Influence of Curvature Radius of Needle Tip on Characteristics of Electrical Treeing in Silicone Rubber

Studies on electrical treeing characteristics of silicone rubber (SIR) were carried out in this paper. Tree initiation voltage and electrical tree shape of different curvature radius of needle tip were measured. From the experiments, it was found that tree initiation voltage of SIR is so low that causes high failure rate of cable accessories. Electrical tree in SIR initiates mostly in a single branch named initiation tree, which will transfer to four kinds of electrical trees with different shapes. Electrical treeing characteristics were discussed by the model of tree shape propagation in silicone rubber. Meanwhile, initiation tree, withe-like tree and breakdown channel caused by withe-like tree mentioned here can be found in failed cable accessories. This indicates that the experimental results can be used as an explanation for the failure on site.