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补全短文1P1FunctionsofpowertransmissionThefunctionof(powertransmission)istosendpowerfrompowerplantstoloadcenterortoexchangepowerbetweennetworksinordertoattainthegeneration-consumptionbalanceorthesupply-demandbalancebetween(powernetworks).Powertransmissioniscompletedbystep-upsubstations,(step-downsubstationsandconnectedtransmissionequipment).Thetransmissionlinemainlyconsistsofthetransmissionconductors(transmissionathighvoltage)canreducethelinelossandthevoltagedrop,ensurethepowerquality,raisetheeconomyof(powernetworkoperation).Theincreaseoftransmissionlinevoltagecannotonlyraisetheamountoftransmittedpower,butalsoreducethelinelossandlinevoltagedrop,andimprovethevoltagequality.功率传输功能（输电）的功能是要把电力从发电厂负荷中心或功率交换网络之间为了达到代消费平衡或供求之间的平衡（电网）。电力传输是通过升压变电站完成，（降压变电站和连接传输设备）。输电线路主要由输电导线（高压输电），可以减少线路损耗和电压降，保证电能质量，提高经济性（电网运行）。输电线路电压的增加不仅可以提高输电线路的传输功率，而且可以降低线路损耗和线路压降，提高电压质量。A.step-downsubstationsandconnectedtransmissionequipment降压变电站和连接传输设备B.powernetworkoperation电网运行C.powertransmission功率传输D.transmissionathighvoltage高压直流输电E.powernetworks一。电力网络P2AbriefintroductiononthedevelopmentofsupercriticalboilersandtheirmainadvantagesIn(someadvancedcountries)suchasU.S.A,JapanandEuropeancountries,thesupercriticalboilerhasbeendevelopedsincethe60soflastcentury.Ithasbeenprovedbydataandexperience,thesupercriticalunithas(greatadvantagesoneconomyandenvironmentalprotection).Asforitsreliability,becausethesteam-waterflowpassagesinsupercriticalboilerissameasthatinthe(subcriticalonce-throughboiler),thereisn’tanythingspecial,Butasfarashydrauliccharacteristic,asymbolofreliability,isconcerned,inasupercriticalboiler,undersupercriticalcondition,mediumisofsinglephasewhichhasa(goodhomogenizationofdistribution).Sothattheproblemcausedbyunevendistributionofsteamphaseandwaterphasecanbeavoided.Itisadmittedthat,if(wholeprocessmanagementisstrengthened),bothsupercriticalandsubcriticalunitscangetanexcellentreliabilityindex.超临界锅炉的发展及其主要优点在（发达国家）如美国，日本和欧洲国家，超临界锅炉已自上世纪60年代以来发达。数据和经验证明，超临界机组具有经济和环境保护的巨大优势。作为其可靠性，因为在超临界锅炉的水蒸汽流通道相同的作为，在的（亚临界直流锅炉），那里是没什么特别，但至于水力特性，可靠性的象征，有关，在超临界锅炉，超临界条件下，介质是单相（良好的同质化分布）。从而避免了汽相、水相分布不均造成的问题。这是承认，如果（全过程管理加强），超临界和亚临界机组可以得到一个极好的可靠性指标。A.goodhomogenizationofdistribution良好的均匀分布B.someadvancedcountries一些发达国家C.wholeprocessmanagementisstrengthened全过程管理加强D.greatadvantagesoneconomyandenvironmentalprotection具有经济和环境保护的巨大优势E.subcriticalonce-throughboiler亚临界直流锅炉P3CircuitbreakerCircuitbreakersareautomaticallyoperatedhighvoltage(orhighcurrent)switches.Circuitbreakersarerequired(tocontrolelectricalpowernetworks)byswitchingcircuitson,bycarryingloadandbyswitchingcircuitsoffundermanualorautomaticsupervision.Theirdutyisasfollows:Inclosedpositionthecircuitbreakermustbeagoodconductorforthenormalloadcurrent.Inoperatingthecircuitbreakermustbeablecontactsshallhavefullinsulationlevel.Atoperationthecircuitbreakermustclosebeable(toswitchthecurrentwhichcanbefromafewamperes)tomanythousandsofamperes,andindependentlyofthecharacteristicsfrompurelyinductivetofullycapacitive.Atclosingoperationthecircuitbreakermustclosefastandbesafealsoagainstfullshortcircuitconditions.Theymust,therefore,beeffective补全短文2instantaneouslywhenarecalledupon(toperformanyswitchingoperationafterlongperiods)withoutmovement.Asthecircuitbreakeristhelastlinkinthechainofprotectiveequipment,thecircuitbreakerreliabilityis(ofthehighestimportanceforhighreliability)ofthetotalelectricpowersystem.Sotheimportance(ofthecircuitbreaker)cannotbeoveremphasized.断路器断路器是自动操作高压（或大电流）开关。断路器是必需的（以控制电力网络）的开关电路，通过负载和开关电路的手动或自动监控。他们的职责如下：在闭合位置，断路器必须是正常负载电流的良好导体。在操作断路器必须能够接触应具有完全的绝缘水平。在操作断路器必须关闭能（开关电流可从几安培到几千安培），和独立的特点，从纯感性充分电容。在关断操作时，断路器必须要关闭快速，并能安全地进行全短路工况。因此，他们必须是有效的瞬间被调用时（长时间）执行任何切换操作不运动。断路器是保护设备链中的最后一个环节，其可靠性是全电力系统中（最高）的可靠性。因此，重要性（断路器）不能过分强调。A.toperformanyswitchingoperationafterlongperiods在长时间后执行任何切换操作B.tocontrolelectricalpowernetworks控制电力网C.ofthecircuitbreaker断路器的D.toswitchthecurrentwhichcanbefromafewamperes开关的电流可从几安培E.(ofthehighestimportanceforhighreliability高可靠性的最高重要性P4FuelcellsFuelcellsaredevicesthatwhenafuelsuchashydrogenorhydrogen-richcompoundsandoxygenaresuppliedtomaterialsarrangedliketheanodeandcathodeofaconventionalbattery,combinetoconvertchemicalenergydirectlyintoelectricalenergy.Unlikeconventionalbatterieswheretheconversionofchemicaltoelectricalenergyrequiresonlytheclosingofacircuitbetweenthecathodeandanodetoproduceandelectricalcurrent,(thereisnostoragecapacityinafuelcell).Thesecellsrequirethefuelandoxygenthatwillproducethechemicalreactionsthatproduceanelectricaloutput.Fuelcellshavebeenmadethatwillsupplypowerinthemegawattrange,and(furtherdevelopmentisunderway).Suchcellsarenotyetwidelyusedonpowersystems,but(astheyarebeingdevelopedtherehavebeensomeapplications)tosupplyfuelcellpowertoisolatedloads.Asthevoltageoutputofacellisintheorderofto2.5V,(manycellsareoperatedinseriestoobtainvoltages)andpoweroutputinrangesthatarenormallyrequired.Invertersareusedto(supplyalternatingcurrentfromfuelcells)whenandACoutputisdesired.燃料电池燃料电池是，当一个燃料如氢或氢化合物丰富和氧气供给排列像传统电池的阳极和阴极材料，结合转换化学能量直接转化为电能的装置。不像常规电池里的化学能转化为电能的需要只有闭合电路的阴极和阳极之间产生电电流，（有无储存能力的燃料