A fully biodegradable dielectric fluid based on high oleic acid vegetable oil has been developed for use in electrical equipment. The development of such a fluid for use in equipment such as electrical transformers has naturally caused it to be compared to more conventional mineral oil based insulating fluids and to high-temperature hydrocarbons and silicones for which specifications already exist. The selection of the base oil and its modifications relied heavily on preexisting standards such as ASTM D 3487 and ASTM D 5222. Because such a vegetable based fluid in practical terms does not completely match any of these fluids exactly in its characteristics, commercial implementation may lead to a desire for a standard specification describing its unique set of properties.
In addition, the biodegradable nature of the fluid has required that standard tests not used in the electrical industry, such as CEC L-33-A-94, developed for two-stroke-cycle outboard engine oils, be applied to the material in question. ASTM has subsequently developed a standard guide, ASTM D 6006 for hydraulic fluids, but relatively little work was performed on dielectric fluids at the time of the development of the biodegradable fluid discussed in this paper. Comparisons with other potential tests will be discussed and a discussion of the relative merits of these tests for dielectric fluids will be presented.