Study Of Fault Location Method For Metro Traction Power Supply System

Urban mass transit is the preferred solution to solve the large and medium-sized urban traffic jams, and has been developing rapidly in recent years. The UMT traction power supply system provides traction power for urban rail vehicle, whose safety and reliability is the premise of the subway normal operations. Owing to no spare characteristics of the catenary, when the traction network short-circuit fault occurs, organizing the maintenance staff to repair the faults rapidly is very important. Therefore studying the fault location method of the UMT traction power supply system, so as to locate the precise positioning of the short circuit trouble point and overhaul the faults quickly, is of great significance for the subway normal operations.At present, mature fault location methods or devices for UMT traction power supply system has not yet been put into practical application. However a rough fault location method, based on engineering experience, has been applied in a city subway; this method uses the ratio of two-terminal short-circuit steady currents for fault location, whose ranging error is about10%of the distance between the traction substations according to the field staff reflect. This paper buildes the short-circuit fault model, then theoretically analysis and simulation of the rough location method has been made, simulation results show that this rough method has higher raning accuracy for remote short-circiut faults, while relatively low for close-up short-circiut. The output-characteristics of rectifier units can explain this raning error difference. Therefor this paper considers introducing two-terminal voltages into the location method, presents an improved location method, and it has higher ranging accuracy for both close-up and remote short-circiut faults. In addition, the two-terminal short-circuit steady currents used in the aforesaid rough method are not time-synchronous in practical application. Combined with DC feeder protection principle, this paper detailedly analyses this asynchronous time, then another new location method about two-terminal electrical quantities is given, which based on genetic algorithm.How to extract the short-circuit fault currents from traction load currents is a prerequisite for fault location. However, because of large amplitude and high current rise of the locomotive starting current, it is difficult to distinguish the remote short-circuit current form the locomotive starting current, thus how to distinguish these becomes a difficult problem. This paper carries on the research of ac locomotive traction performance, slip frequency vector control system and traction load, in order to establish the locomotive traction drive model, and to get the locomotive starting current; and then compares the locomotive starting current with the short-circuit current; finally, distinguishes these two currents based on the differences of their current increment and rise rate, so as to correctly extract short-circuit current.Based on the above analysis, this paper describes the whole design scheme of the metro fault location device in brief, and focuses on fault location hardware system and its control logic design; then debugges this hardware system using the previous simulation data.