Research and Development of NDIR Sensor and Its Application In On-Line Detection of CF4 Gas

Abstract

Due to the excellent insulation and arc extinguishing properties of SF6 gas, it is widely used in the production and use of high voltage GIS. However, due to the breakdown of discharge and overheat, SF6 gas decomposes and produces a variety of low fluorine sulfides. Therefore, the concentration of CF4 gas in the high-voltage switch state can be effectively determined by detecting high-voltage GIS. This paper puts forward a kind of semiconductor laser based gas detection (NDIR) technology, the flange fixed installation in high voltage switch, optical fiber sensing structure can realize remote, real-time online monitoring of CF4 gas content. The experiment shows that the flange fiber optic sensor on-line monitoring device can realize the effective measurement of CF4 gas. The research results show that maximum field intensity on the surface of basin insulator is 10.788kV/mm, which is lower than the control field strength of 20kV/mm under the SF6 gas insulation condition, therefore the E-field near the basin insulator does not affect the operation of the optical fiber sensor. In the case of 1m light path, the detection limit of CF4 gas near 1312nm is less than 0.5ppm. The results of this study can provide an entirely new scheme for on-line monitoring of high-pressure open-light SF6 gas decomposition products, which can realize real-time on-line monitoring of the internal gas of the high voltage GIS equipment.