Effect of Low Temperature on Impulse Discharge Characteristics of Insulator String

Due to the geographical location, many transmission lines operate in cold conditions for a long period of the year. However, the existing standards are mostly only applicable for the correction of the discharge voltage of the external insulation above 5 ℃. The relevant basic data under low temperature are lacking and there is no targeted optimization and improvement for the external insulation. In this paper, switching impulse discharge and lightning impulse discharge tests on insulator strings using XWP-70 insulator are carried out at normal temperature and low temperature respectively. The results show that the switching impulse discharge voltage of insulator string is lower than that of lightning impulse discharge. With the decrease of temperature, both the witching impulse discharge voltage and the lightning impulse discharge voltage increase, and the increase of lightning impulse discharge voltage is greater than that of witching impulse. It indicates that the external insulation configuration at low temperatures can be optimized. The research results can provide theoretical support for the design and optimization of external insulation of transmission lines under perennial low temperature environment. It has important reference value for ensuring the safe operation of power grid, improving the stability of electrical equipment and reducing operation and maintenance costs in extremely cold areas.