Voltage-time characteristics of PD patterns in void discharges

PD in defects of solid insulation system is very harmful since it leads to deterioration of insulation. But, PD can indicate incipient failure, so it has been used to determine degradation of insulation. Void is usual defect in solid insulation system. Void is very harmful since it leads to deterioration of insulation. So it is very important that study properties of PD in void. To estimate deterioration of void, accurate and general characteristics of PD in void are required. The correlation between size of void and internal partial discharge (PD) was discussed as a function of time of the applied voltage and its magnitude. Magnitude, repetition rate, average discharge power and Average discharge current of PD in specimens with large void were larger than the other. The smaller specimens had void, the faster magnitude and the number of PD were reduced.