毕业设计供配电类英文原文.docx

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1、附录二：英文原文ElectricpowerdistributionAnelectricpowerdistributionsystemisthefinalstageinthedeliveryofelectricpower;itcarrieselectricityfromthetransmissionsystemtoindividualconsumers.Distributionsubstationsconnecttothetransmissionsystemandlowerthetransmissionvoltagetomediumvoltagerangingbe

2、tween2kVand35kVwiththeuseoftransformers.Primarydistributionlinescarrythismediumvoltagepowertodistributiontransformerslocatednearthecustomer'spremises.Distributiontransformersagainlowerthevoltagetotheutilizationvoltageofhouseholdappliancesandtypicallyfeedseveralcustomersthroughseconda

3、rydistributionlinesatthisvoltage.Commercialandresidentialcustomersareconnectedtothesecondarydistributionlinesthroughservicedrops.Customersdemandingamuchlargeramountofpowermaybeconnecteddirectlytotheprimarydistributionlevelorthesubtransmissionlevel.HistoryFurtherinformation:Historyofe

4、lectricpowertransmissionElectricpowerdistributiononlybecamenecessaryinthe1880swhenelectricitystartedbeinggeneratedatpowerstations.Beforethatelectricitywasusuallygeneratedwhereitwasused.ThefirstpowerdistributionsystemsinstalledinEuropeanandUSciteswereusedtosupplylighting:arclightingru

5、nningonveryhighvoltage(usuallyhigherthan3000volt)alternatingcurrent(AC)ordirectcurrent(DC),andincandescentlightingrunningonlowvoltage(100volt)directcurrent.Bothweresupplantinggaslightingsystems,witharclightingtakingoverlargearea/streetlighting,andincandescentlightingreplacinggasforbu

6、sinessandresidentiallighting.Duetothehighvoltagesusedinarclighting,asinglegeneratingstationcouldsupplyalongstringoflights,upto7-mile(11km)longcircuits,sincethecapacityofawireisproportionaltothesquareofthecurrenttravelingonit,eachdoublingofthevoltagewouldallowthesamesizecabletotransmi

7、tthesameamountofpowerfourtimesthedistance.Directcurrentindoorincandescentlightingsystems(forexamplethefirstEdisonPearlStreetStationinstalledin1882),haddifficultysupplyingcustomersmorethanamileawayduetothelow110voltsystembeingusedthroughoutthesystem,fromthegeneratorstothefinaluse.TheE

8、disonDCsyste