Distributed Acoustic Emission Detection Method for GIS Partial Discharge Based on Dual Mach–Zehnder Optical Fiber Interferometry

Currently, piezoelectric transducer (PZT) based sensing systems are the dominant method for detecting partial discharge (PD) via acoustic emission (AE) in gas-insulated switchgear (GIS). Nevertheless, standard PZT systems often struggle to satisfy the stringent operation and maintenance demands of contemporary power equipment. Numerous research teams have recently explored novel acoustic emission sensing technologies based on optical fiber interferometers. Despite these advances, most existing research has concentrated heavily on enhancing sensor sensitivity, often overlooking the potential for multiplexing. Consequently, true distributed sensing capabilities have not yet been fully realized. To address this gap, an acoustic emission detection method based on a dual Mach–Zehnder (DMZ) optical fiber interferometer is proposed in this paper. This method can not only detect high-frequency AE signals but also identify the AE source via the time difference of the arrival of signals at the two interferometers. The latter is crucial for realizing distributed acoustic emission detection of PD in GIS. Based on this methodology, key parameters for the DMZ optical fiber sensing system were designed, and an experimental platform was established to evaluate the response and localization performance of the sensing system. Furthermore, a PD detection experiment on a real 110 kV GIS was conducted to evaluate the detection ability of the system for metallic particle defects. Experimental validation demonstrates that the proposed DMZ sensing architecture can identify discharge events down to the hundreds of picocoulombs (pC) range. The system achieves a signal-to-noise ratio (SNR) approximately 5 dB higher than that of conventional PZT systems. Additionally, the system supports the serial multiplexing of 20 sensing units and achieves a localization error of 6.6 m for the locus of the AE signal activity in the optical path.