Influence of Metal Particle Contamination on Surface Charging and Flashover Characteristics of PTFE Insulator under Impulse Voltage in Vacuum

Influence of metal particle contamination on surface charging behaviors as well as flashover characteristics for PTFE insulators in vacuum was experimentally investigated under impulse voltage under a planar electrode-sample structure. The surface charge was measured by a vibrating Kelvin probe used in conjunction with an electrostatic voltmeter. The effects of metal particle positioned on insulator, e.g., near cathode, at the middle of cathode-anode surface and near anode, on surface charging and flashover voltage were discussed. It is confirmed that the secondary electron emission process governs surface charge accumulation behaviors under impulse excitation, which initiates from cathode triple junction (CTJ) and develops towards anode. Surface charging is much more severe with metal particle contamination, and flashover voltage decreases as the size of metal particle increases due to the enhanced electric field at CTJ. This study is helpful to make a better understanding of the mechanism of surface flashover for insulators with metal particle contamination.