lightning

In article <[email hidden]>, [email hidden] says...

Quoted message said:

Dorfus Dippintush said:

The safest place is under large power lines. you are protected in a 30
degree zone under the power line. The safest place is in a switchyard.

From http://www.lightningsafety.com/nlsi_pls/decision_tree_people.html:

"*Unsafe* places are near metal or water; under trees; on hills; near
electrical/electronics equipment."

If lightning strikes a tree/tower/whatever near you, the potential of
the earth at the base of the tower rises. The potential decreases as you
get further away from the base. So if you have two feet on the ground,
and one foot is farther from the tower's base than the other foot, you
have a potential difference between your feet. Now electricity tries to
go through you (up one leg, down the other). That's a bad thing.

A reference describing the same thing I just tried to describe:
http://science.howstuffworks.com/lightning8.htm

Good website, thanks. I found this entry there:

"The tallest objects in a storm don't always get struck by lightning. It's
true that taller objects are closer to the clouds, but as discussed
previously, lightning can strike the ground at a close distance to a tall
object. Taller objects may have a higher possibility of a strike, but
where lightning is concerned, the strike path is not predictable."

Zog The Undeniable said:

The best advice is to head for a valley or lie in a ditch,
well away from the bike.

Don't lie down. In many situations there's more danger from
ground current than from a direct strike. So get away from
tall things. Then crouch down with head low and (most
importantly) feet together.

John

dvt said:

Dorfus Dippintush said:

dvt said:

Dorfus Dippintush wrote:
> The safest place is under large power lines. you are protected in a
> 30 degree zone under the power line. The safest place is in a
> switchyard.

From http://www.lightningsafety.com/nlsi_pls/decision_tree_people.html:

"*Unsafe* places are near metal or water; under trees; on hills; near
electrical/electronics equipment."

If lightning strikes a tree/tower/whatever near you, the potential of
the earth at the base of the tower rises. The potential decreases as
you get further away from the base. So if you have two feet on the
ground, and one foot is farther from the tower's base than the other
foot, you have a potential difference between your feet. Now
electricity tries to go through you (up one leg, down the other).
That's a bad thing.

A reference describing the same thing I just tried to describe:
http://science.howstuffworks.com/lightning8.htm

A switchyard has earthing conductors that run underground that reduce
such effects. That's why it's the safest place to be.

I can believe that a switchyard has a good grounding system. I don't
have first-hand experience, but it seems plausible. But that doesn't fix
your first sentence: "The safest place is under large power lines." I
think that's bad advice.

Above large power lines you have one or two large conductors, they are
there especially to to take lighting strikes. They protect the current
carrying conductors below from lightning. Do some research. Talk to
someone that knows transmission lines.

http://richoq.home.mindspring.com/transmission.htm

http://concise.britannica.com/ebc/art-19392

Dorfus

Dorfus Dippintush said:

dvt said:

I can believe that a switchyard has a good grounding system. I don't
have first-hand experience, but it seems plausible. But that doesn't fix
your first sentence: "The safest place is under large power lines." I
think that's bad advice.

Above large power lines you have one or two large conductors, they are
there especially to to take lighting strikes. They protect the current
carrying conductors below from lightning. Do some research. Talk to
someone that knows transmission lines.

http://richoq.home.mindspring.com/transmission.htm

http://concise.britannica.com/ebc/art-19392

Dorfus

Lightning is unpredictable. If lightning strikes a
tower above you, the shortest path to ground will be
through the grounding strap of the tower. But that
doesn't guarantee that some portion of the electric
current will not also take the path through you.

In the little picture about lightning rods posted earlier,
the cone of protection is shown with a little cartoon
house inside it. Not a little cartoon person standing
next to the tower base. It is, of course, a cartoon,
but lightning rods are designed to protect structures
(and people within the structures), not people standing
outside in an electrical storm.

Ben

Dorfus Dippintush said:

dvt said:

Dorfus Dippintush wrote:

Quoted message said:

Quoted message said:

Quoted message said:

A switchyard has earthing conductors that run underground that reduce
such effects. That's why it's the safest place to be.

I can believe that a switchyard has a good grounding system. I don't
have first-hand experience, but it seems plausible.

