Fault Diagnosis Of Switch Cabinet By Ultrasonic And TEV Combined Detection Method

35kV metal clad switchgear has been widely used in substations.It is the key electrical equipment in power system.Rapid and accurate inspection and identification of pd is of great practical significance to ensure the safe operation of power network and improve the stability of distribution equipment.TEV and ultrasonic test technology and characteristics make it suitable for high voltage switchgear partial discharge test.Therefore,it is of great practical significance to carry out in-depth research on the mechanism and test methods of these two methods.In order to better study the discharge fault diagnosis,firstly,the ultrasonic inspection method of high Voltage switchgear and the partial discharge inspection method of Transient Earth Voltage（TEV）are studied.According to the characteristics of partial discharge of switch cabinet,suitable ultrasonic sensor and TEV sensor are adopted.Design make the discharge needle plate,surface discharge,suspended discharge and internal discharge of the four typical faults model of partial discharge,the method of using ultrasonic method and the TEV carried out partial discharge test and typical defects of partial discharge,time domain analysis and the characteristic of the frequency spectrum of switchgear multi-source partial discharge signals separation technical grade application were studied.The ultrasonic spectrum characteristic database of various typical discharge models is established,and the BP neural network algorithm is used to carry out pattern recognition of ultrasonic partial discharge signals and TEV discharge signals.The research shows that both TEV algorithm and ultrasonic algorithm are based on the analysis and solution of continuous signal,some algorithms can be universal,but the main parameters of the characteristics are different.Finally,on the basis of the above research results,a set of comprehensive partial discharge inspection plan for high voltage switchgear based on ultrasonic method and TEV method was established and clearly proposed to use TEV and ultrasonic method to test partial discharge.The test results show that the precision positioning method is simple and high precision,which can meet the requirements of engineering application.Ultrasonic method.