Study On Identification Of Transformer Magnetizing Inrush Current Based On The Slope Mean Ratio Of Differential Current

Transformer is the key equipment of the power system,and its safe operation is related to the running state of the whole power system.The main protection of the transformer is the differential protection,and the main factor that affects the correct action rate of transformer differential protection is the correct identification of magnetizing inrush current and fault current.In order to achieve the protection device go right,the power supply can be recovered quickly after the fault is removed,and the electric power equipment over current impact can be reduced.It is very meaningful and valuable to fully understand the mechanism of magnetizing inrush current and to realize fast and accurate identification of fault current and inrush current.This paper mainly analyzes the magnetizing inrush current and after removal of external faults recovery inrush their respective mechanism,influencing factors and their effects on differential protection.The existing methods of identifying inrush current are analyzed and evaluated.In order to study angle and remanence whose effect on inrush current,In this paper,PSCAD simulation software is used for simulation and comparison.In order to study the waveform characteristics of inush current and fault current,simulation is done to the short-circuit fault and magnetizing inrush current of the transformer.On the basis of analyzing the difference characteristics of inrush current and fault current,a method based on the slope mean ratio of differential current is proposed to identify the magnetizing inrush current,and the Matlab program is designed.Transformer model is established in the PSCAD,simulate under different closing phase angles and different fault current waveforms,and then income waveform data into the compiled MATLAB algorithm of using the new method for calculation and identification inrush current and fault current.The results showed that the newly proposed method is simple and easy to operate,It is affected by the waveform distortion is small,and the new method can corectly identify inrush current and fault current.