Re: Am I courting disaster?

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

Original poster: Bert Hickman <bert.hickman-at-aquila-dot-net> 

Hi Adam,

There are two main types of modern lightning arresters (or arrestors - I've 
seen both spellings) in current use. The older style uses a spark gaps in 
series with silicon carbide MOV elements. The spark gaps were necessary to 
prevent excessive AC current from constantly flowing through the leaky MOV 
element. Newer arresters (>1970) use low leakage MOV elements made from 
zinc oxide disks - this style does not require the use of spark gaps.

I have some pictures of a "visible" 9 kV distribution class arrestor with a 
clear Pyrex housing on my site. The spark gaps and silicon carbide MOV 
elements are easily visible within:
http://205.243.100.155/photos/Arrestor1.jpg
http://205.243.100.155/photos/Arrestorgaps.jpg
http://205.243.100.155/photos/ArrestorMOV.jpg

BTW, some interesting information on arrestor history, theory, construction 
can be seen in these PDF's from Ohio Brass:
http://www.hubbellpowersystems-dot-com/powertest/literature_library/pdfs4lib/OB/EU1044-H.pdf
http://www.hubbellpowersystems-dot-com/powertest/literature_library/pdfs4lib/OB/EU1377-H.pdf

Best regards,

-- Bert --
-- 
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We specialize in UNIQUE items! Coins shrunk by Ultrastrong Fields,
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Tesla list wrote:

>Original poster: Yurtle Turtle <yurtle_t-at-yahoo-dot-com>
>Yes, this is for HV side protection. If placed on the
>LV side, it would hardly protect the pig.
>This one conducts at 18 kV and is for a 14.4 kV 25 kVA
>pig. The photo doesn't do it justice, as it's probably
>around 30" long and 3" to 4" in diameter.
>As to whether it's a MOV, I've always assumed it was
>simply a spark gap, since it's called an "18 kV gap":
>http://www.hot-streamer-dot-com/adam/garage/gap_18kV_2.jpg
>though it may be more than a simple spark gap. Someone
>on the list disected one once, though I forget what he
>found.
>Adam
>--- Tesla list <tesla-at-pupman-dot-com> wrote:
>  > Original poster: Thomas <tom-at-pwrcom-dot-com.au>
>  >
>  > Yikes! I take it that is meant to protect
>  > thetransformer from the HV side?
>  >
>  > What is it- a MOV?
>  >
>  > I was thinking more along the lines of protecting
>  > other devics connected to
>  > the same LV (120/240V) circuit as the pig.
>  >
>  > Tom.
>  >
>  > Original poster: Yurtle Turtle <yurtle_t-at-yahoo-dot-com>
>  >
>  > I think he was referring to a pig lightning
>  > arrestor,
>  > like one of these:
>  >
>  >
>http://www.hot-streamer-dot-com/adam/garage/gap_18kV_1.jpg
>  >
>  > Quite huge and heavy.
>  >
>  > Adam
>  >
>  > --- Tesla list <tesla-at-pupman-dot-com> wrote:
>  >   > Original poster: Thomas <tom-at-pwrcom-dot-com.au>
>  >   >
>  >   > Original poster: "Crow Leader"
>  >   > <tesla-at-lists.symmetric-dot-net>
>  >   >
>  >   > -snip-
>  >   >    How about just a spark gap? Lightning
>  > arrestors
>  >   > are large and heavy,
>  >   > even
>  >   >    polymer ones. This sort of defeats the entire
>  >   > goal you were shooting
>  >   > for.
>  >   > -----------------------------------
>  >   >
>  >   > Where'd you get that idea? One of these on each
>  > 120V
>  >   > line to earth would do
>  >   > the trick quite nicely:
>  >   >
>  >
>http://www.novaris-dot-com.au/products/earthing/specs/ec20.html
>  >   >
>  >   >
>  >
>.