RU2272346C1 - Spiral dead-end clamp - Google Patents

Abstract

FIELD: power engineering; attachment of bare conductors to supporting structures of overhead power transmission lines.

SUBSTANCE: proposed clamp is, essentially, spiral stranded conductor made of steel or aluminum wires stuck together. Inner surface of stranded conductor is covered with abrasive material to enhance conductor-to-clamp friction coefficient. Stranded conductor is looped in its middle part. This loop is fitted onto thimble and the latter is attached to supporting structure of overhead power transmission line. Density of abrasive coating applied to stranded conductor is such that variable friction coefficient is ensured throughout entire length of clamp relative to wire ranging between 0.1 and 0.8; coiling angle of spiral wires of strand 1 on conductor 4 throughout clamp length is also variable. As an alternative, abrasive is not applied on inner surface of clamp strand within section of definite length (up to five coiling pitches);coefficient of spiral wire compression relative to conductor 4 also varies in the course of manufacture within the range of 0.8 to ≥1. This clamp ensures design strength of conductor termination without impairing integrity of conductor, its contacting surface does not cause damage to external wires of stranded conductor.

EFFECT: enhanced reliability of securing bare conductors on line supporting structures.

2 cl, 3 dwg

Description

The invention relates to the field of electric power and, in particular, to spiral-type fittings (spiral tension clamps) for hanging bare wires of overhead power lines.

Known, for example, referring to the type of widely used standard linear reinforcement, a compressible clamp for multi-wire wires of overhead power lines, made in the form of a metal body with an eye, enveloping the body with a flexible wire element with fluffy ends and a compression sleeve, mounted on a flexible element [1] .

Of the significant drawbacks of this clamp, it is first necessary to note the complexity, multi-element design of the clamp and, as a result of this, possible installation difficulties associated with the need to use press equipment in the field (special hand presses).

Currently, traditional linear fittings are often replaced by spiral-type fittings, which has significant advantages over clamps of traditional designs. Such reinforcement, providing reliable fastening of the wire, protects it from excesses, abrasions, and other mechanical damage; while there is a more uniform distribution of compressive forces along the length of the wire, the exclusion of their local concentrations; installation of spiral fittings is simple and does not require the use of special tools or devices.

The closest technical solution to the proposed one is a spiral tension clamp for hanging bare wires of overhead power lines, containing a U-shaped strand of spiral wires wound on a wire with a thimble embedded in its loop, while a layer of adhesive compound with an abrasive is applied to the inner surface of the strand [ 2].

However, this spiral tension clamp also has a significant drawback. Under the action of large tensile loads approaching the wire, approaching the breaking strength of the wire, deformation (tension) of the spirals forming the clamp occurs, especially intense in the area close to the clamp loop (the first 2 ÷ 3 turns of the spiral, counting from the loop). Due to the abrasive on the inner surface of the strand, the friction forces between the clamp strand and the wires of the outer coil are much more friction between the strands of the wire itself, as a result of which the wires of the outer coil are slipped along the wires of the inner coil and are deformed according to the movements of the clamp strands. Since the wires of the wire during installation are laid in a much more gentle spiral than the spiral wires that form the strands of the clamp, their longitudinal deformation may be more than the maximum permissible limit and the upper twisting of the wire may be destroyed.

The applicant, ZAO ESPP, and the authors set themselves the task of developing a new spiral tension clamp free from the disadvantages of known clamps of a similar purpose, in particular, characterized by high reliability during long-term operation in any conditions and ensuring the operational reliability of the line wire. This positive technical result is achieved due to the combination of essential design features set forth in the claims, namely: a spiral tension clamp for hanging uninsulated wires of overhead power lines, containing a U-shaped strand of wire spirals wound on the wire with a thimble embedded in its loop, while a layer of adhesive compound with an abrasive is applied to the inner surface of the strand; the abrasive is applied to the inner surface of the strand in such a way that the value of the friction coefficient of the strand relative to the wire is a variable that varies between 0.1 ÷ 0.8, at the loop of the strand the friction coefficient is minimum and maximum at the end of the clamp, the angle of winding of the spiral wires relative to the horizontal axis wires are varied along the length of the clamp and determined within 15 ° ÷ 40 °, while the value of the angle of winding of the spiral wires at the loop of the strand is minimal and maximum at the end of the clamp, and the compression ratio of the strands relative to the wire and changing selected in the range of 0.8 to ≥ 1, wherein the maximum value corresponds to the strand at the nip site loops and the minimum value is realized at the ends of the strand clamp; up to 5 steps of winding spiral wires onto the inner surface of the strand, starting from the loop, no abrasive is applied.

The invention is illustrated by drawings, where figure 1 shows a view of a clamp made according to the present invention, with a thimble embedded in its loop; figure 2 - strand of the clamp shown in figure 1, with a variable angle of winding spirals; figure 3 is a General view of the declared spiral tension clamp mounted on a wire line.

