national grid

advantages of the national grid:

• don’t need a power station in every town

• smaller number of power stations can supply the whole country

• any power station can supply electricity to any consumer

• standardised frequency and voltage

  • no adapters needed when travelling in the same country

what makes up the national grid?

transformers and pylons

what do step up transformers do?

• increase voltage

• decrease current

what do step down transformers do?

• decrease voltage

• increase current

how is electricity transmitted through cables to our homes and why?

• high voltage

  • lower current = low heat = reduce power loss

  • more efficient

what does a high current and low voltage do?

lots of thermal energy lost to the surroundings

why is the voltage of electricity reduced before it is supplied to homes?

• safety measure

  • prevent electrocution and fires

voltage of electrical cables before step-up transformer

25kV

voltage of overhead cables

132kV+

voltage of electrical cables after step-down transformer

230V

advantages of overhead electrical cables:

* less likely to hurt people
* can be placed over motorways and canals
* convenient
* easy to fix
* less expensive than underground wires

disadvantages of overhead electrical cables:

* visual pollution
* damaged by weather/low-flying planes