Actually, that problem has been solved quite nicely.

As we speak, there is a new several hundred megawatt DC transmission line between Pittsburg, Ca and a power station in San Francisco's Hunters Point District. I believe it is in service already (about 50 miles).

Even more astounding is that it rests in the mud at the bottom of the San Francisco Bay, or in the San Joaquin river bottom, the whole distance. It is a two wire system, with both water proof highly insulated wires, kept a fixed distance apart (a few feet). Magnetic disturbances could have been a problem with such a high current system, but the wires are arranged so that the magnetic field around one of the wires is canceled out by the magnetic field of the other wire. To my knowledge, that has worked well. More such transmission lines are in the works.

So it turns out that in the long run, Tesla and Edison were both right. AC power transmission as pushed by Tesla, was until very recently, eminently more practical than DC, simply because the AC could easily be transformed into extremely high voltage; which made it possible to send extreme amounts of power at much lower currents, and thus with much smaller wire. And that's the way it's been for the last hundred years.

The down side of this arrangement is a thing called skin effect, where only the outer layer of a high current wire can actually carry AC current; the inner areas being blocked by inductive effects. So the extremely high currents now needed don't do as well as they once did with the currents envisioned in Tesla's day.

DC transmission does not have that problem. Its problem was that it was not practical back then to convert DC voltage to the extremely high voltages needed for long distance transmission, and then back down again for safe local use. Rotary mechanical equipment was needed, but no DC motor commutator could possibly withstand such high voltages - not even now.

But that problem is no more, thanks to modern solid state electronics. The trick is to use solid state components to convert the AC generated at the power plant, into extremely high DC voltage. Then at the distant power substation, convert it back down to conventional medium voltage AC for distribution in the city. This now allows the whole wire cross section to conduct current. At 500,000 volts, and with the much higher current now possible; much more wattage can be stuffed through the same size wire, than with AC. And thus, Edison was also right; but available technology had to catch up, first.

OPB