Effects of frequency on treeing phenomena in Silicone rubber

The use of Silicone rubber (SiR) is increasing as an insulating material of cable joint in power transmission line in recent years for its various excellent characteristics. However, few attentions has been focused on the influence of frequency on electrical tree characteristics. In this paper, room temperature vulcanized silicone rubber was employed as test sample to investigate the relationship between electrical tree propagation characteristics and the frequency of applied voltage. Electrical trees have been grown over a frequency range from 50 Hz to 10 kHz through the typical needle-plate electrode, both the structures and growth characteristics of electrical tree were observed by using a digital camera and a microscope system. The fractal dimension of electrical tree is calculated using a simple box-counting technique. Obtained results show that both the tree structures and the accumulative probability of tree inception vary a lot with the increase of frequency. In detail, the frequency reduces the time to initiation, accelerates tree growth rate and reduces the time to breakdown.