Tips from a New Zealand grazing farmer and consultant to keep your fence hot and your livestock in.
By Vaughn Jones
Editor's note: Noted New Zealand grazing farmer and consultant, Vaughn Jones, has been building and troubleshooting electric fences since 1954. Here he provides a checklist of advice and tips to solve one of the most common causes of fencing failure: Poor grounding -- or "earthing" as they say "down under."
For your fence to function correctly, your earth (ground) system must be perfect. But very few are, despite the instructions provided with most energizers. Also I've not seen an instruction book with complete details of how to achieve perfect earthing and completely trouble-free operation in all respects. So I'll give all I know here:
Most farms seem to have earth systems which can't cope with the flow of electrons coming back to it from fences with poor insulation, leakage into vegetation, and the occasional wire which breaks and touches the ground or touches a non-insulated wire. Energizers have become more powerful, but many ground systems and their recommendations have not kept up with them.
When the energiser (charger) earth system can't handle the increased flow of electrons, they find other ways of getting back to the power supply earth system. Unfortunately they sometimes do this through the cows and milking machine, and through steel water pipes or the water in plastic pipes.
Guide to Good Grounding
When the energiser earth system can't absorb the increased flow of electrons from leakage, electrons find other ways of getting back to the power supply earth system. Energisers put out thousands of volts, and just one volt through the cow's mouth or teats can upset her. Here are methods to follow to avoid that:
- The energiser earth system must be installed well away -- at least 10 m (33 feet) from mains power earth peg, preferably on the opposite side of the building.
- Use 25-mm (1-inch) or larger diameter new or near new galvanised pipe driven as deeply as possible into a moist soil, each at least 10 m (33 feet) apart. Thin, black or rusty fence posts or similar are not suitable. Rust is a bad conductor. A large surface area is needed to give a large contact area between the soil and pipe.
- One metre (3 feet) of earth pipe per joule of output of the energiser is usually sufficient for satisfactory earthing in conductive soils. Long earth pipes which are driven deep into the soil give far better earthing than the same total length at shallower depths because soils are more moist and have more conductive minerals at lower levels. Two 3- metre-long pipes are better than three 2-metre-long pipes when driven deeply this way. Large diameter pipes have a greater soil contact surface, so are better than thin rods.
- Install the earth system well way from water pipes and bores which are being used. But an unused steel pipe bore can be an excellent earth if it's not rusted or broken.
- Connect the terminal marked Earth or Ground to the earth pipes by one continuous length of double insulated electric fence leadout cable -- not household or industrial cables which are made for only 400 volts, not for 10,000 volts. The cable should contain 2.5-mm (16-gauge) galvanised wire -- not thinner and not copper wire, which causes electrolysis at the joins. Bare and clamp the cable securely to each pipe with galvanised clamps. Ordinary galvanized wire can rust where it is damaged or touches the ground. Using cable eliminates this.
- It is best to have no voltage on the earth system, but a maximum of 200 volts (and up to 300 volts on a large energizer) are acceptable when the fence has been shorted out to as low a voltage as possible.
- Soils are not good conductors, so electrons spread out inclining towards moist and mineral soils when travelling back to the energizer. Aim for a moist area, work out a system of keeping the area around the earth pipes moist. If necessary, take a galvanised wire along the bottom of a fence to a moist area, and then install more earth stakes at that point. If the distance exceeds 100 metres, use two wires. Better still, use aluminium or aluminium-coated wire which is up to three times more conductive than the same thickness galvanised wire.
- Some soils are very bad conductors. If you have dry peat, pumice, volcanic ash soils, etc., or soils that are dry at any time of the year, and there is no wet area within a few hundred metres which could be used, a bentonite earthing system can be bought and used. They are a good value. The bentonite mix is made into a slurry and poured down 75-mm (3-inch) diameter or larger holes with pipes set in the centre. Keep them moist. This system can improve earthing by up to ten times.
- In extremely dry areas and on snow, use an earth wire return system. This is where there is an equal number of live and earth wires kept well apart on the fence. The earth wires are joined with joint clamps (like the live wires) and connected to the energized earth terminal. The earth wires should also be earthed adequately (no voltage on them) every kilometre. These also act as lightning conductors, keeping it away from energizers.
- Testing an earth system without the fencing shorted out is a waste of time. You must create a flow of electrons to load the earth system before testing it.
- Also testing the earth by holding the last earth pipe can be a waste of time if the wire between it and the energiser is broken.
- To test the earth system, first short the fence out with steel rods at least 100 metres from the earth system. Then use a digital voltmeter to measure the voltage between the energiser earth terminal and an independent earth wire. This should be pushed as far as possible (about one metre) into damp ground in a position handy to the energizer and several metres away from any other earth peg.
- To lower the voltage on the earth system add more earth pipes and/or connect the earth wire to the bottom wire of a conventional fence.