I should add that I don't know if the grounding system is sufficient to
keep potential differences low within the switchyard. And since a
switchyard is prime territory for lightning strikes and concomitant
mechanical damage, I don't know if a switchyard is a safe place during a
lightning storm.

Quoted message said:

Quoted message said:

But that doesn't
fix your first sentence: "The safest place is under large power
lines." I think that's bad advice.

Quoted message said:

Above large power lines you have one or two large conductors, they are
there especially to to take lighting strikes. They protect the current
carrying conductors below from lightning.

And where do those large conductors lead? To an earth point somewhere
near the poles. And where are you standing in the case you propose?
Somewhere near the poles. Sounds like a bad idea to me.

Quoted message said:

Do some research. Talk to someone that knows transmission lines.

Am I having a conversation with "someone that knows transmission lines"
in this exchange?

Quoted message said:

http://richoq.home.mindspring.com/transmission.htm

http://concise.britannica.com/ebc/art-19392

Your references show protection from direct lightning strikes, not
ground current. I agree that your scenarios protect someone from direct
lightning strikes. But I think you're missing part of the picture: the
ground current.

--
Dave
dvt at psu dot edu

Everyone confesses that exertion which brings out all the powers of body
and mind is the best thing for us; but most people do all they can to
get rid of it, and as a general rule nobody does much more than
circumstances drive them to do. -Harriet Beecher Stowe, abolitionist and
novelist (1811-1896)

email hidden said:

but lightning rods are designed to protect structures
(and people within the structures), not people standing
outside in an electrical storm.

What exactly are you saying here? That we actually have to take
responsibility and deal with the environment? That we can't control
it?

Egads, next thing you know you'll be suggesting that we have to take
responsibility for what we do to the enivronment!

dvt said:

Dorfus Dippintush said:

dvt said:

Dorfus Dippintush wrote:

Quoted message said:

Quoted message said:

> A switchyard has earthing conductors that run underground that
> reduce such effects. That's why it's the safest place to be.

I can believe that a switchyard has a good grounding system. I don't
have first-hand experience, but it seems plausible.

I should add that I don't know if the grounding system is sufficient to
keep potential differences low within the switchyard. And since a
switchyard is prime territory for lightning strikes and concomitant
mechanical damage, I don't know if a switchyard is a safe place during a
lightning storm.

Quoted message said:

Quoted message said:

But that doesn't fix your first sentence: "The safest place is under
large power lines." I think that's bad advice.

Quoted message said:

Above large power lines you have one or two large conductors, they are
there especially to to take lighting strikes. They protect the current
carrying conductors below from lightning.

And where do those large conductors lead? To an earth point somewhere
near the poles. And where are you standing in the case you propose?
Somewhere near the poles. Sounds like a bad idea to me.

Quoted message said:

Do some research. Talk to someone that knows transmission lines.

Am I having a conversation with "someone that knows transmission lines"
in this exchange?

Quoted message said:

http://richoq.home.mindspring.com/transmission.htm

http://concise.britannica.com/ebc/art-19392

Your references show protection from direct lightning strikes, not
ground current. I agree that your scenarios protect someone from direct
lightning strikes. But I think you're missing part of the picture: the
ground current.

Well if you don't like it then go and stand in the open. Problem solved.

Dorfus

Quoted message said:

Dorfus Dippintush said:

dvt said:

I can believe that a switchyard has a good grounding system. I don't
have first-hand experience, but it seems plausible. But that doesn't fix
your first sentence: "The safest place is under large power lines." I
think that's bad advice.

Above large power lines you have one or two large conductors, they are
there especially to to take lighting strikes. They protect the current
carrying conductors below from lightning. Do some research. Talk to
someone that knows transmission lines.

http://richoq.home.mindspring.com/transmission.htm

http://concise.britannica.com/ebc/art-19392

Dorfus

Lightning is unpredictable. If lightning strikes a
tower above you, the shortest path to ground will be
through the grounding strap of the tower. But that
doesn't guarantee that some portion of the electric
current will not also take the path through you.

In the little picture about lightning rods posted earlier,
the cone of protection is shown with a little cartoon
house inside it. Not a little cartoon person standing
next to the tower base. It is, of course, a cartoon,
but lightning rods are designed to protect structures
(and people within the structures), not people standing
outside in an electrical storm.

Ben

It's not a cartoon it's a diagram.

If you don't like it then go and stand in the open.

Dorfus