Earthing and Testing

What is an Earth System?

An earth system is the most important component of any electric fence system. If an electric fence is not properly grounded, it will be much less effective.
An earth system consists of a number of earth rods (stakes) that pass electric current back from the soil to the energizer. The larger the energizer and the longer the fence line, the more earth rods are required.

 

How does earthing work?

For an electric fence to give an animal an electric shock, electrical current (produced by the energizer) must complete a circuit. The current from the energizer flows along the wires, through the animal’s body, down through the soil to the earth system, then back up to the energizer. If the earth system isn't working properly, the animal won't get an effective shock.

 

What factors will affect the Earth System?

Dry, sandy and non-conductive soil types limit the current flow to the earth rods. If you have soil that is not well suited to earthing, use additional earth rods, choose a better location for the earth system, or use an alternate method of earthing such as earth/ground wire return.
Vegetation touching the live fence wires allows current to leak, causing the fence to “short” and voltage to drop. Check the fence regularly to make sure that long grass and overhanging branches are not touching the live fence wire.
Using a mixture of metals in the earth system will lead to electrolysis. This may cause the parts of the earth system to disintegrate in a short period of time. For example, never use copper wire with galvanised earth rods.

 

Choosing the Right Earth System

Earth Systems - All Live

An all live earth system is recommended where soil is conductive (most moist soils are conductive). When an animal standing on the soil touches the fence, the circuit is completed and the animal gets a shock.

 

Earth Systems - Earth/Ground Wire Return

A earth wire return system is recommended where soil is not conductive (most dry or sandy soils are not conductive). The fence is constructed using both live and ground wires. When an animal touches a live and a earth wire at the same time, the circuit is completed and the animal gets a shock.

 

Selecting a Site for the Earth System

A suitable place for the earth system is:

  • At least 10 m (33 ft) away from any other earth system (i.e. telephone, house power line, etc.)
  • Away from livestock or other traffic that could interfere with the installation
  • Where the system can easily be accessed for maintenance
  • Ideally, where there is damp soil all year round (i.e., a shaded area or under the drip line of a building).

NOTE: If it is not possible to locate the earth system in close proximity to the energizer, you may be able to use the existing fence line to connect to a remote earth system. In dry weather, it may be necessary to water the earth system in order to improve soil conductivity.

 

Setting up an Earth System

Earth Rods

The number of earth rods required depends on the type of energizer being used to power the fence and soil condition. Refer to information supplied with your energizer for the correct number of earth rods to use.

To insert the earth rods:

  1. Space the required number of 2 m (6 ft) earth rods at least 3 m (10 ft) apart.
  2. Drive the earth rods deeply into the soil, at least 3 m (10 ft) apart. Make sure that the earth rods protrude out of the soil at least 10 cm (4 in) so they can be easily connected
  3. Join the earth rods in a series using earth clamps and underground cable.

Testing the Earth System

  1. Turn off the energizer.
  2. At least 100 m (330 ft) away from the energizer, short circuit the fence by laying several steel rods (or lengths of pipe) against the fence. In dry or sandy soils, drive the rods up to 30 cm (12 in) into the soil.
  3. Turn on the energizer.
  4. Use a digital voltmeter to measure the fence voltage. It should read 2 kV or less. If not, repeat step 1 to 3.
  5. To check the earth system, attach the voltmeter’s clip to the last earth rod and insert the earth probe into the soil at the full extent of the lead. The voltmeter reading should be no more than 0.3 kV. If the reading is higher than this, the earth system is insufficient. See the earthing checklist, add more earth rods, or find a better location for your earth system.

Earthing Checklist

Check your earth system to make sure:

  • All wires are joined securely
  • Connections to earth rods are secure
  • Earth rods are at least 2 m (6 ft) long and at least 3 m (10 ft) apart
  • There are a sufficient number of earth rods.
  • All parts of the earth system are made of the same metal
  • Earth rods are buried deeply in the soil.