Influence of Creeping Distance and Gas Pressure on Negative Creeping Discharge for Composite Insulation Consisting of N₂/SF₆ and Solid Dielectric under Pulse Voltage

Abstract

Creeping discharge characteristics on negative polarity of a composite gas/solid insulating system with N2/SF6 mixed gas have been studied by inserting a solid insulator between a needle electrode and a plane electrode. In the case of the shorter creeping distance, the flashover voltage on the negative needle increased with increasing SF6 gas content, which was a positive effect of the SF6 gas mixture. When creeping distance was increased, a considerable decrease in the flashover voltage on the negative needle under the gas pressures P of 0.2 MPa and 0.3 MPa was observed by the addition of a small amount of SF6 into N2. The effect of SF6 gas mixture for the flashover voltage on the negative needle changed from positive to negative at a threshold creeping distance. Furthermore, the threshold creeping distance depended on the gas pressure.