High-voltage three-core submarine cable

Abstract

The invention belongs to the technical field of submarine cables, and provides a high-voltage three-core submarine cable. Comprising a cable core, a waterproof layer, an inner sheath, an armor layer and an outer sheath, the cable core comprises at least one conductive core, the conductive core comprises a conductor and an insulation system arranged outside the conductor, the insulation system comprises a conductor shielding layer, an insulation layer and an insulation shielding layer, and the conductivity of the conductor shielding layer is gradually reduced from inside to outside in the radial direction of the conductive core; the conductivity of the insulation shielding layer is gradually reduced from outside to inside in the radial direction of the conductive core. The contact interface of the conductor shielding layer and the insulating layer prevents charge from gathering at the interface, and the electric field distribution between the conductor shielding layer and the insulating shielding layer is greatly optimized; similarly, the electric conductivity of the insulation shielding layer is set to be gradually increased in the direction away from the insulation layer, the interface electric field between the insulation layer and the insulation shielding layer is optimized, electric charges on the interface of the insulation layer can be rapidly led to the insulation shielding layer, and the partial discharge phenomenon is prevented.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of submarine cable, in particular to a high-voltage three-core submarine cable. BACKGROUND

[0002] Submarine power cables usually have an armor layer composed of a plurality of armor wires. The armor wires are usually spirally wound on the single-core or multi-core cable of the submarine power cable, and the armor layer provides mechanical protection against lateral impact during cable installation and operation. In alternating current power cables, alternating magnetic fields can cause different types of losses in the armor layer. For example, in a plane parallel to the cable axis, a circular induced current is formed inside a single wire, and this loss is called eddy current loss.

[0003] The use of non-magnetic metal materials such as stainless steel or copper can greatly reduce eddy current loss, however, these alternative materials are much more expensive than low-carbon steel. In addition, the use of high-grade steel can improve the tensile strength of the armor, and high-grade steel is more expensive than low-carbon steel. There are also designs that provide a plating or resin coating outside the steel wire, but the gap between the armor wires still causes technical problems such as water infiltration or structural instability. Some people also propose using non-metallic armor wires, such as aramid or para-aramid wires. This can increase the tensile strength of the armor and reduce weight, however, non-metallic armor wires lack the electromagnetic shielding effect of metal armor, and the cable still has a large loss.

[0004] On the other hand, the loss of metal armor is also affected by the insulation and conductive shielding effect of the cable. The dielectric constant and loss coefficient of the insulation layer directly affect the propagation speed and attenuation characteristics of electromagnetic waves in the shielding layer; if the shielding layer does not cooperate well with the insulation layer, electromagnetic waves may leak through the air gap or gap, and the reduced shielding effect will also cause electromagnetic loss of the armor. For example, air gaps may exist between the insulation layers due to manufacturing processes or material properties, causing uneven electric field distribution, potential step between the semiconductor shielding layer and the insulation layer, etc., which may cause partial discharge, thereby increasing cable loss and metal armor loss. SUMMARY

[0005] In order to solve the problems in the prior art, the present application provides a high-voltage three-core submarine cable, which comprises an insulation system, the insulation system comprising a conductor shielding layer, an insulation layer and an insulation shielding layer, the conductor shielding layer gradually decreasing in conductivity from inside to outside in the radial direction of the conductive core; the insulation shielding layer gradually decreases in conductivity from outside to inside in the radial direction of the conductive core, smoothing the interface electric field between the conductor shielding layer, the insulation layer and the insulation shielding layer, thereby solving the technical problem of partial discharge of the insulation system.

[0006] The embodiment of the application provides a high-voltage three-core submarine cable, which comprises a cable core, a water-blocking layer, an inner sheath, an armored layer and an outer sheath, the cable core comprises at least one conductive core, the conductive core comprises a conductor and an insulation system arranged outside the conductor, the insulation system comprises a conductor shielding layer, an insulation layer and an insulation shielding layer, the conductor shielding layer gradually decreases in conductivity from inside to outside in the radial direction of the conductive core; the insulation shielding layer gradually decreases in conductivity from outside to inside in the radial direction of the conductive core.

