Quantitative detection of C6F12O/CO2 gas mixture based on UV differential absorption spectrometry combined with variational mode decomposition

C
₆
F
₁₂
O gas mixture is potential to be used in low and medium voltage switchgear equipment due to its excellent insulation properties. It is essential to investigate the detection method of trace C
₆
F
₁₂
O for the leakage monitoring and maintenance of the equipment. In this paper, a quantitative method for the detection of trace C
₆
F
₁₂
O (0.02%~0.125%) is proposed based on ultraviolet (UV) spectral detection technology. The variational mode decomposition (VMD) optimized by the sparrow seeking algorithm (SSA) is chosen to remove the noise in the UV spectrum to improve the detection accuracy and is compared with the conventional wavelet transform and the ensemble empirical mode decomposition (EEMD). It is found that the UV absorption spectra of C
₆
F
₁₂
O gas has the absorption peak in the 220 nm~365 nm band, with the peak at 306 nm; the optimized VMD is better than wavelet transform and EEMD in noise reduction, with a maximum signal-to-noise ratio (SNR) of 30.12 dB and a minimum root-mean-square error (RMSE) of 0.0025; the UV differential spectra of trace C
₆
F
₁₂
O processed by optimized VMD have an inversion curve fitting coefficient as high as 0.99983, with the error of detection less than 0.004% and the lower detection limit as low as 0.02%. The related research results can provide a reference for the application of UV spectral detection technology to the trace detection of C
₆
F
₁₂
O /CO
₂
gas mixture in insulation equipment.