Inside this page:

1. Introduction to How Power Grids Work

2. The Power Plant

3. The Power Plant: Alternating Current

4. The Power Plant: Three-phase Power

5. Transmission Substation

6. The Distribution Grid

7. Distribution Bus

8. Regulator Bank

9. Taps

10. At the House

11. Safety Devices: Fuses

12. Safety Devices: Circuit Breakers

13. Lots More Information

14. See all Engineering articles

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.

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