The main reason that power utilities prefer three-phase transmission to any other number of phases is as follows:
For a fixed amount of power to be transmitted a fixed distance at a fixed line loss with a fixed voltage between conductors, three-phase is more economical in the use of conductor metal than any other number of phases.
However it should be noted that when a fixed amount of power is transmitted a fixed distance with a fixed loss for the same voltage to neutral, there is no difference between any system of phases regarding the required amount of conductor metal.
The above information was obtained from the book "Alternating-Current Circuits" by Kerchner and Corcoran where proofs are given.
The main reason that power utilities prefer three-phase transmission to any other number of phases is as follows:
For a fixed amount of power to be transmitted a fixed distance at a fixed line loss with a fixed voltage between conductors, three-phase is more economical in the use of conductor metal than any other number of phases.
However it should be noted that when a fixed amount of power is transmitted a fixed distance with a fixed loss for the same voltage to neutral, there is no difference between any system of phases regarding the required amount of conductor metal.
The above information was obtained from the book "Alternating-Current Circuits" by Kerchner and Corcoran where proofs are given.
