How to estimate cellulose condition in insulation transformers papers? Combined chromatographic and spectroscopic study.

This study focuses on the temporal stability of insulation paper used in power transformers and intends to provide reliable and comprehensive estimators for the assessment of paper degradation state. To achieve the objectives artificially aged model papers were investigated along with power transformers insulation papers, by means of Size Exclusion Chromatography (SEC), Fourier-Transform Infrared Spectroscopy (FT-IR), ultraviolet–visible (UV–Vis) reflectance spectroscopy. The results of the UV–Vis analysis were compared to quantum chemical calculations performed by using time-dependent-Density Functional Theory method. The selection of methods allows the assessment of paper degradation state by characterization of depolymerisation progress and development of carbonyl groups. Our results not only are aimed to collect a data basis for paper condition assessment but also to increase the understanding of the mechanism of cellulose degradation in terms of relationship between aging conditions, different degradation paths and its observed effects. • Insulation paper degradation (oxidation and DP changes) described with use of spectroscopic and chromatographic techniques. • Concentration of chromophores in cellulose calculated from the UV–Vis spectra analysed by TDDFT simulations. • Transformer samples described by higher amount of conjugated diketones on C(2) and C(3) atoms than the aged model papers. • Two-indicator OI FTIR and DP approach is superior to one degradation indicator. [ABSTRACT FROM AUTHOR]