This standard is applicable to three-phase and single-phase power transformers (including auto-transformers).
Where corresponding standards do not exist for small and special transformers (such as single-phase transformers with rated capacity less than 1kVA and three-phase transformers less than 5kVA, instrument transformers, convertor transformers, traction transformers for electric locomotive, testing transformer and welding transformer), this standard may be referred to.
