1.China Railway Electrified Survey Design & Research Institute Co. Ltd, Tianjin 300250,China; 2.State Grid Corporation of China, Beijing 100031,China; 3.China Electric Power Research Institute, Beijing 100192,China；4. State Grid Beijing Electric Power Company, Beijing 100031, China)
Abstract：Abstract：Research purposes： With the lightning faults increasing, overhead ground wire has been used for lightning protection in metro projects. The overhead contact system(OCS) for the vehicle power supplying in metro is different with the power system transmission line, because it was installed above the track and its insulation level is very low. The relevant provisions are lacking in the design codes. The protective effect of overhead ground wire has not been systematically studied in the current domestic metro. There are great differences in the projects that have been implemented. Therefore, it is necessary to study the lightning protection effect of metro overhead ground wire. Using electrical geometric model (EGM)，the relationship of the overhead ground wire installation position with lightning flashover times and the lightning flashover arrester discharge current has been studied in this paper. The proposed solution is given for lighting protection earthing of overhead ground wire. Finally, the application suggestions in metro are put forward in this paper.
Research conclusions：(1) The overhead ground wire can reduce the number of lightning flashover of the OCS. The OCS is higher, the effect is more effective. The overhead ground wire is beneficial to lightning protection in metro.(2) The total lightning flashover times are almost the same whether the overhead ground wire is installed above the OCS or at the top of the pillars. So the overhead ground wire installed at the top of the pillars is suggested to be used. (3) The overhead ground wire can reduce the impact current of metal oxide surge arrester with series gap .The height of the overhead ground wire should be checked to reduce the flashover times of shielding failure to 0.1 times / 100 km·a(40 thunderstorm days). It is suggested that the overhead ground wire is 1 meter higher than the OCS. (4) It is suggested that the earthing device for lighting which is composed of a gas discharge tube and a metal oxide resistor should be connected in series with the earthing line. (5)The research results of this paper can be applied in urban rail transit．
［1］GB 50157—2013，地铁设计规范［S］.
GB 50157—2013，Code for Design of Metro［S］.
［2］DL/T 620—1997，交流电气装置的过电压保护和绝缘配合［S］.
DL/T 620—1997，Overvoltage Protection and Insulation Coordination for AC Electrical Installations ［S］.
［3］GB/T 10411—2005，城市轨道交通直流牵引供电系统［S］.
GB/T 10411—2005，DC Traction Power Supply System for Urban Rail Transit［S］.
［4］GB 50490—2009，城市轨道交通技术规范［S］.
GB 50490—2009，Technical Code for Urban Rail Ttransit［S］.
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Zhang Hao. Analysis of Lightning Protection Effect and Improvement Measures in Tianjin Binhai Line［J］. Electrified Railway, 2008(3):30-31.
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Shen Haibin，Chen Weijiang，Wang Litian，etc. Application of Metal Oxide Surge Arrester with Gap in Metro Overhead Contact System［J］. Electrified Railway, 2010(5):42-45.
［7］边凯，陈维江，王立天，等. 高速铁路牵引供电接触网雷电防护［J］.中国电机工程学报，2013（10）:191-199.
Bian Kai，Chen Weijiang，Wang Litian，etc. Lightning Protection of Traction Power Supply Catenary of High-〖JP〗speed Railway［J］．Proceedings of the CSEE，2013(10):191-199.
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