Nanosize Filler Effect on Propagation of Electron Avalanche in Terms of Waveform Characteristics of Partial Discharge

Nanocomposite materials have excellent insulating properties, such as improved treeing resistance. The propagation properties of electrical trees are often determined using optical observations and partial discharge (PD) characteristics regarding phase angle distribution patterns. There is a limit to confirming the effects of physical barriers on the PD by optical observation alone. Conversely, there is a high possibility that the PD waveform reflects the characteristics of the electron avalanche in the discharge space. In this study, we constructed a PD measurement system with the widest possible frequency range and acquired 1000 PD waveforms along the time series. Although the acquired waveforms have a single peak or multiple peaks, adding nanofillers increased the observation ratio of the waveform with multiple peaks. Furthermore, the multiple peaks suggested that the electron avalanche progresses with difficulty considering that the nanofillers easily capture electrons. We investigated the effect of adding nanofillers from the viewpoint of the waveform characteristics. The time difference between the peaks and the peak ratio is also supported by the property changes in the electron avalanche because of the electron capture by nanofillers.