Study on the characteristics of partial discharges in voids under square voltage by detecting light emission intensity

In order to quantitatively study partial discharge (PD) behavior in voids under square voltage, the feasibility of PD measurement by detection of light emission intensity was investigated at first. Experiments were carried out to study the influences of void size on the correlation between light emission intensity and PD magnitude and its transition with PD degradation. It is confirmed that a good correlation existed between light emission intensity and PD magnitude in a void with diameter larger than 3mm and the correlation did not change in the PD degradation process. Then, the effect of square voltage rise rate on PD characteristics under square voltage was investigated by detecting light emission intensity. In the PD degradation process, an abnormal phenomenon that the maximum PD magnitude decreased with the increase of voltage rise rate was observed. This was interpreted in terms of the change of surface condition due to PD degradation.