Electronic – 1kV DC Circuit – Insulation on ground wire

Yes it is possible, but only really as a extension to radio if you don't want to consider systems that use a implied second conductor, like the earth.

Radio works, so you can use the single wire to greatly decrease the loss between transmitter and receiver. With radio propagating thru space, the power per area falls off with the square of the distance to the transmitter. The falloff with a wire is quite different, with modest distances yielding less loss. The loss in a wire is exponential due to ever-increasing resistance, so eventually radio actually wins over wire.

You can also have what appears to be a single wire system by implicitly using some nearby large conductor, like the earth, as the other "wire". Some old commercial power distribution systems worked this way, with the earth carrying the return currents. If you can send power this way, you can also send information this way. However, no such power systems are being built new, and I think all the old ones have been phased out and replaced with full out and back wires.

Where is that quote from? It is self-contradictory, and pretty much just plain wrong.

Current will flow if a load is connected between a generic power supply positive and negative, no ground connection is needed, unless you have some special purpose power supply.

A ground connection is often used for safety, especially in line non-isolated supplies, or as a means to reduce noise. Even so, not all supplies pass the ground on to the output terminals or even make it available (for common examples, think wall-warts and such with just a two pole output). Many supplies don't even have an incoming ground terminal from the mains (small switchers, and again, wall-warts).

I was going to post this as a comment, but it seemed to cover the question.

Edit as per comment below and corrected text.

Well, that does change things. Generally, a DC power supply has no output tied to ground, or connected to the supply electrically at all, so connecting a load between an output and earth ground would result in no current flow. Supplies that have an output set of terminals and a separate ground can often be configured (by jumping ground to one of the output terminals) as positive ground or negative ground if desired.