Submarine cable

Abstract

The present invention relates to a submarine cable in which the structure and shape of shielding wires and a shielding member constituting a metallic shielding layer are optimized to prevent damage to the metallic shielding layer of a power unit provided in the submarine cable. The present invention may provide a submarine cable comprising at least one power unit, wherein the power unit includes: a conductor; an inner semiconductive layer surrounding the conductor; an insulating layer surrounding the inner semiconductive layer; an outer semiconductive layer surrounding the outside of the insulating layer; and a metallic shielding layer provided on the outside of the outer semiconductive layer, the metallic shielding layer comprising: a plurality of shielding wires wound in a transverse helical direction while being spaced apart from the outside of the outer semiconductive layer; and a shielding member wound in a transverse direction around the outside of the plurality of shielding wires, the shielding member being a braided strap formed by braiding a plurality of metal strands and having a cross-sectional width greater than a cross-sectional thickness thereof.

Description

submarine cables

[0001] The present invention relates to a submarine cable. More specifically, the present invention relates to a submarine cable in which the structure and shape of the shielding wire and shielding member constituting the metal shielding layer are optimized to prevent damage to the metal shielding layer of a power unit provided in the submarine cable.

[0002] Recently, renewable energy systems that install wind turbines and other devices in the sea at a certain distance from land with sufficient wind power and supply the generated electricity by connecting it to onshore power facilities via power cables have been gaining attention.

[0003] In cases where the sea depth is shallow, wind turbines can be installed on top of a structure built on the seabed. However, in cases where the sea depth is deep, wind turbines can be installed in a floating manner.

[0004] Floating wind turbines and substations are supported by floating materials and float above the sea surface, and the floating materials can be connected to anchors installed on the seabed with support lines to restrict their movement.

[0005] In addition, wind turbines installed at sea or substations connecting the wind turbines and power facilities on land can be connected by submarine cables laid underwater.

[0006] Here, the section from the ground-based power facilities to the seabed near the offshore wind turbine is the section where the submarine cable is laid on the seabed, and since there is no movement of the cable while transmitting power after the cable is laid, this section is called the static section, and the submarine cable laid in this section is generally called a static submarine cable. On the other hand, the section from the seabed near the wind turbine to the floating wind turbine or substation is subject to a lot of cable movement due to ocean currents, waves, etc., so this section is called the dynamic section, and the submarine cable laid in this section is called a dynamic submarine cable.

[0007] Dynamic submarine cables installed in dynamic sections are subjected to long-term, repetitive bending loads due to movement or bending caused by ocean currents or waves. It is difficult to apply a lead-skin shield layer as a metal shield layer that cannot withstand such environments to dynamic submarine cables.

[0008] Therefore, instead of a sheath shield layer, a dynamic submarine cable forms a metal wire layer by spirally winding multiple metal wires spaced apart on top of a bedding layer, and the outer side is wound with a metal tape to conduct current throughout the metal wire layer, thereby forming a metal shield layer.

[0009] Here, the metal tape wound transversely on the outside of the metal wire layer may be made of, for example, a copper tape. In a metal shielding layer having such a structure, when the submarine cable is repeatedly bent or pulled, the metal wire and the metal tape strongly bind each other, causing a short circuit or twisting phenomenon in the metal wire or a break in the metal tape, which may result in a deterioration of the fault current conduction and shielding function of the metal shielding layer.

[0010] Therefore, there is a great demand for submarine cables equipped with a metal shielding layer that can provide excellent durability even in environments where continuous bending or bending occurs without being fixed underwater, while also stably providing passage and shielding functions for fault currents.

[0011] The present invention aims to provide a submarine cable in which the structure and shape of the shielding wire and shielding member constituting the metal shielding layer are optimized so as to prevent damage to the metal shielding layer of the power unit provided in the submarine cable.

[0012] In order to solve the above problem, the present invention provides a submarine cable including one or more power units, wherein the power units include a conductor, an inner semiconducting layer wrapping the conductor, an insulating layer wrapping the inner semiconducting layer, an outer semiconducting layer wrapping the outer side of the insulating layer, and a metal shielding layer provided on the outer side of the outer semiconducting layer, wherein the metal shielding layer includes a plurality of shielding wires spaced apart from each other and spirally wound on the outer side of the outer semiconducting layer, and a shielding member wound on the outer side of the plurality of shielding wires, and wherein the shielding member is a braided strap in which a plurality of metal wires are braided and a cross-sectional width is larger than a cross-sectional thickness.

[0013] Additionally, the shielding member may be wound transversely in the same helical direction as the shielding wire, but the transverse winding pitch of the shielding member may be smaller than the transverse winding pitch of the shielding wire.

[0014] Here, each shielding wire constituting the metal shielding layer may be a stranded wire in which a plurality of metal wires are stranded.

[0015] In addition, each shielding wire constituting the metal shielding layer may be a braided wire in which a plurality of metal wires are braided.

