Publication: Electrical Review
New York, NY, United States
High-Tension Strain Insulators.
The accompanying illustrations show two forms of high-tension strain insulator placed on the market by the Locke Insulator Manufacturing Company, of Victor, N. Y. The increase in the use of high-tension electric railroads will call for insulators capable of withstanding high mechanical and electric strains. The insulator shown is designed as the Victor No. 601 strain insulator, six inches high and five and three-quarters inhces in diameter, and has been designed for voltages as high as 8,000. The company has also developed a smaller strain insulator of the same general design for voltages of 5,000 and under. This design is very useful in the construction of spans for trolley suspension. The company is manufactuing a complete line of strain insulators for voltages up to 35,000, and is developing a new design which it will be able to manufacture for voltages of 60,000 or more.
As an indication of the mechanical strength of these insulators, the company reports that it has experimented with these designs considerably, and finds that its larger designs may be relied upon to stand a breakdown test of approximately 12,000 pounds, with the insulator supported by a pin passing through the middle, and the strain applied around the middle wire groove. In connection with these insulators the company has developed a method of using them, whereby almost any strain up to several tons may be applied with entire safety.
These insulators are used for deadending, curves or similar use in holding live wires of high voltage under excessive tension, the ordinary pin being too weak. The mechanical efficiency of the construction is apparent. The maximum strength of the pin is obtained. The pin is supported top and bottom, and the pull is transferred directly to the pole. The pin holes are all of largest diameter at top and bottom, having the smallest diameter directly opposite the wire groove, so that the porcelain is always under direct compression only, though the pin flex somewhat under varying loads.
A large line of insulators for all classes of service is described in "The Insulator Book," No. 8, recently issued by the Locke Insulator Manufacturing Company.