The Quantitative Detection Research Of SF₆ Characteristic Decomposition Component H₂S Based On Cantilever Enhanced Photoacoustic Spectrometry

As one of the key characteristic components produced by SF6 decomposition owed to the internal insulation faults in the SF6 gas insulated electrical equipment, H2 S could reflect the severity of the insulation faults and whether the faults involved with solid insulation materials effectively. By quantitative detection of H2 S in SF6 decomposition gas, powerful data supplement could be offered for the SF6 decomposition components method in recognizing the fault category and severity, evaluating the internal insulation condition of the equipment. It is significant to insuring the safe and stable operation of SF6 gas insulated electrical equipment. Cantilever enhanced photoacoustic spectrometry(CEPAS) as an improved photoacoustic spectrometry(PAS) based on the micro cantilever microphone, has a board application prospect in SF6 characteristic decomposition components detection field for the advantages such as no sample gas consume, extremely high sensitivity, good selectivity, et al.This paper summarized the shortage of SF6 decomposition components detection methods now available and the research status of PAS and CEPAS trace gas detection technology. The theory of gas infrared absorption spectral, basic principles of PAS and CEPAS, how the micro cantilever microphone detects the PA signal were described, and the influences on the CEPAS system frequency response were discussed. The theoretical analysis results laid the foundation for the application of CEPAS trace gas detection technology in the SF6 decomposition components detection field.Based on the radiation characteristic of the laser source and the near infrared spectrum analysis of the main components in SF6 decomposition gas, following the selection principle of gas absorption line, the characteristic absorption line of H2 S with a central wavenumber of 6336.62cm-1 was selected as the study objected. By discussing the selection of each device, the CEPAS detection system for trace H2 S was build. The impacts of working temperature and injection current on radiation wavelength of the DFB LD were tested to offer data supplement for the linear wavelength tuning of the DFB LD.The impacts of gas temperature and pressure on the selected absorption line were studied based on HITRAN on the web online simulation, and the infrared absorption characteristic of H2 S gas was obtained. Frequency response of the CEPAS detection system was tested, and high resolution CEPAS spectrum of the selected absorption line was measured. Experimental study on quantitative detection of trace H2 S in N2 and SF6 background gas were conducted respectively, and quantitative analysis model based on the least square regression were built. The detection limit of the CEPAS system for trace H2 S in N2 was calculated as 0.84*10-6, and H2 S in SF6 was 1.75*10-6. The impacts of gas temperature and pressure on the CEPAS detection were studied by experiment The effectiveness of CEPAS system measurement results were evaluated by comparing with the Gas chromatograph-mass spectrometer.