Patent Description:
Flexible direct-current submarine cable is generally suitable for large-capacity and long-distance transmission projects, which requires a conductor with a large cross-sectional area. Due to limitations of the number of reels of a framed stranding machine and requirements of diameter of single wire, and a small filling coefficient of single wire conductor with a circular cross-section, the conductor with the circular cross-sectional has a small cross-sectional area, and furthermore, a segment conductor has a poor performance of water-blocking. Therefore, conductors of a high-voltage flexible direct-current cable are mostly special-shaped single wire conductors.

An existing flexible direct-current submarine cable generally includes a water-blocking conductor; an optical fiber unit; and a conductor shielding layer, an insulating layer, an insulating shielding layer, a water-blocking layer, a metal protective layer, an inner protective layer and an optical fiber protective layer and other layer, which are wrapped around an outer side of the water-blocking conductor, where the optical fiber unit is arranged in the optical fiber protective layer, and the water-blocking conductor is a special-shaped single wire conductor, and cross-sections of the single wire are mostly "S (Z)" shaped or trapezoidal.

Therefore, the structure of the above flexible direct-current submarine cable will lead to the increase of the outer diameter of the submarine cable and increase of the processing cost of the submarine cable. Moreover, since the optical fiber unit is close to the outermost layer of the submarine cable, the optical fiber unit is more susceptible to force, resulting in waveform abnormality or even interruption. In addition, the conductor single wire in the above submarine cable uses a single wire with a "S (Z)" shaped or trapezoidal cross section, but production speed of the single wire with the "S (Z)" shaped cross section is relatively slow, which will reduce production efficiency of the submarine cable, and the single wire with the trapezoidal cross section is easy to turn over in the production process, affecting the performance of water-blocking of the submarine cable. The prior art document <CIT> discloses a submarine cable with a core comprising an optical fibre cable. The core comprises a metallic, longitudinal strength member matrix in which a plurality of optical fibres are housed in internal, hermetically-isolated longitudinal passages which are disposed equi-radially in a peripheral region of the matrix.

Embodiments of the present application provide a flexible direct-current submarine cable, which has advantages of low production cost, high production efficiency and good performance of water-blocking.

The present application provides a flexible direct-current submarine cable, including a water-blocking conductor and an optical fiber assembly, where the water-blocking conductor wraps around an outer side of the optical fiber assembly along a circumferential direction of the optical fiber assembly; the water-blocking conductor includes a conductor core wrapped around the outer side of the optical fiber assembly, the conductor core includes at least two conductor layers including a first conductor layer and a second conductor layer, the first conductor layer and the second conductor layer are alternately provided along a radial direction of the optical fiber assembly, the first conductor layer is formed by stranding a plurality of first metal wires arranged along a circumferential direction of the optical fiber assembly, the second conductor layer is formed by stranding a plurality of second metal wires arranged along the circumferential direction of the optical fiber assembly; the first metal wires each have a concave part and a convex part arranged sequentially in the radial direction of the optical fiber assembly, and both a concave direction of the concave part and a convex direction of the convex part are along the circumferential direction of the optical fiber assembly, and the convex part of one of two adjacent first metal wires is stuck into the concave part of the other; the second metal wires each have two straight side wall surfaces that are opposite to each other, the straight side wall surfaces extend along the radial direction of the optical fiber assembly, and the straight side wall surfaces of two adjacent second metal wires fit each other.

Optionally, in the flexible direct-current submarine cable provided in the present application, projection positions of the first metal wires and the second metal wires in a radial direction of the flexible direct-current submarine cable are staggered with each other, in adjacent first and second conductor layers.

Optionally, in the flexible direct-current submarine cable provided in the present application, the first metal wires in adjacent first and second conductor layers are pressed against at least two adjacent second metal wires,; or, the second metal wires in adjacent first and second conductor layers are pressed against at least two adjacent first metal wires.

Optionally, in the flexible direct-current submarine cable provided in the present application, stranding directions of adjacent first and second conductor layers are opposite.

