Analysis the ligthning accident of Mass Rapid Transit System and discussion the grounding

With rapid development of Mass Rapid Transit System in China, it brought more convenience and comfort. The Mass Rapid Transit System are engineering projects with highly centralized information, electrical, and electronic system, the lightning brings serious threat to this control system, and the safety of passengers. In order to reduce the damage and loss, 19 lightning accidents are analysing in this reaearch, the result shows unreasonable setting of grounding system is the main factor. Analysing the simulation model result, shortenning the distance between catenary pillars grounding electrode, reducing grounding resistance, installing line surge arrester can improve the line lightning perfermance. Numerical methods is used to caculate the ground network resistance, reducing soil resistivity and increasing area of ground network are more considerably way to lower grounding resistance. At ground network design, the ground resistance of subway power supply system can not be greater than 1Ω, but in main substation, its grounding resistance should be designed by no more than 0.5Ω. Using the Three-Electrode angle method by large ground network tester and the correction formula could get relatively accurate grounding resistance at the practical testing.