Thursday, March 28, 2024

Finding the juice leak

Avatar photo
Farmers would probably all agree there’s nothing worse than stock getting out because the electric fence isn’t working.
Reading Time: 3 minutes

Finding the reason can take minutes or sometimes hours checking electric fence units, earths and connections and looking for shorts.

Electricity can be felt, sometimes heard and more rarely seen so you have to use a range of senses to figure out what is going wrong and why.

Start with the electric fence unit.

Whether connected to mains power, a battery or a solar panel, it sends a brief electric current through a fence wire at a pulse rate of about one second. Each pulse lasts about 0.0003 seconds.

Mains-operated units should be installed under cover, away from children and flammable material. Portable units such as battery-powered units should be kept out of reach of animals and off the ground to protect the electronics from moisture and insects.

Make sure the fence unit is on, no one has turned it off by mistake or taken it away, and the connections to the fence and the earth haven’t fallen off. Units can also be prone to lightning damage.

Batteries can fail and solar panels should be checked to make sure they’re not in the shade, which can happen in winter when the sun is lower, causing longer shadows.

Insulators stop shorts on fence posts.

Leakage is when the voltage is reduced on the fence because of something touching the wires. A dead short is where the fence is broken and there is no pulse after the break.

To find both, isolate sections of the fence starting from the electric fence unit and test the fence at 100m intervals.

If there is leakage the voltage will fall until the fault is reached. After the fault is passed the voltage will remain the same so when you discover this point backtrack until you find the fault.

If you find no voltage on the fence you know you have passed a dead short.

Some shorts will make a loud “crack” sound, especially in wet conditions, and sometimes a flash can be seen.

Faults usually occur where wires are connected and have come apart, at insulators, under gateways where wires might have become water damaged and broken, or where branches have blown onto wires.

Stock or dogs jumping over a fence can hook a non-electrified wire to the electric wire causing shorts. Possums and birds, especially pukekos, can also become caught in fences.

When looking for shorts check older fencing first. Wires can sag on to each other, older insulators can break and Insultimber eventually decays.

Something as simple as a staple hammered in too tightly around a broken insulator so the staple is touching the wire can cause a fence to fail.

If the electric fence works as a continuous loop faults can be harder to locate because the pulse is being pushed through from both ends by the electric fence unit. To find a fault in a continuous loop fence, disconnect part of it first.

A sure sign you have a dead short on the fence is when you hook a gate wire back up and it makes a loud “crack” sound. Look further down the line, away from the fence unit, to find it. Also remember electricity is lazy – it won’t travel in a straight line but instead takes the easiest route back to the electric fence earth.

If cows don’t like walking on part of a track, check for leakage. Manure is a good conductor of electricity and the cows might be getting a shock from a short nearby, even if the track is curving away from a fence.

Pre-calving electric fence check

• Check voltage on fences to make sure it is in the required range.

• Check fences for long grass, branches from trees, discarded balage wrap or anything else touching or about to touch wires.

• Check older parts of fences to make sure insulators are still doing their job and that wires aren’t sagging and touching.

• Check the earth and the unit are working correctly and not interfering with the dairy.

• Watch stock behaviour – they know where the shorts are. They also know when fences aren’t working.

Total
0
Shares
People are also reading