High temperature operating capabilities of silicone transformer fluid

Silicone fluids appear to be well-suited to applications in higher temperature rise transformer designs; smaller, lighter-weight transformer designs; and transformers which could operate above rated capacity periodically without significant loss of insulation life. This would require a selection process to match the proper combination of insulating fluid and other insulation system components to achieve these capabilities. Much research on the thermal stability and aging characteristics has been performed with silicone fluid. Some of this work is reviewed and discussed. Thermal analysis data indicate that 50 cs, polydimethylisiloxane (PDMS) fluid is considerably more thermally stable than mineral oil. Sealed tube thermal aging studies of Kraft paper and Formvar-based enameled wire in 50 cs, PDMS fluid indicate that the life of both are similar whether aged in silicone fluid or mineral oil. The silicone fluid is affected little by either the degradation of the solid insulation materials or the thermal exposure.