DC Ground Current

[loren]

I am finding dc current flowing through the ground on a dairy. There are no apparent sources of dc on the farm. I have found dc in areas where there was a lot of fill under the farm or where gas or oil pipe line ran near the farm and cathodic grounding was used but in this case I am stumped.
If I can't find the source how can I control it to get it to flow away from the animal areas?
I am mapping the gradients to find just where the current is flowing to and from but this is a long process.
Any help would be appreciated.

Loren

 

[wbalsam1]

Sounds like an equipotential plane must be established asap.

 

[loren]

I have helped many farms that have bought into this myth. You can never get the grounded surface to be equal from one end to the other. Every connection in the concrete has a small amount of resistance thus current flowing through resistance causes voltage. In several of the cases the farmers have had to completely remove the concrete and reinstall fiberglass reinforced concrete.
In one case voltage developed from a strobe light over a mile away was using the floor to find its way back to the power company. The strobe is capacitor fired and developes about 1100 volts on the neutral each time. You cant balance that out on 120/208 system and only a meger amount of went back on the power companies system neutral. By the time it reached the farm it was down to 8 volts generated over the 600 foot barn. The saving grace was the short duration of the pulses. The cell provider took immediate action and install an constantly on red light instead.
If you have an opertunity check out what I am saying the next time you have to install on in order to honor the NEC. Hook up a current source to both ends of the slab then read the voltage drop. To make it more real flood the floor with a mild salt water. You will see that the surface and the slab are just a current divider and the path of least resistance will end up being the surface to stanchions and milk pipes and drain grates.
The concept is great but the reality is there is no perfect connection. I recommended that for years as a solution then wondered why the problem only became worse, (not in all cases).
My view is not real popular but when you think about or work with it in a real life situation it will convince you.

 

[ghostbuster]

We also had DC current running through a large community swimming pool.The swimmers were getting shocks when they grabbed onto the metal handrails to get out of the pool.We found the pool gas piping DC isolators had shorted due to a recent electrical storm.
Good Luck.

 

[PharmerClem]

Hi Loren,

Just joined the site to gain some information and you may be able to fill me in on some information that I am looking for. I am a dairy farmer, but I have not totally bought into the 'myth' of stray voltage, as you stated. there is an electrical substation that is slated to be built next to my place, 1000 feet from my barn. As i have started to investigate future possibilities I am only getting what seems to be 'hype' from situations that have ended badly. I am looking for some positive examples of animals co-mingling with a situation like this. The substation will be taking 69000 volts and stepping it down to 7200 volts and distributing from there. Eventually the city will be completing a loop to serve the townships that it now services. I don't know what a substation does and I'm just looking for information. So far of the 2 'consultants' that have been referred to me, I've gotten a large roll of the eyes from my electrician and the superintendant of the reginal electrical co-op. If you could enlighten me a bit, it would be most appreciated. Thanks.