Terahertz Time Domain Spectroscopy of Transformer Insulation Paper after Thermal Aging Intervals

• Published in: Materials Vol. 11; no. 11; p. 2124
• Main Authors: Wang, Liang, Tang, Chao, Zhu, Shiping, Zhou, Shengling
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI 29.10.2018; MDPI AG
• Subjects: DFT; molecular dynamics simulation; novel diagnostic technique; terahertz-time-domain spectroscopy; transformer insulation paper; terahertz-time-domain spectroscopy; transformer insulation paper; DFT; novel diagnostic technique; molecular dynamics simulation
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma11112124

An accelerated thermal aging process was used to simulate the condition of paper insulation in transformer oil-paper systems. Optical parameters of the insulation paper after various aging intervals were analyzed with terahertz time-domain spectroscopy (THz-TDS) over the range 0.1~1.8 THz. The result shows that the paper had seven absorption peaks at 0.19, 0.49, 0.82, 1.19, 1.43, 1.53, and 1.74 THz, and density functional theory of B3LYP/6-311G+ (d, p) was used to simulate the molecular dynamics of the repeating component (cellobiose) of the cellulose paper. Theoretical spectra were consistent with experiment, which had absorption peaks at 0.18, 0.82, 1.47, and 1.53 THz in the same frequency range. At the same time, the paper samples after various aging intervals had different refractive indexes, and least squares fitting revealed a linear relationship between the degree of polymerization and the refractive index of the paper. Hence, this paper demonstrates that THz-TDS could be used to analyze the aging condition of transformer insulation paper and provides the theoretical and experimental basis for detection.