This standard describes the terminal markings and connections for distribution and power transformers covered in American National Standards C57.12.00, C57.12.01, C57.12.10, C57.12.20, C57.12.21, C57.12.22, C57.12.23 C57.12.24, C57.12.25, C257.12.26, C57.12.30, and C57.12.40.

This standard does not describe terminal markings and connections of rectifier transformers; these are described in American National Standard Requirements, Terminology, and Test Code for Pool-Cathode Mercury-Arc Rectifier Transformers, ANSI C57.18-1964 (R1971).