The Study Of Simulation And Experiment For The Detection Of Winding Deformation Of Transformers By Frequency Response Analysis

With the improvement of voltage level and overall scale of power system,the safe stability becomes increasingly important.As one of the core of electric equipment in power grid,power transformer's reliability directly determines the safe stability of the power system.According to the statistic fault data of the transformer,winding deformation occupies a considerable proportion.Sensitive and effective on-line monitoring mechanical deformation of transformer winding can timely detect winding deformation and prevent deformation expanding to serious fault.Frequency response analysis method is an effective technology,which could monitor externally and evaluate health status of transformer winding.In this paper,the simulate and experimental research had been carried on the detection of winding deformation by frequency response analysis.The test system for detection for winding deformation of power transformer was developed based on the frequency response analysis method,and the test platform for the simulation of different winding deformation was set up.Electromagnetic field simulation was carried out on power transformer based on the finite element software COMSOL and distributed parameter circuit model was established.Then,the frequency response curve of the winding was obtained by MATLAB.The main research results were as follows:The changing law on frequency response curve by inductance when winding was bucked had been explored.The results showed that Inductance have a certain influence on the frequency response curve in high frequency band.The changing law of capacitance and inductance on frequency response curve was opposite,which explained the frequency response curves sightly changed in low frequency and greatly change at high frequency before and after the winding deformation.The changing characteristics of different degree on the frequency response curve had been studied.The results showed that frequency response curve integrally and slightly offset to the left and up when winding became radial deformation,and frequency response curve integrally and slightly offset to the left and down when winding became axial deformation.Besides,the change was even more significant at high frequency with the increment of deformation degree.Besides,The changing characteristics of different types on the frequency response curve had been studied.The results showed that the influence of different types for frequency response curve was not the same in different frequency band.The mathematical index method for the improvement of diagnosis of frequency response curve before and after winding deformation had been studied.Relative to the traditional correlation coefficient method,euclidean distance not only had highsensitivity for the change of resonance frequency but also had high sensitivity for the change of resonance amplitude.Windowed calculation improved the sensitivity of winding deformation by mathematical index method.Besides,euclidean distance after disposed by windowed calculation could be characteristic quantity of degree and types.Finally,fisher discriminant method successfully diagnosed degree and types of winding deformation.