In studying of losses in power systems, often spoken that power loss decrease is proportional to the inverse square of system voltage increase. For example, if the voltage is doubled, the losses will be a quarter. It should be noted that this conclusion is correct only when that after increasing the line voltage (and so reducing the line current) conductor cross section remains the same as previous. But this assumption is unreasonable and unwise, because conductor cross section must be chosen based on current amount.

It is a well known relationship that conductor cross-section and the energy loss is proportional to the square of the current. So, if we assume that the correct conductor cross sections is chosen, the following conclusions can be found (in the case of system voltage increasing) :

1 -Because the conductor cross section will reduce proportional to the current decreasing, the costs of conductors purchasing will reduce also. Instead, the cost of the conductors insulating will increase with voltages increasing.

2 – With assuming that the conductor cross section is chosen based on nominal current, then the loss will be proportional to the voltage inverse (instead of the inverse square of voltage).

For example, with doubling of the line voltage, conductor cross-section and the energy loss are both reduced approximately to half (there are other parameters that complicate heat transfer conditions and so we say conductor cross section approximately will reduce to half).