Partial discharge characteristics and tree propagation in artificially-simulated tree channel

In an attempt to clarify the mechanism of electrical treeing degradation and tree propagation, partial discharge (PD) characteristics in an artificially-simulated tree channel in a low-density polyethylene (LDPE) sample were investigated. The PD's formed PD pulse trains whose magnitude changed with time. In the samples where tree propagation was seen at the tip of the artificial channel, pulse trains with large PD magnitude sometimes occurred and the region of light emission reached the vicinity of the channel tip before tree propagation. In the samples where tree propagation was not seen, the region of light emission due to PD did not reach the channel tip. These results suggest that tree propagation takes place when PD's with large magnitude and long luminous region occur in an artificial channel and damage the channel tip.