特高压GIL非均匀热气流特性与三支柱绝缘子绝缘裕度分析  

Non-Uniform Gas Convection in UHV-GIL and Insulation Margin Analysis for Tri-Post Insulator

作　　者：杜伯学 董佳楠 梁虎成 Du Boxue;Dong Jia′nan;Liang Hucheng(Key Laboratory of Smart Grid of Education Ministry School of Electrical and Information Engineering Tianjin University,Tianjin 300072,China)

机构地区：[1]智能电网教育部重点实验室、天津大学电气自动化与信息工程学院,天津300072

出　　处：《电工技术学报》2023年第6期1678-1686,共9页Transactions of China Electrotechnical Society

基　　金：国家自然科学基金(U1966203);博士后创新人才支持计划(BX2021210)资助项目。

摘　　要：特高压(UHV)气体绝缘输电管道(GIL)导体通流发热,使绝缘气体SF6在温度梯度场下形成对流,导致三支柱绝缘子的沿面绝缘裕度与设计产生差异,威胁特高压GIL的安全运行。为探究气体对流效应对特高压GIL三支柱绝缘子沿面绝缘性能的影响,该文建立了水平敷设的1100kV GIL三支柱绝缘子电场-温度场-流体耦合仿真模型,考虑电场和气体密度的影响,计算了三支柱绝缘子放电起始电压。结果表明:大负荷条件下(8000A)GIL导体温度升高53℃,周围气体密度和介电强度下降15%,电场强度设计基准需同比例降低15%以保证足够的绝缘裕度;负荷导致放电起始电压降低11.6%,由于气体受热上浮,绝缘子上支柱周围的气体密度和介电强度均低于底部区域,更容易发生气体放电。因此,气体对流效应对特高压GIL绝缘性能的影响不能忽略,需要针对运行工况对结构及参数作进一步优化。In recent years,gas insulated transmission lines(GILs)have been widely applied in power systems because of their excellent performances including high transmission capacity,low power loss,strong environmental adaptability,etc.Under the current carrying condition,the joule heat generated from the central conductor can raise the conductor temperature to 70~80℃,causing a radial temperature gradient between the conductor and the shell.Under temperature gradient,SF6 gas convection is formed,changing the designed insulation margin of tri-post insulators,which threats the safe operation of UHV-GIL.At present,more attention is paid to the problem of electric field distribution during checking the insulation performance of UHV-GIL,and the influence of thermal-fluid field distribution on gas dielectric strength is seldom considered.Therefore,this paper analyzed the insulation margin of the UHV-GIL tri-post insulator considering the non-uniform gas convection effect.The simulation model of the electric-thermal-fluid field in a horizontally laid 1100kV GIL was established to explore the effects of the temperature and the gas density distributions inside the GIL on the breakdown strength of the insulation gas.Then,the insulation margin analysis for the tri-post insulator was conducted based on the current reference values of the designed electric field considering the gas convection effect.Finally,the discharge inception voltage based on the volume-time theory was calculated considering the electric field and the gas density.Results show that under the large current-carrying condition(8000A),the GIL conductor temperature reaches 78.1°C,reducing the local gas density and the dielectric strength by 15%.To keep the insulation margin,the reference value of the designed electric field should be lowered accordingly.The revised allowable electric field strength considering the gas convection is 20.4 kV/mm in the SF6 gap,is 10.2 kV/mm on the insulator surface and is 3 kV/mm inside the insulator and on the insert surface,respective

关 键 词：特高压GIL 气体对流 三支柱绝缘子 绝缘裕度 起始电压 

分 类 号：TM216[一般工业技术—材料科学与工程]