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电气毕业设计外文文献翻译

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'河南理工大学万方科技学院本科毕业论文附录:外文资料与中文翻译外文资料:SelectionandCoolingofPowerTransformerTheselectionofthetransformercanhaveamajorimpactonthecostofasubstation,sincethetransformerrepresentsthemajorcostitem.Nameplateratingisonlyaguidetotransformerapplication,andshouldonlybeusedasafirststepintheselectionprocess.Thetransformerisavailableasaself-cooledunit,oritcanbepurchasedwithadditionalstepsofforcedcoolingthatusefanorfansandoilpumps.Thenameplateratingscanbeincreasedfrom25%to66%bytheadditionoffanspumps.Thenameplateratingisbasedonacontinuousloadproducinga550Cto650Cconductortemperatureriseoverambient.Sincemanytransformersdonotcarrycontinuousloads,advantagecanbegainedfromthethermaltimelagtocarryhigherpeakloadswithoutexceedingthetemperaturelimits.Transformerratingsarebasedontheassumptionthatonlyanextremelyslowdeteriorationofinsulationwilltakeplacewithnormaloperation.Asubstantialincreaseinratingcanbeachievedbyacceleratingthelossofinsulationlife,Thisincreaseinratingmightapproach200%foranhourortwo,andapproximately120%for24hours.Forsubstationsthataredesignedtocarryfullloadundertheoutageofanyonetransformer,ahighemergencyratingfora24-hourperiod(e.g.Untilthefailedunitcanbereplaced)couldmeantheselectionofsmallertransformer 河南理工大学万方科技学院本科毕业论文andasubstantialsavinginsubstationcost.Theselectionofthetransformershouldinvolveacarefulevaluationofanumberofotherfactors:(1)Impedancesshouldbeselectedconsideringtheireffectonshort-circuitdutiesandlow-sidebreakerratingsbothforinitialandfuturestationdevelopments.Inaddition,impedanceisimportanttoachieveadivisionintheparalleloperationoftransformer.(2)Noloadtaprangesshouldbeselectedtoprovideanadequatelow-sidebusvoltage.(3)Ifthehigh-sideorlow-sidevoltagesvaryoverawiderangeduringtheloadcycle,itmaybenecessarytoprovidebusregulation.Theactualregulationcanbecalculatedusingthesystemandloadcharacteristics.Ifregulatingequipmentisneeded,itmaybedesirabletoprovideitinthetransformerbyusingloadtapchanger(LTC)equipment.Iftheneedforbusregulationisnotpresentlyevident,butmayberequiredinthefuture,itmaybeeconomicaltoleavespaceinthestationforfutureregulators,andbuytransformerswithoutLTCequipment.Agreatmanytransformers,includingallthelargeonesandallthehighvoltageonesareimmersedinmineraloilwhichservesthedoublepurposeofcoolingandinsulatingthewindings.Smalltransformershaveenoughtanksurfacetoradiatealltheheatcausedbytheirlosseswithoutexceedingthepermissibletemperaturerise.Assizeincreases,thelossesincreasefasterthanthetanksurfacewhichsoonbecomesinadequate.Variousmethodshavebeendeveloped 