Research on the Energized Ice-Melting for the Ground Wire Optical Cable of ±800 kV Ultra-High Voltage Direct Current Transmission Line

In recent years, icing on the ground wire of ultra-high voltage transmission lines has become a major problem threatening the safe and stable operation of transmission lines. In order to effectively solve the problem of ground wire icing on ultra-high voltage transmission lines, this paper proposes a ground wire ice-melting system for ±800 kV ultra-high voltage DC transmission lines during live operation. Firstly, a twelve-pulse valve group and rectifier transformer are selected as the ice-melting device based on technical and economic considerations, and then the ground wire is insulated and transformed to form a ice-melting circuit with single-point grounding. The parameters such as ice-melting current, ice-melting capacity, and ice-melting time are calculated and verified. Secondly, the temperature rise test under ice-melting current is conducted in the laboratory environment to determine the temperature characteristics and safety of the cable, and finally the parameters of the ice-melting device are determined. The ice-melting system is constructed in a selected section of about 14.45 km on a certain  ±800 kV transmission line, and on-site verification of live ice-melting is conducted under rainy, snowy and icy weather. According to the measurement results of the on-site cable temperature monitoring device, the ice-melting system successfully achieved continuous and adjustable ice-melting current and accurate control of cable temperature rise, which is consistent with the calculated results and achieved the expected goals. The results of this paper can provide reference for the live ice-melting of ground wire/cable of ultra-high voltage DC transmission lines.