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Prediction of tree initiation by phase angle analysis of discharge magnitude and discharge luminescence on partial discharge

Partial discharge is one of the causes of degradation in insulating polymer materials subjected to high voltages. Of particular importance in this case is the degradation which occurs due to partial discharges inside gaps, such as voids inside an insulator. In this study, the prediction of tree initiation due to partial discharge occurring from void is considered. New tree initiation diagnostic methods are proposed by measuring discharge magnitude and discharge luminescence in each phase angle section of the applied voltage. It was noted that some samples revealed different time dependence of partial discharge patterns even under the same measurement condition. These patterns were the case of the occurrence of Swarming Pulsive Micro Discharges before tree initiation. The prediction of tree initiation is analyzed by using moving average of the discharge magnitude. A proposal of the typical variances seen in the time dependence of partial discharge which symbolize a pre-tree initiation mode will be made as well as evaluation of the usefulness of this technique.