Experimental Study on the Detection of Trace H2S and H_2O in High Voltage Combination Appliances Based on TDLAS Technology

摘要

H_2S and moisture content are important indicators to evaluate the potential faults and insulation performanceof H_2S electrical appliances. Currently, there is no report on the simultaneous detection of H_2S gas and moisturecontent. In order to realize the accurate detection of H_2S gas and H_2O at the same time, lorentz simulation analysiswas performed on the absorption spectra of H_2S gas and H_2O molecules. The absorption was strongest near2684nm, and there was no cross interference of SF6 other decomposition products. H_2S and moisture content atdifferent concentrations were measured by TDLAS technology in a customized CW-DFB laser with a centralwavelength of 2.68μm combined with a small-volume Herriott long-range cell with multiple reflections. In order toverify the detection ability of selected spectral lines to H_2S gas and H_2O molecules at low concentration, trace H_2Sand H_2O vapor with SF_6 as background were detected by direct absorption technology and wavelength modulationtechnology respectively. In the second harmonic absorption, the minimum detection lower limit of H_2S and H_2O is9.01×10~(-6) and 4.54×10~(-6), respectively. The maximum harmonic signal amplitude has a good linear correlationwith concentration, and the linear fitting degree R~2 is 0.978 and 0.997, respectively. SF_6 gas displacementexperiments with different flow rates showed that the equilibrium time of H_2S and moisture content at 708mL/minwas 90s and 100s, respectively. The response time of H_2S and H_2O at the same concentration and injection velocityis 30s and 45s, respectively. Wavelength modulation technology can provide a reliable experimental basis for thesimultaneous detection of trace H_2S and H_2O in high voltage combination electrical appliances.