RT Journal Article T1 Study on the contamination rate of mineral oil in natural-ester retrofilled transformers A1 Montero, Andrés A1 García de Burgos, María Belén A1 Burgos Díaz, Juan Carlos AB The replacement of mineral oil (MO) by ester (retrofilling) is a practice used in power transformers to reduce fire and environmental risk. Although measures are taken to remove traces of oil on the paper, a certain amount of MO remains, which migrates over time. This article presents a study to evaluate the migration of MO from paper to ester using techniques such as the iodine value or the measurement of permittivity and dielectric losses. PB IEEE SN 1070-9878 YR 2023 FD 2023-08 LK https://hdl.handle.net/10016/38646 UL https://hdl.handle.net/10016/38646 LA eng NO This work was supported in part by the Spanish Research Agency under Project PID2019-107126RB-C21/AEI/10 and Project 13039/501100011033, and in part by the European Union's Horizon 2020 Research and Innovation Program under Grant 823969. DS e-Archivo RD 18 jul. 2024