Acoustic-Enhanced Fiber-Optic MZI Sensing Technology for Partial Discharge Detection in Silicone Rubber Insulation

The fiber-optic Mach–Zehnder Interferometer (MZI) acoustic sensing technology offers unique advantages in partial discharge (PD) detection. However, its sensitivity for PD detection in silicone rubber insulation remains insufficient, posing significant risks to the safe operation of power equipment. This paper proposes using a fiber-optic MZI system with an acoustic enhancement structure to detect PD in silicone rubber insulation. Firstly, an acoustic-enhanced fiber-optic sensor (AFS) was developed based on the theory of the acoustic black hole. This sensor was then integrated with MZI sensing technology to form a PD detection system. Subsequently, the system was utilized to analyze the frequency-domain response characteristics of the AFS to identify the sensor material with the best performance. Finally, a PD test platform with a needle-plate electrode configuration in silicone rubber was constructed to evaluate the PD detection capability of the AFS. The results indicate that polycarbonate is a suitable material for fabricating AFS. For a needle electrode with a curvature radius of 60 μm in a silicone rubber needle-plate electrode configuration, the AFS can detect a minimum PD magnitude of 56.0 pC. When the curvature radius of the needle electrode is 15 μm, the detection sensitivity of the AFS surpasses that of the high-frequency current transformer, the cylindrical fiber-optic sensor, and the piezoelectric transducers (PZT) sensor. The initial PD voltage detection sensitivity is improved by 7.7%, 25.0%, and 46.1%, respectively. The proposed fiber-optic MZI system with an acoustic enhancement structure significantly improves the sensitivity of PD detection in silicone rubber insulation.