[0016] In addition, the submarine cable may further include: a plurality of power units; a plurality of shape fillers arranged between the power units to accommodate the power units in a spaced-apart manner and to form a circular cross-sectional shape of the submarine cable; at least one optical unit accommodated in at least one of the plurality of shape fillers and having an optical fiber; a bedding layer provided on the outside of the plurality of power units and the plurality of shape fillers; at least one armor layer provided by horizontally winding a plurality of armor wires arranged on the outside of the bedding layer; and an outermost layer provided on the outside of the armor layer.

[0017] According to the submarine cable according to the present invention, the shielding member constituting the metal shielding layer of the power unit is made of a braided strap in which a plurality of metal wires are braided and the width of the cross-section is larger than the thickness of the cross-section, thereby preventing damage to the metal shielding layer due to pressure or force applied when bending or bending the submarine cable.

[0018] In addition, according to the submarine cable according to the present invention, the shielding member and the shielding wire constituting the metal shielding layer of the power unit are wound transversely in the same spiral direction, but the transverse winding pitch of the shielding member is made smaller than the transverse winding pitch of the shielding wire, thereby minimizing damage to the shielding wire caused by the shielding member and enabling rapid current conduction when a fault current occurs.

[0019] In addition, according to the submarine cable according to the present invention, the shielding wire constituting the metal shielding layer of the power unit is configured as a stranded wire or a braided wire, thereby dispersing the pressure or force applied when bending or bending the submarine cable, thereby further minimizing damage to the metal shielding layer.

[0020] Figure 1 illustrates an example of the configuration of an offshore wind power generation system connected to a submarine cable according to the present invention.

[0021] Figure 2 shows a multi-stage stripped perspective view of a dynamic submarine cable for underwater installation among submarine cables according to the present invention.

[0022] Figure 3 shows a perspective view and a partially enlarged view of one embodiment of a power unit according to the present invention.

[0023] Figure 4 shows a perspective view and a partially enlarged view of another embodiment of a power unit according to the present invention.

[0024] Figure 5 shows a perspective view and a partially enlarged view of another embodiment of a power unit according to the present invention.

[0025] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosure is thorough and complete, and to sufficiently convey the spirit of the invention to those skilled in the art. Like reference numbers designate like elements throughout the specification.

[0026] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosure is thorough and complete, and to sufficiently convey the spirit of the invention to those skilled in the art. Like reference numbers designate like elements throughout the specification.

[0027] Figure 1 illustrates an example of the configuration of an offshore wind power generation system connected to a submarine cable according to the present invention.

[0028] The installation of wind turbines (WB) is increasing in remote areas of the sea where there is sufficient wind and a certain distance from land.

[0029] In order to achieve abundant and consistent wind speeds, wind turbines (WB) are often installed in relatively deep seas rather than coastal areas. In the case of wind turbines installed in shallow coastal areas, structures are erected on the seabed and installed on top of them. However, in deep seas, it is often impossible to install structures on the seabed. Therefore, wind turbines (WB) are installed in a floating manner, anchored (A) on the seabed, and moored by connecting the wind turbine (WB) with a fixed wire (R).

[0030] In addition, when an offshore wind power generator (wb) is configured as a standalone power generation complex, multiple wind power generators (wb) are installed to form a larger power generation complex, and the power generated by multiple wind power generators (wb) is combined and supplied to a power facility (ps) on land in a form that minimizes power loss through a substation (ts), etc.

[0031] In this case, the onshore power facility (ps) and the offshore substation facility (ts) can be connected through a submarine cable system (1000).

[0032] The submarine cable constituting the submarine cable system (1000) illustrated in Fig. 1 is connected to a power facility (ps) on land and laid on the seabed up to the vicinity of a substation facility on the seabed. However, in order to connect to a substation facility (ts) on the seabed near the substation facility, an underwater laying is required.

[0033] Here, the submarine cable (300) installed on the seabed is generally buried in the seabed or covered with a protective material, whereas the submarine cable (100) in the section from the seabed to the sea surface is exposed underwater and is affected by various external forces such as currents and waves. The installation of the submarine cable from the seabed to the sea surface is called underwater installation. In addition, the submarine cable can be connected to substation facilities installed above the sea surface, and the section above the sea surface can also be treated as an underwater installation section.

[0034] Accordingly, a submarine cable system (1000) for connecting a land-based power facility (ps) and a sea-based substation facility (ts) may be installed in some sections on the seabed (g) and in other sections underwater (w).

[0035] In the case of a submarine cable system (1000), it is desirable to configure cable protection layers differently for sections installed on the seabed (g) and sections installed underwater (w) due to differences in their respective environments. The underwater (w) section is a section where the cable is continuously affected by waves or currents, and thus requires reinforcement of the cable protection layer compared to the cable installed on the seabed (g).

