Vegetable oils

Only recently have transformer-grade vegetable oils become available. The first commercial product was BIOTEMP®, patented in the U.S. in September 1999 by ABB and developed at its Raleigh, NC-based transformer lab. The base fluid was high oleic oil with over 80 percent oleic content. These oils are produced mostly from seeds that have been developed by selective breeding; more recently, gene manipulation techniques have been used. Partial hydrogenation is an added step that may be used to minimize the very unstable triunsaturates. The high mono- unsaturate oils are in demand in the food and lubrication industries. The BIOTEMP® fluid, also from high oleic oils, is now used in some distribution and network transformers in critical areas. Another U.S. patent was issued later, in September 1999, for a transformer oil from regular soybean oil, obtained by Waverly Light & Power in Iowa, though this product is not yet commercially used. It is not a high oleic oil. In March 2000, another U.S. patent was granted to Cooper Industries, Inc in Milwaukee, WI under the trademark Envirotemp FR3®. This fluid also is from standard-grade oleic base oils, and is used commercially in some distribution transformers. A second patent was issued to the ABB inventors on the BIOTEMP® fluid in August 2001. Figure 1 shows typical oil seeds used from which oils are extracted and processed for transformer use. Fluid development details are not available except for the BIOTEMP®

fluid, for which a dozen technical papers have been published. Commercial brochures are available for the BIOTEMP® and Envirotemp FR3® fluids.