New dielectric coolant concepts for distribution and power transformers

Insulation systems for electrical distribution transformers are being re-evaluated based on their total life cycle cost from both an economical and an environmental perspective. Due to the inherently higher efficiency design offered by liquid cooled transformers, development has focused on fluids having improved environmental and health properties while maintaining the fire resistant properties of "less-flammable" fluids. This paper reports our findings from several years of research and development on alternative dielectric systems using both natural and synthetic esters. Because esters have lower inherent resistance to oxidation and differ significantly in the type and magnitude of oxidation by-products, a novel insulation system was developed to overcome this potential handicap. Single and three phase prototype field installations using these new dielectric coolants are discussed.