A voltage to ground mystery.

Glenn Ashmore wrote:
Well this is in the Piedmont of Georgia so the pipe is definitely burried in
1,000' of red clay. :)

The thing I can't figure out is the copper pipe comes out of the ground
right at the puddle so it should be well grounded but if you use a VOM
between the faucet and a nail stuck into the mud a foot from the base it
reads 25V!

--
Glenn Ashmore
Click to expand...

Move the nail further ot to see if the voltage goes up even more. if
you can get 100 to 120 volts if you can and connect a 20 watt or higher
light bulb and see if it lights. There are still a few outdated power
distribution systems that use "Earth return", meaning they feed the one
side of the transformer primary and ground the other side and let the
return current flow through the ground. These were used in rural areas
and have mostly been replaced due to this kind of problem.

--
Former professional electron wrangler.

Michael A. Terrell
Central Florida
 
"Fred Bloggs" <nospam@nospam.com> wrote in message
news:424917F5.3040304@nospam.com...
The power grid is circulating current through the GND returns at the two
different points of connection to the grid- one at the origin of the
copper pipe and the other at the construction site. You have created a
nice short-circuit with that pipe and the circulating current can be very
large. You will have no option except to install a section of
non-conducting plastic pipe at the construction site, make the faucet and
its T-section riser plastic also.

I agree with Fred. It sounds as though with an o'head single phase power
Click to expand...
system there is voltage difference between the ground at the power
transformer and other power system grounds. The copper pipe is providing a
convenient path for some of the ground current?
Have seen that before when a neighbour's buried power service became damaged
and had a bad leak to ground. Our ground and basement appliances became
noticeably 'tingly' due to current leaking through the ground to our
grounded neutral. It disappeared when his service was repaired.
 
On Mon, 28 Mar 2005 09:42:21 -0500, "Glenn Ashmore" <gashmore@cox.net>
wrote:

This is more of an electricity question than electronic but: We just
finished running water and power to a new construction site. Water is in a
copper pipe run about 1,000' through the woods burried about 2' deep that
just ends in a 2' vertical piece with a faucet on top. Power runs parallel
to the pipe about 100' away to a transformer on a pole at the construction
end.

The mystery is that there is a 25-30VAC difference between the faucet and
the mud puddle below it. Touch the faucet without wearing rubber boots and
you get shocked! I can see how a current might be induced into the pipe as
it runs along the power line but how can there be a potential between the
ends of a 24" copper pipe???
Click to expand...
---
There isn't, there's a differential between the secondary of a
transformer (the 1000 feet of pipe) running in parallel with the
primary of the transformer (the power line) and the puddle.

--
John Fields
 
"Glenn Ashmore" <gashmore@cox.net> wrote in message
news:gJU1e.80145$SF.30120@lakeread08...
This is more of an electricity question than electronic but: We just
finished running water and power to a new construction site. Water is in a
copper pipe run about 1,000' through the woods burried about 2' deep that
just ends in a 2' vertical piece with a faucet on top. Power runs parallel
to the pipe about 100' away to a transformer on a pole at the construction
end.

The mystery is that there is a 25-30VAC difference between the faucet and
the mud puddle below it. Touch the faucet without wearing rubber boots and
you get shocked! I can see how a current might be induced into the pipe as
it runs along the power line but how can there be a potential between the
ends of a 24" copper pipe???
Click to expand...

Given the physical situation you describe and the way
power *should* be connected and grounded, the AC
voltage you report should not occur. Something is
very wrong. I suggest you call whoever is responsible
for that power installation to fix it, and if they will not or
are unable to discover what is wrong, get an independent
qualified electrician to look at it.

There may have been another power line contacted by
the pipe when it was laid. The situation could become
more dangerous.

Do not use your hands as "got AC volts" testers anymore.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.
 
"Glenn Ashmore" <gashmore@cox.net> wrote in message
news:gJU1e.80145$SF.30120@lakeread08...
This is more of an electricity question than electronic but: We just
finished running water and power to a new construction site. Water is in
a
copper pipe run about 1,000' through the woods burried about 2' deep that
just ends in a 2' vertical piece with a faucet on top. Power runs
parallel
to the pipe about 100' away to a transformer on a pole at the construction
end.

The mystery is that there is a 25-30VAC difference between the faucet and
the mud puddle below it. Touch the faucet without wearing rubber boots
and
you get shocked! I can see how a current might be induced into the pipe
as
it runs along the power line but how can there be a potential between the
ends of a 24" copper pipe???

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com
Click to expand...
I had a similar problem once with a ground level bathroom. When starting the
shower, no problem but when you turned it off you got a slight tingle
(shower floor then being wet). Rang the local electrical contractor who said
it was not an uncommon problem for that area and there was no answer for it.
He mentioned that it may have something to do with the clay soil - if that
is of any help.

