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How Does Electric Fencing Work?

Please view the electric fencing guide below that explains some of the questions we are asked. Every electric fence system is different but the principles remains the same on installation, maintenance and how it is used.

Uses for an electric fence

Electric fencing is used for either keeping animal in or keeping predators out. Electric fences can be used with horses, sheep, pigs, poultry, goats and even zoo animals. Electric fencing is less expensive and needs less maintenance than conventional fencing.

How does electric fencing work?

The fence is charged by an electric fence energiser that sends a high voltage current through the fence line. Wire, tape or rope can be used as the fence line depending on the animal it is containing and the conditions it is situated. The charge is sent through the fence in 1-2 second intervals. The fence acts as an open circuit that closes and becomes complete when an animal or person standing on the ground touches it.

When the circuit is closed, the current runs through the animal or person and it results in a shock. The voltage on the fence is determined by the fence energiser that is powering the fence line and how low the resitance on the fence is. It takes less voltage for short haired animals than longer haired animals. In many cases it only takes one shock from an electric fence to keep the animal from touching it again. Once they receive a shock from the fence most animals will want to keep their distance and remember the electric fence is there. Some animals are more stubborn and will try test the electric fence a few times before they decide to stay away.

Electric Fence System

For a complete electric fence system there are several components that are needed. Generally every electric fence system will have an electric fence energiser, a power source (mains, solar or battery), an earth stake, insulators which can be plastic posts and a fence line. These components will generally create a circuit which would be completed by the animal when it touches the fence. Although you will have an electric fence system it is usually the case depending on the animal you are fencing along with the proximity and location of the fence. These smaller parts will help make your electric fence work more effectively and be easier to use. Important parts are straining posts, electric fence gates, tape, rope and wire connectors, electric fence testers and fence posts for strip grazing.

Why not just connect a fence directly to a mains supply?

An electric fence will not work effectively and be very dangerous if it is connected directly to a mains supply and should never be done. All electric fences need an electric fence energiser that is regulated. Electric fence energisers convert mains or battery power into a high voltage pulse. The fence energiser transfers this pulse on to an insulated fence line just about once every second. The pulse itself is only around 150 microseconds long and is not continual.

Does an electric fence hurt?

This pulse is commonly referred to as the "shock" and is felt by any animal which touches an electrified fence. When the animal makes contact with the fence the circuit is complete if the animal is grounded. It is at this point the animal receives a shock. The current flows through the animal back to the earth stake for the system to complete a circuit.

An electric fence is a much more a psychological barrier than it is a physical one so the animal must be educated and trained to respect the fence. The pain that an animal feels is very short lived and does not physically harm the animal.

Importance of grounding your electric fence system

Many people overlook the importance of grounding or earthing your electric fence system. Around 90% of fault or poorly performing electric fences are down to poor earthing. An electric fence depends totally on the current being delivered to the earth stake or ground rod to complete the circuit. Inadequate grounding will not only limit of amount of electricity that can through the electric fence but also create a stray voltage risk. In determining the earth size you will use it will depends on a few factors. Larger electric fence energiser will need larger earth stakes, as a general rule its better to get a larger earth stake than needed if your are unsure. Also the more moisture in the soil the better the fence system will earth. In dry soil conditions its advised to install more than one electric fence earth stake.

Working out the perimeter of your field using the hectare or acre measurement:

Determine your perimeter length:

(0.1 hectares) ¼ acre = 127 metres
(0.2 hectares) ½ acre = 180 metres
(0.3 hectares) ¾ acre = 220 metres
(0.41 hectares) 1 acre = 255 metres
(0.81 hectares) 2 acres = 360 metres
(1.21 hectares) 3 acres = 441 metres
(1.62 hectares) 4 acres = 509 metres
(2.02 hectares) 5 acres = 569 metres
(4.05 hectares) 10 acres = 805 metres
(8.09 hectares) 20 acres = 1141 metres
(16.19 hectares) 40 acres = 1609 metres
(20.24 hectares) 50 acres = 1800 metres