Influence of electrode contacts on flashover characteristics of alumina and PTFE under pulsed voltage in vacuum

The surface flashover phenomena across insulating materials always lead to the failure of system insulation and may cause serious accidents. Based on the synchronized measurement of optical and electrical signals, the flashover phenomena along alumina ceramics and polytetrafluoroethylene (PTFE) are investigated under impulse voltage in vacuum. The planar electrode system is used with the advantage of optical observation. Different electrode contact manners are employed, i.e., with the traditional electrode butt contact and with the sputtered metal films for adjusting the contact behavior. The fundamental characteristics of flashover phenomena are discussed, and the difference of the flashover characteristics between alumina and PTFE is also compared. It is also revealed that sputtering metal film electrode has obvious influence on the flashover characteristics of insulator. Based on the band theory of solid, these phenomena can be reasonably explained by the charge carrier injection and transport behaviors.