ARMOURED POWER CABLE

Abstract

An armoured power cable (10) comprises a cable core (11) and an armour layer (21) comprising a plurality of armouring wires (22) laid around the cable core (11), wherein at least 10% of the armouring wires (22) are wavy wires (23) having a zig-zag shape laying on the outer surface of the cable core (11).

Claims

1. An armoured power cable comprising a cable core and an armour layer comprising a plurality of armouring wires laid around the cable core, wherein at least 10% of the armouring wires are wavy wires having a zig-zag shape laying on an outer surface of the cable core.

2. The armoured power cable according to claim 1, wherein the armour layer comprises from 20% to 40% wavy wires with respect to a total number of the armouring wires.

3. The armoured power cable according to claim 1, wherein each wavy wire has substantially constant peak-to-peak amplitude (P) and wavelength (W), and a diameter (D).

4. The armoured power cable according to claim 1, wherein all of the wavy wires have substantially constant peak-to-peak amplitude (P) and wavelength (W).

5. The armoured power cable according to claim 1, wherein the armouring wires are made of metal.

6. The armoured power cable according to claim 3, wherein each wavy wire has a wavelength (W) of (X′.Math.D)+D, where X′ is a value between 0.5 and 30.0 and D is a diameter of the wavy wire.

7. The armoured power cable according to claim 3, wherein each wavy wire has a peak-to-peak amplitude (P) of (X″.Math.D)+D where X″ is a value between 0.5 and 5.0 and D is a diameter of the wavy wire.

8. The armoured power cable according to claim 1, wherein all of the armouring wires are wavy wires laid parallel to one another the cable core.

9. The armoured power cable according to claim 8, wherein the wavy wires are laid with infinite length lay over the cable core.

10. The armoured power cable according to claim 9 comprising a binder around the armour layer.

11. The armoured power cable according to claim 1, wherein the outer surface of the cable core has a generic cylindrical shape including flat portions and curved portions, and each wavy wire having the zig-zag shape extends on a flat portion of the outer surface of the cable core.

12. The armoured power cable according to claim 1, wherein the plurality of armouring wires each has a diameter ranging from 0.2 mm to 8 mm.

13. The armoured power cable according to claim 1, wherein the plurality of armouring wires have substantially a same diameter.

14. The armoured power cable according to claim 1, wherein the plurality of armouring wires each has a round cross section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The present cable will be now described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the cable are shown.

[0062] Drawings illustrating the embodiments are not to scale representations.

[0063] For the purpose of the present description and of the appended claims, use of the “a” or “an” are employed to describe elements and components of the disclosure. This is done merely for convenience and to give a general sense of the disclosure. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

[0064] For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term “about”. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

[0065] FIG. 1 shows a schematic perspective view of an armoured power cable according to the present disclosure;

[0066] FIG. 2 shows a schematic lateral view of an embodiment of an armoured power cable according to the present disclosure;

[0067] FIG. 3 shows a schematic lateral view of another embodiment of an armoured power cable according to the present disclosure;

[0068] FIG. 4 shows a schematic cross section along the plane Iv-Iv of the armoured power cable of FIG. 1;

[0069] FIG. 5 show a magnified view of a detail of the armoured power cable of FIG. 2; and

[0070] FIG. 6 shows a manufacturing line of the cable of the present disclosure.

DETAILED DESCRIPTION

[0071] An armoured power cable according to the present disclosure is indicated with the reference number 10 in FIG. 1.

[0072] As illustrated in FIG. 1, the armoured power cable 10 comprises a cable core 11 for carrying direct current or alternate current and extending along a longitudinal direction L.

[0073] The cable core 11 comprises three electric conductors 12 made of an electrically conductive metal, such as copper or aluminium or both, in form, as an example, of a rod, stranded wires, profile wire or segmental conductor.

[0074] The electric conductor 12 is surrounded by an insulating system 13 which can comprise an inner semiconducting layer 14, an insulating layer 15 and an outer semiconducting layer 16 (illustrated in FIG. 4).

[0075] The inner semiconducting layer 14, the insulating layer 15 and outer semiconducting layer 16 can be made of extrudable polymeric materials, such as polyethylene, crosslinked polyethylene (XLPE), ethylene propylene rubber (EPR) or a propylene compound. The material of the inner and of the outer semiconducting layers 14, 16 are added with a conductive filler, such as carbon black. Alternatively, the insulating layer 15 can be made of paper or paper-polypropylene tapes impregnated with suitable viscosity oil.

[0076] The cable core 11 further comprises a metallic screen 17 surrounding the insulating system 13, as illustrated in FIGS. 1 and 4.

[0077] The metallic screen 17 can be made of lead alloy or copper or aluminium in form of tape, wires or braids.

[0078] The three conductor 12 with their relevant insulating system 13 are stranded and embedded in a bedding or interstitial filler material 20 (FIG. 4), made, for example, of extrudable polymeric material or of fibrous material.

[0079] The bedding 20 is surrounded by a protecting layer 19 which can be composed by one or more sub-layers such as a water barrier made of metal or a composite polymer/metal, polyester tapes.

[0080] Over the cable core 11 it is provided an armour layer 21 comprising a layer of a plurality 22 of metal armouring wires. In some embodiments, the plurality of metal armouring wires is made of steel.

[0081] In the present embodiment, each of the plurality of metal armouring wires 22 has a minimum tensile strength of 125 N/mm.sup.2. When an armouring wire of the plurality 22 is a galvanized steel wire, it has an electric resistance less than 3.0 ohm/Km; this compares with the cable specification for the armouring wire of the plurality 22 made of a drawn metal, which has a required electric resistance less than 4.0 ohm/Km.

