Ultrasonic Signal Detection And Analysis Based On Fiber FP Cavity

The partial discharge of power transformer will bring great damage to the operation of the electric power substation equipment,cause irreparable economic loss.Partial discharge will produce a series of physical phenomena,such as ultrasonic wave,that can be judged by detecting the ultrasonic signal,once the transformer fails to make emergency repair in time.Because of the Strong electromagnetic and easy corrosion surround the transformer,the traditional piezoelectric ultrasonic sensors can't be used in transformer testing.Optical fiber F-P cavity ultrasonic sensor have the advantages of electromagnetic interference resistance,corrosion resistance,high precision,lightweight,deflection,be able to use in transformer testing system dominant.According to the theory of Fabry-Perot cavity light interference,Manufacture the optical fiber F-P cavity ultrasonic sensor and construct the optical fiber F-P cavity ultrasonic sensor demodulation system by using the sensing characteristic,use the ultrasonic signal that is obtained by demodulation to analysis,launched further study of the ultrasonic sensor sensitivity in order to improve the optical fiber F-P cavity.The main contents are as follows:(1)According to the multiple beam interference theory and sensing principle of F-P cavity,design a kind of optical fiber F-P cavity ultrasonic sensor,analyzes the basic principle of type intensity demodulation and phase demodulation.analysis the quartz membrane structure parameters on the influence of the resonance frequency and sensitivity,through the ANSYS simulation and Workbench platform diaphragm simulation comparison of different structural parameters,optimize the ultrasonic sensor quartz effective radius parameter and thickness of the diaphragm,manufacture three optical fiber F-P cavity ultrasonic sensors.(2)According to the principle of ultrasonic signal detection,optical fiber F-P cavity ultrasonic sensor demodulation system is developed.The design of the hardware circuit of the system is in detail,select the optical components,such as DFB narrow band,low noise photoelectric diode laser diode and fiber coupler,as well as the analysis of the optical device interface and flange.Through the amplifier chip,power and AD sampling chip selection,developed the amplifying circuit,power conversion module and A/D data acquisition module,construct the fiber F-P cavity ultrasonic sensor demodulation system.ResearchanddevelopmentPC software system,PC connect the demodulation instrument acquisition module through USB port,have a real-time data,storage,database and data display,parameter configuration and performance analysis and so on,through testing,PC acquisition,data storage,display functions is normal.(3)Ultrasonic signal generated by electronic pulse discharge through the optical fiber F-P cavity ultrasonic sensors and piezoelectric sensor for detecting signal acquisition,through the acquisition of two kinds of sensors output voltage amplitude in the same source,the sensor output voltage amplitude is studied and the relationship between ultrasonic sound pressure.Through three optical fiber F-P cavity ultrasonic sensor horizontal contrast experiment of the sensor structure parameters influence on sensitivity and natural frequency;Study optical fiber F-P cavity ultrasonic sensors in different medium damping effect sensitivity;Compared the optical fiber sensor and test the performance of piezoelectric sensor.