Power unit and submarine cable including same

Abstract

The present invention relates to a power unit and a submarine cable including same, which prevents separation of a bonding portion of a metal shielding layer of a power unit included in a submarine cable when the metal shielding layer is bonded in a "dry type" configuration to completely cover an insulation layer inside the power unit, the separation being caused by stress and tensile loads generated during bending of the submarine cable, and thus the present invention ensures excellent water-blocking performance, shielding performance, and durability.

Description

Power unit and submarine cable including the same

[0001] The present invention relates to a power unit and a submarine cable including the same, wherein the metal shielding layer of the power unit included in the submarine cable is configured in a 'Dry Type' form so as to completely cover the insulation layer inside the power unit, thereby preventing the separation of the joint of the metal shielding layer due to stress and tensile load generated during bending of the submarine cable, and ensuring excellent water-blocking performance, shielding performance, and durability.

[0002] Recently, submarine cables are being widely used to supply power and connect optical communications to island areas located a certain distance from the mainland.

[0003] Since submarine cables are directly exposed to the seabed environment, water-blocking performance is essential to prevent moisture from penetrating or spreading into the cable. Among submarine cables, so-called 'Dry Type' cables can be configured to block moisture penetration by being equipped with a metal shielding layer made of lead sheathing.

[0004] A metal shielding layer equipped with a water-blocking function is configured to completely cover the insulation layer inside the power unit, thereby preventing the water tree phenomenon that may occur when the insulation layer is exposed to water for a long period of time.

[0005] These metal shielding layers can be manufactured in the form of seamless tubes using continuous or discontinuous extrusion methods, in which case lead (Pb) or a lead alloy providing high ductility and extrudability can be used as the metal shielding layer material.

[0006] However, while lead-based metal shielding layers have the advantages of being easy to manufacture and flexible, their low fatigue resistance may make them unsuitable for dynamic submarine cables subjected to repetitive bending and tensile loading in dynamic environments. To address this, methods are being proposed to manufacture metal shielding layers using copper (Cu) or copper alloys, which possess excellent mechanical properties and durability.

[0007] Meanwhile, since copper (Cu) has a higher melting point than lead (Pb), if a metal shielding layer is formed on the outside of the insulating layer by extrusion, the insulating layer may be thermally damaged. Therefore, a copper metal shielding layer can be manufactured by wrapping a metal sheet in a circular shape on the outside of the insulating layer and then joining the ends.

[0008] However, if the bonding strength at the joints of a metal shielding layer manufactured by a bonding method is insufficient, there is a risk that the joints may detach and separate due to the high stress and tensile loads generated during the bending of the submarine cable. This allows moisture to easily penetrate into the metal shielding layer, degrading the waterproofing performance of the submarine cable and reducing its shielding performance. Furthermore, it weakens the structural stability of the power unit, making it vulnerable to damage from the external environment.

[0009] Therefore, there is a need for a power unit of a submarine cable that can secure excellent water-blocking performance, shielding performance, and durability by ensuring that the joint of the metal shielding layer does not easily separate from the stress and tensile load generated during bending of the submarine cable, even when joining the metal shielding layer of a 'Dry Type' submarine cable configured to completely cover the insulation layer inside the power unit.

[0010] The present invention aims to solve the problem of providing a power unit and a submarine cable including the same, which can secure excellent water-blocking performance, shielding performance, and durability by preventing the separation of the joints of the metal shielding layer due to stress and tensile load generated during bending of the submarine cable when the metal shielding layer of the power unit included in the submarine cable is configured in a 'Dry Type' form such that it completely covers the insulation layer inside the power unit.

[0011] To solve the above problem, the present invention may provide a power unit comprising at least one power unit included in a submarine cable, the power unit comprising a conductor, an inner semiconducting layer surrounding the conductor, an insulating layer surrounding the inner semiconducting layer, an outer semiconducting layer surrounding the insulating layer, a metal shielding layer surrounding the outer semiconducting layer, and a polymer sheath layer surrounding the metal shielding layer, wherein the metal shielding layer comprises a joint in which both ends of a metal sheet are joined in a mutually overlapping state, and the joint comprises at least one recess and a protrusion that are mutually fitted to each of the joint surfaces between the two ends of the metal sheet.

[0012] In addition, the metal shielding layer may not be wrinkled.

[0013] In this case, the thickness of the metal sheet may be 0.1 millimeters to 2.0 millimeters (mm), and the thickness of the joint may be 0.12 millimeters to 3.60 millimeters (mm).

