This Practice provides requirements for the design and fabrication of two-winding liquid-immersed air-cooled substation power transformers. This Practice describes the requirements for design, manufacture, inspection, testing, and shipping of three-phase, two-winding, liquid-immersed air-cooled substation power transformers with a rating of 750 kVA through 10,000 kVA for use on systems 34.5 kV and below.