基于太赫兹频谱的绝缘油中微量甲醇无损检测新方法  

New Nondestructive Method of Methanol Detection in Insulating Oil Based on Terahertz Spectrum

作　　者：何雨欣 杨丽君 俞华 陈奇宇 成立 廖瑞金[1] HE Yu-xin;YANG Li-jun;YU Hua;CHEN Qi-yu;CHENG Li;LIAO Rui-jin(State Key Laboratory of Power Transmission Equipment Technology,School of Electrical Engineering,Chongqing University,Chongqing 400044,China;State Grid Shanxi Electric Power Company Electric Power Research Institute,Taiyuan 030001,China)

机构地区：[1]输变电装备技术全国重点实验室(重庆大学电气工程学院),重庆400044 [2]国网山西省电力公司电力科学研究院,山西太原030001

出　　处：《光谱学与光谱分析》2024年第5期1405-1411,共7页Spectroscopy and Spectral Analysis

基　　金：国家重点研发计划项目(2021YFB2401705);国网山西省电力公司科技项目(52053022000H);重庆市自然科学基金面上项目(cstc2021jcyj-msxmX0489)资助。

摘　　要：甲醇是油纸绝缘中纤维素老化的特有标志物,目前采用的顶空气相色谱/质谱测试方法过程繁琐,无法实现无损快速检测。现有的拉曼光谱和红外光谱也难以实现低浓度甲醇(mg·L^(-1)级)的感知。利用太赫兹检测技术对极性物质的敏感性,提出了一种实现绝缘油中微量甲醇的无损检测新方法。通过采用克拉玛依25#矿物绝缘油和色谱级别的甲醇配制浓度为99、59.4、19.8、9.9、4.95、2.48、1.24、0.62、0.31和0.15 mg·L^(-1)的含甲醇的绝缘油混合溶液。检测含微量甲醇的绝缘油在太赫兹频段的吸收光谱,发现在1.7 THz左右存在特征峰,其与油中甲醇浓度有较好的定量相关关系,初步在实验室中实现了0.15 mg·L^(-1)的绝缘油中微量甲醇的测量。基于量子化学计算分析揭示了甲醇与绝缘油之间复杂的分子间力使油与甲醇分子协同振动,是太赫兹频段特征峰的机理。甲醇和绝缘油之间复杂的分子间作用力,使得两种分子在太赫兹频段产生协同振动。同时,随着甲醇浓度的增加,甲醇分子间会形成氢键,更易缔合,减少了甲醇分子与绝缘油分子缔合的比例,从而1.7 THz左右的特征峰增长速度变缓。因此,吸收峰的强度与甲醇浓度存在非线性关系。含微量甲醇的老化绝缘油的太赫兹频谱在1.7 THz左右同样出现了吸收峰,在同一甲醇浓度时,吸收峰的强度随着老化天数的增加而增加,增幅与老化程度存在非线性关系,这可能与不同时期的绝缘油裂解的产物含量有关。聚合物和绝缘油对太赫兹波的低吸收性,有机会实现变压器上绝缘油中低浓度甲醇的快速原位检测。未来将通过进一步增大光程、绝缘油老化产物与甲醇的协同振动机理分析以及自适应大数据信号提取算法来提高测试下限,并排除老化因素的影响,实现全周期绝缘油中甲醇含量的准确无损测量。Methanol is a unique aging marker of cellulose in oil-paper insulation.Headspace gas chromatography/mass spectrometry and spectrophotometry are the main methods for measuring methanol,which have a complex and long testing process.Raman spectroscopy and infrared spectroscopy also make it difficult to realize the perception of low-concentration(ppm)methanol.This paper proposes a new method for non-destructive detection of trace methanol in insulating oil by utilizing terahertz detection technology's sensitivity to polar substances.The insulating oil samples containing methanol were completed with Karamay#25 mineral insulating oil and chromatographic grade methanol.The concentrations were 99,59.4,19.8,9.9,4.95,2.48,1.24,0.62,0.31,and 0.15 ppm.Detection of the terahertz absorption spectrum showed a characteristic peak around 1.7 THz,which exhibits satisfactory quantitative correlation with methanol concentration in oil,and the minimum detection limit of 0.15 ppm trace methanol in the new insulating oil was preliminarily realized in the laboratory.Quantum chemical analysis methods can be used to study the interaction between molecules and molecules.The complex intermolecular force between methanol and the insulating oil that causes cooperative vibration between oil and methanol molecules is the mechanism of characteristic peaks in the terahertz frequency band.Meanwhile,hydrogen bonds are formed between methanol molecules for easy association.Therefore,the different association ratios of methanol molecules with different concentrations of insulating oil molecules result in a nonlinear relationship between the intensity of the absorption peak and the methanol concentration.The terahertz spectrum of aged insulating oil containing trace methanol also demonstrates an absorption peak at approximately 1.7 THz.The intensity of the absorption peak increases with the increase of aging days,and the increase is nonlinear with the degree of aging at the same methanol concentration.This finding may be related to the content of pyro

关 键 词：甲醇 太赫兹光谱 绝缘油 指纹识别 

分 类 号：TM855[电气工程—高电压与绝缘技术]