Research On Design Of The Stray Current Net System In Subway

Now, the urban rail transit becomes a forceful measure to solve the problems of urban public transport, because it doesn’t occupy the city floor space to relieve urban congestion and uses electric traction to be conducive to reduce the pollution. The DC traction is always powered in the urban rail transit system, and the subway system is usually supplied by the traction voltage, which is750V or1500V.In the metro power supply system, the DC current flows from the traction substation to the OCS. And the Pantograph-catenary system provides electric power to the locomotive, then the current is back to the substation along the rail. Rail track being fully insulated away the ground, is quite difficult. Thus, the current leaks from the rail and forms stray current, which causes corrosion to the buried metal damage along the MTR lines. In long-term, stray current can make the buried metal badly damaged, causing huge economic losses. The stray current flowing in the earth, forces the potential difference along the path, which may endanger people’s safety.After grasping the principle of stray current corrosion, it’s a considered and attentioned problem that how to set up a more effective stray current net system, during subway construction survey and design phase. The stray current system is consised of drainages and protections, whose profession are involved in a lot of influencing factors. Also, the system of metro stray current is a comprehensive project that is required the mutual cooperation of various professions.This article mainly is discussed the following aspects:firstly, it is expounded the status and significances of the stray current. And then, in the basis of which the principle to the formation of the stray current and the corrosion mechanism that the stray current causes, it is compared with traditional resistance distribution network model, to establish a new stray current model on the " rail track-stray current net-buried metal-the earth " structure resistance distribution network. Through Matlab simulation, each factor is compared, which influence in the traditional model and new model. On the basis of the new model, analyzing the longitudinal resistance range of the stray current net, it is raised another consideration factor to adjust rows of the stray current net structure in the design. Then, it is built out a set of stray current system. After the Matlab simulation of the system working, it is described the advantages and disadvantages. Finally, some basic requirements are summarized, which is on relevant professions of metro stray current corrosion protection in a subway project, among the survey, design, construction and operation. They are considered each factor with a more comprehensive perspective, as some reference to the protection in the metro stray current system of the relevant professions.