This International Standard covers specific characteristics of traction transformers as defined in 3.1.1, used in traction substations or along the track for the supply of power to a.c. and d.c. traction systems or to provide power to auxiliary services. Traction transformers are either – single-phase traction transformers, or – three-phase to two-phase traction transformers, or – single-, three- or poly-phase rectifier-transformers or converter-/inverter-transformers for d.c. or a.c. traction systems, or – single phase auto-transformers for traction power supply, or – single-phase booster transformers, or – single- or three-phase auxiliary transformers at traction supply voltage. Traction transformers are generally covered by the Standards of the IEC 60076 series. The requirements given in IEC 60076 apply together with the additional requirements given in this standard. Dependent on the selected technology specific parts of IEC 60076 apply: – IEC 60076-1: Oil immersed transformers – IEC 60076-11: Dry-type transformers – IEC 60076-15: Gas-filled transformers For transformers feeding contact lines through static converters IEC 61378-1 may assist, but modified or additional requirements are given in this standard. Transformers mounted on-board traction vehicles are covered by IEC 60310 and are excluded from the scope of this standard. Electromagnetic compatibility is ruled by IEC 60076-1, which states that a transformer may be considered a passive element in this respect. Some accessories, however, are subject to EMC requirements given in IEC 62236-5.