Cavity-Enhanced Raman Spectroscopy Detection Technology for Dissolved Multicomponent Gases in Insulating Oil

Dissolved gases in insulating oil (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{CO}_{2}, \mathrm{C}_{2} \mathrm{H}_{2}, \text{CO}, \text{CH}_{4}, \mathrm{C}_{2} \mathrm{H}_{6}, \mathrm{C}_{2} \mathrm{H}_{4}$</tex>, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{H}_{2}$</tex>) are key indicators of the operating state of oil-immersed power transformers. This paper explores a multicomponent gas detection method based on Raman spectroscopy and presents the development of a cavity-enhanced Raman spectroscopy detection platform. With an incident laser power of 300 mW, the laser power accumulated in the cavity reaches approximately 240 W, resulting in a power gain ratio of 800. Under the action of 60 s integration time and 1 bar pressure, the gas detection limit of the platform can reach ppm level (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{CO}_{2}$</tex> is 5.34 ppm, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{C}_{2} \mathrm{H}_{2}$</tex> is 1.05 ppm, CO is 5.94 ppm, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{CH}_{4}$</tex> is 1.92 ppm, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{C}_{2} \mathrm{H}_{6}$</tex> is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4.29 \text{ppm}, \mathrm{C}_{2} \mathrm{H}_{4}$</tex> is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2.16 \text{ppm}, \mathrm{H}_{2}$</tex> is 5.52 ppm). In this paper, Raman spectroscopy detection of dissolved gas in oil is carried out, and the influence of cavity mirror reflectivity on Raman scattering signal is studied, which proves the potential of Raman spectroscopy detection technology for transformer fault gas analysis.