[0007] In some embodiments, the conductor shielding layer comprises a matrix and conductive fillers distributed in the matrix, and the filling proportion of the conductive fillers gradually decreases from inside to outside in the matrix material.

[0008] In some embodiments, the volume resistivity of the conductor shielding layer changes in any interval of 100 Ω / m-1000 Ω / m from inside to outside of the conductive core, and the difference of the interval is at least 100 Ω / m.

[0009] In some embodiments, the insulation shielding layer comprises a matrix, and conductive fillers and inorganic particles are added in the matrix, the filling proportion of the conductive fillers gradually increases from inside to outside in the matrix material, and the inorganic particles gradually decrease from inside to outside.

[0010] In some embodiments, the conductive fillers in the insulation shielding layer are attached to fibers to form conductive fibers, the insulation shielding layer comprises multiple layers of braided layers formed by the conductive fibers, and the matrix and the inorganic particles are filled between the pores of the braided layers.

[0011] In some embodiments, the conductive fibers in each layer of the insulation shielding layer have the same conductivity, but the braiding density of the braided layers gradually decreases from outside to inside.

[0012] In some embodiments, the conductive fibers in each layer of the insulation shielding layer have the same braiding density, but the conductivity of the conductive fibers of each braided layer gradually decreases from outside to inside.

[0013] In some embodiments, the volume resistivity of the insulation shielding layer changes in any interval of 100 Ω / m-500 Ω / m from outside to inside of the conductive core, and the difference of the interval is at least 100 Ω / m.

[0014] In some embodiments, the conductivity of the conductor shielding layer away from the conductor is smaller than the conductivity of the insulation shielding layer away from the conductor.

[0015] In some embodiments, the conductive fillers in the conductor shielding layer and the insulation shielding layer are at least one of conductive carbon black, graphene, carbon nanotubes, nano silver wires or nano copper.

[0016] Compared with the prior art, the application has the beneficial effects that: in the application, the conductor shielding layer is arranged to be close to the insulating layer in a structure in which the conductivity decreases continuously, so that the interface where the conductor shielding layer contacts the insulating layer prevents the accumulation of electric charges at the interface, greatly optimizing the electric field distribution between the conductor shielding layer and the insulating shielding layer; similarly, the insulating shielding layer is arranged to gradually increase in the direction away from the insulating layer, optimizing the interface electric field between the insulating layer and the insulating shielding layer, and quickly guiding the electric charges at the interface of the insulating layer to the insulating shielding layer, preventing the generation of partial discharge.

[0017] In order to make the above-mentioned purposes, features and advantages of the application more obvious and easy to understand, the following preferred embodiments are described in detail below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0019] Figure 1 A structural schematic diagram of a high-voltage three-core submarine cable of the application is shown; Figure 2 A structural schematic diagram of a conductor core of the application is shown; Figure 3 A structural schematic diagram of an insulating shielding system of the application is shown; Figure 4 A structural schematic diagram of a conductor shielding structure of the insulating shielding system of the application is shown; Figure 5 A structural schematic diagram of an insulating shielding of the insulating shielding system of the application is shown; Figure 6 Another structural schematic diagram of an insulating shielding of the insulating shielding system of the application is shown; Figure 7 A structural schematic diagram of a composite armored shielding layer of the application is shown; Figure 8 Another structural schematic diagram of a composite armored shielding layer of the application is shown; Figure 9 Another structural schematic diagram of a composite armored shielding layer of the application is shown; Figure 10 Another structural schematic diagram of a composite armored shielding layer of the application is shown; Figure 11 Another structural schematic diagram of a composite armored shielding layer of the application is shown; Figure 12 Another structural schematic diagram of the composite armored shielding layer in the application is shown. Figure 13 Another structural schematic diagram of the composite armored shielding layer in the application is shown. Figure 14 Another structural schematic diagram of the composite armored shielding layer in the application is shown. Figure 15 Another structural schematic diagram of the high-voltage three-core submarine cable in the application is shown.

