Subject: Re earth cables (fwd)
Date: Fri, 28 Aug 1998 062820 -0500 (CDT)
From: "Roy L. Beavers" <rbeavers@mail.llion.org>
To: emfguru@hotmail.com
--------------------------------------------------
Hi everybody:
As usual, Alasdair provides a very worthwhile response to Ingrid's
question about "underground power lines." As I read on down to my
initial reponse to Ingrid, I realize that I failed to state what I was
actually thinking. Please note the modification to my initial statement
that is inserted below, thus [......].
Cheerio......DO YOU KNOW SOMEONE WHO SHOULD BE ON THIS LIST?????
Roy Beavers (EMFguru)
rbeavers@llion.org..............http://www.feb.se/EMF-L/EMF-L.html
................................It is better to light a single candle ...
than to curse the darkness...............................................
---------- Forwarded message ----------
Date: Fri, 28 Aug 1998 11:16:58
From: Alasdair Philips
To: "Roy L. Beavers"
Cc: "High, Ingrid"
Subject: Re: earth cables (fwd)
Ingrid
The magnetic field from a simple single-circuit unbalanced overhead line
(as in your friends case) falls off approximately linearly with distance as
it would from a single wire (i.e. Flux = const*current/distance to wire).
>From a reasonable balanced double-circuit reverse phased overhead line it
falls off approx. inversely with dist.squared.
>From a helically wound underground cable it falls off with dist.cubed.
The magnetic field at 2.5 m from the new underground cable will be around
the same as , or less than,the field from the existing cable at 15 metres.
In practice I find it usually much lower than that, because of the
closeness of the underground conductors the cancellataion is much better
and I would estimate from the many 1000s of readings I have done that the
magnetic field at 10 metres from the existing wires will be about twice the
level of the field 2.5 metres from the new cable - i.e. their EMF levels
will fall significantly.
Also, of course, there is zero Electric field from an underground cable and
recent research is pointing to E-fields being AT LEAST as important as
B-fields. So the new cable should be better for them. Still, the further
away they can get it from their building, the better, of course.
Alasdair
=======================
At 06:16 26/08/98 -0500, guru wrote:
>
>.......The thing that I find disturbing about Ingrid's question
>below ... is that it seems to be an example of the "new thinking"
>in the power line business: Let's just put this EMF 'problem' out of
>sight.... All of us on this network know that burying the power
>cable has no real impact on the 'magnetic field' of the EMF
>charisteristics, which (though it is probably NOT the only active metric)
>nevertheless is the metric which has most clearly been identified with
>biological activity (e.g., the melatonin thesis).
[Of course, the 'engineering aspect' of creating "underground power
cables" does 'affect' what would be the "normal" magnetic field. As I
understand it, in general, it has the effect of 'compressing the field'
-- reducing its "extent." But it does not _eliminate_ the magnetic field.
Thus, the question, "Where does one install the cable with the "compressed
field?" becomes all important!
If (on the assumption that the public will not be 'aware' of the field)
the electric companies thereby install the cables ***closer*** to the
public (as in buildings, sidewalks, etc., or as described in Ingrid's
original question) they may be causing ***MORE EMF*** exposure rather than
less, even though they have responded to public desires by "burrying" the
cable!!!.......guru...]
> Still, the question
>is: is the industry reacting in response to a well thought out, properly
>engineered strategy ... or are they just trying to "put the problem out
>of sight?".......Ingrid's question below poses a situation that sounds
>like the latter......guru.......
>
>
>---------- Forwarded message ----------
>Date: Wed, 26 Aug 1998 12:05:12 +0200
>From: "High, Ingrid"
>To: "'Roy L. Beavers'"
>Subject: earth cables
>
>Hello,
>I wonder if anyone could please help me help a friend of mine who is
>worried. Their newly bought hut is built so that an overhead
>transmission line - a local 20 kV airborn feeder (if those are the right
>terms!) now passes on poles set some 4-5 metres from the corner where
>their bedroom is (not parallell with a wall but at 30 degrees angle
>approx.) - but of course high up in the air so the air distance is close
>to the 12.5 meters which is the regulation minimum in Norway.
>
>Now the electricity company is putting this into an under-earth cable,
>in a ditch following the same line as the air-cable. Then they
>apparently are allowed to keep the cables 2,5 metres away from buildings
>(this also goes for the very big long-distance transmission cables).
>
>What consequence will this have? Will radiation be less from a cable
>going underground? - The overhead one is already a single-cable line.
>Which questions should they ask from the electricity company? What
>measures can be taken to at least try to protect the closest point to
>their house?
>
>The ground where this goes is heavily waterlogged with a diffuse stream
>going under the surface, and in part in ditches - more or less following
>the line of the cable.
>
>very grateful for any input,
>Ingrid High
>
>
>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Alasdair Philips (aphilips@gn.apc.org)
Director, UK Powerwatch,
EMC Engineer and EMF-bioeffects researcher
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Archive provided courtesy of WaveGuide, http://www.wave-guide.org
Reprinted with permission of Roy Beavers, http://www.feb.se/EMF-L/EMF-L.html