Earthing an energiser - part 2

Surveys show that 80% of fence systems do not have an adequate earth system.

4 wire earth return system.

Figure 4.8 - 4 wire earth return system

Dry soil conditions

In dry, low mineral soils with poor earthing, eg. sandy, pumice or volcanic ash soils, use the Super Earth Kit (available from RD1).

Note: In drought conditions it may be necessary to water the earthing system.

Main causes of a poor earth are:

  • Rusty or corroded earth stakes
  • Broken earth wire connecting the stakes
  • Not enough earth stakes
  • Stakes too close together or too short
  • Poor connections at the stakes or in the connecting wire

Test the earth (ground) system

This needs to be done once a short section of fence has been built. It should be tested at least once a year or at the height of any dry period to ensure the earthing capacity is sufficient for the joule rating of the energiser.

Short the fence out at least 100m (330ft) away from the earth system by using several steel stakes between the live wires and the ground. Reduce the fence voltage at this point to 2000V (2kV) or less.

Using a Digital Volt Meter (DVM), measure the voltage between the wire connecting through the earth stakes to the energiser earth terminal and an independent earth stake. This stake should be a galvanised metal rod, minimum 200mm (8") long, and placed 1m (3ft) away from the earth rods or as far away as your DVM cable will reach (see Figure 4.9).

Note: If you are using a SmartPower energiser the earth monitor/alarm will indicate when the earth system requires attention).

There should be no reading on the DVM, however up to 200V (0.2kV) is acceptable. If the voltage is higher than this, switch off the energiser, drive in more earth stakes at the recommended spacings and connect them to the existing earth system until the voltage is down to the acceptable level.

Test the earth (ground) system

Testing an earth (ground) return wire

Install a standard length earth stake (2m) as close as possible to the end of the fence. Create an earth between a live wire and the earth wire. Choose the location for the earth stake in a damp area if possible. If you cannot find a damp area, the earth test may be unreliable.

Using a DVM measure:

1. The voltage between the live wire and the earth wire, (i.e. across the load just installed).

Testing an earth (ground) return wire - step 1

Figure 4.10(a)

2. The voltage between the live wire and the independent earth stake, leaving the load in place.

Testing an earth (ground) return wire - step 2

Figure 4.10(b)

Earth return wire performance

If the second voltage reading exceeds the first by more than 1000V (1kV) check the earth return wire for loose connections. Finally connect the independent earth stake to the earth return wire as a permanent connection. Extra earth stakes can be installed at various places around the fencing system and connected to the earth return wire to improve earth performance.

System performance

If the first voltage reading is less than 3kV, your fence system is at risk of poor animal control. Assuming that your earth wire return checked out satisfactorily, check that the fence live wire has good connections. If connections are good, it is possible that your energiser is too small for your fence system. Assess your total length of fence or farm size against the energiser selection charts.

Information supplied by Gallagher from the Gallagher Power Fence Systems Manual available at your local RD1 store. Pick up your copy today!

 

 


ABOUT SSL CERTIFICATES