Here’s how you can check:
Disconnect power from your fence energizer.
Place the fence under heavy load by “shorting” the fence as follows:
At a location on the fence at least 100 yards from the energizer, lean 3 or 4 steel stakes or unpainted T-posts against the “hot” wire of the fence. (Alternatively, some people have found a successful method is to push several pieces of fence wire into the earth and wrap the opposite ends around the hot wire)
Plug the fence energizer in and check the fence line voltage with a digital voltmeter. You want to see that the voltage has dropped below 2,000V due to shorting the fence. On some high-powered fence energizers, you may not be able to short the fence below 2,000V. However, you can still test them at a higher voltage.
Continue to short the fence by leaning steel posts or by making wire connections to ground at 100 yards distance or more from energizer until the fence line voltage drops below 2,000V.
You are now ready to test the energizer ground system. Connect one lead of the digital voltmeter to a 12-inch metal stake driven into the ground 3 feet away from the last fence energizer ground rod. Connect the second lead to the ground rod furthest from the energizer. The voltage reading should ideally be zero or no more than 200V.
If the digital voltmeter reading is under 200V, your ground system is adequate, and you will get near maximum performance from your electric fence energizer.
If the reading is above 200V, then your ground system needs improvement.
