Submarine cable

Abstract

The present invention relates to a submarine cable. More particularly, by forming a shielding layer of a power unit with metal wires and a metal braided structure surrounding the metal wires, and optimizing the outer diameters of the metal wires and the outer diameters of strands forming the metal braided structure, it is possible to prevent metal wire disconnection and breakage of the strands in the metal braided structure, caused by excessive pressure between the metal wires and the metal braided structure, or a reduction in durability, and to minimize physical damage to the shielding layer and degradation of shielding function by making the metal braided structure have flexibility and elasticity above a certain level.

Description

submarine cable

[0001] The present invention relates to a submarine cable. More specifically, it relates to a submarine cable that minimizes damage to the shielding layer caused by a break in the metal wire or a break in the wire of the metal braid, has a certain level of flexibility and elasticity of the metal braid, and prevents the formation of protrusions on the outside of the sheath layer.

[0002] Recently, renewable energy systems that supply electricity generated by installing wind turbines and other equipment in distant offshore areas with sufficient wind speeds at a certain distance from land, connecting them to onshore power facilities via power cables, are gaining attention.

[0003] In cases where the water depth of the sea where wind turbines are installed is shallow, a structure may be installed on the seabed and the wind turbine installed on top of it; however, in cases where the water depth is deep, the wind turbine may be installed using a floating method.

[0004] In addition, wind turbines installed offshore, or substations connecting those wind turbines, and onshore power facilities can be connected by submarine cables laid underwater.

[0005] Here, the section from onshore power facilities to the seabed near offshore wind turbines is where submarine cables are laid on the seabed. Since no movement occurs in the cable while transmitting power after laying, this section is called the static section, and the submarine cable laid in this section is generally referred to as a static submarine cable. On the other hand, the section from the seabed near the wind turbines to floating wind turbines or substations is subject to significant cable bending, tensioning, or twisting due to ocean currents and waves. Therefore, this section is called the dynamic section, and the submarine cable laid in this section is referred to as a dynamic submarine cable.

[0006] 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, and lead-sheathed shield layers are difficult to apply as a shielding layer that cannot withstand such environments to dynamic submarine cables.

[0007] Therefore, dynamic submarine cables generally form a metal wire layer by winding multiple metal wires spirally and spaced apart from each other around the outer surface of an outer semiconducting layer instead of a lead-sheathed shield layer, and form a shielding layer by winding a metal tape around the outside of it.

[0008] Meanwhile, dynamic submarine cables may experience problems where the metal tape tears due to pressure or stress in the harsh underwater environment. To resolve this, applying a metal braided wire instead of the metal tape can prevent damage to the shielding layer due to the elasticity of the metal braid.

[0009] However, due to repeated bending or tensioning of the submarine cable, the metal wire and the metal braid are strongly pressed against each other, which may cause the metal wire to break or the individual wires of the metal braid to break, and there is a risk that the shielding function of the shielding layer will be degraded.

[0010] Excessive compression between the metal wires constituting the shielding layer and the metal braid can be mitigated to some extent by making the outer diameter of the metal wires or the outer diameter of the wires of the metal braid small. However, if the outer diameter of the metal wires or the outer diameter of the wires of the metal braid becomes excessively small, the durability and mechanical strength of the shielding layer decrease, which may actually accelerate damage to the shielding layer.

[0011] Meanwhile, the thickness of the metal braid affects the outer diameter of the cable. If the thickness of the metal braid is increased, a protrusion is formed outside the sheath layer surrounding the outer side of the metal braid, causing severe friction between the shielding layer and the internal components of the cable, which can lead to damage to the power unit, i.e., damage to the sheath layer. To solve this, the thickness of the sheath layer can be increased, but this may increase the outer diameter of the submarine cable.

[0012] If the outer diameter of a submarine cable increases, handling becomes difficult when installing the cable on the seabed, making installation work challenging. Additionally, as mechanical stress generated on the seabed increases, the load applied to the submarine cable increases, which may raise the risk of damage.

[0013] Therefore, in order to minimize damage to the shielding layer caused by breakage of the metal wire or breakage of the metal braid, and to ensure that the flexibility and elasticity of the metal braid for use in dynamic submarine cables are above a certain level, and at the same time prevent the formation of protrusions outside the sheath layer, a submarine cable is required that can optimize the outer diameter of the metal wire, the outer diameter of the metal braid, and the thickness of the metal braid.

[0014] The present invention aims to solve the problem of providing a submarine cable that minimizes damage to the shielding layer caused by breakage of the metal wire or breakage of the metal braid by optimizing the outer diameter of the metal wire constituting the shielding layer, the outer diameter of the wire of the metal braid surrounding the outer side of the metal wire, and the thickness of the metal braid, while ensuring that the flexibility and elasticity of the metal braid are above a certain level and preventing the formation of protrusions on the outside of the sheath layer.

[0015] To solve the above problem, the present invention provides a submarine cable comprising at least one power unit, wherein the power unit comprises 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, a shielding layer provided on the outer side of the outer semiconducting layer, and a sheath layer surrounding the shielding layer, wherein the shielding layer comprises a plurality of metal wires that are spaced apart from the outer side of the outer semiconducting layer and are spirally wound, and a metal braided body that is wound on the outer side of the plurality of metal wires, wherein the metal braided body is formed by braiding a bundle of wires composed of a plurality of wires, the outer diameter of the metal wire is 4 to 11.5 times the outer diameter of the wire constituting the metal braided body, and the thickness of the metal braided body is 3.5 to 10 times the outer diameter of the wire constituting the metal braided body.

[0016] In addition, the outer diameter of the metal wire may be 0.8 millimeters to 2.0 millimeters (mm).

[0017] In addition, the outer diameter of the wire constituting the metal braid may be 0.16 millimeters to 0.254 millimeters (mm).

[0018] Here, the metal braid has a flat strap shape in which the width of the cross-section is greater than the thickness, and the thickness of the metal braid may be 0.5 to 2 times the outer diameter of the metal wire.

[0019] In this case, the thickness of the metal braid may be 0.8 millimeters to 1.5 millimeters (mm).

[0020] And, the metal wire and the metal braid can be transversely wound in the same spiral direction.

[0021] In addition, the metal wire and the metal braid can be wound transversely in different directions.

[0022] Also, the transverse winding pitch of the metal braid may be smaller than the transverse winding pitch of the metal wire.

[0023] Here, the transverse winding pitch of the metal braid may be larger than the transverse winding width of the metal braid.

[0024] In this case, the sheath layer is made of a polymer resin, and the thickness of the sheath layer may be 1.5 to 10 times the outer diameter of the metal wire.

[0025] In addition, some of the wires of the metal braid placed on the metal wire may be plastically deformed by contact and friction with the metal wire.

[0026] Additionally, the submarine cable may include a plurality of power units; a plurality of shape fillers disposed between the power units to accommodate the power units while spaced apart from each other, and having a circular shape on their outer surface together with the power units; at least one optical unit accommodated in at least one of the shape fillers and having an optical fiber; a bedding layer provided outside the plurality of power units and the plurality of shape fillers; at least one armor layer provided with a plurality of armor wires wound transversely and disposed outside the bedding layer; and an outermost layer provided outside the armor layer.

[0027] According to the submarine cable of the present invention, the shielding layer of the power unit constituting the submarine cable is composed of a metal wire and a metal braiding body surrounding it, and by optimizing the outer diameter of the metal wire and the outer diameter of the wire constituting the metal braiding body, the phenomenon of the metal wire being cut off due to excessive compression or reduced durability between the metal wire and the metal braiding body and the wire breaking of the metal braiding body are prevented, and the flexibility and elasticity of the metal braiding body are made to be above a certain level, thereby minimizing physical damage to the shielding layer and the degradation of the shielding function.

[0028] In addition, according to the submarine cable of the present invention, by optimizing the thickness of the metal braiding body, the wire breakage phenomenon of the metal braiding body is prevented, and at the same time, the phenomenon of protrusions being formed in the sheath layer surrounding the shielding layer due to the increase in the thickness of the metal braiding body is prevented, thereby minimizing damage to the power unit.

[0029] In addition, according to the submarine cable of the present invention, the transverse winding directions of the metal wire and the metal braid constituting the shielding layer are configured to be the same or different. When the transverse winding directions of the metal wire and the metal braid are configured to be the same, the flexibility of the submarine cable is improved, and conversely, when the transverse winding directions are configured to be different, the adhesion between the metal wire and the metal braid is strengthened, thereby lowering the electrical resistance.

[0030] FIG. 1 illustrates one embodiment of an offshore wind power generation system connected by a submarine cable.

[0031] FIG. 2 shows a multi-stage stripped perspective view of a dynamic submarine cable for underwater laying according to the present invention.

[0032] FIG. 3 shows a perspective view and a partial enlarged view of one embodiment of a power unit according to the present invention.

[0033] FIG. 4 shows a perspective view and a partial enlarged view of another embodiment of a power unit according to the present invention.

[0034] FIG. 5 illustrates a metal braided body constituting a shielding layer of a power unit according to the present invention.

[0035] Figure 6 shows a photograph of the exterior of a metal braid according to an embodiment.

[0036] Figure 7 shows a photograph of the appearance of a metal braid according to a comparative example.

[0037] 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.

[0038] FIG. 1 illustrates one embodiment of an offshore wind power generation system connected by a submarine cable.

[0039] In cases where the water depth of the sea where the wind turbine (wb) is installed is shallow, the wind turbine can be installed on top of a structure installed on the seabed, but in cases where the water depth is deep, the wind turbine (wb) and substation equipment (ts) can be installed in a floating manner.

[0040] Floating type wind turbines (wb) and substation equipment (ts), etc. are supported by floating materials for floating and float above the sea surface, and are connected to an anchor (a) installed on the seabed by a support line (r) so that movement may be restricted.

[0041] In addition, a wind turbine (wb) installed offshore, or a substation (ts) and power equipment (ps) connecting the wind turbine (wb), can be connected by a submarine cable laid underwater.

[0042] Here, the section from the ground power facility (ps) to the seabed (g) is the section where the submarine cable is laid on the seabed. Since no movement of the cable occurs while transmitting power after laying the cable, this section is called a static section, and the submarine cable laid in this section is generally called a static submarine cable (300).

[0043] On the other hand, between floating type wind turbines (wb), from a wind turbine (wb) to a substation (ts), or from a substation (ts) to an intermediate connection box (200) on the seabed (g), since the cable undergoes a lot of bending, tensioning, or twisting due to ocean currents, waves, etc., this section is called a dynamic section (dynamic section), and the submarine cable laid in this section is called a dynamic submarine cable (100).

[0044] The dynamic submarine cable (100) is laid underwater, and in cases where the water depth is deep, a floating module (b) may be provided in a certain section. By maintaining a floating state where the submarine cable is floated underwater by the floating module (b), the submarine cable (100) is prevented from colliding with sharp rocks or obstacles in the sea, and maintenance is facilitated by allowing the submarine cable to be easily manipulated and moved underwater through the floating module (b). Additionally, the floating module (b) can visually indicate the location of the submarine cable, providing an identification function during marine operations.

[0045] In addition, a stiffener(s) may be installed at the connection point between the submarine cable and the surface facility, or between the dynamic submarine cable (100) and the static submarine cable (300). The stiffener(s) can perform the function of preventing cable damage by dispersing the bending moment when bending occurs at the connection point of the submarine cable.

[0046] FIG. 2 shows a multi-stage stripped perspective view of a dynamic submarine cable for underwater laying according to the present invention.

[0047] A submarine cable (100) according to one embodiment of the present invention may include a cable core portion comprising one or more power units for power transmission and a cable protection layer surrounding the outer side of the cable core portion.

[0048] The above cable core may include three power units (10a, 10b, 10c), 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 a jacket layer (110). A detailed description of each component will be provided later.

[0049] In the embodiment of the present invention, a three-phase cable having three power units (10a, 10b, 10c) is illustrated as an example, but the present invention is not limited thereto and may be applied in cases where there is one power unit or the number of power units is different.

[0050] Each power unit (10a, 10b, 10c) may be configured to include a conductor (11), an inner semiconducting layer (12), an insulating layer (13), an outer semiconducting layer (14), a shielding layer (15), and a sheath layer (16).

[0051] The above conductor (11) serves as a passage for current to flow to transmit power, and can be made of a material having excellent conductivity and strength and flexibility suitable for cable manufacturing and use, such as copper or aluminum, so as to minimize power loss.

[0052] As shown in FIG. 2, the above conductor (11) may be a composite conductor formed by twisting a plurality of circular wires together to form a circle, and specifically, may be a composite conductor formed by twisting in the S direction or the Z direction. However, it is not limited thereto, and the conductor (11) may be a flat conductor comprising a layer of flat wires formed by twisting a circular central wire and flat wires wrapped around the circular central wire.

[0053] However, the surface of the above conductor (11) is not smooth, so the electric field may be uneven and corona discharge may occur in some parts. In addition, if a gap is formed between the surface of the above conductor (11) and the insulating layer (13) described later, the insulation performance may be reduced.

[0054] 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.

[0055] The above-mentioned internal semiconducting layer (12) performs the function of stabilizing insulation performance by preventing a sudden change in the electric field between the conductor (11) and the insulating layer (13) described later. In addition, by suppressing the uneven charge distribution on the surface of the conductor (11), the electric field is made uniform, and by preventing the formation of a gap between the conductor (11) and the insulating layer (13), corona discharge, insulation breakdown, etc., can be suppressed.

[0056] The insulating layer (13) is provided on the outside of the inner semiconducting layer (12) to electrically insulate it from the outside so that current flowing along the conductor (11) does not leak out. Generally, the insulating layer (13) must have a high breakdown voltage and be able to maintain its insulating performance stably for a long period. Furthermore, it must have low dielectric loss and possess thermal resistance performance such as heat resistance. Accordingly, the insulating layer (13) may be made of polyolefin resins such as polyethylene and polypropylene, and the polyethylene resin may be made of a cross-linked resin.

[0057] An outer semiconducting layer (14) may be provided on the outside of the insulating layer (13). The outer semiconducting layer (14) is composed of a material having semiconductive properties, such as carbon black, carbon nanotubes, carbon nanoplates, graphite, etc., added to an insulating material like the inner semiconducting layer (12), and stabilizes insulation performance by suppressing the non-uniform charge distribution between the insulating layer (13) and the shielding layer (15) described later. In addition, the outer semiconducting layer (14) can smooth the surface of the insulating layer (13) in the cable to mitigate electric field concentration and prevent corona discharge, and can also perform the function of physically protecting the insulating layer (13).

[0058] A shielding layer (15) and a sheath layer (16) may be provided on the outside of the outer semiconducting layer (14). The shielding layer (15) and the sheath layer (16) can protect each power unit (10a, 10b, 10c) from various environmental factors such as moisture penetration, mechanical damage, and corrosion that may affect the power transmission performance of the cable.

[0059] The shielding layer (15) not only protects the power unit (10a, 10b, 10c) from external shocks, but also acts as a passage for fault current to flow when an accident such as a ground fault or short circuit occurs at the end of the power unit (10a, 10b, 10c), thereby shielding the electric field so that it is not discharged outside the power unit (10a, 10b, 10c).

[0060] As shown in FIG. 2, the dynamic submarine cable (100) is subjected to long-term repetitive friction and load due to movement or bending caused by ocean currents or waves. Since it is difficult to apply a lead-sheath shield layer that cannot withstand such an environment as a shielding layer, a metal wire layer can be formed by winding a plurality of metal wires horizontally on the outer surface of an outer semiconducting layer in a spaced-apart manner instead of a lead-sheath shield layer, and a shielding member can be wound horizontally on the outside to conduct current to the metal wires as a whole.

[0061] The shielding member that is transversely wound on the outer side of the metal wire constituting the shielding layer is generally composed of a metal tape made of a material such as copper, but the metal tape frequently tears due to external pressure or tension, and in order to solve this problem, the present invention transversely wound a metal braided body (153) composed of a plurality of wires braided together as a shielding member on the outer side of the metal wire (151) instead of a metal tape.

[0062] In addition, the present invention minimizes damage to the shielding layer caused by a break in the metal wire or a break in the metal braiding wire by optimizing the outer diameter of the metal wire constituting the shielding layer of the submarine cable (100), the outer diameter of the wire of the metal braiding that surrounds the outer side of the metal wire, and the thickness of the metal braiding, and prevents an increase in the outer diameter of the cable.

[0063] The shielding layer (15) of each power unit (10a, 10b, 10c) illustrated in FIG. 2 may be composed of a plurality of metal wires (151) wound transversely along the longitudinal direction of the power unit (10a, 10b, 10c) and a metal braid (153) wound transversely on the outer side of the metal wires (151). A detailed description of the structure of the shielding layer (15) will be provided later.

[0064] On the outside of the shielding layer (15), a sheath layer (16) composed of a polymer resin such as polyvinyl chloride (PVC) or polyethylene (PE) is extruded to improve the corrosion resistance and water-blocking properties of the submarine cable and to perform the function of protecting the cable from external environmental factors such as mechanical damage, heat, and ultraviolet rays. In particular, for submarine cables, it is preferable to use polyethylene resin, which has excellent water-blocking properties.

[0065] Additionally, the power units (10a, 10b, 10c) may additionally be provided with a copper wire tape (not shown) or a moisture absorbing layer (not shown) between the shielding layer (15) and the outer semiconducting layer (14). Additionally, the moisture absorbing layer (not shown) may be additionally provided between the shielding layer (15) and the sheath layer (16).

