Flashover Characteristics of Epoxy Insulator in SF6/CF4 Gas Mixture at Low Temperature

Extremely cold weather may damage the internal insulation performance of gas insulated electrical equipment, resulting in threats to the reliability of the equipment. The surface flashover characteristics of insulator in SF
6
/CF
4
gas mixture at low temperature are obtained. The results show that when temperature decreases from 20°C to -50°C, the flashover voltage first decreases, then increases, and finally decreases. Compared with the experimental results in SF
6
, gas, it is found that the variation trend of flashover voltage is similar, but the variation degree in the SF
6
/CF
4
mixed gas is less than that in SF
6
gas. The flashover voltage in 0.7MPa 50%SF
6
/50%CF
4
is slightly lower than that in 0.5MPa SF
6
, and the gap becomes larger as temperature decreases. When temperature is higher than -35°C, using 0.5MPa pure SF
6
gas or 0.7MPa 50%SF
6
/50%CF
4
gas mixture can both ensure that the surface insulation performance does not decrease significantly at lower temperature compared with that at 20 °C. However, the surface flashover voltage in 0.7MPa 50%SF
6
/50%CF
4
gas mixture at -50°C is about 30% lower than that at 20°C, indicating that the SF
6
content in the gas mixture should be reduced at -50°C.