Re: Electric Field vs Magnetic Fields

It's usually very expensive to block a 60 Hz magnetic field from a power
line.
Grain-oriented silicon steel is probably the most cost effective if the
field lines can be oriented to the grain of the steel.

The good news is that I'm starting to think that a lot of the problems
caused
by power lines are actually caused by RF frequencies on the line.
Unfortunately
these can also enter your house along the wiring making shielding possibly
pointless. Depending on what your house is made of, it's likely that no
60Hz electric field is coming directly through, except maybe near the
windows.
But if the house is just wood, maybe it does come through.

If you have a lot of windows facing the power line, try some kind of
grounded
conductive screens or curtains, and see if you feel better. (Also, see if
the
field is lower with the breakers off--if so you've got a wiring problem).

If you get any interference on your TV like white snow that moves up slowly
in bands,
complain to the power company and insist they check the line for sparking
insulators etc.
You could also complain over radio reception, but the TV is the best
indicator.. but
do it now before they switch to digital in February.

Bill

On Mon, Aug 18, 2008 at 2:39 PM, NO Name <[hidden email]> wrote:


[Non-text portions of this message have been removed]

Hi,
I have the same problem with power lines with a magnetic field
oscilating from 6mG to 2mG. I think I don't have almost no electric
field from the lines inside the house.

http://www.danielferres.es/fotos/foto_LAT_4.jpg

I'm also planning to look for RFs measuring and shielding.

I've found this interesting study:
"Radiofrequency exposure near high-voltage lines."
M Vignati and L Giuliani

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1469914

Thanks,
Daniel

>
> On Mon, Aug 18, 2008 at 2:39 PM, NO Name <nnc200@...> wrote:
>
> > Dear All,
> >
> > I'm trying to find some kind of shielding material for the powerlines
> > outside my home. I noticed that some materials claims to block
out magnetic
> > fields. Some block out electric fields. Which one do I need? I
just know
> > that when I take readings around my house with the CellSensor
meter I get 2

So I understand that if one wants to use aluminium survival blankets,
it's not enough.

My problem is to shield from a medium voltage powerline (the ones
that feed the houses, at 25kV I've been told). Just for a camping
tent. The powerlines are on posts, about 3-4 meters high.

Less serious problem than hight voltage power lines I know, so just
mixing in the discussion.

John.


--- In [hidden email], "Bill Bruno" <wbruno@...> wrote:
>
> It's usually very expensive to block a 60 Hz magnetic field from a
power
> line.
> Grain-oriented silicon steel is probably the most cost effective if
the
> field lines can be oriented to the grain of the steel.
>
> The good news is that I'm starting to think that a lot of the
problems
> caused
> by power lines are actually caused by RF frequencies on the line.
> Unfortunately
> these can also enter your house along the wiring making shielding
possibly
> pointless. Depending on what your house is made of, it's likely
that no
> 60Hz electric field is coming directly through, except maybe near
the
> windows.
> But if the house is just wood, maybe it does come through.
>
> If you have a lot of windows facing the power line, try some kind of
> grounded
> conductive screens or curtains, and see if you feel better. (Also,
see if
> the
> field is lower with the breakers off--if so you've got a wiring
problem).
>
> If you get any interference on your TV like white snow that moves
up slowly
> in bands,
> complain to the power company and insist they check the line for
sparking powerlines
> > outside my home. I noticed that some materials claims to block
out magnetic
> > fields. Some block out electric fields. Which one do I need? I
just know
> > that when I take readings around my house with the CellSensor
meter I get 2

>I'm trying to find some kind of shielding material for the powerlines
>outside my home. I noticed that some materials claims to block out magnetic
>fields. Some block out electric fields. Which one do I need?

Hi Nancy,
While there are magnetic shielding materials, you will have a difficult time
shielding your entire home, or even a whole room from powerlines outside.
The problem is that you will need to make a metal enclosure with the
shielding material. Easy enough for small shields, but not practical for a
whole house. I wish it was easier, but there are no shortcuts here.

Emil