126 kV GIS三工位隔离开关用绝缘拉杆击穿故障分析

Analysis on an Accident of Insulated Pull Rod in 126 kV GIS Disconnector With Three Positions

为了分析一起126 kV GIS三工位隔离开关用绝缘拉杆击穿故障原因,通过对绝缘拉杆进行外观检查、耐压及局放试验、X射线检测、解剖观察、电场仿真分析等试验,判定故障的主要原因为绝缘拉杆电场结构设计不合理。金属嵌件与真空浸胶管相交联的三界面场强位置未采取合适的电场屏蔽设计,导致三界面位置楔形气隙及附近气孔直接暴露在高场强下,产生局部放电,长期局放造成绝缘材料劣化,最终发生击穿故障。

An accident of insulated pull rod used in 126 kV GIS disconnector with three positions was studied by means of appearance inspection, high-voltage holding test, partial discharge test, X-ray detection, dissection research, and electric field simulation. The results show that the main cause of the accident is the unreasonable electric field structural design. Proper electric field shielding design was not adopted at the three-interface field strength position where the metal insert intersected with the vacuum impregnation tube, leading to wedge air gap and nearby pores at the three-interface positions directly exposed to high field strength. The partial discharge is generated. Long-term partial discharge causes deterioration of insulation material and finally the breakdown accident.