Effect of Coating Conductivity on Surface Charge Accumulation with Metal Particle on DC Conical Insulator

This paper focuses on the surface charge accumulation on conical insulators in DC gas-insulated switchgear (GIS). Down-sized insulators applied with high-, low- and nonlinear-conductivity coatings were selected as test samples with a metal particle attached to the central conductor. After being charged by ±15 kV DC voltage for 1 hour, the charge distributions on the concave and convex surfaces of the insulator were displayed. The results showed that the effect of coating conductivity on surface charge accumulation was related to the polarity of applied voltage and surface characteristics of the insulator. A charge spot appeared near the metal particle, on the convex surface, a hetero-charge spot tended to be formed while on the convex surface, the polarity of the charge spot was reversed.