national grid

• The NATIONAL GRID

  A large network consisting of CABLES & TRANSFORMERS

  • It connects POWER STATIONS to CONSUMERS, distributing electricity across the country.

  
• The NATIONAL GRID operates using a HIGH POTENTIAL DIFFERENCE & a low CURRENT to transmit electricity efficiently.

  • A high CURRENT would lead to a significant amount of energy being LOST as HEAT in the cables
  • it's avoided by using a HIGH POTENTIAL DIFFERENCE to allow for a LOW CURRENT
  • It reduces ENERGY LOSS & prevents the wires from heating up too much, making the grid more efficient.

  
• TRANSFORMERS

  used to change the POTENTIAL DIFFERENCE for efficient energy transmission over long distances.
• The two types of transformers:

  • STEP-UP TRANSFORMERS
  • STEP-DOWN TRANSFORMERS
• STEP-UP TRANSFORMERS:

  These INCREASE the POTENTIAL difference & decrease the current to reduce thermal energy transfer from transmission cables to surroundings to increase the efficiency of power transmission.
•  STEP-DOWN TRANSFORMERS:

  These decrease the POTENTIAL DIFFERENCE & INCREASE the CURRENT, so it's safer for consumers.

  • high voltages are dangerous & would blow the appliances in our houses
• • The electricity generated from the POWER STATION goes through a STEP-UP transformer
  • It's to INCREASE the p.d. to around 400000 volts & decrease the current, so it can travel long distances & minimise ENERGY LOST as HEAT
  • the wires then transmit the electricity all across the country between huge pylons, before it hits its destination like a town
  • Then it passes through a STEP-DOWN transformer to decrease the p.d. & increase the current.
  • This is done so that it's at a SAFE LEVEL for the consumer to use (230V & 50Hz).

  
• Label the photo:

  • power station
  • step-up transformer
  • national grid
  • step-down transformer
  • consumer

  
• Transformers are made up of two coils of wire:

  • PRIMARY coils
  • SECONDARY coils

  around a magnetic iron core
• The POWER transferred by a transformer is almost equal in the primary & secondary coils.
• • A: cables
  • B: step-down transformer

  
• Fossil fuel & nuclear power stations work by generating thermal energy.

  • This is used to turn water into steam which can then rise & turn turbines.
  • The kinetic energy of the moving turbines can be converted to electrical energy
  • which is finally sent out across the national grid