Optionally, in the flexible direct-current submarine cable provided in the present application, in the at least two conductor layers, both a conductor layer in contact with the optical fiber assembly and a conductor layer located on a surface of the conductor core are the first conductor layer.

Optionally, in the flexible direct-current submarine cable provided in the present application, the conductor core further includes a third conductor layer that is a single-layer or a multi-layer, the third conductor layer is formed by stranding a plurality of third metal wires, and a cross section of the third metal wires in the radial direction of the flexible direct-current submarine cable is circular.

Optionally, in the flexible direct-current submarine cable provided in the present application, the first metal wires in each first conductor layer are of the same shape and equal size, and the second metal wires in each second conductor layer are of the same shape and equal size.

Optionally, in the flexible direct-current submarine cable provided in the present application, the concave part is a concave arc segment and the convex part is a convex arc segment; or the concave part has a first extension segment extending in the radial direction of the flexible direct-current submarine cable, the convex part has a second extension segment extending in the radial direction of the flexible direct-current submarine cable, and the first extension segment and the second extension segment are parallel to each other.

Optionally, in the flexible direct-current submarine cable provided in the present application, the first extension segment of the concave part is parallel to the second extension segment of the convex part; the first metal wires further comprise a transition segment connected between the first extension segment and the second extension segment, and an extension direction of the transition segment is perpendicular to an extension direction of the first extension segment.

Optionally, in the flexible direct-current submarine cable provided in the present application, the optical fiber assembly includes an optical fiber unit, the optical fiber unit includes a plurality of optical fibers, a first water-blocking filling unit and a first metal tube, the plurality of optical fibers are located in the first metal tube, the first water-blocking filling unit is filled between the plurality of optical fibers and the first metal tube, and the optical fibers are not in contact with the first metal tube.

Optionally, in the flexible direct-current submarine cable provided in the present application, there are a plurality of optical fiber units, the plurality of optical fiber units each include a first optical fiber unit located in a center of the water-blocking conductor and a plurality of second optical fiber units uniformly wrapped around a periphery of the first optical fiber unit, a center of the first optical fiber unit coincides with a center of the optical fiber assembly, the second optical fiber units abut against the first optical fiber unit, and two adjacent second optical fiber units abut against each other.

Optionally, in the flexible direct-current submarine cable provided in the present application, the optical fiber assembly further includes a plurality of filling units, a second metal tube and a second water-blocking filling unit; the filling units are arranged corresponding to the second optical fiber units, and the filling units are located between adjacent second optical fiber units, the second metal tube is wrapped around outer sides of the plurality of filling units and of the optical fiber unit, and the filling units and the second optical fiber units each abut against an inner wall of the second metal tube; the second water-blocking filling unit is filled between the plurality of optical fiber units, the plurality of filling units and the second metal tube.

Optionally, in the flexible direct-current submarine cable provided in the present application, the optical fiber assembly further includes a first water-blocking wrapping tape located inside the second metal tube.

Optionally, in the flexible direct-current submarine cable provided in the present application, the water-blocking conductor further includes a second water-blocking wrapping tape wrapped around an outer side of the conductor core.

Optionally, in the flexible direct-current submarine cable provided in the present application, the water-blocking conductor further includes a protective layer wrapped around an outer side of the second water-blocking wrapping tape layer, and the protective layer is peelably arranged on the outer side of the second water-blocking wrapping tape layer.

The flexible direct-current submarine cable provided in the present application includes a water-blocking conductor and an optical fiber assembly, the water-blocking conductor includes a conductor core wrapped around an outer side of the optical fiber assembly, the conductor core includes at least two conductor layers including a first conductor layer and a second conductor layer, the first conductor layer and the second conductor layer are alternately provided along a radial direction of the optical fiber assembly, the first conductor layer is formed by stranding a plurality of first metal wires arranged along a circumferential direction of the optical fiber assembly, the second conductor layer is formed by stranding a plurality of second metal wires arranged along the circumferential direction of the optical fiber assembly; the first metal wires each have a concave part and a convex part arranged sequentially in the radial direction of the optical fiber assembly, and a concave direction of the concave part and a convex direction of the convex part are along a circumferential direction of the optical fiber assembly, and the convex part of one of two adjacent first metal wires is stuck into the concave part of the other; the second metal wires each have two straight side wall surfaces that are opposite, the straight side wall surfaces extend along the radial direction of the optical fiber assembly, and the straight side wall surfaces of two adjacent second metal wires fit each other. The flexible direct-current submarine cable in the present application has advantages of low production cost, high production efficiency and good performance of water-blocking.

