The Transformer Protection Based On Parameter Identification

With the development of economic and improvement of living standard, the demands of power increase rapidly. More and more large capacity transformers were applied to meet the increasing power system scale. The reliability of power system was affected by the safe operation of transformer. During the operating of large capacity transformer, all kinds of failure and accidents could be happened. The correct operation rate of transformer protection was far below other power system protection, which was the main limitation to enhance the safety and reliability of power system. Therefore, to improve the correct operation rate of transformer protection was vital important.Differential protection was applied for transformer nowadays. Distinguishing the excitation surge and internal faults effectively was the key point to guarantee the veracity of operation by a measure of excitation surge braking. Aim at the complexities of transformer faults and fault characteristic quantities, basing on the theory of parameter identification, an identification method was used to gain the parameter characteristics of transformer under different operation conditions, addressing troubleshooting problems of transformer, achieving a new transformer protection solution by parameter characteristics.A simulation model was set up by ATP-EMTP software for different operation conditions. By simulating no-load input, the internal wingding grounding fault, internal turn-to-turn short circuit, internal line to line fault, external fault elimination and other operation conditions of transformer, data for identification were acquired.After addressing the simulation data by adding white noise, the least square method was applied for parameter identification on Matlab platform. The impedance parameters identification of transformer under different operation conditions was proceeded. Besides, the error of identification was analyzed. The effectiveness of parameter identification method to identify the parameters of transformer under different operation conditions was improved. The parameter characteristics of transformer under different operation conditions were included, which were used for diagnosing faults and fault types of transformer.