[0066] The above copper wire insertion tape is composed of copper wire and non-woven tape, etc., and can facilitate electrical contact between the outer semiconducting layer (14) and the shielding layer (15).

[0067] The above moisture absorption layer (not shown) may be formed in the form of a powder, tape, coating layer, or film containing a super absorbent polymer (SAP) that has a fast rate of absorbing moisture penetrating into the cable and excellent ability to maintain an absorbent swelling state. Accordingly, the above moisture absorption layer can prevent moisture from penetrating in the longitudinal direction of the cable. In addition, the moisture absorption layer may be configured to include a copper wire to prevent abrupt changes in the electric field in the above moisture absorption layer.

[0068] In particular, when metal wire (151) and metal braid (153) are applied as a shielding layer (15) laid in the dynamic section of the seabed, the water-blocking performance is inferior to that of a lead sheath, so it is desirable to additionally provide a water-absorbing layer (not shown) to improve the water-blocking performance.

[0069] Additionally, the submarine cable (100) may be equipped with an optical unit (20). Here, the optical unit (20) may be equipped with at least one optical fiber (21) and a tube (22) that accommodates the optical fiber (21).

[0070] The optical unit (20) is provided with a predetermined number of optical fibers (21) mounted together with a filler (not shown) within a tube (22), and the tube (22) may be made of a material with high rigidity such as stainless steel. Additionally, the optical unit (20) may further be provided with a metal sheath (23) and a polymer sheath (24) that surround the tube (22).

[0071] As illustrated in FIG. 2, the submarine cable (100) according to the present invention may include a plurality of shape fillers (30) to accommodate a plurality of power units (10a, 10b, 10c) spaced apart from each other and to make the shape of the outer surface circular together with the plurality of power units (10a, 10b, 10c).

[0072]

[0073] *Conventionally, the filler material was composed of a yarn made of polypropylene, but the present invention may be provided with a shape filler (30) as the filler material, which is more advantageous for maintaining the cable shape of the submarine cable and protecting the internal structure. The shape filler (30) is a shape insert formed by extrusion of a material such as high-density polyethylene (HDPE) or polyethylene (PE), which has excellent chemical resistance, weather resistance, and water pressure resistance.

[0074] In addition, the shape filler (30) can accommodate a light unit (20) in at least one light unit receiving portion formed therein.

[0075] Additionally, as shown in FIG. 2, a binding tape layer (60) may be further provided to wrap a plurality of shape fillers (30) so that the cable core portion maintains a circular shape. The binding tape layer (60) may allow the plurality of shape fillers (30) to maintain a mutually supported state.

[0076] Meanwhile, the submarine cable (100) illustrated in FIG. 2 may be equipped with a cable protection layer to protect the internal structure even in harsh environments such as seawater and salt in the sea.

[0077] As illustrated in FIG. 2, according to one embodiment of the present invention, the cable protection layer of the submarine cable (100) may include a bedding layer (70) provided on the outside of the shape filler (30).

[0078] The above bedding layer (70) serves as a cushion for placing the armor layer (80), protects the submarine cable (100) from external impacts, and increases mechanical strength. An armor layer (80) that enhances mechanical properties and performance in a submarine environment is placed on the outside of the above bedding layer (70), and a jacket layer (110) may be provided on the outside thereof.

[0079] The above armor layer (80) strengthens the mechanical properties of the submarine cable (100) and provides additional protection from the external environment. The above armor layer (80) may be composed of at least one armor wire layer (80a, 80b).

[0080] The armor wire of the above armor wire layer (80a, 80b) is preferably composed of a metal material, but it may also be a non-metal material if it is a material with high tensile strength. The metal armor wire may be made of steel, galvanized steel, copper, brass, bronze, etc., and is arranged in a spiral transverse winding manner with a cross-sectional shape that is circular or flat. In the case of the non-metal armor wire, it may be formed into a wire shape using a high-tensile material such as aramid fiber or ultra-high molecular weight polyethylene fiber.

[0081] In the embodiments of the present invention, a metal armor layer composed of a metal armor wire is described, but the present invention is not limited thereto.

[0082] The armor wire is wound spirally on the outer surface of the bedding layer (70) and may be wound in a Z direction or an S direction opposite to the assembly direction of the plurality of power units (10a, 10b, 10c). However, it is not limited thereto, and the armor wire may be wound in the same direction as the assembly direction of the plurality of power units (10a, 10b, 10c).

[0083] In addition, for a submarine cable (100) used in a dynamic section, the armor layer (80) may be configured in a multi-layer structure to reinforce rigidity, and the wire transverse winding direction of each layer may be different from each other.

[0084] Meanwhile, the submarine cable (300 in FIG. 1) installed in the static section may include a single layer armor layer and a serving layer on the outside thereof, but the submarine cable (100) used in the dynamic section may additionally have a jacket layer (110) on the outside of the armor layer (80).

[0085] For example, the jacket layer (110) is made of a polymer resin such as polyvinyl chloride (PVC) or polyethylene (PE) produced by an extrusion method, and protects the armor layer (80) while minimizing damage to the submarine cable (100) from external forces occurring in the underwater environment, such as waves and currents, thereby providing sufficient durability.

[0086] FIG. 3 shows a perspective view and a partial enlarged view of one embodiment of a power unit according to the present invention, FIG. 4 shows a perspective view and a partial enlarged view of another embodiment of a power unit according to the present invention, and FIG. 5 shows a metal braided body constituting a shielding layer of a power unit according to the present invention.

[0087] A power unit (10) according to the present invention may be configured to include a conductor (11), an inner semiconducting layer (12) surrounding the conductor (11), 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 shielding layer (15) provided on the outer side of the outer semiconducting layer (14), as described above.

[0088] Additionally, the shielding layer (15) of the power unit (10) according to the present invention may be configured to include a plurality of metal wires (151) that are spirally spaced apart and transversely wound on the outer side of the outer semiconducting layer (14), and a metal braid (153) that is transversely wound on the outer side of the plurality of metal wires (151).