The structure, other application purposes and beneficial effects of the present application will be obvious by the description of the preferred embodiments with reference to the drawings.

In order to illustrate the technical solutions of embodiments of the present application or prior art more clearly, the drawings that need to be used in the embodiments will be briefly introduced hereunder. It is obvious that the drawings described below only show certain embodiments of the present application, and for those ordinarily skilled in the art, other relevant drawings also can be obtained according to these drawings without any creative work.

Illustration of reference signs of the accompanying drawings:.

In order to make the purpose, technical solution and advantages of the embodiments of the present application more clear, the technical solution in the embodiment of the present application will be described clearly and completely in combination with the accompanying drawings in the embodiments of the present application. Obviously, the embodiments described are some embodiments of the present application, but not all embodiments.

Based on the embodiments in the present application, all other embodiments obtained by those skilled in the field without creative work fall within the protection scope of the present application. The following embodiments and the features in the embodiments may be combined with each other without conflict.

In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "above", "below", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial" and "circumferential" are based on the orientations or position relationships shown in the accompanying drawings, and are only intended to facilitate the description of the present application and to simplify the description, rather than indicating or implying that the device or element referred to must have a specific orientation, constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application.

In the present application, unless otherwise clearly specified and defined, the terms "installation", "junction", "connection" and "fixed" shall be understood in a broad sense, for example, they can be a fixed connection, a detachable connection, or an integrated connection; they can be directly connected, or indirectly connected through an intermediate medium, or they can be the internal connection of two elements or the interaction between two elements. For those skilled in the field, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

It should be stated that in the description of the present application, the terms "first" and "second" are only used to facilitate the description of different components, it cannot be understood to indicate or imply sequential relations, relative importance or implicitly indicate the number of indicated technical features. Thus, a feature defined with "first" and "second" may include at least one such feature either expressly or implicitly.

An existing flexible direct-current submarine cable generally includes a water-blocking conductor; an optical fiber unit; and a conductor shielding layer, an insulating layer, an insulating shielding layer, a water-blocking layer, a metal protective layer, an inner protective layer and an optical fiber protective layer and other layer, which are covered on outer side of the water-blocking conductor; where the optical fiber unit is arranged in the optical fiber protective layer, the water-blocking conductor is a special-shaped single wire conductor, and cross-sections of the single wire mostly are "S (Z)" shaped or trapezoidal.

Therefore, the structure of the above flexible direct-current submarine cable will lead to increase of the outer diameter of the submarine cable and increase of the processing cost of the submarine cable. Moreover, since the optical fiber unit is close to the outermost layer of the submarine cable, the optical fiber unit is more susceptible to force, resulting in waveform abnormality or even interruption. In addition, the conductor single wire in the existing submarine cable is a single wire with a "S (Z)" shaped or trapezoidal cross section, but a production speed of the single wire with the "S (Z)" shaped cross section is relatively slow, which will reduce production efficiency of the submarine cable, and the single wire with the trapezoidal cross section is easy to turn over during the production process, affecting the performance of water-blocking of the submarine cable.

Therefore, the present application provides a flexible direct-current submarine cable, where the optical fiber unit is arranged inside the water-blocking conductor to avoid that the water-blocking conductor and the optical fiber unit are arranged separately, thereby reducing the processing cost of the submarine cable. Besides, the optical fiber unit is arranged inside the water-blocking conductor, which can reduce the force on the optical fiber unit and prevent the interruption of the optical fiber unit. In addition, the water-blocking conductor in the present application combines a conductor layer formed by stranded "S (Z)" shaped metal wires with a conductor layer formed by stranded trapezoidal metal wires, which not only solves the problem the metal wire with the "S (Z)" shaped cross section alone has a slow production speed, but also solves the problem that the metal wire with the trapezoidal cross section alone is easy to turn over, and thus not only can improve the production efficiency of the submarine cable, but also can ensure that the submarine cable has a good performance of water-blocking.

