WO2018099191A1 - Direct-current submarine cable - Google Patents

Abstract

Disclosed is a direct-current submarine cable, comprising a hexagonal support core (1), wherein the edge length of the hexagonal support core (1) is 3.3 mm-3.7 mm; a first type wire layer (2) is arranged outside the hexagonal support core (1); the first type wire layer (2) comprises six first type single wires (2a); the six first type single wires (2a) are circular after being stranded with the support core (1); and the sectional area of each of the first type single wires (2a) is 28.50 mm2-29.5 mm2.

Description

DC submarine cable

Cross-reference to related applications

The present application is filed on the basis of the Chinese Patent Application No. 201611078251.7, filed on Nov. 29, 2016, the entire disclosure of which is hereby incorporated by reference.

Technical field

The invention relates to the technical field of submarine cables, and in particular to a direct current submarine cable.

Background technique

The global intelligent Internet is inseparable from high voltage, large capacity and communication transmission. Ultra-high voltage direct current transmission has low cost, low loss and no reactive power loss. And the grid connection is convenient, easy to control and adjust, has been widely used in long-distance transmission. HVDC transmission can make marine wind power, tidal power, solar power, etc. unstable, and the power supply and power system are connected without affecting the power quality level of the power grid. Therefore, it is necessary to use DC power transmission.

However, at present, the high-voltage DC submarine cable technology only stays in the oil-impregnated paper insulated oil-filled submarine cable. On the one hand, the oil-impregnated paper-insulated oil-filled submarine cable has poor water blocking effect, and the laying is limited by the drop; on the other hand, the submarine cable occurs. It is difficult to repair when leaking oil; on the other hand, corrosion resistance and tensile strength are poor, resulting in shortened cable life and increased cost.

Therefore, those skilled in the art are working to develop a DC submarine cable capable of effectively improving the water blocking effect.

Summary of the invention

In view of the above drawbacks of the prior art, embodiments of the present invention are expected to provide a DC submarine Cable can effectively improve the water blocking effect.

The technical solution of the embodiment of the present invention is implemented as follows:

In order to achieve the above object, an embodiment of the present invention provides a DC submarine cable, including a hexagonal support core, and a side length of the hexagonal support core is 3.3 mm - 3.7 mm;

The first type of line layer is provided on the outer side of the hexagonal support core, and the first type line layer comprises six first type line single lines, and the six first type line single lines and the support core are twisted and rounded, and each of the first type lines has a single line. cross-sectional area are 28.50mm ² -29.5mm ^2;

The outer side of the first type of line layer is provided with a second type of line layer, the second type of line layer comprises twelve second type line single lines, and the twelve second type line single lines are twisted and rounded with the first type of line layer , the cross-sectional area of each of the second type of single line is 8mm ² -10mm ² ;

The outer side of the second type line layer is provided with a third type line layer, the third type line layer comprises eighteen third type line single lines, and the eighteen third type line single lines and the second type line layer are twisted and rounded , the cross-sectional area of each third line single line is 6.5mm ² -8.5mm ² ;

The fourth type line layer is provided with a fourth type line layer, the fourth type line layer includes twenty-four fourth type line single lines, and twenty-four fourth type line single lines and the third type line layer are twisted and then Round, the cross-sectional area of each of the fourth type of single line is 5.5mm ² -7.5mm ² .

In order to further improve the water blocking performance, as an embodiment, the cross-sectional area of the first type of line layer is 200 mm ² -202 mm ² ; the cross-sectional area of the second type line layer is 313.2 mm ² -315.2 mm ² ; The cross-sectional area is 451.2 mm ² -453.2 mm ² ; the cross-sectional area of the fourth type of wire layer is 614.2 mm ² -616.2 mm ² .

In order to enhance the compactness of the structure, as an embodiment, the outer side of the fourth type line layer is provided with a fifth type line layer, and the fifth type line layer includes thirty fifth type line single lines, the fifth type line single line and the The four-type line layer is rounded after being twisted, and the cross-sectional area of each of the fifth type line single lines is 5.5 mm ² -7.5 mm ² ;

The sixth type line layer is provided with a sixth type line layer, and the sixth type line layer includes thirty-sixth sixth type line single lines, and the sixth type line single line and the fifth type line layer are twisted and rounded, each the sixth type of wire-line cross-sectional area are 6.8mm ² -8.2mm ^2.