[0020] In the figure: 1-conductive core, 11-conductor, 12-conductor shielding layer, 13-insulating layer, 14-insulating shielding layer, 141-matrix, 142-first braided layer, 143-second braided layer, 144-third braided layer, 15-metal sheath, 2-filling strip, 3-optical fiber unit, 4-water-blocking layer, 5-inner sheath, 6-composite armored shielding layer, 61-matrix, 62-magnetic conductive layer, 631-first layer of metal wires, 632-second layer of metal wires, 633-third layer of metal wires, 64-tensile-resistant fiber, 65-bonding strip, 634-fourth braided layer, 635-fifth braided layer, 636-sixth braided layer, 637-conductive particles, 621-first magnetic conductive strip, 622-second magnetic conductive strip, 623-magnetic conductive particles, 7-outer sheath, 8-reinforcing fiber layer, σ-conductivity, μ-magnetic permeability. DETAILED DESCRIPTION

[0021] The term "comprising" in the description of the application is synonymous with "including" or "containing" or "characterized by" and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps.

[0022] It should be noted that similar reference numerals and letters refer to similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings, in addition, the terms "first", "second", "third" and the like are only used to distinguish description, and cannot be understood as indicating or implying relative importance. The technical solutions in the embodiments of the application will be described clearly and completely in the following with reference to the drawings of the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0024] The present application will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0025] Example 1 This application provides a high-voltage three-core submarine cable. As in Example 1 of this embodiment, a high-voltage three-core submarine cable, such as Figure 1 As shown, it includes, from the inside out, a cable core, a water-blocking layer 4, an inner sheath 5, a composite armored shielding layer 6, and an outer sheath 7.

[0026] The cable core includes at least one conductive core 1, such as Figures 2-3 As shown, the conductive core 1 includes a conductor 11, an insulation system, and a metal sheath 15. The insulation system includes a conductor shielding layer 12, an insulation layer 13, and an insulation shielding layer 14. In the insulation system, the conductor shielding layer 12 and the insulation shielding layer 14 have bidirectionally gradually changing conductivity relative to the insulation layer 13. Specifically, the conductivity σ of the conductor shielding layer 12 gradually decreases from the inside to the outside in the radial direction of the conductive core 1; the conductivity σ of the insulation shielding layer 14 gradually decreases from the outside to the inside in the radial direction of the conductive core 1. That is, the conductivity gradient directions of the conductor shielding layer 12 and the insulation shielding layer 14 are opposite.

[0027] Due to minute defects in the manufacturing process or abrupt changes in the conductivity of materials, micropores or charge concentrations may occur at the interface, leading to partial discharge. Preventing partial discharge at the interface between the insulated wire and the conductor shield 12 and the insulation shield 14 is one of the core objectives in the design, manufacturing, installation, and operation and maintenance of high-voltage submarine cables. By setting the conductor shield 12 to a structure with continuously decreasing conductivity σ, the interface between the conductor shield 12 and the insulation layer 13 is designed to prevent charge accumulation at the interface, significantly optimizing the electric field distribution between the conductor shield 12 and the insulation shield 14. Similarly, setting the insulation shield 14 to have a conductivity σ that gradually increases away from the insulation layer 13 optimizes the electric field between the insulation layer 13 and the insulation shield 14, and can quickly draw the charge at the interface of the insulation layer 13 into the insulation shield 14, preventing the occurrence of partial discharge.

[0028] In the embodiment, the conductor shielding layer includes a base 141, and conductive fillers distributed in the base 141, the base 141 is a resin material, and the conductive fillers can be at least one of conductive carbon black, graphene, carbon nanotubes, nano silver wires, or nano copper. The filling proportion of the conductive fillers in the base 141 material decreases from inside to outside, so as to realize that the conductivity σ of the conductor shielding layer 12 decreases continuously from inside to outside in the radial direction of the conductive core 1, as shown in Figure 4 FIG. 5, the arrow direction is the increasing direction of the conductivity. The continuous decrease of the conductive fillers in the base 141 can ensure the continuous change of the potential of the conductor shielding layer 12, form a smooth electric field transition, improve the shielding effect of the conductor shielding layer, and optimize the interface performance with the insulating layer 13. Compared with the layer-by-layer wrapping structure of the semi-conductive shielding tape with different potentials, the conductor shielding layer 12 of the present application does not have gaps caused by wrapping, avoiding the partial discharge caused by the wrapping gap, and the conductor shielding layer 12 of the present application uses the base 141 as a medium and adopts an extrusion process, which ensures the zero-gap contact between the conductor shielding layer 12 and the conductor 11, and at the same time ensures the roundness of the conductive core 1.

[0029] In some embodiments, the filling proportion of the conductive fillers gradually changes from 40% to 20% from inside to outside, so as to realize that the volume resistivity of the conductor shielding layer changes in any interval of 100 Ω / m-1000 Ω / m from inside to outside in the radial direction of the conductive core, and the difference of the interval is at least 100 Ω / m. The conductivity and the volume resistivity are inversely proportional, so as to realize that the conductivity σ of the conductor shielding layer 12 gradually decreases from inside to outside in the radial direction of the conductive core 1.

[0030] In the embodiment, the insulating shielding layer 14 includes a base 141, and conductive fillers and inorganic particles (not shown in the figure) are added in the base 141, the filling proportion of the conductive fillers in the base 141 increases from inside to outside, and the filling proportion of the inorganic particles decreases from inside to outside. The conductive fillers include at least one of conductive carbon black, graphene, carbon nanotubes, nano silver wires, or nano copper, and the inorganic fillers are, for example, alumina and boehmite.

[0031] By adding the gradient doping of the inorganic fillers, the distribution proportion of the conductive fillers in the base 141 can be controlled synchronously, and by adding the inorganic fillers, the conductor shielding layer 12 has higher thermal stability and mechanical strength, which further strengthens the protection of the internal insulating layer 13, the conductor shielding layer 12, and the conductor 11, and improves the pressure resistance of the conductive core 1.

[0032] Furthermore, in some embodiments, the conductive filler in the insulating shielding layer 14 is attached to the fibers to form conductive fibers. The insulating shielding layer 14 includes multiple braided layers formed of conductive fibers, with the matrix 141 and inorganic particles filling the pores between the braided layers. The multiple braided layers formed of conductive fibers are at least two layers. The conductive fiber braided layers make it easier to control the gradient ratio of the conductive filler and also increase the tensile strength of the insulating shielding layer 14.

[0033] Furthermore, in some embodiments, the conductive fibers in each layer of the insulating shielding layer 14 have the same conductivity σ, but the braiding density of the braided layers gradually decreases from the outside to the inside. Since the conductive fibers have the same conductivity σ, the pore size of the braided layers is controlled by gradually varying the braiding density. The higher the pore density of the braided layers, the higher the filling ratio of the matrix 141 material and inorganic materials, and the lower the corresponding conductivity σ; conversely, the lower the pore density of the braided layers, the higher the filling ratio of the conductive filler, and the higher the corresponding conductivity σ.

[0034] Specifically, such as Figure 5 As shown, the insulating shielding layer 14 includes a substrate 141, inorganic particles, and multiple braided layers formed by conductive fibers. The braided layers consist of three layers: a first braided layer 142, a second braided layer 143, and a third braided layer 144, arranged sequentially near the insulating layer 13. The conductive fibers used in the first braided layer 142, the second braided layer 143, and the third braided layer 144 have the same conductivity σ. The density of the first braided layer 142 is greater than that of the second braided layer 143, and the density of the second braided layer 143 is greater than that of the third braided layer 144. By gradually decreasing the braiding density of the braided layers from the outside in, the conductivity σ of the insulating shielding layer 14 decreases as it approaches the insulating layer 13, thereby reducing the potential jump between the insulating layer 13 and the insulating shielding layer 14 and preventing partial discharge between them.

[0035] Furthermore, in some embodiments, the conductive fibers in each layer of the insulating shielding layer 14 have the same braiding density, but the conductivity σ of the conductive fibers in each braided layer gradually decreases in the direction closer to the cable core. For example... Figure 6 As shown, the insulating shielding layer 14 includes a substrate 141, inorganic particles, and multiple braided layers formed of conductive fibers. The braided layers consist of three layers: a first braided layer 142, a second braided layer 143, and a third braided layer 144, sequentially arranged near the insulating layer 13. The braiding density of the first braided layer 142, the second braided layer 143, and the third braided layer 144 is the same. The conductivity σ of the conductive fibers used in the first braided layer 142 is greater than that of the conductive fibers used in the second braided layer 143, and the conductivity σ of the conductive fibers used in the second braided layer 143 is greater than that of the conductive fibers used in the third braided layer 144.

