The Study Of Short-Circuit Fault On DC Traction System Of Rail Transit Fraction System Of Rail Transit

The importance of the subway to ease traffic pressure are becoming increasingly apparent. The safe and reliable operation of the Metro DC traction power supply system plays a very important role not only in the locomotives operation but also in the passenger safety. DC system has various operation modes, and the short-circuit current is large and hard to remove when fault occurred in it. This will not only cause economic loss, and may even threaten the safety of passengers. Accurate short-circuit calculation of the DC traction system is not only the base of the system design and planning, but also the foundation of relay setting and shows great importance in ensuring personal safety and reducing the loss of faults.This paper analyzes the problems in short-circuit calculation model of DC traction system, and presents a set of fault calculation process meeting the requirements of protection setting and validation by analyzing different fault calculation models. The reasons for producing calculation errors are analyzed. The method of reducing the calculation error in steady-state short-circuit calculation is presented from two aspects of rectifier unit equivalent and knee current. The optimized calculation process is given. Based on the calculation model of transient current of DC-side output short-circuit and remote short-circuit, the overshoot theory is applied to come up with a new method to identify the output short-circuit, close-up short-circuit, and far end short-circuit, and method of calculating the transient current of close-up short-circuit is proposed. Simulation examples confirm the feasibility and accuracy of the proposed models and methods in meeting the requirements of protection setting and validation.Furthermore, an effective method is presented to classify the valve side current by simulating different kind of valve side current and analyzing current characteristics and relevant work status. Then the relationship between DC side current and AC side current of rectifier is deduced. This paper provides a way to analyze rectifier current, as well as a simple and feasible calculation method to make DC side current be equivalent to AC side current.In the end, this paper discusses the DC side current impact on fault point and calculation method of AC side current. Therefore, DC traction short-circuit fault models and calculation theory are completed.