US3914532A

US3914532A - Sector cable

Info

Publication number: US3914532A
Application number: US460126A
Authority: US
Inventors: John J Dyba; Carl F Ackerman
Original assignee: Anaconda Co
Current assignee: Ericsson Inc
Priority date: 1974-04-11
Filing date: 1974-04-11
Publication date: 1975-10-21
Anticipated expiration: 1992-10-21

Abstract

A sector cable comprising a plurality of wedge-shaped, segments, composed of a plurality of compacted and twisted wire strands, arranged with side walls abutting and with the point of each wedge directed toward, but spaced from, the central axis of the cable, at least alternate segments covered on the exterior with an insulation covering comprising at least two layers of an extensible, flexible, and dense, uncreped paper, the insulated and uninsulated segments being so spaced in relation to each other that the side wall of any uninsulated segment does not abut the side wall of any other uninsulated segment.

Description

[ Oct. 21, 1975 I SECTOR CABLE [75] Inventors: John J. Dyba, New York, N.Y.; Carl F. Ackerman, New Hope, Pa.

[73] Assignee: The Anaconda Company, New

York, NY.

22 Filed: Apr.1l, 1974 21 Appl. No.: 460,126-

[52] U.S. Cl 174/119 R; 174/110 P; 174/114 S FOREIGN PATENTS OR APPLICATIONS Netherlands 174/114 S Primary ExaminerE. A. Goldberg Attorney, Agent, or FirmPennie & Edmonds [57] ABSTRACT A sector cable comprising a plurality of wedgeshaped, segments, composed of a plurality of compacted and twisted wire strands, arranged with side walls abutting and with the point of each wedge directed toward, but spaced from, the central axis of the cable, at least alternate segments covered on the exterior with an insulation covering comprising at least two layers of an extensible, flexible, and dense. uncreped paper, the insulated and uninsulated segments being so spaced in relation to each other that the side wall of any uninsulated segment does not abut the side wall of any other uninsulated segment.

3 Claims, 3 Drawing Figures US. Patent Oct. 21, 1975 3,914,532

F/G Z SECTOR CABLE BACKGROUND OF THE I VENTION Sector cables, also known as Segmental conductor cables, are relied upon in systemswith voltage ratings from 5,000 to 500,000 volts and require a conductor design capable of giving many decades of reliable service.

Such cables utilize a plurality of conductor segments each of which is formed of a plurality of wire strands which are first compacted and then twisted, as in a standardcabling machine,'to introduce a permanent twist into each segment so that the finished conductor will lay dead. In addition,in order to prevent shorts between conductorsegments and current losses resulting from the distortion of the current distribution due to proximity to the other currentcarrying conductor segments it is necessaryto insulate the individual segments. Not every segment need be insulated but at least a sufficient number are insulated so that the side wall of the uninsulated segment does not abut the side wall of any other uninsulated segment.

In forming the insulated segments the insulation covering is placed over the segment prior to the twisting operation. As is readily apparent the'twisting operation requires a considerable amount of torque and overtwist to produce the desired set in the segment because the segments are in a medium-hard condition because of compaction. The insulator covering on the segment is thus first exposed to the over-twist and then to the die pressure in the bushing of the cabling machine which applies the torque. The over-twist places a high tensile load on the insulating covering which can, anddoes, cause breaks in the tape. In addition, the die pressure causes wear of the insulation covering, sometimes tears through the covering, atthe comers of the segment where the bushing forces concentrate. Such breaks, wears, and tears can cause segment shorts which are obviously detrimental to the cable performance and operation.

Various insulation coverings have been tried in order to overcome this problem of shorting and current loss, such as paper made from hemp rope, nylon fabric tapes, and a combination of such nylon tape intercalated with a polyester tape, but none have been completely successful.

SUMMARY or THE INVENTION Sector cables have now been found in which there is no breakage in the insulating tape thereby substantially eliminating shorts between segments.

Briefly stated, the present invention comprises a sector cable comprising a plurality of wedge-shaped seg- .tion covering comprising at least two layers of an extensible, flexible, dense uncreped paper, the insulated and uninsulated segments being so spaced in relation to each other that the side wall of any uninsulated segment does notabut the side wall of any other uninsulated segment.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a sector cable of the instant invention;

FIG. 2 is a sectional view of a single insulated segment forming part of the sector cable; and

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2.

DETAILED DESCRIPTION Referring to thedrawings, there is shown a sector cable 10 comprising an outer protector covering, usually of a polymeric material such as rubber, plastic, or the like, which overlies a lead sheath 12. Immediately under sheath 12 is a semiconducting carbon black tape 13 intercalated with a copper shielding tape 14. The copper shielding tape 14, in turn, is placed over cable insulation (usually paper) 15 which is placed about strand shield 16. The foregoing layers of material are those conventionally used in making sector cables and they are applied in their usual thicknesses.

Indicatedas 17 are compacted conductor segments made of individual metal wire strands 20. As illustrated in FIG. 1,,every other segmental conductor 17 is cov-v ered with an insulation covering 18. In accordance with the instant invention at least alternate segments 17 must be covered on the exterior with the insulation 18. If desired, all of the segments 17 can be covered with such insulation. It will be noted that insulated and uninsulated conductor 17 are so spaced in relation to each.

other that side walls of any uninsulated conductor does not abut the side wall of any other uninsulated segment in the cable 10.

