EP4629266A1

EP4629266A1 - Submarine cable having shielding layer that considers dynamic characteristics

Info

Publication number: EP4629266A1
Application number: EP23898330.8A
Authority: EP
Inventors: Jae Bok Lee; Chul Min Kim; Kyoung Soo Kim
Original assignee: LS Cable and Systems Ltd
Current assignee: LS Cable and Systems Ltd
Priority date: 2022-11-30
Filing date: 2023-11-30
Publication date: 2025-10-08
Also published as: KR20240081426A; WO2024117806A1

Abstract

The disclosure relates to a submarine cable including a shielding layer in consideration of dynamic characteristics. Specifically, the disclosure relates to a submarine cable including a shielding layer that is configured in consideration of dynamic characteristics, in which the shielding layer is capable of sufficiently performing a path for fault current and a shielding function, while simultaneously achieving excellent durability in dynamic environments such as under the sea, by considering dynamic characteristics in which deformation is continuously applied due to external force in a conducting state.

Description

[Technical Field]

[Background Art]

The submarine cable has been installed for a long time for power transmission to island regions and intercontinental communication connections, and may be fixed and laid on the seabed by section or may be connected from the seabed to offshore wind turbines or offshore substations while being suspended above the seabed. The submarine cable installed in sections that are separated from the seabed may be subjected to movement caused by ocean currents or waves, or bending loads due to flexure. Such sections of the submarine cable are particularly referred to as dynamic sections, and in these dynamic sections, the aforementioned movement and flexure need to be ensured. Therefore, it is difficult to apply a metal sheath-type shielding layer, such as a lead sheathing, which hinders such movement or flexure, to the submarine cable.
FIG. 1 schematically illustrates a state of a core that may be included one or more times in a conventional submarine cable.
As illustrated in FIG. 1, the core may include a conductor 31, an inner semiconductive layer 32 surrounding the conductor 31, an insulation layer 33 surrounding the inner semiconductive layer 32, an outer semiconductive layer 34 surrounding the insulation layer, a water-blocking layer 35 surrounding the outer semiconductive layer 34, and a metal shielding layer 36 surrounding the water-blocking layer 35.
The metal shielding layer 36 may be formed of a plurality of metal wires 36a arranged at intervals, which is more advantageous for movement or flexure of the submarine cable than a lead metal shielding layer. However, in the event of a fault current, current flows only through one adjacent wire 36a to the grounded cable end, and thus the metal shielding layer cannot effectively perform the function of a path for fault current. To sufficiently perform the function of a path for fault current by distributing the fault current to all the wires, a metal tape 36b configured to enclose and conductively connect all the metal wires 36a may be additionally provided.
Here, the metal tape 36b may be made of, for example, a copper tape, and in the metal shielding layer 36 of such a structure, the metal wires 36a and the metal tape 36b may strongly restrain each other due to repeated bending or tension of the submarine cable, causing problems such as disconnection of the metal wires 36a or breakage of the metal tape 36b. As a result, the metal shielding layer 36 may fail to perform its functions as a path for fault current and a shielding function.
Therefore, there is an urgent need for a submarine cable including a shielding layer capable of sufficiently performing the path for fault current and shielding function, while simultaneously achieving excellent durability in dynamic environments, such as a dynamic section of a submarine cable, by considering dynamic characteristics in which deformation is continuously applied due to external force in a conducting state.

[Disclosure]

[Technical Problem]

The disclosure is directed to providing a submarine cable including a shielding layer capable of sufficiently performing the path for fault current and shielding function, while simultaneously achieving excellent durability in dynamic environments, such as a dynamic section of a submarine cable, by considering dynamic characteristics in which deformation is continuously applied due to external force in a conducting state.

[Technical Solution]

