High-Sensitivity and Wideband All-Polymer Microcavity Fiber Acoustic Sensor and Its Applications in Partial Discharge Detection

An all-polymer microcavity fiber acoustic sensor and its applications in partial discharge (PD) detection for power equipment are proposed and demonstrated. The sensor adopts a sandwiched structure comprising a sensing film, polymer cover, and polymer ferrule. Due to its all-polymer structure with a lower Young’s modulus and small size, it shows a maximum frequency response within 68 Hz to 524 kHz, and it has a high sensitivity of 20.99 V/Pa at 25 kHz with the minimum detectable sound pressure level, 34.1 μPa/Hz 1/2 . In addition, the sensor exhibits a flat response and a high signal-to-noise ratio in the 10–200 kHz range, making it ideal for acoustic signal detection. The sensor was applied to PD detection in stator bars of the large hydroelectric generator, where it demonstrated the ability to detect PD signals at distances of up to 50 cm from the insulation damage point. Statistical analysis identified key frequency ranges (24–28 and 32–36 kHz) for further optimization, and the results highlight its potential for real-time PD monitoring in smart grids and industrial applications, with advantages in sensitivity, frequency response, and immunity to electromagnetic interference.