FTIR被动遥测信噪比优化及在变电站SF6泄漏检测应用

被动FTIR红外遥测技术可应用于气体泄漏检测，气体检测下限与仪器信噪比密切相关。仪器信噪比与测量参数有关，如光谱分辨率、采样频率、积分时间、平均次数等，如何结合实际应用优化参数组合以实现最佳信噪比，目前还缺少系统分析。针对这一问题，从理论上分析了这些参数与信噪比关系，并归类为三个方面：（1）光谱分辨率，引用了Roland Harig给出的结论，当光谱分辨率低于特征峰半高全宽时，信噪比不变，但为了避免背景气体的交叉干扰，分辨率不宜设置过低，需要结合实际应用综合考虑；（2）降低采样频率能够减少计算量，缩小光谱范围，但采样频率和光谱范围与信噪比无关；（3）在积分时间和光谱平均次数方面，同样时间条件下，多次干涉图采集会引入零光程差的采样误差，使得噪声大于理论计算值，因而长积分时间获得信噪比优于多次平均。开展了六氟化硫（SF₆）泄漏检测实验，根据SF₆特征峰宽度选择4 cm-1分辨率，20 kHz采样频率兼顾了信噪比和检测时间，并利用FTIR巡检系统发现变电站泄漏点，证明了方法的有效性。

Optimization of FTIR Passive Remote Sensing Signal-to-Noise Ratio and Its Application in SF6 Leak Detection in Transform Substation

Passive FTIR infrared remote sensing technology is useful in gas leak detection.The detection limit of trace gas is related to the instrument’s signal-to-noise ratio(SNR).The instrumental SNR is related to measurement parameters,such as spectral resolution,sampling frequency,integration time,and average times.How to optimize the combination of parameters to achieve the best signal-to-noise ratio in combination with actual applications currently lacks system analysis.This paper the oretically analyzes the relationship between these parameters and SNR and categorizes them into three aspects:(1)In terms of spectral resolution,the conclusion,cited from Roland Harig,is that SNR stays the same when the spectral resolution is lower than the full width at half maximum(FWHM),but in order to avoid interference of background gases,the resolution mustavoid too low and is appropriately set in practical application;(2)In terms of the sampling frequency,sampling frequency reduction can reduce calculation cost and narrow the spectral range,but the sampling frequency and spectral range are not related with SNR;(3)In terms of integration time and multiple spectra averaging,under the same time conditions,multiple interferogram acquisitions will introduce a sampling error in zero path difference,making the noise larger than the theoretical calculation,so SNR obtained by long integration time is better than multiple averaging.Conducted sulfur hexafluoride(SF₆)leak detection experiment,the 4 cm^-1 resolution is selected according to SF6 spectral feature,and 20 kHz sampling frequency is selected by taking into account SNR and detection time,and FTIR inspection system is used to locate the leakage point in the transform substation,which proves the effectiveness of this method.