Glossary
Electricity, explained plainly
Short answers to the questions people actually ask.
Installation
Cable cross-section
The cross-sectional area of one conductor in square millimetres. It sets how much current the cable may carry, and therefore which breaker goes in front of it.
ReadConsumer unit
The enclosure where the supply from the meter is split into circuits and where all the protection sits: main switch, RCD and breakers, in that order from left to right.
ReadSchuko socket
Type F, known as Schuko: two round pins and two earthing clips on the sides. It takes the same plug as Germany, Austria, the Netherlands and most of continental Europe.
ReadSingle-phase and three-phase
Single-phase is one live and neutral at 230 V, which covers almost everything in a flat. Three-phase is three lives with 400 V between them, needed for a cooker, larger motors and workshops.
ReadProtection
Circuit breaker
The cable in the wall, not the appliance. It cuts the circuit when more current flows through it than the cable can carry without overheating.
ReadEarthing
It gives fault current a path into the ground instead of through a person. It is the only protection that works the moment an appliance casing becomes live.
ReadRCD (residual current device)
A device in the consumer unit that cuts the supply when it detects current leaking to earth. It is the only protection that reacts when current passes through a person.
ReadShort circuit
Live and neutral touching directly, with no appliance between them. Current jumps to hundreds of amps and the cable overheats instantly, so protection must disconnect at once.
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