Members Audiopile Posted May 2, 2015 Members Share Posted May 2, 2015 This morning I got roped into fixing the neighbor lady's partially dysfunctional electric fence... she offered cookies. I used an electric fence tester to assist in troubleshooting, which is a purpose built voltmeter type unit for measuring the voltage of a pulse charged fence. Directly to the lugs on the fence charger the tester read 8,900 volts. As I went down the fence line, the tested voltage raised proportionally to the distance I was from the charger, being: About 1/4 mile down the line the tester read 9,200 volts, 1/2 mile from the charger yielded a reading of 9,500 volts, the 1 mile reading was 10,100 volts, 2 miles read 11,300 volts. There's two legs to the fence, not tied together at the far end, because the two legs of the fence terminate at two sides of a large corral complex... but both legs read the same incremental voltage increases as the distance from the charger increased. That was counterintuitive for what I expected... I expected there'd be voltage drop... but then I got to thinking: The fence wire runs likely function sort-of like a large capacitor... current doesn't actually flow through the fence wire, but rather the wire is charged and dissipates to the atmosphere, but I can't explain why the voltage increases rather than drops or stays the same on down the line from the charger? Link to comment Share on other sites More sharing options...
Members agedhorse Posted May 3, 2015 Members Share Posted May 3, 2015 Well, I suppose I'm kind of an electric fence expert... but I'm also an expert at avoiding electric fences because they hurt like hell if you get bit. There's a couple of possible explanations, the first being that the opposite end of the fence charger which is supposed to be tied to ground is floating somewhat. If the fence charger is not ground referenced, it's possible that it's your reference that is changing and not the actual voltage. At the far end of the fence, with a piece of wire connected to the closest fence post, see if you can draw a spark at the far end when just barely touching the wire. Always have the end grounded to the T-post first which limits the voltage rise above ground and hence the shock hazard. If the problem is very dry ground limiting the reference (making the ground reference rise with distance), another way to really "tune up" the system is to run an additional wire from the charger ground, clipped to each T-post with a conductive clip. This will stabilize the local reference. It will also increase the bite if a system suffering from poor local grounds. A fence charger uses an inductive discharge coil just like a car ignition, the energy is stored in the magnetic field of the coil and when the current through the coil is interrupted, the back EMF of the coil due to the collapsing magnetic field generates a high voltage pulse. The duration of the pulse is fixed, therefore the energy limited. This is why you don't die from such a shock (though you may wish you died). Ultimately, the charge leaks away between pulses, the insulation to ground is not perfect. Link to comment Share on other sites More sharing options...
Members Pro Sound Guy Posted May 4, 2015 Members Share Posted May 4, 2015 Yea in high school a buddy took a wiz on an electric fence. Only for a split second. Link to comment Share on other sites More sharing options...
Members nchangin Posted May 4, 2015 Members Share Posted May 4, 2015 At the far end of the fence, with a piece of wire connected to the closest fence post, see if you can draw a spark at the far end when just barely touching the wire. Spent my child hood doing this on the farm, the old man always said if there's a spark on the line when you just barely touch it, there's a short on that section....Now go find it boy.......Boy all the "sparked" memories are coming back... Link to comment Share on other sites More sharing options...
Members Audiopile Posted May 4, 2015 Author Members Share Posted May 4, 2015 There's a couple of possible explanations, the first being that the opposite end of the fence charger which is supposed to be tied to ground is floating somewhat. If the fence charger is not ground referenced, it's possible that it's your reference that is changing and not the actual voltage. At the far end of the fence, with a piece of wire connected to the closest fence post, see if you can draw a spark at the far end when just barely touching the wire. I suspect the AC feed to the charger is likely not grounded. The charger is housed in a old shed, with what I'd suspect is WWII era or earlier AC wiring. The dysfunction with the part of the fence that wasn't working was a simple break in the wire... looked like it got tagged with a field implement. Link to comment Share on other sites More sharing options...
Members agedhorse Posted May 5, 2015 Members Share Posted May 5, 2015 The negative side of the charger should have a solid connection to ground (earth). I have run this to a few t-posts or have seen an entire strand bonded to all the t-posts for added kick in the ass. Will drive a pretty long fence this way, but the ground wire needs to be separated from the hot wire by at least 6" (or more). Link to comment Share on other sites More sharing options...
Members Audiopile Posted May 5, 2015 Author Members Share Posted May 5, 2015 The negative side of the charger should have a solid connection to ground (earth). I have run this to a few t-posts or have seen an entire strand bonded to all the t-posts for added kick in the ass. Will drive a pretty long fence this way' date=' but the ground wire needs to be separated from the hot wire by at least 6" (or more).[/quote'] I believe the ground (earth) / negative lug hook-up to the charger looks to be good... that part of the system is a series of 5 standard 8ft. copper coated ground rods drove in along a year-round creek. The ground rods are located in the vicinity of the charger, at the far end of the fence system. The whole system is seemingly well done... it's a professionally installed New Zealand / Kiwi style fence system. Link to comment Share on other sites More sharing options...
Members agedhorse Posted May 5, 2015 Members Share Posted May 5, 2015 Then it should be a shocking installation Link to comment Share on other sites More sharing options...
Members Telecruiser Posted May 7, 2015 Members Share Posted May 7, 2015 What happened after you regained consciousness? Link to comment Share on other sites More sharing options...
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