Settlement monitoring for ultra-long GIS equipment based on weak fiber Bragg grating sensing

With the widespread use of Gas Insulated Switchgear (GIS) in substations, the impact of foundation settlement on the safety of equipment has attracted increasing attention. This paper investigates a weak fiber Bragg grating static level meter (wFBG-SLM) that can be deployed on a large scale. It utilizes wFBG as temperature and pressure-sensitive elements and establishes a network using time-division multiplexing. Hundreds of sensors can be connected to a single fiber, making it particularly suitable for long-term real-time settlement monitoring of ultra-long GIS equipment foundations. A sensitivity of 0.06mm/pm and a long-term monitoring accuracy of ±0.4mm were achieved through analysis and testing of this wFBG-SLM. The system has been applied to monitor the foundation settlement of GIS equipment in a ±800kV Ultra High Voltage (UHV) converter station. The obtained two months of monitoring data align well with manually observed data and this system demonstrates significant value for widespread application in related structures.