Significant differences exist in the thermal aging mechanisms and byproducts between vegetable oil-paper insulation and mineral oil-paper insulation systems. Consequently

conventional aging characteristic parameters developed for mineral oil-paper systems cannot be directly applied to assess the thermal aging state of vegetable oil-paper insulation. To extract novel characteristic parameters suitable for evaluating the thermal aging of vegetable oil-paper insulation

this study conducted accelerated thermal aging experiments on vegetable oil-paper insulation systems. Three-dimensional fluorescence spectroscopy was employed to investigate the fluorescence characteristics of suspended cellulose fibers in vegetable oil during thermal aging

revealing a progressive enhancement in fluorescence peak intensity accompanied by red-shift phenomena. Quantum chemical calculations were adopted to further analyze the changes in frontier molecular orbital energies and electronic transitions of cellulose fibers before and after esterification during thermal aging. These calculations demonstrated that esterification reactions between cellulose and various acids served as the primary microscopic mechanism which drived the fluorescence spectral changes observed in suspended cellulose fibers. Finally

through fingerprint characteristic model analysis of the three-dimensional fluorescence spectral data from suspended cellulose fibers in vegetable oil

an exponential correlation between fingerprint characteristic parameters and the degree of polymerization was established

with the goodness-of-fit of the exponential model exceeding 0.92. This research provides a novel methodology for aging assessment of vegetable oil-paper insulation systems.