Читать книгу Alternative Liquid Dielectrics for High Voltage Transformer Insulation Systems - Группа авторов - Страница 58

The alteration of the chemical assembly of the oil can be studied using the nuclear magnetic resonance (NMR) study. In the NMR spectrum, multiplets are observed for CH₃, CH₂, and allylic protons of the fatty acid fragments in the section of 0.87–2.78 ppm, for both the oil samples, as seen in Figure 2.11. In the range of 4.12–5.35 ppm, two multiplets are identified meant for the CH₂ and CH protons of the glycerol moiety. The existence of methyl ester group is established at 2.3 ppm. The peak that represents the chloroform solvent for both the oils is observed at 7.28 ppm, and this is considered the reference peak [74]. The NMR spectroscopy shows if there are any changes in the structure of the samples over a long duration. However, no significant difference is observed for the oil spectra of NEOs after accelerated aging hours.

Figure 2.11 NMR analysis of (a) new FR3, (b) aged FR3 for 2000 hours, (c) new JAT, and (d) aged JAT for 2000 hours.

Source: Baruah et al. [73] / with permission of IEEE.