WHY USE HIGH VOLTAGES ?

The high. voltages used  to transmit electrical power around a country are dangerous. That is why the cables that carry the power are supported high above people, traffic and building on tall pylons. Sometimes the cables are buried underground, but this is much more expensive, and the cables must safely insulated. There is a good reason for using high voltages. It means that the current flowing in the cables is relatively low, and this wastes less energy. We can understand this as follows.

                                               Free photo: electrical power lines - Blue, Power, Voltage - Free ...

When a current flows in a wire or cable, some of the energy it is carrying is lost because of the cable's resistance - the cables get war,. A small current wastes less energy than a high current. Electrical engineers do everything they can do to reduce the current to half its value ( by doubling the voltage), the losses will be one-quarter of their previous value. This is because the power losses in cables are proportional to the square of the current lowing in the cables:

  • double the current gives four times the losses
  • three times the current gives nine times the losses.
 


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