Effect of Zoning-Coating on Charge Suppression on Asymmetric Surface of DC GIS Insulator

This paper discusses the suppression effect of zoning-coating on the charge accumulation on the asymmetric surfaces of insulator in DC gas-insulated switchgear (GIS). Down-sized insulator with concave and convex surfaces was chosen as the test sample. Zoning-coating, depositing coatings with various conductivities in a partition, was applied on both surfaces of the test sample. The samples of uncoated and coated insulator were charged with +5, +15 and +25 kV DC testing voltage until the surface charge reached a steady state, and the charge densities on the asymmetric surfaces were recorded. The results displayed that the charge densities increased with the testing voltage, and the accumulation on the concave surface was more serious than that on the convex surface. Compared with the uncoated insulator, the accumulation on the zoningcoating insulator was suppressed. The maximum charge density on the concave and convex surfaces of coated insulators decreased by 34.21% and 16.22% under +25 kV. It is considered that the zoning-coating is effective in suppressing charge accumulation on the DC GIS insulator, and the suppression effect is more pronounced on the concave surface.