How do high-voltage power lines work?

The electricity in your fan was made hundreds of kilometres away, seconds ago. A power station makes three-phase AC at about 21 kV. A transformer lifts it to 400 or 765 kV for the long trip across the country, and substations step it down to 220, 33 and 11 kV.

Read how it works: How do high-voltage power lines work? · The history of high-voltage power lines · More boxes on Glassbox

Chapters in this interactive model

1. From power station to your plug: Up to 400 kV for the long trip, then down in steps to 230 V at your socket.
2. Why the voltage is so high: Same power, higher voltage, smaller current: and the heat lost falls with the square.
3. Anatomy of a pylon: Steel lattice, glass insulators, aluminium wires with a steel heart, and wires that sag on hot days.
4. Why three wires, and when DC wins: Three waves a third of a cycle apart add up to zero. For very long distances, direct current is cheaper.
5. The grid is one giant machine: Every generator in India spins in step at 50 Hz. Frequency shows, second by second, whether supply matches demand.
6. Fields, hum and staying safe: Why birds can perch on a live wire, why a kite string can kill, and what the fields below really are.