It has the status of a horizontal standard in accordance with IEC Guide 108.
IEC 60050-421 Ed. 1.0 t:1990
Original price was: $278.00.$139.00Current price is: $139.00.
International Electrotechnical Vocabulary (IEV) – Part 421: Power transformers and reactors
International Electrotechnical Commission , 10/15/1990