Ultrahigh frequency study of PD pulses

Conventional partial discharge (PD) measurements are carried out with instruments of relatively limited bandwidth. There arises the question as to the temporal characteristics of the actual pulses and the significance of the results so obtained. To gain a detailed knowledge of the rise time, duration and amplitude of these pulses, a study has been undertaken using as detector a 500 MHz digitizing oscilloscope in combination with a point-plane electrode geometry. In this paper the pulse characteristics of PD in air were studied as a function of polarity under dc and ac conditions