This standard is a basis for the establishment of performance, limited electrical and mechanical interchangeability, and safety requirements of equipment described. It is also a basis for assistance in the proper selection of such equipment. This standard describes electrical mechanical, and safety requirements of liquid-immersed distribution and power transformers, and auto transformers and regulating transformers, single phase and polyphase, with voltage of 601 V and higher in the highest voltage winding. This standard applies to all liquid-immersed distribution, power, and regulating transformers that do not belong to the following types of apparatus: Instrument transformers; Step voltage and induction voltage regulators; Arc furnace transformers; Rectifier transformers; Specialty transformers; Grounding transformers; Mobile transformers; Mine transformers. When this standard is used on a mandatory basis, the words shall and must indicate mandatory requirements. The words should and may refer to matters that are recommended or permissive, but not mandatory. This standard is a basis for the establishment of performance, limited electrical and mechanical interchangeability, and safety requirements of the equipment covered. It is also a basis for assistance in the proper selection of such equipment. Revision Standard - Superseded. Superseded by IEEE Std C57.12.00-2006 Electrical,mechanical,and safety requirements are set forth for liquid-immersed distribution and power transformers,and autotransformers and regulating transformers; single and polyphase, with voltages of 601 V or higher in the highest voltage winding. This standard is a basis for the establishment of performance,limited electrical and mechanical interchangeability, and safety requirements of equipment described;and for assistance in the proper selection of such equipment. The requirements in this standard apply to all liquid-immersed distribution, power, and regulating transformers except the following: instrument transformers, step-voltage and induction voltage regulators, arc furnace transformers, rectifier transformers, specialty transformers, grounding transformers, mobile transformers, and mine transformers.