To achieve the objects, the disclosure is directed to providing
a submarine cable. The submarine cable may include: at least one core including a conductor, an inner semiconductive layer surrounding the conductor, an insulation layer surrounding the inner semiconductive layer, an outer semiconductive layer surrounding the insulation layer, and a metal shielding layer surrounding the outer semiconductive layer; and a cable protection layer surrounding an outer side of the at least one core, in which the metal shielding layer includes a plurality of braided bodies, each formed by weaving braided strands in which a plurality of metal elementary wires are twisted together, and wherein the plurality of braided bodies are each formed by circumferentially winding, without overlapping with each other.
Here, each of the plurality of braided bodies may be at least partially in contact, at side surfaces of both ends thereof in a width direction, with a side surface of an adjacent braided body.
In addition, each of the plurality of braided bodies may have a thickness of 1 to 2 mm.
Further, a total cross-sectional area of the plurality of braided bodies may be 0.5 to 8 mm², a cross-sectional area of a single braided strand forming the braided body may be 0.08 to 0.26 mm², and a twisting pitch length of the braided strand may be 5 to 100 mm.
Here, a metal tape layer that is electrically in contact with each of the plurality of braided bodies may be further provided on an upper portion or lower portion of the metal shielding layer.
Meanwhile, the metal tape layer may be formed by circumferentially winding a wire, tape, or braided body made of a metal material.
Here, the core may further includes: an inner water-blocking tape layer provided between the outer semiconductive layer and the metal shielding layer and surrounding the outer semiconductive layer; an outer water-blocking tape layer surrounding the metal shielding layer; and a core jacket surrounding the outer water-blocking tape layer.
In addition, the inner water-blocking tape layer or the outer water-blocking taping layer may include at least one selected from a group consisting of powder, tape, coating layer, and film that include a super absorbent polymer (SAP).
Meanwhile, the submarine cable may include a plurality of cores, and a cable filler is provided in a region between the cores.
In addition, the cable protection layer may include: a binding taping layer configured to finish the plurality of cores and the cable filler in a circular arrangement; a bedding layer formed outside the binding taping layer and including polypropylene yarn; an armor layer provided outside the bedding layer; and an outermost layer formed outside the armor layer and including a polymer resin material.

[Advantageous Effects]

The submarine cable according to the disclosure exhibits excellent effects in that, by including a shielding layer having a novel structure, it is capable of sufficiently performing a path for fault current and a shielding function, while simultaneously achieving superior durability in dynamic environments such as under the sea, by considering dynamic characteristics in which deformation is continuously applied due to external force in a conducting state.

[Description of Drawings]

FIG. 1 schematically illustrates a state of a core that may be included one or more times in a conventional submarine cable.
FIG. 2 is a cross-sectional view illustrating one embodiment of a submarine cable according to the disclosure.
FIG. 3 schematically illustrates one embodiment of a core included in the submarine cable illustrated in FIG. 2.
FIG. 4 schematically illustrates another embodiment of a core included in the submarine cable illustrated in FIG. 2.
FIGS. 5A to 5C illustrates an embodiment of a metal shielding layer in the core illustrated in FIG. 3.

[Mode for Disclosure]

