GB2134171A - Clamps for overhead conductors - Google Patents

Abstract

A overhead conductor terminating clamp for securing a conductor to a tower comprises, in combination, the surfaces of opposed side walls of a smoothly curved, channel-shaped conductor guide 3 which taper smoothly and continuously in a direction away from an end of the guide, and a wedge member 5 which has a complementary tapered surface. When a conductor C is positioned in the guide 3 and a tensile force is applied to that part of the conductor extending from the other end of the guide, the wedge member 5 is urged lengthwise to maintain it in engagement with the tapered surfaces with the conductor clamped between the wedge member and the base wall of the guide. Risk of damage to the core of the conductor and to any optical fibre loosely housed in the core is substantially reduced. <IMAGE>

Description

SPECIFICATION Overhead electrical transmission and distribution systems This invention relates to overhead electrictransmission and distribution systems ofthe kind in which at least one overhead flexible electric conductor is suspended at spaced positions along its length from towers, pylons, poles or other upstanding supports, all such upstanding supports hereinafter, for convenience, being included in the generic term "tower".

Where a length of overhead flexible electric conductor directly or indirectly suspended from a tower of an overhead electric transmission or distribution system of this kind approaches and leaves the tower in directions that differfrom one another, it is the general practice to secure the conductorto an insulator or insulator string suspended from the tower, or where the conductor is an earth conductorto the tower itself, by means of a fitting generally and hereinafter referred to as a conductor terminating clamp.

Known forms of conductorterminating clamp used forthispurposecomprisea body of metal or metal alloy having means for securing the body directly or indirectly to a tower of an overhead electric transmission or distribution system and having, integral with the body, an elongate conductor guide which is of substantially channel-shaped transverse cross-section and which is smoothly curved in the direction of its length and, at or near one end ofthe conductor guide, a separatelyformed plate and associated bolt or bolts for mechanically clamping a conductor, when positioned in the guide, between the wall ofthe conductor guide and the plate.

Where an overhead conductor to be clamped in a conductorterminating clamp has a separate optical fibre andloroptical bundle loosely housed in an elongatecompartmentwithin and extending throughoutthe length ofthe conductor, as described and claimed in the Complete Specification of our British Patent No. 1598438, we have found that there is a substantial riskthat mechanical clamping ofthe conductor between the wall of the conductor guide andtheplatewill result in distortion of the conductor and possible damage to the optical fibre andloroptical bundle. This risk is substantially increased where the plate and/or underlying su rface of the wall ofthe conductorguideistransverselycorrugatedto improve the mechanical grip on the conductor.

It is an object ofthe present invention to provide an improved conductorterminating clamp which is especially, but not exclusively, suitable for use with overhead flexible electric conductors of the kind forming the subject of our aforesaid patent.

According to the invention the improved conductor terminating clamp comprises a body of metal or metal alloy having means for securing the body directly or indirectly to a tower of an overhead electrictransmis- sion or distribution system and having, integral with the body, an elongateconductorguidewhich is of substantially channel-shaped transverse cross-section and which is smoothly curved in the direction of its length and, at or near one end of the conductor guide, means for clamping a conductor in the guide, wherein said conductor clamping means comprises, in combination, a surface of the wall ofthe conductor guide which tapers smoothly and continuously over a part ofthe length ofthe guide in a direction away from the said end of the guide, and at least one elongate wedgememberwhich hasasurfaceofcom- plementary shape to the tapered surface ofthe guide, the arrangement being such that, when a conductor is positioned in the guide and a tensile force is applied to that part ofthe conductor extending from the other end ofthe guide, the elongate wedge memberwill be urged lengthwiseto maintain it in engagementwith the tapered surface ofthe guide with the conductor clamped between the wedge member and a wall ofthe guide.

The improved conductorterminating clamp has the important advantage thatthe dimensions ofthe elongate conductorguide and the wedge member can be so arranged that, when the wedge member is in engagementwiththetaperedsurfaceoftheguide,the wedge member grips the conductorjust sifficiently to develop the necessary tension without causing any significant radial distortion ofthe conductor and, when the conductor has an elongate compartment in which at least one optical fibre is loosely housed, without imposing sufficient radial pressure on the conductor to impairthe optical transmission characteristics of the or each optical fibre.

In orderto arrangeforthewedgememberto impart a controlled and predetermined radial pressure on the conductor, preferably the wedge member is explosively driven into engagement with the tapered surface of the guide. Preferably, to limit positively the extent to which the wedge member can be driven into engagement with thetapered surface ofthe guide and thereby substantially eliminate any risk of imposing unacceptable radial pressure on the conductor, the wedge member has at least one outwardly extending protuberance which is adapted to aboutthe end face ofthe conductor guide atthe said end ofthe guide.

