The Provo Type High Potential Insulator
by Elton and Lynda Gish
Reprinted from "INSULATORS - Crown Jewels of the Wire", May 1972, page 5
The Hemingray Glass Company of Covington, Ky., is placing on the market the
"Provo" type insulator for high potential work. This is the insulator
which has given such excellent results on the 40,000 volt line of the Telluride
Power Transmission Company in Utah. The insulator was perfected nearly a year
and a half ago, and is the outcome of several years of experiment with existing
types and many new forms. It is only now that a description appears in print, as
it has been the desire of the makers to fully establish its worth. It is all
glass, which is the cheapest insulating material, and is boldly claimed to be
the only one that is absolutely reliable when exposed to the weather and the
action of high potential currents.
It is 5-3/4 inches high and 7 inches in diameter and has five petticoats. Two of
these petticoats are near the line wire and serve to break the continuity of the
exposed surface between the wire and the pin or the cross arm, which tends to
prevent jumping of the current between these points. Another advantage of these
petticoats near the line wire is that they protect surfaces of small area and
high resistance, which check surface leakage at its source. It is noticed in
actual practice that these surfaces remain free from moisture and snow. The
other petticoats on the bottom extend the surface distance from the line wire to
the pin to 16 inches. Teats along the bottom of the outer petticoat aid in
shedding water.
The line is tied around the insulator in the topmost groove, which holds it well
above the cross arm. This method of tying has been adopted, as it is considered
the best for use in a country where the strain on an insulator may be either up
or down or sidewise.
The thickness of glass is well proportioned and the insulator is extra strong in
resisting mechanical breakage or electrical punctures. Tests have been made
between the points for the wire and the pin with voltages as high as 125,000
without puncturing the material. The thread is of standard size and 2-1/2 inches
long. The strain of the wire comes squarely on the pin. The glass is almost
colorless and the insulator is not conspicuous on a pole line. The name of
Hemingray is a sufficient guarantee for good work in the glass insulator line.
They have increased facilities for manufacturing this insulator and are prepared
to fill orders on short notice.
Taken from:
The Electrical Engineer
December 29, 1898
Elton and Lynda Gish
614 Dallas Street
Port Neches, Tex. 77651
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