Relative properties of the new combustion resistant vegetable oil based dielectric coolants

Electrical distribution transformers insulation systems are being re-evaluated based on their total life cycle from economical, safety and environmental perspectives. 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 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 than conventional mineral oil, 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.