Re: Saltwater Caps

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


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, April 02, 2001 8:34 PM
Subject: Re: Saltwater Caps


> Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz
<twftesla-at-uswest-dot-net>"
> I don't know enough about glasses to translate the old recipes to
> modern glasses, but I imagine that too "alcaline" glasses
> are bad, because they attract water. Borosilicate glass, as "Pyrex",
> is better (I have made some good Leyden jars with Pyrex glass, waxed).
> What kind of glass is used in those big insulators seen in high-
> voltage power transmission lines?

Judging from the distinctly greenish color, I'd say it has a lot of iron in
it.  For HV string insulators, the breakdown strength of the material isn't
as important as the mechanical strength. You can always string more segments
to raise the breakdown voltage.  Also, the creepage breakdown on the surface
is a bigger problem (salt, dust, bird feces, etc.) than the breakdown
through the material.  High iron glass is stronger - check out the color of
a glass table top, "bulletproof" glass, etc. (BTW, high iron glass is
terrible for solar collectors and optical components because it is IR
absorbing...)