What electrical quantities must be kept small to transmit electric energy economically over long distance?

Answer 1

Transmission energy loss is mainly (but not solely) resistive. The resistive loss is I squared times R where I is the current in amperes and R is the loop resistance in ohms. So to minimize loss, we want to minimize loop resistance and minimize current. To minimize current for any required amount of power, we must maximize voltage. This is why very high voltages are used to transmit electricity over long distances. To minimize resistance we must use more copper (assuming copper wires - the traditional wire material). This increases initial cost for the larger diameter wire and the heftier towers to carry the additional wire weight.

In summary, raise voltage to lower current and raise wire diameter to lower resistance.

Commercial power use is so large that reactive losses must be included. Reactive current may not show up as power in the reactive components, but the reactive current suffers the same I squared R losses that resistive current suffers. Reactive current is due to both load reactance and transmission line reactance.