Study On AT Traction Power Network Rail Potential Factors

High-speed electrified railway is developing rapidly and will be the inevitable trend of transportation system in the future. Autotransformer (AT) supply system has been applied more and more extensively in the long-term practice. It is good at anti-interference and suitable for large current high-speed and heavy-load operating. It also have several technical advantages some other supply modes do not have. But at the same time because of the large fault current and small leakage conductance, the rail potential where the train running is too high to control. In the worst case human and equipments safety has been threatened seriously.In this paper, AT supply system and the formation mechanism of the rail potential have been discussed. The research status and obtained achievements of rail potential problems at home and abroad have been introduced, and qualitative analysis has been given.The factors influenced rail potential, the distribution of induction current and conduction current and the total current have been analysesed in detail. The theoretical formula of rail potential has been derived. According to the in-depth analysis and the actual situation of engineering application, the necessity, feasibility and implementation of solving the problem have been briefly explained.The factors which influences rail potential such as CPW, rail leakage conductance, AT leakage reactance, grounding resistance and rail cross line have been considered in this paper. Under AT traction supply, sequence network model which is suitable for rail potential calculation has been built, according to generalized method of symmetrical components, the relationship between sequence current and traction current has been studied, and at last the calculation formula of sequence impedance has also been derived. At he same time, based on the theoretical knowledge of the in-depth study, the multi-conductor transmission model and equivalent model have been built and.M-file for rail potential has been compiled under Matlab/Simulink environment. According to the calculation and simulation, the influence when AT traction network parameters change has been studied, and the results from those models have been compared.Through the comprehensive analysis, the trend of changes on rail potential when chose different parameters of AT traction network have been obtained, based on the track in actual engineenng.