How the National Grid Works

🧲 How the National Grid Works

The National Grid is the network of cables that distributes electrical power across the UK. It works through a series of voltage changes (see the interactive diagram above):

1. Power station generates electricity at about 25,000 V (25 kV)
2. Step-up transformer increases voltage to 275,000 V or 400,000 V for long-distance transmission
3. Transmission cables (on pylons) carry power across the country at high voltage, low current
4. Grid substation (step-down) reduces to 33,000 V for heavy industry
5. Local substation (step-down) reduces to 11,000 V then to 230 V for homes

Why High Voltage for Transmission?

The equation P = I²R shows that power wasted in the cables depends on current squared. If you halve the current, you quarter the power loss. The National Grid transmits at very high voltage (and therefore very low current) to minimise this wastage. A cable that would lose 50% of the power at low voltage loses less than 2% at 400,000 V.