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電氣工程及其自動(dòng)化專(zhuān)業(yè)英語(yǔ)Protectionrelay(繼電保護(hù))
Anewerdevelopmentintheofpowersystemprotectionistheofcomputers(usuallymicrocomputers)forrelaying(計(jì)算機(jī)繼電保護(hù)).Althoughcomputersprovidethesameprotectionasthatsupplied(供應(yīng))byconventional(常規(guī))relays,therearesomeadvantagestotheuseofcomputer-basedrelaying.Thelogiccapability(邏輯能力)andapplicationexpansionpossibilities(應(yīng)用的可擴(kuò)展能力)forcomputer-basedrelayingismuchgreaterthanforelectromechanicaldevices(機(jī)電式繼電保護(hù)裝置).Computer-basedrelayingsamplesthevalues(采樣值)ofthecurrent,voltage,andotheritems(其他量)coveredintheprotectionscheme(在保護(hù)方案中)severaltimesasecond,andbyuseofA/Dconverters(轉(zhuǎn)換器),changetheseanalogvaluestodigitalformandthensendthemtothecomputer.Intheeventofafault(系統(tǒng)出現(xiàn)故障時(shí)),thecomputercancalculatethefault’scurrentvaluesandcharacteristics(故障電流的值和特性),andsettings(整定值)canbechangedmerelybyreprogramming(編程).Computer-basedrelayingarealsocapable(有能力的)oflocatingfaults(故障的定位),whichhasbeenoneofthemostpopularfeatures(最受歡迎的特征)intheirapplication.Inaddition,self-checkingfeaturescanbebuiltin(可配置自檢功能)andsequenceofeventsinformation(事件順序信息)canbedownloadedtoremote(遙遠(yuǎn))computersforfastanalysis(快速分析)ofrelayingoperations.Computer-basedrelyingsystemconsistsofsubsystemswithwelldefinedfunctions(功能明確的子系統(tǒng)組成).Althoughaspecificsubsystem(子系統(tǒng))maybedifferentinsomeofitsdetails,thesesubsystemsaremostlikelytobeincorporatedinitsdesigninsomeform(以某種形式融合在設(shè)計(jì)中).TheblockdiagraminFigure(框圖)13-1showstheprincipalsubsystemsofacomputer-basedrelaying(微機(jī)繼電保護(hù)的基本子系統(tǒng)的原理).Theprocessor(處理器)isthecenterofitsorganization(整個(gè)組合).Itisresponsible(主管,負(fù)責(zé))fortheexecutionofrelayingprograms(繼電保護(hù)程序的執(zhí)行),maintenanceofvarioustimingfunctions(各定時(shí)功能的保持),andcommunicatingwithitsperipheralequipment(與外部設(shè)備的通訊).Severaltypes(幾種不同類(lèi)型)ofmemories(存儲(chǔ)器)areshowninFigure13-1─eachofthemservesaspecific(具體的)need.TheRandomAccessMemory(隨機(jī)存取存儲(chǔ)器)(RAM)holds(保持,儲(chǔ)存)theinputsampledata(輸入采樣數(shù)據(jù))astheyarebroughtinandprocessed(送入被處理過(guò)).TheReadOnlyMemory(只讀存儲(chǔ)器)(ROM)orProgrammableReadOnlyMemory(可編程只讀存儲(chǔ)器)(PROM)isusedtostoretheprogramspermanently(永久性程序.).Insomecases(在某些情況下)theprogramsmayexecute(執(zhí)行)directly(直接)fromtheROMifitsreadtimeisshortenough.Ifthisisnotthecase(若不是這樣),theprogramsmustbecopiedfromtheROMintotheRAMduringaninitializationstage(在初始化階段),andthenthereal-timeexecution(實(shí)時(shí)執(zhí)行)wouldtakeplacefromtheRAM.TheErasablePROM(EPROM)(可擦寫(xiě)電存儲(chǔ)器)isneededforstoringcertainparameters(確定參數(shù))(suchastherelayingsettings(繼電器設(shè)定值))whichmaybechangedfromtimetotime,butonceitissetitmustremainfixed(保持不變)evenifthepowersupply(供電)tothecomputerisinterrupted(中斷).Therelayinginputs(繼電器的輸入)arecurrentsandvoltages─or,toalesserextent(程度較輕)─digitalsignalsindicatingcontactstatus(指示觸點(diǎn)狀態(tài)的數(shù)字信號(hào)).Theanalogsignalsmustbeconverted(轉(zhuǎn)換)tovoltagesignalssuitableforconversion(適合于轉(zhuǎn)換)todigitalform.Thecurrentandvoltagesignalsobtained(獲得)fromcurrentandvoltagetransformersecondarywindings(變壓器次級(jí)繞組)mustberestricted(限制到)toafullscalevalue(滿額值)of±10volts.Thecurrentinputsmustbeconverted(轉(zhuǎn)換)tovoltagesbyresistiveshunts(并聯(lián)電阻).Asthenormal(由于通常)currenttransformersecondarycurrents(電流互感器二次電流)maybeashundredsofamperes(數(shù)百千安),shuntsofresistance(并聯(lián)電阻)ofafewmilliohms(幾毫歐姆)areneededtoproducethedesiredvoltage(所需的電壓)forAnalogtoDigitalConverter(模擬數(shù)字轉(zhuǎn)換器)(ADC).Analternative(另一種)arrangement(辦法)wouldbetouseanauxiliarycurrenttransformer(輔助電流互感器)toreducethecurrenttolowerlevel.Anauxiliarycurrenttransformerserves(輔助電流互感器裝置)anotherfunction:thatofprovidingelectricalisolation(電氣隔離)betweentheminCTsecondary(電流互感器二次側(cè))andthecomputerinputsystem.(計(jì)算機(jī)輸入系統(tǒng))Sincethedigitalcomputercanbeprogrammedtoperformseveralfunctions(可編程來(lái)執(zhí)行這些功能)aslongas(只要)ithastheinputandoutputsignalsneededforthosefunctions(提供各種功能所需要的輸入和輸出信號(hào)).Itissimplemattertotherelayingcomputertodomanyothersubstationtasks(變電站的任務(wù)),forexample,measuringandmonitoringflows(測(cè)量和監(jiān)測(cè)潮流)andvoltagesintransformersandtransmissionlines(變壓器和輸電線路),controllingtheopeningandclosingofcircuitbreakersandswitches(控制斷路器和開(kāi)關(guān)的分閘和合閘),providingbackupforotherdevicesthathavefailed(對(duì)故障設(shè)備提供備用),arefunctionsthatcanbetakenoverbytherelayingcomputer.
Therearemanyperceivedbenefits(顯而易見(jiàn)的優(yōu)點(diǎn))ofadigitalrelayingsystem:1.Economics:withthesteadydecrease(逐漸下降)incostofdigitalhardware(數(shù)字型硬件),coupledwiththeincreaseincostofconventionalrelaying(再加上傳統(tǒng)繼電器花費(fèi)增加).Itseemsreasonabletoassume(假想)thatcomputerrelayingisanattractivealternative.Softwaredevelopmentcostcanbeexpectedtobeevenedout(預(yù)期將被均衡化)byutilizingeconomiesofscale(規(guī)?;玫慕?jīng)濟(jì)體)inproducingmicroprocessorsdedicatedtobasicrelayingtasks(在致力于生產(chǎn)微處理器作為基本繼電保護(hù)任務(wù)。).2.Reliability(可靠性):adigitalsystemiscontinuouslyactive(繼續(xù)發(fā)展)providingahighlevelofaself-diagnosis(提供一個(gè)高水平自診斷)todetectaccidentalfailureswithinthedigitalrelayingsystem(以檢測(cè)所述數(shù)字中繼系統(tǒng)內(nèi)的意外故障。).3.Flexibility(靈活性):revis
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