Initiation and Propagation Processes of Electrical Tree in Silicone Rubber

Cross-linked polyethylene power cables are more and more widely used, but they still have electrical tree break-down happened in cable accessories occasionally, while the mechanism of electrical treeing's initiation and propagation needs further research. Therefore, through material and calculative analyses, we described the microscopic structure of silicone rubber quantitatively, and obtained the channel characteristics and partial discharge characteristics during the initiation stage of electrical treeing. It is shown that the microscopic structure of silicone rubber includes a large number of physical crosslinking comprising the crosslinking in silicone rubber together with chemical crosslinking; The breakdown of physical crosslinking structure makes microscopic crack zones become larger, which further causes the electrical tree initiation. Meanwhile, channels of electrical trees have good insulation properties, and the trees' growth depends on the tearing effect of gas heat expansion or electromagnetic force under strong partial discharge mainly. Improving the mechanical properties, especially improving the tear characteristics, can enhance the silicone rubber's ability against electrical trees. The research on the initiation and propagation of electrical trees in silicon rubber provides theoretical basis for the proper application of silicone rubber in cable accessories.