Simulation Analysis of Distribution Characteristics of Urban Rail Transit Stray Current in Power System

Abstract

The stray current generated by urban rail transit could cause DC magnetic bias problems in transformers round the subway, threatening the safe and stable operation of transformers and AC grid systems. In order to solve such problem, the static distribution model of subway stray current, the multi-layer block soil model of Shenzhen and the simulation model of Shenzhen AC power system were established. The variation of the ground potential of the AC power grid substation and the distribution characteristics of the neutral point DC current of the transformer caused by the stray current were calculated and analyzed. The results show that the change of ground potential and DC current through transformer neutral point is related to the operating conditions of the subway. For the autotransformer, it is pointed out that the installation of the capacitive blocking device only at the DC over-standard site cannot eliminate such DC magnetic bias problems, and it is necessary to properly arrange the blocking device from the perspective of the entire regional power grid.