Research On Comprehensive Lightning Protection Performance Of The±800KV UHV DC Transmission Lines

UHV DC transmission bears the long-distance and large-capacity transmission task and occupies a very important position in the power grid. While the line after more area and the environment even worse, the line is more vulnerable to lightning damage. So the research on lightning protection of±800kV UHV DC transmission lines is necessary.This paper summarizes the development of HVDC technology, lightning overvoltage mechanism as well as the research status of line lightning protection at home and abroad, on the basis of analysis of the calculation theory and method of DC transmission line lightning protection, lightning back-flash performance simulation model was established by using PSCAD software. Shielding failure calculation model was established based on Electrical Geometric Model, and considering the effect of the working voltage and wind speed.By using the simulation model, the lightning protection performance of transmission line was calculated and analyzed, the results show that, the lightning back-flash level of±800kV UHV DC transmission lines is higher, flashover of transmission lines is mainly caused by the lightning shielding failure. The effects of line voltage and wind speed on the calculation results are of large, so that it should be considered in the calculation. The height of tower, ground resistance, insulation levels will have different influence on the lightning back-flash level, reducing the ground resistance of towers is an effective measure to improve the lightning back-flash level. The height of conductor, protection angle, ground obliquity have important influence on the lightning shielding failure level, suggested that lines use negative protection angle, for the height of the tower is too high and the ground obliquity is of great, transmission lines should use additional lightning protection measures.At last, the reasons for high rate of lightning flashover in China are analyzed, including lightning activity increased, lack of line protection measures and human factors etc, and puts forward the lightning protection measures and improvement scheme.