The following is a detailed description of the present application in combination with the accompanying drawings and specific embodiments.

<FIG> is a schematic structural diagram of a flexible direct-current submarine cable provided by an embodiment of the present application.

As shown in <FIG>, the present application provides a flexible direct-current submarine cable, including a water-blocking conductor <NUM>, an optical fiber assembly <NUM>, a conductor shielding layer <NUM>, an insulating layer <NUM>, an insulating shielding layer <NUM>, a water-blocking layer <NUM>, a metal protective layer <NUM>, an outer protective layer <NUM>, an inner lining layer <NUM>, an armor layer <NUM>, and an outer serving layer <NUM>, where the conductor shielding layer <NUM>, the insulating layer <NUM>, the insulating shielding layer <NUM>, the water-blocking layer <NUM>, the metal protective layer <NUM>, the outer protective layer <NUM>, the inner lining layer <NUM>, the armor layer <NUM>, and the outer serving layer <NUM> are sequentially coated on the outer side of the water-blocking conductor <NUM>. In order to reduce the processing cost of the submarine cable provided in the present application and to prevent the interruption of the optical fiber assembly <NUM>, in the specific implementation modes of the embodiments of the present application, the water-blocking conductor <NUM> wraps outer side of the optical fiber assembly <NUM> along a circumferential direction of the optical fiber assembly <NUM>, and centers of the optical fiber assembly <NUM> and the water-blocking conductor <NUM> coincide with the center of the submarine cable. Setting the optical fiber assembly <NUM> inside the water-blocking conductor <NUM>, compared with setting the optical fiber assembly <NUM> on an outer layer structure the water blocking conductor <NUM>, can avoid further molding of the outer structure to form an accommodation space for accommodating the optical fiber assembly <NUM>, and thus reduce the processing cost of the submarine cable; in addition, when the optical fiber assembly <NUM> is located inside the water blocking conductor <NUM>, the force acting on the optical fiber assembly <NUM> in the radial direction of the submarine cable is small, which can prevent the interruption of the optical fiber assembly <NUM>.

It should be stated that the above insulating layer <NUM> may be a cross-linked polyethylene (Cross linked polyethylene, CLPE) insulating layer; the water-blocking layer <NUM> may be a semi-conductive water-blocking tape, and the semi-conductive water-blocking tape may be compounded of a semi-conductive nonwoven and a water-absorbent resin; the metal protective layer <NUM> may be made of plumbum or other alloy; and the outer protective layer <NUM> may be a polyethylene (polyethylene, PE) protective layer; the inner lining layer <NUM> may be a polypropylene (polypropylene, PP) inner lining layer; the armor layer <NUM> may include a plurality of steel wires that stranded together and with a circular cross-section in a radial direction of the submarine cable, and asphalt filled between the plurality of steel wires; the outer serving layer <NUM> may be a PP outer serving layer; here, there is no specific restriction on other type of material of the layer structure wrapped outside the water-blocking conductor <NUM>.

<FIG> is a first schematic structural diagram of the optical fiber assembly in the flexible direct-current submarine cable provided by an embodiment of the present application. <FIG> is a second schematic structural diagram of the optical fiber assembly in the flexible direct-current submarine cable provided by an embodiment of the present application.

As shown in <FIG>, in some specific implementation modes, the optical fiber assembly <NUM> includes an optical fiber unit <NUM>, the optical fiber unit <NUM> includes a plurality of optical fibers <NUM>, a first water-blocking filling unit <NUM> and a first metal tube <NUM>. The plurality of optical fibers <NUM> are located inside the first metal tube <NUM>. Here, there is no specific restriction on the arrangement of the plurality of optical fibers <NUM> in the first metal tube <NUM>. The first water-blocking filling unit <NUM> is filled between the plurality of optical fibers <NUM> and the first metal tube <NUM>, and the optical fibers <NUM> and the first metal tube <NUM> are not in contact with each other.

