Why is it desirable to transmit high votage and low current during the transmission of power?
Why is it desirable to transmit high votage and low current during the transmission of power?
To minimize losses for Joule heating, a.k.a. ohmic and resistive heating - process of heating up the conductor as electric current flows through it.
According to Joule’s first law electrical current passing through a conductor generates heat with power proportional to conductor’s electrical resistance and square of the current:
P ~ I² · R
So in order to minimize this power, which would otherwise be lost to warming up the atmosphere, you need to reduce the current. In order to still transmit the same power to the destination with lower current you need to increase the voltage as evident from the electrical power equation:
P = V · I
That is if you want to keep the power (P) the same, but lower the current (I) you have to proportionally increase voltage (V).
This is the reason why electrical companies use transformers to increase voltage at the generation site (power plant), transmit it with low thermal losses to great distances and then use transformers locally to reduce the voltage to distribute electricity to consumers. In fact they use cascades of transformers, i.e. to cover very long distances outside the cities very high voltage is used (hundreds of kilo-volts up to a Mega-volt). High voltage power lines are inconvenient in urban areas so when it reaches a city voltage is reduced to tens of kilo-volts to fan out within the city. It is then further reduced to fan out within an area/block and then down to receptacle voltage right before entering homes.
Having said that, nothing is free and there are losses associated with high voltage transmission too, e.g. corona discharge which you can look up separately. To mitigate those losses they use bundle conductors - three or four parallel wires bundled close together acting as a single wire of larger diameter
To minimize losses for Joule heating, a.k.a. ohmic and resistive heating - process of heating up the conductor as electric current flows through it.
According to Joule’s first law electrical current passing through a conductor generates heat with power proportional to conductor’s electrical resistance and square of the current:
P ~ I² · R
So in order to minimize this power, which would otherwise be lost to warming up the atmosphere, you need to reduce the current. In order to still transmit the same power to the destination with lower current you need to increase the voltage as evident from the electrical power equation:
P = V · I
That is if you want to keep the power (P) the same, but lower the current (I) you have to proportionally increase voltage (V).
This is the reason why electrical companies use transformers to increase voltage at the generation site (power plant), transmit it with low thermal losses to great distances and then use transformers locally to reduce the voltage to distribute electricity to consumers. In fact they use cascades of transformers, i.e. to cover very long distances outside the cities very high voltage is used (hundreds of kilo-volts up to a Mega-volt). High voltage power lines are inconvenient in urban areas so when it reaches a city voltage is reduced to tens of kilo-volts to fan out within the city. It is then further reduced to fan out within an area/block and then down to receptacle voltage right before entering homes.
Having said that, nothing is free and there are losses associated with high voltage transmission too, e.g. corona discharge which you can look up separately. To mitigate those losses they use bundle conductors - three or four parallel wires bundled close together acting as a single wire of larger diameter