[0089] The metal wire (151) and the strands (153') constituting the metal braid (153) may be made of a metal material with high electrical conductivity, such as copper, copper alloy, or tin-plated copper. However, in the case of tin-plated copper, the surface may become rough, causing wear or conductor abrasion on the surface of the wire or strands (153'), so a separate coating treatment may be required to solve this problem.

[0090] The metal braid (153) constituting the shielding layer (15) may be configured in a braiding manner of wire bundles (153B) composed of a plurality of wires (153'). The wire bundles (153B) may be configured, for example, in a form in which 2 to 10 wires (153') are assembled side by side, and the wire bundles (153B) may be manufactured as a metal braid (153) by forming a specific braiding pattern as they are arranged in an alternating direction that intersects each other.

[0091] Additionally, the metal braid (153) may have a flat strap shape in cross-section in which the width is greater than the thickness. Thanks to this flat strap shape, the metal braid (153) has improved elasticity, and thus can flexibly respond to tension, bending, etc. occurring in the seabed environment, thereby effectively preventing damage to the shielding layer (15).

[0092] Meanwhile, when bending or flexing occurs in the submarine cable (100), external forces such as load and tensile force transmitted to the submarine cable (100) are transmitted to the internal components of the cable, including the armor layer (80). At this time, the shielding layer (15) of the power unit (10) is compressed by structural elements such as the armor layer (80), which has high mechanical strength, and the metal wire (151) and the metal braid (153) are pressed by strong pressure. In this process, a breakage phenomenon may occur in the metal wire (151), and a problem may also occur in which the thin wire (153') constituting the metal braid (153) is broken.

[0093] This problem can cause damage to the shielding layer (15) and delay the transmission of fault current to adjacent metal wires through the metal braiding, which can consequently degrade the shielding function of the submarine cable (100).

[0094] To solve these problems, the present invention optimizes the outer diameter (d1) of the metal wire (151) constituting the shielding layer (15) of the power unit (10) and the outer diameter (d2) of the wire (153') constituting the metal braid (153) so as to prevent the metal wire (151) from being severed and the wire (153') of the metal braid (153) from being broken due to excessive pressure or reduced durability between the metal wire (151) and the metal braid (153), thereby minimizing physical damage to the shielding layer (15) and the reduction of the shielding function.

[0095] Specifically, in the shielding layer (15) of the power unit (10) according to the present invention, the outer diameter (d1) of the metal wire (151) can be configured within a range of 4 to 11.5 times the outer diameter (d2) of the wire (153') constituting the metal braid (153).

[0096] If the outer diameter (d1) of the metal wire (151) deviates from the range of 4 to 11.5 times the outer diameter (d2) of the wire (153') constituting the metal braid (153), the durability and mechanical strength of the metal wire (151) or the metal braid (153) are significantly reduced, and when bending or bending of the submarine cable (100) occurs in a dynamic environment, the metal wire (151) may be severed or the wire (153') constituting the metal braid (153) may be severed, and the flexibility and elasticity of the metal braid (153) may be significantly reduced.

[0097] For example, if the outer diameter (d1) of the metal wire (151) is too small and is less than four times the outer diameter (d2) of the wire (153') constituting the metal braid (153), the metal wire (151) may not withstand strong pressure and compression when bending or bending of the submarine cable (100) occurs in a dynamic environment, and the metal wire (151) may break.

[0098] As another example, if the outer diameter (d1) of the metal wire (151) is excessively large and exceeds 11.5 times the outer diameter (d2) of the wire (153') constituting the metal braid (153), strong pressure may be applied to the metal wire (151) against the metal braid (153) when bending or twisting of the submarine cable (100) occurs in a dynamic environment, and a break may occur in the wire (153') constituting the metal braid (153).

[0099] As another example, if the outer diameter (d2) of the wire (153') constituting the metal braid (153) is too small and is less than 1 / 11.5 times the outer diameter (d1) of the metal wire (151), a break may occur in the wire (153') constituting the metal braid (153) when it is in friction with the metal wire (151) placed on the inside.

[0100] As another example, if the outer diameter (d2) of the wire (153') constituting the metal braid (153) is excessively large and exceeds 1 / 4 times the outer diameter (d1) of the metal wire (151), the thickness of the metal braid (153) increases excessively, and the flexibility and elasticity of the metal braid (153) may decrease. In this case, the outer diameter (d1) of the metal wire (151) may be configured within the range of 0.2 millimeters to 3.5 millimeters (mm), preferably 0.5 millimeters to 2.7 millimeters (mm), and more preferably 0.8 millimeters to 2.0 millimeters (mm).

[0101] In addition, the outer diameter (d2) of the wire (153') constituting the metal braid (153) can be configured within the range of 0.05 millimeters to 0.3 millimeters (mm), preferably 0.1 millimeters to 0.28 millimeters (mm), and more preferably 0.16 millimeters to 0.254 millimeters (mm).

[0102] Meanwhile, assuming that the number of wires (153') constituting the metal braid (153) is constant, the thickness (t) of the metal braid (153) is proportional to the outer diameter (d2) of the wires (153') constituting the metal braid (153), and if the thickness (t) of the metal braid (153) is too thin, the wires (153') constituting the metal braid (153) may break due to friction with the metal wire (151).

[0103] In addition, if the thickness (t) of the metal braid (153) is too thick, not only is flexibility and elasticity reduced, but when the sheath layer (16) is formed on the outside of the shielding layer (15), a protrusion (not shown) may be formed on the outer surface of the sheath layer (16) corresponding to the area where the metal wire (151) and the metal braid (153) overlap. If a protrusion (not shown) is formed on the sheath layer (16), severe friction may occur between the power unit (10) of the submarine cable (100) and the shape filler (30), and stress may be concentrated on the protrusion (not shown), causing the sheath layer (16) to tear or the structure of the shielding layer (15) to deform, thereby creating a risk of damage to the power unit (10).

