CH4和C2H2是变压器发生故障时两种重要的特征气体。为了实现对变压器中溶解的微量CH4和C2H2气体含量检测的需求, 采用激光光声光谱气体检测技术, 通过分析CH4和C2H2气体的近红外吸收谱线, 选取合适的激光光源并确定激光调制参数; 设计并搭建了一套以双激光光源和非共振光声池为核心的光声光谱微量CH4和C2H2气体检测系统, 获得了系统对CH4和C2H2气体检测灵敏度和低含量检测误差。结果表明, CH4和C2H2气体分别在体积分数为0～1000×10-6和0～500×10-6的范围内具有良好的线性响应, 每10-6体积分数的检测响应度分别为5.8969μV和16.1831μV; 在低含量CH4/C2H2混合气体对系统的重复性和精度测试中, CH4气体体积分数为3.00×10-6时的检测最大绝对误差为0.30×10-6, C2H2气体体积分数为0.50×10-6时的检测最大绝对误差为0.20×10-6。此研究结果满足测量误差的技术指标要求, 实现了对微量CH4和C2H2气体的高灵敏度检测。

Methane and acetylene are the most important characteristic gases when the transformer breaks down. In order to meet the demand for detecting the concentration of the trace CH4 and C2H2 dissolved in the transformer, the laser photoacoustic spectroscopy gas detection technology was adopted. By analyzing the near-infrared absorption spectrum of CH4 and C2H2 gas, the appropriate laser light source was selected and the laser modulation parameters were determined. A set of photoacoustic spectroscopy trace CH4 and C2H2 gas detection system with dual laser light source and a non-resonant photoacoustic cell were designed, and the detection sensitivity and low concentration detection error of the system for CH4 and C2H2 gas was obtained. The result shows that CH4 and C2H2 have good response linearity in the volume fraction range of 0~1000×10-6 and 0~500×10-6, respectively, and the responsivities are 5.8969μV and 16.1831μV per 10-6 volume fraction, respectively. The system is tested for repeatability and accuracy using low-content CH4/C2H2 mixed gas. The maximum absolute error of detection is 0.30×10-6 when the CH4 volume fraction is 3.00×10-6, and the maximum absolute error of detection is 0.20×10-6 when the C2H2 volume fraction of 0.50×10-6. The research results meet the technical index requirements of measurement error and achieve high-sensitivity detection of trace CH4 and C2H2.