继电保护中英文翻译

1、继电保护中英文翻译(精)继电保护中英文翻译(精)继电保护中英文翻译(精)FundamentalsofprotectionpracticeThepurposeofanelectricalpowersystemistogenerateandsupplyelectricalenergytoconsumers.Thesystemshouldbedesignedandmanagedtodeliverthisenergytotheutilizationpointswithbothreliabilityandeconomy.Asthesetworequirementsarelargelyopposed,it

2、isinstructivetolookatthereliabilityofasystemanditscostandvaluetotheconsumer.Onehand,Thediagrammastmakesurethereliabilityinsystemdesign,.Ontheotherhand,highreliabilityshouldnotbepursuedasanendinitself,regardlessofcost,butshouldratherbebalancedagainsteconomy,taking.Securityofsupplycanbebetteredbyimpro

3、vingplantdesign,increasingthesparecapacitymarginandarrangingalternativecircuitstosupplyloads.Svidesflexibilityduringnormaloperationandensuresaminimumofdislocationfollowingabreakdown.Thegreatestthreattothesecurityofasupplysystemistheshortcircuit,whichimposesasuddenandsometimesviolentchangeonsystemope

4、ration.Thelargecurrentwhichthenflows,accompaniedbythelocalizedreleaseofaconsiderablequantityofenergy,cancausefireatthefaultlocation,andmechanicaldamagethroughoutthesystem,particularlytomachineandtransformerwindings.Rworkcannotbeguaran-teed.Theriskofafaultoccurring,howeverslightforeachitem,ismultipli

5、edbythenumberofsuchitemswhicharecloselyassociatedinanextensivesystem,asanyfaultproducesrepercussionsthroughoutthenetwork.Whenthesystemislarge,thechanceofafaultoccurringandthedisturbancethatafaultwouldbringarebothsogreatthatwithoutequipmenttoremovefaultsthesystemwillbecome,inpracticalterms,inoperable

6、.Theobjectofthesystemwillbedefeatedifadequateprovisionforfaultclearanceisnotmade.Noristheinstallationofswitchgearalonesufficient;discriminativeprotectivegear,designedaccordingtothecharacteristicsandrequirementsofthepowersystem.mustbeprovidedtocontroltheswitchgear.Asystemisnotproperlydesignedandmanag

7、edifitisnotadequatelyprotected.ProtectivegearThisisacollectivetermwhichcoversalltheequipmentusedfordetecting,locatingandinitiatingtheremovalofafaultfromthepowersystem.Relaysareextensivelyusedformajorprotectivefunctions,butthetermalsocoversdirect-actinga.c.tripsandfuses.Inadditiontorelaystheterminclu

8、desallaccessoriessuchascurrentandvoltagetransformers,shunts,d.c.anda.c.wiringandanyotherdevicesrelatingtotheprotectiverelays.Ingeneral,themainswitchgear,althoughfundamentallyprotectiveinitsfunction,isexcludedfromthetermprotectivegear,asarealsocommonservices,suchasthestationbatteryandanyotherequipmen

9、trequiredtosecureopera-tionofthecircuitbreaker.ReliablityTheperformanceoftheprotectionappliedtolargepowersystemsisfrequentlyassessednumerically.Forthispurposeeachsystemfaultisclassedasanincidentandthosewhichareclearedbythetrippingofthecorrectcircuitbreakersandonlythose,areclassedascorrect.Thepercent

10、ageofcorrectclearancescanthenbedetermined.Thisprincipleofassessmentgivesanaccurateevaluationoftheprotectionofthesystemasawhole,butitissevereinitsjudgementofrelayperformance,inthatmanyrelaysarecalledintooperationforeachsystemfault,andallmustbehavecorrectlyforacorrectclearancetoberecorded.Onthisbasis,

