Effect of Surface Coating on Charge Accumulation Feature on Epoxy Insulator under DC Voltage

Epoxy insulator widely used in Gas Insulated Switchgear (GIS) and Gas Insulated transmission Line (GIL) is subjected to the risk of surface charge accumulation that leads to the electric field distortion and the reduction in flashover voltage thus threatening the insulation performance. From the viewpoint of safety, it is very necessary to control the charge accumulation on epoxy insulator surface. Over the years, the surface coating has been suggested a promising route for charge suppression especially with the installed epoxy insulator. In this work, a flexible coating protocol for a real size epoxy insulator is suggested with the help of numerical simulation. The effect of coating on charge suppression of epoxy insulator has been compared and discussed. The results suggested that the surface charge of insulator was mainly accumulated in nonplanar area. The shallow trap and deep trap in the coating were used to regulate the surface charge on insulator, a significant suppression was achieved.

I. Introduction

Epoxy resin has been widely used in Gas Insulated Switchgear (GIS) and Gas Insulated transmission Line (GIL) because of its excellent insulation and mechanical properties [1]. The insulation performance of epoxy resin is directly related to the safe and stable operation of the equipment. However, after long-time operation under DC voltage, free charges are accumulated on the surface of the insulator to form the surface charge, resulting in the distortion of electric field distribution and a significant reduction of flashover voltage, which will seriously affect the insulation performance [2]. From the point of safety, it is necessary to find an effective way to inhibit the surface charge accumulation.