EFFECT OF OVERVOLTAGE ON THE RISETIME AND AMPLITUDE OF PD PULSES

A two-dimensional mathematical model has been employed to characterize the pulse or spark breakdown behavior of a short gap in air. It has b een established that the form or shape of a breakdown current pulse is very much determined by the overvoltage developed across the gap. Lar ge overvoltages lead to intense space charge effects, which appreciabl y modify the breakdown current pulse form, leading to more rapid rise times, greater peak current amplitudes and reduced pulse widths. In so far as the overvoltage across a given cavity affects the rise time an d amplitude of the pulse resulting from a spark type discharge, the re sponse of a conventional partial discharge pulse detector is necessari ly a function of the overvoltage developed across the cavity.