11、aperformanceof94%isobtainablebystandardtechniques.Completereliabilityisunlikelyevertobeachievedbyfurtherimprovementsinconstruction.Averybigstep,however,canbetakenbyprovidingduplicationofequipmentorredundancy.Twocompletesetsofequipmentareprovided,andarrangedsothateitherbyitselfcancarryouttherequiredf

12、unction.Iftheriskofanequipmentfailingisx/unit.theresultantrisk,allowingforredundancy,isx2.Wherexissmalltheresultantrisk(x2maybenegligible.Ithaslongbeenthepracticetoapplyduplicateprotectivesystemstobusbars,bothbeingrequiredtooperatetocompleteatrippingoperation,thatis,atwo-out-of-twoarrangement.Inothe

13、rcases,importantcircuitshavebeenprovidedwithduplicatemainprotectionschemes,eitherbeingabletotripindependently,thatis,aone-out-of-twoarrangement.Theformerarrangementguardsagainstunwantedoperation,thelatteragainstfailuretooperate.factors,suchascommoncurrenttransformersortrippingbatteries,willreducethe

14、overallperformance.SELECTIVITYProtectionisarrangedinzones,whichshouldcoverthepowersystemcompletely,leavingnopartunprotected.Whenafaultoccurstheprotectionisrequiredtoselectandtriponlytheneareatcircuitbreakers.Thispropertyofselectivetrippingisalsocalleddiscriminationandisachievedbytwogeneralmethods:aT

15、imegradedsystemsProtectivesystemsinsuccessivezonesarearrangedtooperateintimeswhicharegradedthroughthesequenceofequipmentssothatupontheoccurrenceofafault,althoughanumberofprotectiveequipmentsrespond,onlythoserelevanttothefaultyzonecompletethetrippingfunctiopn.Theothersmakeincompleteoperationsandthenr

16、eset.bUnitsystemsItispossibletodesignprotectivesystemswhichrespondonlytofaultconditionslyingwithinaclearlydefinedzone.Thisunitprotectionorrestrictedprotectioncanbeappliedthroughoutapowersystemand,sinceitdoesnotinvolvetimegrading,canberelativelyfastinoperation.Unitprotectionisusuallyachievedbymeansof

17、acomparisonofquantitiesattheboundariesofthezone.Certainprotectivesystemsderivetheirrestrictedpropertyfromtheconfigurationofthepowersystemandmayalsobeclassedasunitprotection.Whichevermethodisused,itmustbekeptinmindthatselectivityisnotmerelyamatterofrelaydesign.Italsodependsonthecorrectco-ordinationof

18、currenttransformersandrelayswithasuitablechoiceofrelaysettings,takingintoaccountthepossiblerangeofsuchvariablesasfaultcurrents.maximumloadcurrent,systemimpedancesandotherrelatedfactors,whereappropriate.STABILITYThisterm,appliedtoprotectionasdistinctfrompowernetworks,referstotheabilityofthesystemtore

19、maininerttoallloadconditionsandfaultsexternaltotherelevantzone.Itisessentiallyatermwhichisapplicabletounitsystems;thetermdiscriminationistheequivalentexpressionapplicabletonon-unitsystems.SPEEDThefunctionofautomaticprotectionistoisolatefaultsfromthepowersysteminaverymuchshortertimethancouldbeachieve

20、dmanually,evenwithagreatdealofpersonalsupervision.Theobjectistosafeguardcontinuityofsupplybyremovingeachdisturbancebeforeitleadstowidespreadlossofsynchronism,whichwouldnecessitatetheshuttingdownofplant.Loadingthesystemproducesphasedisplacementsbetweenthevoltagesatdifferentpointsandthereforeincreases

21、theprobabilitythatsynchronismwillbelostwhenthesystemisdisturbedbyafault.Theshorterthetimeafaultisallowedtoremaininthesystem,thegreatercanbetheloadingofthesystem.Figure1.5showstypicalrelationsbetweensystemloadingandfaultclearancetimesforvarioustypesoffault.Itwillbenotedthatphasefaultshaveamoremarkede

