Research on SO2F2 gas detection in GIS combining interband cascade laser and second harmonic technology

SO2F2 gas is one of the important decomposition products of SF6 in the GIS gas chamber. Based on the analysis of the chemical composition of the gas, the failure prediction of high-voltage electrical equipment can be realized. The SO2F2 gas detection system in the GIS is built based on the second harmonic absorption technology with an inter-band cascade laser with a center wavelength of 3599 nm. The experimental results of the tuning characteristics of the ICL laser show that when the laser works at 35°C and the drive current is 60~100 mA, the emission wavelength of the laser output can cover the wavelength range of 3615.4 nm to 3623.4 nm, which meets the detection requirements of SO2F2 gas at 3619.3 nm. The second harmonic detection results show that the gas harmonic absorption intensity increases with the increase of gas concentration, and the fitted linear correlation R2 is 0.99563, which has a good positive correlation. Collect 300 sets of data, the collection time is 50 minutes, the relative standard deviation (RSD) is 0.29%, and the system detection limit is 357.56 ppb. This method can provide a new method for the optical detection of SO2F2 gas.