Currently

partial discharge defect detection in on-site gas insulated switchgear(GIS) equipment mainly relies on PZT sensing systems

but their performance is insufficient to meet the high-level operation and maintenance requirements of power equipment. In recent years

many research teams have conducted research on interferometric fiber optic acoustic emission sensing technology. However

most current research focuses only on improving the sensitivity of fiber optic sensors

neglecting the research on sensor multiplexing performance

thus failing to achieve distributed sensing. To address this issue

we propose an acoustic emission detection method based on dual Mach-Zehnder fiber optic interferometry. This method can achieve high-sensitivity detection of high-frequency signals and utilize the time difference of signal arrival at the two Mach-Zehnder interferometers for source identification

thereby realizing distributed acoustic detection of partial discharge in GIS. Based on this method

we design the key parameters of the dual Mach-Zehnder fiber optic interferometric sensing system and build an experimental platform to test the system’s response and positioning performance. Furthermore

a partial discharge detection experiment was conducted on a real 110 kV GIS to evaluate the detection level of the fiber optic sensing system for metal particle defects. Experimental results show that the signal-to-noise ratio of the dual Mach-Zehnder interferometric fiber optic acoustic emission sensing system is approximately 5 dB higher than that of the PZT sensing system. Furthermore

this system can achieve cascaded multiplexing of 20 sensing units with a signal application point positioning error of 4.62 m. By installing the 20 sensing units in the fiber optic sensing array on the surface of each chamber in the GIS

the cavity containing defects can be determined based on the signal application location

thereby realizing distributed sensing and localization of partial discharge defects in GIS.