As best illustrated in FIG. 3, it is preferred to use three layers of material in forming the insulation covering 18. The first layer 30, or innermost layer, placed on top of the metal wire strands of the segment 17 is wrapped around the segment with about a 5% butt space 33'between the edges of this innermost layer. The

outer layers

31 and 32 are applied over this innermost layer with approximately 50% intercalation of these two layers. This butt space and intercalation permits, in conjunction with the required insulation material 18, the twisting of the metal wire strands to form the finished segments without any wearing or tearing of the insulation covering 18.

It is an essential feature of the instant invention that all three layers of the insulation covering 18 must be of an extensible and flexible, dense, uncreped paper. Such paper is described in detail in U.S. Pat. No. 2,624,245. It is characterized by having substantial extensibility well in excess of its primitive elastic limit in a direction parallel to its faces, the extensibility being continuous throughout it in the direction of extensibility and those fibers within the paper which extend generally lengthwise in the direction of extensibility being locally, laterally, and individually rearranged and undulating lengthwise within the paper.

The

insulation papers

30, 31 and 32 are preferably in the form of tapes that are three-quarters of an inch wide and having a thickness of 5 mils. The tapes, 30, 31 and 32 are spiral wound onto the compacted segment 17 with the butt spacing and intercalation noted above.

After application of the three tape insulation covering 18, the insulated segment is fed through a standard cabling machine of the type conventionally used for this purpose and a permanent twist introduced into the segment.

The twisted insulated and uninsulated segments are then formed into the finished cable with the various protective coverings described in the usual manner; cabling procedures being well known to those skilled in this art. I

it has been found that, with the insulation paper of the present invention, the high tensile load caused by overtwisting and the wear caused by the die pressure are eliminated. The elimination is caused not only by the nature of the paper itself and its ability to flex and extend under the tensile load and die pressure but also by the butt spacing and intercalation which permit the

insulation tapes

30, 31, and 32 to adapt to the tensile load and pressure without breaking or tearing. The result is a sector cable which is free of shorts.

The processing of the cable, aside from the application thereon of the insulating paper layer that has been extensively discussed, is'that conventionally used in making a sector cable. More specifically, a standard cabling machine is used and the protective covering 11, lead sheath 12, carbon black tape 13, copper shielding tape 14, paper insulation 15, and strand'shield l6-are those conventionally used for this purpose and are placed thereon in the usual thickness and in the'usual manner.

Whilethe invention has been described in connection with a preferred embodiment, it is not intended to limit the invention to the particular form set forth, but, on .the 'contrary,'it is intended to cover such alternatives, modifications and equivalents as may be included within the spirit and the scope of the invention as defined by the appended claims.

What is claimed is: a

1. A sectr.:,cable comprising a plurality of wedgeshaped segments, composed of a plurality of compacted and twisted wire strands, arranged with side walls abutting and with the point of each wedge directed toward, but spaced from, the central axis of the cable, at least alternate segments covered on the exterior with an insulation covering comprising at least two layers of an extensible, flexible, and dense uncreped paper, the insulated and uninsulated segments being so spaced in relation to each other that the side wall of any uninsulated segment does not abut the side wall of any other uninsulated segment, the innermost-insulation layer is wrapped around the segments with about a 5% butt space between the edge of the layer and at least one outer layer being applied over the innermost layer with approximately 50% intercalation of saidat least one outer layer. v

2. The sector cable of claim 1 wherein the insulation covering comprises three layers of said uncreped pa- 3. Asector cable comprising a plurality of wedgeshaped segments, composed of a, plurality of compacted and twisted wire strands, arranged with side walls abuttingand with the point of each wedge directed toward, but spaced from, the central axis of the cable, at least alternate segments covered on the exterior with an insulation coveringcomprising at least two layers of an extensible, flexible, and dense uncreped paper, the insulated and uninsulated segments being so spaced in relation to each other that the side wall of any uninsulated segment does not abut the side wall of any other uninsulated segment, wherein the insulation covering comprises three layers of said uncreped paper, and wherein the innermost insulation layer is wrapped around the segments with about a 5% butt space between the edge of the layer and the outer two layers being appliedvoer the innermost layer with approximately 50% intercalation of said two outer layers.

Claims

1. A sector cable comprising a plurality of wedge-shaped segments, composed of a plurality of compacted and twisted wire strands, arranged with side walls abutting and with the point of each wedge directed toward, but spaced from, the central axis of the cable, at least alternate segments covered on the exterior with an insulation covering comprising at least two layers of an extensible, flexible, and dense uncreped paper, the insulated and uninsulated segments being so spaced in relation to each other that the side wall of any uninsulated segment does not abut the side wall of any other uninsulated segment, the innermost insulation layer is wrapped around the segments with about a 5% butt space between the edge of the layer and at least one outer layer being applied over the innermost layer with approximately 50% intercalation of said at least one outer layer.

2. The sector cable of claim 1 wherein the insulation covering comprises three layers of said uncreped paper.

3. A sector cable comprising a plurality of wedge-shaped segments, composed of a plurality of compacted and twisted wire strands, arranged with side walls abutting and with the point of each wedge directed toward, but spaced from, the central axis of the cable, at least alternate segments covered on the exterior with an insulation covering comprising at least two layers of an extensible, flexible, and dense uncreped paper, the insulated and uninsulated segments being so spaced in relation to each other that the side wall of any uninsulated segment does not abut the side wall of any other uninsulated segment, wherein the insulation covering comprises three layers of said uncreped paper, and wherein the innermost insulation layer is wrapped around the segments with about a 5% butt space between the edge of the layer and the outer two layers being applied voer the innermost layer with approximately 50% intercalation of said two outer layers.