[0014] In addition, the bonding length of the bonding surface in the circumferential cross-section of the above-mentioned joint may be 1 millimeter to 5 millimeters (mm).

[0015] In addition, the metal sheet constituting the metal shielding layer may be made of copper or a copper alloy.

[0016] In addition, the recess and protrusion formed on the joint surface of the above joint may extend along the longitudinal direction of the power unit.

[0017] In addition, the recesses and protrusions formed on the joint surface of the above joint may each be provided in multiple numbers.

[0018] Here, multiple lumens and iron parts may be provided extending parallel along the longitudinal direction of the power unit.

[0019] In addition, the above joint may be formed by applying an adhesive made of a conductive resin composition to the joint surface.

[0020] In addition, the above-mentioned lumbar and iron parts may be formed on the upper surface of one end and the lower surface of the other end, respectively, of the metal sheet.

[0021] In addition, the main part of the above joint can be formed by cutting a smooth metal sheet to a preset width and simultaneously press-forming both ends of the metal sheet.

[0022] In addition, to solve the above problem, the present invention may provide a power unit characterized by further comprising: a plurality of the aforementioned power units; a plurality of cable intermediaries provided in the region between the plurality of power units; a binding taping layer for finishing the plurality of power units and the plurality of cable intermediaries in a circular shape; a bedding layer provided on the outer side of the binding taping layer; an armor layer provided on the outer side of the bedding layer; and an outermost layer provided on the outer side of the armor layer and comprising a polymer resin material.

[0023] According to the power unit and submarine cable including the same according to the present invention, at least one recess and a protrusion having a mutually fitting shape are formed on each of the joint surfaces of a joint formed by overlapping and joining the two ends of a metal sheet constituting the metal shielding layer of the power unit, so that the uneven structure formed in the joint acts like a latch and simultaneously increases the joint area, thereby preventing the separation phenomenon of the joint of the metal shielding layer and further enhancing water barrier performance, shielding performance, and durability.

[0024] In addition, according to the power unit and submarine cable including the same of the present invention, the metal sheet constituting the metal shielding layer of the power unit is composed of copper or a copper alloy material having excellent mechanical properties and high fatigue resistance, thereby enabling excellent durability against tensile force or load generated during long-term repetitive bending even in the dynamic environment where the submarine cable is laid.

[0025] FIG. 1 illustrates a cross-sectional view of one embodiment of a submarine cable according to the present invention.

[0026] FIG. 2 shows a multi-stage stripping view and a partial enlarged view of a power unit included in the submarine cable shown in FIG. 1.

[0027] FIGS. 3 and 4 illustrate cross-sectional views of embodiments in the joint region of a metal shielding layer provided in a submarine cable according to the present invention.

[0028] Figure 5 shows a perspective view of a metal sheet forming a metal shielding layer as illustrated in Figure 4.

[0029] 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 disclosed content is thorough and complete, and to ensure that the spirit of the invention is sufficiently conveyed to those skilled in the art. Throughout the specification, the same reference numerals indicate the same components.

[0030] FIG. 1 illustrates a cross-sectional view of one embodiment of a submarine cable according to the present invention.

[0031] As illustrated in FIG. 1, the submarine cable (1000) according to the present invention may be composed of a three-phase power cable in which three power units (300a, 300b, 300c) are arranged in a triangular shape.

[0032] In a three-phase power cable, a plurality of cable inserts (400a, 400b, 400c) made of plastic material may be provided and positioned in the area between adjacent power units. The plurality of cable inserts (400a, 400b, 400c) fill the empty space between the power units (300a, 300b, 300c) to form the entire submarine cable in a circular shape, thereby serving to maintain the roundness of the cable.

[0033] One or more of the above plurality of cable inserts (400a, 400b, 400c) may be provided with an optical unit receiving portion (a) in which an optical unit (100) can be received and mounted.

[0034] The optical unit (100) may include at least one optical fiber (110) and a tube (120) having the optical fiber (110). The optical unit (100) has a predetermined number of optical fibers (110) mounted together with a filler inside the tube (120). Additionally, the optical unit (100) may further have a sheath (130) that surrounds the tube (120).

[0035] The plurality of power units (300a, 300b, 300c), the optical unit (100), and the plurality of cable inserts (400a, 400b, 400c) can be combined in a circular arrangement with a predetermined pitch to form a submarine cable (1000).