[0036] Depending on the differences in cable protection layers, the submarine cable system (1000) can be classified into a dynamic submarine cable (100) and a static submarine cable (300), and can have a structure in which different cable protection layers are connected at an intermediate connection (200).

[0037] The submarine cable below may mean a dynamic submarine cable (100).

[0038] Figure 2 illustrates a multi-stage stripped perspective view of a dynamic submarine cable for underwater installation according to the present invention.

[0039] A submarine cable (100) according to an embodiment of the present invention may include a cable core portion including one or more power units (10) for power transmission and a cable protection layer surrounding the outer side of the cable core portion. The cable core portion may include three power units (10), an optical unit (20), and a shape filler (30), and the cable protection layer may include a bedding layer (70), an armor layer (80), and an outermost layer (110). A detailed description of each component will be provided below.

[0040] In the embodiment of the present invention, a three-phase cable having three power units (10) is illustrated as an example, but the present invention is not limited thereto and can be applied to cases where one power unit (10) is provided or the number of power units (10) is different.

[0041] Each of the above power units (10) may be configured to include a conductor (11), an inner semiconducting layer (12), an insulating layer (13), an outer semiconducting layer (14), a metal shielding layer (15), and a polymer sheath (16).

[0042] The conductor (11) above serves as a passage through which current flows to transmit power, and may be made of a material having excellent conductivity and strength and flexibility suitable for cable manufacturing and use, such as copper or aluminum, to minimize power loss.

[0043] The conductor (11) above may be a bundle conductor formed by stranding a plurality of circular wires and gathering them into a circle, as illustrated in FIG. 2, and specifically, may be a bundle conductor formed by stranding a plurality of circular wires in an S direction or a Z direction, and further may be a flat conductor having an overall circular cross-section, including a flat wire layer formed by stranding a circular central wire and a flat wire to surround the circular central wire. In the case where the conductor is formed of the latter flat conductor, there is an advantage in that the outer diameter of the cable can be reduced because the space factor is relatively high compared to a circular compressed conductor.

[0044] However, the surface of the conductor (11) is not smooth, so the electric field may be uneven, and corona discharge may easily occur partially. In addition, if a gap is created between the surface of the conductor (11) and the insulating layer (13) described later, the insulating performance may be deteriorated.

[0045] In order to solve the above problem, an internal semiconducting layer (12) may be provided on the outside of the conductor (11). The internal semiconducting layer (12) may have semiconductivity by adding conductive particles such as carbon black, carbon nanotubes, carbon nanoplates, and graphite to an insulating material.

[0046] The above inner semiconducting layer (12) functions to stabilize the insulation performance by preventing a sudden change in electric field between the conductor (11) and the insulating layer (13) described below. In addition, it suppresses uneven charge distribution on the conductor surface to make the electric field uniform, and prevents the formation of a gap between the conductor (11) and the insulating layer (13), thereby suppressing corona discharge, insulation breakdown, etc.

[0047] The above insulating layer (13) is provided on the outside of the inner semiconducting layer (12) to electrically insulate the current flowing along the conductor (11) from the outside so that it does not leak to the outside. In general, the insulating layer (13) must have a high breakdown voltage and must be able to maintain its insulating performance stably for a long period of time. Furthermore, it must have a low dielectric loss and have heat resistance performance such as heat resistance. Therefore, the insulating layer (13) can use a polyolefin resin such as polyethylene and polypropylene, and the polyethylene resin can be made of a crosslinked paper.

[0048] An external semiconducting layer (14) may be provided on the outside of the insulating layer (13). The external semiconducting layer (14) is formed of a semiconducting material by adding conductive particles, such as carbon black, carbon nanotubes, carbon nanoplates, graphite, etc., to an insulating material like the internal semiconducting layer (12), thereby suppressing uneven charge distribution between the insulating layer (13) and a metal shielding layer (15) described below, thereby stabilizing the insulating performance. In addition, the external semiconducting layer (14) may perform the function of smoothing the surface of the insulating layer (13) in the cable, alleviating electric field concentration, preventing corona discharge, and physically protecting the insulating layer (13).

[0049] A metal shielding layer (15) and a polymer sheath (16) may be provided on the outside of the external semiconducting layer (14). The metal shielding layer (15) and the polymer sheath (16) can protect the power unit (10) from various environmental factors such as moisture penetration, mechanical trauma, and corrosion that may affect the power transmission performance of the cable.

[0050] The above metal shielding layer (15) not only protects the power unit (10) from external impact, but also acts as a passage for the fault current to flow in the event of an accident such as a ground fault or short circuit by being grounded at the end of the power unit (10), thereby shielding the electric field from being discharged to the outside of the power unit (10).

[0051] Typically, a lead sheath is used as the metal shielding layer (15), or a shielding wire (151) and a metal tape (not shown) can be used. In the case of a submarine cable (300) laid in a static section installed on the seabed as shown in FIG. 1, a lead sheath can be used as the metal shielding layer (15). However, in the case of a dynamic submarine cable (100), there is a concern that the lead sheath may be subject to fatigue failure due to cable behavior. Therefore, a plurality of shielding wires (151) made of a material such as copper may be wound horizontally, and a shielding member (153) wound horizontally across the shielding wires (151) may be applied as the metal shielding layer (15).