In order to further enhance the compactness and improve the water blocking effect, as an embodiment, the cross-sectional area of the fifth type line layer is 803 mm ² -805 mm ² ; and the cross-sectional area of the sixth type line layer is 1074 mm ² -1076 mm ² .

As an embodiment, the outer side of the sixth type wire layer is provided with a semi-conductive shield; the outer side of the semi-conductive shield is provided with a cross-linked polyethylene insulating layer; and the outer side of the cross-linked polyethylene insulating layer is provided with an insulating shielding layer.

As an embodiment, a semi-conductive water buffer layer is disposed outside the insulating shielding layer; an alloy lead sleeve is disposed outside the semi-conductive water buffer layer; and a semi-conductive polyethylene (PE, Polyethylene) sleeve is disposed outside the alloy lead sleeve. An outer lining is provided on the outer side of the semiconductive PE sleeve.

In order to increase the tensile strength, as an embodiment, a steel wire armor layer is disposed outside the inner liner layer, and the steel wire armor layer includes a plurality of steel wires having a diameter of 3.0 mm, 5.0 mm, 6.0 mm or 8.0 mm.

In order to make it have photoelectric composite performance and prolong the service life, as an embodiment, an optical cable is disposed in the steel wire armor layer, and a filling strip is disposed on both sides of the optical cable;

The outer diameter of the filling strip is the same as the outer diameter of the steel wire and larger than the outer diameter of the cable; the outer layer of the steel wire armor layer is provided with an outer layer.

The structure is used for a large-section cable, so that the cross-section of the direct current submarine cable is 3000 mm ^{2 -} 4000 mm ² .

In order to further improve the water blocking effect, as an embodiment, a water blocking glue is disposed between each type of single line; a semiconductive water belt is disposed between each layer and each layer.

The beneficial effects of the technical solution described in the embodiments of the present invention are:

The DC submarine cable provided by the embodiment of the invention effectively improves the water blocking effect on the one hand, overcomes the problem that the laying is limited by the drop; on the other hand, it can meet the requirements of large length, high power and large capacity; It effectively improves corrosion resistance and tensile strength, prolongs cable life and reduces costs.

DRAWINGS

1 is a schematic structural view of a DC submarine cable according to an embodiment of the present invention;

2 is a partial enlarged structural view of the portion A in FIG. 1 according to an embodiment of the present invention;

3 is a schematic structural view of a factory joint according to an embodiment of the present invention.

detailed description

In the following, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. It is a partial embodiment of the invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

As shown in FIG. 1 to FIG. 3, a DC submarine cable includes a hexagonal support core 1 having a side length of 3.3 mm to 3.7 mm; as an alternative embodiment, In the embodiment, the hexagonal support core 1 has a side length of 3.5 mm.

The outer side of the hexagonal support core 1 is provided with a first type of line layer 2, and the cross-sectional area of the first type line layer 2 is 200 mm ^{2 -} 202 mm ² ; in this embodiment, the cross-sectional area of the first type line layer 2 is 201.1 mm ² . The first type line layer 2 includes six first type line single lines 2a, and the six first type line single lines 2a are rounded after being twisted with the support core 1, and the cross-sectional areas of the first type line single lines 2a are both 28.50 mm ^{2 -} 29.5. Mm ² ; In this embodiment, the cross-sectional area of the first type line single line 2a is 29 mm ² .

The outer side of the first type of line layer 2 is provided with a second type of line layer 3, and the cross-sectional area of the second type of line layer 3 is 313.2 mm ^{2 -} 315.2 mm ² ; in this embodiment, the cross-sectional area of the second type of line layer 3 is 314.2mm ² , the second type line layer 3 includes twelve second type line single lines 3a, and the twelve second type line single lines 3a are rounded and twisted with the first type line layer 2, and each second type line single line 3a cross-sectional area are 8mm ² -10mm ^2; embodiment according to the present embodiment, the sectional area of each of the second type are lINES 3a 9mm ^2.

