Phase-resolved measurement of partial discharge in artificially-simulated tree channel

Phase-resolved measurement of partial discharge (PD) in an artificially-simulated tree channel with diameter of 10-50 μm in low-density polyethylene was carried out. The results revealed that 50-μm channel showed the φ-q-n patterns similar to those from void PD, but the channels with diameters of 40 μm, 30 μm, 20 μm and 10 μm showed φ-q-n patterns similar to those from electrical treeing. Here φ is phase angle, q is PD magnitude and n is PD number. PD pulse-sequence analysis revealed that the PD number per half cycle decreased with the decrease of the channel diameter. In the channel with diameter of 10-μm, at most 1 PD occurred in every half cycle. PD pulses occurred in several consecutive cycles, then ceased for several consecutive cycles and then appeared again. It is probable that the trapped charge on the wall of the channel caused by a PD prevents another PD to occur in the same half cycle, but may assist a PD to occur in the following half cycle. These results are useful for explaining electrical treeing PD