The national grid Flashcards
What is the national grid ?
giant system of cables and transformers that covers the UK and connects power stations to consumers.
The national grid transfers electrical power from anywhere on the grid
to anywhere else on the grid where it’s needed — e.g. .
homes and industry
1) Throughout the day electricity usage (the demand ) changes. Power stations have to produce enough electricity for everyone to have it when they need it
2) They can predict when the most electricity will be used though. Demand increases when people get up in the morning, come home from school or work or when its dark, cold
Popular events like a sporting final being shown on TV could also cause a peak in demand.
3)Power stations often run at well below their maximum power output , so there’s spare capacity to cope with a high demand, even if there’s an unexpected shut-down of another station.
4)Lots of smaller power stations that can start up quickly are also kept in standby just in case.
The national grid uses a high PD and a low current.
What makes the national grid an efficient way of transferring energy ?
1) To transmit the huge amount of power needed, you need either a high PD or a high current ( P=VI)
2) The problem with a high current is that you lose loads of energy as the wires heat up and energy is transferred to the thermal energy store of the surroundings
3) Its much cheaper to boost the PD up really high and keep the current as low as possible
4) For a given power, increasing the pd decreases the current, which decreases the energy lost by heating the wires and the surroundings. This makes the national grid an efficient way of transferring energy .
