wrote in message
...
On Oct 15, 10:54 am, Ian Jackson
wrote:


One reason for lightning conductors (and for grounding elevated
conductors, like radio antennas) is that it helps to stop a high
electrostatic charge from accumulating in the air immediately above
them. The intention is to PREVENT a direct lightning strike, rather than
conduct a strike to ground. Of course, if a direct strike DOES occur, an
antenna (and even a stout lightning conductor) may be seriously damaged.
--
Ian

"The only problem with that is that the charge is so quickly
replenished
that I think trying to bleed off the charge is a waste of time."

The turn of the century genius, Testla, patented some lighting protection
devices based on having an insulated "cap" at the highest object on the
protected property. The "cap" would rise thousands of volts above the
protected structure and this would reduce the tendency of lightning to
strike.

Seems to me that the federal government has lots and lots of buildings and
would relatively inexpensively conduct definitive experiments to see what
works and what doesn't in the area of lightning protection.

So far as I know, the feds have done no such thing.

On Oct 16, 8:55*pm, "John Gilmer" wrote:
wrote in message

...
On Oct 15, 10:54 am, Ian Jackson

wrote:

One reason for lightning conductors (and for grounding elevated
conductors, like radio antennas) is that it helps to stop a high
electrostatic charge from accumulating in the air immediately above
them. The intention is to PREVENT a direct lightning strike, rather than
conduct a strike to ground. Of course, if a direct strike DOES occur, an
antenna (and even a stout lightning conductor) may be seriously damaged..
--
Ian

"The only problem with that is that the charge is so quickly
replenished
that I think trying to bleed off the charge is a waste of time."

The turn of the century genius, Testla, patented some lighting protection
devices based on having an insulated "cap" at the highest object on the
protected property. * The "cap" would rise thousands of volts above the
protected structure and this would reduce the tendency of lightning to
strike.

Seems to me that the federal government has lots and lots of buildings and
would relatively inexpensively conduct definitive experiments to see what
works and what doesn't in the area of lightning protection.

So far as I know, the feds have done no such thing.

yes, they have, not that i believe everything the government has said,
but this stuff i do.

this presentation lists several reports by the navy and faa among
other agencies: http://www.docstoc.com/docs/4177489/...-Abdul-M-Mousa

the nfpa and others are quoted here, even though the author is
skeptical: http://www.straightdope.com/columns/...-strikes-again

this one again quotes the onr, nasa, and air force studies as well as
others. http://lightning-protection-institut...ct-fallacy.htm

as far as tesla's stuff, i file it with most of the other experiments
with lightning protection and prevention, if it really worked it would
be used all over the place. the only system that has stood the test
of time is the old franklin rod system, it doesn't prevent strikes,
but it does try to provide a safe route to ground besides through the
protected structure. much of the success of it depends on the quality
of the installer, mostly how well they bond the various wires and how
well they take it to ground.

John Gilmer wrote:
wrote in message
...
On Oct 15, 10:54 am, Ian Jackson
wrote:

One reason for lightning conductors (and for grounding elevated
conductors, like radio antennas) is that it helps to stop a high
electrostatic charge from accumulating in the air immediately above
them. The intention is to PREVENT a direct lightning strike, rather than
conduct a strike to ground. Of course, if a direct strike DOES occur, an
antenna (and even a stout lightning conductor) may be seriously damaged.
--
Ian

"The only problem with that is that the charge is so quickly
replenished
that I think trying to bleed off the charge is a waste of time."

The turn of the century genius, Testla, patented some lighting protection
devices based on having an insulated "cap" at the highest object on the
protected property. The "cap" would rise thousands of volts above the
protected structure and this would reduce the tendency of lightning to
strike.


This is done in some HV test laboratories to avoid flashover to the
ceiling and to make the field more representative of "outdoors".. they
hang a semiconductive curtain in a horizontal plane above the apparatus
which charges up and makes what's above look less like "ground"


There's also the whole thing of surrounding a valuable structure (e.g.
ammunition storage bunker, rocket launch pad) with an array of high
towers with grounded wires from the tops of the towers. While no
guarantee that lightning won't strike elsewhere, it definitely ups the
odds of the protective structure taking the hit.

here's a pictu
http://commons.wikimedia.org/wiki/Fi...launch_pad.jpg

On Oct 16, 10:43*pm, Jim Lux wrote:
John Gilmer wrote:
wrote in message
...
On Oct 15, 10:54 am, Ian Jackson
wrote:

One reason for lightning conductors (and for grounding elevated
conductors, like radio antennas) is that it helps to stop a high
electrostatic charge from accumulating in the air immediately above
them. The intention is to PREVENT a direct lightning strike, rather than
conduct a strike to ground. Of course, if a direct strike DOES occur, an
antenna (and even a stout lightning conductor) may be seriously damaged.
--
Ian

"The only problem with that is that the charge is so quickly
replenished
that I think trying to bleed off the charge is a waste of time."

The turn of the century genius, Testla, patented some lighting protection
devices based on having an insulated "cap" at the highest object on the
protected property. * The "cap" would rise thousands of volts above the
protected structure and this would reduce the tendency of lightning to
strike.

This is done in some HV test laboratories to avoid flashover to the
ceiling and to make the field more representative of "outdoors".. they
hang a semiconductive curtain in a horizontal plane above the apparatus
which charges up and makes what's above look less like "ground"

There's also the whole thing of surrounding a valuable structure (e.g.
ammunition storage bunker, rocket launch pad) with an array of high
towers with grounded wires from the tops of the towers. *While no
guarantee that lightning won't strike elsewhere, it definitely ups the
odds of the protective structure taking the hit.

here's a pictuhttp://commons.wikimedia.org/wiki/Fi...aunch_pad.jpg- Hide quoted text -

- Show quoted text -

yeah, the nasa pads have towers and long sloped wires to try to catch
lightning also.

for hv work we mostly do it outside or in a very tall building (the
octagonal one just left of center in the top picture is open inside
and about 80' tall.
http://www.ewh.ieee.org/r1/schenecta...2007_lenox.pdf