Design On Protection Device Of Subway DC Power System

Protection device of subway DC power system offers the acquisition of protection data, processing the task of judgment and issued a trip command, and it plays an important role for the security and economic operation of the subway traction power supply system.At present, domestic subway system already has a number of domestic DC protection device in operation, but most still use the foreign DC protection equipment,therefore developing a high reliability and high intelligent DC protection system is of great significance.This paper starts from basic components of the power supply system and basic principles of DC protection, then provides a brief introduction to the protection principle and gives the simulation analyses of the subway traction power supply system’s short-circuit fault and the starting process.Then it also identified the configuration schemes and relevant setting principle of the current fast-tripping protection and di/dt+AI protection. According to the limitation of di/dt+AI protection this paper introduces an adaptive protection principle that based on the current integral value and its average.Then it gives an outline of the detection principle of DC protection data. In the hardware scheme of DC protection device, this paper gives the detailed design of the isolation amplifier module and the central processing unit in the protection device, then setting the values of relevant protection value. In the software design of the DC protection device, it’s divided into several parts as the main program, the display program, the keyboard handling, sampling procedures, interrupt and testing procedures, protection program, and gives protection flow diagram of each module, and carrys out the analysis and design of the control processes realize. At last with the use of MATLAB m language this paper writes a protection program based on the amount of current characteristics and verifies the validity and reliability of the procedure.