[0036] In addition, a binding tape layer (500) for fixing the plurality of power units (300a, 300b, 300c) and the plurality of cable inserts (400a, 400b, 400c) in a circular shape may be additionally provided.

[0037] A bedding layer (600) may be formed on the outer side of the binding tape layer (500). The bedding layer (600) serves to provide a mounting surface so that an armor layer (700) located on the outer side can be stably mounted.

[0038] The above armor layer (700) includes a plurality of armor wires (710) and may be composed of a multilayer structure including a first armor wire layer (700a) and a second armor wire layer (700b), or may be a single layer structure equipped only with the first armor wire layer (700a). The above armor layer (700) performs the function of protecting the submarine cable (1000) from external shock and damage in a rough seabed environment.

[0039] On the outer side of the armor layer (700), an outermost layer (800), such as a serving layer or a jacket containing a polymer resin material, may be provided. The outermost layer (800) protects the armor layer (700) and at the same time mitigates external forces applied in an underwater environment, such as waves and currents, thereby minimizing damage to the submarine cable (1000) and providing high durability.

[0040] Although FIG. 1 illustrates that the power unit included in the submarine cable (1000) is provided with three units, it is not limited thereto, and the power unit included in the submarine cable (1000) may be provided with one unit. In this case, the submarine cable may include a bedding layer (600) provided on a polymer sheath layer (360) to be described later with reference to FIG. 2, an armor layer (700) provided on the bedding layer (600), and an outermost layer (800) provided on the armor layer (700).

[0041] In the process of transmitting power through a plurality of power units (300a, 300b, 300c) according to the present invention, if the submarine cable (1000) is exposed to the seabed environment for a long period, the insulation strength may be reduced and a water tree may be formed due to moisture penetration and diffusion into each power unit (300a, 300b, 300c). This water tree phenomenon may lead to the deterioration of the insulation layer and reduce the performance of the submarine cable.

[0042] For submarine cables of 220kV or higher, instead of using a metal shielding layer structure with multiple metal wires wound spirally and a metal tape wound over the multiple metal wires, it is suitable to use a metal sheet that completely wraps around the outer surface of the insulation layer. A metal shielding layer that completely wraps the insulation layer with a metal sheet can be manufactured mainly using either an extrusion method or a bonding method.

[0043] Metal shielding layers manufactured by the extrusion method utilize metal sheets made of lead or lead alloys. However, since lead metal sheets have low durability and are vulnerable to stress and tensile loads generated when submarine cables are subjected to bending in dynamic environments, metal shielding layers manufactured by the bonding method may use metal sheets made of copper or copper alloys. Copper and copper alloys provide excellent mechanical strength and fatigue resistance, enabling them to maintain stable performance over long periods even in the dynamic environments where submarine cables are installed.

[0044] The present invention relates to a submarine cable comprising a power unit in which a metal sheet made of copper is applied as a metal shielding layer. The submarine cable of the present invention effectively prevents moisture penetration by optimizing the bonding structure of the metal shielding layer, thereby maintaining insulation strength and providing excellent durability and reliability even in dynamic environments.

[0045] FIG. 2 shows a multi-stage stripping view and a partial enlarged view of a power unit included in the submarine cable shown in FIG. 1.

[0046] Referring to FIG. 2, the structure of the power unit (300) included in the submarine cable (1000) according to the present invention is examined in detail. The power unit (300) may sequentially include a conductor (310), an inner semiconducting layer (320), an insulating layer (330), an outer semiconducting layer (340), a metal shielding layer (350), and a polymer sheath layer (360). Additionally, a coating layer (370) may be additionally included to enhance durability in a dynamic environment.

[0047] The conductor (310) serves as a passage for current to flow to transmit power and is made of a material, such as copper or aluminum, which has excellent conductivity and strength and flexibility suitable for cable manufacturing and use so as to minimize power loss.

[0048] The above conductor (310) may be a circular compressed conductor formed by twisting multiple circular wires together and compressing them into a circle, or it may be a flat conductor having a flat wire layer composed of a circular central wire and a flat wire surrounding it. A flat conductor has a relatively higher packing density compared to a circular compressed conductor, which allows the outer diameter of the submarine cable to be reduced.

[0049] However, if the surface of the conductor (310) is not smooth, the electric field becomes uneven and corona discharge may occur in some areas, and if a gap is formed between the surface of the conductor (310) and the insulating layer (330) described later, the electric field may be concentrated in the gap and the insulation performance may be degraded.