[0082] The armouring wires of the plurality 22 have a constant circular cross section.

[0083] A jacket 26 surrounds the armoured layer 21. The jacket 26 can be made of polypropylene yarns or high density polyethylene.

[0084] According to the present disclosure, at least 10% of the armouring wires of the plurality 22 are wavy wires 23 zig-zag shaped in a plane laying on the outer surface of the cable core 11. The other armouring wires of the plurality 22 are straight wires 24

[0085] The wavy wires 23 can have a substantially sinusoidal shape or a substantially triangular wave shape. The specific shape of the wavy wires 23 depends on the process for manufacturing the wavy wires 23, as will be discussed hereinafter.

[0086] As detailed in FIG. 5, a wavy wire 23 comprises a succession of peaks 23a, at which the wavy wire 23 course changes direction. The peaks 23a are evenly distributed along the longitudinal axis A of the wavy wire 23. Two successive peaks 23a are connected by a connecting portion 23b having an arcuate or straight shape.

[0087] A wavy wire 23 has a wavelength W, a peak to peak amplitude P and a diameter D.

[0088] In an embodiment, all the wavy wires 23 have substantially the same wavelength W which is thus constant along each wavy wire 23.

[0089] In an embodiment, all the wavy wires 23 have the substantially same peak to peak amplitude P which is thus constant along each wavy wire 23.

[0090] In an embodiment, the plurality of armouring wires 22 amount to from 15 to 60 armouring wires 23, 24, in particular from 24 to 44 armouring wires 23, 24.

[0091] In the embodiment of FIG. 2 the plurality of metal armouring 22 are helically wound around the cable core 11 along a winding direction F. The plurality 22 comprises both wavy wires 23 and straight wires 24 which are helically wound with the same lay length.

[0092] A group of four straight wires 24, adjacent and substantially in direct contact one another, alternate to one wavy wire 23.

[0093] In an embodiment, as illustrated in FIG. 2, the peaks 23a of each wavy wire 23 are in direct contact with two straight wires 24 belonging to different groups of four. By this configuration of the plurality 22 of armouring wires, gaps 25 in the armour layer 21 are formed between a wavy wire 23 and two straight wires 24.

[0094] A sequence of gaps 25 extends along the wire winding direction F. The dimension of each gap 25 is given by the wavelength W and the peak amplitude P of each wavy wire 23.

[0095] In the embodiment of FIG. 3, the plurality 22 of armouring wires comprises only wavy wires 23. All the wavy wires 23 extend parallel each other along the cable longitudinal direction L and they do not overlap each other, while contacts among them could allow dissipation of current.

[0096] By this configuration of wavy wires 23, the gaps 25 in the armour 21 can be formed between adjacent wavy wires 23, as illustrated in FIG. 3.

[0097] In the illustrated embodiment, the peaks 23a of adjacent wavy wires 23 are slightly misaligned in the circumferential direction C, so as the connecting portions 23b of adjacent wavy wires 23. Some contact points for dissipating current are present

[0098] In an alternative embodiment, not illustrated, the peaks 23a of adjacent wavy wires 23 can be aligned in the circumferential direction C, and the connecting portions 23b of adjacent wavy wires 23 are substantially parallel each other. In this embodiment, substantially no gaps are present in the armoured layer 21 and the contact for dissipating current is more extended.

[0099] In the embodiment of FIG. 3, the wavy wires 23 are held in position by a binder 27 in form of a continuous tape helically wound over the armouring wires 23.

[0100] The cable of the present disclosure where the armouring wires are helically wound around the cable core can be manufactured by a line as from FIG. 6.

[0101] The cable core 101 is unwound from a drum 102 held in a pay-off stand 103. The pay-off stand 103 drives the drum 102 such that the cable core 100 is rotated perpendicular to the axis of the manufacturing line. The required number of metal armouring wires 104 are paid off from individual spools 105. The armouring wires 104 pass through banks of tensioning pulleys 106 which include the forming gears for shaping some straight armouring wire into wavy wire.

[0102] In particular, the wavy wires can be manufactured by passing a straight wire through a clearance provided between two forming gears. The teeth profile of the two gears, as well as their diameters, are substantially identical. The distance that divides the two gears (clearance), is set to allow the teeth of the two gears to engage each other without causing undue stress to the wire. When a straight wire pass through the clearance between the two gears, the teeth of the gears plastically deform it and provided a zig-zag shaped (or wavy) wire. The shape of the corrugation depends on the profiles of the teeth.

[0103] The armouring wires are then pass through a grouping die 107 and helically wound around the cable core 102 resulting in an armoured cable 108. The armoured cable 108 is hauled off using a device 109 such as a caterpillar. The haul off device 109, the take-up drum 110, and the take-up stand 111 are turned around the circumference of the cable at the same speed and direction of with the pay-off drum 102.

[0104] The cable of the present disclosure where the armouring wires are all wavy wires laid with infinite length lay around the cable core (parallel to the longitudinal cable axis) can be manufactured by a line analogous to that of FIG. 6 having the following differences: a) the pay-off stand 103 driving the drum 102 does not rotate the cable core; b) a delivering device for providing the armoured cable 108 of a binder can be optionally provided before the haul off device 109.

[0105] The armoured cable 108 can be directly covered with a polymeric jacket by extrusion.