Hereinafter, exemplary embodiments of the disclosure will be described in detail with reference to the accompanying drawings. However, the disclosure is not limited to the exemplary embodiments to be described below and may be specified as other aspects. On the contrary, the embodiments introduced herein are provided to make the disclosed content thorough and complete, and sufficiently transfer the spirit of the disclosure to those skilled in the art. Like reference numerals indicate like constituent elements throughout the specification.
FIG. 2 is a cross-sectional view illustrating one embodiment of a submarine cable according to the disclosure, and FIG. 3 schematically illustrates one embodiment of a core included in the submarine cable illustrated in FIG. 2.
A submarine cable 1000 according to the disclosure may be a three-phase alternating current power cable in which three cores 300a, 300b, and 300c are disposed in a triangular shape, as illustrated in FIG. 2. A cable filler 400 may be provided to form the three cores 300a, 300b, and 300c into a circular shape, the cable filler 400 including fillers 400a, 400b, and 400c made of a plastic material and disposed in regions between adjacent cores. At least one of the fillers 400a, 400b, and 400c of the cable filler 400 may be provided with an optical fiber accommodating portion a, which may accommodate and mount at least one optical unit 100 having a plurality of optical fibers.
Here, the optical unit 100 may include at least one optical fiber 110 and a tube 120 that accommodates the optical fiber 110. Each optical unit 100 may include a predetermined number of optical fibers 110 mounted with a filling material inside the tube 120, and the tube may be made of a material having rigidity such as stainless steel. The optical unit 100 may further include a sheath 130 surrounding the tube 120.
The cable filler 400 is generally made of a plastic material, and preferably, a foamed plastic material is primarily used. When forming the submarine cable by assembling the cores 300a, 300b, and 300c, the optical unit, and the fillers, they may be assembled in a circular arrangement with a predetermined pitch.
Further, the submarine cable according to the disclosure includes a cable protection layer that surrounds the one or more cores, and, according to the embodiment of the disclosure illustrated in FIG. 2, the cable protection layer may include a binding tape layer 500, a bedding layer 600, an armor layer 700, and an outermost layer 800.
That is, the binding tape layer 500 may be provided to finish the three cores 300a, 300b, and 300c and the cable filler 400 in a circular arrangement.
Outside the binding tape layer 500, the bedding layer 600 may be provided. The bedding layer 600 may serve to provide a mounting surface on which the armor layer 700, disposed on the outer side thereof, is mounted.
Here, the bedding layer 600 may be configured to include polypropylene (PP) yarn. Outside the bedding layer 600, the armor layer 700 may be provided, and the armor layer 700 may include armor wires 710 disposed therein to protect the submarine cable from harsh submarine environments, and may be formed in a plurality of layers, including a lower layer 700a and an upper layer 700b.
Outside the armor layer 700, the outermost layer 800 including a polymer resin material may be provided to complete the submarine cable for offshore wind power applications.
As illustrated in FIGS. 2 and 3, the core 300 may be configured to sequentially include a conductor 310, an inner semiconductive layer 320, an insulation layer 330, an outer semiconductive layer 340, an inner water-blocking tape layer 350, a metal shielding layer 360, an outer water-blocking tape layer 370, a core jacket 390, and the like.
The conductor 310 serves as a path through which current flows to transmit electric power, and may be made of a metal material such as copper or aluminum, which has excellent electrical conductivity and appropriate mechanical strength and flexibility for cable manufacturing and usage, in order to minimize power loss.
The conductor 310 may be a circular compressed conductor, in which a plurality of round wires are stranded together and compressed into a circular shape. Alternatively, the conductor 310 may be a flat rectangular conductor that includes a center round wire and a flat rectangular wire layer stranded to surround the center round wire, and has an overall circular cross-section. Compared to the circular compressed conductor, the flat rectangular conductor may have a relatively higher space factor, thereby providing an advantage of reducing the outer diameter of the cable.
However, the conductor 310 may have a non-smooth surface, thereby potentially causing a non-uniform electric field, and in local regions, corona discharge may easily occur. In addition, when a void is formed between the surface of the conductor 310 and the insulation layer 330 to be described below, the electric field may be concentrated in the void, resulting in a deterioration of insulation performance.
Therefore, the inner semiconductive layer 320 may be provided on the outside of the conductor 310. The inner semiconductive layer 320 may exhibit semiconductivity by incorporating conductive particles such as carbon black, carbon nanotubes, carbon nanoplates, or graphite into an insulating material.
The inner semiconductive layer 320 performs a function of stabilizing insulation performance by preventing abrupt electric field variations between the conductor 310 and the insulation layer 330 to be described below. Additionally, the inner semiconductive layer 320 may suppress non-uniform charge distribution on the surface of the conductor, thereby making the electric field uniform, and may prevent void formation between the conductor 310 and the insulation layer 330, thus suppressing corona discharge, dielectric breakdown, and the like.
The insulation layer 330 is provided outside the inner semiconductive layer 320 and electrically insulates the conductor 310 from the outside so that current does not leak externally along the conductor 310. In general, the insulation layer 330 needs to have a high breakdown voltage and be capable of maintaining stable insulation performance over a long period. Further, the insulation layer 13 needs to have low dielectric loss and thermal resistance properties such as heat resistance. Therefore, the insulation layer 330 may be formed using polyolefin resins such as polyethylene and polypropylene, and preferably, polyethylene resin may be used. Here, the polyethylene resin may be formed of cross-linked polyethylene (XLPE).
The outer semiconductive layer 340 may be provided outside the insulation layer 330. The outer semiconductive layer 340 may be formed of a material that has semiconductivity by incorporating conductive particles, such as carbon black, carbon nanotubes, carbon nanoplates, or graphite, into an insulating material, similar to the inner semiconductive layer 320, and may serve to stabilize insulation performance by suppressing non-uniform charge distribution between the insulation layer 330 and the metal shielding layer 360 to be described below. In addition, the outer semiconductive layer 340 may smooth the surface of the insulation layer 330 in the cable, thereby mitigating electric field concentration and preventing corona discharge, and may also perform a function of physically protecting the insulation layer 330.
The metal shielding layer 360 may be provided outside the outer semiconductive layer 340. The metal shielding layer 360 may serve as a path through which a fault current flows, as it is grounded at the end of the cable in the event of a ground fault or short circuit, and may also perform a shielding function to prevent the electric field from being discharged to the outside of the cable.
As illustrated in FIG. 3, the metal shielding layer 360 may be formed by circumferentially winding, on a lower structure of the core 300, for example, on the outer semiconductive layer 340, a plurality of braided bodies, each of which is braided from braided strands formed by twisting together multiple copper wires having high electrical conductivity, in a manner such that the braided bodies do not overlap with each other, so as to smoothly perform a fault current path function and a shielding function.
