地铁运行状态变化下杂散电流对埋地管道干扰数值模拟

目的研究地铁系统运行状态多变性导致地铁杂散电流对埋地管道的干扰规律。方法构建具有多个牵引区间、排流网、地铁站接地系统及停车场的地铁系统,埋地管道及其阴极保护系统等模型,基于数值模拟方法,采用专业软件计算地铁机车数量、位置及牵引电流变化,地铁排流网、站内接地系统和停车场与线路轨道电导通状况等地铁运行状态变化下轨道对地电位分布,轨道和排流网泄漏杂散电流密度分布,接地系统和停车场杂散电流量、以及杂散电流干扰时的埋地管道电位分布,分析确定地铁运行状态变化下杂散电流对埋地管道干扰规律。结果地铁系统采用焊接而成的长走行轨回流时,任何牵引供电区间内运行的机车及电流变化,均会对靠近地铁线路的埋地管道造成干扰,干扰有叠加效应。干扰最大位置出现在埋地管道与轨道的交叉点或并行段,且并行间距越小,最大干扰水平越接近交叉点处的干扰水平。当地铁排流网、站接地系统和停车场轨道不与线路轨道电连接时,能够一定程度降低干扰水平,当与轨道在局部电连接时,会使得邻近埋地管道所受干扰程度剧增。结论地铁运行状态变化致使埋地管道电位波动,且波动程度与机车运行状态、接地系统或停车场轨道频繁与线路轨道电连接状态、排流网性能及工作状态等地铁运行状态息息相关,在干扰检测和防护中应关注地铁运行状况变化。

Numerical Simulation of Stray Current Interference Rules on Buried Pipeline from Metro System under Different Operative Modes

Stray current interference on nearby buried pipeline from metro system under variable operating conditions is complicated, so that the interference rules are difficult to obtain through field tests. In this paper, a numerical simulation model including an entire metro system with multiple traction sections, drainage network, grounding systems in stations and a parking lot, the buried pipeline and its cathodic protection system are constructed. Based on the numerical simulation method and professional software, the potential distribution of rail to earth, the leakage stray current density distribution from rail and drainage network, the stray current flow of grounding systems and a parking lot, and the potential distribution of buried pipeline under stray current interference are calculated under different metro operating conditions such as changes of the number, location and traction current of metro locomotives, the electric connections of drainage network, grounding systems and rails in the parking lot with the main track. The interference rules of stray current on buried pipeline from metro system under different operating conditions are determined. The results show that stray current interference on nearby buried pipeline occurs and is superposed from multiple traction sections with running locomotives. The maximum interference occurs at the intersection or parallel section of the buried pipeline and the track, and the smaller the parallel distance is, the closer the maximum interference level is to the interference level at the intersection. When the drainage network, grounding system in stations and parking lot track are not electrically connected with the main track, the interference level can be reduced to a certain extent. However, when the drainage network, grounding system in stations or/and parking lot track is locally electrically connected with the track, the interference level on buried pipeline will increase dramatically. The potential fluctuation of buried pipeline is caused by the change of metro operating condition, and the fluctuation degree is closely related to the running state of locomotives, the electric connection state of rail with grounding system or parking lot, the performance of drainage network and its working state, etc. Therefore, attention should be paid to the change of metro operating condition in metro stray current interference detection and protection.