[0052] On the outside of the above metal shielding layer (15), a polymer sheath (16) composed of a resin such as polyvinyl chloride (PVC), polyethylene, etc. is extruded to improve the corrosion resistance and water resistance of the submarine cable, and to protect the cable from mechanical trauma and other external environmental factors such as heat and ultraviolet rays. In particular, in the case of submarine cables, it is preferable to use a polyethylene resin with excellent water resistance.

[0053] In addition, the power unit (10) may additionally be provided with a copper wire direct insertion tape (not shown) or a moisture absorption layer (not shown) between the metal shielding layer (15) and the external semiconducting layer (14). In addition, a moisture absorption layer (not shown) may additionally be provided between the metal shielding layer (15) and the polymer sheath (16).

[0054] The above copper wire direct tape (not shown) is composed of copper wire and non-woven tape, etc., and can function to facilitate electrical contact between the external semiconducting layer (14) and the metal shielding layer (15).

[0055] The above moisture-absorbing layer (not shown) may be formed in the form of a powder, tape, coating layer, or film containing a super absorbent polymer (SAP) that rapidly absorbs moisture that has penetrated the cable and has excellent ability to maintain an absorbed state. Accordingly, the moisture-absorbing layer can prevent moisture from penetrating in the longitudinal direction of the cable. In addition, the moisture-absorbing layer may be configured to include a copper wire to prevent a rapid change in the electric field in the moisture-absorbing layer.

[0056] In particular, when applying a shielding wire (151) and a metal tape (not shown) as a metal shielding layer (15) laid in the dynamic section of Fig. 1, the water-proofing performance is lower than that of a soft skin sheath, so it is desirable to additionally provide a moisture-absorbing layer (not shown) to improve the water-proofing performance.

[0057] Meanwhile, the submarine cable (100) may further include an optical unit (20). Here, the optical unit (20) may include at least one optical fiber (21) and a tube (22) that accommodates the optical fiber (21).

[0058] Each of the above optical units (20) is equipped with a predetermined number of optical fibers (21) mounted together with fillers (not shown) within a tube (22), and the tube (22) may be made of a rigid material such as stainless steel. In addition, the optical unit (20) may further be equipped with a metal sheath (23) and a polymer sheath (24) that surround the tube (22).

[0059] As illustrated in FIG. 2, a submarine cable (100) according to the present invention may include a plurality of shape fillers (30) arranged between a plurality of power units (10a, 10b, 10c) to accommodate the power units (10a, 10b, 10c) while being spaced apart from each other, and to form a cross-sectional shape of the cable into an overall circular shape.

[0060] Each shape filler (30) is provided with two concave portions on its inner surface, and a power unit (10) can be accommodated between the concave portion provided in one shape filler (30) and the concave portion provided in an adjacent shape filler (30). In addition, a flat portion can be provided between the two concave portions provided on the inner surface of each shape filler (30) to accommodate a plurality of power units (10a, 10b, 10c) in a mutually spaced state. The plurality of shape fillers (30) can form an overall circular cross-sectional shape of the cable by filling the space between the outer surfaces of the plurality of power units (10a, 10b, 10c). In addition, the shape filler (30) can accommodate an optical unit (20) in an optical unit accommodation portion formed therein. The shape filler (30) may be provided with a cut line in which a flat portion provided between two concave portions is partially cut inward, and an optical unit receiving portion for receiving an optical unit (20) may be provided at the end of the cut line.

[0061] And, as shown in FIG. 2, a binding tape layer (60) may be further provided to keep the cable core portion including a plurality of power units (10a, 10b, 10c), a plurality of shape fillers (30) and an optical unit (20) in a circular shape.

[0062] Meanwhile, the submarine cable (100) illustrated in FIG. 2 may be provided with a cable protection layer to protect internal components even in harsh environments such as seawater and salt in the ocean.

[0063] The cable protection layer of the submarine cable (100) illustrated in Fig. 2 may include a bedding layer (70) provided on the outside of the power unit (10) and a plurality of shape fillers (30). The bedding layer (70) may serve as a cushion for arranging an armor layer (80) provided with at least one armor wire.

[0064] The above bedding layer (70) may be provided with two armor layers (80a, 80b) on the outside to improve the mechanical strength of the submarine cable (100) in a harsh underwater environment, and a sheath layer of polymer resin material that serves as the outermost layer (110) may be provided on the outside of the armor layers (80a, 80b) to perform the role of a cable jacket.

[0065] For example, the outermost layer (110) is made of a polymer resin such as polyvinyl chloride (PVC) or polyethylene by extrusion, thereby protecting the armor layer and minimizing damage to the cable caused by waves and currents in a rough underwater environment, thereby ensuring sufficient durability.

