Effect of low temperature on tree characteristics in silicone rubber under repetitive pulse voltage

Silicone rubber (SiR) has been an important material in cable accessories which are connected to the superconducting power system. Electrical tree is a serious electrical aging to SiR insulation and it will cause breakdown when reaches the ground. Addition of nanoparticles into SiR will improve the insulating properties compared with undoped material. However, the effect of temperature below 0 °C under repetitive pulse voltage has not been researched. In this paper, the samples were prepared by mixing nano-SiO₂ into liquid SiR, with the content of 0, 0.5, 1.0, 1.5 and 2.0 wt% respectively. The experiment temperature was set to be -30, -60 and -90 °C. Repetitive pulse voltage was applied between the needle-plate electrodes for the initiation and growth of electrical tree. The growth process of electrical trees was recorded by a microscope system and the pictures were taken. The experiment results indicated that both nanoparticles and low temperature are important factors of the treeing process in SiR/SiO₂ nanocomposites.