Partial discharge characteristics and tree inception in artificial simulated tree channels

In 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) were investigated. The PD pattern and PD pulse sequence showed that the PD in artificial channel with diameter of 10 /spl mu/m was useful for clarification of PD in actual tree. The PD formed a PD pulse train 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 the PD with large magnitude and long luminous region occur in an artificial channel and damage the channel tip.