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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.

The National Grid ensures a reliable supply of electricity.

If one power station breaks down, the grid will continue to supply electricity from other power stations in the grid.

The National Grid also responds to the demand for electricity – supplying more at peak times.

Main features

The diagram below shows the main features of the National Grid.

The higher the current in a cable, the greater the heat loss to the surroundings.

This means that high currents waste more energy than low currents.

Why use high voltage?

When a transformer steps up voltage, current is stepped down.

A step up transformer at the power station steps up the voltage and consequently steps down the current.

This means that the current flowing in the overhead cables is relatively small and can be distributed long distances across country.

Transmitting small current greatly reduces heat lost in the cables, which in turn reduces the number of power stations needed.

Northern Ireland has just three major electricity generating stations: Ballylumford Power Station, Islandmagee, County Antrim (gas fired); Coolkeeragh Power Station, Derry/Londonderry (oil fired); and Kilroot Power Station, Carrickfergus, County Antrim (dual coal/oil fired).

The main features of the Grid are:

• Power station which generates electricity at 25,000 V.
• A step-up transformer beside the power station to step-up the voltage and consequently step-down the current reducing electrical energy wasted as heat energy in the overhead cables. Electricity is sent through these at 400,000 V.
• A step-down transformer close to domestic consumers to step the voltage down to 230 V for safe use in the home.