Preferably, the smoothly curved conductor guide is of substantially C-shaped transverse cross-section and, over a part of its length adjacent the end of the guide nearerthe conductor clamping means,substantially diametrically opposed side walls ofthe guide diverge smoothly and continuously from the central longitudinal axis of the guide in a direction towards said end,the arrangement being such thatwhen the elongate wedge member is introduced between said side walls ofthe guide it will clamp a conductor positioned in the guide against the base wall ofthe guide. The wall of the elongate wedge memberthat will be contiguous with the conductor preferably has a transverse cross-section of smoothly curved concave form.

Theanglesub-tended bythe smoothly curved elongate conductor guide may be any angle lying between 120 and 360 and, in some circumstances, may be greater than 360". Where the angle subtended by the smoothly curved conductor guide is approx imately 180 , the conductor guide is approximately kidney-shaped.Wheretheanglesub-tended bythe smoothly curved conductor guide is greater than 360 , the conductor guide is of substantially spiral form.

Preferably, the body of the improved conductor terminating clamp is made of aluminium oran aluminium-based alloy.

The invention also includes an overhead electric transmission and distribution system ofthe kind in which at least one overhead flexible electric conductor is suspended at spaced positions along its length from towers, wherein, at at least one ofthe towers, the conductor is secured to an insulatororinsulatorstring suspended from the tower, or where the conductor is an earth conductor to the tower itself, by a conductor terminating clamp comprising a body of metal or metal alloyhaving means bywhichthe body is secured directly or indirectly to the tower and having, integral with the body, an elongate conductor guide which is of substantially channel-shaped transversesection, which is smoothly curved in the direction of its length and which, at or near one end ofthe conductorguide, has awall whose surface tapers smoothly and continuously over a part ofthe length of the guide in a direction awayfrom the said end ofthe guide,the conductor extending along the guide and being clamped therein by at least one elongate wedge memberwhich has a surfaceofcomplementaryshape to thetapered surface ofthe guide and which, when a tensileforce is applied to that part ofthe conductor extending from the other end of the guide, is urged lengthwise to maintain it in engagement with the tapered surface ofthe guide with the conductor clamped between the wedge member and a wall ofthe guide.

The invention isfurtherillustrated by a description, by way of example, of three preferred forms of conductorterminating clamp with reference to the accompanying drawings, in which: Figure lisa side view of a conductorterminating clamp in which the smoothlycurved conductor guide is ofsubstantiallyspiral form; Figure 2 is a fragmental side view of an end part of the conductorterminating clamp shown in Figure 1; Figure 3 is a tranverse cross-sectional view ofthe conductorterminating clamp taking on the line Ill-Ill in Figure 2;; Figure 4 is a side view of a conductorterminating clamp in which the angle subtended by the smoothly curved conductor guide is approximately 1200 and, Figure 5 is a side view of a conductorterminating clamp in which the smoothly curved conductor guide is approximately kidney shaped.

The conductorterminating clamp shown in Figures 1 to 3 comprises a body 1 of aluminium having socket 2 by means of which the body can be indirectly secured to a tower of an overhead electrictransmission and distribution system via an insulator string and having, integral with the body, an elongate conductor guide 3 which is of substantially C-shaped transverse cross-section and which is so smoothly curved that the conductor guide subtends an angle of approximately 400" and is of substantially spiral form.

At an end part 4 ofthe conductor guide 3 diametrically opposed side walls ofthe C-shaped guide diverge smoothly and continuouslyfrom the central longitudinal axis ofthe guide in a direction towards that end and an elongate wedge member 5 is explosively driven into engagement with the surfaces ofthe tapered side walls under a controlled and predetermined pressureto clamp a conductor C, positioned in the guide and having an elongatecompartmentin which an optical fibre is loosely housed, against the base wall ofthe guide.Opposed outwardly extending protuberances 6 on opposite side faces of the wedge member 5 abutthe end face ofthe conductor guide 3 to limit positively the extentto which the wedge member can be explosively driven into the guide and therebysubstantiallyeliminateanyriskthatthe wedge memberwill impart unacceptable radial pressure on the conductor Cto impairthe optical transmission characteristics ofthe optical fibre.

When a tensile force is applied in the direction ofthe arrowAtothatpartoftheconductorC protruding from the end ofthe conductor guide remote from the wedge member 5, the wedge member is urged lengthwiseto maintain it in engagement with the surfaces ofthetapered side walls with the conductor clamped between the wedge memberandthe base wall oftheguide.Theconductorterminating clamps shown in Figures 4 and 5 operate on the same principle as the conductorterminating clamp shown in Figures 1 to 3 exceptthatthe conductor guide of the terminating clamp shown in Figure 4subtends an angle of approximately 120" and the conductorguide oftheterminating clamp shown in Figure 5 subtends an angle of approximately 220". The conductor terminating clamp shown in Figure 4 comprises an aluminium body 11 having an aperture 12 by means of which the body can be directly or indirectly secured to a tower and an elongate conductor guide 13 of C-shaped transverse cross-section which is smoothly curved and subtends an angle of approximately 1200.

