Power lines not dangerous...

Chuck Murcko chuck@topsail.org
Tue, 28 Aug 2001 23:35:37 -0400


Hmmm. I wonder *who* will spin this one, the power companies or those 
other guys.

If you're a believer, you're likely in more danger from your electric 
razor, hair dryer, or running your laptop on the AC adapter than from 
living near a 500 KV power line, aesthetics aside.

Note that square law doesn't apply here, the near field effects swamp 
the far field effects at 5000m wavelengths.

http://www.calpoly.edu/~dhafemei/background2.html

Excerpt:

"A typical U.S. home has the Earth's  constant magnetic field of about 
450
mG and a 60-Hz background magnetic field level (primarily not from power
lines) that ranges from 0.5 mG to 4 mG with an average value of 0.9 mG.
Five percent of the homes have fields above 2.9 mG, and 1% are above 6.6
mG.  For comparison sake, one study reports that electrical powerline
workers experience an average field of 11 mG.  Typical transmission power
lines produce average fields at distances of 30 and 60 meters as follows:

				E (V/m at 30/60 m)	B (mG at 30/60 m)
115 kV			0.07/0.01			1.7/0.4
230 kV			0.3/0.05			7.1/1.8
500 kV			1.0/0.3			12.6/3.2

As a simple example, a two wire 500 MW transmission line at 500 kV draws
500 amperes in opposing directions in the two wires.  From Ampere's law a
single wire of 500 A produces a field of 33 mG at a distance of 30 m.  If
two opposing currents of 500 A are separated by 4 meters, the field will
be 4.4 mG (in the plane of the wires).  By reducing the separation to 1
m, the field falls to 1.1 mG.  At a doubled distance of 60 m, the field
from the single conductor is 17 mG and the fields from the paired
conductors are 1.1 mG for a 4-meter separation and 0.3 mG for 1-meter
separation.  Motor and appliance electrical coils produce either magnetic
dipole or quadrupole fields that diminish as the inverse square or cube
of the distance, respectively.  Average fields at a distance of 30 cm
are: color television (7 mG), microwave (4 mG), analog clocks (15 mG),
electric razors (20 mG, 100 mG at 15 cm) and hair driers (1 mG, 300 mG at
15 cm). "

I wonder just what the field strength was in these tests? It must have 
been pretty high compared to standing under an HV transmission line, 
unless they just dropped cables into the water and used that as the 
current carrying medium. Of course that approach resembles electrocution 
more than radio.

Didn't we go through this twenty years ago with the Video Display 
Terminal (VDT) scare?

Chuck

On Tuesday, August 28, 2001, at 10:09 PM, Adam L. Beberg wrote:

> "Zebra mussels in an aquarium that were exposed to very low-frequency
> electromagnetic waves - around 60 hertz, or similar to what is emitted 
> by a
> power outlet - died within 40 days"
>
> So does this classification of 60hz EMF as a large scale biological 
> weapon
> hurt the power companies claim that's it's harmless?
>
> Wonder how they will spin this one :)
>
> - Adam L. "Duncan" Beberg
>   http://www.iit.edu/~beberg/
>   beberg@mithral.com
>
>
> Study: Radio Waves May Kill Mussels
>
> By TAMMY WEBBER, Associated Press Writer
>
> CHICAGO (AP) - Low-frequency radio waves might someday be used instead 
> of
> chemicals to control zebra mussels, which cause millions of dollars in
> damage by clogging water intake pipes at power plants and other
> installations, researchers said Tuesday.
>
> Zebra mussels in an aquarium that were exposed to very low-frequency
> electromagnetic waves - around 60 hertz, or similar to what is emitted 
> by a
> power outlet - died within 40 days, according to a study conducted by
> undergraduate students at Purdue University-Calumet in Hammond, Ind., 
> and
> presented Tuesday at an American Chemical Society meeting in Chicago.
>
> Though field trials still must be conducted, the technology appears
> promising, said Matthew F. Ryan, associate professor of chemistry at 
> Purdue.
> The technique appears to be safe for fish and other aquatic life, he 
> said.
>
> Chemicals such as chlorine and bromine have been used to kill the 
> mussels,
> but there are concerns about the safety of the substances, Ryan said.
>
> Brought to the United States in the ballast water of oceangoing ships 
> in the
> 1980s, zebra mussels spread rapidly through the Great Lakes and other 
> inland
> waterways and have caused millions in damage to power plants and boats.
>
> Gary Wege, a biologist with the U.S. Fish and Wildlife Service in 
> Minnesota,
> welcomed the study, saying that most efforts to control zebra mussels 
> have
> failed.
>
> ``If you could zap the critters right from the water, that would be 
> great,''
> Wege said.
>
> If the technique proves effective, Wege said, electrical barriers could
> block the mussels from infesting other waters.
>
> Ryan said irradiation appeared to cause zebra mussels to lose large 
> amounts
> of calcium - essential for shell health and muscle control - as well as
> sodium and potassium. Only 10 percent of unexposed mussels in another 
> tank
> died after 40 days, he said.
>
> During experiments, fish collected from the same waters and put in the 
> same
> tank as the mussels survived. Native clams did not die until being 
> exposed
> for 90 days.
>
> Ryan said the technology would have to be installed in intake pipes and 
> the
> radio waves aimed at specific spots.
>
>
>
> http://xent.com/mailman/listinfo/fork
>

Chuck Murcko
Topsail Group
http://www.topsail.org/