Residual 60 Hz magnetic intensity

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
220622-2202 EDT

What level of residual magnetic field intensity have you measured in your home, measured in 1/1000 of a gauss, and at 60 Hz?

Does this change much in going into your yard? What is it in the region of your power lines?

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paulengr

Senior Member
220622-2202 EDT

What level of residual magnetic field intensity have you measured in your home, measured in 1/1000 of a gauss, and at 60 Hz?

Does this change much in going into your yard? What is it in the region of your power lines?

.

Why does it matter? What level and frequency has shown to have any real medical effect? Can you prove any biological effect or harm?

Tests have been done on this stuff for years. iEEE has extensive standards backed uo by tons of research data. Fir example have you seen what transmission li e workers do? The health effects have been studied both short and long term.


So, why does it matter?

Donate your PKE meter to the local ghost hunters.
 

tom baker

First Chief Moderator
Staff member
One of our forum mods, Karl Riley, wrote the book on EMFs and invented a gaussmeter. His research indicates high levels of EMFs are caused by electricians making wiring violations of the NEC. Search for his video on you tube.
Are you familiar with the inverse square law?
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
220622-2202 EDT

What level of residual magnetic field intensity have you measured in your home, measured in 1/1000 of a gauss, and at 60 Hz?

Does this change much in going into your yard? What is it in the region of your power lines?

.
What do you mean by residual? After what event am I supposed to measure?
My 'yard is 1/4 mile to the closest neighbor. with no utility powerline between us.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
220623-2049 EST

paulengr:

In my post where did I say anything about health?

But unbalanced wires are a problem. At my daughter's home my cousin's son was playing his electric guitar, and there was substantial unwanted 60 and/or 120 Hz hum. This was obviously a result of the unbalanced current path relative to the air conditioner.


tom baker:

The inverse square law relates to a point source. With a moderately long straight wire the the relationship is 1 / radius from the line.

See page 337 and the field of a long straight wire in "Principles of Electrical Engineering", by Timbre and Bush, John Wiley, third edition 1940. Note who Bush was.

The equation provided is B = 2*u*I / r where B is in gauss, I in abamperes, and r in centimeters.


ptonsparky:

On your farm and assuming no conductive elements ( pipes for example ) it would be interesting to know what level of 60 Hz magnetic fields you could sense.

With my present tuned magnetic sensor. I need to go out into our Waterloo Recreation area, and see what levels I read.

In previous experiments in this area I measured the direction of ground current, but with no 60 Hz filter, and the direction was not parallel to the high voltage tie line between Detroit Edison and Consumers Power.

I only have an AC powered scope, and this grossly changes the meter reading when making the low level measurements when I connect the scope to the tuned circuit. So at the moment I can not totally verify that the meter reading only without scope is of a 60 Hz sine wave.

.
 

Fred B

Senior Member
Location
Upstate, NY
Occupation
Electrician
So Gar, you find high level EMF in a home, are you making "fixes" to reduce the EMF present? How much can you really reduce? What was the solution on the AC unit that presumably created the imbalance and EMF, and unwanted interference? Did you confirm the ac as cause?
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
The field from a long straight wire falls off as 1/r, where r is the perpendicular distance from the wire.
The field from two long straight wires separated by distance a and carrying equal and opposite current, on the other hand, falls off more rapidly. I think it is proportional to 1/(r/a)2 when r is large compared to a.
(I have had a lot of difficulty confirming that inverse square dependence. Does anyone have an authoritative source?)
So the balanced currents need to be carried in wires that follow as closely as possible the same path.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
220624-0844 EDT

GoldDigger:

The inverse square relationship is based on a single point source of energy radiating uniformity in all directions. For example the sun or an ordinary incandescent light bulb. The surface area of a sphere varies as the square of the radius, and so the power density of a lossless energy source will also vary in accordance with the inverse square law.

In post #5 I provided a reference for the derivation of the 1/Radius law for a straight wire.


Fred B:

I did not do anything about the problem in my daughter's home because she did not want to bother. In some fashion it had to do with current flowing on the cooling duct.


tom baker:

I don't have Riley's book.


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wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
(I have had a lot of difficulty confirming that inverse square dependence. Does anyone have an authoritative source?)
The fields are additive (yes?) so isn't the two opposing currents solution directly derivable from the single current solution? Just like the dipole solution is derivable from the point solution? In both cases the exponent on r decreases by 1, as it is akin to a differentiation, being the difference in the two opposing effects.

Cheers, Wayne
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
220624-1436 EDT

ptonsparky:

With magnetic field measurement in close proximity to the heating ( air conditioning ) duct I could detect current flow there when the air conditioning breaker was on.

.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
The fields are additive (yes?) so isn't the two opposing currents solution directly derivable from the single current solution? Just like the dipole solution is derivable from the point solution? In both cases the exponent on r decreases by 1, as it is akin to a differentiation, being the difference in the two opposing effects.

Cheers, Wayne
I figured that, but wanted to be more convinced. :) It would also be nice to get the actual coefficients, as I am lazy.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
220624-1640 EDT

GoldDigger:

See

For 1 A and at a radius of 1 meter from a single straight wire the flux density in gauss is 0.02 or 20 milligauss.

Consider two parallel wires spaced 1 cm apart ( 2.54 cm = 1" and this is the exact value, and 1 meter = 39.34" ). Make the current the exact same value in both wires, but the directions are opposite. Then the net field intensity at 1 meter when the plane of the two wires contains the point of flux measurement is

B = Ia * 20 * ( 1/1000 - 1/1010 ) = Ia * 20 * ( 1010 - 1000 ) / 1000 * 1010 = Ia * 20 * 10^-5 = very small . Or at 1 A = 20 * 0.01 = 0.2 milligauss compared to 20 milligaus for the single wire.

If you rotate the two wires by 90 deg, then the level drops to 0.

Check my math to see if I made any mistakes.

.
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
I walked through out the house, ground floor and basement. 1.7 to 2 mg. Outside around the house, under the primary, over the service laterals, and the well. VFD.

No significant change unless I was within 8" of service panels, conduits or cord ends with loads. As expected.

I did not zero the meter
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
220624-2049 EDT

ptonsparky:

I do not control ( tell ) my daughter what to do. She's 62 years old and has to and does control her own life. Suggestions I do make, but that is all I do. Solving the unwanted neutral problem was nothing of importance to her. She now has a new air conditioner. Will this eliminate the problem I don't know. Even worse is her main panel. No main breaker. So you can not de-energize the main panel without pulling the meter. In my opinion the city should never have allowed such a main panel, but there are many in project areas. When I built my home I put in a Sq-D QO main panel with a pullout main fuse block. When that block is pulled there is about a 6" air gap between the power source at th top of the panel and the panel breakers. Plenty safe to work in the panel when the fuse block is pulled.

My daughter's husband works for Dominos at the main headquarters, but because of Covid he has worked at home much of the time. My daughter has her own business in their home as well and this consumes most of the basement, and a room or two on the second floor. Their home is somewhat over 2000 sq-ft. Not really big enough for all of what is done there. But they are not inclined to move.

My son bought about 20 acres west of town. He is much happier with that country location, and he has many toys to play with. One toy is full size farm tractor with all sorts of attachments.

.
 

mtnelect

HVAC Contractor
Location
Southern California
Occupation
Contractor
Questions have been raised about the possible health effects of 60-Hertz (power frequency) electric and magnetic fields (EMF), which are found wherever you have electric power.
 

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