Direct current submarine cable

Abstract

The invention discloses a direct-current submarine cable which comprises a conductor layer, an optical cable layer, a first circulating cooling layer, a second circulating cooling layer, a shielding layer and a protective layer. The cross section of each layer is a concentric circle, and the optical cable layer, the first circulating cooling layer, the conductor layer, the second circulating cooling layer, the shielding layer and the protection layer are sequentially distributed on the direct-current submarine cable from inside to outside. The optical cable layer is arranged in the conductor layer, so that the monitoring unit is closer to the conductor layer, timely early warning is facilitated when an abnormal condition occurs, and a fault point is accurately positioned. After the optical cable layer is built in, a filling layer for protecting the optical cable layer can be removed, the overall outer diameter of the submarine cable is reduced, and laying is facilitated. Circulating cooling layers are respectively arranged between the optical cable layer and the conductor layer and between the conductor layer and the shielding layer, so that the actual operation temperature of the direct-current submarine cable is reduced, and the output capacity is improved.

Description

Technical Field

[0001] The present invention relates to the field of high voltage cables, and in particular to a direct current submarine cable. Background Art

[0002] Existing DC submarine cables usually adopt a multi-layer structure from the inside to the outside, with the conductor layer located in the center and the optical cable layer usually placed on the outer layer of the submarine cable. The optical cable layer detection unit is too far away from the conductor layer, which may lead to the inability to timely warn and accurately locate the fault point when an abnormal situation occurs. In addition, the central conductor layer cannot dissipate heat well during operation and is prone to reach the maximum operating temperature, resulting in a reduction in the transmission capacity of the DC submarine cable. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a DC submarine cable, which is convenient for timely warning and accurate positioning of fault points, reduces the operating temperature of the conductor layer, and improves the output capacity.

[0004] An embodiment of the present invention provides a DC submarine cable, comprising: a conductor layer, an optical cable layer, a first circulating cooling layer, a second circulating cooling layer, a shielding layer and a protective layer; The cross section of each layer is a concentric circle, and the DC submarine cable is sequentially distributed with the optical cable layer, the first circulating cooling layer, the conductor layer, the second circulating cooling layer, the shielding layer and the protective layer from the inside to the outside.

[0005] Preferably, the shielding layer comprises a conductor shielding layer, an insulating layer and an insulating shielding layer; The shielding layer is sequentially distributed with the conductor shielding layer, the insulating layer and the insulating shielding layer from the inside to the outside.

[0006] Preferably, the protective layer comprises a copper-plastic composite tape.

[0007] Furthermore, the protective layer also includes a water blocking tape, a semiconductor sheath, a carbon fiber layer and a nylon sheath; The protective layer is sequentially provided with the water-blocking tape, the copper-plastic composite tape, the semiconductor sheath, the carbon fiber layer and the nylon sheath from the inside to the outside.

[0008] Furthermore, the water blocking tape is wrapped around the outside of the shielding layer in two layers with an overlap of 15%.

[0009] Furthermore, the copper-plastic composite tape is composited with copper and polypropylene materials in the same volume ratio; The copper-plastic composite tape is wrapped around the outside of the water-blocking tape with a 25% overlap.

[0010] Preferably, the conductor layer is made of solid concentric circular copper conductor.

[0011] Preferably, a circulation system filled with cooling liquid medium is provided in the first circulation cooling layer or the second circulation cooling layer, and heat conduction cooling is performed through the circulation system.

[0012] Preferably, the optical cable layer is composed of a plurality of optical fibers with outer layers wrapped with a silica coating.

[0013] As a preferred solution, the outer diameter of the optical cable layer is 5 mm, the inner diameter of the conductor layer is 7 mm, and the outer diameter of the conductor layer is 57 mm; The conductor layer is covered with a layer of water-blocking glue, and the first circulating cooling layer is arranged with a 1mm gap between the conductor layer and the optical cable layer.

