Historical
IEEE Std C57.12.40-2006
IEEE Standard Requirements for Secondary Network Transformers, Subway and Vault Types (Liquid Immersed)
This Standard was originally a NEMA/ANSI Standard last published as ANSI C57.12.40-2000. This standard is intended for use as a basis for establishing the performance, interchangeability, and safety of the equipment covered and to assist in the proper selection of such equipment.
Institute of Electrical and Electronics Engineers [ieee]