[Trade Journal]
Publication: Electrical Review and Western Electrician
Chicago, IL, United States
vol. 60, no. 12, p. 581, col. 1
An Improved Giant Strain Insulator.
The giant strain insulator shown in the accompanying illustration has been designed with a view to maintaining permanently its high insulation resistance and exceptional mechanical strength.
The two metal parts are insulated from one another by layers of sheet mica, each sheet having sufficient dielectric strength to withstand the potential for which the insulator is designed. The malleable-iron cup casting is crimped over the stud casting by a pressure of 40 tons, thus making an absolutely rigid insulated joint. Any movement of the parts is thus prevented when the insulator is subjected to tension or temperature changes and the mechanical strength of the insulator is limited only by the strength of the malleable-iron eyes or devises, which are designed liberally so as to withstand the severest service conditions.
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| Giant Strain Insulator. |
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| Section Through Insulator Showing Sheet Mica. |
A non-absorbent insulating compound is molded over the entire insulated joint, making it waterproof. Owing to the rigid joint this molded insulation is subjected to no mechanical strains. Its exterior surface is so formed that it provides ample creepage surface and effectually prevents a continuous film of moisture from forming between the metal parts. The latter are sherardized which effectually prevents corrosion.
Every insulator is tested mechanically at one-half its ultimate strength, the two-inch size at a tension of 2,500 pounds and the 2-inch size at a tension of 4,000 pounds. Both sizes are subjected to an alternating-current potential test of 5,000 volts for five seconds. This insulator is manufactured by the General Electric Company, Schenectady, N.Y.
