He Huiwen

Comparison and analysis on over-voltage and insulation coordination of UHV AC transmission system between China and Japan

The technology comparison and analysis on the over-voltage and insulation coordination of UHV AC transmission system between China and Japan have been carried out in this study, which may include the level of the power frequency temporary over-voltage, switching overvoltage and secondary arc current and the measures to restrict them, the lightning protection methods for transmission line and substation, the insulation level selection of substation apparatuses and the external insulation air clearance selection of the transmission line and substation. The corresponding UHV technologies of China and Japan have been selected based on their own characteristics of the UHV power grid. The research achievements may be helpful for the development of the international UHV transmission technology.

Lightning protection of 1000 kV AC power transmission lines and substations

First of all, in combination with characteristics of the lightning performance of UHV power transmission lines and on the basis of the analysis of experiences and lessons concerning excessively high lightning trip-out rate on 1000 kV transmission lines in Japan and the former Soviet Union, authors of this paper put forward that one of the critical points in the key technical research on 1000kV transmission lines in China should be the reduction of lightning fault rate, and definitely present the prevention of shielding failure flashover as the main orientation in the research on lightning protection. The paper presents that the reduction of ground wire shield angle and distance of the gap with an appropriate length is an important measure for reducing shielding failure trip-out rate of 1000kV transmission lines. Therefore, it is particularly necessary to pay attention to the shielding failure flashover of the lines in mountainous areas with bigger inclination of ground along the lines. In this paper, authors introduce the ground wire shield angles used for UHV transmission lines in plain and mountainous areas in China as well as the operation situation of UHV transmission lines in China in recent two and a half years. Lightning trip-out faults have never occurred up to the present time in Chinas UHV transmission lines, thus preliminarily showing a good lightning performance. The authors also introduce the method and principle used for calculating lightning inrush overvoltage to UHV substations in China and put forward that the concurrent adoption of measures of both reducing the maximum lightning current of shielding failure at the incoming line section and optimizing the arrangement of lightning arresters to restrict the lightning inrush overvoltage to substations, thus either meeting the demand of restricting overvoltage and reducing the quantity of MOAs used.