This data sheet describes the requirements for two-winding liquid-immersed air-cooled substation power transformers 34.5 kV and below, 500 kVA through 15,000 kVA, as discussed in ELSTR01 - Design and Fabrication of Liquid-Immersed Substation Power Transformers 34.5 kV and below, 500 kVA through 15,000 kVA.