河南理工大学万方科技学院本科毕业论文togettheheatoutofthetankmoreeffectively.Largepowertransformerbeingbuilttodayarecommonlyoftheforced-oil-cooledtype.Inthisdesigntheoilispumpedboththroughtheexternalcoolingdevices(airorwaterheat-exchangers)andthroughinternalchannelsthatarelocatednearestthepointswheretheheatisgenerated,Thusthetransferofheattoandfromtheoilisfarmoreeffectivethanintheplainself-cooledorfan-cooledunitwheretheoilisallowedtocirculatebyconvection.Whenoil-to-airheatexchanger(agroupfansoneachradiator)isused,thiscoolingtypeisdesignatedastypeofFOA.Whileoil-to-waterheatexchangerisused,itiscalledFOW.Forapplicationswhereanyliquid,evenanonflammableone,isobjectionable,thedry-typetransformerisused.Theventilateddry-typeunitiscooledbyacontinuousnaturaldraftofairandconsequentlyisnotsuitableforlocationswheretheairiswetordirty.Fortheselocationsacompletelyenclosedunit,thesealeddry-type,isavailable,havingacore-and-coilinatankthatissealedandfilledwithaninsulatinggas,Dry-typetransformersarecompletelynonflammable,usingorganicmaterialsuchasepoxyresin.UnattendedSubstationandSubstationAutomationThedevelopmentofautomaticreclosingmadetheunattendedsubstationpractical.Automaticoperation,withoutthecontinuous 河南理工大学万方科技学院本科毕业论文presenceofanattendant(operator),wasfirsttriedonthesynchronousconvertersubstationssupplyinganinterurbanelectricrailwayin1914.Intheearly1920s,thedevelopmentofautomaticreclosing,protectiverelays,andmeansforautomaticcontrolofvoltagemadeitpossibleforACsubstationstobecompletelyautomatic.Duringtheperiodwhenthesubstationshadtobecontrolledmanually,itwasnecessarythattheyhandleenoughpowertojustifytheoperator"swages.Thisdictatedlargestations,frequentlyservinglargeareasbymeansofmanyfeeders,Thefeedersthatservedthemoredistantpartsofanareahadtogoalongwaybeforetheypickedupanyload.Furthermore,astheloadonalargesubstationgrows,transformercapacityhastobeadded.Thisincreasestheshort-circuitcurrentonthesecondaryside;sometimestheshort-circuitcapacityexceedstheinterruptingcapacityofthecircuitbreakersalreadyinstalled.Appropriateremediesincludebussectionalizing,theinstallationofreactorsorsomecombinationofthetwo.Suchmeasuresarefrequentlyexpersiveandinconvenientandtheyconstituteanundesirablelimitationonoperatingflexibility.Oncetheunattendedsubstationbecameareality,thesubstationcouldbemadesmaller,locatednearertheload,andlongfeederswerenolongernecessary.Thisnewmethodofdistributionhadbecomeavailablesinceloadgrowthcouldnowbeaccommodatedbyinstallinganothersubstationthatcouldcarrypartsofthearealoadsformerlycarriedbyadjacentsubstations.Usually,thereisnointerconnectionbetweenthecircuitsenergizedbythevarioussubstations.Consequently,thereisnoincreaseinshort-circuitseverity.However, 