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  #11  
Old 03-18-2003
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Something that looks like a fuse

Gord,
Dissipation is an important function of land based LP systems. As a captive observer on the top of +800 structures at power plants I can report dissipation does occur (4-6" blue arcs at the tips of lightning points). Obviously, discharging a total strike energy does not occur as strikes do happen to these structures (and, yes, lightning does strike twice, three, four....). The LP systems have specific guidelines (for instance, no downcomer change in direction greater than 45 degrees) which are intended to direct the strike away from electrical conductors, motors etc and with eventual dissipation into the ground.

As the system Werner describes contains abrupt changes in direction and termimates at a dubious ground plate, I would be more concerned with blowing a hole in the boat at a most susceptible location!! Think I would dangle a chain around a shroud when things start crackling.

The land systems we install are UL certified and designed in accordance with National Fire Protection Assoc guidelines. But the science behind it is mostly empirical!! The marine designs are probably even more reliant upon witchcraft!!





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Old 03-18-2003
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Something that looks like a fuse

SOLVED....

I received from a colleague owner of a Dufour a part of the manual identifying the part…

“The entire rigging is grounded by a metal strap connecting the forestay chain plate to the keel. Under normal conditions this circuit is cut by a lightning conductor fixed on the strap situated on the hull behind the main bulkhead. … … The circuit is only re-established if there is an electric discharge of high intensity. This allows use of the rigging as antenna.”

OK… at least Dufour tried to do something about lightning discharge. As some of you already stated it is very doubtful that this might work, but it has been identified.

No… I did not contact Dufour about this. The main reason is that the currect Dufour company only bought the name Dufour. It’s not the same company, hence my doubt that they would know.

Next weekend I''ll make a picture of the "lightning conductor" as it has been identified by now. I only don''t know how to post it on this forum...

thanks guys for the feedback
Werner
Antwerp - Belgium

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Old 03-19-2003
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Something that looks like a fuse

Werner:
I''m still confused as to this device''s function.
Is it something like a Metal Oxide Varister (MOV) that only conducts at high voltages; thereby establishing a path to ground for (above threshold) lightning energy?

John Parker:
I knew I should stay "out" of this one - too complex to cover properly - BUT ...
The research (I''ve seen) FAILS to indicate that "Early Streamer (Ion) Dissipators" reduce the incidence of lightning strikes on land-based tall structures. The ground path DOES mitigate the dammage caused by lightning strikes.
For 2 good articles see:
IEEE Transactions on Power Delivery, Vol. 13, No 4, October 1998 (Abdul M. Mousa)
and
IEEE Transactions on Electromagnetic Compatibility, Vol. 33, No. 2, May 1991 (Ewan M. Thomson)
It would take thousands of words to describe the actual installation; but (in reply to yours):
45 degree change in direction: Straight conductors (to ground) are preferred; but a 90 deg. bend with a minimum radius of 8" can be accommodated.
Chain around a shroud: The (minimum #6 AWG copper)ground connection to (salt) water should present a minimum of 1 square foot of surface to the water - more is preferable, especially in fresh water. Would, rather suggest connecting a #6 AWG cable to a (min.) 1 square foot x 1/4" ground plate. This could be clamped to the bow chain plate (further from occupants),
Your concerns ("blowing a hole in boat) are well founded, and not simply addressed.
NFPA guidlines are under current review, and mostly address methodes of dammage mitigation, not prevention (which I, and others, believe to be impossible).
Witchcraft? You bet!
Thanks for all the good information & opinion from all.
Respectfully,
Gord

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Old 03-19-2003
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Something that looks like a fuse

Gord,

When looking through the glass tube at the inside of the "lightning conductor" I recognize 2 electrodes, about 3mm apart. I gues that they work as a kind of arc-lamp. When voltages rise above threshold a spark will jump from one electrode to the other, herby making a ‘plasma’ connection where current can flow through. Again as mentioned before it’s doubtful that it would work for real lighning...

The exterior of the device looks like a very thick fuse with terminal-leads.
It’s about 7.5cm(3”) long and 2cm(.8”) thick.

Best regards
Werner
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