Research On Contact Fault Diagnosis Of On-load Tap Changer Based On Electromechanical Joint Feature Analysis

On-load tap changer is an indispensable and important part of on-load voltage regulating transformer,it is of great importance to ensure the safe operation of on-load voltage regulating transformer.Therefore,the realization of on-load tap changer operation condition monitoring and fault diagnosis is very important to ensure the normal operation of the transformer.Considering that the fault caused by the performance failure of the on-load tap changer accounts for a large proportion of the total fault of the on-load voltage regulating transformer,and the on-load tap changer has the characteristics of current carrying sliding electrical contact,which is easy to produce phenomena such as wear,spark and ablation in the tapping process,which is easy to cause the contact performance of the component contact head to decline,the on-load tap changer contact is studied.Combined with the actual structural characteristics of the on-load tap changer contact,this thesis collects the mechanical vibration signal and high-frequency current signal in the process of contact sliding on the on-load tap changer contact simulation experimental platform built,analyzes and diagnoses the operation state of the on-load tap changer contact,and provides a solution for the condition monitoring and fault diagnosis of the on-load tap changer.The innovative research work carried out in this thesis is as follows:(1)A test platform simulating the contact sliding of oil immersed on-load tap changer is built,and the mechanical and electrical characteristic signals of on-load tap changer under different states are collected.Based on the actual switching principle of on-load tap changer,a simulation platform for contact sliding test of oil immersed on-load tap changer is designed and built in the laboratory environment.Based on the experimental platform,the vibration signals and high-frequency current signals at both ends of the on-load tap changer contacts under normal,loose,slight wear and severe wear are collected respectively.(2)An improved fuzzy C-means clustering method for on-load tap changer contact operating state diagnosis is proposed.Firstly,wavelet packet transform is used to denoise the collected mechanical vibration signal.Secondly,the marginal spectrum and marginal spectral energy entropy are obtained by using set empirical mode decomposition and Hilbert transform.Finally,the Grey Wolf algorithm is used to optimize the fuzzy C-means clustering algorithm,and the marginal spectral energy entropy is used as the eigenvalue input of the optimized fuzzy C-means algorithm for state diagnosis.The results show that the optimized fuzzy C-means clustering has a clearer clustering center and clustering results,and the diagnosis accuracy of different states of on-load tap changer is higher.(3)The method of electromechanical joint characteristic analysis and fault diagnosis of on-load tap changer contact is proposed.Through the noise reduction preprocessing of electromechanical signals,the correlation relationship of tap changer telecommunications in different states is determined by correlation analysis.On this basis,through the decomposition and feature extraction of electromechanical signals,the marginal spectrum and marginal spectrum energy entropy of electromechanical signals are obtained,which are used as the input of support vector machine for on-load tap changer contact operation state diagnosis.The results show that the error between the accuracy of switch state diagnosis based on electromechanical signal and the actual state is less than 10%,which verifies the efficiency and feasibility of electromechanical joint feature analysis in on-load tap changer fault diagnosis.