The plurality of divided braided bodies constituting the metal shielding layer 360 may behave independently during repeated bending or tension of the submarine cable, such that bending or movement of the submarine cable caused by ocean currents or waves in dynamic environments, such as on the seabed, is ensured. In addition, unlike the conventional configuration in which a metal shielding layer is formed by a combination of metal wires and metal tapes, the above configuration may implement superior durability in dynamic environments.
Here, since the plurality of braided bodies do not overlap with each other during circumferentially winding, it is possible to prevent localized thickness nonuniformity of the metal shielding layer 360 caused by overlapping, and accordingly, to prevent compression or damage to the lower structure. However, each braided body may be at least partially in contact, at side surfaces of both ends thereof in the width direction, with the side surface of an adjacent braided body, such that, when a fault current occurs, the fault current is shared throughout the entire metal shielding layer 360, thereby enabling the fault current path function to be performed more smoothly.
FIG. 4 schematically illustrates another embodiment of a core included in the submarine cable illustrated in FIG. 2.
As illustrated in FIG. 4, a metal tape layer 380 that is in direct electrical contact with the metal shielding layer 360 may be additionally provided on the lower portion or upper portion of the metal shielding layer 360,
for example, between the inner water-blocking tape layer 350 and the metal shielding layer 360, or between the metal shielding layer 360 and the outer water-blocking tape layer 370. When, due to the behavior such as bending or other movement of the submarine cable, the plurality of braided bodies constituting the metal shielding layer 360 are not in contact with one another at their side surfaces, the fault current, upon occurrence, may not be shared across the entire metal shielding layer 360, and as a result, the metal shielding layer 360 may fail to smoothly perform its function as a path for fault current.
Therefore, by additionally providing the metal tape layer 380 on the lower portion or upper portion of the metal shielding layer 360 such that the metal tape layer 380 contacts each of the plurality of braided bodies constituting the metal shielding layer 360, even when the plurality of braided bodies are not in contact with one another at their side surfaces, the fault current may still be shared across the entire metal shielding layer 360.
Specifically, the metal tape layer 380 may be formed by circumferentially winding, around the inner water-blocking tape layer 350, a metal material having excellent electrical conductivity, such as copper, in the form of a wire, tape, or braided body, etc. In addition, the circumferential winding direction of the metal wire or the like that forms the metal tape layer 380 may be the same as or different from the circumferential winding direction of the plurality of braided bodies constituting the metal shielding layer 360. FIGS. 5A to 5C illustrate an embodiment of the metal shielding layer in the core shown in FIG. 3.
As illustrated in FIG. 5A, the metal shielding layer 360 may be divided and configured into two braided bodies 361 and 362, as illustrated in FIG. 5B, it may be divided and configured into three braided bodies 363, 364, and 365, and as illustrated in FIG. 5C, it may be divided and configured into four braided bodies 366, 367, 368, and 369.
As the number of divided braided bodies increases, it becomes more advantageous for ensuring bending or tension of the submarine cable, but, it becomes disadvantageous in terms of sharing the generated fault current. Therefore, the number of divided braided bodies may be appropriately selected in consideration of the outer diameter or the number of cores 300, or other structural characteristics of the submarine cable.
In particular, the thickness of each of the plurality of braided bodies constituting the metal shielding layer 360 may be 1 to 2 mm, and preferably, 1.5 to 2 mm. Here, when the thickness of the braided body is less than 1 mm, the durability of the metal shielding layer 360 may deteriorate, and it may be easily damaged during bending or tension of the submarine cable. Additionally, due to an increase in overall resistance, the fault current path function may be insufficiently performed. On the other hand, when the thickness of the braided body exceeds 2 mm, the thickness of the braided body becomes unnecessarily large, thereby unnecessarily increasing the outer diameter and weight of the submarine cable, and also increasing the manufacturing cost of the submarine cable due to the increased amount of copper wires used in forming the braided body.
For example, the total cross-sectional area of the plurality of braided bodies, each having the above-mentioned thickness, may be 0.5 to 8.0 mm², and the cross-sectional area of each braided strand forming the braided body may be 0.08 to 0.26 mm². The twisting pitch length of the braided strand, that is, the twisting pitch length of the plurality of elementary wires constituting a single braided strand, may be 5 to 100 mm. In consideration of the total cross-sectional area of the braided body, the cross-sectional area of the braided strand, and the twisting pitch length, the number of braided strands forming each braided body, i.e., the braided strand count of the braid body, may be appropriately selected.
Further, the core 300 may further include at least one water-blocking taping layer for moisture absorption on the outside of the outer semiconductive layer 340. The water-blocking taping layer may be provided at at least one of the inside or outside of the above-described metal shielding layer 360. In the embodiments illustrated in FIGS. 2 and 3, the water-blocking taping layer is shown to include both an inner water-blocking taping layer 350 on the inner side of the metal shielding layer 360 and an outer water-blocking taping layer 370 on the outer side thereof.
However, since moisture primarily penetrates from the outside, only the outer water-blocking taping layer 370 may be provided.
The water-blocking tape forming the water-blocking taping layer may be configured in the form of a powder, tape, coating layer, or film, etc. that includes a super absorbent polymer (SAP) having excellent performance in rapidly absorbing moisture that has penetrated the cable and maintaining the absorbed state in a swollen condition, and serves to prevent moisture penetration along the longitudinal direction of the cable. The water-blocking taping layer may also have semiconductivity in order to prevent abrupt electric field variations. The water-blocking taping layer may be configured to have a thickness of 0.2 millimeters (mm) to 1.4 millimeters (mm).
A core jacket 390 may be provided outside the outer water-blocking taping layer 370. The core jacket 390 forms the outermost part of the core, and serves to enhance corrosion resistance and water-blocking performance, while protecting the cable core from various environmental factors that may affect the power transmission performance of the cable, such as moisture penetration, mechanical damage, corrosion, and fault current. Meanwhile, the core jacket 390 may be formed of a resin, such as polyethylene.
While the disclosure has been described above with reference to the exemplary embodiments, it may be understood by those skilled in the art that the disclosure may be variously modified and changed without departing from the spirit and scope of the disclosure disclosed in the claims. Therefore, it should be understood that any modified embodiment that essentially includes the constituent elements of the claims of the disclosure is included in the technical scope of the disclosure.

