激光诱导击穿光谱技术定量分析SF_6中的痕量O

六氟化硫(SF_6)气体因其优良的绝缘和灭弧性能,被广泛应用于高压绝缘设备中。然而,当存在H_2O和O_2等杂质时,SF_6气体在局部放电等作用下分解成的低氟化物会进一步与杂质发生反应生成稳定的氟硫氧化物和氢化物,使得设备绝缘性能下降,危害电网安全,因此检测和分析SF_6中微水、微氧及其分解产物具有重要意义。采用激光诱导击穿光谱技术测量了SF_6中的痕量O含量。利用CaF2作为窗口材料,解决了窗口材料在不断腐蚀作用下引起的激发能量逐渐衰减以及窗口材料与SF_6气体击穿产物反应引入的污染影响测量结果的问题,消除了由激发条件改变引起的等离子体状态的变化;通过测量不同O含量的SF_6气体激光诱导击穿光谱,结合迭代小波分析对实测光谱进行基线校正和降噪处理,通过定标曲线获得了O元素检测限为38ppm。利用偏最小二乘法建立了稳定的定量分析模型,改善了定量分析模型的稳定性和精度。

Quantitative Analysis of Trace O Concentration in SF6 with Laser-Induced Breakdown Spectroscopy

Sulfur hexafluoride (SF6 ) is widely used in gas-insulated high-voltage equipments due to its excellent insulation and arc extinguishing performance .However ,when impurities such as trace water and oxygen are present in SF6 ,the by-products , which are formed due to equipment faults and partial discharge ,can react with these impuriti to form stable sulfur oxyfluorides . The equipment insulation performance can be degraded significantly by those stable sulfur oxyfluorides ,causing threat to the safety of the power system .The detection and analysis of the impurities such as water ,oxygen and decompositions in SF6 are therefore of great importance .In this paper ,laser-induced breakdown spectroscopy is employed to measure trace O in SF6 .CaF2 is used as window material to solve the degradation of the excitation energy caused by the corrosion of the window material by SF6 decompositions ,to eliminate the pollution problem caused by the reaction between the window material and the breakdown products of SF6 gas ,and to reduce the change of plasma state caused by the change of excitation condition .By correcting the spectral baseline with an iterative wavelet transform and suppressing the noise with a wavelet transform with soft thresholding ,a limit of detection of 38ppm is achieved from the experimental calibration curve .Furthermore ,a quantitative model based on partial least squares (PLS) is developed to achieve better stability and precision .