Research On High Voltage Switchgear Partial Discharge On-line Monitoring Based On Ultrasonic Sensor

High voltage switchgear is a kind of important equipment in power system,whose reliability and stability is essential to the normal operation of power system.Insulation fault is one of the main faults of HV switchgear,and we can judge its insulation state by monitoring its partial discharge.Among all the partial discharge detection methods,ultrasonic method is favored because it avoids electromagnetic interference in the detecting scene theoretically.However,China still adopts periodic maintenance method that has much limitation.Based on this situation,we develop a set of on-line monitoring system for partial discharge in high voltage switchgear.The main work includes:(1)Expound the mechanism of partial discharge,and do research on partial discharge in high voltage switchgear combining with its structure.(2)Analysis the acoustic theory of generation,propagation and attenuation of partial discharge ultrasound,which provides a theoretical basis for partial discharge ultrasonic monitoring.(3)Design the hardwire circuit of partial discharge ultrasonic monitoring system and make it tested.The hardware includes partial discharge ultrasonic sensor,signal preprocessing analog circuit,digital circuit and power supply circuit.(4)Do research on digital noise reduction of partial discharge ultrasonic signal.According to the different types of interference,FIR filter,FFT algorithm and wavelet packet algorithm are used to reduce the noise.(5)Do research on partial discharge evaluation method.Combine threshold method and trend method to judge the insulation state of high voltage switchgear.Introduce OBV and PVT indexes into the partial discharge trend analysis,and process it with moving average method.