hot-handing HV transmission line - why need the farady suit?

J

John VanCleve

Jan 1, 1970
0
Hi everyone,

I just watched the discovery channel clip of a helicopter crew doing
live work on a 500KV powerline (search youtube for "Like a Bird on a
Wire" to see similar clip) and I can't figure something out. They
said that you don't see birds sitting on 500kv lines because they
would feel discomfort from the "induction" of the lines. That's why
the crew wears metal-mesh faraday suits to prevent them from feeling
"discomfort".

I'm sure the suits also provide safety in case they have a mishap
bonding on, but I don't see how the induction from the current in the
line could cause a physically detectable sensation. Is what they
really mean that the guy's body has enough capacitance to the earth
below to pass current from the line? Or can a 60 HZ magnetic field (if
strong enough) actually be felt by the human body? I can't figure it
out…

Cheers…

J

Jeroen Belleman

Jan 1, 1970
0
Tim said:
Reporters (and documentary writers) don't know much about anything but
reporting. "Induction" is an electrical phenomenon. "discomfort" is an
electrical phenomenon. Hence, all electrical phenomenon must be from
induction.

The word "induction" also applies to charges moving in an object
under the influence of an electric field.

Estimating a typical human to have about 100pF capacitance, 500kV
at 50Hz would result in 15mA at the point of contact. That's enough
to cause discomfort.

Jeroen Belleman

D

Dirk Bruere at NeoPax

Jan 1, 1970
0
Jeroen said:
The word "induction" also applies to charges moving in an object
under the influence of an electric field.

Estimating a typical human to have about 100pF capacitance, 500kV
at 50Hz would result in 15mA at the point of contact. That's enough
to cause discomfort.

Jeroen Belleman

diploma...

R

Rich Grise

Jan 1, 1970
0
The word "induction" also applies to charges moving in an object under the
influence of an electric field.

Estimating a typical human to have about 100pF capacitance, 500kV at 50Hz
would result in 15mA at the point of contact. That's enough to cause
discomfort.

But, aren't the UHV hi-lines DC? I saw that chopper thing and wonder if
500 KVAC would maintain an arc like that?

Thanks,
Rich

B

Baron

Jan 1, 1970
0
Besides the danger of induced currents (I was told in college
that 10mA of current through the heart is sufficient to be fatal), I
have also seen documentaries of adverse health effects in living
things (i.e. cattle, people, trees) that were in constant exposure to
such high-power lines. Although I have never witnessed any, I have
heard of people setting up illegal ground-level inductors under these
high-power lines to "steal" electricity.

I have a colleague that lives in a bungalow almost directly under a
500Kv power line. The fluorescent tubes in his kitchen never go out
even when turned off at the switch, and some not all the CFL lights
have a constant glow.

My 2cw

P

PeterD

Jan 1, 1970
0
I have a colleague that lives in a bungalow almost directly under a
500Kv power line. The fluorescent tubes in his kitchen never go out
even when turned off at the switch, and some not all the CFL lights
have a constant glow.

Doesn't have any children, does he? <bg>

F

Frithiof Jensen

Jan 1, 1970
0
PeterD said:
Doesn't have any children, does he? <bg>

They glow too ;-)

B

Jan 1, 1970
0
F

Frithiof Jensen

Jan 1, 1970
0
Baron said:
Yes ! One of each.

?? !

The glow-in-the-dark-child --> extreme radiation i.e. Chernobyl jokes.

O

[email protected]

Jan 1, 1970
0
Therefore, in conclusion, I would have to concur that a Faraday
suit would go a long way to protect one's health if not one's life.

Studies of trees along the Navy's ELF sites in Michigan showed a
growth rate increase and overall healthier trees close to the antenna
line, which was on telephone poles. It has since been dismantled.

Steve

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