Impulse breakdown of short rod-plane gaps and the influence of humidity

An attempt is made to assess the extent of influence of various parameters on the breakdown mechanism in short rod-plane gaps under positive impulses. Such parameters include front duration and peak value of the impulse voltage, gap length, profile of the rod and, in particular, absolute humidity. Depending on the above parameters, breakdown occurs either through a streamer-dominated breakdown mechanism or through one involving the development of a small leader. The second corona was found to predesignate which mechanism will take place, thus influencing the statistical behaviour of breakdown, Calculated humidity correction factors were found to be different from those proposed by IEC