[0050] Accordingly, an internal semiconducting layer (320) may be provided on the outside of the conductor (310). The internal semiconducting layer (320) may be given semiconductivity by adding conductive particles, such as carbon black, carbon nanotubes, carbon nanoplates, and graphite, to an insulating resin.

[0051] The above-mentioned internal semiconducting layer (320) prevents a sudden change in electric field between the conductor (310) and the insulating layer (330) to stabilize insulation performance, maintains a uniform electric field by suppressing uneven charge distribution on the surface of the conductor (310), and prevents corona discharge and insulation breakdown by preventing the formation of voids.

[0052] The insulating layer (330) is positioned on the outside of the inner semiconducting layer (320) to electrically insulate the current flowing along the conductor (310) so that it does not leak to the outside. Generally, the insulating layer (330) must maintain a high breakdown voltage and provide stable insulation performance over a long period. In addition, low dielectric loss and thermal resistance performance, such as heat resistance, are required. To this end, the insulating layer (330) may be composed of a polyolefin resin such as polyethylene or polypropylene, and in particular, the polyethylene resin may be made of a cross-linked resin.

[0053] An outer semiconducting layer (340) may be provided on the outside of the insulating layer (330). The outer semiconducting layer (340) is formed from an insulating material with added conductive particles, similar to the inner semiconducting layer (320), and stabilizes the insulation performance by making the charge distribution between the insulating layer (330) and the metal shielding layer (350) uniform. In addition, the outer semiconducting layer (340) can smooth the surface of the insulating layer (330) to alleviate electric field concentration and prevent corona discharge, and can also perform the function of physically protecting the insulating layer (330).

[0054] A metal shielding layer (350) acting as a water-blocking layer may be provided on the outer side of the above-mentioned outer semiconducting layer (340). The metal shielding layer (350) is grounded at the end of the cable and serves as a passage through which fault current can flow in the event of an accident such as a ground fault or short circuit. It also basically performs the role of protecting the cable from external shocks and shielding it so that the electric field is not discharged outside the cable.

[0055] In addition, if the metal shielding layer (350) is configured in a 'Dry Type' form so as to completely cover the insulation layer (330) inside the power unit, it can also perform a moisture blocking function to prevent moisture from penetrating into the power unit (300) and forming a water tree within the insulation layer (330). The metal shielding layer (350) can be configured by wrapping a metal sheet (351) in a circular shape around the outer side of the outer semiconducting layer (16) and joining it. Specifically, a metal sheet can be wrapped around the outer side of the outer semiconducting layer (16), and a joint (350s) can be formed in which both ends of the metal sheet are joined in a mutually overlapping state.

[0056] The metal sheet (351) constituting the metal shielding layer (350) is made of a conductive material, such as copper, stainless steel, aluminum, etc., and preferably may be made of copper or a copper alloy. In particular, copper or a copper alloy has excellent mechanical properties and excellent fatigue resistance, providing excellent durability against tensile force or load generated during long-term repetitive bending in a dynamic environment.

[0057] Additionally, the metal shielding layer (350) may not be wrinkled. Specifically, the outer surface of the metal shielding layer (250) may have a smooth structure without a wrinkled corrugation structure. In this way, a metal sheet (351) with a smooth surface is wound around the outside of the insulating layer (330), and both ends of the metal sheet (351) are joined so that the outer diameter of the metal shielding layer (350) can be minimized.

[0058] The metal shielding layer (350) may include a joint (350s) in which the two ends (351a, 351b) of the metal sheet (351) are joined in an overlapping state. The joint (350s) may be formed by overlapping the two ends (351a, 351b) of the metal sheet (351) by a certain length and then applying an adhesive to the joint surface so that the two ends (351a, 351b) of the metal sheet (351) are joined. The adhesive may be applied to one of the two joint surfaces or to both of the two joint surfaces.

[0059] The adhesive applied to the bonding surface of the above-mentioned bonding portion (350s) may be composed of a conductive resin composition to provide excellent electrical contact between the two ends (351a, 351b) of the metal sheet (351). For example, the adhesive may be prepared as a conductive resin composition comprising a conductive filler such as carbon black, carbon nanotubes, carbon nanoplates, or graphite in an ethylene-vinyl acetate-based, polyolefin-based, styrene block copolymer-based, polyamide-based, polyester-based, or urethane-based polymer resin.