[0036] By selecting the concentration of the conductive fiber from different conductive fillers, the conductivity σ of each layer of the braided layer formed by the conductive fiber is controlled, so as to control the potential gradient of the insulating shielding layer 14. At the same time, since the braiding density of the braided layer is the same, only different conductive fibers need to be arranged in different layers, which reduces the complexity of the production process.

[0037] In some embodiments, the conductivity σ of the conductive fiber of each braided layer gradually decreases in the direction close to the cable core, and at the same time, the braiding density of the braided layer decreases to meet the requirement of the conductivity σ gradient.

[0038] In some embodiments, the conductivity σ of the conductor shielding layer 12 away from the conductor 11 is smaller than the conductivity σ of the insulating shielding layer 14 away from the conductor 11. The trend of continuous attenuation of the electric field from the conductive body shielding layer to the metal sheath 15 is ensured, the outside electric field is quickly introduced into the insulating layer 13, and at the same time, the ground current of the metal sheath 15 is prevented from penetrating the insulating shielding layer 14, thereby reducing the eddy current loss. The conductivity is inversely proportional to the volume resistivity, and in some embodiments, the volume resistivity of the insulating shielding layer 14 changes in any interval of 100 Ω / m-500 Ω / m in the direction from the outside to the inside of the conductive core, and the difference between the intervals is at least 100 Ω / m.

[0039] Specifically, in some embodiments, the volume resistivity of the conductor shielding layer 12 in the gradual change interval in the direction from the inside to the outside of the cable core is 400 Ω / m-500 Ω / m, and the volume resistivity of the insulating shielding layer 14 in the gradual change interval in the direction from the outside to the inside of the cable core can be 300 Ω / m-400 Ω / m. In some embodiments, if the volume resistivity of the conductor shielding layer 12 in the gradual change interval in the direction from the inside to the outside of the cable core is in any interval of 1000 Ω / m-600 Ω / m, then the volume resistivity of the insulating shielding layer 14 in the gradual change interval in the direction from the outside to the inside of the cable core can be in any interval of 100 Ω / m-500 Ω / m.

[0040] The base body 141 is a cross-linked polyethylene material.

[0041] The cable core further comprises a filler strip 2 and an optical fiber unit 3, the filler strip 2 is arranged between adjacent conductive cores 1, and the optical fiber unit 3 is arranged in the filler strip 2.

[0042] A composite armor shielding layer 6 is arranged between the inner sheath 5 and the outer sheath, the composite armor shielding layer 6 comprises a matrix 61, and an electrically conductive material and a magnetically conductive material arranged in the matrix 61, the electrically conductive material is arranged on the side of the composite armor shielding layer 6 close to the cable core, and the magnetically conductive material is arranged on the side of the composite armor shielding layer 6 away from the cable core; wherein the electrical conductivity σ of the composite armor shielding layer 6 gradually decreases in the direction away from the cable core; the magnetically conductive material is a non-conductive material, and the magnetic permeability μ of the side of the composite armor shielding layer 6 away from the cable core is greater than the magnetic permeability μ of the side close to the cable core.

[0043] The composite armor shielding layer 6, the electrically conductive material is arranged on the side of the composite armor shielding layer 6 close to the cable core, and the magnetically conductive material is arranged on the side of the composite armor shielding layer 6 away from the cable core, not only has good tensile property and wear resistance, but also has good shielding effect on the internal high-frequency magnetic field and the external low-frequency magnetic field, realizes bidirectional shielding of the internal induced current and the external interference magnetic field, and greatly reduces the loss of the submarine cable.

[0044] In some embodiments, the magnetically conductive material is at least one of ferrite or a permanent magnet, and is a coating arranged on the side away from the cable core, the coating has a certain thickness and forms a magnetically conductive layer 62. The magnetically conductive layer 62 is on the outer surface of the composite armor shielding layer 6, not only has good electromagnetic shielding function, but also has excellent corrosion resistance and wear resistance.

