The Power Grid. Image credit source.co.zw

The Power Grid. Image credit source.co.zw

ZIMSEC O Level Combined Science Notes: Transmission of electricity

  • At Hwange, Kariba, Munyati and other places AC power is generated
  • This is because the most efficient power generators produce AC power
  • In addition to that AC power can be stepped up and down using transformers
  • Direct Current cannot be stepped up or down using transformers
  • Electrical energy is generated at 4 000 V (4kV)
  • It is stepped up to 132 000 kV
  • It is then fed into the network of power lines which cover the entire country
  • This is network is also known as the National Grid
  • It is operated by ZETDC (which is part of ZESA)
  • When it reaches its destination it is stepped down to 240V
  • At substations readying it for domestic use
  • Some industries and mines have their own substations
  • These substations also step down the supply from the overhead national grid cables to various voltages
  • These voltages vary from industry to industry depending with their intended useage
  • Electricity is transmitted at higher voltages
  • As this allows thinner wires to be used
  • Thinner wires are cheaper compared to the very thick wires that would be otherwise required
  • The national grid allows electricity to be generated at advantageous locations
  • For example at Hwange where there is plenty of coal
  • At Kariba where there is plenty of water in the Kariba Dam
  • Or by using molasses in the low-veld

To access more topics go to the Combined Science Notes page.


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