Identification Of Transformer Inrush Current Based On Energy Components

With rapid development of national economy, the scale of electrical power system also expands. Since applications of High-power transformer have been increasing over the years, the reliability and speed ability of the protection of transformer is required. However, the veracity of the protection itself is restricted by inrush current discrimination when transformer closes its switch without load.The generation mechanism of the field excitation inrush current is detailed analyzed in this dissertation. Based on the typical feature of the inrush current which distinguishes from the fault current, methods of identifying the inrush current are dissected such as the principle of intermittent angle, principle of second harmonic braking, principle of waveform symmetry, etc. Under the comprehensive consideration of the advantages and disadvantages of these methods, a method of identifying the inrush current is proposed on the basis of energy compositions: to analyze and detect the current signal mutation points with multi-resolution, to identify the inrush current according to the distribution of these points on the time axis, and to achieve the whole process of identifying the inrush current with the use of FPGA.Simulation results verify the stability, reliability and practicality of the proposed energy compositions method, overcome the deficiencies of traditional protection, and improve the performance of transformer differential protection effectively.