Thermal analysis of transformers insulation based on vegetable esters

This paper presents an analysis of the thermal performance experienced by dielectric materials inside power transformers. In this case the materials studied were mineral oil, vegetable ester and kraft paper. Two basic issues on the performance of insulation systems are their cooling capacity and their degradation rate. Thus two research lines have been considered: the first one is based on the assessment of the temperature and velocity distributions of the oil in the transformer´s cooling channels, being the second aim the measurement of the degree of polymerization of the dielectric paper, a key parameter that is used to estimate the remaining life of power transformers. The first objective was approached by CFD simulations of real transformer geometries. For the second goal, a thermal aging experiment has been implemented in the laboratory. These two perspectives are closely related since high temperature accelerates aging of the dielectric system of these machines.