The power grid

A power grid is many generators and many users tied into one shared electrical network, so that power made anywhere on it can be used anywhere else on it. Its trick is voltage. Electricity is generated at moderate voltage, stepped up by transformers to tens or hundreds of thousands of volts for the cross-country lines — high voltage means low current, and low current means little lost heating the wires — then stepped back down near the user. The current is three-phase alternating current: three separate AC supplies staggered a third of a cycle apart, carried on three wires, which delivers steady power and spins motors smoothly with no extra machinery.

Before long-distance transmission, you had to generate electricity roughly where you used it, which chained cities to nearby fuel and left the energy in a remote waterfall stranded. The grid broke that link. A dam in the mountains or a plant at a distant coal seam could now feed a city hundreds of kilometres away, and many stations could back each other up on a common network, so a fault or a peak in one place could be covered from another. It is the reason electricity became a utility you simply expect from the wall, rather than a local luxury.

The grid is the nervous system of industrial civilization — a continent-spanning network into which hydro dams, coal and gas plants, nuclear stations, and later wind farms and solar arrays all pour their power, and from which every home, factory, hospital, and computer draws. Once electricity could travel, industry no longer had to huddle at the energy source; light, machinery, and eventually the entire electrified economy spread wherever the wires reached. The three humming wires on the pylons marching across the landscape are the direct heirs of the line from Lauffen to Frankfurt.