Surface Charge Accumulation and Electric Field Distribution of Cone-Type Spacer in DC GIL

The surface charge accumulation on the spacer and the distortion of the surface electric field caused by it are the main reasons for the reduction of flashover voltage of DC GIL (Gas Insulated Transmission Line) spacers. A reasonable spacer structure helps to improve the surface electric field distribution. This paper considers the generation, migration, diffusion and recombination of free ions in GIL gas, and the nonlinear relationship between gas current density and electric field strength. A numerical model for the charge transport and accumulation in DC GIL is established. Based on this model, the surface charge accumulation and electric field distortion characteristics of cone-type spacer with different inclination angles and curvatures of the surface are investigated. The results show that the polarity of the accumulated charge on the two sides of the cone-type spacer is different from that on the inside and outside (concave and convex surface). The negative charge density in the concave surface is 1.6 times that of the positive charge density in the convex. The normal component of the electric field is the main reason for the formation of charge accumulation; The surface charge density of the cone-type spacer increases as its inclination angle increases. and there is a key position for the electric field along the both surfaces. The high-voltage side electric field decreases with the increase of the angle, and the electric field near the ground side increases with the increase of the angle; The smaller the curvature along the spacer, the higher the charge density. The research results can provide reference for structural optimization of cone-type spacer in DC GIL.