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Re: Lightning Arrestors (was Geek Pig)



Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-uswest-dot-net>" <bert.hickman-at-aquila-dot-net>

Chris,

Turns out they ARE a bit more complicated than that - remember that
arrestors are designed to provide a safe path to ground for HV
transients, but should open back up once the surge has gone. They must
be able to rapidly recover and hold off normal line voltage. Ideally,
they should pull little or no current at normal line voltage. 

To meet these requirements, most arresters are actually a combination of
spark gaps and MOV's, with the MOV element actually made of silicon
carbide. I happen to have a clear glass 9 kV (Pyrex) arrestor that I use
for demos - it has a MOV that's about  9" long by 3" in diameter, in
series with eight spark gaps (each about 1/16"). Will be interesting to
see what you find inside yours... :^)

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "Christopher Boden by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <chrisboden-at-hotmail-dot-com>
> 
> >Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> ><Tesla729-at-cs-dot-com>
> >
> >In a message dated 1/22/01 10:54:39 AM Pacific Standard Time,
> >tesla-at-pupman-dot-com writes:
> >
> 
> ><< Does anyone know the internal construction of the arrestors? >>
> >
> >It's my understanding that they are basically an appropriate number
> >of  HV (1800 volt?) MOVs in series. I know from experience that they
> >don't burn out once they are called on to shunt an overvoltage peak.
> >Once the voltage returns to normal operational levels, they are as good
> >as new.
> >
> >David Rieben
> >
> 
> Terry would be in a better position to answer this, but I'm willing to bet
> they're nowhere near that complicated. Consumers Power (and the NPG as a
> whole) subscribes to the Brute-Force system. This is why things (unless you
> live in CA) are so well overengineered. These are designed to be put into
> service in terrible conditions (we have -20 to 120 temps on a regular basis)
> and last for decades. These arrestors are from '75 to '83 as was ALL the
> gear we got. Aside from surface rust, a little fading, and some new friends
> (of the Arachnoid variety) they are all in mint condition. I think they are
> nothing more than a well sealed, insulated, spark gap, that's all. and I'm
> going to open one of each to make sure.  I'll post an autopsy of each on the
> website. I may try (as a scientific experiment, of course) discharging
> Groucho (Marx bank) and Thumper (50kJ cap array) though it, just to see what
> happens. But I don't think we can crank Thumper up to 12kV....hmmmmmmmm.
> 
> >
> >
> 
> Christopher "B A N G....it WORKED!" Boden Geek#1
> President / C.E.O. / Alpha Geek
> The Geek Group
> www.thegeekgroup-dot-org
> Because the Geek shall inherit the Earth!
> 
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