Power transmission for long distance is carried out at:

Power transmission for long distance is carried out at high voltage due to following reasons

Advantages of high transmission voltage:

1. Reduces the volume of conductor material

The volume of conductor material required is inversely proportional to the square of transmission voltage and power factor. The greater the transmission voltage, the lesser is the conductor material required. Hence, the transmission at high voltages is economical.

We know that \(P = VIcos\phi \)

\(\Rightarrow I = \frac{P}{{Vcos\phi }}\)

Power loss \(P = {I^2}R = {I^2}\left( {\frac{{\rho l}}{a}} \right)\)

\(\Rightarrow a = {I^2}\left( {\frac{{\rho l}}{P}} \right)\)

\(\Rightarrow a = {\left( {\frac{P}{{Vcos\phi }}} \right)^2}\frac{{\rho l}}{P}\)

\(\Rightarrow a \propto \frac{1}{{{{\left( {Vcos\phi } \right)}^2}}}\)

\(\Rightarrow volume \propto \frac{1}{{{{\left( {Vcos\phi } \right)}^2}}}\)

So that for higher transmission voltage of the order of 110 kV, thinner conductor is required.

2. Increases transmission efficiency

Transmission efficiency increases when the line voltage is increased.

3. Decreases percentage line drop

Percentage line drop decreases when the transmission voltage increases.

Important Points:

Limitations of high transmission voltage:

1. The increased cost of insulating the conductors
2. The increased cost of transformers, switch-gear and other terminal apparatus.