Distributed optical fiber sensing for metal particle defect detection in GIS via frequency-swept interferometry

Conventional detection of metal particle defects in gas-insulated switchgear (GIS) mainly relies on piezoelectric (PZT) sensors, which are inadequate for distributed monitoring in modern power equipment. Although interferometric optical fiber sensors offer high sensitivity for GIS partial discharge detection, they are generally limited to single-point measurements. To address this issue, this study proposes a multiplexing method for optical fiber acoustic emission sensors based on optical frequency-scanning in a Michelson interferometric configuration. By introducing high-frequency carriers through optical frequency modulation and separating channels via bandpass filtering, the proposed method preserves the high sensitivity of conventional single-point interferometric sensors and extends it to multiplexed sensing, enabling frequency-division multiplexing of multiple sensors using a single demodulation system. Experiments on a 126 kV GIS with four sensing units demonstrate that the proposed system can effectively detect discharge signals and identify the defective cavity. This work provides a promising approach for distributed GIS condition monitoring.