[0066] The above armor layer (80a, 80b) can be configured by spirally winding a plurality of armor wires parallel to the outside of the bedding layer (70), and not only performs the function of reinforcing the mechanical properties and performance of the submarine cable (100), but also additionally protects the submarine cable (100) from external force.

[0067] It is preferable that the armor wire constituting the above armor layer (80) is composed of a metal material, but it may also be composed of a non-metal material as long as it has high tensile strength.

[0068] In the case of armor wire made of metal, it can be formed by horizontally winding wires made of steel, galvanized steel, copper, brass, bronze, etc. and having a cross-sectional shape such as circular or flat. In the case of non-metal armor wire, it can be formed by horizontally winding materials such as aramid fiber or ultra-high molecular weight polyethylene fiber, which are high-tensile materials.

[0069] In the following, the embodiments of the present invention are described as using a metal armor layer formed of metal armor wire, but the present invention is not limited thereto.

[0070] The armor wire constituting the metal armor layer (80) may be spirally wound around the outer surface of the bedding layer (70), and preferably, may be wound in the Z direction or S direction, which is opposite to the collective twisting direction of the power units (10a, 10b, 10c).

[0071] And, as shown in Fig. 2, in the case of a submarine cable (100) installed in a dynamic section, if the armor layer (80) is provided in multiple layers to reinforce rigidity, the transverse winding directions may be different from each other.

[0072] Typically, submarine cables laid in static sections may have a single armor layer and a serving layer (110) as the outermost layer outside the armor layer. However, in the case of submarine cables (100) laid in dynamic sections, a sheath layer of polymer resin material that serves as a cable jacket is provided as the outermost layer (110), as described above.

[0073] The submarine cable (100) configured in this manner has a stronger cable protection layer than a static submarine cable because continuous bending or bending occurs.

[0074] In the process of continuous bending or bending of the submarine cable during underwater installation, the cable protection layer exerts strong pressure on the inside, which can easily damage the metal shielding layer (15) of each power unit (10).

[0075] That is, the reinforced cable protection layer of the submarine cable (100) can strongly press the power unit (10) when bending or bending occurs, and as a result, the shielding wire (151) or shielding member (153) constituting the metal shielding layer (15) of the power unit (10) can be damaged.

[0076] Accordingly, the present invention has changed the structure and shape of the metal shielding layer (15) of the power unit (10) so as to prevent damage to the metal shielding layer (15) of the power unit (10) due to the armor layer of the submarine cable, etc., even when bending and bending of the dynamic submarine cable occur. This will be described with reference to FIG. 3 and below.

[0077] Figure 3 shows a perspective view and a partially enlarged view of one embodiment of a power unit (10) according to the present invention.

[0078] The power unit (10) according to the present invention may be configured to include, as described above, a conductor (11), an inner semiconducting layer (12) surrounding the conductor, an insulating layer (13) surrounding the inner semiconducting layer (12), an outer semiconducting layer (14) surrounding the outer side of the insulating layer (13), and a metal shielding layer (15) provided on the outer side of the outer semiconducting layer (14).

[0079] In addition, considering the special nature of the underwater installation environment, the power unit (10) according to the present invention may be equipped with a plurality of shielding wires (151a) that are spirally spaced apart and transversely wound on the outside of the outer semiconducting layer (14) without applying a metal shielding layer (15) in the form of a soft skin sheath, and a shielding member (153) that is transversely wound on the outside of the plurality of shielding wires (151a).

[0080] In addition, the shielding member (153) constituting the metal shielding layer (15) of the power unit (10) according to the present invention illustrated in FIG. 3 may be a braided strap in which a plurality of metal wires are braided and the width of the cross-section is larger than the thickness of the cross-section. The metal wire may refer to a thin wire, a small wire, etc. made of a metal material such as copper or a copper alloy, and the same applies hereinafter.

[0081] The metal tape applied as a conventional shielding member (153) has the advantage of being thin and closely adhered to the shielding wire (151a), but when a bending or bending situation of the submarine cable (100) occurs, the metal tape adhered to the shielding wire (151a) may be torn by the lifting of the shielding wire (151a), and the pressure or force due to the bending or bending may be transmitted to the shielding wire (151a) restrained by the metal tape, so that the shielding wire (151a) may be maintained in a twisted state, resulting in damage such as a kink or a short circuit that cannot be restored. That is, when using a metal tape as a shielding member (153) as in the past, the metal tape or the shielding wire (151a) may be damaged.

[0082] On the other hand, according to the present embodiment, the shielding member (153) constituting the metal shielding layer (15) is formed as a braided strap in which a plurality of metal wires are braided and the width of the cross-section is larger than the thickness of the cross-section, thereby preventing damage or disconnection of the shielding wire (151a) even in the case of bending or bending of the submarine cable (100). The braided strap, which is the shielding member (153), may be formed of a material such as copper or a copper alloy, and the shielding wire (151a) may also be formed of a material such as copper or a copper alloy.

