Research On Design Of Microcomputer Main Protection System For Traction Transformer

Traction transformer is one of the important devices in electric railway power supply system, which supplies incessantly power to electric locomotive, and the stability and reliability of its running is directly related to the railway transport safety. With the development of the electric railway and the rise of the high-speed railway, there are higher requirements on the performance of the traction transformer protection system. Because it could restrain the affection of negative current to electric power system and has a high utilization rate of capability, the impedance-matching balance transformer has been widely applied and has been the main connections of railway traction transformer.Presently the traction transformer in China most adopts differential protection principle as the main protection. However, the magnetizing inrush current at no-load switch and the imbalance current at external short circuit will bring differential protection lots of disturbance, and make it hard to distinguish internal fault or external fault, thereby result in that the protection makes a faulty action or refuses action. So, lots of scholars pay attention to the research of novel principles for traction transformer protection. The paper proposed a traction transformer protection principle based on parameter identification according to analyzing the limitation of differential protection principle, built the identification model of impedance-matching balance transformer, and verified the feasibility of the new principle by simulation, finally respectively designed the platform in hardware and software for the traction transformer protection system based on parameter identification. The following research works has been completed in this paper:①Studied the structural feature, running principle and transformation relationship of impedance-matching balance transformer between current and voltage in each self, and especially analyzed the limitation of differential protection principle resulted from the magnetizing inrush current at no-load switch and the current at external short circuit.②Propounded a traction transformer protection principle based on high voltage side parameter identification, which could distinguish internal fault or external fault of the traction transformer without identifying the magnetizing inrush current.③Established the identification model of impedance-matching balance transformer after analyzing the transformer's electromagnetic properties. ④By means of MATLAB and recursive least square algorithm, it made the simulation for the resistance value and the short circuit reactance value for the impedance-matching balanced transformer high voltage side, and verified its feasibility of the traction transformer protection system based on parameter identification.⑤Designed a new hardware platform and a software platform for the traction transformer protection device based on protection principle of parameter identification.