The Power Plant

Electrical power starts at the power plant. In almost all cases, the power plant consists of a spinning electrical generator. Something has to spin that generator -- it might be a water wheel in a hydroelectric dam, a large diesel engine or a gas turbine. But in most cases, the thing spinning the generator is a steam turbine. The steam might be created by burning coal, oil or natural gas. Or the steam may come from a nuclear reactor like this one at the Shearon Harris nuclear power plant near Raleigh, North Carolina.

No matter what it is that spins the generator, commercial electrical generators of any size generate what is called 3-phase AC power. To understand 3-phase AC power, it is helpful to understand single-phase power first.

A breakdown of the major power plants in the United States, by type

Photo courtesy U.S. Department of Energy