Metal particle encouraged surface charge accumulation on epoxy insulator with multi-arc surface profile under DC voltage

Abstract

Surface charge accumulation on epoxy insulator installed in gas insulated switchgear (GIS) or gas insulated transmission line (GIL) has been recognized as an important factor for electric field distortion that results in reduction of surface flashover voltage. This paper reports on surface charge accumulation behavior on a actual epoxy insulator for 100 kV GIL prototype with multi-arc surface profile. A coaxial electrode system is used to investigate the charging behavior under DC voltages with metal particles positioned at various positions of the surface so as to estimate its influence on the charge accumulation behavior using a Kelvin type probe. The results show that positive charges are accumulated mainly on the nonplanar region around the high voltage electrode in the shape of speckles, and the average charge distribution along the radial direction presented a double-peak feature. Moreover, the charge accumulation is enhanced by metal particles contacting to the grounded electrode. Using a numerical simulation method, it is suggested that the charge accumulation is mainly determined by gaseous ionization which is enhanced by the metal particle induced electric field distortion.