IEEE C57.12.20:2005

Revision Standard - Superseded.
This standard covers certain electrical, dimensional, and mechanical characteristics and safety features of single- and three-phase, 60 Hz, mineral-oil-immersed, self-cooled, overhead-type distribution transformers 500 kVA and smaller, high voltages 34 500 V and below and low voltages 7970/13 800Y V and below.

This project is a revision of an existing product standard covering certain electrical, dimensional and mechanical characteristics and safety features of single and three phase, 60 HZ, mineral oil immersed, self cooled, overhead type distribution transformers 500 kVA and smaller, High Voltages 34500 volts and below with Low Voltages 7970/13800Y volts and below.
This project is to maintain and update the subject standard which is intended for use as a basis for determining the performance, interchangeability and safety of overhead type distribution transformers and to assist in the proper selection of this equipment.