Measurement of surface charge distribution on DC-GIS cone-type spacer in charge accumulation/decay process

Surface charge accumulation under high DC electric fields causes electric field distortion and flashover voltage reduction in DC gas-insulated switchgear (DC-GIS). Since most studies have investigated the charge accumulation phenomena with disk-type spacers, the phenomena with cone-type spacers are poorly understood. In this study, surface charge density distribution on a downsized cone-type spacer in DC-GIS simulated environment is obtained. Our measured results show that homocharges accumulate dominantly on both surfaces of cone-type spacers, which is the same as the results obtained with disk-type spacers. The experimental results agreed well with the simulated results of resistive field calculation around an inner electrode. We attributed the agreement to the fact that charge transport in the cone-type spacer is dominant by that through spacer bulk due to its cone-shaped structure. This study suggests the validity of the resistive field calculation for insulation designs of cone-type spacers.