电子类英汉词典.doc

《电子类英汉词典.doc》由会员上传分享，免费在线阅读，更多相关内容在应用文档-天天文库。

1、影响电力系统运行的因素HazardstoPowerSystemOperation⑴Theoperationofelectricpowersystemsmaybedisturbedastheresultofanumberofcauses.Thetroublesontheelectriccircuitsareusuallyintheformofbrokenconductorsorcircumstancesinwhichconductorsaretemporarily(orpermanent)connectedtoeachotherortoground.Regardlessoft

2、hecauseofthedisturbances,suchtroublesseriouslyinterferewiththeflowofpowerandrequirecorrectiveaction.⑵Overheadlinesarevulnerabletotroublescausedbylightning.Whenlightningstrikesalineoranearbyobject,atransientvoltageiscreatedontheline,Hihg-voltagecircuitshavelargespacingbetweenconductorsandfr

3、omconductorstogroundedobjects,suchastowers.Directstrokestosuchlinesareusuallydivertedtogroundthroughoverheadgroundwiresandmaycausenointerferencewithoperation.Occasionallystrokesterminatedirectlyonthepowerconductorsandintroduceontothemtransienttransientvoltagesofsuchmagnitudethatarcheracros

4、sinsulatorstringsmayresult.Onceanarcisestablished,powercurrentflowsthroughituntilthecircuitisdeenergized.Lightningvoltagesmaybeofhighmagnitudebutareofveryshortduration;theirtimeismeasuredinmicroseconds.Asaresult,theireffectsaremostnoticeableatthepointwherethestrokeoccurs.Distributionlines,

5、whichoperateatperhaps12kVorless,aremountedonrelativelysmallinsulators,whichmaybeflashedoverbythevoltageinducedinalineeventhoughthelightningstrokedoesnotcontacttheline.Suchresultingarcsinterferewithoperationandusuallyareeliminatedbydeenergizingtheline.Whenthelineisdeenergized.Thearcisexting

6、uishedand,verycommonly,thelinemaybereenergizingimmediately.⑶Overheadlinesaresubjectedtowindandsleet.Althoughdesignedtowithstandordinarystormloading,practicallytheycannotbedesignedfortheextremeconditionofsleetorwindloading.Hence,occasionallinefailuresoccurasaresultofthesecauses.Failurescaus

7、edbywindorsleetareusuallyofsuchnaturethatrepairsmustbemadebeforethelinemaybereenergize.⑷Foreignobjectsmaycontactalineandcausedamage,whichnecessitatesremovalofthelinefromservice.Airplanesmayflyintoaline,anautomobilemayknockapole,aconstructionworkermayrunacranei