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I got a call to look at a problem (I’d never been there before), where someone had felt a tingle between the ground (dirt, earth) and the metal frame of a trailer on tires with a sub panel in it. I didn’t have a ground rod or plate with me, but I put a piece of rebar in the ground and measured 12 VAC (Greenlee true RMS multimeter) between that rod and the bonded metal of the trailer, or the bond wire back to main service, or the sub panel metal etc. I Shut off feed (ACWU- 3 aluminum conductors plus ground in an armoured/ jacketed cable- this is Canada) to this sub panel and the voltage was still there! I removed the neutral, bond wire and connector from the main service ( all paths back to system ground) and the voltage went away. As soon as those connections were re-established in the main service it was back. I could even read it just by putting one probe in the dirt and the other to grounded metal! The property has a house with a 200 A service with at least one out building fed from that as well as a shop with a 400 A service which feeds the trailer with the 12VAC potential from surrounding earth back to the system ground of the 400 Amp service. I had someone shut off the main at the house the voltage went down to 10 VAC. With house back on, they shut off the entire shop- voltage again went down about 2 volts to around 10VAC. I don’t know why I didn’t try killing both services at the same time, but I’m not sure it would have mattered... It seems to me this is too high of a potential to be “normal “. Here in Canada we don’t have to re establish the ground in out buildings, unless they house livestock- the bond wire back is fine. I could however put in a ground and bond the neutral in the sub panel and that would eliminate the potential to earth there, but if there is a high impedance ground fault somewhere on one of the systems, wouldn’t that cause current flow back through the bonding conductor to the 400 amp service ground? I’m guessing it would be a pretty negligible current though... I’m thinking that since the voltage was still there with either service turned off, that it could be a power utility (POCO) issue? Am I on the right track with this? Is re establishing the ground at the sub panel the solution? What are the best ways to troubleshoot this issue? Different multimeter? Could a loose neutral connection cause this even with the mains shut off? Sorry for long winded post, but hopefully it gives enough info that I can get some helpful feedback. Thanks in advance!
Paragraphs, please. :blink:

That's brutal to read. :eek:
 

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Out in the sticks, some utilities actually use the Earth as a neutral return for THEIR power scheme.

( Then they can save on a conductor. )

This results in a voltage gradient over distance -- right out of the soil.

It's something to look into if you're out in the sticks.

Yes, in such schemes, you can't take it for granted that everywhere is at the same earth potential.

If you're not aware that this is going on -- then you are truly lost.

The above working scheme is not common in urban areas -- just the sticks.

When the money is available, the Poco can always change over.
 

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Really? I may be truly lost. Ya I think this place could be considered in the sticks- it’s way out there for sure. Probably at the end of the lines.

So are you saying this is normal enough that I should just do a ground at the trailer and bond it there and call it good? It will get rid of the tingle.
You can double check with the Poco... but I'd say you're on the right track.
 
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