Study On Distribution Of Metro Stray Current Based On Multi-Locmotive Operation

Metro adopts Direct Current (DC) traction for power supply, and rail, as the return line of traction current concurrently, cannot be absolute insulation with the earth. This causes part of the current to leak to the earth, which forms the alleged stray current. Stray current can cause electrochemical corrosion of the metal buried around the metro, shorten the service life of the metal pipes, reduce the intensity of the building facilities and even worse threaten the safety of the personnel. Therefore, the establishment of the stray current distribution model and the forecast of the electrical quantity distribution such as stray current, rail potential etc., when the metro is operating, can provide certain theoretical basis for the designation, construction, operation and maintenance of the stray current protection, to guarantee the construction quality and the operation safety.Currently, single-locomotive model is generally used in the analysis of the stray current distribution. The boundary condition is either one substation (one way feeding) or two substations (two way feeding) in the process of building single-section bus model. Besides, electric locomotive is only considered to obtain current from substation nearby. However, all these hypotheses do not match with the actual operation of the metro, which causes large errors between calculation results and the actual value.In order to better reflect the distribution of each electrical quantity in the actual metro lines, the thesis is based on "rail-drainage net-buried metal-earth"(underground structure with four layers), which is more closer to actual lines, and both the locomotive and traction substation are taken as injection current sources that affect the underground structures to produce the stray current. This thesis adopts micro-element algorithm and superposition principle to obtain the mathematical model (multi-locomotive stray current model) that inflects the stray current, rail potential and other quantities when multi-locomotive is operating. On this basis, it builds the corresponding simulation mode through Matlab simulation software. Based on the simulation, it analyzes the effect of the distribution of the full line stray current and ground network parameters under the situation of operating multi-locomotive in a metro line. Simulation results show that multi-locomotive stray current model can reflect the distribution of stray current in the whole line more accurately.