Re: Lightning Arrestors (was Geek Pig)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>

Almost certainly they are a stack  and zinc oxide (or some proprietary
blend of zinc, bismuth, and cobalt compounds) disks.  Essentially a stack
of MOVs.  The idea is to conduct the lightning to ground, without allowing
a follow on arc from the power line, and without dissipating too much power.

The MOVs are not infinite life.  Each time they take a hit, they die a
little.  The breakdown voltage decreases a bit, and the leakage current
increases.  Typical leakage currents are cited as 0.5 to 1 mA.

Even in California, powerline components are tough (our problems are
financial.. it's a shortage of money, not kWh)

The metal oxide arresters replace the old magnetically blown arc arresters,
which formed an arc, and then used the arc current to create a magnetic
field that blew out the arc.  


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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