外文翻译--供电技术

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1、外文原文PowerSupplyingTechnologyandIntelligentBuildingTheelectricdistributionsystemisapartofanelectricpowersystemthatsupplieselectricenergytotheindividualuserorconsumer.Thedistributionsubstationsthatsupplythem,thedistributiontransformers,andappropriateprotectiveandcontroldevicesthethreegeneralclassesof

2、individualuserareindustrial,residential,andruralThethree-phasealternating-current(ac)systemispracticallyuniversal,althoughasmallamountofdirect-currentsystemsareinoperation.Three-phasetransformerandsubtransmissionlinesrequirethreewires,learnedphaseconductors.Mostofthelow-voltagethreephasedistributio

3、nsystemsconsistofthreephaseconductionsandacommonorneutralconductor,makingatotaloffourwires.single-phasebranches(consistingoftwowires)suppliedfromthethree-phasemainsareusedforsinglephaseutilizationinresidences,smallstores,andfarms,loadsareconnectedinparalleltocommonsupplycircuits.Thedistributionsubs

4、tationisanassemblageofequipmentforpurposeofswitching,changingandregulatingthevoltagefromsubtransmissiontoprimarydistribution.MoreimportantsubstationsaredesignedsothatthefailureofapieceofequipmentinthesubstationoroneofthesubtransmissionlinestothesubstationwillnotcauseaninterruptionofpowertotheloadTh

5、eprimarysystemleavingthesubstationismostfrequentlyinthe6-35kVrange.AparticularvoltageusedisIlkline-to-lineand5.8kVfinetoneutral(conventionallywritten10/5.8kV).someutilitiesusealowervoltage,suchas3/1.7kVTheuseofvoltageinthe35kVclassisincreasingforitslowerelectricloss.Secondaryvoltagesarederivedfromd

6、istributiontransformersconnectedtotheprimarysystemandtheyusuallycorrespondtoutilizationvoltages.Mostloadsaresuppliedby380/220voltsingle-phasefour-wiresystems,somehighpower-ratemotorsrequire3kVor6kV.Goodvoltagemeansthattheaveragevoltageleveliscorrect,thatvariationsdonotexceedprescribedlimait,andthat

7、suddenmomentarychangesinleveldonotcauseobjectionablelightflicker.Utilizationvoltagevarieswithchangingloadonthesystem,butavoltagevariationoflessthan5%attheconsumer'smeteriscommon.toachievethisresult,distribu