Insulation systems for liquid filled transformers

Liquid dielectrics have been successfully used for many years for the major insulation system impregnate for transformer applications above 10-25 KV operating levels. Extensive use of liquid insulants is based primarily on their ability to satisfy the prime design requirements of low cost, long service life with a minimum of maintenance, good dielectric, thermal properties and compatibility with other materials. Not all insulating fluids meet these individual requirements to the same degree, therefore, the selection of a particular liquid solid system should represent the best compromise in these desired properties.