Infrared Absorption Properties of SF6 Gas-decomposition Product SO2F2 in GIS Gas Chamber

摘要

HF gas is an important decomposition product of SF_6 gas in Gas insulated switchgear (GIS), and is an important index to evaluate the moisture environment and potential faults of high-voltage combination appliances. Therefore, HF gas detection is of great significance. A tunable diode laser absorption spectroscopy (TDLAS) sensor based on distributed feedback laser (DFB) is used to detect HF gas in GIS gas chamber.The transmitting and receiving circuits of laser signals are designed to realize the modulation of the transmitting laser signals and the control of the laser temperature. Meanwhile, dynamic amplification and voltage tracking are carried out on the detection output signal to further improve the stability and sensitivity of the system. The different sample number corresponding harmonic amplitude index fitting results show that the saturated adsorption after second harmonic amplitude basic remains the same, reaching constant extremum, first-order index fitting correlation coefficient R~2 is 0.995, 0.996, 0.997, respectively, PVDF to sample three times after adsorption saturation, gas testing response time is 3 min, optimal performance. Analysis of adsorption mechanism in SUS304 adsorption process, electrostatic attraction plays a key role, while PVDF and PTFE materials have developed microporous structures, and Vander Waals force plays a major role. HF gas calibration experiment shows that the linear relationship between gas concentration and second harmonic amplitude is well, the fitting coefficient R~2 is 0.9985, the maximum absolute error of concentration inversion is -0.83, the maximum relative error is -2%, and the lower limit of detection is 0.85 PPM. To sum up, TDLAS sensor used for HF gas detection in GIS gas chamber was designed, and the advantages of PVDF material optical path cell in adsorption time and detection accuracy were verified by experiments, and the adsorption mechanism was analyzed from the perspective of material structure.