During the lightning storm this summer we had a number of customers asking us if they require a lightning protection kit for there electric fence .
We thought we would make a small article just to explain what a lighting kit does and some pointers so you can decide if you are at significant risk or not.
Most of us in the UK rarely see lighting but when it does come it can be fantastical destructive.
Most warranties for electric fencing energisers DO NOT cover lighting damage.
What is a lightning protection kit ?
This is a device that sits in line with your fencing and ordinarily does nothing . In the event of a high volt pulse coming back up the electric fence the arrestor kit provides a easy path to earth ( a lighting arrestor kit has to have it own earth stake more on this later ) The bulk of the pulse will use this earth route and effectively be neutralised .
That said a very large pulse can get past the lighting arrestor and break the energiser but with out the arrestor that same pulse could have caused the energiser to catch fire !!!!
As i said above the arrestor provides a path to earth so it is very important that a decent earth stake is used and it can not share the earth stake with the energiser ( or the earth stake for the mains power of a property ).
Why are electric fences a problem ?
The problem with electric fences is that they have lots of metal in them that acts as a huge aerial and will collect any radiated energy. This aerial ( fence) is then all connected back at a single point , the energiser.
Is my fence at risk.
The longer your fence the greater the risk, a small 100 meter fence to stop your pony getting fat is low risk but if you have a big perimeter fence of several thousand meter the risk is proportionally bigger. The key point is that the lighting does not have to give a direct strike to your fence. A close strike with in a few hundred meters can radiate enough energy to cause serious problems back at the energiser. It is impossible to give a hard rule that you should fit a lighting arrestor at a certain length of fence but other factors to consider are if your fence is near tall solitary objects that have a greater chance of being struck.
The picture below is of a mini electric fencing lighting arrestor . The electric fence is in contact with the top stud and a earth stake is connected to the bottom stud
Mini Arrestor Kit
This is the big arrestor kit usually used for mains powered energisers . This would be fitted to a exterior wall or post and the earth stake would be in the ground below it . The black plastic part is a three way switch this can be used to divert the power away from the fence to ground . Useful for maintenance work when the electric fencing energiser is hard to get to .
Lightning Arrestor Kit