From all of the readings I have taken (mostly in KY, WV, and OH) I would say
3 mG is about average. 4mG would not be very high. What you need to remember is that the field strength in the house can often be much higher. Magnetic fields are caused by current, not voltage. The higher the current, and the closer to the source, the higher the fields. Your low voltage wiring in your home will have relatively high current levels and you will much closer to them. Also, if the feeder outside is three phase, you will see a magnetic field related to the unbalance of the current and also related to the asymmetry of the construction. These effects tend to reduce the field strength from three phase sources.
Right on Roy... I dont think Chas Perry has your background or tenure in academia.. he misses the finer points completely... and has NO clue about resistance inversion in vault shielding for open space landing sites...no clue. He may have gotten his PE in a box of cracker jacks.
Ahhh HATES to agree with Chas Perry, because he was so far south and pig headed on the back emf issue, but I think he is right on with with his loose primary ground theory and the house current then in the water lines.. that would provide all the strange readings and the variables too...as the neutral ground waxed and waned... the neighbors would have had a similar problem, then going to bed and shutting it down right after the evenin' noose.. our correspondents house piping would be an even better ground due less flow in the neighbors water pipe grounding 'grids'.,, all connected to the same water mains as they were.
Although I agree with what you say, shouldn't the meter pick up readings from the wiring in the house? If it should, then the highest reading I get is still from the road. I have monitored the readings since the fix, and they are almost exactly 10% of what they were before, with all the same fluctuations and peaks/fall times. Regardless of the electric theory which runs the cables outside, the fact is as far as I can tell, the readings I have taken at various times should surely be accurate?
Thanks for your reply. The only minor problem is that I'm told there is no water mains down with the electric cables, it runs in the back of my house instead ;) These cables are at the front.
Nevertheless, if the neutral current was finding a *different* path from the cables, there would be imbalance and a resulting field. This is why all the cables are normally run together. The field from each will cancel out the others and not propagate very far. So anything such as a loose connection that caused some of the current to be diverted through another path (such as water line or another cable around the block), could have been the culprit.
I spoke to the manager of the electric company today. I must confess I didn't quite understand the cause of the problem, the techno-babble was beyond me. But he said the problem was indeed with the neutral connection at the local sub-station. He did mention there were connection problems, so I would assume it related to that. It was causing extremely high levels of current to flow down my street when it should of been more distributed. The sub-station is around 200 yards away from my house.
I have not taken readings in my current home. In the 1990s, I took measurements in 50 or so homes and a dozen or so businesses. Part of the job I had at the time.
Sounds like the unbalance current from several feeders was feeding back on the neutral of the feeder in front of your house because it was the one with a good connection. Neutrals from different feeders are often interconnected.
In rural circuits you can use this fact to help locate broken neutrals (often very hard to find since the line might cross many tree covered mountains). If you had two feeders from a station for example and branches from these feeders interconnected at open points (with the neutrals tied together) you could look for a higher than expected neutral current. You then knew neutral current from the other feeder was coming back on that feeder. A few measurements and you can narrow down the location of the break. Then it becomes an excercise in hiking ;-)
It doesn't work so well in urban areas where this is usually a much greater number of interconnections.
You dont understand... your house ground is directly connected to the water supply or the gas meter with a jumper across the meter..but more likely to a water line at the copper or steel supply to the house. that of course grounds to the entire city water main loop.
Your ground very well could be, but not necessarily is, tied to your neutral at the panel... as well as the primary neutral from the utility company...if the utility companies ground got jiggy (loose and partially conducting_, then current would flow to your ground at the water lines... creating the effects Chas discussed.
Measure amperage through the wire you have running to ground ..attached to a water line most likely.. if you find amperage in that then you will find the neutral bonded to it in your panel, and some of the flow that was intended solely for the neutral is going to your ground.. and that is creating the localized effects Chas mentioned so brilliantly.
At night then or as the neigbors loads change, the current in the water lines (used as a grounded neutral in this case to to common bonding in the panel) would vary...and this would give the variable reads you are discussing.
You could all a few neighbors to engage with you in a test, by tesing with some of thier heavy 120v loads, all at once...then again with the loads off.
If you get corresponding higher reads on your EMF radiation meter with their loads you will have confirmed Chas's theory.
Frankly after reading his analysis I dont see what else it could be.
Thanks to all of you who posted in this thread. I unfortunately have no new information to give at this stage, so I'll sign off on this one. The discussion is now more technical than my brain can handle anyway :)
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