The AM Forum

http://en.wikipedia.org/wiki/Single-wire_earth_return

 ???   :o  ???  ::)  ???  :o  ???

I guess it's doable if you have really conductive soil, but I wouldnt trust it to carry much current reliably.

If you notice in long run setups and distribution runs, the grounded neutral is also ran along with one of the primary wires, thus providing the ground / neutral return.

Some years back, after a nasty thunderstorm a friend of mine that lived at a shore home called me to come down and "see whats wrong with my power". His lights were dim and flickering up and down in brightness. A little poking aroung with a meter to his neutral ground and an incoming water pipe showed wild voltage swings. A call to the local power company found that a lightning hit had caused a high resistance connection from his neutral off of the pole (he had his own pole pig as he was the end of a run) to the main grid neutral. this intermittant connection on the primary side was causing his problem.

So I guess this blows that theory right out of the water unless, maybe you live in the middle of a salt marsh.  ???  ???

System deployed by the Gotham Power Co?

How fast does electricity travel through dirt?  They are talking hundreds of miles in some cases with a dirt return. Just how conductive is 240 miles of dirt?

They use this @ high voltage. The main resistance is where the GND rods meet the earth. Claim is a pair of rods through a short earth has similar resistance to a pair through a long path. I saw this done near where I live a few years ago and couldn't believe my eyes. Later the run was changed to 3 phase with the usual GND.

That's strange when a 'grounding company' will drive a rod or pipe down 100 feet.
Fred

Good question, but you're looking at the concept incorrectly.

You need to consider the resistance of the ground rod to earth. The National Electric Code expects a resistance of 25 ohms or less using a single ground rod.

OK. If you assume a load of 10 KW off of a 14 KV power line, the AC current drawn is 700 mA. Not even an amp. If the ground rod return is 25 ohms to earth, the voltage drop is only about 17 volts, less than 1/10 of 1%.

As far as the 250 mile distance goes, the earth itself has negligible resistance, it's the resistance of the ground electrodes *to* the earth that counts. Heck, the center of the earth is a ball of metallic iron and nickel.

What would really stink with a 1-wire power feed is what happens in the event of a lightning strike!


250.56 Resistance of Ground Rod Electrode.
When the resistance of a single ground rod is over 25 ohms, an additional electrode is required to augment the ground rod electrode, and it must be installed not less than 6 ft away.

Hum please run the clothes dryer tonight I need some worms for our fishing trip