Objective Compared with traditional detection/monitoring technology, the distributed optical fiber has absolute advantages compared with traditional method in terms of technical performance and practical application. It can detect the physical quantities such as temperature, displacement, vibration, and pressure, and has the advantages of high sensitivity, no electromagnetic radiation, large dynamic range, and wide adaptation range. In order to further strengthen the monitoring and operation of GIL and reduce the influence of a large number of sensing equipment on the structure of the equipment, the integrated monitoring and research of GIL shell vibration, temperature and strain is carried out. An optical cable realizes multi-parameter signal sensing, and the operation law of GIL is explored on the premise of reducing the number of sensing equipment.

Methods Long-distance high-drop GIL multi-parameter integrated distributed optical fiber sensing and monitoring system uses multi-core optical cable as a sensing unit to collect and control data by computer to realize long-distance and large-range pipeline safety monitoring. The system mainly includes temperature and strain measuring unit, vibration measuring unit, multi-core optical cable, data acquisition center and control platform (Fig.3).

Results and Discussions The vibration, temperature, strain and other multiple parameters of the gas insulated metal closed transmission line called GIL are collected through distributed optical fiber sensing technology, and the data are studied and applied for the collected data. Through vibration, strain, temperature monitoring test and data analysis, the system can accurately measure the vibration, strain and temperature data of optical fiber perception, and the data is accurate and reliable. The temperature measurement accuracy of the test system is ±0.5 ℃, temperature spatial resolution is ±0.6 m, positioning accuracy is ±0.3 m, system strain measurement accuracy is ±20 με, system vibration positioning accuracy is ±2 m and vibration positioning accuracy is ±2 m. Through the integrated monitoring study of GIL shell vibration, temperature, strain and other multiple parameters, the GIL operation rule is explored under the premise of reducing the number of sensing devices.

Conclusions Distributed fiber sensing technology is used to carry out multi-parameter signal collection and monitoring of vibration, temperature and strain of GIL shell. Combined with the application environment and project objectives, on the basis of calculation method theory and application research, the reliability of the development of the monitoring system of the whole system is ensured, the performance index of the whole system is realized, the multi-parameter monitoring requirements for the long-distance and high-drop GIL pipeline is met. A single optical fiber can realize the sensing and measurement of multiple points throughout the GIL pipeline, and intuitively show the running status of GIL. In the future, the system will continue to go deep into the pipeline fault identification, improve the intelligence of the model, and provide technical support for the intelligent operation and maintenance of the GIL pipeline.