Corresponding Relation Between Aging Micrographs and Partial Discharge Properties of Electrical Trees in Silicone Rubber

At present, partial discharge(PD) test is one of the most available methods to detect the insulation status, but its theoretical foundation for evaluating the electrical treeing states in silicone rubber, which is used as the cable accessories' insulation material, is far from complete. Thus, we synchronously captured the optical images and partial discharge properties of the electrical trees in silicone rubber in treeing experiment. The n-q-φ(the frequency-phase-capacity of PDs) patterns reveal that the discharges are randomly dispersed in a wide phase range. The PD properties and the characteristics of the micrographs indicate that the PD counting per cycle increases with the electrical tree fractal dimensions during the tree propagation. When the maximum PD quantities increase, the electrical trees in the silicone rubber appear to have more bush-like and pine-like patterns. For the first time, the phenomenological properties and the PD sequence patterns are put together to discuss their relationship. It is found that large discharge pulse corresponds to rapid elongation of electrical branch channel, and the number of larger discharge pulses in positive half-cycle corresponds to the number of main channels when there is an obvious arterial channel. The comprehensive analysis of phenomenological properties, impulse sequence properties and partial PD signals offers a theoretical basis for using PD tests to evaluate the electrical treeing aging status in cable accessories.