Degradation behavior of epoxy in stator insulation of large generators in service for 23 years based on infrared spectrometric analysis

作者：Hao, Yanpeng; Xie, Hengkun

来源：Transactions of China Electrotechnical Society, 2008, 23(3): 19-23.

• Degradation behavior
• Epoxy
• Infrared spectrometric analysis
• Methyl group
• Nitroso composites

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&middotNO or&middotNO2 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.

• 出版日期2008-3
• 单位华南理工大学