Effect of temperature on electrical tree in silicone rubber

In this paper, room temperature vulcanized (RTV) silicone rubber (SiR) was employed as test sample to investigate the relationship between electrical tree propagation characteristics and the experiment temperature. Both the structures and growth characteristics of electrical tree in SiR were observed by using a digital camera and a microscope system. Obtained results show that electrical tree in RTV SiR is white gap tree channel, which all initiate from single branch, and the width of initiative single branch channel varies a lot with the electrical tree structure. The structure of electrical tree at experiment temperature from 30°C to 90°C in RTV SiR can be classified into four categories. They are branch, bush, pine branch and bush-pine mixed tree. The distribution of tree structures changes with the experiment. At the temperature of 30°C, branch tree take up a great proportion, however, bush tree becomes the dominant structure when the temperature rise up to 60°C and 90°C. The probability of tree initiation decreases obviously with the rise of the experiment temperature from 30°C to 90°C. All kinds of electrical tree grow rapidly in the first beginning of the treeing propagation, and this process lasts only a few minutes. In addition, a new parameter, the treeing proportion is introduced to describe propagation characteristics of bush tree.