I run (4) 8 ft ground rods in a row about 10 ft apart under the fence near the charger. Then a single hot wire. Use ceramic insulators (rather than plastic) at the corners and ends. Use a couple shutoff switches in the line and a lightning choke arrester (with its own separate ground rod) near where the charger feeds the system so if lightning strikes the fence or nearby it doesn't fry your charger.

I went through two chargers before I figured out I needed lightning chokes.

What Galaxy is describing is usually used in dryland areas on a high-tensile fence where one or more of the 5 or 6 wires are hot and one or more of the rest are grounded in places. This completes the circuit when the ground may be too dry to carry the pulse back to the ground rods.

I have a couple areas where the fence wire is over 1/2 mi away from the charge and ground rods and have not had a problem at any time of year getting a good pop from the fence. Depends where you are and what type of fence you are running. If you use a good hot charger (around 9 kv on the fence and around 6 joules of energy stored) in most areas you will not need anything but a good ground system near the charger.

A very good reference on setting up an electric fence system is the Gallagher fencing manual here . Note especially the section on grounding.

Good luck

Jim at Dawn