SF_(6)气体中H_(2)S光声检测及FFT滤波在检测信号噪声抑制中的应用

Photoacoustic Detection of H_(2)S in SF_(6) and Application of FFT Filtering in Noise Suppression of Detected Signal

H_(2)S作为SF_(6)气体绝缘电气设备中一种重要的故障特征气体,其浓度对于评估SF_(6)气体绝缘状态有着重要意义。由于H_(2)S在近红外波段的吸收系数非常小,导致传统光学检测方法在该波段对H_(2)S气体的探测灵敏度较低。气体光声光谱技术灵敏度高、响应速度快且无需载气,非常适用于痕量气体的检测。搭建了一套大功率气体光声检测平台,选择H_(2)S气体在1578.12 nm处的吸收谱线,结合波长调制技术和二次谐波检测技术针对H_(2)S气体进行检测,并采用快速傅里叶变换(fast Fourier transform,FFT)算法对光声二次谐波信号进行频谱分析,去除残余噪声。结果表明FFT滤波技术可以有效去除光声二次谐波信号中的残余噪声,使搭建的光声检测平台对H_(2)S气体体积分数的最低检测限从10^(-6)量级降低到亚10^(-9)量级。

The concentration of H_(2)S,as an important fault characteristic gas in SF_(6) gas insulated electrical equipment,is of great significance for the evaluation of insulation status of SF_(6).The sensitivity of traditional optical detection method is rather low since the extreme small absorption coefficient of H_(2)S in the near infrared band.Gas photoacoustic spectroscopy is very suitable for trace gas detection for its high sensitivity,fast response speed and no carrier gas requirement.A set of high-power gas photoacoustic detection platform was built,and the absorption spectral line at 1578.12 nm was selected.The wavelength modulation technology and second harmonic detection technology were comprehensively adopted to detect H_(2)S gas,and FFT algorithm was used to analyze the spectrum of the second harmonic signal of photoacoustic to eliminate the residual noise.The results show that FFT filter can effectively eliminate the residual noise in the second harmonic signal of photoacoustic,so that the limit of detection of the established photoacoustic detection platform for H_(2)S is reduced from 10^(-6) level to sub 10^(-9) level.