The Research On DC Feeder Protection Of DC1500V Third Rail Power Supply System

With the rapid development of China's economy, the situation of urban traffic jam has been a more and more serious problem; therefore, the best way to resolve the urban traffic jam is developing the city railway greatly, for instance, metro. The power supply form of DC1500V third rail has been a new direction of metro development for its advantages of decreasing construction investment as well as operation & maintenance cost. The relay protection system plays an important role of metro traction power supply in assuring its safe operation. At present, the protection equipments for domestic DC1500V third rail traction power system are mainly imported from foreign countries, therefore, it is necessary to research protection ways and parameters based on the analysis of DC short circuit faults in traction power supply system.In this paper, the basic principle, structure and grounding of DC1500V third rail traction power supply system are analyzed, and the DC short circuit faults including metallic faults and nonmetallic faults which are probably occurred during its operation process are also analyzed Then the fundamental and characteristic of main protections and backup protections in common use for metro traction power system are discussed in the thesis. On the basis of analyzing the characteristics of rectifier and traction rectifier transformer with axial split structure, the calculation method of DC stable short circuit current depending on rectifier characteristic is given through project example.24-Pulse traction rectifiers in metro DC traction substations and short circuit faults under different work conditions of a certain metro project adopting DC1500V third rail power supply form are simulated by Matlab/Simulink. Then the transient starting and passing third rail fracture currents of metro locomotive equipping with line motors are simulated in the thesis. Associating with the setting principles of IDS and DDL protections, IDS and DDL parameters are set in a certain operation section and the results show the setting is correct and rational.