Further, the above optical fibers <NUM> are made of glass or plastic, the above first water-blocking filling unit <NUM> may be a water-blocking grease, such as asphalt water-blocking grease, and the above first metal tube <NUM> may be a copper tube; here, other types and materials of the optical fibers <NUM>, the first water-blocking filling unit <NUM> and the first metal tube <NUM> are not specifically limited.

It should be stated that in the actual production process, according to different structures of the submarine cable itself, the optical fiber assembly <NUM> may include different numbers of optical fibers <NUM>, and when the number of optical fibers <NUM> is less than or equal to a preset number, the optical fiber assembly <NUM> includes an optical fiber unit <NUM>, and when the number of optical fibers <NUM> is greater than the preset number, the optical fiber assembly <NUM> may include a plurality of optical fiber units <NUM>. The following is a specific introduction of the optical fiber assembly <NUM> with different numbers of optical fibers <NUM>.

As shown in <FIG>, when the number of optical fibers <NUM> is less than or equal to the preset number, the optical fiber assembly <NUM> includes one optical fiber unit <NUM>, and at this time, the center of the optical fiber unit <NUM> is the center of the optical fiber assembly <NUM> and also the center of the water-blocking conductor <NUM>.

As shown in <FIG>, when the number of optical fibers <NUM> is greater than the preset number, there are a plurality of optical fiber units <NUM>, and at this time, the plurality of optical fiber units <NUM> include a first optical fiber unit 21a located in the center of the water-blocking conductor <NUM> and a plurality of second optical fiber units 21b uniformly wound around the periphery of the first optical fiber unit 21a. The center of the first optical fiber unit 21a coincides with the center of the water-blocking conductor <NUM> and the center of the optical fiber assembly <NUM>. The second optical fiber units 21b abut against the first optical fiber unit 21a, and two adjacent second optical fiber units 21b are abutted against each other.

In a specific implementation mode of the present embodiment, the preset number of optical fibers <NUM> may be <NUM>, that is, when the total number of optical fibers <NUM> is less than or equal to <NUM>, the optical fiber assembly <NUM> includes one optical fiber unit <NUM>; when the total number of optical fibers <NUM> is greater than <NUM>, the optical fiber assembly <NUM> includes a plurality of optical fiber units <NUM>.

As shown in <FIG>, when the total number of optical fibers <NUM> is greater than <NUM>, the optical fiber assembly <NUM> further includes a plurality of filling units <NUM>, a second metal tube <NUM> and a second water-blocking filling unit <NUM>, where the filling units <NUM> are arranged corresponding to the second optical fiber units 21b, and the filling unit <NUM> are located between adjacent second optical fiber units 21b, and the second metal tube <NUM> is wrapped around the outer sides of the plurality of filling units <NUM> and the optical fiber units <NUM>, and the filling units <NUM> and the second optical fiber units 21b each abut against the inner wall of the second metal tube <NUM>; the second water-blocking filling unit is filled between the plurality of optical fiber units <NUM>, the plurality of filling units <NUM> and the second metal tube <NUM>.

It should be stated that the above filling units <NUM> may be stranded from steel wires, the above second metal tube <NUM> is a copper tube, and the second water-blocking filling unit <NUM> may also be a water-blocking grease, such as asphalt water-blocking grease; here, there is no specific restriction on other materials or types of the filling units <NUM>, the second metal tube <NUM> and the second water-blocking filling unit <NUM>.

<FIG> is a third schematic structural diagram of the optical fiber assembly in the flexible direct-current submarine cable provided by an embodiment of the present application.

As shown in <FIG>, in order to improve the longitudinal water-blocking performance of the optical fiber assembly <NUM>, that is, to improve the performance of water-blocking of the optical fiber assembly <NUM> in the radial direction of the submarine cable, in some optional implementation modes, the optical fiber assembly <NUM> further includes a first water-blocking wrapping tape <NUM>, which is located inside the second metal tube <NUM>.

