红外光谱法研究运行23年大电机定子绝缘中环氧的老化机理  

Degradation Behavior of Epoxy in Stator Insulation of Large Generators in Service for 23 Years Based on Infrared Spectrometric Analysis

作　　者：郝艳捧[1] 谢恒堃[2] 

机构地区：[1]华南理工大学电力学院,广州510640 [2]西安交通大学电力设备电气绝缘国家重点实验室,西安710049

出　　处：《电工技术学报》2008年第3期19-23,共5页Transactions of China Electrotechnical Society

基　　金：教育部全国百篇优秀博士论文作者专项基金(200541);西安交通大学电力设备电气绝缘国家重点实验室开放基金资助项目

摘　　要：对300MW/18kV发电机备用的和运行23年的定子线棒绝缘进行了红外光谱实验研究。实验比较了三种取样法,即直接取一层绝缘、用溶剂分离玻璃纤维布取环氧云母粘合层、刮取绝缘成分做溴化钾压片,发现只有后者能得到绝缘在低波数段的红外吸收峰。结果表明,老化线棒绝缘厚度一半部位的绝缘其环氧有未老化和老化两种状态,未老化环氧较少;接近导体部位的绝缘其环氧老化最严重。最后探讨了环氧的老化过程,环氧支链发生氧化反应生成酸,该老化反应比较普遍;环氧支链被局部放电产生的·NO或·NO2氧化生成了亚硝基化合物,该老化反应极少地发生在接近导体部位的绝缘。Fourier transform infrared （FTIR） spectrometer is used to analyze the microscopic changes of epoxy in stator insulation cut from a standby and an aged stator bar in operation for 23 years in a 300MW/18kV generator. Three sampling methods were tested, such as taking one layer of the laminated insulation, one layer of the epoxy adhesive with mica powders through separating glass fiber cloth by solvent, and a pressed KBr disc by scraping insulation into powders. Only with the last method the infrared spectrum in low wave-number rang can be obtained. Three conditions, still unaged and already aged epoxy are found in the insulation located half thickness, and the severe aged near the conductor of the aged bar. At last, the degradation behavior of epoxy in the stator insulation is discussed. Two types of chemical changes take place here. One is that the methyl group of epoxy is attacked, forming acid, which is prevalent. The other is that · NO or · NO2 resulted from partial discharges, which occur rarely on the insulation near the conductor of stator bar, attack the methyl group of epoxy, forming nitroso composites.

关 键 词：定子线棒 环氧云母绝缘 老化过程 红外光谱分析 

分 类 号：TM215.92[一般工业技术—材料科学与工程]