河南理工大学万方科技学院本科毕业论文atthedistributionlevel,tieswitchesareusedtoswitchfeedersorfeedersectionsbetweentransformersinthesamestationortoadjacentsubstationsforsubstationtransformerloadmanagement.Automaticcontrolhasbeenappliedtolargerandlargersubstations,andomanyhydroelectricgeneratingstations.Itisalsousedonindividualcircuitsandequipmentinmanyattendedstations.Forexample,eveninmanystationswhereanoperatorisonduty,outgoingoverheadfeedersarecontrolledbyautomaticreclosingrelays.Undersomecircumstances,itmaybeimpracticaltomakeastationcompletelyautomatic.Thesecircumstancescouldexistbecauseoftechnical,economic,orsafetyconsiderations.Astationneednotbeattendedeventhoughitisnotfullyautomatic.Itispossibletocontrolastationfrombedonebymeansofsupervisorycontrol(aformofremotecontrol).BymeansofaSCADAsystem,anoperatoratadispatchcentercancauseoperationssuchastheopeningandclosingofbreakers,thestartingandstoppingofcondensers,andthechangingofthetapsontransformerswithloadtapchanger.Theoperatorcanreceiveamindicationhasbeencompleted.Allofthiscanbedoneoveravoice-gradecommunicationchannelsthatdistinguishessupervisorycontrolfromdirect-wireremotecontrolrelaysrequiredforautomaticcontrol.Alloftheprotectiverelaysandmostofthecontrolisused.Onlytheinitiatingdevicesmaybedifferentoromitted.Forexample,afullyautomaticsynchronouscondenserisstartedandstoppedbyaninitiatingdevicesarestillnecessary,andonlytheinitiatingdevicescanbeomitted. 河南理工大学万方科技学院本科毕业论文Withtherecentrevolutioninmicroelectronicperformanceandcosts,digitalautomationsystemsarenowbeingdevelopedforpowersystems.Theseautomationsystemsprovideanintegratedsystemsconceptforprotection,control,andmonitoringfunctions.Theapproachutilizesdistributedmicroprocessor-basedmoduleslocatedwithinthesubstationsandoutonthetransmissionanddistributionsystem.Thisprovidesprotectionandcontroldecisionsoutonthesystemwherethedataislocated.Byautomatictransmissionanddistributionsystems,majorbenefitswillbeobtained.Theseincludegreaterutilizationofexistingfacilities,reductionofcommunicationrequirements,deferralmajorsysteminvestments,optimizedoperationsandmaintenance,improvedsystemreliability,moreefficientsystemoperationthroughlowerlossesandrapidrestorationofserviceafterafault.Thefunctionsimplementedbyusingthisintegratedsystemsapproachinclude:Transmissionsubstationautomationfunctionsanddistributionsubstationandfeederautomationfunctions.