<FIG> is a first schematic structural diagram of a combination of the water-blocking conductor and the optical fiber assembly in the flexible direct-current submarine cable provided by an embodiment of the present application. <FIG> is a second schematic structural diagram of a combination of the water-blocking conductor and the optical fiber assembly in the flexible direct-current submarine cable provided by an embodiment of the present application. <FIG> is a third schematic structural diagram of a combination of the water-blocking conductor and the optical fiber assembly in the flexible direct-current submarine cable provided by an embodiment of the present application. <FIG> is a schematic structural diagram of a second metal wire in the flexible direct-current submarine cable provided by an embodiment of the present application.

As shown in <FIG>, in order to improve the production efficiency of the flexible direct-current submarine cable and ensure that the flexible direct-current submarine cable has better performance of water-blocking, in a specific implementation mode of the present application, the water-blocking conductor <NUM> includes a conductor core <NUM> wrapping around outer side of the optical fiber assembly <NUM>, and the conductor core <NUM> includes at least two conductor layers <NUM>, the at least two conductor layers <NUM> include a first conductor layer 111a and a second conductor layer 111b. The first conductor layer 111a and the second conductor layer 111b are alternately provided along a radial direction of the optical fiber assembly <NUM>, the first conductor layer 111a is formed by stranding a plurality of first metal wires <NUM> arranged along a circumferential direction of the optical fiber assembly <NUM>, the second conductor layer 111b is formed by stranding a plurality of second metal wires <NUM> arranged along the circumferential direction of the optical fiber assembly <NUM>; the first metal wire <NUM> has a concave part <NUM> and a convex part <NUM> arranged sequentially in the radial direction of the optical fiber assembly <NUM>, and concave direction of the concave part <NUM> and convex direction of the convex part <NUM> are along the circumferential direction of the optical fiber assembly <NUM>, and the convex part <NUM> of one of two adjacent first metal wires <NUM> is stuck into the concave part <NUM> of the other; the second metal wire <NUM> has two opposite straight side wall surfaces <NUM>, the straight side wall surfaces <NUM> extend along the radial direction of the optical fiber assembly <NUM>, and the straight side wall surfaces <NUM> of two adjacent second metal wires <NUM> fit each other. In the flexible direct-current submarine cable provided by the embodiment of the present application, alternately combining the first conductor layer 111a formed by stranding a plurality of first metal wires <NUM> and the second conductor layer 111b formed by stranding a plurality of second metal wires <NUM> not only can improve the production efficiency of the submarine cable, but also can ensure that the submarine cable has a good performance of water-blocking.

In a specific implementation mode of the present embodiment, the second metal wire <NUM> further has two opposite curved side walls <NUM>, where the length of the curved side walls <NUM> near the center of the submarine cable in the circumferential direction of the submarine cable is less than that of the curved side walls <NUM> away from the center of the submarine cable in the circumferential direction of the submarine cable.

It should be stated that in a specific implementation mode of the present embodiment, in order to improve the performance of longitudinal water-blocking of the submarine cable, a water-blocking glue is filled between the water-blocking conductor <NUM> and the optical fiber assembly <NUM>, and the water-blocking glue is also filled between adjacent conductor layers <NUM>.

In a specific implementation mode of the present embodiment, among at least two conductor layers <NUM>, the conductor layer <NUM> in contact with the optical fiber unit <NUM> and the conductor layer <NUM> located on the surface of the conductor core <NUM> are both the first conductor layers 111a.

In order to facilitate the processing of the first metal wire <NUM> and the second metal wire <NUM>, and to facilitate the stranding of a plurality of first metal wires <NUM> and a plurality of second metal wires <NUM>, in a specific implementation mode of the present embodiment, the first metal wires <NUM> in each first conductor layer 111a each have the same shape and size, and the second metal wires <NUM> in each second conductor layer 111b each have the same shape and size; that is, the number of the first metal wires <NUM> in the first conductor layer 111a near the center of the submarine cable is less than that of the first metal wires <NUM> in the first conductor layer 111a away from the center of the submarine cable, and the number of the second metal wires <NUM> in the second conductor layer 111b near the center of the submarine cable is less than that of the second metal wires <NUM> in the second conductor layer 111b away from the center of the submarine cable.

