Flashover Characteristics along the Insulator in SF6 Gas under DC Voltage

In order to promote the flexibility about the selection of transmission corridor, DC gas-insulated transmission line (GIL) can be utilized to substitute part of the overhead line. One of the key factors that greatly threaten insulation level of GIL is the accumulation of surface charges along the supporting insulators under DC voltage. In this paper, the sphere-plane electrode system has been established to simulate the field distribution of the coaxial cylinder configuration in GIL. The effect of the insulator´s material and geometry on the insulator´s flashover characteristics under DC voltage in SF₆ gas has been investigated. Results show that the insulator´s surface conductivity has great influence on the surface charge accumulation as well as the flashover along the insulator in DC GIL.