Three-dimensional Finite Element Simulation And Protection Of Stray Current Field On Subway

In subway DC traction power systems, the running rails are used as the return path of the train’s current to the supply source. Due to the rails have a poor insulation from the ground, a part of current leaves rails to the ground. These leakage currents are called stray current. Stray current causes a series of serious problems that electrical corrosion for buried metal structures.The normal operation of urban rail transit was effected seriously, and even personal safety could be threated. Therefore, a reasonable subway stray current field model should be built,based on the factors and sphere of influence, researching of stray current protection measures is significance.Presently, the major model of stray current is circuit element model, and that these models were established and simulated under the ideal conditions, it can only macroscopically and qualitatively analyze the effects of different factors on stray current. And it can not be accurately simulated for comlex structures of subway tunnel and geological conditions. Three dimensional finite element models were built by ANSYS. Regarding different soil distributions, different load currents and whether the establishment of drainage net as simulation conditions, the calculated potential of each location. If buried metal and row nets suffer from corrosion in the electric field can be known exactly, in order to determine the scope of protection to take targeted measures. The main contents are as follows:(1) Stray current definition, the organizational structure of the subway system, the mechanism of electrochemical corrosion and subway engineering were taken as the reference,to summarized the hazards of stray current.(2) The circuit element model of the ideal conditions can derivate formulas of stray current, rail current and rail voltage, qualitatively analysis of the distribution of stray current and influencing factors. But many uncertainties are given difficulty, if stray current theoretical derivation could be deduced that its accuracy is not high.(3) Three-dimensional Finite element models and simulations of subway stray current fields were taken by ANSYS. The simulations reveal that different soil distributions, different load currents and whether the establishment of drainage net have a lot of impact, and can get calculated potential of each location. If buried metal and row nets suffer from corrosion in the electric field can be known exactly. In order to determine the scope of protection of stray current to take targeted measures.(4) In response to these simulation results, subway stray current protection measures were researched.