[0083] Specifically, when the shielding member (153) is a braided strap, the braided structure itself has elasticity, which increases the tensile range, so that when the submarine cable is bent or stretched, the braided strap stretches, reducing the binding force on the shielding wire (151a), thereby preventing damage to the metal shielding layer (15) due to pressure or force that may be applied to the shielding wire (151a).

[0084] In addition, when using a braided strap as a shielding member (153), even if some of the metal wires constituting the braided strap are broken, the overall electrical conductivity can be maintained. That is, since the braided strap is provided by braiding multiple metal wires, even if some of the metal wires are broken, the electrical conductivity can be maintained as long as the braided structure itself is not damaged.

[0085] In addition, the braided strap, which is the shielding member (153), may be a braided strap having a cross-sectional width greater than the cross-sectional thickness. The cross-sectional thickness of the braided strap may be preset in consideration of damage prevention and the outer diameter of the submarine cable, and the cross-sectional width of the braided strap may be formed to be greater than the cross-sectional thickness. When the cross-sectional width of the braided strap is formed to be greater than the cross-sectional thickness, the contact area between the braided strap and the shielding wire (151a) increases, thereby further reducing the binding force on the shielding wire (151a) and enabling rapid current conduction when a fault current occurs.

[0086] Meanwhile, the thickness of each of the braided straps constituting the metal shielding layer (15) may be 1 to 2 mm, preferably 1.5 to 2 mm. Here, if the thickness of the braided strap is less than 1 mm, the durability of the metal shielding layer (15) is reduced, so that the submarine cable may be easily damaged when bent or stretched, and the passage function of the fault current may be insufficiently performed due to an increase in the overall resistance, whereas if the thickness of the braided strap exceeds 2 mm, the thickness of the braided strap is unnecessarily thick, so that the outer diameter and weight of the submarine cable are unnecessarily increased, and the manufacturing cost of the submarine cable is increased due to an increase in the metal wire forming the braided strap.

[0087] In addition, the shielding member (153) constituting the metal shielding layer (15) of the power unit (10) of the present invention may be wound transversely in the same spiral direction (SS direction or ZZ direction) as the shielding wire (151a), but the transverse winding pitch of the shielding member (153) may be provided to be smaller than the transverse winding pitch of the shielding wire (151a). The transverse winding pitch of the shielding wire (151a) may be a length for the shielding wire (151a) to complete one turn outside the outer semiconducting layer (14), and the transverse winding pitch of the shielding member (153) may mean a length for the shielding member (153) to complete one turn outside the shielding wire (151a).

[0088] Specifically, as illustrated in FIG. 3, the metal shielding layer (15) of the power unit (10) of the present invention has a plurality of shielding wires (151a) made of a metal material such as copper or a copper alloy, which are spaced apart from each other and spirally wound on the outside of the outer semiconducting layer (14), and a shielding member (153) provided on the outside of the plurality of shielding wires (151a) can be spirally wound in the same spiral direction as the horizontal winding direction of the shielding wires (151a). That is, the horizontal winding directions of the shielding wires (151a) and the shielding member (153) can be provided in the same SS direction or ZZ direction. When the shielding wire (151a) and the shielding member (153) are transversely wound in the same direction, the restraining force of the shielding wire (151a) by the shielding member (153) is reduced compared to when they are transversely wound in the opposite direction (SZ direction or ZS direction), thereby minimizing damage to the shielding wire (151a) due to pressure or force applied when bending or bending the submarine cable.

[0089] In addition, the transverse pitch of the shielding member (153) may be provided to be smaller than the transverse pitch of the shielding wire (151a). The shielding member (153) is configured to quickly conduct a fault current that may flow through one shielding wire (151a) when a fault current occurs in a submarine cable to a plurality of shielding wires (151a) that are spaced apart from each other.

[0090] If the transverse winding pitch of the shielding member (153) is provided relatively larger than the transverse winding pitch of the shielding wire (151a), the shielding member (153) may compress the shielding wire (151a) more quickly when the submarine cable is bent or curved, which may cause the shielding wire (151a) to be broken or snapped. On the other hand, if the transverse winding pitch of the shielding member (153) is provided relatively smaller than the transverse winding pitch of the shielding wire (151a) as in the present embodiments, the tensile allowable range of the braided strap is increased within a range where plastic deformation does not occur when the submarine cable is bent or curved, so that the pressure on the shielding wire (151a) by the shielding member (153) is minimized, thereby preventing the shielding wire (151a) from being broken or snapped.

