Optical Sensing System Based on Bidirectional Self-Correction Technology: An Online Detection Method for Carbon Disulfide and Sulfur Dioxide in Gas-Insulated Switchgear.

Carbon disulfide (CS2) and sulfur dioxide (SO2) are typical indicative gases for the early warning and diagnosis of faults in gas-insulated switchgear. In this study, an optical sensing system is reported for online detection of CS2 and SO2 based on a bidirectional self-correction technology (BSCT). First, the differential absorption signals of CS2 and SO2 in the wavelength range of 195-230 nm are obtained using the UV differential optical absorption spectroscopy (UV-DOAS) technique. On this basis, a BSCT is proposed to decouple the spectral lines that exhibit significant overlap. This method primarily employs bidirectional difference spectroscopy to mutually correct the spectra of CS2 and SO2, combined with spectral reconstruction to extract the single-component absorption signals of CS2 and SO2 from the mixed gas spectra. Furthermore, the effectiveness of this novel decoupling technique is validated by comparing the decoupling results with the absorption spectra of single-component standard gases at corresponding concentrations. Finally, the quantitative relationships between the concentrations of target gases (CS2, SO2) and the optical parameters are modeled using the least-squares method. The experimental results show that the mean absolute percentage errors of CS2 (19.00-3735.35 ppb) and SO2 (0.19-38.77 ppm) are 0.543 and 0.521%, respectively. At an effective optical range of 50 cm, the system achieves the lowest detection limits of 0.5 ppb for CS2 and 12 ppb for SO2, representing the best results reported to date for the online detection of CS2 and SO2 in the ppb-ppm range.