The outer side of the second type line layer 3 is provided with a third type of line layer 4, and the cross-sectional area of the third type line layer 4 is 451.2 mm ^{2 -} 453.2 mm ² ; in this embodiment, the cross-sectional area of the third type line layer 4 is 452.4mm ² . The third type line layer 4 includes eighteen third type line single lines 4a, and the eighteenth type line single lines 4a and the second type line layer 3 are twisted and rounded, and the cross-sectional area of each third type line single line 4a are 6.5mm ² -8.5mm ^2; embodiment according to the present embodiment, each of the third type lINES 4a are cross-sectional area of 7.7mm ^2.

The fourth type line layer 5 is provided on the outer side of the third type line layer 4, and the cross-sectional area of the fourth type line layer 5 is 614.2 mm ² -616.2 mm ² . In this embodiment, the cross-sectional area of the fourth type line layer 5 is 615.8mm ² . The fourth type line layer comprises twenty-four fourth type line single lines 5a, and the twenty-fourth type line single lines 5a and the third type line layer 4 are twisted and rounded, and the fourth type line single line 5a is cut. area are 5.5mm ² -7.5mm ² in this embodiment, the sectional area of each of the fourth type lINES 5a are 6.8mm ^2.

The fifth type line layer 6 is disposed on the outer side of the fourth type line layer 5, and the cross-sectional area of the fifth type line layer 6 is 803 mm ² -805 mm ² ; in this embodiment, the cross-sectional area of the fifth type line layer 6 is 804.2 mm. ² . The fifth type line layer 6 includes thirty fifth type line single lines 6a, and the fifth type line single line 6a and the fourth type line layer 5 are rounded and rounded, and each fifth type line single line 6a has a cross-sectional area of 5.5. mm ² -7.5mm ^2, in this embodiment, the cross-sectional area of the fifth type lINES 6a are 6.3mm ^2.

A sixth type of wire layer 7 is disposed on the outer side of the fifth type wire layer 6. The cross-sectional area of the sixth type wire layer 7 is 1074 mm ^{2 -} 1076 mm ² . In this embodiment, the cross-sectional area of the sixth type wire layer 7 is 1075.2 mm. ² . The sixth type line layer 7 includes thirty-six sixth type line single lines 7a, and the sixth type line single line 7a and the fifth type line layer 6 are twisted and rounded, and the cross-sectional area of each of the sixth type line single lines 7a is 6.8 mm ^{2 -} 8.2 mm ² , in this embodiment, the cross-sectional area of the sixth type wire single wire 7a is 7.5 mm ² .

The outer side of the sixth type wire layer 7 is provided with a semiconductive shield 9. In the present embodiment, the semiconductive shield 9 is an extruded semiconductive shielding material. The outer side of the semiconductive shield 9 is provided with a crosslinked polyethylene insulating layer 10; the outer side of the crosslinked polyethylene insulating layer 10 is provided with an insulating shield layer 11. In this embodiment, the cross-linked polyethylene insulation layer 10 is dedicated to a high-voltage DC power cable, and the electrical properties and physical properties of the material can satisfy the insulation of the high-voltage DC cable and greatly reduce the formation of space charge. In order to meet the above requirements, we have chosen a non-polar cross-linked polyethylene insulation material, which has a good addition. Excellent performance, mechanical and electrical properties, and its structure is:

--[--CH2--CH2--]n---[CH2--CH--]---[CH2--CH2--]x----[CH2--CH--[CH2- -CH2--]a-/

/

--[--CH2--CH2--]m---[CH2--CH--]--[CH2--CH2--]y----[CH2--CH--[CH2-- CH2--]b--

In the middle is a cross-linking bond, which is generally initiated by a peroxide, forms a radical, forms a cross-linking bond between the radicals, and forms a three-dimensional solid polymer from the linear polymer.

