A uniform method is established for determining the temperature classification for the insulation systems for dry-type power and distribution transformers by testing rather than by chemical composition. These insulation systems are intended for use in transformers covered by IEEE Std C57.12.01(TM) and IEEE Std C57.12.91(TM) as they apply to dry-type transformers whose highest voltages exceed nominal 600 V.

This test procedure for the thermal evaluation of insulation systems of dry-type power and distribution transformers is to be used for determining the temperature classification and modification of the insulation systems. This standard shall apply to all dry-type transformers with a voltage of 601 V or higher in the highest voltage winding except as follows: a) Instrument transformers b) Step- and induction-voltage regulators c) Arc-furnace transformers d) Rectifier transformers e) Specialty and general-purpose transformers f) Mine transformers g) Testing transformers h) Welding transformers

The purpose of this test procedure is to establish a uniform method for the following: a) Acquiring data used to determine the temperature classification of an insulation system b) Acquiring data that may be used as a basis for a loading guide, such as IEEE Std C57.96(TM) c) Modifying an established electrical insulation system