Specifications include, but are not limited to: The transformer shall be designed and constructed for operation on a 115kV three-phase, 60 hertz, effectively grounded system, at the following usual service conditions: · A maximum ambient temperature of +104°F (40°C) to -4°F (-20°C) · An altitude below 3,300 feet (1000 meters) · A medium pollution level 2. VOLTAGE RATINGS 2.1. HIGH VOLTAGE (PRIMARY) The high-voltage winding (HV) is to be Delta connected, rated at 115,000 volts (nominal). 2.2. LOW VOLTAGE (SECONDARY) The low-voltage winding (XV) is to be Wye-connected with fully insulated neutral brought out, rated at 13,200 or 14,400 volts, as specified per item. 3. MVA RATINGS The three-phase minimum output ratings of the windings at a maximum of 65°C rise over ambient are as follows: Item # Minimum Output Ratings 1, 2 15/20/25MVA ONAN/ONAF/ONAF 3, 4 24/32/40MVA ONAN/ONAF/ONAF 5 10/12.5MVA ONAN/ONAF Transformers shall be capable of delivering full rated MVA at all HV tap positions. 4. IMPEDANCE The impedance between the high-voltage and the low-voltage winding at the self-cooled rating shall be as listed below. The impedances of all like transformers manufactured under this contract shall vary less than 7.5 percent of each other to facilitate parallel operation Item # Impedance Ratings (at rated voltage, 85°C ref at ONAN rating). 1, 2 7% min- 8.5% max 3, 4 8% min- 9.5% max 5 7% min – 8.5% max
