极寒环境下电缆GIS终端界面故障分析

Fault Analysis of Cable GIS Terminal Interface Under Extremely Cold Environment

气体绝缘(gas insulated switchgear,GIS)电缆终端广泛地应用于高压电缆系统中,近年冬季出现了多起因低温引发的故障,绝缘界面是导致极寒环境下电缆GIS终端发生故障的主要原因之一。该文基于电缆GIS终端内部两种界面的故障,针对环氧套管/橡胶界面,制作GIS环氧套管试样并开展了–40℃的机械性能试验,利用有限元分析计算了环氧套管的应力场;针对橡胶/交联聚乙烯界面故障,制作界面模拟试样并开展了不同温度和粗糙度条件下的击穿试验。结果表明:环氧套管在温度骤降时,其金属嵌件螺母处的内应力会增大,甚至超过其抗弯强度,硅橡胶的收缩会使环氧套管/橡胶界面出现气隙,可能引发套管的击穿;低温下的温度循环是导致极寒环境下GIS电缆终端橡胶/交联聚乙烯界面破坏的主要原因之一。分析结果可为极寒地区的GIS电缆终端结构设计和运维提供参考依据。

Gas insulated switchgear(GIS)cable terminal is widely used in high-voltage cable system.In recent years,many failures caused by low temperature have occurred in cable terminals in winter,and the insulation interface is one of the main reasons for the failure of cable GIS terminals in extremely cold environments.This paper is based on the faults of two interfaces inside the cable GIS terminal.The GIS epoxy casing simulation sample was prepared for the epoxy bushing/rubber interface,and the mechanical properties test and stress field finite element analysis were carried out at–40℃.In view of the failure of rubber/XLPE interface,the interface sample was prepared and the breakdown test was carried out under different temperature and roughness conditions.The results show that when the temperature of epoxy casing drops suddenly,the internal stress at the metal insert nut will increase or even exceed its bending strength.The shrinkage of silicone rubber will cause an air gap at the epoxy casing/rubber interface,which may lead to the breakdown of the casing.Temperature cycling at low temperatures is one of the main reasons for the failure of rubber/XLPE interface at GIS cable terminal in extremely cold environments.The analysis results in this paper can provide a basis for GIS cable terminal design and maintenance in extremely cold areas.