排流网情况下地铁迷流分布规律的研究

Metro Stray Current Distribution with Current Drainage Net

地铁列车运行时产生的迷流,会对地铁系统及埋地金属结构产生电化学腐蚀,影响其使用寿命及安全运行。地铁迷流很难直接测量,一般通过钢轨纵向电阻、钢轨对地电阻和对地电压等参数来间接计算。作者提出了无排流网情况下的地铁迷流计算公式,建立了考虑排流网情况下的地铁迷流解析公式,修正了原来的迷流估算公式。指出虽然总的迷流并不会因为安装排流网而减少,但流入结构钢筋的迷流明显减小;在排流网与钢轨纵向电阻相同的条件下,流入结构钢的迷流与负荷电流的比值,将减小为无排流网时的平方倍,这证实了排流网的有效性,为迷流的监测与防治提供了理论依据。

The stray currents produced by running Metro vehicles affect the rail transit system and buried Metal structure by causing electrochemical corrosion, and so influence the lifetime and safety of the rail transit system and buried metal structure. The stray currents are difficult to be measured directly. Generally,they are calculated indirectly by using the parameters of the running rail longitudinal resistance, running rail to earth resistance and running rail to earth voltage. The calculating formulae for Metro stray currents are given on condition that the current drainage net is not installed. The analytical formulae for Metro stray currents are also established on condition that the current drainage net is included. The analytical stray current formulae on the condition of the existing current drainage net modifies the stray current calculation formulae deduced in absence of the current drainage net. Although the total magnitude of stray currents is irrelative to the current drainage net, the stray currents leaking to the metal structure are decreased greatly. When the longitudinal resistance of the current drainage net is equal to that of the rail, the ratio of stray currents leaking to the metal structure to load currents is decreased by the squared value of the ratio of the Metro system without the current drainage net. The analysis confirms the importance of installing the current drainage net. The investigation is helpful for monitoring and prevention of stray currents.