[0045] The electrically conductive material is at least one of copper, aluminum, tin, nickel-based alloy and steel wire, and the magnetically conductive material is at least one of ferrite or a permanent magnet.

[0046] In some embodiments, the electrically conductive material forms metal wires, and the metal wires are arranged in at least two layers.

[0047] As Figure 7As shown, the composite armor shielding layer 6 includes a matrix 61, a plurality of layers of metal wires arranged in the matrix 61, and a magnetic conductive layer 62 located on the outer surface of the matrix 141. Specifically, the metal wires are 3 layers, and in the direction away from the cable core, the first layer of metal wires 631, the second layer of metal wires 632 and the third layer of metal wires 633 are arranged in turn, each of which is made of a material with different electrical conductivity σ, wherein the electrical conductivity σ of the first layer of metal wires 631 is greater than that of the second layer of metal wires 632, and the electrical conductivity σ of the second layer of metal wires 632 is greater than that of the third layer of metal wires 633. The design of gradually reducing the electrical conductivity σ in the direction away from the cable core can quickly introduce the induced current of the cable core into the composite armor shielding layer 6, thereby avoiding the occurrence of partial discharge, greatly improving the insulation performance of the submarine cable, and improving the stability and safety of the submarine cable operation. In this embodiment, the diameters of the first layer of metal wires 631, the second layer of metal wires 632 and the third layer of metal wires 633 are the same, and in some other embodiments, the diameters of the first layer of metal wires 631, the second layer of metal wires 632 and the third layer of metal wires 633 decrease in turn in the direction away from the cable core.

[0048] In some embodiments, the metal wires of different layers are made of the same material, the diameter of the inner layer of metal wires is greater than that of the adjacent outer layer of metal wires, and the outer layer of metal wires is further provided with the tensile-resistant fibers 64. As shown, Figure 8 As shown, the composite armor shielding layer 6 includes a matrix 61, a plurality of layers of metal wires arranged in the matrix 61, and a magnetic conductive layer 62 located on the outer surface of the matrix 141. Specifically, the metal wires are 2 layers, and in the direction away from the cable core, the first layer of metal wires 631 and the second layer of metal wires 632 are arranged in turn, and the diameter of the first layer of metal wires 631 is greater than that of the second layer of metal wires 632. The second layer of metal wires 632 is further provided with the tensile-resistant fibers 64, and preferably, the tensile-resistant fibers 64 are Kevlar fibers. By setting the diameters of the metal wires, the electrical conductivity σ of the inner and outer layers of metal wires is changed, and the greater the diameter, the higher the electrical conductivity σ. Further, by arranging the tensile fibers between the outer layers of metal wires, the electrical conductivity σ of the outer layers of metal wires can be adjusted, the tensile-resistant performance of the armor strength can be improved, and the weight of the submarine cable can be reduced.

[0049] Further, adhesive bands 65 can be designed between each layer of metal wires, as shown, Figure 9 The adhesive bands 65 can apply radial force to the inner layer of metal wires to tightly arrange the inner layer of metal wires, thereby avoiding dislocation of the outer layer of metal wires during the twisting process.

[0050] In some embodiments, the conductive material is a woven layer formed by conductive fibers, and the woven layer includes at least 2 layers.

[0051] Furthermore, in some embodiments, the conductivity σ of the materials of the different braided layers decreases in the direction away from the cable core in the composite armor shielding layer 6, and the braiding density of each braided layer can be the same or different. For example... Figure 10 As shown, the composite armor shielding layer 6 includes a fourth braided layer 634, a fifth braided layer 635, and a sixth braided layer 636. The conductivity σ of the fourth braided layer 634 is greater than that of the fifth braided layer 635, and the conductivity σ of the fifth braided layer 635 is greater than that of the sixth braided layer 636. In this embodiment, the braiding density of the fourth braided layer 634 and the fifth braided layer 635 is the same, both greater than that of the sixth braided layer 636. In other embodiments, the densities of the fourth braided layer 634, the fifth braided layer 635, and the sixth braided layer 636 can decrease sequentially. The potential gradient within the composite armor shielding layer 6 can be controlled simultaneously by the conductivity σ of the conductive fibers and the braiding density.

