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编号：时间：2021年x月x日书山有路勤为径，学海无涯苦作舟页码：第PAGE101页共NUMPAGES101页第PAGE\*MERGEFORMAT101页共NUMPAGES\*MERGEFORMAT101页影响电力系统运行的因素HazardstoPowerSystemOperation⑴Theoperationofelectricpowersystemsmaybedisturbedastheresultofanumberofcauses.Thetroublesontheelectriccircuitsareusuallyintheformofbrokenconductorsorcircumstancesinwhichconductorsaretemporarily(orpermanent)connectedtoeachotherortoground.Regardlessofthecauseofthedisturbances,suchtroublesseriouslyinterferewiththeflowofpowerandrequirecorrectiveaction.⑵Overheadlinesarevulnerabletotroublescausedbylightning.Whenlightningstrikesalineoranearbyobject,atransientvoltageiscreatedontheline,Hihg-voltagecircuitshavelargespacingbetweenconductorsandfromconductorstogroundedobjects,suchastowers.Directstrokestosuchlinesareusuallydivertedtogroundthroughoverheadgroundwiresandmaycausenointerferencewithoperation.Occasionallystrokesterminatedirectlyonthepowerconductorsandintroduceontothemtransienttransientvoltagesofsuchmagnitudethatarcheracrossinsulatorstringsmayresult.Onceanarcisestablished,powercurrentflowsthroughituntilthecircuitisdeenergized.Lightningvoltagesmaybeofhighmagnitudebutareofveryshortduration;theirtimeismeasuredinmicroseconds.Asaresult,theireffectsaremostnoticeableatthepointwherethestrokeoccurs.Distributionlines,whichoperateatperhaps12kVorless,aremountedonrelativelysmallinsulators,whichmaybeflashedoverbythevoltageinducedinalineeventhoughthelightningstrokedoesnotcontacttheline.Suchresultingarcsinterferewithoperationandusuallyareeliminatedbydeenergizingtheline.Whenthelineisdeenergized.Thearcisextinguishedand,verycommonly,thelinemaybereenergizingimmediately.⑶Overheadlinesaresubjectedtowindandsleet.Althoughdesignedtowithstandordinarystormloading,practicallytheycannotbedesignedfortheextremeconditionofsleetorwindloading.Hence,occasionallinefailuresoccurasaresultofthesecauses.Failurescausedbywindorsleetareusuallyofsuchnaturethatrepairsmustbemadebeforethelinemaybereenergize.⑷Foreignobjectsmaycontactalineandcausedamage
