Study on the distribution characteristics of stray current in Subway

As one of the most important transportation for residents, metro has been actively popularized and applied in most major cities in China. Metro often uses DC traction power supply system. The running rail also serves return current. Part of return current in the rail leaks into the soil，which called stray current. With the continuous improvement of metro lines, the disadvantages of stray current have become serious. Based on CDEGS software, this paper builds a metro stray current simulation model, and considers the influence of stray current collection devices such as drain net conductors (DNC)., and the effects of different line conditions and fault types on the distribution of stray current are studied by adjusting the structural parameters. Then, the simulation for multi-locomotive in the power supply interval are established to research the variation of stray current when the running state of each locomotive changes. Simulation results show that the rail longitudinal resistance and insulation layer resistivity have a great impact on the distribution of stray current. The influence of partial insulation layer failure is limited, and only the density of rail leakage current increases locally. When the traction current is constant, the locomotive in the middle of the power supply interval will cause more serious stray current problems. When adjacent locomotives are in an accelerated state in the same interval, the rail potential will increase significantly. The simulation results not only provide a theoretical basis for metro operation and maintenance, but also can guide constructors to take preventive measures in advance in the corresponding location. These measures are very vital for restraining the harmful effects of stray current.