An electric fence works because the animals receive an unpleasant but harmless electric shock when touching the conductive material. This only happens because the circuit is completed by the contact of the animal with the fence. In this moment, the current flows from the fence energizer through the conductive material and the animal into the ground and back to the device. A strong grounding is therefore vitally important for the fence to work reliably.
In the following, we give you several tips for the grounding of your electric fence.
The Nature of the Ground
Again, a little more detailed: Since the fence energizer is connected to the fence and the ground, there is a tension between fence and ground. When an animal standing on the ground touches the fence, the circuit is closed and the current flows through the animal and the earth back to the device.
The lower the resistance, the better the current flows. The ground can present a very high resistance and thus impair the function of the pasture fence because the current can not flow back sufficiently to the fence device.
The purpose of the grounding is therefore to minimize the resistance of the soil. This can be achieved more easily through good earth-conductivity, several grounding rods, and careful connection of the grounding rods, both to each other and with the energizer.
The conductivity of the earth is improved by moisture. Dry soil is not suitable for grounding. In the case of rather dry soil, the resistance of the earth can be reduced by the use of additional grounding rods and/or by driving the rods deeper into the ground.
The Grounding Rods
The grounding rods are made of stainless, galvanized steel and should be at least one meter long. They are driven deep into the earth until they hit moist soil, at least 1 m deep. If several rods are used, the distance between them must be at least 3 m. They are then connected underground in series with a high voltage cable. The first grounding rod is connected to the grounding connection of the fence energizer.
The impulse energy also plays a role when considering the number of grounding rods. For 1 Joule electric fences, a grounding rod with a length of 1 m is usually sufficient. For fence energizers with 2 to 5 Joules, at least 2 to 3 grounding rods with a length of 1 m should be used.
And do not forget to keep at least 10 m distance from other grounding systems. Otherwise, a surplus of the voltage may occur.
In case your grounding does not work properly, you can troubleshoot with the help of this check list.
Due to grounding, electric fences are perfect lightening conductors. This is why fences are often struck by lightening. The immense voltage of the lightening may destroy the fence energizer so that a) the fence does not work properly anymore and you may have to catch your animals and b) you have to buy a new fence energizer. It is even worse if the energizer is connected to a socket. The lightning strike goes directly into the socket and can trigger a domestic fire. (The legally required residual current circuit breaker prevents this.)
To prevent this from happening, build a lightning protection device between the fence and the fence energizer and also connect it to the grounding. Since current always finds the path of least resistance, the lightning is removed from the "extra resistance" lightning device into the ground before reaching the pasture station. Phew — danger avoided.
The Fence Switch
In case you use a fence switch to stop the fence in the event of an impending thunderstorm, you must also connect it to the ground. The fence switch then directs the flash into the ground before it hits the lightning protection device. Check after a lightning strike whether lightning protection and fence switches are still functional and exchange them if necessary.
There is even more to learn about electric fences in our free fence guidebook: