Development Of Optical Fiber Sensor For Arc Discharge Acoustic In Transformer And Study On Voiceprint Characteristics

Power transformer is an important core equipment of power system,which plays a vital role in the safe and stable operation of power grid.Statistics show that insulation problems are the main cause of power equipment faults and accidents,and arc discharge is an important manifestation and symptom of transformer insulation deterioration.Therefore,timely and effective online monitoring of arc discharge defects is of great significance for real-time condition monitoring and fault analysis of transformers.At present,optical measurement,gas chromatography,infrared thermography and other methods are mainly used to monitor arc discharge,but these methods are vulnerable to electromagnetic interference and cannot be built into the transformer to accurately identify arc defects.The previous research shows that the ultrasonic signal and audible sound signal will accompany the arc discharge in the transformer,which provides a new idea for the monitoring and diagnosis of the arc discharge in the transformer.In view of the above problems,this paper has carried out the development of optical fiber acoustic sensor for arc discharge in transformer based on fiber grating and the experimental study of its voiceprint characteristics.The main conclusions are as follows:1)The structure of transformer internal arc discharge acoustic sensor based on fiber Bragg grating is designed,which proves that transformer oil has good compatibility with optical fiber.Aiming at the problem that the cross sensitivity of stress and temperature affects the measurement accuracy of the sensor,a dual fiber Bragg grating temperature compensation method is proposed.The results show that the sensitivity of the sensor to temperature is reduced to 20%without compensation,and developed a transformer internal acoustic sensor with large measurement range and excellent anti-interference performance,which has both audible sound and low-frequency ultrasound.The measurement frequency band range of the sensor is 1-60 kHz.2)Three different acoustic sensors are used to measure the frequency range of arc discharge under test conditions,and the measurement range of the optical fiber acoustic sensor is tested and verified.The acoustic signal frequency band sensed by the audible sound sensor is mainly 20 Hz-8 kHz,the acoustic signal frequency band sensed by the SR40M ultrasonic sensor are mainly 15～25 kHz and 50～60 kHz,and the acoustic signal frequency band sensed by the optical fiber acoustic sensor are mainly 2～10 kHz and 50～60 kHz.3)Based on the optical fiber acoustic sensor,the voiceprint feature of arc discharge in the real transformer are measured:the acoustic signal frequency band sensed at the top of the transformer oil tank is mainly 1～8 kHz;The acoustic signal frequency band sensed at the high-voltage side of the transformer is mainly 1～10 kHz,and the ultrasonic frequency is 44 kHz.4)By comparing the energy of each frequency range of the sound signal spectrum perceived by the top of the transformer tank and the high-voltage side,it can be found that,with the occurrence of arc discharge,the proportion of energy in the ultrasonic frequency band of the acoustic signal increases,while the proportion of energy in the audible frequency band decreases.The proportion of audible energy perceived by the top of the tank and the high-voltage side decreases to about 98%and 70%respectively.