衡木继电器提供微分保护，距离保护和低负荷（用电需求）过电流单元。这些继电器只有在操作信号的数量大于限制信号的数量时才能进行操作。这些继电器被称为振幅比较仪。单输入感应继电器提供延时操作。这种继电器的操作依赖于输入电流之间的相位位移。这些继电器被称为相位比较仪。固态技术引入后，振幅和相位进行比较时使用包括真空管在内的离散成分。20世纪60年代初期，电子电路整合的发展使该技术在继电器中的应用成为可能。该继电器的主要优点是其在发挥既定功能时无须移动部分。该继电器无论在操作速度上还是在重设时间上都优于电磁继电器。除上述优点外，固态继电器设置精确，无需太多维护。20世纪60年后期，研究者尝试使用电脑保护电力系统，固态继电器取代了电磁继电器。20世纪70年代，研究者在大型整合技术和软件技术方面的尝试与进展开发出微处理器继电器。多功能继电器于20世纪80年代后期进入市场。这些装置大幅降低了生产安装成本。该趋势延续至今，微处理器继电器成为现代变电站的有力工具。1.2微处理机电器的优点虽然在微处理器继电器演变的过程中，基本的保护原则没有发生改变，但该技术的使用与之前的技术相比有利有弊。本节主要讨论微处理器继电器的优点与缺点。1.2.1多功能微处理器继电器具有许多电磁或固态设计所没有的功能。这些功能包括多重设计组，可编程的逻辑，适应逻辑，自我监控，自我测试，事件顺序纪录，示波法，与其他继电器和控制电脑进行交流的能力。1.2.2成本微处理器继电器的功能成本比电磁和固态继电器的功能成本低。成本降低是由于成分，生产设备和生产技术的成本降低了。1.2.3用户逻辑计划微处理继电器的一大特点是其允许用户开发自己的逻辑计划，包括逻辑的动态变化。然而，该优点是有代价的，因为该性能增加了系统的复杂性。1.2.4事件顺序与示波法包括事件顺序和示波法在内的记录特性是微处理器保护系统的天然副产品。该特性使人们能以最小成本分析继电器的性能和系统干扰。1.2.5自我监控预测试微处理器继电器的另一优势是其能发挥自我监控预测试功能。该特点减少了常规维护的必要，因为继电器可进行自动检测，当发现功能故障是会向操作者发出警告。1.3微处理器继电器的缺点本节主要讨论微处理器继电器的缺点。1.3.1使用寿命短包括保护系统在内的微处理器装置，其使用寿命比较短。虽然新一代微处理器系统与先前的系统相比功能增多，但变化的速度使设备在短期内被淘汰。1.3.2设置预测试的复杂性许多微处理器继电器提供可编程的功能，提高了使用的灵活性。因此，多功能微处理器继电器有许多设置，这给管理和功能测试带来困难。1.4典型微处理器继电器的主要功能板块该继电器取样电压和电流，在电力系统中，电压和电流分别可达几十万伏或几十万安。在北美，该数值可通过电流或电压转换器降低至67V或5A。2模拟输入本节主要描述模拟信号转变为序列数值的过程。先讨论预先过滤的必要性，然后描述取样/A/D转换。2.1预先过滤电力系统信号主要由纪初频率部分组成。然而，由于存在非线性系统与负载，谐波部分有时也出现。出现故障时还会有非谐波部分；这是由运动的波及其中断反射造成的。2.1.1混淆将模拟信号转变为数字时的取样速度应适当，因为信息中可能存在的高频率部分会被误认为低频率部分。取样顺序的重组和运算法则表明信号的频率为60Hz。这种将高频率误认为低频率的现象称之为混淆。2.2取样所谓取样，就是将电流或电压等连续的时间信号转变为离散时间信号的过程。考虑到微处理器和A/D转换器的性能，取样速度同唱越高越好。确定单个频率的正弦曲线峰值时，一段时期内只取样三次。如果样品代表模拟信号，包含足够信息重现原有的曲线，连续信号的取样就比较适当。重现过程不是单纯地在数据点之间画直线，而应收集独特的数值。2.3模拟数字转换模拟数字转换器获取持续时间的即时信息，将其转换为等值的数值，并以二进制输出，代表取样时的模拟信号。3相位估算技巧多年来，人们提出了许多相位估算的技巧。这些技巧可分为：余弦运算法则；最小平方法则；卡尔曼过滤本节我们主要讨论这些相