[0091] In addition, when the transverse pitch of the shielding member (153) is provided to be larger than the transverse pitch of the shielding wire (151a), the length of the contact point between one shielding wire (151a) and the adjacent wire (151a) is increased by the shielding member (153), so that the speed at which the fault current flows through the multiple shielding wires is slowed down, which may generate high-temperature heat. On the other hand, when the transverse pitch of the shielding member (153) is provided to be smaller than the transverse pitch of the shielding wire (151a), as in the present embodiments, the length of the contact point between one shielding wire (151a) and the adjacent wire (151a) is shortened by the shielding member (153), so that the speed at which the fault current flows through the multiple shielding wires is fast, which may prevent the generation of high-temperature heat.

[0092] In addition, when the transverse winding pitch of the shielding member (153) is provided to be larger than the transverse winding pitch of the shielding wire (151a), the space between the plurality of shielding wires (151a) provided between the transverse winding pitches of the shielding member (153) becomes wider, so that when bending or bending of the submarine cable occurs, the arrangement of the plurality of shielding wires (151a) may become misaligned, causing a phenomenon of crowding in a certain direction. On the other hand, when the transverse winding pitch of the shielding member (153) is provided to be smaller than the transverse winding pitch of the shielding wire (151a) as in the present embodiments, the space between the plurality of shielding wires (151a) provided between the transverse winding pitches of the shielding member (153) becomes narrow, so that when bending or bending of the submarine cable occurs, the phenomenon of crowding due to the arrangement of the plurality of shielding wires (151a) becoming misaligned can be prevented.

[0093] In addition, if the transverse pitch of the shielding member (153) is provided to be smaller than the transverse pitch of the shielding wire (151a), even if some of the shielding wires (151a) are disconnected, the fault current of the disconnected shielding wire (151a) can be quickly transferred to another adjacent shielding wire (151a).

[0094] Accordingly, according to the submarine cable (100) according to the present invention, the shielding member (153) and the shielding wire (151a) constituting the metal shielding layer (15) of the power unit (10) are wound transversely in the same spiral direction, but the transverse winding pitch of the shielding member (153) is made smaller than the transverse winding pitch of the shielding wire (151a), thereby minimizing damage to the shielding wire (151a) caused by the shielding member (153) and enabling rapid current conduction when a fault current occurs.

[0095] FIG. 4 shows a perspective view and a partially enlarged view of another embodiment of a power unit (10) according to the present invention, and FIG. 5 shows a perspective view and a partially enlarged view of another embodiment of a power unit (10) according to the present invention.

[0096] Furthermore, in order to prevent damage to the metal shielding layer (15) of the power unit (10), as illustrated in FIG. 4, each shielding wire (151b) constituting the metal shielding layer (15) may be a stranded wire in which a plurality of metal wires are stranded, or as illustrated in FIG. 5, each shielding wire (151c) constituting the metal shielding layer (15) may be a braided wire in which a plurality of metal wires are braided. The stranded wire or the braided wire may be formed of a plurality of wires made of copper or a copper alloy.

[0097] Since each shielding wire (151a) constituting the metal shielding layer (15) of the power unit (10) illustrated in FIG. 3 is provided as a single solid wire, when the braided strap, which is the shielding member (153), applies force or pressure to the shielding wire (151a) due to bending or bending of the submarine cable, the force or pressure cannot be distributed, so that damage may occur to the shielding wire (151a), or conversely, the shielding member (153) may be damaged by applying strong pressure, thereby causing damage to the shielding member (153). Thus, the metal shielding layer (15) may be damaged.

[0098] Accordingly, the present invention configures the shielding member (153) as a braided strap, and at the same time, configures the shielding wire (151b) as a stranded wire made of a plurality of metal wires, or configures the shielding wire (151c) as a braided wire made of a plurality of metal wires, so that when the braided strap, which is the shielding member (153), applies force or pressure to the shielding wire (151a) due to bending or bending of the submarine cable, the force or pressure can be dispersed.

[0099] Specifically, as shown in FIG. 4, when the shielding member (153) is configured as a braided strap and the shielding wire (151b) is configured as a stranded wire in which multiple metal wires are twisted, when the braided strap, which is the shielding member (153) that is stretched due to bending or bending of the submarine cable (100), applies force or pressure to the stranded wire, which is the shielding wire (151b), the multiple metal wires constituting the stranded wire can be untwisted in the opposite direction to which they were twisted, thereby dispersing the force or pressure.

[0100] As a shielding wire (151b), a stranded wire may be provided by stranding multiple wires. The stranded wire may not be provided with a central metal wire and may be configured by twisting multiple peripheral metal wires, but is not limited thereto. For example, the stranded wire may be provided with one central metal wire and six peripheral metal wires may be twisted around the central metal wire in the same direction. If the stranded wire does not have a central metal wire, when the stranded wire is unwound in the opposite direction to which it is twisted, the multiple unwound metal wires may damage the outer semiconducting layer. On the other hand, if the stranded wire is provided with a central metal wire, when the stranded wire is unwound in the opposite direction to which it is twisted, damage that may be inflicted to the power unit (10) due to the peripheral metal wires unwound around the central metal wire can be prevented. Therefore, preferably, the stranded wire as a shielding wire (151b) may be provided with a central metal wire and may be configured by twisting multiple peripheral metal wires.

