The National Grid

Click on the picture to get it to a bigger size.

On this diagram, A is a step up transformer at the power station.

• A step up transformer increases the voltage (potential difference).
• At the same time the current is reduced.
• Current is responsible for heating up wires and wasting energy.
• So reducing the current reduces the energy wasted by heat.

Near your house there is step down transformer C that decreases the voltage ( and increases the current). The reason is that the massive voltage could give a fatal electric shock.

The National Grid is the system of power stations and power lines. It means that each town no longer has to have its own power station. Clearly there are economies of scale.

PS B is an intermediate step down transformer. There's one for every town that reduces the voltage from 400,000V to 33,000V before it is sent to the local substations to be reduced to 230V for your house.