Claims

A submarine cable, comprising:
at least one core including a conductor, an inner semiconductive layer surrounding the conductor, an insulation layer surrounding the inner semiconductive layer, an outer semiconductive layer surrounding the insulation layer, and a metal shielding layer surrounding the outer semiconductive layer; and

a cable protection layer surrounding an outer side of the at least one core,
wherein the metal shielding layer includes a plurality of braided bodies, each formed by weaving braided strands in which a plurality of metal elementary wires are twisted together, and wherein the plurality of braided bodies are each formed by circumferentially winding, without overlapping with each other.
The submarine cable of claim 1, wherein each of the plurality of braided bodies is at least partially in contact, at side surfaces of both ends thereof in a width direction, with a side surface of an adjacent braided body.
The submarine cable of claim 1, wherein each of the plurality of braided bodies has a thickness of 1 to 2 mm.
The submarine cable of claim 3, wherein a total cross-sectional area of the plurality of braided bodies is 0.5 to 8 mm², wherein a cross-sectional area of a single braided strand forming the braided body is 0.08 to 0.26 mm², and wherein a twisting pitch length of the braided strand is 5 to 100 mm.
The submarine cable of claim 1, wherein a metal tape layer that is electrically in contact with each of the plurality of braided bodies is further provided on an upper portion or lower portion of the metal shielding layer.
The submarine cable of claim 5, wherein the metal tape layer is formed by circumferentially winding a wire, tape, or braided body made of a metal material.
The submarine cable of claim 1, wherein the core further comprises:
an inner water-blocking tape layer provided between the outer semiconductive layer and the metal shielding layer and surrounding the outer semiconductive layer;

an outer water-blocking tape layer surrounding the metal shielding layer; and

a core jacket surrounding the outer water-blocking tape layer.
The submarine cable of claim 7, wherein the inner water-blocking tape layer or the outer water-blocking taping layer includes at least one selected from a group consisting of powder, tape, coating layer, and film that include a super absorbent polymer (SAP).
The submarine cable of claim 1 or 2, wherein the submarine cable comprises a plurality of cores, and
a cable filler is provided in a region between the cores.
The submarine cable of claim 9, wherein the cable protection layer comprises:
a binding taping layer configured to finish the plurality of cores and the cable filler in a circular arrangement;

a bedding layer formed outside the binding taping layer and including polypropylene yarn;

an armor layer provided outside the bedding layer; and

an outermost layer formed outside the armor layer and including a polymer resin material.