地铁邻近埋地金属管线杂散电流分布特性研究

Study on Stray Current Distribution Features of Adjacent Buried Metal Pipelines in Metro System

城市轨道交通直流牵引供电系统引起的杂散电流泄漏以及钢结构腐蚀危险已成为地铁规划建设及公众关心的敏感问题,城市地下管网面临与地铁隧道密集交叉、紧邻或长距离平行敷设等情况,研究地铁邻近埋地金属管线的杂散电流分布特性,对于提高埋地金属管线耐腐蚀寿命、改善腐蚀防护方法具有重要意义。建立地铁隧道杂散电流仿真计算模型,分析轨对地过渡电阻对杂散电流分布的影响,针对金属埋地管线相对钢轨空间方位变化开展杂散电流分布及金属相关腐蚀参数计算。结果表明,当轨对地过渡电阻为0.5Ω·km时,钢轨杂散电流泄漏总量较15Ω·km和3Ω·km分别增加了2 618.5%和500.7%;不同轨对地过渡电阻下,钢轨、排流网、金属管线、土壤中的杂散电流占泄漏总量的百分比基本保持不变,均随泄漏总量的增加而呈等比例增加。埋地金属管线相对钢轨位置变化对其沿线杂散电流大小和方向有明显影响,对于距离钢轨水平间距≥100 m的埋地金属管线年腐蚀量均维持在mg量级。

Stray current leakage and steel structure corrosion caused by DC traction power system have become sensitive issues of metro planning and public concern. Urban underground pipe network is faced with the situations of intensive crossing, close proximity to or long-distance parallel with metro tunnels. The distribution features of stray current are of great significance to improve corrosion resistance and corrosion protection methods of buried metal pipelines. In this paper, the stray current calculation model of the metro tunnel is established to analyze the influence of the rail-to-earth resistance on the stray current distribution, meanwhile, metal corrosion parameters and stray current features are calculated according to the spatial orientation change between buried pipeline and rail. Results show that when the rail to ground transition resistance is 0.5 Ω·km, the total leakage of rail stray current increases by 2 618.5% and 500.7% respectively compared with the total 15 Ω·km and 3 Ω·km. The percentage of the stray current in rail, stray current collection network, metal pipeline and soil to the total leakage remains unchanged basically under different rail-to-earth resistance, and increases in equal proportion with the increase of the total leakage. Spatial orientation change between buried pipeline and rail has a significant impact on the magnitude and direction of stray current. For buried metal pipelines 100m or more away from the rail horizontally, their annual corrosion amounts are maintained at the grade of “mg”.