Power Transformer Differential Protection Technology Currents Of The Identification Research

In recent years, along with the continuous improvement of the China power grid and further expand, long-distance, high voltage grade and high-capacity transmission can become the important way of conveying energy. In power grid of safe and reliable, stable operation process, power transformer of relay protection of important sex self-evident. The main protection for power transformer differential protection to protect concerned, relay protection device and its correct operating rate there's also a considerable raise space. Among them, to correct operating rate of increase must also from power transformer excitation current currents of the recognition of power transformer, effectively identify the internal fault current or excitation inrush current is the key to the problem. Usually, the traditional differential protection ignores power transformer excitation inrush current, correct operating rate is not very high. Therefore, the research electric power transformer differential protection of excitation inrush current recognition, to the safe and stable operation of power system, high power grid, intelligent power grid goal has very important practical significance.This paper from the power system protection based on some problems of power transformer, relay protection technology made corresponding overview of power transformer, and the current situation and development trend of the relay protection makes brief analysis; Combining the current transformer excitation inrush current no-load test, the characteristics of qualitative analysis, combining the current some excitation inrush current identification method and the corresponding components, made comparatively detailed analysis and exposition. Through power transformer equivalent circuit and quantitative analysis on the premise of the magnetic power transformer, and find fault current and excitation inrush current characteristics and differences between and establish a corresponding physical model. Through the normal operation of transformer models, grounding short-circuit, coil short-circuit quantitative analysis, list three kinds of condition equations, and, in these equation is proposed on the basis of proposed power transformer protection scheme. The scheme is the most main according to protect the value for the difference equations with actual setpoint comparison, set action to distinguish fault current and excitation inrush current.Finally, the article through mutual inductance should coefficient method and to identify, in a coil no-load transient, short-circuit, winding grounded with Matlab/Simulink running state of the simulation results, and simulation with theory are discussed, this scheme on power transformer excitation inrush current recognition and internal fault current recognition is feasible; Of course, the final conclusion is feasible. The scheme is feasible, but also for the new method after differential protection test and actual application provides theoretical basis and guidance method.