Surface Charge Accumulation on a Real Size Epoxy Spacer in Various Gas Atmospheres under DC Voltage

Abstract

Surface charge accumulation on the epoxy spacer installed in gas insulated transmission line (GIL) and gas insulated switchgear (GIS) has been recognized as a crucial factor for electric field distortion that results in reduction of surface flashover voltage. This paper reports on the surface charge accumulation on a real size epoxy spacer in various gas atmospheres. A coaxial electrode system was designed to investigate the surface charge density on the spacer under DC voltage of −10 and −30 kV. The spacer and electrode were placed in a metal enclosed test chamber which was filled with 0.1 MPa air, 0.4 MPa SF6/N2 mixture or in vacuum so as to estimate the influence of gas atmosphere on the charge accumulation behavior. The results indicated that positive charges were accumulated on the nonplanar region in air, whereas negative charges were mainly accumulated on the nonplanar region in SF6/N2 mixture and vacuum. It is considered that the charge accumulation behavior is determined by the competition result among the bulk, the gas and the surface conductions.