Why? EMF reading at periscope with all breakers open.
- Thread starter wyreman
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- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
That kind of current in the neutral (at this point effectively ground and utility neutral function combined) is usually the result of a difference in potential between the GES and the utility transformer secondary ground or current flowing from a load on another building which shares a water pipe ground with your building.
Either one could be difficult to impossible to correct.
Either one could be difficult to impossible to correct.
How close are the neighbors?
Scenario...
say the neighbors neutral from the meter to the transformer is bad. The phone and CATV lines all share the same ground, and they usually bug on the GEC at the meter and the pole ground at the pole. If they have a bad neutral connection, they are using whatever path relative to resistance for return currents.
Some of these currents coups be coming from the phone lines, or CATV lines, through the GEC at your house, and up through the neutral at your house returning to the pole.
muddy enough??
Scenario...
say the neighbors neutral from the meter to the transformer is bad. The phone and CATV lines all share the same ground, and they usually bug on the GEC at the meter and the pole ground at the pole. If they have a bad neutral connection, they are using whatever path relative to resistance for return currents.
Some of these currents coups be coming from the phone lines, or CATV lines, through the GEC at your house, and up through the neutral at your house returning to the pole.
muddy enough??
yeah, it doesnt flow back on my GEC ... anyway, the gauss readings are always from the unbalanced flow in the bundle?
Does that mean there will always be gauss readings at a single phase loadcenter fed from a 3phase source. Many times you see a single phase panelboard with more flow on the neutral than the sum of the the phase wires.
Does that mean there will always be gauss readings at a single phase loadcenter fed from a 3phase source. Many times you see a single phase panelboard with more flow on the neutral than the sum of the the phase wires.
yeah thats what i figure as well.
The thing was, I didn't see any flow at the #4 coming from the water pipe
Its like swimming pool grid bonding for the barefoot transients
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
At risk of ridicule for acknowledging this as a legitimate thing, one of the main issues with this field of investigation is that there are a LOT of things that can set off these meters, including RF, naturally occurring magnetism in the earth, static electricity from dry air, battery powered laptop PCs, tablets and cell phones that, even when unplugged, emit pulsed wifi "pings" looking for routers, etc. etc. etc. etc. etc. The fact that these meters are the chief tool for "ghost hunters" now should be a clue as to why their readings are probably worthless. But carry on, you are entitled to you opinion and if you can get someone to pay you to walk around watching that needle dance, then more power to you!
Egg salad in a tin foil hat as they say... but anyway, I have one friend that just turns off the main when he goes to bed. Really nothing wrong with that. There is so much of this stuff around, why not mitigate it where you can. The work is simply to provide a grounded three prong outlet. There is just one reading and that is at the bed which is located directly behind the periscope
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
30 milligauss is high with the power off. My guess the current is coming in thru the community water line or thru the trany. We had a situation like this on a house. We actually dug up the water pipe near the meter (inground meters) and put in 2' of plastic pipe. This solved the problem
PaulMmn
Senior Member
- Location
- Union, KY, USA
- Occupation
- EIT - Engineer in Training, Lafayette College
Would lining the room with metal foil (and grounding it), turning the room into a Faraday cage, have any effect? This could be a metallic wallpaper.
Of course, any penetrations (ie outlets of any type) and windows screened with non-metallic screening will provide leakage.
I know there are some metallic coatings for windows, but the ones I've heard of are things like sputtered gold.
Would the same kind of shielding they use on the windows in microwave ovens work for the windows?
Are there any nearby radio station transmission towers? Signals from AM transmitters couple easily into electronic circuits. I was in one location where a tape recorder picked up an AM station!
Of course, any penetrations (ie outlets of any type) and windows screened with non-metallic screening will provide leakage.
I know there are some metallic coatings for windows, but the ones I've heard of are things like sputtered gold.
Would the same kind of shielding they use on the windows in microwave ovens work for the windows?
Are there any nearby radio station transmission towers? Signals from AM transmitters couple easily into electronic circuits. I was in one location where a tape recorder picked up an AM station!
the trany?
turning off the mains wouldn't help in this case
solved the problem... for you!
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
1. No. Kirchoff's Laws tell us that unless there is another current carrying conductor somewhere that we do not know about, the net current in the feeder must be balanced, No current in the ungrounded wires means no current in the grounded wire either.
