Effects of low temperature and nanoparticles on electrical trees in RTV silicone rubber

The operating temperature of power cable system has a great influence on the electrical performance of room temperature vulcanizing (RTV) silicone rubber. This paper investigated the effects of low temperature and nanoparticles on electrical tree in RTV silicone rubber. Samples were prepared by mixing SiO₂ nanoparticles into RTV silicone rubber, with the content of 0, 0.5, 1, 1.5 and 2 wt% respectively. The experiment temperature was ranged from - 30 to -90 °C. AC voltage with a frequency of 50 Hz was applied between a needle-plate electrode. The electrical tree patterns, growth rate, expansion coefficient, fractal dimension and proportion of accumulated damage were studied. The results reveal that both nanoparticles and low temperature environment have a significant impact on the electrical tree growth. The tree patterns are branch tree or bush tree when the temperature is higher than -60 °C; however, there is only pine tree when the temperature is lower than -90 °C. Compared with - 30 °C, some tree channels are easier to propagate at - 60 °C in silicone rubber. It is also suggested that the temperature affects the expansion coefficient of electrical tree. The fractal dimension of the electrical tree increases with the nanoparticle content, while the accumulated damage of treeing area shows the opposite tendency.