[0104] Accordingly, in the present invention, not only is the outer diameter (d1) of the metal wire (151) and the outer diameter (d2) of the wire (153') constituting the metal braid (153) optimized, but the thickness (t) of the metal braid (153) is also optimized, thereby preventing the wire (153') of the metal braid (153) from breaking due to excessive friction or excessive pressure between the metal braid (153) and the metal wire (151) placed inside it, and at the same time, while maintaining flexibility and elasticity above a certain level, a protrusion (not shown) is not formed on the outer surface of the sheath layer (16), thereby preventing damage to the power unit (10) caused by the protrusion (not shown).

[0105] Specifically, the thickness (t) of the metal braid (153) in the shielding layer (15) of the power unit (10) according to the present invention can be configured within a range of 3.5 to 10 times the outer diameter (d2) of the wire (153') constituting the metal braid (153).

[0106] If the thickness (t) of the metal braid (153) is smaller than 3.5 times the outer diameter (d2) of the wire (153') constituting the metal braid (153), the durability of the metal braid (153) is reduced, so the wire (153') may easily break.

[0107] On the other hand, if the thickness (t) of the metal braid (153) exceeds 10 times the outer diameter (d2) of the wire constituting the metal braid (153), the flexibility and elasticity of the metal braid (153) may be reduced, and a protrusion (not shown) may be created on the outer surface of the sheath layer (16), which may cause damage to the power unit (10).

[0108] And, the thickness (t) of the metal braid (153) can be configured within the range of 0.2 millimeters to 3.0 millimeters (mm), preferably 0.4 millimeters to 2.1 millimeters (mm), and more preferably 0.8 millimeters to 1.5 millimeters (mm).

[0109] Meanwhile, the sheath layer (16) may be formed by extruding a polymer material on the outside of a shielding layer (15) composed of a metal wire (151) and a metal braid (153). In this case, if the thickness of the sheath layer (16) is excessively thin, there is a very high possibility that a protrusion (not shown) will be formed on the outer surface of the sheath layer (16) corresponding to the area where the metal wire (151) and the metal braid (153) overlap.

[0110] On the other hand, if the thickness of the sheath layer (16) is excessively thick, the outer diameter of the power unit (10) increases due to the increase in the thickness of the sheath layer (16), and consequently, the outer diameter of the submarine cable (100) may increase more than necessary, and the manufacturing cost will also increase as a result.

[0111] Therefore, not only the outer diameter (d1) of the metal wire (151), the outer diameter of the wire (153') constituting the metal braid (153), and the thickness (t) of the metal braid (153), but also the thickness of the sheath layer (16) needs to be optimized.

[0112] Specifically, the thickness of the sheath layer (16) of the power unit (10) according to the present invention may be 1.5 to 10 times the outer diameter (d1) of the metal wire (151). In this case, the formation of a protrusion (not shown) on the outer surface of the sheath layer (16) can be prevented, and the outer diameter of the submarine cable (100) can be prevented from increasing more than necessary, while also preventing an increase in manufacturing costs.

[0113] Here, the thickness of the sheath layer (16) can be configured within the range of 1.2 millimeters to 10.0 millimeters (mm), preferably 1.5 millimeters to 8.0 millimeters (mm), and more preferably 2.0 millimeters to 6 millimeters (mm). However, it is not limited thereto, and the thickness of the sheath layer (16) may be increased or decreased depending on the usage environment or application of the submarine cable (100).

[0114] In addition, the transverse winding pitch (Pt) of the metal braid (153) constituting the shielding layer (15) of the power unit (10) according to the present invention may be configured to be smaller than the transverse winding pitch (Pw) of the metal wire (151). In addition, the transverse winding pitch (Pt) of the metal braid (153) may be configured to be larger than the transverse winding width (Wt) of the metal braid (153).

[0115] Here, the transverse winding pitch (Pw) of the metal wire (151) refers to the longitudinal length of the power unit when the metal wire (151) is wound once on the outside of the outer semiconducting layer (14), the transverse winding pitch (Pt) of the metal braid (153) refers to the longitudinal length of the power unit when the metal braid (153) is wound once on the outside of the metal wire (151), and the transverse winding width (Wt) of the metal braid (153) refers to the width of the transversely wound metal braid (153) measured in the longitudinal direction of the power unit.

[0116] As described above, the transverse winding pitch (Pt) of the metal braid (153) can be formed to be smaller than the transverse winding pitch (Pw) of the metal wire (151). When the transverse winding pitch (Pt) of the metal braid (153) is formed to be smaller than the transverse winding pitch (Pw) of the metal wire (151), the length of the contact point between one metal wire (151) and another adjacent metal wire (151) is shortened by the metal braid (153), so the current flow rate of the fault current is increased, thereby preventing the generation of high-temperature heat and preventing a decrease in the durability of the submarine cable (100).

[0117] In addition, if the transverse winding pitch (Pt) of the metal braid (153) is configured to be smaller than the transverse winding pitch (Pw) of the metal wire (151), even if some of the metal wires (151) are disconnected, the fault current of the disconnected metal wire (151) can be quickly transmitted to an adjacent other metal wire (151).

[0118] Additionally, the transverse winding pitch (Pt) of the metal braid (153) can be configured to be larger than the transverse winding width (Wt) of the metal braid (153). In this way, if the transverse winding pitch (Pt) of the metal braid (153) is configured to be larger than the transverse winding width (Wt) of the metal braid (153), an overlapping area of ​​the transversely wound metal braid (153) does not occur, thereby preventing the disconnection of the metal wire (151) in contact with the interior of the metal braid (153).

[0119] Furthermore, the power unit (10) of the present invention may have the transverse winding directions of the metal wire (151) and the metal braid (153) constituting the shielding layer (15) configured to be the same or different from each other.

[0120] As shown in FIG. 3, the transverse winding direction of the metal wire (151) and the metal braid (153) constituting the shielding layer (15) can be configured in the same spiral direction (SS direction or ZZ direction).

