Simultaneous Dissolved Gas Analysis in Transformer Oil via Time-Division-Multiplexed Quartz-Enhanced Photoacoustic Spectroscopy

Dissolved gas analysis (DGA) is an essential method for monitoring and diagnosing faults in oil-immersed transformers. Acetylene (C₂H₂) and methane (CH₄) are key indicator gases for fault identification. We report for the first time a time-division-multiplexed quartz-enhanced photoacoustic spectroscopy (QEPAS) sensing system capable of simultaneously and sensitively detecting dissolved C₂H₂ and CH₄, even with an extremely small amount of required sample gas. The on-beam configuration enhanced the 2<i>f</i> signal amplitude by nearly 20-fold. The sensing system achieved minimum detection limits (MDLs) of approximately 15 ppb for C₂H₂ and 0.3 ppm for CH₄, which are 2-3 orders of magnitude lower than the safety thresholds defined in the relevant industry standards. The detectability of the sensing system satisfies the requirements for DGA in transformer oil. With a gas cell volume of approximately 1.6 mL, the system markedly reduces the required oil sample volume. By integrating headspace degassing with QEPAS, the sensing system enables real-time monitoring and analysis of the oil-gas equilibrium behavior of dissolved C₂H₂ and CH₄. With its high sensitivity, rapid response, and low sample consumption, the proposed sensing system provides a viable and efficient approach for early detection of transformer faults. Furthermore, it establishes a foundation for applying QEPAS to dissolved gas analysis in transformer oil.