Understanding the properties and aging characteristics of natural esters for applications in fluid filled electrical apparatus

Fluid filled electrical apparatus have utilized the conventional cellulose and mineral oil combination as the main insulation system since the early development of the transformer. This paper will review the properties of the natural ester fluid and its application to fluid filled electrical apparatus. We will review the advantages of the fluid and investigate the comparison to conventional mineral oil. Because of the chemical structure of esters, they have lower inherent resistance to oxidation and differ significantly in the type and magnitude of the oxidation by-products. This paper will focus on the long term performance of the natural ester fluid and how that performance and the aging characteristics of the natural ester differ from conventional mineral oil. We will investigate the fluid parameters as well as the other key components of the system. Included will be the aging data from performance studies over extended time frames for both conventional mineral oil and natural ester fluid.