I as well, couldn't see the difference in potential between the taps/faucets
and ground.

Cheers.
 
Jamie wrote:
i have a friend, his neighbor had problems when the furnace was running.
my friend would get a mile shock when touching his sink!
Click to expand...

WOW! A whole mile? ;)

--
Former professional electron wrangler.

Michael A. Terrell
Central Florida
 
On Mon, 28 Mar 2005 08:57:21 -0800, Larry Brasfield wrote:
"John Fields" <jfields@austininstruments.com> wrote in message
On Mon, 28 Mar 2005 09:42:21 -0500, "Glenn Ashmore" <gashmore@cox.net

This is more of an electricity question than electronic but: We just
finished running water and power to a new construction site. Water is in a
copper pipe run about 1,000' through the woods burried about 2' deep that
just ends in a 2' vertical piece with a faucet on top. Power runs parallel
to the pipe about 100' away to a transformer on a pole at the construction
end.
---
There isn't, there's a differential between the secondary of a
transformer (the 1000 feet of pipe) running in parallel with the
primary of the transformer (the power line) and the puddle.

There are two difficulties with that analysis.

1. The currents flowing in the power cable should be somewhat
well balanced and they flow within an inch or two of each other.
The conductors carrying those currents will have some degree
of twisting, tending to cancel when considering the net coupling
to any single parallel conductor. Magnetic coupling coefficients
sufficient to effect a 30/240 stepdown are highly improbable.
Click to expand...
Don't forget the 900' of pipe running parallel to the hiline upstream
of the transformer.

Cheers!
Rich
 
Terry wrote:

"Fred Bloggs" <nospam@nospam.com> wrote in message
news:424917F5.3040304@nospam.com...

The power grid is circulating current through the GND returns at the two
different points of connection to the grid- one at the origin of the
copper pipe and the other at the construction site. You have created a
nice short-circuit with that pipe and the circulating current can be very
large. You will have no option except to install a section of
non-conducting plastic pipe at the construction site, make the faucet and
its T-section riser plastic also.


I agree with Fred. It sounds as though with an o'head single phase power
system there is voltage difference between the ground at the power
transformer and other power system grounds. The copper pipe is providing a
convenient path for some of the ground current?
Have seen that before when a neighbour's buried power service became damaged
and had a bad leak to ground. Our ground and basement appliances became
noticeably 'tingly' due to current leaking through the ground to our
grounded neutral. It disappeared when his service was repaired.


i have a friend, his neighbor had problems when the furnace was running.
Click to expand...
my friend would get a mile shock when touching his sink!

there was a ground problem due to the soil around there.
 
"John Fields" <jfields@austininstruments.com> wrote in message
news:ls7g419rupl4j9ar8d5f9lbrjjnb8bjrop@4ax.com...
On Mon, 28 Mar 2005 09:42:21 -0500, "Glenn Ashmore" <gashmore@cox.net
wrote:

This is more of an electricity question than electronic but: We just
finished running water and power to a new construction site. Water is in a
copper pipe run about 1,000' through the woods burried about 2' deep that
just ends in a 2' vertical piece with a faucet on top. Power runs parallel
to the pipe about 100' away to a transformer on a pole at the construction
end.

The mystery is that there is a 25-30VAC difference between the faucet and
the mud puddle below it. Touch the faucet without wearing rubber boots and
you get shocked! I can see how a current might be induced into the pipe as
it runs along the power line but how can there be a potential between the
ends of a 24" copper pipe???

---
There isn't, there's a differential between the secondary of a
transformer (the 1000 feet of pipe) running in parallel with the
primary of the transformer (the power line) and the puddle.
Click to expand...

There are two difficulties with that analysis.

1. The currents flowing in the power cable should be somewhat
well balanced and they flow within an inch or two of each other.
The conductors carrying those currents will have some degree
of twisting, tending to cancel when considering the net coupling
to any single parallel conductor. Magnetic coupling coefficients
sufficient to effect a 30/240 stepdown are highly improbable.

2. The copper pipe may be in the same trench, but it should be
separated by some distance. (I forget the code requirement,
but enforcing it is part of the reason an inspection is required
before the trench is filled in.) Unless the pipe is jacketed, (a
condition not stated by the OP), the fill around it will further
serve to reduce the coupling from nearby power conductors.

As I stated in another post, the OP's observations could easily
be due to an unsafe condition that should be investigated by
a competent person on site, who can discover the additional
facts necessary to explain and correct the problem. This is
true regardless of any debate that might occur regarding the
magnetic coupling. I should hope that Mr. Fields is able to
concur with that view, even if he disagrees with my points
about magnetic coupling.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.
 
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