Electrical tree characteristics of XLPE under repetitive pulse voltage in low temperature

Cross-linked polyethylene (XLPE) may be operated under repetitive pulse voltage and low temperature environment. In recent years, many influencing factors to the treeing process, which is a main reason for the aging of XLPE have been researched. However, the tree behavior under repetitive pulse voltage and low temperature in XLPE is still not clear. In this paper, the tree behavior under repetitive pulse voltage and low temperature was investigated and analyzed. A positive pulse voltage with the amplitude of 12 kV and the frequency of 300 and 400 Hz was applied on the needle-plate electrodes. The experimental temperature was set to 30, -30, -90 and -196 °C. Four typical morphologies of the electrical trees are observed, including bush, branch, branch-pine and stagnated tree. It is revealed that low temperature has an obvious effect on tree structures and it can reduce the tree growth rate and extend the time to breakdown. It is also revealed that the tree inception probability becomes lower with the decrease of temperature. With the increase of pulse frequency, the tree growth rate, the fractal dimension and the number of tree channels increases and the tree inception probability becomes higher, but the morphologies of electrical trees stay the same.