| Long-term partial discharge is one of the main factors for failure of high-voltage power equipment.Therefore,the partial discharge of the high-voltage power equipment is detected,and the equipment is repaired before the fault occurs,which can effectively reduce the economic loss caused by sudden failure.Due to the existence of high voltage and strong magnetic fields and other environmental factors in high-voltage power equipment,for the detection of partial discharge,ultrasonic signals generated when detecting partial discharge can be used for judgment.The traditional piezoelectric ultrasonic sensor is limited by environmental factors and cannot be detected inside the transformer.The use of fiber-optic ultrasonic sensors has the characteristics of strong magnetic field resistance,high pressure resistance and corrosion resistance,and can adapt to this environment.In this paper,according to Fabry-Perot multi-beam interference principle,a fiberoptic Fabry-Perot(FP)cavity ultrasonic sensor is developed,and the common fiberoptic FP cavity ultrasonic sensor coupled diaphragm material is used for analysis and comparison.At the same time,the use of different materials processed into a coupling diaphragm,and the preparation of optical fiber FP cavity ultrasonic sensors and the establishment of a fiber optic ultrasonic sensor demodulation system.In addition,the in-depth study and analysis of the demodulation system,improve the performance of the detection system,and use the sensor and demodulation system to collect and analyze the ultrasonic signal,to prove the reliability of the fiber FP cavity ultrasonic sensor and demodulation system work.The main research content is as follows:(1)The working principle and structure of the FP-cavity fiber-optic sensor were studied.The fiber-optic FP-cavity ultrasonic sensor was designed.The commonly used diaphragm material quartz glass,optical glass and single crystal silicon(100)material were compared and analyzed using ANSYS simulation software.The relationship between radius and natural frequency,half-path and static sensitivity of different diaphragm materials was obtained.At the same time,optimized simulation of diaphragm structure parameters was performed on selected materials,and optical fiber FP cavity ultrasonic sensors were prepared using diaphragms made of different materials.(2)A fiber optic ultrasonic demodulation system was developed for the optical fiber ultrasonic sensor to transform the ultrasonic signal into a correspondingly changed optical signal.A distributed feedback laser(DFB)is used to output a narrow-band beam,and the fiber-optic ultrasonic sensor modulates the light source signal and returns the modulated light signal.An optical fiber ultrasonic sensor demodulation system was designed.The photoelectric conversion circuit,operational amplifier circuit,A/D acquisition circuit and filter circuit were developed.The demodulation system demodulates the modulation signal and converts the analog signal into a digital signal.Through the communication and data transmission between the master control chip and the host computer,the collected data is transmitted to the host computer,and the data is completed in the host computer software.Store and display.(3)Using a fixed-frequency ultrasonic signal source,using a piezoelectric ultrasonic sensor and an optical fiber FP cavity ultrasonic sensor of quartz glass material at the same position,the same signal source is measured to verify the accuracy of the optical fiber ultrasonic sensor.The fiber FP cavity ultrasonic sensors were then prepared using different materials of the diaphragm,and the ultrasonic waves generated by the high voltage discharge were detected.Then the optical fiber ultrasonic sensors of different material diaphragms were compared and the influence of the materials on the sensitivity and natural frequency of the sensors was studied.,And the diaphragm response characteristics of different materials. |
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