Electric Fence

<...how far a high voltage device can go...> depends upon the energy input to the coil and the resistance of the fence. The forum cannot answer this question. As it is already built, the easiest way to find out is to measure it.

<...how many meters of wire...with the same device...> depends upon its resistance to earth, which the forum cannot answer either. As it is already built, the easiest way to find out is to measure it.

<...estimate this...> Without access to the equipment and its design data, any old guess will do. As it is already built, the easiest way to find out is to measure it.

i have two levels of energy 0,264 and 7,9 joules if i use an iron wire how long can i go? the output is 18kv .. my calculation gave me enormous number ! something probably i have done wrong!

<...if...an iron wire how long...> The forum cannot answer this as it depends upon the local resistance to earth. No-one other than the original poster is in any position to measure it.

Thank you very much for your reply

What constitutes "perfect"? When you start killing animals and people? Electric fences are not normally high-voltage devices.

You lack an understanding of electric fences. Having used electric fences for over 60 years, l can safely say - The higher the voltage the lower the amperage, the safer the fence and the better trained the cows will be. We call them grass burners because they don't short out on tall grass. (and no they don't start fires.)

You err! The higher the voltage and the lower the amperage the better the electric fence.

You might want to consider legal and liability issues. If you build your own electric fence and someone is injured or killed, your legal problems would be greater than if you had an off-the-shelf item. Just sayin'.

Quite. Keep <...sayin'...>.

It also depends on the goal of the electric fence. I worked on systems for electrified fences at max. security prisons. Their deterrence goal was that the fences were DEADLY so we used 1.1kV...

It has to do with ohms of resistance per foot of the wire, the less resistance the longer the run possible even to miles...You do need a pulsing circuit though...

When I worked on my uncles farm - it was a non-issue - but he only had 300 acres.

The only problem we had was when tall wet grass leaned against it - shorted it out.

The odd cow didn't seem to care and just walked through it - but they would also jump a barbed wire fence to get at the sorghum fields.

(Then the boy scouts would challenge each other to peeing on the fence - or the reel test of manliness - how long can you hang on.)

"... how long can you hang on..."

As long as I was wearing decent footwear and standing somewhere dry, it didn't hurt to assertively grab the wire in my palm and hold it through the pulses. If I was barefoot or in a spot that was muddy or hesitated in getting a quick broad contact grip, it was an eye opener.

I wasn't afraid to grab the wire and won a number of bets, but I was never so foolish as to pee on an electric fence.

I will never forget working on my sweetcorn field. I had elec. fence at ankle level to keep the racoons out.

my daughter who was 4 came running to me and said "daddy, daddy,. johnny's peeing on the electric fence.." (he was 6)

I asked him what he was thinking... his reply:

" I don't know, but it made my peepee grow"..

I thought to myself Hmmm....

No I never did...lol

I will say it wasn't a very strong fence, ran off a 12v battery.

Most of the electric fences I have dealt with have a "weed chopper function that will sever a weed on contact.A dry weed has no effect,but a green one will be cut quickly.

Cows are usually easy to train,and once accustomed to their perimeter,they will seldom leave it.

When changing from one pasture to another,a leader cow has to be manually walked across the area where the fence used to be,several times.

I have seen an electric fence literally put a bull on his butt,so I don't think anyone would pee on that one.

"... Cows are usually easy to train,and once accustomed to their perimeter,they will seldom leave it....."

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As long as it remains 'cows', as in there must be more than one. Lonely cows are often escape artists or at least escape enthusiasts.

so is it something that i need to measure, more than i have done, in order to find in how many meters is this device capable to transfer its energy?

To measure the fence voltage you need to make a voltage divider out of 10MOhm resistors of good quality, at least 10 and a 1 MOhm resistor shunted by a 0.1 UF cap giving a voltage divider ratio of 101:1. or if you wish use a 9MOhm resistor in place of a 10MOhm but with the tolerances of the resistor it is purely semantics unless you do as I did and use a resistance bridge to derive 100:1 ratio but it is only an electric fence not a laboratory tester.

A peak measuring multi meter may measure the voltage across the 1MOhm resistor but a moving coil meter is more robust and you don't want to fluke a hit on a Fluke.

The resistance of the fence will be of little concern as mostly the current flowing in the fence is capacitive charging and will serve mostly to alter the wavefront and rise time of the pulse unless a cow's nose is the return path which is snot good for it but the message is received.

i have measured the voltage of the fence and the pic was 18kv ... and my joule 0.264 what else to measure?

