Vegetable-Oil-Based Dielectric Coolants

Electrical transformer insulation systems are evaluated based on economic, safety, and environmental standpoints using total life cycle analysis. Because of the inherent high efficiency of liquid-cooled transformer designs, new developments focus on improving the environmental and safety properties of fire resistant (less-flammable, high fire point) fluids. This article reports the latest findings on dielectric systems using natural ester (vegetable oil) fluids. Because esters naturally have lower oxidation resistance than mineral oils, a novel blend of base oils and additives were developed to overcome this potential handicap. Single- and three-phase prototype field installations using these new dielectric coolants are discussed.