Correlation between stabilizer consumption and degree of polymerization of thermally upgraded paper aged in insulating natural ester and insulating mineral oil

Insulating paper holds significant importance in the insulation system of power transformers, and thus, its degradation is the subject of many studies. A successful evaluation of the degradation rate of such paper contributes to reducing downtime and avoiding equipment failure. In this work, samples of thermally upgraded paper were thermally aged in insulating natural ester (INE) and insulating mineral oil (IMO) and were evaluated by degree of polymerization (DP) and FTIR-ATR. It was possible to identify characteristic bands of dicyandiamide, an inhibitory compound of the thermal degradation of the paper, and to establish a correlation between the decrease in DP and the consumption of dicyandiamide during aging, which was observed to develop in three distinct steps for both IMO and INE.