See #1⇑.

The power all depends on the dump capacitor value the voltage on the secondary voltage of the inverter and the ignition coil/ encapsulated transformer ratio.

Gobolldy, gobolldy, gook.

You could have made things a lot easier on yourself by buying an actual fencer.

all your answers as well as liability would have been laid out by others.

where the range would be 50 miles, which seems to be quite a bit. At lease to maintain that a mount of fence.

Step #1, get a good personal liability lawyer...

I would compare the output of electric fence devices that are on the market and compare or extrapolate from that. I have seen devices that work for 5 miles and others for 20 mile. There are probably units that can energize fence or much longer distances..

Hi Athmio, it seems you're from Greece, so maybe this will assist in keeping you out of jail https://www.google.com/search?q=eu+regulations+electric+fencing&oq=eu+regulations+electric+fencing.

Locally, we have strict legal limitations on our very popular fixed electric fencing systems, though I vaguely recall that there are differences between fencing for security reasons as opposed to wildlife (game) control and portable agricultural fencing. Issues such as maximum voltage, energy, pulse width, construction details, etc. are covered. And understandably barbed wire may NEVER be electrified. There is an interesting bit about earthing that you may want to consider too. Sorry for not helping directly, can just point you in the general direction!

BTW, our law assumes that you need to protect people accidentally touching it (sorry occifer, I accidentally touched this non-compliant fence on this 3m high wall... yeah, right!) and very specifically that children should be reasonably safe from it, whilst still performing it's primary function. It is most definitely not allowed to be lethal!

Needing an insulated conductor for my electric fence,I used a 100 foot piece of RG6 coax that I had lying around.

I was surprised at first when I detected sparks from the outside insulator of the coax to ground.

Then I remembered that coax has an inherent capacitance,and the outer insulator was charged to the peak voltage of the fence.

Even grounding the shield did not make it go away.

The coax actually had 2 concentric capacitors at work here:

The outer conductor/shield and the inner conductor /insulation/shield/outer conductor.

I decided to mount it on insulators and use it anyway,with the capacitance adding a little more "bite" to the fence.

"... I was surprised at first when I detected sparks from the outside insulator of the coax to ground.

^{Then I remembered that coax has an inherent capacitance,and the outer insulator was charged to the peak voltage of the fence.}

Even grounding the shield did not make it go away....."

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How do you suppose that grounding the shield did not keep sufficient potential for sparking from occurring between the shield and ground?

I am not sure why it did not stop the arcking from the outer insulator to ground,but I think that there are multiple capacitors involved

1 is formed between the inner conductor and the inner insulation.

Another is formed between the inner insulation and the shield,and another is formed between the outer insulation and the shield.

Whatever the physics involved,there was still an arc from the outer insulation to ground even with the shield grounded.

Maybe someone else on the forum can explain it better.

If you have a fence charger,try it you will see.Use about 100 feet of RG6U coax.

I am confused by your terminology. I thought it was just a simple transposition in your first comment to which my previous replied, but with this additional comment, it seems the terminology is as you intend.

You describe arcing from formation of a capacitor in relation to an insulator. I initially thought you meant the conductor shield.

While I realize dielectrics can hold significant charge (see beta irradiated dielectrics discharged to create Lichtenberg figures) and that charge is fundamental to some capacitors capacity, when I think of a capacitor, the fundamental requirements are two conductors brought in close proximity.

Is it truly the insulator and not the conductor shield with which the insulator is in contact that is arcing to ground? And if the insulator is arcing to ground and the metal shield is grounded, why isn't it just arcing to the much closer grounded conducting shield?

The best I can do to explain it is this.

1 center conductor,a dielectric insulator,and a shield,both open at the ends,with the center carrying 8KV.This forms one capacitor.

The shield is surrounded by another insulator,a dielectric.This forms another capacitor.

When the shield is grounded on one end, the field(Earth ground) ground becomes the second conductor.

When the outer insulation is grounded to Earth,it discharges.

The dielectric carries the charge,the conductors mobilize it.

There is 100 ft of coax involved.

RG6 has about 20 pF per foot capacitance.Small amount,but enough to create an arc,although the spark was much less than the primary spark.

I noticed that the outer insulation arc only occurred when the main charge turned off,which would indicate a capacitor discharge.

In other words,it provided a second charge when the main charge was off.

This may not fully explain it,but it is my theory on what was happening.

Constructive feedback is always welcome.

Maybe you have inadvertwntly formed some sort of Blumlein transmission line pulse generator.