Reply-To: "Don Kelly"
From: "Don Kelly"
Subject: Re: Interference from power lines
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Date: Mon, 06 Jan 2003 18:31:44 GMT
NNTP-Posting-Date: Mon, 06 Jan 2003 11:31:44 MST
Organization: Shaw Residential Internet
"DarkMatter" wrote in message
> On Mon, 6 Jan 2003 08:34:07 -0500, "Charles Perry"
> Gave us:
> >"Kevin McMurtrie" wrote in message
> >> In article
> >> Ask LIPA to fix it. There's something wrong with their wiring that's
> >> creating a long range electromagnetic field from the AC power. When
> >> everything is working correctly, the power lines are side by side and
> >> carrying matching amounts of power in and out. When they aren't, the
> >> magnetic fields don't cancel.
> >No, even when all three phases of an overhead line are carrying the same
> >current the magnetic field is not zero. They do not all cancel due to
> >geometry of the construction.
> >Charles Perry P.E.
> Depending on what plane one is in when taking the measurements, they
> might *appear* quite diminished in one location, when compared to
> another. Directly above or below the parallel lines, the fields would
> be distinct, and separate. In the same plane that the lines traverse
> at a parallel height, one might only see the field strength of the
> nearest line.
Actually, at any location , the magnetic field is due to all the currents in
the vicinity. There will be no distinct and separate fields although one
phase may dominate depending on the geometry of the situation. Each phase
will contribute to the total field at any point, depending on the distance
> Sort of like how directional antennas work.
Not really, considering that wavelength considerations are implicit in
directional antenna design and behaviour. At 60 Hz the distances involved
are a negligable fraction of a wave length.
> But differences in the currents in them would have no effect.
> Magnetic fields pass through planets. If we could "cancel" them with
> opposing fields, we would probably be flying magnetic hovercraft by
What do you mean by this? Since all currents will be involved in the field
at any point in the region, differences in currents will definitely have an
There will be a cancellation effect for three phase -this will occur at
points equidistant from the three conductors (for balanced 3 phase). In
general, the fields from a three phase system will decrease with distance
faster than those of single phase systems because of such cancellation
remove the urine to answer