Abstract：Research purposes ： The traction network in an electric railway is a single - phase unbalance network with the earth, so there is an earth return current when it operates normally. A large earth return current indicates the impeded return current in the overhead contact system. The current is forced to return to the substation through the earth. It may bring a large current in the grounding grid of the substation, which causes overheat or even burning. It may also raise the rail potential, and threaten the safe running of the signal devices beside the rail. The operating performance of the traction power supply system and the driving safety can be worsened. The earth return current in a direct feeding network is calculated with the simulation software developed by the authors. The influences of different structures and parameters on the magnitude of the earth return current are compared and analyzed.
Research conclusions ： (1) The results reveal that the impedance relationship between the return network and the earth is the main factor influencing the earth current. To decrease the earth current, we can decrease the impedance of the return circuit, increase the grounding resistance, and reduce the leakage loop. (2) For the T - R feeding system without the return conductor, adding the overhead return conductor is an effective method. (3) To resolve the excessive large earth current problem, we should ensure the traction current return to substation freely and there should be no break or tortuous loop in the return circuit. (4 ) The research conclusions can be the references to the analysis of traction substation earth return current and resolving the excessive large earth current problem.
2015, Vol. 32 
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