An optical sensor based on chemical conversion and partition differential optical absorption spectroscopy is developed to detect hydrogen sulfide (H2S) and sulfur dioxide (SO2) gas in sulfur hexafluoride (SF6) decomposition products. Given that the absorption cross sections of SO2 and H2S overlap in 170-230 nm band, the differential lines of H2S are very few, meanwhile the corresponding absorption cross sections are small in comparison to that of SO2, thus H2S can be detected by reacting with oxygen to convert to SO2 in the presence of UV light. Through the concentration variation of SO2 before and after chemical reaction, the concentration of H2S can be obtained. Meanwhile the partition differential optical absorption spectroscopy method deduced from Beer-Lambert's law is introduced to weaken the influence of electronic noise on the measuring result, especially in low concentration. The SO2 detection limit of 12 ppb per meter can be achieved. The optical sensor can measure the concentrations of H2S and SO2, so it is suitable for the fault diagnosis of gas insulated switchgear (GIS).
Keywords: Chemical conversion; Hydrogen sulfide; Partition differential optical absorption spectroscopy; Sulfur dioxide.
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