- Never use your water supply, bore or well as a ground or allow a charger ground wire to touch them or any part of buildings. It can cause shocks in the water and stop animals from drinking, and buildings can become a transmitting aerial for radio and phone interference.
- Double insulated underground cable should be used for the ground as well as the live wire. Unused bore pipes or steel well liners are usually good grounds.
- Many New Zealand farmers measure Joules (energy) roughly by holding the live wire and feeling the kick in good insulated gumboots standing on one foot to halve the electrons flowing through your body. Caution: Don't do this if you have a dicky ticker or Pacemaker.
- High-power energizers are essential for to controlling animals where long lengths of wire are electrified. The high power is on for the very short period of 0.0003 seconds which makes them safe.
- Voltage measured at the energizer is useless, especially if the fence wire is thin, limited to one wire or has bad connections. But voltage can be an indicator of the energy when measured at the end of a long fence.
- The latest, best New Zealand energizers have a system of telling the farmer at the energizer the effectiveness of the fence at various points, and the earth condition, both of which are extremely clever.
- The lower the voltage on the ground the better it is. But with high-power energizers, it can be difficult to get the voltage below 200 volts, which figure is acceptable (provided it was measured when the fence was shorted (grounded) a few hundred metres from the energizer).
- Ensure that all electrical appliances wirings, everything metal and all concrete steel reinforcing are all connected by welding or strong galvanised clamps, not electroplated ones which rust sooner.
- If your stock are going through fences, check the earth first, followed by the joints on the whole fence, and at the same time look for shorts.
- Test your earth by thoroughly shorting out the fence at least 100 metres (330 feet) away from the energiser with steel standards. Doing this creates the maximum current flow so puts a load on the earth system. If your earth pipes can't handle the flow you'll get a voltage reading at the energizer terminals. If there is no voltage, then your earthing system is satisfactory.
- You should have a digital voltmeter, then install an earth monitoring point by pushing a piece of 4-mm (8-gauge) wire into the ground handy to the energiser and measure between it and the energiser earth terminal. Don't check the last earth pipe because there could be a break in the wire to it, in which case you'll think the earth is OK, but it may not be.
- With the fence shorted out, there should be no more than 200 volts, although no voltage reading is best. The more voltage you read flowing to your earth, the less power you will have on your fence because it indicates that the earth is inadequate and needs more pipes.
- To improve your earth system, increase the number of earth pipes and put them in as deep as possible. Tests on several soil types have shown that depth is essential -- 2 m (6 feet) deep is the minimum, and 3 m (9 feet) deep is twice as good.
An inadequate earth system reduces the output of your energiser and increases the chances of shocks in milking parlors, yards and water troughs. It takes an expert with sensitive measuring equipment left connected for 24 hours and a recorder to check for shocks in parlors. There may be none during the day, but they can occur when heaters, cookers, etc., are switched on in the late afternoon.
Check your parlor twice a year and yards in many positions at the height of dry weather and the height of the wet period. See your energiser installation instructions for more details on installing it and an earth system.
Poor Earthing Costs Production
A common problem is having energiser earth pipes behind the milking parlor. Leaked electrons (there are always some) flow from the farm under the yard and parlor when the soil is moist. But when it is dry, they look for easier routes, which can be across a moist yard and through parlor pipe work.
In wet weather, electrons can travel along the soil surface and through the parlor, especially after cows enter and pass their high mineral, highly conductive urine. This can cause electrons to even flow across the concrete surface and across pipe work, so affecting the cows.
A short or weeds conducting power off a live wire close to the parlor can result in electrons flowing through the parlor and/or yard because it is the shortest route, especially after cows enter and urinate. The above can occur even when the earth system is perfect, simply because the electrons are flowing to it via the best, shortest and fastest route.
To avoid this, earth systems should be in a damp area well to the side of the milking parlor, or even have earth pipes well to both sides, but never in line with the parlor. The earth leadout wire from the energiser should be insulated, and not allowed to touch any other wire, building or pipe.
Electrons can also move through water pipes, giving shocks to cows when drinking in a paddock, so no wires should be allowed to touch water troughs. Even if not electrified, they can conduct induced current. Cows standing around a full trough waiting to drink can be a sign of power deterring them from drinking.
Where conventional fences have a live wire running with them or as an offset wire, the conventional fence wires can absorb induced current (more so in damp conditions) and become electrified. So unelectrified wires must be earthed or they can build up a voltage which can:
- Jump gaps (bad joins) and cause sparks and radio and phone interference.
- Conduct current to water troughs they may touch. Animals then won't drink so growth and milk production suffer, and females can get cysts on their ovaries through stress. This happened to a herd near here causes calculated losses of $30,000 over the years it had been happening.
- Give people shocks when opening and closing gates.
- Give animals shocks as they go through gateways and brush against the wires tied around strainer posts.