The main properties of the insulation are shown in Table 1:

Table 1 physical properties

Table 2 Electrical properties

A semi-conductive water buffer layer 12 is disposed outside the insulating shielding layer 11; in the embodiment, the semi-conductive water buffer layer 12 is a semi-conductive water ribbon having a high water expansion rate. The outer casing of the semi-conductive water buffer layer 12 is provided with an alloy lead sleeve 13; in the embodiment, the alloy lead sleeve 13 is a high-quality lead alloy material which is extruded in a radial waterproof layer. The outer side of the alloy lead sleeve 13 is provided with a semiconductive PE sleeve 14. In the present embodiment, the semiconductive PE sleeve 14 is extruded to prevent damage during the lead sheath production process. An inner liner layer 15 is disposed outside the semiconductive PE sleeve 14. In this embodiment, the inner liner layer 15 is made of modified asphalt made of PP rope and cable.

This product is equipped with cable modified asphalt with excellent corrosion resistance on the surface of the cable metal sheath (lead sleeve surface, steel wire surface). The asphalt adopts special formula and has good adhesion performance.

Modified asphalt formulations are shown in Table 3:

Table 3 modified asphalt formula

material	Weight (kg)
asphalt	500
PE (melt index less than 100)	twenty three
rosin	twenty three
Coupling agent	2.8

A steel wire armor layer 16 is disposed outside the inner liner layer 15, and the wire armor layer 16 includes a plurality of steel wires 16a having a diameter of 3.0 mm, 5.0 mm, 6.0 mm, or 8.0 mm. This product tensile layer mining Thick round or flat steel wire (double or single layer) and zinc-aluminum-magnesium alloy coated steel wire, the diameter of the round wire can be 5.0mm, 6.0mm or 8.0mm. The flat steel wire is used, and the thickness can be 3.0 mm, 5.0 mm, and 6.0 mm. In this embodiment, a thick round steel wire having a diameter of 6.0 mm is used.

Under normal circumstances, according to the water depth of the submarine cable laying, single-layer steel wire armor is generally used below 300 meters, and double-layer reverse steel wire armor is used for 300 meters and above. The steel wire armor can meet the cable laying depth and ensure that the cable is subjected to a large tensile force. The corrosion resistance of this material is 8.76 times that of ordinary hot-dip galvanized steel wire. The coating utilizes the dual functions of electrochemical protection of the sacrificial anode and protection of the corrosion product film. Once the protective film is formed, it is no longer corroded, greatly extending the service life of the cable.

The invention relates to a high voltage, a large cross section, a large capacity and a communication transmission, which are mainly suitable for a power cable for a large length submarine power transmission, and are suitable for various underwater transmission and distribution systems and equipment connections. The invention provides a high voltage and ultra high voltage XLPE insulated DC submarine cable. This cable has good corrosion resistance, high tensile strength and high water resistance. It can be immersed in sea water for a long time, and is not limited by the installation drop. It can fully meet the requirements of large-length, high-power submarine power DC transmission system and realize electricity. , communications and submarine cable operation monitoring targets.

A cable 17 is disposed in the wire armor layer 16. The fiber cable 17 is provided with filler bars on both sides thereof; the outer diameter of the filler bar is the same as the outer diameter of the wire 16a and larger than the outer diameter of the cable 17; the outer side of the wire armor layer 16 is disposed There is an outer layer 18. In this embodiment, the outer layer 18 is composed of asphalt, PP rope, asphalt, PP rope, asphalt, and non-woven tape.

A water blocking glue is disposed between each type of single line; a semiconductive water belt is disposed between each layer and each layer. In this embodiment, the optical cable adopts a single-mode optical fiber and a multi-mode optical fiber, and the outer layer is a stainless steel loose tube and a PE sheath, and the loose tube is filled with a water-blocking grease. In order to prevent the cable from being subjected to mechanical external force, the outer diameter of the cable is smaller than the outer diameter of the armor wire, the cable is placed symmetrically, and a circular PE strip is used for protection on both sides of the cable. When the cable is composited, it is stranded in the same layer as the inner layer of steel wire, and has a certain excess length.

The purpose of photoelectric composite is to enable condition monitoring and remote control while delivering electrical energy. The ability to provide early warning capabilities for power transmission and real-time monitoring. Effectively identify DC submarine cable sheath defects, faults, abnormal overheating and fires, so that the cable has a certain early fault prediction capability.