[0121] In this way, the flexibility of the shielding layer (15) is improved by winding the metal wire (151) and the metal braid (153) constituting the shielding layer (15) in the same direction. Therefore, when bending or bending of the submarine cable (100) occurs in a submarine environment, the longitudinal flexibility of the shielding layer (15) is increased, and the possibility of damage to the metal wire (151) or the metal braid (153) can be reduced.

[0122] Additionally, as illustrated in FIG. 4, the transverse winding directions of the metal wire (151) and the metal braid (153) constituting the shielding layer (15) may be configured in different spiral directions. In the embodiment illustrated in FIG. 4, a configuration (SZ direction) is shown in which the metal wire (151) is transversely wound in the Z direction and the metal braid (153) is transversely wound in the S direction, but this is merely an example, and it may also be configured in an arrangement (ZS direction) in which the metal wire (151) is transversely wound in the S direction and the metal braid (153) is transversely wound in the Z direction.

[0123] In this way, when the metal wire (151) and the metal braid (153) constituting the shielding layer (15) are wound transversely in different directions, the adhesion or restraint force between the metal wire (151) and the metal braid (153) increases compared to when they are wound transversely in the same direction (SS direction or ZZ direction), and accordingly, the volume resistance per unit length is reduced, resulting in the effect of lowering the electrical resistance of the submarine cable (100).

[0124] The metal braid (153) is formed by braiding a group of wires (153B) consisting of a plurality of wires (153') to form a flat strap shape, and possesses flexibility and elasticity. Therefore, a certain degree of flexibility of the shielding layer (15) can be achieved even without the transverse winding direction of the metal wire (151) and the metal braid (153) being the same. Accordingly, depending on the underwater environment in which the submarine cable (100) is provided, if flexibility is secured even without the transverse winding direction of the metal wire (151) and the metal braid (153) being the same, it is desirable to provide an additional effect of lowering electrical resistance by transversely winding the metal wire (151) and the metal braid (153) in different directions.

[0125] Meanwhile, when the metal wire (151) and the metal braid (153) are wound transversely in different directions, flexibility may be reduced compared to when they are wound transversely in the same direction, so the risk of damage to the metal wire (151) or the metal braid (153) due to tension or stress of the submarine cable (100) may increase. To overcome this limitation, the outer diameter (d1) of the metal wire (151), the outer diameter (d2) of the wire (153') constituting the metal braid (153), and the thickness (t) of the metal braid (153) may be optimized to the aforementioned ranges to compensate for the disadvantages of the different transverse winding directions of the metal wire (151) and the metal braid (153).

[0126]

[0127] [Example]

[0128]

[0129] 1. Preparation Example

[0130] A shielding layer (15) was formed by reflecting the outer diameter (d1) of the metal wire (151) listed in Table 1 below, the outer diameter (d2) of the wire (153') constituting the metal braid (153), and the thickness (t) of the metal braid (153).

[0131] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Metal wire outer diameter (mm) 0.8 1.2 20.6 2.2 1.2 1.2 1.2 Braised wire outer diameter (mm) 0.1 6 0.1 80.2 5 40.1 60.1 60.1 0.3 10.1 60.1 Braised thickness (mm) 0.8 1.0 1.5 1.0 1.0 1.0 1.0 30.0 4

[0132] 2. Physical properties and appearance. The metal wire (151) and metal braid (153) of the shielding layer (15) manufactured according to each example and comparative example were evaluated for whether they were broken, elongated, or had protrusions formed, and are shown in Table 2 below.

[0133] The evaluation of the breakage of the metal wire (151) and the metal braid (153) was performed by conducting a tensile-bending fatigue test of at least 1.5 million times on the finished submarine cable product including the shielding layer (15) according to each embodiment and comparative example using a Full-scale Fatigue device, and then taking out the shielding layer (15) inside the submarine cable to visually inspect its appearance. If a breakage occurred in the wire (153') of the metal wire (151) or the metal braid (153), it was evaluated as '○', and if no breakage occurred, it was evaluated as 'X'.

[0134] The elongation of the shielding layer (15) was evaluated by fixing one end of the metal braid (153), pulling the other end at 10 kgh for 10 minutes, and then measuring the ratio of the increased length to the original length (elongation).

[0135] The protrusion generation evaluation was performed by visually checking whether a protrusion was generated on the surface of the sheath layer (16) due to the shielding layer (15) after extruding the sheath layer (16) on the outside of the shielding layer (15). If a protrusion was clearly formed or easily identifiable on the surface of the sheath layer (16), it was evaluated as ‘○’, and if no protrusion was formed or the size was very small and difficult to identify, it was evaluated as ‘X’.

[0136] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Metal wire breakage status XXX○XXXXX Metal braid wire breakage status XXXX○○XX○ Metal braid elongation (%) ≥ 20 ≥ 20 ≥ 20 ≥ 20 ≥ 20 ≤ 10 10~20 ≥ 20 Formation of sheath layer surface protrusion XXXXXXX○X

[0137] Referring to Tables 1 and 2, in Examples 1 to 3, as the outer diameter (d1) of the metal wire (151), the outer diameter (d2) of the wire of the metal braid (153), and the thickness (t) of the metal braid (153) satisfy the scope of the present invention, no breakage occurred in the metal wire (151) and the metal braid (153), the elongation of the metal braid (153) was 20% or more, and no protrusions were formed on the surface of the sheath layer (16). Meanwhile, to prevent deformation such as the gap between adjacent metal wires (151) under the Minimum Bending Radius (MBR) of the submarine cable, it is preferable that the elongation of the metal braid (153) transversely wound on the outside of the metal wire (151) be 20% or more. In Examples 1 to 3, the elongation of the metal braid (153) was all measured to be 20% or more, so regarding cable deformation It can be confirmed that the structural stability of the shielding layer (15) can be maintained.

