High-sensitivity photoacoustic carbon monoxide detection based on mid-infrared laser

As the operating time of the transformer increases, the large molecules of the insulating cardboard will crack and produce carbon monoxide (CO) gas due to overheating or discharge fault. In order to achieve high-precision detection of CO, a detection technology for dissolved CO in transformer oil based on a non-resonant photoacoustic (PA) cell with small volume was proposed. In the mid infrared band, CO has a stronger absorption of light, which is shown in the absorption spectrum of CO. A CO detection system based on laser absorption photoacoustic spectroscopy (LAPAS) was established, an interband cascade laser (ICL) was chosen to excite PA wave. The performance of the system is evaluated through experiments. The minimum detection limit (MDL) of the system for CO reaches 73 ppb with an averaging time of 30 s. The system detection indicators comply with the concentration limits for dissolved key gases specified in the IEEE guideline. This scheme has a good application prospect in the direction of dissolved CO detection.