中文翻译:电力变压器的选择和冷却变压器的选择对变电站的造价有主要的影响,因为变压器为变电站造价的主要项目。铭牌额定值仅是变压器应用的一个指导,只是选择过程的第一步。可选用自冷式变压器,也可购买带有风扇或风扇加上油泵这种强迫冷却措施的变压器。增加风扇和油泵可使变压器额定值增加25%到66%。铭牌额定值是以产生至 河南理工大学万方科技学院本科毕业论文导线温升的持续负荷为依据的。由于许多变压器并不带持续负荷,这就可利用发热时间的滞后来带上更高的峰值负荷而不至于超出温升的限定值。变压器的额定值是以这样的加大为依据的,即正常运行时的绝缘仅发生极缓慢的老化。过度超出额定容量讲加速绝缘寿命的缩短。负荷增大到200%额定值时可运行1或2小时,增大到约120%额定值时刻运行24小时。对于设计为任何一台变压器停运时仍能带满负荷的变电站,其24小时的高紧急情况额定值可能意味着可选择容量较小的变压器,这可大大节省变电站的造价。选择变压器时应仔细评估一些其他的因素:(1)阻抗的选择要考虑它们对短路负荷的低压侧断路器额定值的影响作用,变电站初期情况和奖励的发展都要考虑到。此外,要实现变压器并联运行时的恰当负荷分配,阻抗值是重要的。(2)区在分解范围选择应能提供正确的低压侧母线电压。(3)若在负荷变化周期中,高压侧或低压侧的电压有较大范围的变化,就有必要提供母线电压的调节。实际调节量可利用系统特性和负荷特性来计算。若需要调节设备,可要求在变压器中采用有载分接开关(LTC)设备。若目前对母线电压调节并不明确需要,但将来可能需要,较为经济的做法是在变电站中留有将来装电压调节器的地方,购买不带LTC设备的变压器。 河南理工大学万方科技学院本科毕业论文大量的变压器,包括所有的大型变压器和所有高压变压器时浸于矿物油中的,矿物油起冷却和将绕组绝缘的双重作用。小型变压器具有足够的油箱表面积来散发所有由损耗引起的热而使之不超过允许的温升。随着容量的增大,损耗的增大要超过油箱的表面积的增大,因而表面积就不够了。已经研究了各种方法使热量更有效地从油箱中散发出来。大型变压器通常为强迫油冷型的。在此种类型的设计中,用油泵使油通过外部的冷却装置(空气或水热交换器)和通过最靠近热产生部位的内部通道,这样热被转移至油,并再从油转移走,从而就比普通子冷或风冷式变压更为有效,因此时变压器油被循环而不只是对流。当采用油--空气热交换器(每个散热器上一组风扇)时,此种冷却方式成为FOA。而当采用油--热水交换器时,此种冷却方式称为FOW。在液体甚至是不可燃特提不允许使用的场所,就采用干式变压器。风冷干式变压器通过持续的自然通风来冷却,因此不适合于潮湿或多尘的场所。对于这些场所,采用全封闭的干式变压器,在箱体中充以绝缘气体来隔绝铁芯和线圈。干式变压器的完全不燃的,采用如环氧树脂这样的有机材料。无人值班变电站与变电站自动化自动重合闸的研制使无人值班变电站得以实现 河南理工大学万方科技学院本科毕业论文。在无人连续值班下的自动操作,首次于1914年在一个向电气化铁路供电的同步换流站中尝试。二十世纪二十年代初期,由于自动重合闸、保护继电器及电压自动控制设备的研制,使交流变电站有可能完全自动化。变电站须手动控制时,运行人员必须管理足够多数量的电力,才能使运行人员的工资较合理。这就决定了要采用大型变电站,一般通过许多馈电线向大的地区供电。向较远地区供电的馈电线在带负荷前需经过较长的输电距离。此外,随着大型变电站的负荷增长,变压器的容量也必须增加。这样就增加了二次侧的短路电流。有时,短路容量会超过已安装断路器的开断容量。合适的补救措施包括母线分段、安装电抗器、或者这两者的组合。这样的措施通常代价昂贵并不方便,且对运行的灵活性构成不必要的限制。一旦无人值班变电站得以实现,变电站就可以造的更小,更靠近负荷,也不再需要长的馈电线路了。此新配电方法之所以可以被采用,是因为增加的负荷可被另外安装的变电站来承担,新安装变电站就可承担原先要由邻近变电站来承担的负荷。通常,由不同变电站送电的线路之间无相互联接。因此,不会增大短路的严重性。然而在配电等级,联络开关用来开合同一变电站中不同变压器上的馈线或馈线段,或切换到邻近变电站以进行变电站变压器的负荷管理。自动控制已在越来越大的变电站,以及许多水电站中得到应用。自动控制也被用于有人值班变电站的线路和设备。例如,许多变电站中,即便有人值班,架空馈电出线也由自动重合闸继电器控制。在某些情况下,变电站完全自动化是做不到的。出线这些情况的原因可能是出于技术性、经济性或安全的考虑。即使一变电站并不是全自动化,也不一定需要值班。这可从另一地方,如更大的有人值班变电站或运行中心来控制。通过监控(一种遥控)就可以做到。 河南理工大学万方科技学院本科毕业论文借助于SXADA系统,运行人员可在调度中心进行操作,如断路器的分闸和合闸,调相机的起动和停止,改变有载分接开关变压器上的分接头。运行人员可接收到操作已完毕的单独指示。所有这些都可通过话音级的通信通道来实施。话音级双路通信通道的采用是监控与专线控制的区别。对于专线控制,每个被控设备都需要一条专线。SCADA设备对自动控制起补充作用。采用监控时所有自动控制需要的保护继电器和大部分控制继电器仍是必需的,仅是启动设备不同或省略,例如,全自动调相机由相应于电压或电流,或两者组合的启动设备来启动或停止。此外,还有许多保护继电器和控制继电器。若调相机通过监控来控制,其他所有设备仍都需要,仅启动设备可省略。随着微电子技术性能和价格上的革命,数字式自动化系统现已研制用于电力系统。这些自动化系统将保护、控制、监视功能综合于一体。此方法利用在输配电系统中和在变电站内分布的微处理机模块,这为数据所在的系统提供了保护控制。采用输、配电系统自动化后将带类重大好处,这包括更好利用现有设施、减少通信需求、推迟系统重大投资、优化运行和维修、提高系统可靠性、系统损耗更小而高效运行、故障后更快恢复供电。采用此综合系统方法所执行的功能包括:输电变电站自动功能和配电变电站及馈线自动功能。'