Research On Overvoltage Mechanism And Prevention In The Network-Locomotive Coupling Of The High Speed And Heavy Haul Railways

With the development of the high speed and heavy haul railway in China, there raise a lot of problems in traction power supply system, one of which is the overvoltage and its prevention in the coupling between the system and the locomotive (or the high-speed motor train-set). In recent years, the problems in traction power supply system, such as ferroresonance overvoltage, overvoltage of the split phase, the rail voltage raise and the integrated earth wire etc., which have not been theoretically studied enough and well solved in engineering. Thus, they momentarily threaten the stability of electrical equipment insulation and the correspondence signal device; the security of traction power supply system and the locomotive (motor train-set). It is significant to study the causing mechanism of the overvoltage and the prevention methods. This paper explored these problems which appear in coupling overvoltage of the traction power supply system and its prevention.In order to analyze the ferromagnetic resonance overvoltage, this paper compared each kind of fitting function of magnetization curve which describes the transformer core material silicon steel plate; chose the improvement exponential function form; guaranteed the magnetization curve in the nonlinear section's fitting precision; then guaranteed the accuracy of ferromagnetic resonance overvoltage analysis. Furthermore, discuss the relationship between the exciting inductance and transformer parameters as well as voltage; study the saturation phenomenon of the excitation inductance of the vehicle-mounted transformer by the method of numerical calculation; illustrate the mechanism of ferroresonance overvoltage in traction power supply system; put forward the method of eliminating ferroresonance overvoltage.According to the physical process of a locomotive passing the neutral section, the system consisting of the traction network and the locomotive is divided into four transient processes. State equations are created by utilizing linear system theory. In these transient processes, voltage at pantograph is calculated by using typical parameters of the system. Calculative results indicate that overvoltage generated by single electrical transient process does not harm the insulation of the locomotive roof. Gradually increasing voltage at pantograph will eventually breakdown the protest gap or make the surface flashover on the insulator of locomotive roof because the reignition of electric arc leads to alternate occurrence and influence of two transient processes. Because of randomness of the voltage phase when the locomotive pass the neutral section, randomness of generation and extinction of the electric arc between the neutral section and pantograph possess, so overvoltage of the splitting phase is produced randomly.The conception of the attenuation constant is presented, and it was measured in the practical field. Analyze the distribution rule and affection factor of the rail voltage and current; improve the calculation method for grounding resistance of the integrated earth wire; deduce the formula for current allocation proportion between the integrated earth wire and rail; discuss the affection factor of the current allocation for the integrative earth wire based on rail resistance; integrate earth wire resistance, leak conductance between the rail and the ground, leak conductance between integrated earth wire and the ground, the soil electric resistivity.