Influence Of Surface Modification By Direct Fluorination On Dielectric Flashover Characteristics In Vacuum

The surface flashover phenomena of insulating materials in vacuum greatly weakens the overall performance of vacuum-dielectric system, which seriously limits its development. The improvement of surface flashover characteristics of insulators in vacuum becomes a significant challenge for the development of high voltage electrical equipment. In this paper, we report a simple and convenient way to achieve the high surface flashover performance of low density polyethylene (LDPE) and alumina ceramics (Al2O3) in vacuum based on direct fluorination technique. The direct fluorination of test samples was performed in a fluorination apparatus for different time of 30, 60, and 90min by using F-2/N-2 mixture of 12.5% F-2 with the pressure and temperature keeping constant as 0.1MPa and 55 degrees C. Then the surface flashover characteristics of LDPE and Al2O3 at different fluorination time was investigated. The results show that for LDPE samples fluorinated with 30 and 60min, the hold-off voltage increased by 21.9% and 34.1% than the virgin sample. However, the hold-on capability decreased apparently for the case of 90min fluorination. However for Al2O3 samples, direct fluorination had little influence on the surface flashover characteristics. This research could make a contribution to understand the influence of direct fluorination on dielectric flashover characteristics in vacuum.