Effect of surface polishing on surface charging and flashover characteristics of spacer in GIS / GIL under AC condition

Surface discharge is easy to occur in the polishing area of the basin spacer surface under AC working condition, which significantly reduces the insulation performance of the spacer. The influence of the polishing method on the surface charging and flashover voltage of spacers under AC voltage is investigated by experiments. The basin spacer was polished radially and circumferentially, the surface charging of spacer under the AC voltage was analyzed, and the flashover voltage under different AC conditions was measured. Results show that the accumulation of positive charges in the polished area of the radially polished spacer. The surface charge distribution changes from a single negative charge uniform distribution to uneven distribution. Besides, the flashover voltage is affected by polishing method. The flashover voltage of spacer before and after radial polishing decreases by 14% under AC pre-voltage. The flashover voltage of the basin spacer is improved by overall radial and circumferential surface polishing. It is confirmed that the Al2O3 particles exposed in the polished area are the important reason for the difference in surface charge distribution and flashover voltage of spacer before and after polishing.