Cellulosic papers are the insulator of choice in oil-filled electrical power transformers. They are excellent dry state insulators with satisfactory mechanical performance at elevated temperatures, readily available at low cost, and have up to a 40-year lifespan. Normal working conditions for transformers (60 – 90 <sup>o</sup>C) can easily be exceeded during heavy power loads, which can accelerate paper insulation decomposition. Assessment of insulator condition and degradation products in the oil is difficult and has become an important research topic. Understanding the degradation of carbohydrates exposed to elevated temperatures is central to interpretation of the analytes detected in the oil. Data on the thermal degradation process of the of paper insulator hemicellulose fraction is lacking, as is how the presence of hemicellulose affects thermal degradation. Moreover, the changes of the supramolecular structure of cellulosic insulators under thermal stress had not yet been studied. We used gel permeation chromatography (GPC), gas chromatography – mass spectrometry (GC-MS), and solid-state <sup>13</sup>C nuclear magnetic resonance spectroscopy (NMR) to characterize softwood kraft paper and cotton cellulose aged by submersion in heated transformer oil. We learned that: (1) There is partial hemicellulose degradation, (2) cellulose degraded with some cross-linking and oxidation along its backbone, and (3) time-dependent- supramolecular changes of cellulose can be observed for the duration of the study. The methodology used in this study can be used to characterize aged paper.

In-depth characterization of structural changes in electrical insulation paper upon thermal stres

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.