SubstationsSubstations are an important part of the national grid. They contain transformers which increase or decrease the voltage of an electric current. Substations are very dangerous if you try to tamper with them or vandalise them. Do not enter a substation for any reason - it is against the law and you could be electrocuted. contain devices called transformersA transformer is a device that can change the voltage associated with an electric current. One type of transformer decreases the voltage and so is called a 'step-down' transformer. A 'step up' transformer increases the voltage.. A transformer is a device used to increase or decrease voltage of electric currentElectric current is a flow of electric charges (electrons). fed into it.
Large substations
Electric current is generated with a voltage of 25,000 volts. A large substation like this one will increase the voltage to 132,000 or 400,000 volts ready for transmission across long distances. These large substations are also known as 'grid' substations.
The high voltage electric current usually leaves the grid substation on overhead linesThick electric cables that carry electricity from where it is generated to where it is used. carried high in the air on metal pylonsA tall metal tower that carries very high voltage overhead lines. - out of reach of people.
The overhead lines are fixed to the pylon with special insulatorsA material that reduces or stops the flow of electricity. made of glass and ceramics - to make sure the electric current doesn't travel down the pylon to the ground.
Small substations
On the way across the countryside, smaller substations step down the voltage to 33,000 volts for use by some factories and to supply power for trains.
Electric current generated by wind farms is usually fed into the distribution network at a lower voltage than fossil fuelCoal, oil and gas are called fossil fuels because they were formed from the remains of prehistoric plants and animals., nuclear or hydroelectric plants.
Near to places like towns and cities, the voltage is stepped down to somewhere between 11,000 and 33,000 volts for use in factories.
Pole mounted transformers
This wooden pole has a small transformer which steps the voltage down to between 230 and 450 volts for use by hospitals, factories and homes.
