Influence of tiny metal particles on charge accumulation phenomena of GIS model spacer in high-pressure SF6 gas

The charge density distribution of the downsized GIS disc spacer made of epoxy resin was measured in 0.5-MPa (abs.) SF₆ gas. A dc voltage was applied to the spacer, and the charge density on the surface was measured using an electrostatic probe. Voltage application and charge measurement were conducted in a sealed chamber without opening it. After the voltage application of 60 kV, radial charge patterns appeared on the spacer. Tiny metal particles whose size is smaller than 0.1 mm were observed on the spacer after the voltage application. Metal particles on the spacer may cause the radial charge accumulation in this experiment: if a metal particle adheres on the spacer, partial discharge may occur near the metal particles and negative charges may progress along the surface of the spacer.