[0060] Additionally, the joint portion (350s) of the metal shielding layer (350) may include at least one recess (352) and a protrusion (353) having a shape that fits together on each of the joint surfaces between the two ends of the metal sheet (351). The protrusion (353) refers to an area protruding from the joint surface of the joint portion (350s), and the recess (352) refers to an area sunken from the joint surface of the joint portion (350s). The protrusion (353) and the recess (352) are provided on each of the joint surfaces between the two ends of the metal sheet (351) so that they fit together when joined. For example, the iron portion (353) provided at one end of the metal sheet (351) may be mutually fitted when joined with the recess (352) provided at the other end of the metal sheet (351), and the recess (352) provided at one end of the metal sheet (351) may be mutually fitted when joined with the iron portion (353) provided at the other end of the metal sheet (351).

[0061] The above-mentioned portion (353) may refer to a portion of the metal sheet (351) constituting the metal shielding layer (350) that has a reduced thickness through press processing, etc., and the above-mentioned portion (352) may refer to a portion that protrudes as a result of the formation of the above-mentioned portion (353).

[0062] That is, the metal shielding layer (350) of the present invention has two ends of a metal sheet (351) that overlap each other and are joined by an adhesive to form a joint (350s), and the joint (350s) has a recess (352) and a protrusion (353) formed on the joint surface, thereby improving the bonding strength of the metal shielding layer (350) through the mutually bonding structure of the joint surface. As a result, the phenomenon of the joints of the two ends (351a, 351b) of the metal sheet (351) separating can be prevented even when high stress and tensile load are applied when the submarine cable is bent or curved.

[0063] FIGS. 3 and 4 illustrate cross-sectional views of embodiments in the joint region of a metal shielding layer provided in a submarine cable according to the present invention.

[0064] FIG. 3 illustrates an example in which one concave part (352) and one protruding part (353) are formed on each joint surface of the joint part (350s), and FIG. 4 illustrates an example in which three concave parts (352) and three protruding parts (353) are formed on each joint surface of the joint part (350s).

[0065] Additionally, the recesses (352) and protrusions (353) formed in the joint portion (350s) may be arranged in various numbers in addition to the embodiments shown in FIG. 3 and FIG. 34, but preferably, the recesses (352) and protrusions (353) provided on the joint surface of the joint portion (350s) may each be formed within a range of 1 to 5.

[0066] As described above, the bonding portion (350s) of the metal shielding layer (350) is formed by bonding one end (351a) and the other end (351b) of the metal sheet (351) with a mutually overlapping bonding surface using a conductive resin composition that is pre-applied as an adhesive. Referring to FIGS. 3 and 4, one end (351a) of the metal sheet (351) may be positioned inside the power unit (300), and the other end (351b) may be positioned outside the power unit (300). However, this is not limited thereto, and one end (351a) of the metal sheet (351) may be positioned outside the power unit (300), and the other end (351b) may be positioned inside the power unit (300).

[0067] In addition, in the embodiments illustrated in FIGS. 3 and 4, the recess (352) and protrusion (353) formed on the joint surface of the joint (350s) are shown as having an angular shape, but are not limited thereto, and the recess (352) and protrusion (353) formed on the joint surface of the joint (350s) may be formed with rounded corners or a curved shape with a gentle slope.

[0068] Additionally, the recess (352) and the protruding part (353) formed on the joint surface of the joint (350s) may be formed to extend along the longitudinal direction of the power unit, and in this case, the joint strength of the joint (350s) may be further improved. However, this is not limited thereto, and the recess (352) and the protruding part (353) formed on the joint surface may be formed to extend along the longitudinal direction of the power unit but spaced apart at a predetermined interval.

[0069] Additionally, it is preferable that the recesses (352) and protrusions (353) formed on the joint surface of the joint portion (350s) are each provided in multiple numbers. In this case, the recesses (352) and protrusions (353) formed on the joint surface of the joint portion (350s) are formed alternately in multiple numbers, and the multiple recesses (352) and protrusions (353) may be provided extending parallel to each other along the longitudinal direction of the power unit (300). However, this is not limited thereto, and the multiple recesses (352) and protrusions (353) may be provided tilted at a certain angle along the longitudinal direction of the power unit (300), but it is preferable that they be provided extending parallel to each other along the longitudinal direction of the power unit (300) in terms of ease of manufacturing of the recesses (352) and protrusions (353).

