Coating effect on AC and impulse breakdown stress of SF/sub 6/

Under a uniform electric field and high (0.3 MPa) gas pressure, sulfur hexafluoride (SF/sub 6/) gas insulation breakdown strength was measured. When the coating is so thick that the electrical stress concentration caused by surface roughness is almost negligible, the breakdown stress for AC and impulse voltage is respectively 30/spl sim/88% and 18/spl sim/40% higher than that with bare electrodes. Breakdown stress dependence on the coating thickness and the electrode materials is discussed.