Design and Experiment of SF6 Decomposition Product CF4 Sensor in GIS by NDIR Technology

CF4 gas is an important decomposition product of SF6 in high voltage combined electrical equipment. Its content can not only characterize the surface discharge of insulating materials, but also has the great significance for the research of potential defect diagnosis technology of high voltage combined electrical equipment based on the gas analysis. The gas sensing and the detection system of SF6 decomposition product CF4 is developed based on the NDIR technology. The system adopts the single-light source and dual-wavelength structure, which can effectively eliminate the unstable factors and has the high measurement accuracy. System was calibrated and calibrated by the linear and first-order exponential function fitting in the range of high and low ranges, and the fitting coefficients R-2 were 0.985 and 0.994 respectively, showing good consistency. Combining NDIR principle measurement technology with grey system OBGM (1, N) model fitting and prediction technology, The CF4 gas volume fraction high-precision measurement and the wide-area time interval gas concentration fitting can be realized. The experimental results show that maximum error is -4.25% within measured concentration range, which increases with the increase of gas concentration. The maximum RSD% is less than 3%, showing good stability. This system can provide the novel method for the rapid detection of CF4 gas in GIS.