| Traction transformers are important devices in electric railways system, along with the new material, the new craft development and the heavy load, the high-speed railroad transportation need, and the capability of transformer becoming bigger and bigger, the requirement for improving performance of transformer protection relay becomes stronger. It is an effective approach to improve the performance of transformer protection relay by introducing new theory and new technique to transformer protection relay.The paper analyses the principles of distinguishing internal faults current from inrush current and their defects at the present time on the basis of investigating widely the existing papers on identification of inrush current. The system recognizes the theory to take the modern control theory to the electrical power system has recognized the theory in the elaboration system, analyzed the system to recognize in the theory to utilize more typical least squares method, and used the main algorithm which the recursion form the least squares method achievement recognized. Basing on differential protection, the dissertation emphasizes the study of the discrimination method three-phase to two-phase balanced transformer basing on identification of winding parameter. Based on linear equation, a novel protective principle according to identification of winding parameter is presented, and its operation characteristic and operation equation are proposed. Simulation results by using software demonstrate the feasibility and availability.It is confirmed that compared with conventional current differential protection, identification of winding parameter is being predominant in distinguishing magnetizing rush current from fault current. These results about the influence on the performance of differential protection are useful to the design of protection scheme and setting of the threshold, thus have certain significance for the performance of the differential protection transformer in power system. |