[0101] When the braided strap, which is a shielding member (153) that is stretched due to bending or bending of the submarine cable, applies force or pressure to the shielding wire (151b), the plurality of metal wires constituting the twisted wire may be unwound in the opposite direction to the twisting, and when the force or pressure applied to the shielding wire (151b) is very large, the plurality of metal wires may be unwound and arranged in a row. In other words, the degree of unwound may vary depending on the magnitude of the force or pressure applied to the shielding wire (151b) by the braided strap, which is the shielding member (153).

[0102] When a plurality of metal wires constituting the stranded wire are unwound in the opposite direction to which they were twisted, the stranded wire can be maintained in a loosened state even when the bending or bending of the submarine cable (100) is reduced or the submarine cable (100) is returned to its original straight shape.

[0103] If the stranded wire, which is the shielding wire (151b), remains loose, the braided strap, which is the shielding member (153) provided on the loosened stranded wire, can come into contact with the loosened stranded wire in a loosened state. That is, the braided strap provided on the loosened stranded wire becomes loose, and thus the tensile range becomes larger, so that the pressure or force applied when bending or bending the submarine cable (100) can be further dispersed.

[0104] Meanwhile, in the case where the shielding member (153) is configured as a braided strap as shown in FIG. 5 and the shielding wire (151c) is configured as a braided wire in which a plurality of metal wires are braided, not only the braided strap, which is the shielding member (153), but also the braided wire, which is the shielding wire (151c), is elastic and can be stretched when bending or bending of the submarine cable occurs, and when the braided strap, which is the shielding member (153), applies force or pressure to the braided wire, which is the shielding wire (151c), the braided wire in contact with the braided strap can be widened to disperse the force or pressure.

[0105] The braided wire, which is the shielding wire (151c), may be provided by braiding multiple wires. The braided wire may be circular in shape, but is not limited thereto. For example, the braided wire may be strap-shaped, similar to the braided strap, which is the shielding member (153). In other words, the braided wire is not limited in shape as long as it is braided with multiple wires.

[0106] In addition, the width of the braided wire, which is the shielding wire (151c), may be provided to be smaller than the width of the braided strap, which is the shielding member (153). However, this is not limited thereto, and the width of the braided wire may be provided to be equal to or larger than the width of the braided strap, which is the shielding member (153). That is, the width of the braided wire, which is the shielding wire (151c), may vary depending on the cable design conditions.

[0107] Accordingly, as in the present invention, when the shielding member (153) is configured as a braided strap and the shielding wire (151b) constituting the metal shielding layer (151) is configured as a stranded wire made of a plurality of metal wires, or when the shielding wire (151c) is configured as a braided wire made of a plurality of metal wires, the pressure or force applied when bending or bending the submarine cable can be dispersed, thereby further minimizing damage to the metal shielding layer.

[0108] While this specification has described preferred embodiments of the present invention, those skilled in the art will appreciate that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention as defined in the claims below. Therefore, any modified implementation that fundamentally includes the elements of the claims should be considered within the technical scope of the present invention.

Claims

1. In a submarine cable including one or more power units, The above power unit includes a conductor, an inner semiconducting layer surrounding the conductor, an insulating layer surrounding the inner semiconducting layer, an outer semiconducting layer surrounding the outer side of the insulating layer, and a metal shielding layer provided on the outer side of the outer semiconducting layer. The above metal shielding layer includes a plurality of shielding wires spaced apart and spirally wound outside the outer semiconducting layer and a shielding member wound outside the plurality of shielding wires. A submarine cable characterized in that the above shielding member is a braided strap in which a plurality of metal wires are braided and the width of the cross-section is larger than the thickness of the cross-section.

2. In paragraph 1, A submarine cable characterized in that the shielding member is wound transversely in the same helical direction as the shielding wire, but the transverse winding pitch of the shielding member is smaller than the transverse winding pitch of the shielding wire.

3. In paragraph 1, A submarine cable, characterized in that each shielding wire constituting the above metal shielding layer is a stranded wire in which a plurality of metal wires are stranded.

4. In paragraph 1, A submarine cable, characterized in that each shielding wire constituting the metal shielding layer is a braided wire in which a plurality of metal wires are braided.

5. In paragraph 1, The above submarine cable, A plurality of said power units; A plurality of shape fillers arranged between the above power units to accommodate the above power units in a mutually spaced state and to form a circular cross-sectional shape of the submarine cable; At least one optical unit, which is accommodated in at least one of a plurality of shape fillers and has an optical fiber; A bedding layer provided on the outer side of the plurality of power units and the plurality of shape fillers; At least one armor layer comprising a plurality of armor wires wound transversely and arranged on the outside of the bedding layer; and A submarine cable additionally comprising an outermost layer provided outside the above armor layer.

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