Electrical Power Supply And Distribution Book

Electrical power systems

Electrical power systems can be composed of the following:

1. Subtransmission lines to main substations;
2. Distribution lines to distribution substations;
3. Utilization lines to distribution transformers; and
4. Generators to provide emergency, stand-by, and/or prime power for mission essential/critical loads.

Generally, for Army base-wide distribution changeouts, the preferred CONUS voltage is 13.2 kV or 13.8 kV three-phase, three-wire, with delta primary and wye secondary transformer connections. When extending existing distribution systems, the preferred distribution voltage is the same as the existing distribution voltage.

For Air Force, the preferred CONUS distribution is 12,470Y/7,200 volt, three-phase, with delta primary and wye secondary transformer connections. Voltages for facilities outside of the United States are specified in AFM 86-3.