Depth-Study On The City Subway Stray Current And Suppression Measures

In recent years, with the continuous development of urbanization, the importance of large-capacity rail transport in some modern large cities become increasingly evident. The DC power supply mode is mostly used in the urban rail transit traction power supply system. In this system the currents always return back through running rail. Since the running rails on the ground, which is not absolutely insulated, will produce a large number of stray currents and corrosion the steel structure and related metal equipment, causes great economic losses. Therefore, in this paper, the distribution law of stray current is deeply analyzed, and the corresponding stray current suppression measures are also put forward.In this paper, firstly, it has a further discussion of the cause and hazard of stray current. Secondly, the mathematical models of stray current distribution is established, they include: running rails-earth, running rails-drainage net-earth, as well as running rails-drainage net-assisted drainage net-earth three kinds of continuous and discrete models of stray current distribution. Thirdly, the mathematical models are simulated and analyzed with MATLAB software. And the variation of running rail voltage, current and stray current is found through changing the relative parameters. Finally, the way to suppress stray current and the measuring method of parameters associated with the stray current are put forward.In addition, because the model is added drainage net, according to the needs of engineering practice, the calculation of drainage net cross-section is presented in this paper. The principle, which is related to establish the size of the drainage net cross-section, is to ensure drainage net longitudinal voltage is less than the standard value.According to the theoretical and simulation, the main conclusions of this paper as follows:To reduce the stray current, the most fundamental measures include: the resistance per unit length of running rails/earth needs to be increased as possible as it can. Then the resistance per unit length of running rails, the traction load and the distance between substations should be reduced. As for the resistance per unit length of drainage net interconnected structure, it plays only a minor role in controlling stray current.