Auto-correlation function of PD pulses under electrical treeing degradation

Pulse correlation in PD signals was analyzed with auto-correlation function of PD pulses occurring in tree channels at 50 Hz ac voltage application as well as PD pulses occurring in several simple model electrodes. It was clarified that the auto-correlation function of PD pulse trains was strongly affected by void shape including tree length. It was found that even simple model electrodes, which showed very similar /spl phi/-q distribution patterns to those of tree channels, had different auto-correlation functions from those of PD pulse trains of tree channels. The results suggest that the auto-correlation function may give additional information about the PD mechanism to that given by the /spl phi/-q distribution patterns.>