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 (C 2 H 2 ) and methane (CH 4 ) 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 C 2 H 2 and CH 4, even with an extremely small amount of required sample gas. The on-beam configuration enhanced the 2 f signal amplitude by nearly 20-fold. The sensing system achieved minimum detection limits (MDLs) of approximately 15 ppb for C 2 H 2 and 0.3 ppm for CH 4, 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 C 2 H 2 and CH 4 . 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.