The conductor structure of the invention is not within the scope of GB/T3956-2008 standard, considering the large section, high voltage, large capacity transmission, meeting the requirements of the sea cable laying environment, the product structure design is required, and the analysis and comparison of several structural designs are finally carried out. Choose the best solution.

1) Squeeze the circular + water blocking structure. According to the national standard GB/T3956-2008, the second type of compacted circular stranded conductor structure can meet the requirements, but the large cross-section conductor is pressed tightly. After pressing, the outer diameter is large, the gap between the wire diameters is not easy to fill, the water blocking effect is not good, and the conductor compacting filling coefficient is difficult to reach more than 90%. There are big flaws that should not be used.

2) Split conductor + water blocking structure, split conductor according to the requirements of high voltage cable standard, in general, 800mm2 and above should be used to split the conductor, and the water blocking effect of the submarine cable using split conductor + water blocking material is not good, there is no domestic and foreign This structure should not be used.

3) Round + type line + water blocking structure, the center adopts the compacted circular stranded conductor, and the stranding of the profile line is adopted outside the layer. This structure is unstable in production, the processing effect is poor, and the interface between the circular and the profile line The water blocking effect is not good, it is difficult to meet the water blocking requirements, and it is not suitable to adopt

4) Profile + water blocking structure, the center conductor adopts 6-sided conductor instead of round conductor, and the center twisted conductor of the target polygon is not suitable for pulling out and is more stable. It is easy to draw when using a round shape. The conductor stranding method is 1+6+12+18+24+30+36 regular stranding.

The conductor stranded layer and the layer adopt a profile conductor. After the structure is processed, the outer diameter is small, and the conductor compaction coefficient can reach not less than 0.9. The gap between the profiles is easy to fill the water blocking material, the conductor structure is stable, and the super large section resistance is satisfied. Water structure, soft joint conductor welding is easy to recover, therefore, this structure is the best choice.

In this embodiment, the water blocking layer structure of the cable comprises a longitudinal water blocking layer and a radial water blocking layer, and the longitudinal water blocking layer is included inside the conductor and outside the insulated core, and the inside of the conductor is made of water blocking glue or water blocking. High to meet the water blocking performance of water seepage. The outer part of the conductor insulated core is a semi-conductive water belt with high water resistance. The water-blocking material expands rapidly with water, effectively preventing the longitudinal diffusion of water and achieving a good longitudinal water-blocking effect. The radial water-blocking layer of the cable adopts a layer of extruded alloy lead sleeve, which is a dense seamless round tube. The outer wall of the tube is coated with a layer of anti-corrosion asphalt, which is extruded with a semi-conductive PE sheath. The integrated water-blocking layer not only has a good radial water-blocking effect, but also has excellent corrosion resistance, so that the cable is safely operated on the seabed.

The cross section of the DC submarine cable is 3000mm ² -4000mm ² . In this embodiment, the conductor structure is 3500mm ^2, the structure 1 + 6 + 12 + 18 + 24 + 30 + 36; 127 core, the total sectional area of the conductor 3499.7mm ^2, the outer diameter of the conductor 68.7mm. The structure of the present invention is for use with large cross-section (3000 mm ^{2 -} 4000 mm ² ) cables. The structure of the invention can be effectively used in the manufacture of such a large-section conductor, which can effectively improve the water blocking effect, overcome the difficulty of laying restrictions, and meet the requirements of large length, high power and large capacity; effectively improve corrosion resistance and tensile strength. Force performance, extending cable life and reducing costs. However, if this configuration is used in a small section of the cable is less than 3000mm ² -4000mm ^2, not only have the above advantageous effects, even shorter lifetime, less effective, so this layered structure only for large 3000mm ² -4000mm ² The cross-section cable can effectively produce the above beneficial effects. The prior art can solve the problem of laying drop by using a cross-linked polyethylene insulating material, but the stability is poor when the cable is used. In the present embodiment, the cross-linked polyethylene insulating material and the hexagonal support of the present invention are used. The combination of the core 1 and the profile layer effectively improves the stability and, after being used in combination with the layered structure, further improves the stability (only for large-section conductors).

