"Years ago," Jack began, "a new office building was being constructed. The electrical team, eager to save time and materials, decided to use a smaller earth cable than what was specified in the design. They thought, 'What's the worst that could happen?'"
The primary job of an earth cable is to provide a low-resistance path for fault current to flow back to the source. This surge in current forces the circuit breaker to trip or the fuse to blow almost instantly, disconnecting the power and making the fault safe. earth cable size
If calculation is impractical, standards provide minimum earth cable sizes based on the live conductor size: "Years ago," Jack began, "a new office building
Electricians use two primary methods to determine the correct size according to regulations (such as BS 7671 in the UK): A. The Selection Method (The Table Method) This surge in current forces the circuit breaker
There is a dangerous misconception that because the earth doesn't carry current under normal conditions, it can be small. Remember: the earth cable must carry more current than the live cable, but for a much shorter time. It faces the toughest test during a fault.
A thick enough wire ensures that the resistance is low enough to draw a massive amount of current instantly, which "trips" the fuse or breaker.
As it turned out, the smaller earth cable was not able to handle the fault current that occurred during a short circuit. The cable overheated, causing a fire that spread quickly through the building. Luckily, no one was hurt, but the damage was extensive.