In-Vacuum Surface Flashover Characteristics of Insulator With Different Oil Coating Regions

The surface flashover usually occurs on the interface between the insulator and vacuum in a pulsed power system and high-voltage device. In this paper, we studied the improvement of insulator performance in vacuum by covering the transformer oil on different insulator surface regions. We calculated the electrical field distribution to evaluate the influence of oil coating and carried out the surface flashover experiments by oil coating on different regions. The calculated results of the electric field showed that the electrical field magnitude was reduced by coating oil layer and the maximum field located at the electrode triple junction of metal, oil, and insulator. The experiment results showed that the insulator performances with a coating on cathode or anode region were lower than that with the whole surface coating but still higher than that with no coating. Then, the flashover process with a coating on different regions was also discussed. We speculated that the oil layer could restrict the development of secondary electrons and the release of desorbed gas, so the insulator performance could be increased by coating the oil layer on the entire surface, cathode region, and anode region. The insulator performance with cathode region coating and anode region coating was lower than that with entire surface coating due to the electrons avalanche easily moving from cathode to anode.