The Study Of Short-Circuit Current Calculation And Fault Location Method Of Dc Traction Power Supply System

Metro power supply system is an important part of the subway project, its security and reliability is a prerequisite of metro operations. In order to improve the reliability of metro power supply system, measures can be taken from two aspects. On the one hand, the traction network should equipped with protection devices, so as to reduce or eliminate the traction network outage time, at the same time, after faults of the traction network occur, protection devices can cut off the fault current quickly and selectively, reducing the range of failures. On the other hand, fault location device is needed, which can give the fault location and help speed up the repair progress after the fault occurs.In this paper, the principle of the24-pulse rectifier is analyzed, the calculations of the rectifier transformer equivalent circuit parameter and output characteristic of the rectifier are proposed. In addition, the skin effect of the running rail is significant, the electrical parameters of the running rail are variable in the transient process of the short-circuit current, this article uses Ansoft to study the skin effect of the running rail.Calculation of traction network transient short-circuit current is the basis of the protection device parameter tuning, after modeling of metro power supply system, the transient short-circuit current calculation has been researched. After studying the calculation method of close-up and remote short-circuit faults currents of the6-pulse rectifier, corresponding calculation method of the24-pulse rectifier is given. Furthermore, a second-order model for calculation of both remote and close-up short-circuit faults currents is obtained. In the second-order model, the DC side parameters meanwhile the AC side parameters are considered, in order to overcome the limitations to close-up or remote fault current calculation model.Theoretical analysis of the fault location method used by a city Metro has been made, and fault location error sources are analyzed. On this basis, the voltage is introduced into fault location method, then a improved fault location method based on double-terminal electric quantities has been got. However the double-terminal fault location method requires large hardware investment, a single-terminal fault location method has been proposed, and genetic algorithm is used for solving the fault location equation. The simulation results show that the proposed two fault location algorithms have acceptable location accuracy. A fault location system based on two-terminal electrical measurements is designed, and the whole scheme is described, some important issues in the fault location system are introduced.