|Function of an electric fence
Technically, an electro fence is not a closed electric circuit. The circuit is closed, if a animal touches the fence or comes very close to it. The electro impulse flows through the animal into the ground and triggers a short pain in the animal.
The good experience with electro fences shows, that most animals learn very quick to avoid contact to the fence. Only every now and than are so called freshening impulses (“reactivation of the experience”) are needed.
Parts of an electro fence
An electric fence consists of four main parts, building a chain:
The fencer produces regular electro shocks with short durability
The conductor materials. Wires, flexes or tapes, deliver these shocks along the fence.
Insulators make sure that the electricity will not go into the ground without an animal contact.
Earthing bars deliver the electricity back to the fencer, if the electric circuit is closed.
The electric fence system can only work, if all four parts are present, fully functional and correctly adjusted to each other. A chain is just as strong as its weakest link!
The aim for every fencer maker is to build a secure fence.
Requirements for a secure fence
A fence is seen as secure when there is no danger for humans, animals or objects from it.
Therefore following facts have to be considered
- Adjusting the length of the fence for the individual requirements of the location (e.g. pasture location, kind of animals etc.)
- Use of the right fencer with sufficient impulse energy
- Use posts, conductors and insulators which are correctly adjusted to each other
- Providing the minimum values of voltage and impulse energy (Maximum values can not be exceed for security reasons).
- Daily checking (responsibility of owner)
Fencing voltage and kind of animal
Fencing voltage is the voltage peak of the electric impulse that is provided by the fencer. There are two groups of pasture animals, easy ones and difficult ones to fence.
Easy to fence animals have mostly little hair, are used to the fence and keep distance from the fence (except from seldom freshening impulses). Cattle with short hair, horses, pigs, and other pets belong to this group. They require a fencing voltage of at least 2000 Volt everywhere on the fence, also at the end of the fence.
Difficult to fence animals have a thick coat, like sheep and Highland cattle, or are not used to a fence, for example wild animals. They require a fencing voltage of 4000 Volt which has to be present everywhere on the fence, also at the end of the fence. The higher voltage is required because of the higher resistance of the thick coating of the animals.
Fencing voltage under practical conditions
The stipulated fencing voltages of 2000 and 4000 Volt are required, to ensure the electric circuit will be closed and the animals gets a short pain. This voltage has to be present at practical circumstances and not just the voltage that is provided by the fencer without a fence. The combination of fencer and fence in practical conditions is conclusive. In the case of doubt, conductors, fencer and vegetation has to be adjusted.
Above values showing, that high performance fencer are needed for difficult to fence animals and fencers with lower performance are suitable for easy to fence ones.
The impulse energy is the maximum energy of an impulse, provided from the fencer to the fence. It is measured in Joule. The higher the impulse energy is, the stronger the pain felt by the animal and the higher the keeping security.
Additionally vegetation dries quicker on the fence. But there are maximum values stipulated for the impulse energy, max. 5 Joule at 500 Ohm assumed animal resistance, to prevent injuries or health damage for humans and animals.
Why is good earthing so essential?
Earthing is indispensable for the right function of a fence. Requirement of any electric flow is a closed electrical circuit. In a fencing system the circuit is closed through the animal and the earthing. The electrical circuit is closed by the ground and the fence, if an animal touches the fence. The “conductor ground” has a high resistance. The earthing bars enlarge the cross section of the “conductor ground” and the resistance lowers. Because electricity takes always the way of the lowest resistance, it flows through the ground to the earthing bars and from there to the fencer. The electric circuit fencer->fence->animal->ground->earthing bars->fencer is closed and the animal becomes a short shock.
Improper earthing results in weaker impulse energy on the fence, the keeping security is lower. If earthing is missing, the electrical circuit can not be closed – the animal doesn´t get shocked – the fencing system doesn´t work.
Which conductor for wich fence?
Conductors transport the voltage energy which is produced by the fencer. There are three different kinds of conductors available: wire, cord and tape. Conductors with low resistance provide low voltage losses, which has an influence on the fencer being used and/or the possible fence length. Wire with 2,5 mm diameter has the lowest resistance. In this category aluminium wires have a better conduction than steel wires, but provide lower tension resistance due to their soft material. The conductivity in cords and tapes is dependent on the material – copper conducts better than Nirosta – and on the number of conductors. The choice of the conductor can not only be decided by technical matters. The conductors are determined in a big way from the animals which have to be fenced in. Fences for dairy cows, suckler cows, cattle or bulls are normally equipped with wire, the same as for sheep, goats, pigs and poultry and for keeping out game. A good wire provides a high conductivity, strong tension resistance and good value for money.
Flexes and control wire are used for the inner fence in paddock grazing. Electric fencing mesh is offered especially for the fencing of sheep, goats and poultry. The mesh conducts and the mesh space is adjusted for the relevant animal. When fencing horses the visibility of the fence is very important. The horse has to be able to recognise the fence clearly. TEXAS TRADING recommends therefore the Permanent – Horse wire: It provides super conduction and very low risk of injury, but it is highly visible because of its wrapping with conducting plastic. Alternatively cords and wide tapes can be used. But by using these cords and tapes, only high quality materials should be used, because of their higher resistance. Cords should be choosen instead of tapes, because they usually have a higher conductivity, no problems in windy conditions and smaller length differences if temperature varies. Sensitive horses can be irritated by flattery tapes and big changes in temperature, which occurs particularly in the spring or autumn within a day/night rhythm, need a lot of maintenance for tensioning or loosening the tapes. We recommend the electro cord G600: It provides high visibility for horses, has outlaying conductors, no wind problems and the length change is low if temperature varies. Beside that, is has a nice design and enables not only a good looking but also for a trouble-free technical fencing
ADVICE: Calculation for the length of the conductor
Single fence length in m x number of conductors + 2 % for waste material, cross connections and corner connections = total length in meters. Please round up to complete rolls.