Further, in order to facilitate the processing of the first metal wires <NUM> and the second metal wires <NUM>, a transition connection is used at the connections of segments of the first metal wires <NUM> and the second metal wires <NUM>, so that it is not only convenient for processing, but also convenient to fill a water-blocking glue between the first conductor layer 111a and the second conductor layer 111b.

It should be stated that in a specific implementation process, the number of the first metal wires <NUM> included in the first conductor layer 111a and the number of the second metal wires <NUM> included in the second conductor layer 111b can be selected according to a specific stranding device and the performance of the submarine cable. As an example, as shown in <FIG>, the conductor core <NUM> includes four conductor layers <NUM>, including two first conductor layers 111a and two second conductor layers 111b, the number of the first metal wires <NUM> in the first conductor layer 111a near the center of the submarine cable may be less than or equal to <NUM>, and the number of the second metal wires <NUM> in the second conductor layer 111b near the center of the submarine cable may be less than or equal to <NUM>, and the number of the first metal wires <NUM> in the first conductor layer 111a away from the center of the submarine cable may be less than or equal to <NUM>, and the number of the second metal wires <NUM> in the second conductor layer 111b away from the center of the submarine cable may be less than or equal to <NUM>.

In order to ensure that the second metal wires <NUM> is not easily turned over during stranding, in some optional implementation modes, in adjacent first and second conductor layers 111a, 111b, projection positions of the first metal wires <NUM> and the second metal wires <NUM> in a radial direction of the flexible direct-current submarine cable are staggered with each other, that is to say, in adjacent first and second conductor layers 111a, 111b, the first metal wires <NUM> are pressed against at least two adjacent second metal wires <NUM>; or, in adjacent first and second conductor layers 111a, 111b, the second metal wires <NUM> are pressed against at least two adjacent first metal wires <NUM>. In this way, it is possible to prevent the edges of the first metal wires <NUM> in the circumferential direction of the submarine cable from coinciding with the edges of the second metal wires <NUM> in the circumferential direction of the submarine cable, ensuring that the second metal wires <NUM> do not turn over easily; it should be stated that the above "turn over" can be understood as a <NUM>° rotation of the second metal wires <NUM>.

In order to prevent an outer conductor layer <NUM> from falling into a gap of an inner conductor layer <NUM> during the stranding process, in a specific implementation mode of the present embodiment, stranding directions of adjacent first and second conductor layers 111a, 111b are opposite, thus ensuring the flatness of the surface of the submarine cable so as to meet the standard requirements.

<FIG> is a schematic structural diagram of the first metal wire in the flexible direct-current submarine cable provided by an embodiment of the present application. <FIG> is a fourth schematic structural diagram of a combination of the water-blocking conductor and the optical fiber assembly in the flexible direct-current submarine cable provided by an embodiment of the present application.

As shown in <FIG>, in order to avoid a small size of the first metal wires <NUM> or the second metal wires <NUM>, which is not conducive to processing, in some optional implementation modes, the conductor core <NUM> further includes a third conductor layer 111c, the third conductor layer 111c is a single-layer or a multi-layer, the third conductor layer 111c is formed by stranding a plurality of third metal wires <NUM>, and the shapes of the cross sections of the third metal wires <NUM> in the radial direction of the flexible direct-current submarine cable are circular. In this way, by setting the third conductor layer 111c formed by stranding a plurality of third metal wires <NUM> with circular cross sections, the defect that it is not convenient to process and shape the first metal wire <NUM> or the second metal wire <NUM> can be overcome.

As shown in <FIG> and <FIG>, in some optional implementation modes, the concave part <NUM> is a concave arc segment and the convex part <NUM> is a convex arc segment, so that the cross section of the first metal wire <NUM> in the radial direction of the submarine cable is in "S" shape.

