Publication: Electrical Age
New York, NY, United States
Insulator Clamps for Transmission Lines
INSULATOR clamps manufactured by the Clark Electric & Manufacturing Company, of New York, for use on overhead transmission lines, are shown in the annexed illustrations. They were designed to replace the weak tie wire and to make a mechanical connection between conductor and insulator, distributing the strain over as much insulator area as possible and allowing the conductor play through the insulator to prevent the hinging action resulting from sway.
The interlocking clamp is used with a special insulator. The latter is constructed with an undercut recess on each side of the groove in the center of the insulator top, so that when the clamp is in position it is interlocked under the projecting portion in such a manner that the wire cannot be removed or the clamp separated from the insulator without unlocking the clamp.
The construction is such that the end strain on the clamp is distributed so that excessive pressure can at no time be concentrated on a small area of porcelain, and at the same time sufficient clearance is allowed so that the cable and clamp together may move freely when the cable or conductor is in place in the insulator, avoiding the hinge action which takes place when the wire is rigidly held in the insulator. This clamp is made in sizes ranging from No. 2 bare to 500.000 circular mils weatherproof.
The standard insulator clamp is designed for use with standard insulators. The two clamps are tightened firmly to the conductor on each side of the insulator by means of a bolt and a nut. The projecting lips engaging the groove of the insulator transfer the end strain to the porcelain in an effective manner. The loops surrounding the neck of the insulator hold the clamps firmly in position and prevent the conductor from being lifted from the groove.
The company also manufacture a copper splicing sleeve, illustrated herewith. These sleeves are made of pure seamless copper tubes, oval in shape, slightly spread at each end, and in sizes to fit any conductor used. The splice is made by running the ends of the conductor into the oval tube and then simply twisting front both ends.
Each sleeve is annealed by a process which secures a hard exterior wall with a soft interior, so that in twisting up the sleeve the hard exterior surface causes the sleeve to tighten over the wires and to partially embed them in the interior of the sleeve, which is considerably softer than the hard-drawn wires, thus giving a much greater area of contact between the wires and sleeves. The joint, moreover, it is claimed, permanently retains its conductivity, as the wires are pressed into the sleeve in such a manner as to prevent oxidation or deterioration in any form after the splice is made up.
Owing to the special process of annealing employed, it is claimed, the difficulty heretofore experienced by the sleeves splitting in making up the splices is overcome, and at the same time there is a satisfactory margin of safety over the tensile strength of the conductor. Special tools are furnished for twisting up these sleeves.