22、ffectonthestabilityofthesystemthandoesasimpleearthfaultandthereforerequirefasterclearance.SENSITIVITYSensitivityisatermfrequentlyusedwhenreferringtotheminimumoperatingcurrentofacompleteprotectivesystem.Aprotectivesystemissaidtobesensitiveiftheprimaryoperatingcurrentislow.Whenthetermisappliedtoanindi

23、vidualrelay,itdoesnotretertoacurrentorvoltagesettingbuttothevolt-ampereconsumptionattheminimumoperatingcurrent.Agiventypeofrelayelementcanusuallybewoundforawiderangeofsettingcurrents;thecoilwillhaveanimpedancewhichisinverselyproportionaltothesquareofthesettingcurrentvalue,sothatthevolt-ampereproduct

24、atanysettingisconstant.Thisisthetruemeasureoftheinputrequirementsoftherelay,andsoalsoofthesensitivity.Relaypowerfactorhassomesignificanceinthematteroftransientperformance.Ford.c.relaystheVAinputalsorepresentspowerconsumption,andtheburdenisthereforefrequentlyquotedinwatts.PRIMARYANDBACK-UPPROTECTIONT

25、hereliabilityofapowersystemhasbeendiscussedinearliersections.Manyfactorsmaycauseprotectionfailureandthereisalwayssomepossibilityofacircuitbreakerfailure.Forthisreason,itisusualtosupplementprimaryprotectionwithothersystemstoback-uptheoperationofthemainsystemandtominimizethepossibilityoffailuretoclear

26、afaultfromthesystem.Back-upprotectionmaybeobtainedautomaticallyasaninherentfeatureofthemainprotectionscheme,orseparatelybymeansofadditionalequipment.Timegradedschemessuchasovercurrentordistanceprotectionschemesareexamplesofthoseprovidinginherentback-upprotection;thefaultysectionisnormallyisolateddis

27、criminativelybythetimegrading,butiftheappropriaterelayfailsorthecircuitbreakerfailstotrip,thenextrelayinthegradingsequencewillcompleteitsoperationandtriptheassociatedcircuitbreaker,therebyinterruptingthefaultcircuitonesectionfurtherback.Inthiswaycompleteback-upcoverisobtained;onemoresectionisisolate

28、dthanisdesirablebutthisisinevitableintheeventofthefailureofcircuitbreaker.Wherethesysteminterconnectionismorecomplex,theaboveoperationwillberepeatedsothatallparallelinfeedsaretripped.Ifthepowersystemisprotectedmainlybyunitschemes,automaticback-upprotectionisnotobtained,anditisthennormaltosupplementt

29、hemainprotectionwithtimegradedovercurrentprotection,whichwillprovidelocalback-upcoverifthemainprotectiverelayshavefailed,andwilltripfurtherbackintheeventofcircuitbreakerfailure.Suchback-upprotectionisinherentlyslowerthanthemainprotectionand,dependingonthepowersystemcon-figuration,maybelessdiscrimina

30、tive.Forthemostimportantcircuitstheperformancemaynotbegoodenouugh,evenasaback-upprotection,or,insomecases,notevenpossible,owingtotheeffectofmultipleinfeeds.Inthesecasesduplicatehighspeedprotectivesystemsmaybeinstalled.Theseprovideexcellentmutualback-upcoveragainstfailureoftheprotectiveequipment,bute

31、ithernoremoteback-upprotectionagainstcircuitbreakerfailureor,atbest,timedelayedcover.Breakerfailprotectioncanbeobtainedbycheckinathatfaultcurrentceaseswithinabrieftimeintervalfromtheoperationofthemainprotection.Ifthisdoesnotoccur,allotherconnectionstothebusbarsectionareinterrupted,theconditionbeingn

