electric fence mystery help please

[wade]

I have an interior fence, cedar posts and 4 strands of barbed wire. I decided to put 2 strands of electric on this fence also. I put one strand of electric above the top strand of barbed wire. The other strand of electric I put on the inside of the fence between the top strand and the second one from the top. This is where it all gets confusing. When I hooked the electric up and made it hot my barbwire that is stapled to the posts also became hot. All the electric is run through insulators at every post and corner post. I used plastic nail on insulators and switched them out to porcelain insulaters with the same affect. There is nowhere on this fence that the hot wire is shorted to the barb wire. (I have had 4 people look at this fence and everyone says the same thing, we have no idea). The top barbed wire is the hottest (but not quite as hot as the electric fence). The second barbed wire down from the top is not quite as hot as the top barbed wire. The third wire down isnt as hot as the second wire. The bottom wire you can barely feel the current in it. So, the top barbed is the hottest and the bottom is the least hot. On one top barbed wire I even put an insulator on each end of it and tied it to the corner post. The barbed wire is still hot. If I cut the juice to the electic wire along this stretch of fence the barbed wire doesnt stay hot. I am at a loss here. Please dont say I have a wire laying on the barbed wire because that isnt the case. Even if I did, I would have to be shorted to all four strands of barbed wire. None of the barbed wire is touching eachother at the corner posts. The only thing the barbed wire has in common is that it is stapled to the posts. I have built lots of fence, the hired man has been on the same farm maintaining and building fences for 40 years and he also is stumped.

 

[Farmer Z]

Well, first of all, you got yourself a "weapons grade" electric fence when the regular barb gets hot for no reason! I'll bet your cattle behave. Seriously, I have no idea how this is possible. Could it be that you have an insulator wire tied to a post - with the elecric wire touching that tie wire - sending electricity through cedar posts that have acidic moisture encased therefore acting as one big electrical field. Hey, I think I just won a Nobel Prize...or just earned a trip to the psych ward.

 

[Douglas]

It called induction i think. Will look for link

 

[Douglas]

INDUCTION
A phenomenon known as induction is common with electric fences. This is the transfer of electricity from an electrified wire to a non electrified wire without the wires physically touching each other. This is often mistakenly blamed on insulator leakage. This phenomenon is also more common in areas where the air is damp such as in conditions of fog.

As this phenomenon is a quirk of nature it cannot be stopped from occurring. However, to avoid receiving shocks caused by induction on non electrified fences and gates etc. you can "ground out" the offending fence by connecting a ground wire to all wires on the non electrified fence. Push the end of this wire into the ground as far as possible and this will send all the offending voltage into the ground.

http://www.kencove.com/fence/resource.php?detail=101

 

[dun]

It called induction i think. Will look for link

Yup, that's what it is!

 

[Farmer Z]

Dang...the "induction" answer seems right on. I'll go ahead and get packed for the trip to the nut house...

 

[wade]

Farmer Z. When I had these plastic insulators on the fence I went around and stuck a rod in the ground and put my finger on the nail of each insulator. I found 2 nails that had some current that I could feel going through them. That is the reason I switched all them and replaced with porcelain insulators. I am almost ready to commit myself to the psyche ward over this, so you wont be alone if you go there.

 

[Douglas]

Farmer Z. When I had these plastic insulators on the fence I went around and stuck a rod in the ground and put my finger on the nail of each insulator. I found 2 nails that had some current that I could feel going through them. That is the reason I switched all them and replaced with porcelain insulators. I am almost ready to commit myself to the psyche ward over this, so you wont be alone if you go there.

When i put up my first high tensil fence i spent days and days trying to figure it out. Like you i had nails that were slighlty hot. I also had small voltage on my brace wires, even a corner post had some voltage. Not till i tested an old fence someone else built did it figure out that it was happening everywhere. I now move my brace posts away from the fence line and don't attached the line to them.

 

[wade]

Thank you very much fellows. I guess the reason this bothered me so much was I didnt understand how I could have something hooked up wrong and I thought it was probably robbing current from my fence. I guess that isnt the case. Think I will ground the barbed wire so if I have to work on it I wont get this shocking feeling. I have been poked so many times checking that fence I am getting real gunshy of electric. Thanks again for you help.

 

[ga. prime]

Wade, I went through the same learning process you just did a few years ago. I about went crazy looking for a short between the hot and the barbed wire. Ground your barbed wire and the shock treatment will cease. We have maximum humidity here, especially in the Summer months. You can take a volt meter and it will light up several inches from the hot wire. I have to do it at night because I can't see the light in the daytime.

 

[kenojoe]

How far apart are the "hot" wires and the barbed wire? I think what you are having is capacitive coupling. To have inductive coupling you have to have some level of current, which the fence charger can not produce. The more separation between the hot and barbed wires the lower the capacitive coupling. I would be curious to know if you check the hot wire with a "good" fence tester and get a reading of what your charger is putting out , and if it changes any when you ground the barbed wire. I don't think you will see any change.

 

[dun]

From my basic electricity that I took in the 60s, it seems that inductance is caused by lines of flux. My surmose is that each time the charger pulses it causes lines of flux from the charged wire cuts the line of the barbed wire causing the barbed to become hot.
But that class was a long time ago.

 

[bird dog]

I get light shocks on a regular barb wire fence that is close to a high voltage line that crosses my place. You will definetly scratch your head the first time you feel it.

 

[hayray]

I had that problem a few years ago around my paddocks on woven wire. I added a lot more ground rods and that fixed the problem. The guy I buy my electric supplies from says he has had to put up to 11 rods in the ground before getting a proper ground on some sites.

 

[lavacarancher]

From my basic electricity that I took in the 60s, it seems that inductance is caused by lines of flux. My surmose is that each time the charger pulses it causes lines of flux from the charged wire cuts the line of the barbed wire causing the barbed to become hot.
But that class was a long time ago.

Well, this one has been beat to death but you are right on the money, Dun. Same principal makes a transformer work, lines of flux cuts the adjacent conduct, induces voltage (EMF), etc.

 

[yme]

I have a wire hanging on eclectic line poles that is a long 1/4 mile from the barn to the start of the fence. It never fails that I get shocked on this fence. The first time I got hit I knew I had unplugged the fencer but went and checked anyway, it was, touched it again, shocked again, just knew someone was at the barn and messing with me. Someone smarter then me told me this was induction and explained it to me. I now have that line hung and connect with it by way of gate hooks so I never have to touch that wire and so I can unhook the fence to work on it without worrying about getting shocked even where the fencer is unplugged.

 

[tytower]

Theres some more to consider too
Firstly the pulse of high voltage travel
s down the hot wire which is not grounded so it gets to the end and then comes back!
There is a current but its small. However on long runs current running in one wire induces current in the other wire even though insulated from each other and thats exactly what happens in a transformer.

Now whats not often realised is every bit of wire like this is an antenna and all of the electromagnetic frequencies are picked up by it and as in radio any paricular frequency can be sucked out of it by a radio tuning the rest of the frequencies to ground.
So there is a varying voltage in any of the wires you are looking at and I would have a good look around for local radio wave sources too -Government bases ,experimental discharges ,aliens ,who knows