Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!
Print

Science

Generating electricity

Page:

  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  1. Back
  2. Next

The National Grid

Electricity is distributed from power stations to consumers through the National Grid, which allows distant power stations to be used. It also allows a mix of different energy resources to be used efficiently to supply the country’s electricity, whatever the local demand.

Transformers

Electricity is transferred from power stations to consumers through the wires and cables of the National Grid. When a current flows through a wire some energy is lost as heat. The higher the current, the more heat is lost. To reduce these losses, the National Grid transmits electricity at a low current. This needs a high voltage.

Transformers are used in the National Grid. A transformer is an electrical device that changes the voltage of an alternating current (ac) supply, such as the mains electrical supply. A transformer that:

  • increases the voltage is called a step-up transformer
  • decreases the voltage is called a step-down transformer.

Power stations produce electricity at 25,000 V. Step-up transformers change the voltage to the very values needed to transmit electricity through the National Grid power lines. Electricity is sent through these at 400,000 V, 275,000 V or 132,000 V. This reduces energy losses during transmission but the voltages would be dangerous in homes. Step-down transformers are used locally to reduce the voltage to safe levels. The voltage of household electricity is about 230 V.

Main features

This diagram shows the main features of the National Grid.

Main features of the National Grid

Main features of the National Grid

Electricity from a power station goes to:

  1. step-up transformers
  2. high voltage transmission lines
  3. step-down transformers
  4. consumers, for example homes, factories and shops.

Page:

  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  1. Back
  2. Next

Back to Mains electricity index

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.