Statistical analysis of partial discharge phenomena. Time of occurrence distributions

This paper presents time-of-occurrence (phase) distributions of individual pulsating partial discharges (PDs) which occur in a point-dielectric gap in air for ac voltage conditions. It is determined that the pulse phase distribution is adequately modeled by a normal (Gaussian) distribution. Based on such best-fit normal distributions, estimated mean values of the phase and the standard deviations are given for the individual PD pulse distributions. For the alternating voltage case, the spread of time-of-occurrence distributions of succeeding pulses are universally broader than that of preceding pulses. PD pulse separations are non-uniform in phase. Further, if one assumes the usual sinusoidal waveform, then the voltage separation of PD pulses are also seen to be non-uniform