1. This part of the Specifications describes the power transformer to be furnished under the Proposal. The transformers must be provided with the features and in accordance with these Specifications, as well drawings and other data attached to these specifications. 2. The transformers must be outdoor, mineral oil filled, three-phase, 60 hertz. Cooling class, self-cooled (ONAN) with single forced air cooling (ONAN/ONAF) with two stages of forced air cooling (ONAF/ONAF). The transformer must have the following continuous capacity with 55/65 degrees C temperature rise. a. Primary (138 kV) and secondary (7.557/13.09 kV) windings, 15/20/25/28 MVA, at 55/65 degrees C, (ONAN/ONAF/ONAF), for continuous operation at 3,300 feet altitude.