2. I don't. If you mean more current in the neutral than the vector sum of the ungrounded, then it is not possible. If you mean more current in the neutral than the difference between the two ungrounded conductors, that will happen with a 2 out of 3 phase source or when there is low power factor current on one side of a 120/240 single phase 3 wire.
If there is no current in the GES at all and the breakers are open then there has to be another source for the current somewhere. Among the possibilities are cable TV/Internet shield, telephone ground rod, bonded interior plumbing not connected electrically to the water pipe, etc.
If POCO has high earth currents (because of a compromised or inadequate distribution neutral?) then two points fifty feet apart in the vicinity of the house could have a voltage difference measure with isolated ground probes) of several volts. This is enough to drive current through your service neutral.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
It's short for transformer, like genny is for generator.
What I want to know is "periscope." Service mast?
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
190828-1519 EDT
wyreman:
You provided no quantitative data, unless the displayed meter reading is it. But still we don't know the range selected.
At my water line, which is my ground rod, a 1 or 1.25" copper tube, my 1" dia gauss probe reads 25 milligauss next to the copper tube at this moment of time when that electrode current is around 1/2 A. When next to the #6 wire from the main panel to the water pipe the reading is 75 milligauss. A radius difference results in the two different readings. The general noise level with this sensing coil about 6 feet away is around 1 milligauss which is mostly meter noise.
At the pole of the pole transformer next to the wood sheath over the pole transformer GEC I read about 75 milligauss. About the same as in the house. Under my 3 phase delta primary lines, no ground wire, only 3 wires, I read about 2.5 milligauss. This 2.5 may still be a noise value, like radio stations.
When your main breaker is open, then there is no load current from the home. Is anything attached to the power lines before the main disconnect. For example a transient limiter, or power factor correction capacitors.
You need to look for all wires or conductors that could cause the apparent current indicated by the gauss meter. Use the gauss meter to look for where this current might be flowing from.
.
wyreman:
You provided no quantitative data, unless the displayed meter reading is it. But still we don't know the range selected.
At my water line, which is my ground rod, a 1 or 1.25" copper tube, my 1" dia gauss probe reads 25 milligauss next to the copper tube at this moment of time when that electrode current is around 1/2 A. When next to the #6 wire from the main panel to the water pipe the reading is 75 milligauss. A radius difference results in the two different readings. The general noise level with this sensing coil about 6 feet away is around 1 milligauss which is mostly meter noise.
At the pole of the pole transformer next to the wood sheath over the pole transformer GEC I read about 75 milligauss. About the same as in the house. Under my 3 phase delta primary lines, no ground wire, only 3 wires, I read about 2.5 milligauss. This 2.5 may still be a noise value, like radio stations.
When your main breaker is open, then there is no load current from the home. Is anything attached to the power lines before the main disconnect. For example a transient limiter, or power factor correction capacitors.
You need to look for all wires or conductors that could cause the apparent current indicated by the gauss meter. Use the gauss meter to look for where this current might be flowing from.
.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
:thumbsup:
Think of the Gaussmeter as an uncalibrated clamp-on ammeter without the clamp. :happyyes:
The OP also said he measured 1 Amp on the utility neutral with the main breaker off. Isn't that quantitative enough for you?
Think of the Gaussmeter as an uncalibrated clamp-on ammeter without the clamp. :happyyes:
The OP also said he measured 1 Amp on the utility neutral with the main breaker off. Isn't that quantitative enough for you?
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
190828-2042 EDT
GoldDigger:
No way quantitative enough when the thread subject is gauss reading, and that was what he was called to look at. Having the current vs gauss reading is useful. The gauss reading will vary inversely in some manner with radius from the current, which you know, others may not.
Further gauss readings can possibly allow him to somewhat trace were the stray current is flowing.
.
GoldDigger:
No way quantitative enough when the thread subject is gauss reading, and that was what he was called to look at. Having the current vs gauss reading is useful. The gauss reading will vary inversely in some manner with radius from the current, which you know, others may not.
Further gauss readings can possibly allow him to somewhat trace were the stray current is flowing.
.
grich
Senior Member
- Location
- MP89.5, Mason City Subdivision
- Occupation
- Broadcast Engineer
I chuckled a little seeing the "$3" shorthand in the first post.
I'm not an electrician, but I learned what that symbol means in junior high shop class in 1976. I wonder if today's junior high kids learn electrical blueprint symbols? Or even have shop class?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Not sure if it was the trany. Downstream in someone else's home is where the issue may have been. The current could not follow the path back to the house because of the plastic pipe we had inserted.
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