Optical investigations of the recovery phase for impulse breakdown on the submicrosecond time range

An optical investigation of the recovery phase of SF₆ and the SF₆-N₂ gas mixture in the submicrosecond time range is presented. One aim of the investigations was the evaluation of the maximum repetition rate which can be realized using a spark gap as a closing switch. A high-voltage pulse generator was used, which delivers multiple square wave pulses with a constant time interval to allow recovery. For the analysis of the recovery phase, a high-speed photographic system was used, providing framing with a high spatial resolution. It is shown that, for the parameters considered, a recovery phase of 400 ns after a duration of current flow from 20 ns to 380 ns is not sufficient for reaching the original dielectric strength