The present invention can weld two conductors together through a factory joint (soft joint). The factory joints use special joint equipment, including the form of extrusion vulcanization. The conductor joints are welded with low-resistance silver electrodes and are layered and misaligned. The chemical reaction heat of metal compounds is used as a heat source to pass the superheated (reduced) molten metal. Direct or indirect exothermic welding; integral welding, using tungsten argon arc welding, the whole conductor is welded, the conductor weld is fan-shaped, and argon and helium are welded. An inert gas such as gas is a protective gas to prevent excessive oxidation of the conductor; the conductor is welded to ensure that the tensile strength and electrical properties of the cable meet the requirements. The insulated joint equipment adopts a twin-screw extruder to recover the new modified cross-linked polyethylene insulation material and semi-conductive shielding material layer by layer to achieve the same effect as the cable body performance. The lead sheath and the semi-conductive PE sheath recovery are recovered by prefabricated lead tube welding. The special lead sleeve is used to pull the mold, and the welded lead sleeve is pulled to make the outer diameter close to the outer diameter of the body, and then the semi-conductive PE sheath is restored. . Make sure that the outer diameter of the cable joint is close to the outer diameter of the body for subsequent production.

Conductor welding 100, the key first step in the production of large length submarine cables is conductor welding. The first link to achieve the two cable connections is generally divided into exothermic welding, integral welding, and delamination misalignment welding. The welding tensile strength needs to reach 85% of the cable body; the inner shield recovery area 20, after the conductor welding is restored, the grinding process is performed, and then the inner shield is restored in the area; the insulating layer recovery area 30, the area continues the previous process After completion, the insulation layer is restored by special mold and special extrusion equipment, and vulcanization is performed; the insulating shielding layer recovery area 40 is generally larger than the outer diameter of the main body after the recovery of the insulation layer, so it needs to be refined and polished to The outer diameter is similar to the outer diameter of the body. The inner shield is reserved 50, and the two cables are shielded from the reserved part. The purpose is that the inner shield at the joint is better compatible with the inner body screen; the reaction cone 60, the reaction force cone to be refined when the insulation is restored, The purpose is to make the insulation and the body insulation interface at the soft joint smooth and excessive, and improve the electric field distribution at the insulation interface; the insulation layer shield is reserved 70, the same as the inner shield, and the semi-conductive paint is sprayed after the insulation layer is restored; lead The sheath and the semi-conductive PE outer sheath recover 80, control the lead sheath to restore the outer diameter and the outer diameter of the semi-conductive PE outer sheath, ensure that the outer diameter of the soft joint is close to the outer diameter of the body, and meet the physical properties for subsequent process production. .

The above has described in detail the preferred embodiments of the invention. It will be appreciated that many modifications and variations can be made in the present invention without departing from the scope of the invention. Therefore, any technical solution that can be obtained by a person skilled in the art according to the prior art by logic analysis, reasoning or limited experiment according to the prior art should be claimed by the claims. Within the scope of protection determined by the book.

Industrial applicability

The DC submarine cable according to the embodiment of the present invention comprises a hexagonal support core, the side length of the hexagonal support core is 3.3 mm-3.7 mm, and the first type of line layer is disposed outside the hexagonal support core, first line layer comprises a first type six-line type line, six-line type first-line with the circular support core strand, each of the first type are cross-sectional area lINES 28.50mm ² -29.5mm ^2. The DC submarine cable according to the embodiment of the invention effectively improves the water blocking effect on the one hand, overcomes the problem that the laying is limited by the drop; on the other hand, it can meet the requirements of large length, high power and large capacity; In terms of aspect, it effectively improves corrosion resistance and tensile strength, prolongs cable life and reduces costs.

