Study on the electromagnetic coupling relationship between subway and power grid

At present, the development of rail transit in China is very rapid, and the subway greatly facilitates people's transportation. Since the metro adopts THE DC power supply system, the dc magnetic bias fault of the transformer in the surrounding AC power network will be caused by the metro, which will affect the operation of the AC power network. The current research literature considers that the stray current of subway leads to the potential difference between the grounding grids of two substations at different positions, thus causing the dc magnetic bias fault of the transformer. This paper studies the feasibility of generating DC magnetic bias current through electromagnetic coupling between space electromagnetic field and nearby transmission lines while traction power supply catenary provides energy for subway. Firstly, the electromagnetic coupling model between subway overhead contact network and nearby transmission lines is established, the coupling relationship between them is deduced, and the influence law of different factors such as subway depth and grid area on grid induced voltage is analyzed. Then, a field measurement was carried out in a subway section of Chengdu city, a simulated grid loop was built, and the induced voltage signal of the simulated line was collected when the subway vehicles passed. It is found that subway traction power supply system has strong coupling effect on AC power network. It is also found that the induced voltage of the traction network on the grid is not only related to the relative position of the subway and the grid, but also related to the running state of the train. When the subway vehicle runs in the coupling interval, the moving magnetic field generated by the vehicle movement has a greater influence on the DC magnetic bias than the magnetic field generated by the catenary current.