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1、浙江大學碩士學位論文ABSTRACTWiththerapidlygrowthofconstruction—landprice，double—circuittransmissionlinesonthesametowerarewidelyusedtOincreasethetransmissioncapacityinthesamewidthofthetransmissioncorridoratpresent．Comparedwithregularsingle—circuittransmissionlines，thedouble-circui

2、ttransmissionlinesfacemoreseriouslightning-protectionproblems，inwhichsimultaneoustrip—outcausedbylightningstrokeistheworst．Howtoavoidthesimultaneoustrip—outaccidentsindouble-circuittransmissionlinesbecomesthekeyissuethatseriouslyaffectsthestabilityofthepowergridandneedt

3、obesolvedassoonaspossible．Inthispaper,electromagnetictransientprogram(EMTP)isusedtorecurtheaccidentswhichhappenedin220kVdouble—circuitlinesinpractice，andthesimultaneoustrip·-outmechanismindouble-·circuittransmissionlinesonthesametowerisrevealed．Thestudyshowsthat：althoug

4、hthepowerfrequencyvoltageisnottheprimarycauseoflightningflashover，ithasasignificantimpactontheflashoversequenceoftheconductors；groundingresistancehasagreatimpactonthelightningwithstandlevel，itissuggestedthatthegroundingresistanceofthedouble—circuittransmissionlinesonthe

5、sametowerisnotlargerthan10Qinheavylightningarea．Thispaperalsoanalysestheapplicationeffectoftheunbalancedinsulationondouble—circuittransmissionlines．Theresultsshowthatbymeansofensuringenoughdifferencebetweeninsulationlevelsforthetwocircuits．itcanmakesurethatwhendoublecir

6、cuittransmissionlinesonthesametowerislightning—strickenthephase·to—phaseflashoveronlyhappensatthecircuitwiththelowerinsulationlevel，thereforetheseriousfaultofsimultaneoustrip—outoftwocircuitscanbeavoidedatthecostoftrip—outofonecircuit．Calculationresultsshowthatwhenthede

7、greeofinsulationunbalancednessfordouble220kVor1l0kVcircuittransmissionlinesonthesametowerreachesto30％，orinotherword，thedifferenceininsulatorpiecesofastringbetweentwo220kVcircuitsortwo10kVcircuitsis4or3pieces浙江大學碩士學位論文respectively,theunbalancedinsulationcanrestrictthecir

8、cuit，wherephase．to．phaseflashoverhappens．Besides，theeffectofsuchameasureisreliableandsuitablefordoublecircuitt