What happens if you don't ground an electric fence?
Earthing is most probably the most important component of an electric fence system. Most of electric fence problems arise due to poor earthing.
For an electric fence to be effective, the circut needs to be completed. When an intruder or animal touches the fence, the circut is completed through the ground or the earth wires, The current flows via the earth back to the energiser.
How an Electric Fence works ?
An electric fences work by shocking intruders or animals with a short, sharp, powerful, yet safe shock that is sufficient to deter them.
When an animal or person makes contact between the live wire of the fence and the ground, the circuit is completed and a shock received.
An electric fence system is made up of 3 components
- Earthing system
All of these components must be working properly for the whole system to function. When the three components of an electric fence are linked together, a circuit is created through which current will flow.
The bird receives no shock as the circuit is not closed.
Where do earth spikes go on electric fence?
Always follow these basic rules when earthing an electric fence.
- The first 3 earth spikes should be as close to the energiser unit as possible.
- Important not to place closer than 10 meters from the mains earth.
- Then an earth spike should be placed along the fence at least every 30 meters
Wiring a security electric fence ?
The fence must be wired in an alternative positive negative series wiring pattern to maximize detection and shock.
How many earth spikes do I need for electric fence?
- Use at least 3 earthy spikes, each at least 1.2 long
- Drive the ground rod at least 1.2 meters apart and completely in the ground
- Connect the initial 3 earth spikes together using a single length of insulated under the gate HT cable.
- To avoid electrolysis make sure like metal types are used when joining
- Install in moist or damp soil whenever possible
- Install earth spikes at least 2 meters away from;
- any mains supply
- other earth spikes
- underground telephone cables
- power cables
- water pipes
- HT cable from the fence to the earth spikes must be in conduit
- Following the initial three earth spikes, earth spikes need to be installed at least every 30 meters in an urban area.
- Agricultural fences should have an earth spike at least every 100 meters after the initial three earth spikes.
Testing the earthing of a electric fence
A poor or inefficient earthing system will restrict the flow of electrons or current around the electric fence circuit. On a clean well-insulated fence there is very little current flow.
So in order to test the earth, it is necessary to create a current flow to make a short or leakage path
- Bring the fence voltage down to 2kv or less by placing several steel stakes between the live wire of the fence and the ground, at least 100 meters away from the earth system
- Drive a galvanized earth stake at least a meter into the ground and at least a meter away from this nearest earth spike of the fence. Then using a digital volt meter, measure the voltage between this earth peg and the nearest earth spike attached to the energizer earth system.
- Ideally, there should be no reading on the voltmeter. A reading of up to 200 volts, provided the fence is shortened to below 2000 volts is acceptable.
- If the reading is above 200 volts. Increase the number and quality of the earth spikes on the electric fence
The don'ts of earthing
- Connect 2 or more energisers to the same earth spikes
- Don’t connect HT cable to earth spikes with unlike metal types, which cause electrolysis and break the wire connection.
- Connect to Eskom or Telkom earthing stakes.
- Connect to a water main pipe
- It is possible to trip over them
- Use stakes less than 1.2 meter long
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