Cargill, Inc.

Vegetable Oil Dielectric Insulating Fluid for High-Voltage Transformers

Innovation and Benefits: High-voltage electric transformers require an insulating fluid to prevent short circuiting and provide cooling. Polychlorinated biphenyls (PCBs) were used as transformer fluids until they were banned in the 1970s, and mineral oil became the primary replacement. Unfortunately, mineral oil is flammable and may be toxic to fish. Cargill has developed a vegetable-oil-based transformer fluid that is much less flammable, provides superior performance, is less toxic, and has a substantially lower carbon footprint.

Summary of Technology: High-voltage electric transformers must be filled with an insulating fluid that absorbs heat and prevents short-circuiting. For many years, most transformers were filled with polychlorinated biphenyls (PCBs) or, especially after PCBs were banned, petroleum-based mineral oil. While mineral oil is significantly less hazardous than PCBs, it is quite flammable and may be toxic to aquatic species. Furthermore, mineral oil is very hydrophobic, so any water in the system is taken up by the solid insulating material inside the transformer, usually cellulose (wood, paper, or cardboard). Cellulose degrades when exposed to water and the operating temperatures of a typical transformer. The service interval for transformers is largely dependent on the operational life of the solid cellulose insulators, so preventing the degradation of those insulators can significantly extend the service life of the transformer.

Cargill has developed Envirotemp^TM FR3^TM dielectric fluid based on vegetable oil instead of petroleum. These biobased oils can be used in replacement of mineral oil for retrofilling transformers. If used in newly designed transformers, the transformers can be made smaller owing to better thermal performance of Cargill’s oils. The FR3^TM fluid is significantly less flammable than mineral oil, greatly reducing the risk of fire or explosion. Cargill’s oils also increase the service life of the cellulose insulation by 5-8 times longer than mineral oil thus extending the insulation life as well as the transformer life.

According to a lifecycle assessment using BEES^® 4.0, a transformer using FR3^TM fluid has a lower carbon footprint across the entire life-cycle of a transformer, with the largest reductions occurring in the raw materials, manufacturing, and transportation phases. The total carbon foot print of an electric transformer is about 55-times lower when using FR3^TM fluid compared to mineral oil. This is all in addition to the low toxicity, high biodegradability, and the fact that FR3^TM fluids are based on a renewable resource. Furthermore, there have been no known explosions or fires in the hundreds of thousands of transformers filled with FR3^TM fluid since the product launched.

FR3^TM fluid has achieved numerous industry validations including EPA's Environmental Technology Verification, the lowest environmental impact performance score in a BEES lifecycle assessment, USDA Bio-based Product certification, and certification as a less flammable fluid by both Underwriters Laboratory (UL) and Factory Mutual Research Corporation.

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