直流牵引城市轨道交通系统对地磁观测干扰研究——以天津轨道交通为例

Magnetic perturbation caused by D. C. traction power supply system for urban rail transit——A case study from Tianjin railway transit in China

直流牵引城市轨道交通系统在运行过程中产生的磁场对我国大城市周边地磁台站的观测数据产生较为严重的干扰.城市轨道交通运行过程中产生泄露电流是产生干扰的重要原因.本文通过对天津地铁轨道交通干扰的理论建模和公式推导,定量估算出直流牵引城市轨道交通的系统的磁场干扰幅值大小和衰减关系.通过对模型的数值模拟,获得了干扰的随距离衰减关系曲线和在线路终点的干扰幅值变化曲线.同时,在天津静海开展实地测量天津地铁干扰来验证该理论模型.理论计算和实地测量结果都表明,如果该区域地表介质大致均匀的情况下,天津轨道交通干扰磁场的衰减距离到45公里处仍然存在0.5 nT左右的干扰.

Magnetic field created by D.C. traction power supply system has become a serious man-made perturbation to the operations of geomagnetic observatories near big cities in China. Leakage current produced by D. C. traction power supply system is the most key factor. In this paper, a more general theoretical model of Tianjin railway transit is presented to enable quantitative estimates of this magnetic perturbation. Using this model, we can get two numerical example results： distance decay for magnetic perturbation and the amplitude variations at the end of railway line caused by displacement of locomotive. In order to verify this model, field measurements was carried out in the vicinity of Jinghai, Tianjin. The Earth structure in this area is approximately layered. Theoretical calculations and field measurements shown a good agreement, which indicated that at the distance of 45 kM, the perturbation caused by Tianjin Subway can reach to 0.5 nT.