Claims (10)

1. A DC submarine cable comprising a hexagonal support core (1), the hexagonal support core (1) having a side length of 3.3 mm - 3.7 mm;

   A first type of line layer (2) is disposed outside the hexagonal support core (1), and the first type line layer (2) includes six first type line single lines (2a), and the six first type lines singlet (2a) of said supporting core (1) has a circular shape after twisting, each of said first type lINES (2a) are cross-sectional area of 28.50mm ² -29.5mm ^2;

   The outer side of the first type line layer (2) is provided with a second type line layer (3), and the second type line layer (3) includes twelve second type line single lines (3a), the twelve The second type line single line (3a) is rounded after being twisted with the first type line layer (2), and the cross-sectional area of each of the second type line single lines (3a) is 8 mm ² -10 mm ² ;

   The outer side of the second type line layer (3) is provided with a third type line layer (4), and the third type line layer (4) comprises eighteen third type line single lines (4a), the eighteen lINES of third type (4a) and the second type after stranding wire layer (3) has a circular shape, each of the third type lINES (4a) are cross-sectional area of 6.5mm ² -8.5mm ² ;

   The outer side of the third type of line layer (4) is provided with a fourth type of line layer (5), and the fourth type of line layer comprises twenty-four fourth type line single lines (5a), the twenty-four The fourth type line single line (5a) is rounded after being twisted with the third type line layer (4), and the cross-sectional area of each of the fourth type line single lines (5a) is 5.5 mm ^{2 -} 7.5 mm ² .
2. The direct current submarine cable according to claim 1, wherein said first type of line layer (2) has a sectional area of 200 mm ^{2 to} 202 mm ² ; and said second type of line layer (3) has a sectional area of 313.2 mm ² - 315.2 mm ² ; the cross-sectional area of the third type wire layer (4) is 451.2 mm ^{2 -} 453.2 mm ² ; and the cross-sectional area of the fourth type wire layer (5) is 614.2 mm ^{2 -} 616.2 mm ² .
3. The direct current submarine cable according to claim 1, wherein a fourth type of wire layer (6) is disposed outside the fourth type wire layer (5), and the fifth type wire layer (6) includes thirty a fifth type line single line (6a), the fifth type line single line (6a) is rounded after being twisted with the fourth type line layer (5), and the cut of each of the fifth type line single line (6a) The area is 5.5mm ² -7.5mm ² ;

   The sixth type line layer (6) is provided with a sixth type line layer (7), and the sixth type line layer (7) includes thirty-sixth type line single line (7a), the type VI lINES (7a) and the fifth wire-type layer (6) has a circular shape after twisting, each of the sixth type lINES (7a) are cross-sectional area of 6.8mm ² -8.2mm ^2.
4. DC submarine cable according to claim 3, wherein said fifth layer profile (6) sectional area of 803mm ² -805mm ^2; sixth type cross-sectional area of the wire layer (7) is 1074mm ² - 1076mm ² .
5. The direct current submarine cable according to claim 4, wherein a semi-conductive shield (9) is disposed outside the sixth type wire layer (7); and a cross-linked polyethylene is disposed outside the semi-conductive shield (9) An insulating layer (10); an insulating shielding layer (11) is disposed outside the cross-linked polyethylene insulating layer (10).
6. The direct current submarine cable according to claim 5, wherein a semi-conductive water buffer layer (12) is disposed outside the insulating shielding layer (11); and an alloy lead is disposed outside the semi-conductive water buffer layer (12). The sleeve (13) is provided with a semiconductive PE sleeve (14) on the outer side of the alloy lead sleeve (13), and an inner liner layer (15) is disposed on the outer side of the semiconductive PE sleeve (14).
7. The direct current submarine cable according to claim 6, wherein a steel wire armor layer (16) is disposed outside the inner liner layer (15), and the steel wire armor layer (16) comprises a plurality of steel wires (16a). The steel wire (16a) has a diameter of 3.0 mm, 5.0 mm, 6.0 mm or 8.0 mm.
8. The DC submarine cable according to claim 7, wherein the steel wire armor layer (16) is provided with a fiber cable (17), and the fiber cable (17) is provided with filler bars on both sides thereof;

   The outer diameter of the filling strip is the same as the outer diameter of the steel wire (16a) and larger than the outer diameter of the optical cable (17); the outer side of the steel armor layer (16) is provided with an outer layer (18).
9. The direct current submarine cable according to any one of claims 1 to 8, wherein the direct current submarine cable has a cross section of 3000 mm ^{2 to} 4000 mm ² .
10. The direct current submarine cable according to claim 9, wherein a water blocking glue is disposed between each of the plurality of types of wires; and a semiconductive electric water belt is disposed between each layer and each layer.

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