I think the question could be constrained as "what frequency uses the minimum amount of copper to remake the electrical distribution network that exists today?"
This would be a pretty good approximation of the ratio of transmission lines to transformers.
You could build the lot with DC and massively reduce transformers, but transformers are probably a lot more reliable than switching converters everywhere. Not sure which would be cheaper tbh.
>Generally, for long-distance power transmission, DC lines can be thinner than AC lines because of the "skin effect" in AC, which concentrates current flow near the surface of the conductor, making thicker wires less efficient; therefore, for the same power transmission, a DC line can be smaller in diameter than an AC line
The issue is actually that DC voltage conversion is much harder than AC, because AC can use transformers, and DC can’t.
This is especially a problem at high voltages and currents.
Also, DC arcs don’t self extinguish as well as AC arcs do, so DC arcs are a lot more dangerous and destructive.
It’s why HVDC lines are still relatively rare (and capital expensive), and typically used for long haul or under salt water, where the inductive loss from AC would cost more than the higher capital costs required for DC voltage conversion and stability.
Cost and weight. High voltage electrical lines use aluminium because of the weight, they are mostly aerial lines. Silver is too expensive to use for almost anything.
This would be a pretty good approximation of the ratio of transmission lines to transformers.