Electrical Tree in Silicone Rubber under Voltage Combined of DC and Pulse

Silicone rubber (SiR) is widely used in high voltage DC (HVDC) cable accessories due to its excellent electrical and mechanical properties. The growth of electrical tree is the physical process of the microstructure of the insulation, which is very harmful to the insulation performance of high voltage cable accessories. The electrical tree under AC and DC voltage has been widely researched. While there are pulses in the HVDC cables under operating conditions, which is caused by the lighting and operating impulse in the power system. However, there are only few researches on the effect of the combined DC-pulse voltage on electrical tree, and its inception and growth mechanism is still not clear. In this paper, electrical trees have been generated under combined DC-pulse voltage. The treeing process were recorded by a digital microscope system. It is found that the distribution of tree structure is determined by the amplitude of combined DC-pulse voltage. The tree growth characteristics are also influenced by the combined voltage.