Research On Temperature Monitoring System For GIS Contacts Based On Multipoint-distributed Fiber Bragg Grating

GIS is widely used in the power system because of the advantage like miniaturization, reliable, high reliability, maintenance friendly and so on. However the characteristics of GIS also lead to the overheat of the conductor especially in the poor contacts condition which can easily develop into major accident. Comparing with other temperature monitoring methods like measuring circuit resistance, partial discharge monitoring, infrared radiation technology, thermal infrared diagnosis technology, fiber bragg grating technology is much more popular and has been a hot area of GIS contact temperature monitoring research basing on its feature like small volume, high accuracy, immune to electromagnetic interference, no interference to GIS operation.The uncertainty of GIS temperature distribution is one of the most important reason that stop fiber bragg grating technology from using in GIS contact temperature monitoring. In order to solve this problem, a coupled multi-physics simulation model is established with finite element method. The calculation of GIS busbar and switchgear with the simulation model reveal the temperature and electromagnetic field distribution, which can provide a reference for installation of FBG sensor. Besides, basing on the GIS busbar calculation model, multiple boundary conditions including solar radiation, wind speed and ambient temperature are taken into account as to analyze the influence of weather conditions on the temperature distribution. The simulated results indicate that, the conductor and the tank temperature’s growth rate increases gradually with the load increase, and the temperature changes in an approximately linear fashion with regard to the ambient temperature. The solar radiation significantly improves the temperature level of GIS, and the tank temperature curve remains as sinusoidal distribution with the hottest spot shifting to the direction of solar radiation. The wind may make the tank temperature curve deviate from the sinusoidal type, however, the heat-conducting capability of SF6 turns to be the main limiting factor on the conductor temperature reduction.In order to test the features of the FBG sensor in GIS temperature measurement and verify the accuracy of coupled multi-physics simulation model, a GIS temperature measuring experiment platform is built, the FBG temperature sensors are selected and the experimental program is developed. Multiple sets of contrast experiment show that FBG sensor has a high sensibility and accuracy in GIS temperature monitoring. The overall trend of the calculated temperature coincided well with the experimental results with small relative errors, which verified effectiveness and reliability of the proposed model.The fitting algorithm of predicting contacts temperature is another key technology in the FBG temperature monitoring. Neural network algorithm, support vector machine algorithm and experience formula method are proposed to calculate the contacts temperature by the tank temperature. The calculated results coincided well with the experimental results with small relative errors shows the three fitting algorithm’s effectiveness. In the end, on-line temperature monitoring scheme for GIS contacts based on multipoint-distributed FBG is proposed and the software system is developed with the Lab VIEW.