Ultraviolet differential spectroscopy quantitative analysis of SF6 decomposition component SO2

SO2 is a symbolic gas that can indicate the insulation status of SF6 insulation electrical equipment. Its accurate quantitative measurement is of the great significance for the judgement of the type and severity of faults inside the insulation equipment. For this reason, a detection system of trace SO2 based on ultraviolet (UV) spectrometry was presented. The measured UV absorption spectra of SO2 were processed using the wavelet analysis to remove useless spectra information and get the UV differential absorption spectra of SO2. The fast Fourier transform (FFT) was used to analyse UV differential spectra in the band of 190-230 and 290-310nm and extract the feature information. The results show that there is a good linear relationship between the FFT characteristic peak value and the concentration of trace SO2 in the two wave bands. The detection limit in the band of 190-230nm was even lower than that in the band of 290-310nm. Besides, the differential absorption cross section of SO2 decreases with the increase of temperature. The study has laid a foundation for the application of the UV differential absorption spectroscopy in the online monitoring and fault diagnosis of SF6 insulation electrical equipment.