Influence of residual charge on treeing degradation with single pulse analysis

Electrical treeing is one of the problems with insulating polymer materials. Therefore, much research has been carried out. The method of diagnosis for insulation degradation is not established yet. The purpose of this research is to improve the accuracy of degradation diagnosis by analyzing the relation between charge and luminescence. A needle-plane electrode was constituted in a PMMA (polymethyl-methacrylate) block, and a needle shape void was made at the tip of the needle electrode. The treeing experiments were conducted by applying ac high voltage to the needle electrode. The conditions of discharge change according to the phase angle area of ac voltage. In this paper, an investigation was carried out by corresponding to the amount of charges and luminescence, obtained from a single partial discharge in the treeing degradation. Results are as follows. A difference was observed in the amount of luminescence, and the luminescence length depended on the phase angle area also in the amount of charges of the same grade. The luminescence form changed with phase angle area also in the amount of charges of the same grade. It has been shown that the influence of the residual charge in a tree is the cause of these phenomena.