32、ecessarilytreatedasabusdarfault.Thisprovidestherequiredback-upprotectionwiththeminimumoftimedelay,andconfinesthetrippingoperationtotheonestation,ascomparedwiththealternativeoftrippingtheremoteendsofalltherelevantcircults.Theextentandtypeofback-upprotectionwhichisappliedwillnaturallyberelatedtothefai

33、lurerisksandrelativeeconomicimportanceofthesystem.Fordistributionsystemswherefaultclearancetimesarenotcritical,timedelayedremoteback-upprotectionisadequatebutforEHVsystems,wheresystemstabilityisatriskunlessafaultisclearedquickly,localback-up,asdescribedabove,shouldbechosen.Idealback-upprotectionwoul

34、dbecompletelyindepen_dentofthemainprotection.Currenttransformers,voltagetransformers,auxiliarytrippingrelays,tripcoilsandd.c.supplieswouldbeduplicated.Thisidealisrarelyattainedinpractice.Thefollowingcompromisesaretypical:a.Separatecurrenttransformers(coresandsecondarywindingsonlyareusedforeachprotec

35、tivesystem,asthisinvolveslittleextracostoraccommodationcomparedwiththeuseofcommoncurrenttransformerswhichwouldhavetobelargerbecauseofthecombinedburden.b.Commonvoltagetransformersareusedbecauseduplicationwouldinvolveaconsiderableincreaseincost,becauseofthevoltagetransformersthemselves,andalsobecauseo

36、ftheincreasedaccommodationwhichwouldhavetobeprovided.SincesecurityoftheVToutputisvital,itisdesirablethatthesupplytoeachprotectionshouldbeseparatelyfusedandalsocontinuouslysupervisedbyarelaywhichwil1giveanalarmonfailureofthesupplyand,whereappropriate,preventanunwantedoperationoftheprotection.shouldbe

37、continuouslysupervised.d.Itisdesirablethatthemainandback-upprotections(orduplicatemainprotectionsshouldoperateondifferentprinclples,sothatunusualeventsthatmaycausefailureoftheonewillbelesslikelytoaffecttheother.继电保护原理发电并将电力供应给用户这就是电力系统的作用。系统要经过设计、组织,以使电力能够可靠、经济地送到用户2端。由于可靠和经济是两个相互对峙的要求,因此系统的可靠性和其所开销

38、用要综合考虑,一方面,系统设计时必定保证可靠性。而另一方面,不应该不计开销的盲目追求高可靠性,应该结合各方面因素综合考虑。改进设施设计能够更好地提高供电可靠性,比方增加备用容量裕度和安排多回路供电。将系统分段,有带保护装置的开关控制,这样能够在正常运行时有多种运行方式可供选择,而在故障时可将损失减少到最低程度。对供电系统最大的威胁就是短路,它经常使系统运行发生突然巨大的变化,巨大能量的局部释放产生的大电流,可以致故障点起火和贯穿系统的机械伤害,特别是对于电机和变压器线圈绕组。迅速断开离故障点近来的开关可减少损失并防范系统崩溃。一个电力系统就意味着特别巨大的投资。为最大限度地回收成本,系统应尽可

39、能多带负荷。因此不但要使系统在AB范围内(图1.1运行以吸引潜藏的用户,还要尽可能保证系统连续地满负荷运行,只有这样才能给用户带来最好的服务,供电刚才能获得最大收益。不能够保证设施和电网绝对不发生故障。诚然故障的危害对于单一元件是略微的,但经过大电网中亲近相关的众多元件,故障的危害就扩大了,这就是说任何一个故障有可能影响到整个电网。对于一个大电网,故障发生的几率和故障带来的扰动是相当大的,若是没有切除故障的设施,电网是不同样意运行的。没有相应的故障切除装置,就算安装了好多开关,电网的作用也不能够实现,还必定依照电力系统的特点和要求装备不同样的保护装置来控制开关。一个电力系统若是没有相应的保护,

