Simultaneous Detection of Hydrogen and Acetylene Using a Photoacoustic Gas Sensor Based on Frequency Tracking and WMS-2 <i>f</i> Technique

Insulating materials in high-voltage electrical equipment are subject to decomposition during the early stages of faults, with the release of characteristic gases such as hydrogen (H₂) and acetylene (C₂H₂). However, the current gas detection methods suffer from issues like cross-sensitivity, compactness, and reliability. This paper proposes a photoacoustic spectroscopy (PAS) gas sensor based on a single DFB laser for the simultaneous detection of H₂ and C₂H₂. Specifically, C₂H₂ serves both as a pump gas for assisting H₂ detection and as the target gas itself. Gas detection is implemented by tracking frequency shift caused by changes in sound velocity and extracting harmonic component generated by infrared absorption. By investigating the attenuation effect of H₂ gas on PA signals, a calibration model is established, correlating C₂H₂ concentration with the harmonic peak under different H₂ concentrations. Through Allan deviation analysis, the system achieved minimum detection limits (MDLs) of 96 ppm for H₂ at 5.6 s integration time and 0.73 ppb for C₂H₂ at 894 s. The developed system enables integrated gas analysis in hydrogen-rich environments, showing practical potential for in situ monitoring in power systems.