[0052] In some other embodiments, the different braided layers are made of the same material, and the braiding density of each braided layer in the composite armor shielding layer 6 gradually decreases in the direction away from the cable core. For example... Figure 11 As shown, the composite armor shielding layer includes a fourth braided layer 634 and a fifth braided layer 635. The conductive fibers used in the fourth braided layer 634 and the fifth braided layer 635 have the same conductivity σ, but the braiding density of the fourth braided layer 634 is greater than that of the fifth braided layer 635, thereby reducing the conductivity σ of the composite armor shielding layer 6 in the direction away from the cable core.

[0053] In some embodiments, the permeability μ of the composite armored shielding layer 6 gradually decreases in the direction near the cable core. Specifically, magnetically conductive material forms magnetic strips, which include at least two layers. The number of magnetic strips in the composite armored shielding layer 6 gradually decreases in the direction near the cable core, thereby causing the permeability μ of the composite armored shielding layer 6 to gradually decrease in the direction near the cable core.

[0054] In the direction near the cable core, the magnetic strips can be arranged alternately with at least one of the tensile fibers or conductive materials. For example, when the conductive material is metal wire, the magnetic strips near the cable core are arranged alternately with the metal wires away from the cable core, or the magnetic strips near the cable core are arranged alternately with the metal wires away from the cable core and the tensile fiber 64. As another example, when the conductive material is conductive particles 637, the magnetic strips near the cable core are embedded in the conductive particles 637.

[0055] like Figure 12As shown, the composite armored shielding layer 6 includes a matrix 61, first magnetic conductive strips, second magnetic conductive strips, a first layer of metal wires 631, and a second layer of metal wires 632. The number of the first magnetic conductive strips is greater than the number of the second magnetic conductive strips, and the number of the first layer of metal wires 631 is greater than the number of the second layer of metal wires 632. The second magnetic conductive strips are arranged at intervals from the second layer of metal wires 632. The interval number can also be selected according to electromagnetic shielding requirements. For example, in the case of more external interference, the interval number of the second magnetic conductive strips from the second layer of metal wires 632 is 1, that is, the number of the second layer of metal wires 632 is higher than the number of the second magnetic conductive strips. When the shielding of internal induced current is required to be strong, the interval number of the second layer of metal wires 632 is 2 or more, so that the number of the second layer of metal wires 632 is higher than the number of the second magnetic conductive strips.

[0056] In some other embodiments, when the number of layers of metal wires is 3, the second magnetic conductive strips of the composite armored shielding layer 6 can also be arranged at intervals from the third layer of metal wires 633 and the tensile-resistant fibers 64. In this embodiment, the electrical conductivity σ of each layer of metal wires can be the same or different, and the diameter of the metal wires can also gradually decrease in the direction away from the cable core of the composite armored shielding layer 6. Figure 13 As shown, the composite armored shielding layer 6 includes a matrix 61, and first magnetic conductive strips, second magnetic conductive strips, a first layer of metal wires 631, a second layer of metal wires 632, and a third layer of metal wires 633 wrapped in the matrix 61. The tensile-resistant fibers 64 are arranged at intervals between the second layer of metal wires 632. Specifically, one tensile-resistant fiber 64 is arranged every two second layer of metal wires 632, and one second magnetic conductive strip and one tensile-resistant fiber 64 are arranged at intervals between the third layer of metal wires 633. Through this arrangement, the electrical conductivity σ can be gradually decreased in the direction away from the cable core of the composite armored shielding layer 6, and the magnetic permeability μ can be gradually decreased in the direction close to the cable core of the composite armored shielding layer 6. The induced current and the induced magnetic field can be quickly guided into the composite armored shielding layer 6 to the greatest extent, and bidirectional shielding can be achieved.

[0057] In this embodiment, the materials of each layer of metal wires are the same, and the electrical conductivity σ is reduced by decreasing the diameter and number of the metal wires in the direction away from the cable core of the composite armored shielding layer 6. In some other embodiments, different metal materials can be used for each layer of metal wires, and the diameter and number of each layer of metal wires can be adjusted as needed.

[0058] In some embodiments, the conductive material is a conductive particle 637 formed of at least one of copper, aluminum, tin, and nickel-based alloy. The filling ratio of the conductive particles 637 gradually decreases in the direction away from the cable core of the composite armored shielding layer 6.