[0070] As illustrated in FIGS. 3 and 4, the present invention is a structure in which a recess (352) and a protrusion (353) are provided on the bonding surface of a bonding part (350s) so that the bonding surface is bonded when bonded by an adhesive, and compared to the case where a smooth bonding surface is formed without the recess (352) and the protrusion (353), the bonding length in the circumferential direction of the power unit (300) is increased so that the bonding strength can be improved.

[0071] Furthermore, the thickness (t) of the metal sheet (351) constituting the metal shielding layer (350) 1a , t 1b ) may have a thickness that can satisfy the electrical characteristics required for the submarine cable (1000) of the present invention and the durability required in a dynamic environment, and preferably may be 0.1 millimeters to 2.0 millimeters (mm).

[0072] In this case, the thickness (t2) of the joint (350s) of the metal shielding layer (350) may be 0.12 millimeters to 3.60 millimeters (mm), preferably 0.14 millimeters to 3.2 millimeters (mm). Additionally, the length of the joint surface in the circumferential cross-section of the joint (350s) may be 1 millimeter to 5 millimeters (mm).

[0073] If, in configuring the joint (350s), the lumbar and protruding parts are omitted and the two ends of the metal sheet (351) are simply overlapped and joined together, the thickness (t2) of the joint (350s) is the thickness (t) of one side of the metal sheet (351). 1a ) and the thickness of the other side (t 1b Although it becomes the sum of ), in the present invention, the joining surface at the joining portion (350s) of the metal shielding layer (350) is formed by mutually joining the recess (352) and the protruding portion (353), and as described above, since press processing or the like is performed to reduce the thickness of a specific area of ​​the metal sheet (351) when forming the recess, the thickness (t2) of the joining portion (350s) is the thickness (t) of one side of the metal sheet (351). 1a ) and the thickness of the other side (t 1b Since it can be formed to be smaller than the sum of ), the protruding thickness caused by the joint (350s) of the metal shielding layer (350) can be minimized.

[0074] As a result, the thickness (t2) of the joint (350s) and the thickness (t) in the non-joint region of the metal sheet (351) 1a , t 1b The difference between them is reduced, so that the protruding portion of the outer surface of the metal shielding layer (350) is minimized, thereby minimizing the formation of unnecessary voids between the metal shielding layer (350) and the polymer sheath layer (360), preventing moisture penetration into the power unit (300), and improving the durability of the power unit (300).

[0075] Figure 5 shows a perspective view of a metal sheet forming a metal shielding layer as illustrated in Figure 4.

[0076] Referring to FIG. 5, the metal sheet (351) constituting the metal shielding layer (350) may have at least one recess (352) and a protrusion (353) formed along the longitudinal direction of the metal sheet (351) at each of the two ends (351a, 351b) in the width direction. In the drawing shown in FIG. 4, the recess (352) formed on the surface of the metal sheet (351) may refer to an area where the thickness of the metal sheet (351) is reduced, and the protrusion (352) may refer to an area where the thickness of the metal sheet (351) is not reduced.

[0077] Preferably, the thickness of the recess (352) in the regions of one end (351a) and the other end (351b) of the metal sheet (351) can be formed to be 20% to 80% of the thickness of the iron portion (353), preferably 40% to 60%. If the thickness of the recess (352) is less than 20% of the thickness of the iron portion (353), the durability of the metal shielding layer (350) may be reduced, and if it exceeds 80%, it may be difficult to form an uneven structure on the bonding surface and the effect of increasing bonding strength may be insufficient.

[0078] And, the recess (352) and the protrusion (353) formed at one end (351a) of the metal sheet (351) are formed on the upper surface of the metal sheet (351), and the recess (352) and the protrusion (353) formed at the other end (351b) are formed on the lower surface of the metal sheet (351). In this way, the recess (352) and the protrusion (353) are formed on different surfaces of the one end (351a) and the other end (351b) of the metal sheet (351), so that when the metal sheet (351) is rolled into a circle, the recess (352) and the protrusion (353) provided at each of the two ends can be configured to face each other.

[0079] Additionally, each recess (352) formed on the upper surface of one end (351a) of the metal sheet (351) has the same width as each protrusion (353) formed on the lower surface of the other end (351b) at a corresponding position, and each protrusion (353) formed on the upper surface of the one end (351a) can have the same width as each recess (352) formed on the lower surface of the other end (351b) at a corresponding position. Thus, when the metal sheet (351) is rolled into a circle to form a metal shielding layer (350), an uneven structure that fits together with each other can be formed on the joint surface of the joint portion (350s).

