Modify an existing standard to a Guide and expand its scope for improved application of the procedures for thermal evaluation of resin cast transformers. Provide alternate procedures/guidelines for the thermal evaluation of resin cast transformers to allow more practical and more rapid testing and evaluation by manufacturers and to result in a thermal classification system of this equipment by transformer users. Revision Standard - Superseded. A uniform method is established for determining the temperature classification of solid- cast and resin-encapsulated power and distribution transformer insulation systems by testing rather than by chemical composition. These insulation systems are intended for use in transformers covered by IEEE Std C57.12.01-1989 and IEEE Std C57.12.91-1995 as they apply to solid- cast and resin-encapsulated transformers whose highest voltages exceed nominal 600 V.