Lightning Impulse Long Delay Breakdown of Centimeter Vacuum Gaps

This paper presents an experimental investigation into the breakdown voltage fall time tf of lightning voltage breakdown of 2-4 centimeter vacuum gaps having a long breakdown delay time td(>30 μs). The results show that the average 50% breakdown voltage fall time t50 decreases with increasing vacuum gap. It is considered that the lightning impulse breakdown of the centimeter vacuum gaps with a long breakdown delay time may be initiated by the interaction between the cathode thermal processes and the micro-particles phenomena. The increase of the electrode diameter and the decrease of the electrode radius of curvature may contribute to the decrease of the breakdown voltage fall time.