The national grid is a massive system of cables and transformers within the UK. It is useful for transporting electricity across the country, carrying it from power stations (power plants) to homes, factories and businesses that require it.
Power stations/plants produce electricity at high currents. When transmitting electricity over long distances, the current will experience great resistance. This leads to a high current heating the wires, which causes energy loss in the form of thermal energy.
Let’s look at the equation P = V × I (Power = Voltage × Current). We can increase the voltage and decrease the current at the same ratio, which will keep the power the same. So, we can transmit the same amount of power while using a smaller current. This decreases the energy loss and is also much cheaper.
A transformer is an electrical device that changes the potential difference (voltage) of an alternating current supply. We use transformers in transmission lines.
A basic transformer consists of two coils of wire, which are not connected together. These coils are wrapped around an iron core.
In the national grid:
Step-up transformers increase the voltage and decrease the current as the electricity leaves the power station. They have more turns of wire on the secondary coil than on the primary coil.
Step-down transformers decrease the voltage and increase the current as the electricity reaches homes, factories or businesses. They have fewer turns of wire on the secondary coil than on the primary coil.