In other optional implementation modes, as shown in <FIG>, <FIG> and <FIG>, the concave part <NUM> has a first extension segment <NUM> extending in a radial direction of the flexible direct-current submarine cable, the convex part <NUM> has a second extension segment <NUM> extending in the radial direction of the flexible direct-current submarine cable, and the first extension segment <NUM> and the second extension segment <NUM> are parallel to each other. Further, the first metal wire <NUM> further includes a transition segment <NUM> connected between the first extension segment <NUM> and the second extension segment <NUM>, and an extension direction of the transition segment <NUM> is perpendicular to an extension direction of the first extension segment <NUM>.

<FIG> is a fifth schematic structural diagram of a combination of the water-blocking conductor and the optical fiber assembly in the flexible direct-current submarine cable provided by an embodiment of the present application.

As shown in <FIG>, in order to further enhance the water-blocking effect of the water-blocking conductor <NUM>, the water-blocking conductor <NUM> further includes a second water-blocking wrapping tape <NUM> wrapping around outer side of the conductor core <NUM>.

It should be stated that the above first water-blocking wrapping tape <NUM> and the above second water-blocking wrapping tape <NUM> are both formed by wrapping with a layer of semi-conductive water-blocking tape and a layer of semi-conductive binder tape, and an overlap rate of the semi-conductive water-blocking tape and semi-conductive binder tape is <NUM>%-<NUM>%. In order to further enhance the effect of water-blocking of the first water-blocking wrapping tape <NUM> and the second water-blocking wrapping tape <NUM>, the semi-conductive water-blocking tape and the semi-conductive binder tape should be staggered at the overlap regions. Here, there is no specific restriction on the structure and forming mode of the first water-blocking wrapping tape <NUM> and the second water-blocking wrapping tape <NUM>.

In order to ensure that the water-blocking conductor <NUM> is not damaged after processing, the water-blocking conductor <NUM> further includes a protective layer <NUM> wrapping around the outer side of the second water-blocking wrapping tape <NUM>, and the protective layer <NUM> is peelably arranged outside the second water-blocking wrapping tape <NUM>. During the manufacture of the flexible direct-current submarine cable provided by the present embodiment, after the water-blocking conductor <NUM> is formed, the protective layer <NUM> can be stripped off for further processing and molding.

It should be stated that the above protective layer <NUM> is formed by two layers of non-woven tapes by wrapping, and the overlap rate of each layer of the non-woven tapes is <NUM>%-<NUM>%. In order to enhance the effect of water-blocking of the protective layer <NUM>, the two layers of non-woven tapes should be staggered at the overlap regions. In addition, in order to successfully remove the protective layer <NUM> from the second water-blocking wrapping tape <NUM>, a wrapping direction of the protective layer <NUM> is opposite to that of the second water-blocking wrapping tape <NUM>.

Claim 1:
A flexible direct-current submarine cable, comprising a water-blocking conductor and an optical fiber assembly, wherein the water-blocking conductor is wrapped around an outer side of the optical fiber assembly along a circumferential direction;
the water-blocking conductor comprises a conductor core wrapped around the outer side of the optical fiber assembly, the conductor core comprises at least two conductor layers comprising a first conductor layer and a second conductor layer, the first conductor layer and the second conductor layer are alternately provided along a radial direction of the optical fiber assembly, the first conductor layer is formed by stranding a plurality of first metal wires arranged along the circumferential direction of the optical fiber assembly, the second conductor layer is formed by stranding a plurality of second metal wires arranged along the circumferential direction of the optical fiber assembly;
the first metal wires each have a concave part and a convex part arranged sequentially in the radial direction of the optical fiber assembly, and both a concave direction of the concave part and a convex direction of the convex part are along the circumferential direction of the optical fiber assembly, and the convex part of one of two adjacent first metal wires is stuck into the concave part of the other;
the second metal wires each have two straight side wall surfaces arranged opposite, the straight side wall surfaces extend along the radial direction of the optical fiber assembly, and the straight side wall surfaces of two adjacent second metal wires fit each other.