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Belg
Jan. 2, 2011, 07:44 PM
Evening,

Been scratching my head on this one, hoping I'm not losing my mind. I've got 5 miles or so of electric fence and on 3 particular runs of it, there is more than one strand.

On two of the three, they are two runs of Poly-braid/poly-rope spaced roughly 18 inches apart, top line powered hot, bottom line a disconnected partial run.

On the third, it's 4 run high tensile, top-only hot, with 12" spacing.

I have good, solid voltage across the system. Here's where I'm scratching my head: the uncharged second strand on the two poly runs, and the second strand down on the high tensile are hot. Nowhere near as hot as the top strand, but tingle hot on the poly runs and almost uncomfortable on the high tensile. Even get one full light... Like 675 volts!

I have walked every inch of this three lines. I have checked every single t-post for arcs, grounds, etc. I've removed any weeds, tree branches, etc; and I'm still getting stray voltage!!!

The only thing I can think of is that the when the hot line is charged breifly and then the circuit is opened again, the magnetic field is collapsing around the second line and generating current like the ignition coil in a car...

Does that make sense??? And if so... Could that also be why we keep getting lame magnetic stripes on our debit cards????

TIA

hosspuller
Jan. 3, 2011, 12:19 AM
More likely, you have a connection through failed or poor insulators. Do you have wood battens to separate the strands? They aren't the best when damp. If the stray voltage is higher when the weather is damp, then insulator issues are to blame. Induced voltage doesn't depend on conduction.

If you want to keep the uncharged strands uncharged ... ground them. But then your fence voltage might be reduced.

Belg
Jan. 3, 2011, 08:34 AM
I physically inspected each insulator for shorts; they would have shown up as brown or black areas on the polyrope. I also checked each tpost for voltage. Nada. Not even the occasional bird doodoo shorts... and those are typically very noisy shorts.

The fence is dry; even if the poly were a tad damp inside, the high tensile wire would have been bone dry. I don't use seperators or battens, I have fiberglass posts alternating with tposts.

Is induction realistic? That's the only cause that makes sense.

Frank B
Jan. 3, 2011, 09:14 AM
...The only thing I can think of is that the when the hot line is charged breifly and then the circuit is opened again, the magnetic field is collapsing around the second line and generating current like the ignition coil in a car...
You nailed it! The problem can also occur on fences run parallel to high-voltage distribution lines.

We had the same problem and wound up having to ground all the supposedly un-energized wires.

Belg
Jan. 3, 2011, 09:37 AM
Dang, did some googling and not only found some pretty interesting info on that, also found out it may be why our DSL is so flaky... and a solution for that.

Okay, glad I'm not losing my mind... and why the more little problems I cleared up on the hot line, the hotter the parallel lines got. "Field collapse perpendicular to axis of a conductor generates current along the axis..." and I've got 1200 feet of perpendicular on that run...

Kinda funny, I've spent 3 years improving the fencelines to go from a voltage problem to a physics problem ;=) Yay, Faraday!