Abstract:In order to study the intrusion range and degree of subway stray current into the AC power grid, a mathematical model of stray current which is based on the degradation of insulation performance of rail insulation fasteners under actual operation is established, and the stray current leakage of each sleeper is derived. The subway stray current is discretized into a finite point current source according to the number of sleepers, and the Greens function is solved based on the complex image method. The ground potential distribution calculation model caused by the subway stray current is also established, and the commercial grounding software CDEGS based on the boundary element is deployed to verify the method accuracy. The influence of traditional sensitive factors, such as stray current leakage and soil structure, on the ground potential distribution along the urban rail line and the surrounding ground potential fluctuations under the operation of multiple trains in a multi?line transportation hub area are discussed.

Abstract:The leaked stray current during the metro operation causes a change of the nearby surface potential, which results in a variation of the ground potential of grounding transformers, then the transformer DC bias. By studying the stray current leakage mode in the traction power supply system for rail transit and the flow path which causes the transformer DC bias, the mechanism of transformer DC bias generated by the metro stray current is revealed. With the consideration of the action mechanism of stray current on transformer DC bias, the equivalent resistance model of the transformer DC bias caused by the stray current is built with doubleend power supply which is based on the discrete model of the stray current distribution. The mathematical equation of the transformer neutral point current with the changing operating conditions of the rail transit is established, and the numerical calculation of the transformer neutral point is realized. The validity of the model is verified by the CDEGS simulation, which has certain guiding significance for the planning and construction of subway stations and substations.