[0014] An embodiment of the present invention provides a DC submarine cable, comprising: a conductor layer, an optical cable layer, a first circulating cooling layer, a second circulating cooling layer, a shielding layer and a protective layer; the cross-section of each layer is a concentric circle, and the DC submarine cable is sequentially distributed with the optical cable layer, the first circulating cooling layer, the conductor layer, the second circulating cooling layer, the shielding layer and the protective layer from the inside to the outside. Placing the optical cable layer inside the conductor layer allows the monitoring unit to be closer to the conductor layer, which is convenient for timely warning when an abnormal situation occurs and accurate positioning of the fault point. After the optical cable layer is built in, the filling layer protecting the optical cable layer can be removed to reduce the overall outer diameter of the submarine cable for easy laying. Circulating cooling layers are respectively arranged between the optical cable layer and the conductor layer, and between the conductor layer and the shielding layer to reduce the actual operating temperature of the DC submarine cable and increase the output capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of a DC submarine cable provided by an embodiment of the present invention; Figure 2 It is a structural schematic diagram of a DC submarine cable provided by another embodiment of the present invention. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Existing DC submarine cables usually adopt a multi-layer structure from the inside out, including a conductor layer, a shielding layer, and a protective layer consisting of a water-blocking tape, a lead sheath, a PE sheath, a filling layer (including an optical cable layer), a metal wire armor, and a PP outer layer. These materials and structures are designed to ensure that the DC submarine cable can work normally in the submarine environment. However, there are still some problems with existing submarine cables in practical applications: The optical cable layer is usually placed on the outer layer of the submarine cable, which requires a filling layer to protect the optical cable layer, resulting in an increase in the outer diameter of the submarine cable. At the same time, the optical cable layer detection unit is too far away from the conductor layer, which may lead to the inability to provide timely warning and accurately locate the fault point when an abnormal situation occurs.

[0018] In the existing submarine cable structure, the conductor layer is located at the center, which cannot dissipate heat well during operation and is more likely to reach the maximum operating temperature, resulting in a reduction in the transmission capacity of the DC submarine cable.

[0019] In order to solve the above technical problems, an embodiment of the present invention provides a DC submarine cable, comprising: a conductor layer, an optical cable layer, a first circulating cooling layer, a second circulating cooling layer, a shielding layer and a protective layer; The cross section of each layer is a concentric circle, and the DC submarine cable is sequentially distributed with the optical cable layer, the first circulating cooling layer, the conductor layer, the second circulating cooling layer, the shielding layer and the protective layer from the inside to the outside.

[0020] When this embodiment is implemented, see Figure 1 , is a schematic structural diagram of a DC submarine cable provided by an embodiment of the present invention; the submarine cable is composed of a conductor layer 3, each layer of which has a concentric circular cross-section, an optical cable layer 1, a first circulating cooling layer 2, a second circulating cooling layer 4, a shielding layer 20 and a protective layer 30.

[0021] Among them, the optical cable layer 1 is located in the center of the DC submarine cable, and the submarine cable is distributed with the optical cable layer 1, the first circulating cooling layer 2, the conductor layer 3, the second circulating cooling layer 4, the shielding layer 20 and the protective layer 30 from the inside to the outside.

[0022] It should be noted that the shielding layer is arranged between the conductor layer and the external protective layer for insulating and shielding the conductor layer. The prior art provides a variety of specific structures of the shielding layer. In this case, the shielding layer can adopt the existing shielding belt structure with insulating shielding function, which will not be elaborated here.

[0023] It should be noted that the protective layer is arranged on the outermost layer of the cable and is used for supporting the structural strength of the cable and for corrosion protection. In this case, the protective layer can adopt the existing protective layer structure, which will not be elaborated here.

[0024] In this case, by placing the optical cable layer inside the conductor layer, the monitoring unit is closer to the conductor layer for accurate monitoring, which is convenient for timely warning when abnormal conditions occur and accurate location of the fault point. After the optical cable layer is built in, the filling layer protecting the optical cable layer can be removed, reducing the overall outer diameter of the submarine cable and facilitating its installation.

[0025] Circulating cooling layers are set in the optical cable layer and the conductor layer, and in the conductor layer and the shielding layer respectively, so as to increase the transmission current and the output capacity by lowering the actual operating temperature of the DC submarine cable.

[0026] In another embodiment provided by the present invention, the shielding layer includes a conductor shielding layer, an insulating layer and an insulating shielding layer; The shielding layer is sequentially distributed with the conductor shielding layer, the insulating layer and the insulating shielding layer from the inside to the outside.

[0027] When this embodiment is implemented, see Figure 2 , is a schematic structural diagram of a DC submarine cable provided by another embodiment of the present invention; The shielding layer 20 of the submarine cable comprises a conductor shielding layer 5, an insulating layer 6 and an insulating shielding layer 7; From the inside to the outside, a conductor shielding layer 5, an insulating layer 6 and an insulating shielding layer 7 are sequentially arranged in concentric circles.

[0028] The insulating layer is used to provide insulation protection for the conductor layer.

[0029] The conductor shielding layer is a shielding layer of semi-conductive material added on the surface of the conductor layer. It has the same potential as the shielded conductor layer and is in good contact with the insulating layer, thereby avoiding local discharge between the conductor layer and the insulating layer.

[0030] Since there may be gaps at the contact point between the insulation surface and the sheath of the protective layer, cracks are easily formed on the insulation surface of the oil-paper cable when the cable is bent, which are factors that cause partial discharge. A shielding layer of semi-conductive material is added to the surface of the insulation layer, namely the insulating shielding layer, which has good contact with the shielded insulation layer and has the same potential as the sheath of the protective layer, thereby avoiding partial discharge between the insulation layer and the protective layer.

