An electric fence does not hold animals back with a physical barrier, but with an experience: a short, painful, yet harmless jolt of current that an animal quickly remembers after the first touch and prefers to avoid afterwards. For the system to work reliably, every part of it, from the energizer to the soil under your feet, has to act as one single electrical circuit. Below we explain how that circuit actually forms and what the numbers you will meet when choosing electric fencing equipment actually mean.
The pulse's path from the device to the wire
The heart of the system is the energizer, which generates short electrical pulses at regular intervals. These travel along the lead-out cables to the fence wire and then further along the entire length of the fence. Because the pulses often have to cover considerable distances, it is essential that the wires and connectors are highly conductive and screwed together tightly. Any poor connection along the way means a loss of voltage that may no longer be sufficient by the end of the fence.
Insulators play a special role here: they separate the wire from the posts and prevent the current from diverting straight into the ground instead of continuing along the fence. The same applies to vegetation touching the wire, since it creates small short circuits through which energy is lost and no longer available to deter animals.
What happens when an animal touches the wire
When an animal touches the wire, current flows through its body into the ground. This moment is painful for the animal but harmless, and this applies equally to livestock and to wild animals the fence is meant to keep out. The system works the same way for all animal species, whether the fence is used for keeping livestock in or for protection against predators and other intruders. The current then returns through the soil towards the device. Because soil is a relatively poor conductor, especially when dry, sandy, or rocky, ground rods have to capture this current effectively and carry it back to the energizer through the grounding conductor. Only then is the circuit closed and the device can generate the next pulse at full power.
What joules mean
The power of an energizer is expressed in joules and states how much energy the device actually releases into the fence with each pulse. More joules mean a stronger, more noticeable jolt for the animal, and also make it easier to overcome the resistance caused by vegetation on the fence. Devices vary considerably: a 9 V battery-powered unit may deliver around 0.33 joules, while a powerful 230 V unit can reach as much as 15 joules.
How much power is enough depends mainly on the length of the fence and the state of the undergrowth beneath it:
- up to 500 m of fence without undergrowth, a device with at least 0.25 joules is sufficient;
- up to 1000 m of fence with normal undergrowth, we recommend at least 2.0 joules;
- up to 1000 m of fence with heavy undergrowth, a device with at least 6.0 joules makes sense.
If the vegetation on the fence is particularly dense, the achievable length with the same device can shrink considerably, so it is better to choose a somewhat more powerful energizer than to find out later that the voltage at the end of the fence is not enough.
Three factors for flawless operation
How well a fence works does not depend on the device alone, but on three factors that must work together:
- Conductivity: wires, strands, ropes or tapes must be chosen according to the fence length and expected vegetation, and connectors must always be screwed tight.
- Grounding: without a sufficient number of correctly installed ground rods, current cannot return to the device, which is why we cover this in a separate article.
- Energizer: its power in joules must match the fence length, the undergrowth, and the type of animal the fence is meant to hold.
To make the choice easier, PATURA developed a scheme that, based on fence length, animal type and undergrowth, helps you quickly determine a suitable energizer; a simple version is also available online as a calculator. Kancler Sistem Pro, as PATURA's Slovenian partner, can advise you on this choice based on the actual conditions on your pasture.
Understanding these basics is the first step towards a fence that works reliably all year round, whether it is protecting livestock or keeping wildlife out.
Need advice?
If you want to check whether your existing fence really works as one circuit, get in touch with us and we will help you find the weak spot.