A comment concerning the rise times of partial discharge pulses

The influence of the discharge mechanism upon the rise time of partial discharge pulses is examined. In contrast to the long rise times characterizing the discharge pulses generated by glow discharges, spark discharges exhibit typically short rise times and large magnitude pulses. The occurrence of the latter is favoured by cavities wherein there is a paucity of free electrons that are necessary for electron avalanche formation. As a consequence, breakdowns across these cavities occur under overvoltage conditions, thus leading to space charge formation and photoemission at the cathode; this results in a rapid development of constricted spark-type breakdown channels. The question of detectability of short and long rise time pulses, utilizing PD detectors having different bandwidths, is considered both in the proximity to, as well as far removed from, the discharge sites.