This standard defines the terminal markings and connections for distribution@ power@ and regulating transformers covered in the IEEE C57 series of standards@ guides@ and recommended practices. Purpose The standard provides a consistent method for terminal markings and connections for single-phase and three-phase distribution@ power@ and regulating transformers. It designates terminal markings for interchangeability showing the sequence@ external terminations@ neutral terminations@ grounded terminations@ and marking of full and tap winding terminations. It also puts forth the connections of singlephase transformers in various configurations and describes the angular displacement of three-phase transformers when connected to various system phase displacements.