Shocks in sheds and water troughs have cost some farmers small fortunes in lost production over several years, until the problem was identified. New Zealand manufacturers discourage grounding the fence circuit though the earth or ground terminal of the charger to the utility (power supply) grounding system because it is illegal in many countries and can cause shocks in all directions including in your shower. The power supply ground is usually just a metre deep rod. A modern high power New Zealand energizer needs ten to twenty times more.
Safety Considerations
Keep these in mind when you build fence:
- Don't string wires across lanes or thoroughfares without marking them clearly. Motor cyclists have been injured through not seeing them.
- Never electrify barbed wire.
- Train and demonstrate the shock to children and visitors with a long piece of grass.
Electrified fences in any position where the public could come in contact with them must be clearly marked with approved warning signs at frequent enough intervals so as to be easily seen.
Radio Interference
It is an offence to operate any appliance which causes any electronic interference, so points to note include:
- Some energizers cause more radio and/or phone interference than others, even if not on a fence. Switch it off, disconnect the fence and earth (ground) cables (wires) at the energizer (if they were loose the sparking there could cause interference) and switch on the energizer and check for interference.
- If the interference is still there, return the energizer to the supplier and try another unit or brand. Some brands are bad.
- If the interference disappears when the fence and earth are disconnected:
- Tighten all joins and clamps on the energizer and fences. Those on some energizers work loose because of the thump (vibration).
- Ensure that all wire connections are figure of eight or reef knots, or are clamped and tight.
- Tube insulators will crack and leak in time. Even double tubes and those with steel inserts leak and spark in some cases.
- Sparking causes radio and telephone interference so insulators must be good quality with adequate tracking distance to avoid arcing over the surface as occurs with staple insulators or through the insulator as occurs with single tubing. Use quality insulators with at least 25 mm (1 inch) of tracking distance (length on insulator from the live wire to any other point).
- Some cable can have breaks in it causing sparking. Single insulated cable gets cracks sooner than double. (Try bending a sheet of cardboard and a wad of paper the same thickness and you'll see why. The card will crack.) Some of the orange cable from New Zealand cracked and leaked soon after installing. Replace it all.
- Even the best cable when buried can become damaged by a stone and then leak. It is essential that all be threaded through 12 mm (half-inch) or similar black plastic piping to give it physical protection. If the distance is long, push a piece of high tensile wire (with its end bent back) through and then pull the cable through. To check under gateways, disconnect before each one and check if the interference stops.
- Ensure that the earth is perfect. Check it at the energizer, not at the last earth pipe as shown on some instruction books. There could be a break in the cable so there would be no voltage at the last, or even first pipe.
- The earth cable should be one continuous length of double insulated cable or be joined with a good galvanised joint clamp, and must not touch any building or pipe. Support the cable in good insulators.
- Use a digital volt meter to test the earth and to locate shorts and maintain tidy, trouble-free fences.
- If you still have interference, tighten all joins and clamps on the farm. This is best done in summer when joint clamps have expanded.
- Walk along all fences and wires with a radio tuned off the station and clicking. It will get louder close to the interference cause.
- Shorting to vegetation or to any grounded object can cause clicking, so disconnect the bottom wire and/or clear the fence line with a weed wiper. Once grass touches a live wire, stock won't graze it, or anywhere near it, so the problem increases. Always have the bottom wire able to be disconnected with a flexible connector and do so before vegetation touches it.
- The mains power supply (utility) earth and all connections including power point terminals and plugs must be adequate with no loose or old verdigris connections.
- If wires run parallel with overhead phone wires on underground phone cables interference can be worse, so avoid the constructing of electrified fences parallel to telephone lines or cables and aerials, or parallel to other long fences which could act as aerials.
Radio interference is worse in poor reception areas, and if the radio is not tuned exactly on the station. Telephone systems are not always perfect.
Lightning Protection
The long distances of electric fencing now used increase the chance of a lightning strike, so an effective protective system should be used. Lightning often hits the power supply line and goes through the energizer to its earth system blowing its fuse or components. The power (utility) supply earth system should be good enough to attract the lightning rather than have it go through the energizer to its earth.
Finding Shorts
The solid state digital volt meter is important for fault finding and for testing the earth system. It enables accurate reading of the voltage and easy fault finding, because of its extreme accuracy.
Start by going to the first switch (these must be installed along fence lines to save going back to the energizer to switch it off for repairs and for fault finding) and see if the voltage before the switch increases after opening the switch to stop current flow down the farm.
If the voltage increases then go to the next switch. If not check the fence between the switch and the energizer. Neon fence testers are also available, but of no use for finding small leaks or earth system faults. Many are bought and not used for long before buying a digital volt meter.
Electric or power fencing helps make animal farming profitable and sustainable, so the effort required to achieve the above suggestions is well worthwhile. If installation is good and monitoring is done, the labour required is less than with any other system and the profit is greater.
If you have problems, read all the above again. There is a lot to take in, but once you understand it, it becomes second nature.
Take pride in your fencing and enjoy your animals.
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