[0080] The recess (353) of the joint portion (350s) can be formed by cutting a smooth metal sheet (351) to a preset width and simultaneously press-forming both ends of the metal sheet (351). For example, when cutting a smooth metal sheet (351) to a preset width using a roller, a mechanism for forming the recess (353) of the joint portion (350s) can be attached to the inside of the cutting point of the metal sheet (351) so that the metal sheet (351) is cut to a preset width and simultaneously press-formed by the mechanism provided inside the cutting point, thereby forming the recess (353) of the joint portion (350s).

[0081] That is, since the width of the metal sheet (351) for forming the metal shielding layer (350) according to the present invention is cut and the recesses (353) are formed at both ends at the same time through press processing, the manufacturing time of the metal sheet (351) for forming the metal shielding layer (350) according to the present invention can be shortened.

[0082] The present invention involves rolling a metal sheet (351) constituting a metal shielding layer (350) into a circular shape and joining it, wherein an uneven structure is formed on the joining surface of the joint portion (350s) joined in a state where both ends of the metal sheet (351) overlap each other. This increases the joining area per unit length, thereby improving the joining strength, and acts like a latch to prevent the joining surface from separating in a dynamic environment. As a result, both ends of the metal sheet (351) are firmly joined to each other, thereby ensuring excellent water barrier performance, shielding performance, and durability.

[0083] Although this specification has been described with reference to preferred embodiments of the present invention, those skilled in the art may modify and change the present invention in various ways without departing from the spirit and scope of the present invention as described in the claims below. Therefore, if a modified embodiment basically includes the components of the claims of the present invention, it should be considered to be included within the technical scope of the present invention.

Claims

1. In a power unit included in at least one submarine cable, It comprises a conductor, an inner semiconducting layer surrounding the conductor, an insulating layer surrounding the inner semiconducting layer, an outer semiconducting layer surrounding the insulating layer, a metal shielding layer surrounding the outer semiconducting layer, and a polymer sheath layer surrounding the metal shielding layer. A power unit characterized in that the metal shielding layer comprises a joint in which both ends of a metal sheet are joined in a mutually overlapping state, and the joint comprises at least one recess and a protrusion that are mutually fitted to each of the joint surfaces between the two ends of the metal sheet.

2. In Paragraph 1, A power unit characterized by the above-mentioned metal shielding layer being non-wrinkled.

3. In Paragraph 1, A power unit characterized in that the thickness of the metal sheet is 0.1 millimeters to 2.0 millimeters (mm) and the thickness of the joint is 0.12 millimeters to 3.60 millimeters (mm).

4. In Paragraph 3, A power unit characterized in that the bonding length of the bonding surface in the circumferential cross-section of the above-mentioned bonding part is 1 millimeter to 5 millimeters (mm).

5. In Paragraph 1, A power unit characterized in that the metal sheet constituting the metal shielding layer is made of copper or a copper alloy.

6. In Paragraph 1, A power unit characterized by the fact that the recess and protrusion formed on the joint surface of the above-mentioned joint are formed to extend along the longitudinal direction of the power unit.

7. In Paragraph 1, A power unit characterized by having a plurality of recesses and protrusions formed on the joint surface of the above-mentioned joint.

8. In Paragraph 7, A power unit characterized by having a plurality of lumbar and iron parts extended parallel to the longitudinal direction of the power unit.

9. In Paragraph 1, A power unit characterized by the above-mentioned joint being formed by applying an adhesive made of a conductive resin composition to the joint surface.

10. In Paragraph 1, A power unit characterized in that the above-mentioned lumbar and iron parts are respectively formed on the upper surface of one end and the lower surface of the other end of the metal sheet.

11. In Paragraph 1, A power unit characterized by forming the main part of the above joint by cutting a smooth metal sheet to a preset width and simultaneously press-forming both ends of the metal sheet.

12. A power unit of any one of the plurality of claims 1 through 11; A plurality of cable interpositions provided in the region between the plurality of power units above; A binding taping layer for finishing a plurality of power units and a plurality of cable inserts in a circular shape; A bedding layer provided on the outer side of the above binding taping layer; An armor layer provided on the outer side of the above bedding layer; and, A power unit characterized by additionally including an outermost layer provided on the outer side of the above armor layer and comprising a polymer resin material.

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