[0059] In some embodiments, the magnetic conductive material is formed into magnetic conductive particles 623 by any one of ferrite or permanent magnet, and the filling ratio of the magnetic conductive particles 623 gradually decreases in the direction of the cable core, so that the magnetic permeability μ of the composite armor shielding layer 6 gradually decreases in the direction of the cable core.

[0060] As shown in Figure 14 The composite armor shielding layer 6 includes conductive particles 637 and magnetic conductive particles 623, the filling ratio of the conductive particles 637 gradually decreases in the direction away from the cable core, the filling ratio of the magnetic conductive particles 623 gradually decreases in the direction of the cable core, and tensile-resistant fibers 64 are further arranged at the mixing position of the conductive particles 637 and the magnetic conductive material, so as to increase the tensile strength of the composite shielding layer.

[0061] Further, a reinforcing fiber layer 8 can be further arranged outside the composite armor shielding layer 6, as shown in Figure 15 to further improve the strength of the submarine cable.

[0062] The matrix 61 is any one of epoxy resin or polyethylene.

[0063] The outer sheath 7 is made of high-density polyethylene or polyethylene.

[0064] The above has introduced the embodiments of the present application in detail, and the principle and implementation mode of the present application are described by applying specific examples; the above embodiment is only used to help understand the method of the present application and its core idea; at the same time, for the general technical personnel in the art, according to the idea of the present application, the specific implementation mode and application range will be changed, and the above description should not be understood as the limitation of the present application.

Claims

1. A high voltage three core submarine cable comprising a cable core, a water barrier layer, an inner sheath, an armour layer and an outer sheath, the cable core comprising at least one electrically conductive core, the electrically conductive core comprising a conductor and an insulation system provided outside the conductor, the insulation system comprising a conductor screen, an insulation layer and an insulation screen, characterized in that, The conductive shielding layer has gradually decreasing conductivity from inside to outside in the radial direction of the conductive core.

2. A high voltage three core submarine cable according to claim 1, characterized in that The conductive shielding layer comprises a base and conductive fillers distributed in the base, and the filling proportion of the conductive fillers gradually decreases from inside to outside in the base material.

3. A high voltage three core submarine cable according to claim 2, characterized in that The volume resistivity of the conductive shielding layer changes in any interval of 100-1000 Ω / m from inside to outside of the conductive core, and the difference of the interval is at least 100 Ω / m.

4. The high-voltage three-core submarine cable according to claim 1, characterized in that, The insulating shielding layer comprises a base, and conductive fillers and inorganic particles are added in the base, the filling proportion of the conductive fillers gradually increases from inside to outside in the base material, and the inorganic particles gradually decrease from inside to outside.

5. A high voltage three core sea cable according to claim 4, c h a r a c t e r i s e d in that The conductive fillers in the insulating shielding layer are attached to fibers to form conductive fibers, and the insulating shielding layer comprises multiple layers of braided layers formed by the conductive fibers, and the base and the inorganic particles are filled between the pores of the braided layers.

6. A high voltage three core submarine cable according to claim 5, characterised in that, The conductive fibers in each layer of the insulating shielding layer have the same conductivity, but the braiding density of the braided layers gradually decreases from outside to inside.

7. A high voltage three core sea cable according to claim 5, c h a r a c t e r i s e d in that The conductive fibers in each layer of the insulating shielding layer have the same braiding density, but the conductivity of the conductive fibers of each braided layer gradually decreases from outside to inside.

8. The high-voltage three-core submarine cable according to claim 4, characterized in that, The volume resistivity of the insulating shielding layer changes in any interval of 100-500 Ω / m from outside to inside of the conductive core, and the difference of the interval is at least 100 Ω / m.

9. The high-voltage three-core submarine cable according to claim 1, characterized in that, The conductivity of the conductive shielding layer away from the conductor is less than that of the insulating shielding layer away from the conductor.

10. The high-voltage three-core submarine cable according to claim 1, characterized in that, The conductive fillers in the conductive shielding layer and the insulating shielding layer are at least one of conductive carbon black, graphene, carbon nanotube, nano silver wire or nano copper.

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