Measurement and analysis of partial discharge current during square voltage waveforms

Arbitrary Waveform Impedance Spectroscopy (AWIS) is used to measure the current generated by partial discharges in a twisted pair sample close to inception voltage. By subtracting the dielectric current resulting from the inherent complex capacitance of the insulating system from the total measured current, the additional current contribution from partial discharges can be obtained. The use of the AWIS system for partial discharge measurements provides integrated information of magnitude, phase position and changes of these properties during time. In addition a conductive current, believed to be related to transport of charge deposited by discharges, can be observed. For the twisted pair sample studied here, the frequency of discharge bursts during the intermittent stage seems to be related to the rate of conductive current decay. This indicates that the conductive current might be an important quantity of insulating systems operating close to partial discharge inception voltage.