Highly sensitive multi-pass cavity enhanced Raman spectroscopy with novel polarization filtering for quantitative measurement of SF6 decomposed components in gas-insulated power equipment

The decomposed components analysis (DCA) is highly valued for potential faults diagnosis in SF6 gas-insulated power equipment (GIE). The current method and technology for effective online monitoring of these components are still lacking. Here, we present a novel multi-pass cavity enhanced Raman spectroscopy (MPC-CERS) as a promising analytical tool to detect SF6 decomposed products. A rear reflector is applied that provides a gain factor of 2.24 for Raman signal intensity and a gain factor of 1.7 for signal-to-noise ratio (SNR) compared to the traditional MPC approach, and a polarizer is installed to suppress the fluorescence background noise by a factor of 0.72. The limits of detection (LODs) at extremely low-ppm levels are achieved for SF6, SO2F2, COS, CF4, SO2, CO2, and CO, and the quantification performance for multi-gases is investigated with a maximum accuracy error < 7.3% as well as a long-term instability of 0.28%. These results pave a promising way for MPC-CERS methodology to be applied in fault diagnosis of SF6-GIE in the future.