Impregnation processes of insulation rigid components of cellulose in synthetic ester and mineral oil

Although oil-immersed power transformers generally use mineral oil as insulation and cooling fluid, this liquid does not meet the new technical requirements of dielectric fluids such as high biodegradability, non-toxicity and high safety. For these reasons, natural and synthetic esters as alternative to mineral oil have increased their utilization in some transformers installations. Despite the fact that there are several works that have demonstrated the suitability of these insulation fluids from the point of view of their stability, dielectric and thermal properties, there are very few works focused on the study of the effects of these liquids on impregnation process. The aim of this work is provide information about the behavior of different rigid insulation materials, not studied until now, during the impregnation process in a synthetic ester compared with a mineral oil.