The research on simultaneous detection of dissolved gases in transformer oil using Raman spectroscopy

Incipient transformer faults can be effectively diagnosed by on-line monitoring of dissolved gases in transformer oil. Raman spectroscopy can simultaneously detect the type and concentration of seven kinds of characteristic dissolved gases in oil excited by a laser at one wavelength. It is a promising technique without facing the issues of aging and calibration compared to traditional gas chromatography techniques. In this paper, the principle of Raman spectroscopy is briefly introduced. The experimental platform based on the confocal micro Raman system is explained, the detection method of Raman spectroscopy for dissolved gases in transformer oil is determined and the Raman detection of seven fault gases (CO, CO₂, CH₄, C₂H₂, C₂H₄, C₂H₆ and H₂) is fundamentally realized. On this basis, characteristic Raman spectra are chosen and the corresponding molecular vibrational modes are analyzed simultaneously. To lower detection limits, a surface-enhanced Raman scattering (SERS) substrate is introduced since near-field coupling effects between adjacent Au nanoparticles decorated on SiO₂ substrate can greatly increase local electromagnetic field. The simulation results of electric field distribution are presented, all of which lay a good foundation for online monitoring of dissolved gases in transformer oil.