C57.12.70-2011 - IEEE Standard for Standard Terminal Markings and Connections for Distribution and Power Transformers
Description: Standard terminal markings and connections are described for single-phase and three phase distribution, power, and regulating transformers. For terminal markings, it covers sequence designation, external terminal designation, neutral terminal designation, grounded terminal designation, and marking of full and tap winding terminals. Additive and subtractive polarity and parallel transformer operation are described. Connections of single-phase transformers in various configurations and angular displacement of three-phase transformers to connect to various system phase displacements are covered.