Research on Fiber-Optic Sagnac Sensor for Acoustic Emission Detection of Partial Discharge in Transformer Tank Wall via Solid-Medium Coupling

Partial discharge (PD) detection is one of the most important techniques for transformer insulation diagnosis. Among the ultrasonic detection methods, externally mounted sensors are widely used. However, due to their external installation, the attenuation of ultrasonic signals by the tank wall is significant. To address the issue of low sensitivity in current externally mounted ultrasonic detection methods, this study enhances the sensitivity of externally mounted fiber-optic sensors by encapsulating the sensing fiber within the stress-concentrated region of a core shaft. Simulation results demonstrate that the encapsulated fiber-optic sensor exhibits significantly improved stress response. Experimental results further validate the feasibility of polymer encapsulation in enhancing the measured ultrasonic signal strength of the sensor.