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Re: ground voltage [Re: schenimann] #202996 09/04/11 04:44 PM
Joined: Jul 2004
Posts: 9,526
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gfretwell Online Content
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A little Gee Whiz info

I see 0.14 to 0.15 difference between the EGC at my house (right at the service disconnect) and the ground electrode on the pole where the transformer sits, 50' away (that is a 14ga, 50' extension cord)
The .14-.15 change seems to be whether the (120v L/N) washing machine is running. I could hear it cycle.

This is the voltage drop in 50' of service drop.

I suppose I should have looked at the neutral current.

[Linked Image from gfretwell.com]



Greg Fretwell
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Re: ground voltage [Re: schenimann] #202997 09/04/11 05:46 PM
Joined: Apr 2003
Posts: 362
Obsaleet Offline
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Is the cold water pipe cu? Do you have good ground rods? Connections. Sounds like you have a bad trans from the power co. if its happening w the main off. and your grounding of the service is not doing its job very well or is doing the whole job and your plumber friend found a little better path to ground. I just finished with a similar problem. The cold water clamp was loose and customer noticed it was arcing and his lights were blinking/flickering. I tightend it and the problem went away. After many calls and visit with the POCO they decided it was a bad trans. It seems the neighbor had a problem too and didn't know it. He paid another sparky weeks before to change his panel LOL.

Ob

Last edited by Obsaleet; 09/04/11 05:48 PM.

Choose your customers, don't let them choose you.
Re: ground voltage [Re: schenimann] #203000 09/04/11 09:31 PM
Joined: Jul 2004
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gfretwell Online Content
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I have a 15,000 gallon concrete swimming pool. You don't get a better grounding electrode than that. Add a Ufer ground, a couple thousand square feet of bonded deck and 4 ground rods and I think I am grounded pretty well.


Greg Fretwell
Re: ground voltage [Re: Obsaleet] #203037 09/05/11 11:54 PM
Joined: Sep 2011
Posts: 66
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Meadow Offline
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Originally Posted by Obsaleet
Is the cold water pipe cu? Do you have good ground rods? Connections. Sounds like you have a bad trans from the power co. if its happening w the main off. and your grounding of the service is not doing its job very well or is doing the whole job and your plumber friend found a little better path to ground. I just finished with a similar problem. The cold water clamp was loose and customer noticed it was arcing and his lights were blinking/flickering. I tightend it and the problem went away. After many calls and visit with the POCO they decided it was a bad trans. It seems the neighbor had a problem too and didn't know it. He paid another sparky weeks before to change his panel LOL.

Ob


A bad transformer does not cause elevated ground voltage. As for tightening up the the ground water clamp your just masking a dangerous hazard called an open service neutral. The op should have the poco do a double check that everything is ok on there end and also try to make an equal potential grid to eleviate the symptoms.

Re: ground voltage [Re: schenimann] #203039 09/06/11 01:26 AM
Joined: Jul 2004
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gfretwell Online Content
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There is voltage drop in any conductor, that will show up as ground shift.
When you have wye distribution there is also voltage drop in the grounded conductor on the pole. Some current has to be returning through the earth.

Since I have a 13kv distribution line that runs pretty close to a tidal river (that I assume might be as close to true ground as possible) I may extend this experiment along the line of about 20 transformers. I just need to come up with a 150 foot meter lead and a decent electrode.


Greg Fretwell
Re: ground voltage [Re: schenimann] #203041 09/06/11 01:30 AM
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gfretwell Online Content
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BTW when I did my current testing a while ago in this transformer string, I still had current in my grounded conductor to the EGC with the service disconnect open.
As I said, I probably have the best grounding electrode system in the neighborhood.


Greg Fretwell
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