[0031] Among the conductor shielding layer, the insulation layer and the insulation shielding layer, the thickness of the conductor shielding layer is 2mm, the thickness of the insulation layer is 31mm, and the thickness of the insulation shielding layer is 2mm. The conductor shielding layer, the insulation layer and the insulation shielding layer are formed by three-layer co-extrusion at one time, and a gap of 1mm is reserved near the conductor layer shielding for circulation cooling.

[0032] The three-layer shielding protection is formed by the conductor shielding layer, the insulating layer and the insulating shielding layer to reduce the electromagnetic interference to the outside world, limit the impact of the external electromagnetic field on the internal conductor layer, and improve the working stability of the submarine cable.

[0033] In another embodiment provided by the present invention, the protective layer includes a copper-plastic composite tape.

[0034] When this embodiment is implemented, see Figure 2 , the protective layer 30 includes a copper-plastic composite tape 9.

[0035] The copper-plastic composite tape is used to replace the lead sheath in the traditional protective layer to reduce the overall weight of the DC submarine cable, which is conducive to the laying in deep sea environment.

[0036] In another embodiment provided by the present invention, the protective layer further comprises a water blocking tape, a semiconductor sheath, a carbon fiber layer and a nylon sheath; The protective layer is sequentially provided with the water-blocking tape, the copper-plastic composite tape, the semiconductor sheath, the carbon fiber layer and the nylon sheath from the inside to the outside.

[0037] When this embodiment is implemented, see Figure 2 The protective layer 30 also includes a water-blocking tape 8, a copper-plastic composite tape 9, a semiconductor sheath 10, a carbon fiber layer 11 and a nylon sheath 12 which are sequentially distributed from the inside to the outside; In this case, the mechanical protection structure uses a carbon fiber layer, which replaces the metal wire armor and PP outer layer in the traditional submarine cable, and a nylon 12 sheath is wrapped around the carbon fiber layer. This design not only improves the tensile and lateral pressure resistance of the submarine cable, but also improves the wear resistance and corrosion resistance of the submarine cable.

[0038] In another embodiment provided by the present invention, the water blocking tape is formed by overlapping two layers with a 15% overlap on the outside of the shielding layer.

[0039] In the specific implementation of this embodiment, the thickness of the water blocking tape is 0.8 mm, and two layers with 15% overlap are wrapped around the outside of the insulation shield.

[0040] The production process of wrapping various strip-shaped, linear metal or non-metallic materials spirally onto the cable core or cable core at a specified pitch is called the wrapping process. The general principle for the cable diameter before wrapping is that the thicker the cable, the wider the tape should be. The wrapping angle should be between 30 and 45 degrees. If the angle is too small, it will affect the production efficiency. On the contrary, if the angle is too large, it will affect the tightness of the tape and the cable may not be round. The wrapping method is one layer of overlapping wrapping or two layers of gap overlapping wrapping. Cables with larger core diameters generally use two layers of gap overlapping wrapping.

[0041] By wrapping with two layers with 15% overlap, the tape is least affected by cable bending and has high production efficiency.

[0042] In another embodiment provided by the present invention, the copper-plastic composite tape is composited by copper and polypropylene materials in the same volume ratio; The copper-plastic composite tape is wrapped around the outside of the water-blocking tape with a 25% overlap.

[0043] The copper-plastic composite tape is made of copper and polypropylene materials, with a copper content of 50% and a polypropylene content of 50%. The thickness of the copper-plastic composite tape is 1mm, and it is wrapped around the outside of the water-blocking tape with a 25% overlap.

[0044] The semi-conductive sheath is made of polyethylene material with a thickness of 3.4 mm and is extruded outside the copper-plastic composite tape.

[0045] The carbon fiber protective layer is composed of carbon fiber strips and nylon 12 material. The carbon fiber strips have a diameter of 5 mm and are wound around the outside of the semi-conductive layer at a pitch of 3500 mm. A layer of 0.5 mm nylon 12 material is wrapped around the outside of the carbon fiber layer.

[0046] In another embodiment provided by the present invention, the conductor layer is made of solid concentric circular copper conductor.

[0047] In the specific implementation of this embodiment, a solid concentric copper conductor is used as a current transmission carrier. The DC submarine cable does not need to consider the skin effect. Compared with the compressed circular conductor layer of the same specification, the solid concentric copper conductor has a smaller resistance and can transmit a higher current. At the same time, the optical cable layer can be accommodated inside.

[0048] In another embodiment provided by the present invention, a circulation system filled with cooling liquid medium is provided in the first circulation cooling layer or the second circulation cooling layer, and heat conduction cooling is performed through the circulation system.