At an end part 14 ofthe conductor guide 13, diametrically opposed side walls of the C-shaped guide diverge smoothly and continuously from the axis ofthe guide and an elongate wedge member 15, explosively driven into engagement with the surfaces ofthetapered side walls under a controlled and predetermined pressure, clamps a conductor C, positioned in the guide, againstthe basewall ofthe guide.

The conductorterminating clamp shown in Figure 5 is of substantially kidney-shape and comprises an aluminium body 21 having a socket 22 by means of which the body can be indirectly secured to the tower via an insulator string. A smoothly curved elongate conductor guide 23 of C-shaped transverse crosssection subtends an angle of approximately 220 and, at an end part 24 ofthe conductor guide, diametrically opposed side walls ofthe C-shaped guide diverge smoothly and continuously from the axis ofthe guide.

An elongate wedge member 25 is explosively driven into engagementwith the surfaces ofthetapered side walls under a controlled and predetermined pressure, clamps a conductor C, positioned in the guide, against the base wall ofthe guide.

Claims (9)

1. A conductorterminating clamp comprising a body of metal or metal alloy having meansfor securing the body directly or indirectlyto a tower of an overhead electric transmission or distribution system and having, integral with the body, an elongate conductor guide which is of substantially channelshaped transverse cross-section and which is smoothly curved in the direction of its length and, at or near one end of the conductor guide, means for clamping a conductor in the guide, wherein said conductor clamping means comprises, in combination, a surface afthewall of the conductor guide which tapers smoothty and continuously over a part of the length of the guide ina direction awayfrom the said end of the guide, and at least one elongate wedge member which has a surface of complementary shape to the tapered surface ofthe guide, the arrangement being such that, when a conductor is positioned in the guide and a tensile force isapplied to that partofthe conductor extendingfrom the other end of the guide, the elongate wedge member will be urged lengthwise to maintain itin engagementwiththetapered surface of the guide with the conductor clamped between the wedge member and a wall ofthe guide.

2. Aconductorterminating clamp as claimed in Claim 1,wherein the smoothly curved conductor guide is of substantially C-shaped transverse crosssection and, overa part of its length adjacent the end ofthe guide nearer the conductor clamping means, substantially diametrically opposed side walls ofthe guide diverge smoothly and continuouslyfrom the central longitudinal axis ofthe guide in a direction towards said end, the arrangement being such that when the elongate wedge member is introduced between said side walls ofthe guide it will clamp a conductor positioned in the guide againstthe base wall ofthe guide.

3. Aconductorterminating clamp as claimed in Claim 1 or2, wherein the wall of the elongate wedge memberthatwill be contiguous with the conductor has a transverse cross-section of smoothly-curved concave form.

4. A conductorterminating clamp as claimed in any one ofthe preceding Claims, wherein the wedge member has at least one outwardly extending pro tuberancewhich is adapted to abutthe end face ofthe conductor guide at the said end of the guide.

5. Aconductorterminating clamp as claimed in any one ofthe preceding Claims, wherein the angle subtended by the smoothly curved elongate conductor guide lies between 120" and 360".

6. Aconductorterminating clamp as claimed in any one of Claims 1 to 4, wherein the angle subtended bythe smoothly curved conductor guide is greater than 360".

7. A conductorterminating clamp as claimed in any one ofthe preceding Claims, wherein the body of the clamp is made of aluminium or an aluminium based alloy.

8. An overhead electric transmission or distribution system ofthe kind in which at least one overhead flexible electricconductoris suspended at spaced positions along its length from towers, wherein, at at least one ofthe towers, the conductor is secured to an insulator or insulator string suspended from the tower, or where the conductor is an earth conductorto the tower itself, by a conductorterminating clamp comprising a body of metal or metal alloy having means by which the body is secured directly or indirectly to thetower and having, integral with the body, an elongate conductor guide which is of substantially channel-shaped transverse cross-section, which is smoothly curved in the direction of its length and which, at or near one end of the conductor guide, has a wall whose surface tapers smoothly and continuously over a length ofthe guide in a direction awayfrom the said end ofthe guide, the conductor extending along the guide and being clamped therein by at least one elongate wedge memberwhich has a surface of complementary shape to the tapered surface ofthe guide and which, when a tensile force is applied to that part ofthe conductor extending from the other end of the guide, is urged lengthwise to maintain it in engagement with the tapered surface of the guide with the conductor clamped between the wedge member and the wall ofthe guide.

9. Aconductorterminating clamp substantially as hereinbefore described with reference to, and as shown in Figures 1 to 3, Figure 4 or Figure 5 ofthe accompanying drawings.