Electrical Tree Characteristics in Silicone Rubber under Repetitive Pulse Voltage

Electrical tree in silicone rubber (SiR) is a threat to the power system. Bedsides ac and dc voltage, there are pulse voltage in power system and the electrical tree behavior in SiR under pulse voltage has not been reported. In this paper, electrical treeing process in SiR under pulse voltage was investigated and analyzed. The voltage was applied to a needle-plate electrode to initiate electrical trees. The frequency of pulse voltage was 100, 200 and 300 Hz and the amplitude ranges from 8 to 14 kV. Aspects such as the patterns of electrical tree, tree length, accumulated damage, fractal dimension and tree breakdown characteristics were studied. Results indicate that the pulse amplitude plays the leading role in electrical tree initiation, propagation and breakdown processes. With the increase of pulse amplitude, the tree structure changes and the breakdown possibility increases obviously. However, the tree length is not sensitive to pulse frequency and higher pulse frequency promotes the increase of tree density. It also has been found that tree structure is closely related to pulse polarity and the inception voltage is lower with positive pulse than that with negative.