电网拓扑结构对地铁杂散电流分布特性研究

侵入变压器的杂散电流受列车工况、轨地过渡电阻、土壤结构和电网拓扑结构等的影响，探究杂散电流影响因素是防治地铁周边电力变压器直流偏磁的重要手段之一。为研究电网拓扑结构对侵入变压器的杂散电流的影响，构建地铁线路与电网回路动态耦合有限元模型。基于该模型，分析电网单回路与地铁线路不同相对位置在3种典型拓扑电网结构下，侵入变压器的杂散电流变化，仿真结果表明：在3种结构中，放射形结构受杂散电流影响程度最高，且随着电网回路数的增加，侵入电网中的杂散电流总量增多。此外，不论构成电网回路的两变压器处于地铁线路同侧或异侧，随着地铁线路与电网回路之间夹角的减小，侵入回路的杂散电流增大。

Topology of Power Grid and Characteristics of Stray Current Distribution in Metro Systems

The stray current intruding into transformers of metro systems is determined by train operating conditions, rail-to-ground transition resistance, soil structure, and grid topology. Exploring the factors affecting the stray current is an important means of preventing and controlling the DC bias of power transformers around a metro system. A dynamic coupling finite element model of a metro line and grid circuit was constructed to study the influence of grid topology on stray currents intruding into the transformer. Based on this model, the variation in stray currents in the intruded transformer was analyzed for different relative positions of the single circuit of the grid and metro line under three typical topologies of the power grid structure. The results show that among the three structures, the radial structure is the most affected by stray currents, and the total amount of stray currents intruding into the grid increases with an increase in the number of grid loops. In addition, regardless of whether the two transformers forming the grid loop are on the same side of the metro line or on opposite sides, the stray current intruding into the loop increases as the angle between the metro line and the grid loop decreases.