[0138] On the other hand, in Comparative Example 1, it was confirmed that the outer diameter (d1) of the metal wire (151) was less than four times the outer diameter (d2) of the wire (153') constituting the metal braid (153), so a break occurred in the metal wire (151). In Comparative Example 2, it was confirmed that the outer diameter (d1) of the metal wire (151) exceeded eleven times the outer diameter (d2) of the wire (153') constituting the metal braid (153), so a break occurred in the wire (153') of the metal braid (153). In Comparative Example 3, it was confirmed that the outer diameter (d2) of the wire (153') constituting the metal braid (153) was less than 1 / 11.5 times the outer diameter (d1) of the metal wire (151), so a break occurred in the wire (153') of the metal braid (153). In Comparative Example 4, it was confirmed that the elongation characteristics of the metal braid (153) were significantly degraded because the outer diameter (d2) of the wire (153') constituting the metal braid (153) exceeded 1 / 4 times. In Comparative Example 5, it was confirmed that the elongation characteristics were degraded because the thickness (t) of the metal braid (153) exceeded 10 times the outer diameter (d2) of the wire (153') constituting the metal braid (153), and a protrusion was formed on the surface of the sheath layer (16). In Comparative Example 6, it was confirmed that the thickness (t) of the braid was less than 3.5 times the outer diameter (d2) of the wire (153') constituting the metal braid (153), causing a break in the wire (153') of the metal braid (153).

[0139] FIG. 6 shows a photograph of the exterior of a metal braid according to an embodiment, and FIG. 7 shows a photograph of the exterior of a metal braid according to a comparative example.

[0140] FIG. 6 shows the appearance of a metal braid (153) of an embodiment in which the outer diameter (d1) of the metal wire (151), the outer diameter (d2) of the strand of the metal braid (153), and the thickness (t) of the metal braid (153) satisfy the scope of the present invention. Referring to FIG. 6, some strands (153') of the metal braid (153) placed on the metal wire (151) may be plastically deformed by contact and friction with the metal wire (151). For example, some wires (153') of a metal braid (153) placed on a metal wire (151) may undergo plastic deformation due to continuous contact and friction with the metal wire (151) during the process of forming a sheath layer (16) on the outside, the manufacturing process of the submarine cable (100), the winding process of the submarine cable (100), the laying process of the submarine cable (100), and the bending or bending process after laying the submarine cable (100). However, when the outer diameter (d1) of the metal wire (151), the outer diameter (d2) of the wire of the metal braid (153), and the thickness (t) of the metal braid (153) satisfy the scope of the present invention, there was an area (A) where plastic deformation occurred in some wires (153') of the metal braid (153), but no breakage of the wire (153') occurred.

[0141] Meanwhile, FIG. 7 shows the appearance of a metal braid (153) of a comparative example in which the outer diameter (d1) of the metal wire (151), the outer diameter (d2) of the wire of the metal braid (153), and the thickness (t) of the metal braid (153) fall outside the scope of the present invention. Referring to FIG. 7, when the outer diameter (d2) of the wire of the metal braid (153) and the thickness (t) of the metal braid (153) do not satisfy the scope of the present invention, it can be seen that there is not only an area (A) in which plastic deformation occurred in some wires (153') of the metal braid (153), but also an area (B) in which a break occurred in the wire (153') constituting the metal braid (153). If a break occurs in a wire (153') constituting a metal braid (153), the cross-section of the broken wire faces inward toward the power unit (10), thereby damaging the outer semiconducting layer (14) and reducing the insulation strength of the power unit (10).

[0142] 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 submarine cable comprising at least one power unit, The power unit comprises 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, a shielding layer provided on the outer side of the outer semiconducting layer, and a sheath layer surrounding the shielding layer. The shielding layer comprises a plurality of metal wires that are spaced apart from the outer side of the outer semiconducting layer and are spirally wound, and a metal braided body that is wound on the outer side of the plurality of metal wires. The above metal braid is composed of wire bundles made of a plurality of wires braided together, and The outer diameter of the metal wire is 4 to 11.5 times the outer diameter of the wire constituting the metal braid, and A submarine cable characterized in that the thickness of the metal braid is 3.5 to 10 times the outer diameter of the wire constituting the metal braid.

2. In Paragraph 1, A submarine cable characterized by the outer diameter of the metal wire being 0.8 millimeters to 2.0 millimeters (mm).

3. In Paragraph 1, A submarine cable characterized in that the outer diameter of the wire constituting the metal braid is 0.16 millimeters to 0.254 millimeters (mm).

4. In Paragraph 1, A submarine cable characterized in that the metal braid has a flat strap shape in which the width of the cross-section is greater than the thickness, and the thickness of the metal braid is 0.5 to 2 times the outer diameter of the metal wire.

5. In Paragraph 4, A submarine cable characterized by the thickness of the metal braiding body being 0.8 millimeters to 1.5 millimeters (mm).

6. In Paragraph 1, A submarine cable characterized in that the metal wire and the metal braid are transversely wound in the same spiral direction.

7. In Paragraph 1, A submarine cable characterized in that the metal wire and the metal braid are wound transversely in different directions.

8. In Paragraph 1, A submarine cable characterized in that the transverse winding pitch of the metal braid is smaller than the transverse winding pitch of the metal wire.

9. In Paragraph 1, A submarine cable characterized in that the transverse winding pitch of the metal braid is greater than the transverse winding width of the metal braid.

10. In Paragraph 1, A submarine cable characterized in that the sheath layer is made of a polymer resin, and the thickness of the sheath layer is 1.5 to 10 times the outer diameter of the metal wire.

11. In Paragraph 1, A submarine cable characterized in that some of the wires of the metal braiding structure disposed on the metal wire are plastically deformed by contact and friction with the metal wire.

12. In Paragraph 1, The above submarine cable is Multiple of the above power units; A plurality of shape fillers disposed between the power units and accommodating the power units while spaced apart from each other, and together with the power units, forming a circular shape on their outer surfaces; At least one optical unit having an optical fiber, which is accommodated in at least one of a plurality of shape fillers; 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 having a plurality of armor wires arranged transversely and wound on the outer side of the above bedding layer; and A submarine cable comprising: an outermost layer provided on the outer side of the above armor layer.

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