[0049] During the specific implementation of this embodiment, a cooling medium is added to the reserved gaps between the optical cable layer and the conductor layer, and between the conductor layer and the shielding layer. The cooling medium in the cooling layer is transformer oil. These liquid media can be continuously circulated between the optical cable layer and the conductor layer, and between the conductor layer and the shielding layer through a special circulation system, thereby effectively reducing the temperature of the conductor layer. The temperature of the transformer oil is controlled between 30°C and 65°C, ensuring that the DC submarine cable can operate stably at a maximum operating temperature not exceeding 70°C, thereby improving the transmission capacity.

[0050] In another embodiment provided by the present invention, the optical cable layer is composed of a plurality of optical fibers with outer layers wrapped with a silica coating.

[0051] In the specific implementation of this embodiment, the optical cable layer is composed of 48 optical fibers, each of which has a diameter of 0.1 mm and a numerical aperture of 0.18 mm. The outer layer of the optical fiber is coated with a layer of silicon dioxide coating, and the thickness of the silicon dioxide coating is 0.01 mm.

[0052] It should be noted that in the present embodiment, the optical cable layer is composed of 48 optical fibers. In other embodiments, the optical fibers may be of other numbers.

[0053] By using multiple optical fiber composite cable layers, the data transmission capacity of the optical cable layer can be increased.

[0054] In another embodiment provided by the present invention, the outer diameter of the optical cable layer is 5 mm, the inner diameter of the conductor layer is 7 mm, and the outer diameter of the conductor layer is 57 mm; The conductor layer is covered with a layer of water-blocking glue, and the first circulating cooling layer is arranged with a 1mm gap between the conductor layer and the optical cable layer.

[0055] In the specific implementation of this embodiment, the outer diameter of the optical cable layer is 5 mm, the outer diameter of the solid concentric copper conductor layer is 57 mm, the inner diameter is 7 mm, and the thickness is 25 mm.

[0056] The resistance of the copper conductor layer at 20°C is 0.0072Ω / km. Place the optical cable layer inside the concentric circle, and cover the conductor layer with a layer of water-blocking glue to ensure that the optical cable layer is located at the center of the circle. Reserve a 1mm gap near the inner diameter for circulating cooling.

[0057] A circulating cooling layer is formed by reserving gaps inside the conductor layer through water-blocking glue to ensure temperature transmission efficiency.

[0058] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A DC submarine cable, characterized in that: include: Conductor layer, optical cable layer, first circulation cooling layer, second circulation cooling layer, shielding layer and protective layer; The cross section of each layer is a concentric circle, and the DC submarine cable is sequentially distributed with the optical cable layer, the first circulating cooling layer, the conductor layer, the second circulating cooling layer, the shielding layer and the protective layer from the inside to the outside.

2. The DC submarine cable according to claim 1, characterized in that: The shielding layer comprises a conductor shielding layer, an insulating layer and an insulating shielding layer; The shielding layer is sequentially distributed with the conductor shielding layer, the insulating layer and the insulating shielding layer from the inside to the outside.

3. The DC submarine cable according to claim 1, characterized in that: The protective layer comprises a copper-plastic composite tape.

4. The DC submarine cable according to claim 3, characterized in that: The protective layer also includes a water blocking tape, a semiconductor sheath, a carbon fiber layer and a nylon sheath; The protective layer is sequentially provided with the water-blocking tape, the copper-plastic composite tape, the semiconductor sheath, the carbon fiber layer and the nylon sheath from the inside to the outside.

5. The DC submarine cable according to claim 4, characterized in that: The water blocking tape is wrapped around the outside of the shielding layer in two layers with 15% overlap.

6. The DC submarine cable according to claim 5, characterized in that: The copper-plastic composite tape is made of copper and polypropylene materials in the same volume ratio; The copper-plastic composite tape is wrapped around the outside of the water-blocking tape with a 25% overlap.

7. The DC submarine cable according to claim 1, characterized in that: The conductor layer adopts solid concentric copper conductor.

8. The DC submarine cable according to claim 1, characterized in that: A circulation system filled with cooling liquid medium is arranged in the first circulation cooling layer or the second circulation cooling layer, and heat conduction cooling is performed through the circulation system.

9. The DC submarine cable according to claim 1, characterized in that: The optical cable layer is composed of a plurality of optical fibers with outer layers wrapped with a silica coating.

10. The DC submarine cable according to claim 9, characterized in that: The outer diameter of the optical cable layer is 5 mm, the inner diameter of the conductor layer is 7 mm, and the outer diameter of the conductor layer is 57 mm; The conductor layer is covered with a layer of water-blocking glue, and the first circulating cooling layer is arranged with a 1mm gap between the conductor layer and the optical cable layer.

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