The inventive spiral tension clamp consists of a U-shaped strand 1, the length (800 ÷ 2000 mm) of which is selected based on the condition of the required sealing strength, and thimble 2, inserted into the loop 3 of the strand 1. The strand is formed of spiral wires; the inner surface of the strand 1 is glued with a compound and an abrasive is applied to it. During installation, a strand of 1 clamp is wound onto a wire of 4 lines. The abrasive provides the grip of the clamp with the wire 4 lines. As a material for spiral wires of strand 1, we take steel galvanized wire according to GOST 9850-72 or steel high-strength wire with extruded aluminum coating, which has recently been put into operation.

The abrasive is applied over the entire length of the clamp along the inner surface of the strand 1, but with a different density in different sections of the length of the strand 1; in the area near the loop 3 of the strand 1, the density of the layer of applied abrasive is minimal up to zero, and then towards the end of the length of the clamp, the density of the layer of applied abrasive increases. The density of the applied abrasive is adjusted by fixing the value of the coefficient of friction of the spiral wires of the strand 1 relative to the surface of the wire 4. The values of the coefficient of friction vary within the limits equal to (0.1 ÷ 0.8). The abrasive is applied to the inner surface of the strand 1 so as to ensure the minimum value of the coefficient of friction near the loop 3 of the strand, and the maximum value at the end of the clamp. As an option, for a length of up to 5 steps of winding the strand 1, starting from its loop 3, the abrasive is not applied at all to the inner surface of the strand 1. The angle of winding 7 of the spiral wires of the strand 1 relative to the longitudinal axis 5 of the wire 4 varies along the clamp length ranging from 15 ° to 40 ° so that the minimum value (15 °) of the angle γ is in the area of loop 3 of strand 1, and the maximum (40 °) in the final section of the clamp length. In the manufacture of the clamp, the strand 1 is made so that the compression ratio of the wires of the strand 1 relative to the wire 4 varies along the length of the clamp from the maximum value (≥1) at loop 3 to the minimum value (0.8) at the end of the clamp. Under the compression ratio refers to the ratio of the inner diameter of the strand 1 of the clamp to the outer diameter of the wire 4, for installation on which the clamp is intended.

The clamp is mounted on the line wire as follows:

wire 4 is cleaned of dirt (dust) at the installation site of the clamp; then a loop 3 is put on with strands 1 of the clamp on the eyelet 2, wire 4 is inserted into one half of strand 1 at the place indicated by the color mark, and strand 1 is wound on wire 4 two turns; then in the same way the second half of strand 1 is wound on the wire for two turns; then the strand 1 is wound alternately by both halves until the clamp is completely wound on the wire 4, while making sure that the strand 1 lies on the wire 4 evenly without overlaps; the ends of the strand 1 of the clamp are adjusted using a mounting tool (screwdriver).

Spiral tension clamps of the proposed design will be widely used as anchor fastening of AC wires (GOST 839-80) with a cross section of up to 400 mm ² to the supports of overhead power lines during construction, reconstruction and repair due to their high operational reliability. The calculated and experimental tests confirmed the validity of designing clamps of this type with a variable coefficient of friction of the inner surface of the clamp strand along the wire, a variable value of the angle of winding of the spiral wires relative to the longitudinal axis of the wire over the entire length of the clamp, and a varying compression ratio of the clamp strand relative to the wire.

The experiments showed that the use of spiral tension clamps of the proposed design does not damage the outer wires of the wires while ensuring the specified clamping strength of the wire in the clamp, which is at least 90% of the breaking strength of the wire. ESPP CJSC carries out serial production of the declared spiral tension clamps.

Information sources

[1] Copyright certificate of the USSR No. 1014083, class H 02 G 7/02, dated 11.08.81

[2] Monthly production and technical journal "Electric Stations" No. 1, 1998, pp.3-5, Fig.2.

Claims (2)

1. A spiral tension clamp for hanging uninsulated wires of overhead power lines, containing a U-shaped strand of spiral wires wound on a wire with a thimble embedded in its loop, while a layer of adhesive compound with an abrasive is applied to the inner surface of the strand, characterized in that the abrasive is applied to the inner surface of the strand so that the value of the coefficient of friction of the strand relative to the wire is a variable that varies within 0.1 ÷ 0.8, at the loop of the strand the friction coefficient is minimal and max alen at the end of the clamp, the angle of winding of the spiral wires relative to the horizontal axis of the wire is varied along the length of the clamp and is determined within 15 ° ÷ 40 °, while the angle of winding of spiral wires at the loop of the strand is minimal and maximum at the end of the clamp, and the compression ratio of the strands relative to the wire is selected varying from 0.8 to ≥ 1, and the maximum value corresponds to the section of the strand at the clamp loop, and the minimum value is realized at the end of the clamp. 2. The clamp according to claim 1, characterized in that for a length of up to 5 steps of winding spiral wires onto the inner surface of the strand, starting from the loop, no abrasive is applied.

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