40、它就不能够算是合理的设计和组织。保护装置保护装置是一个会集术语,它包括了所适用来检测、定位和触发切除电力系统故障的设施。继电器作为主要的保护功能元件而广泛使用。但保护装置还包括直接动作的交流脱扣器和熔丝。除了继电器,保护装置包括所有附件,诸如电流互感器、电压互感器、分流器、直流线圈、交流线圈以及其他与继电器相关的设施。一般来说,诚然开关设施也能起到基本保护的作用,但它不算是保护装置。公用设施,如电站蓄电池和其他用来保证开关动作的设施,也不属于保护装置。为了满足好多不同样配置、运行方式和建设性能的电力系统以最正确速度鉴别保护的要求,必定开发多各种类的继电器以反响电力系统量。比方,在某些情况下,不

41、过测量故障电流量就可以了,但在某些情况下,就有可能要测量功率和阻抗。继电器平时要测量好多复杂的系统量,这些量只有经过数学或图表方式才能方便地表达出来。可靠性为使大型电力系统的继电保护装置动作能以数字来谈论,每一个系统故障定义为一次事故,故障由且仅由正确的断路器来切除的,称为正确动作,由此可获得正确动作率。谈论的原则对于系统的整套保护给出了一个精确的公式,但它取决于继电器的动作,每一个系统故障需要好多继电器动作来切除,只有所有的继电器都正确动作才能看作一次正确动作。有基于此,标准的技术设施能达到94%的正确动作率。即使在施工时做了进一步改进,要达到百分之百的可靠性也是不能能的。双重化配置可大大提

42、高可靠性,两套装置中的任何一套均可达到所要求的功能。若一套装置的故障风险为x/套,采用双重化配置后,风险为x2,由于x很小,x2可忽略不计。实质上母线保护早就采用了双重化配置。两套装置均动作以完成跳闸操作,这就是“2取2”配置。在另一些情况下,重要回路的主保护采用双重化配置,每一套装置能独立完成跳闸操作,这就是“2取1”配置。前一种配置是为了防范误动,后一种配置是为了防范拒动。以上两个功能能够相互结合,生成“3取2”配置,也就是结合使用三套同样的装置,任何两套装置动作均可实现跳闸功能。这种设计方案已在一小范围内使用,而该原理的应用将日渐广泛。若是一个电网采用这种设计方案,用概率论能够得出这样一

43、个结论,即保护正确动作率可达99.8%。这种正确动作率指标要求单独的保护装置完满独立,任何公用因素,如公用的电流互感器、跳闸用蓄电池,将降低正确动作率。选择性保护是分地域部署的,这样整个电力系统都获得了保护,而不存在保护死区。当故障发生时,保护应有选择地动作,跳开距离故障点近来的开关。选择性跳闸也称为“鉴别”,一般可经过以下两种方法实现:分时限保护挨次分区的保护装置被设计成分时限动作,这样当故障发生时,诚然有多套装置响应,但只有那些与故障地域相关的装置实现跳闸功能,另一些不完满动作尔后复归。单元保护能够将保护装置设计成只响应某一特定地域的故障,这种“单元保护”或“限制保护”可在整个电力系统内使

44、用。由于它不带延时,相对来说可迅速响应动作。单元保护平时以比较地域界线量来实现。某些保护装置由于电力系统的部署而拥有“限制”特点的,也可称为单元保护。无论采用何种方法,必定注意选择性不不过依靠继电器设计,它还同时依靠合适整定的继电器与电流互感器的正确配合。要考虑到以下变量的变化范围:如故障电流、最大负荷电流、系统阻抗和其他相应的因素。牢固性保护装置的牢固性与电网的牢固性看法不同样。它是指所有负荷状态和区外故障都不会使装置动作。它实际上是相对单元保护而言的,而对非单元保护则以“鉴别率”来表示。速度自动保护的作用就是在特别短的时间内切除电力系统故障,而该时间若使用人工手段则不能能实现,就算采用大量的人员监察也不能够。其目的是使每一个扰动在以致失步扩散甚至造成设施停机前就除掉它,