Effect of temperatures on very low frequency partial discharge diagnostics

Effects of temperatures on corona discharges developed by needle/bowl electrode configuration at very low frequency are investigated. Partial discharge measurements are carried out under enclosed controlled air temperature range between 20°C and 40°C. Sinusoidal voltage waveform is applied to the test sample under very low frequency and power frequency. Experiment results show that electrical discharge behaviours at 0.1 Hz and power frequency are dependent on ambient temperature in a similar manner. Nevertheless, there are still noticeable differences in partial discharge characteristics at very low frequency at various temperatures, especially in the phase position of discharge events. This could be explained from more availability of free electrons emitted from the negative electrode under higher temperature. Experiment results suggest that, under very low frequency excitation, there might be a critical temperature that triggers change in PD behaviour at a certain applied voltage level.