Fluid-thermal analysis of the cooling capacity of a commercial natural ester in a power transformer

Abstract

The low fire safety and high environmental impact of the mineral oil of the power transformers are two factors that have a negative influence in the goals of maximizing the return on investment and lowering the total costs associated with power system operation. Thus, many studies about alternative liquids (natural and synthetic esters, silicon oil) are being developed worldwide. This paper studies the cooling characteristics of a commercial natural ester in comparison with a traditional insulating mineral oil. A fluid-thermal simulation is done in a 3D-model of a partial cross-section of a single phase of a three-phase power transformer. The comparison of temperatures, velocities and dimensionless numbers (Re and Pr) of both fluids allows concluding that the direct substitution of the traditional liquid by the new one is not possible since the cooling characteristics of the latter one is quite worse than the first one.