Dielectric and Mechanical Properties of Silicone Rubber for Cable Termination at Low Temperature

Recently, there have been many accidents in GIS dry cable terminals, which are closely related to the low-temperature extreme weather (as low as −30 °c). Silicone rubber is an essential material of the terminal stress cone, and its mechanical and dielectric properties will directly affect the insulation strength at the interface. In this paper, the dielectric and mechanical properties of silicone rubber at low temperature are investigated and the causes of cable termination failures are analyzed based on electric field simulation. The results show that, under low temperature, the tensile strength and hardness of the silicone rubber will increase, which will reduce the interface bonding performance and generate micro air gaps. In addition, the relative dielectric constant increases from 3.08 at 20 °C to 3.48 at −40 °c, the increase rate can reach 12.98%. The simulation results further show that low temperature will aggravate the interface air gap electric field, and the maximum distortion field strength is 3.26 kV/mm, which increases by 22.6% compared to 20 °C, eventually bringing the risk to the cable terminal operation.