Charging and Breakdown Characteristics of Various Surface-Treatment Spacers Under DC Voltage in SF6

Recent progress in DC transmission projects has promoted of DC gas insulated switchgear (DC GIS) to ensure better reliability, compactness and economy.1, 2 One difficulty with DC GIS is charge accumulation on solid insulating spacers under DC stress. A number of studies have looked at the effects of the charge accumulation,3, 4 but little has been done on countermeasures for accumulated charge. In this study, we investigated the effects of surface-treatment conditions of spacers treatments included use of a low permittivity material coating, an anti-charging material coating, and a metal-sputtering coating. A final condition was use of coated electrodes with a non-coated spacer. The test results are described along with our evaluation of the spacer for DC GIS.