Analysis Of An Optimized Protection Design In Rail Transit Power Supply System

With the city’s prosperity and economic development, the phenomenon of urban traffic congestion accompanied. Large passenger traffic subway system can fundamentally improve the urban public traffic conditions. The power supply system of the metro is a power source. AC medium-voltage ring network is an important part of city transit system. Therefore improve relay protection of the urban rail transit power supply system AC medium-voltage ring network is essential.The current domestic built metros mostly adopt centralized partition of power supply mode. Relay protection configuration scheme is mainly used for: fiber longitudinal differential protection as the main protection, definite-time overcurrent protection and zero sequence current protection as a back-up protection. In order to reduce the ring network cable investment and total cost, the new rail transit line-powered systems are increasingly adopting the "large series ring" power supply scheme, conventional protection scheme of the power supply system of the " large series ring " medium voltage ring network in order to meet the electricity system requirements, ring overcurrent protection will not be achieved step by step with only sacrifice some selective, will expand the scope of the effects of the accident. Visible, conventional protection scheme of the power supply system of the "large series ring" there are some flaws.In order to further improve the protection of medium voltage ring network, subway 35kV large-series-ring power supply system protection scheme is proposed in this paper. Use the longitudinal optical fiber differential protection, definite-time overcurrent protection, low voltage protection and breaker failure protection cooperation. Use protection device communication between protection devices and freely programmable function. When a fault occurs, the failure can be quickly identified and isolated. Solve the General Protection Configuration of the power supply system of rail transit problems with time differential, selectivity, speediness and other issues. Protection device is applied the GOOSE communication technologies to solve the problems of the conventional protection scheme of interlocking relationships between the protective devices difficult to debug hard-wired cable and wiring complexity. Specific scheme is detailed introduction in the paper.Under the normal or non-normal operation mode, metro power supply system failures that may occur in the operation, the failures be simulated to prove the scheme of accuracy, speed, reliability and selectivity.