Sensitivity Enhancement Packaging Technology for Fabry-Perot Partial Discharge Sensors

Addressing the issue of degraded ultrasonic partial discharge detection sensitivity in packaged extrinsic Fabry–Perot interferometric (EFPI) sensors, this paper investigates encapsulation technologies for Fabry–Perot optical fiber ultrasonic sensing. A novel encapsulation structure integrating acoustic impedance matching with acoustic focusing capabilities is proposed. Theoretical modeling of sound pressure transmission was established, and COMSOL simulations were employed to optimize encapsulation materials and structural parameters, resulting in significantly enhanced acoustic wave transmission efficiency. Based on this foundation, experimental studies were conducted for external partial discharge detection in transformer oil. Results demonstrate that the proposed encapsulation increases the sensor’s response amplitude by approximately 60% at 117 kHz, while achieving doubled signal intensity for partial discharge detection compared to unencapsulated sensors, effectively enhancing the capability to detect weak partial discharge signals. The encapsulation technology for Fabry-Perot optical fiber ultrasonic sensors based on an acoustic focusing structure can effectively enhance the detection sensitivity for weak partial discharge signals in oil.