Dynamic power cable with a copper-tin alloy waterproofing layer

Abstract

To provide dynamic power cables, particularly but not limited to offshore floating applications, such as those for multi-unit wind power plants. [Solution] A cable core (110) comprising a conductor (115) surrounded by an insulating system (200); A metal layer (120) in the form of a metal foil (121) wrapped around a cable core wire (110) along the longitudinal direction (A), the metal layer (120) being made of a copper-tin alloy, with a tin content of 0.5 to 14 mass% relative to the total mass of the alloy, A dynamic power cable (100) including is provided.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to dynamic power cables, particularly but not limited to dynamic power cables useful for offshore floating applications, such as collective wind farms.

BACKGROUND ART

[0002] The power cable can be, for example, a high-voltage or extra-high-voltage power cable. As used herein, the expression "high voltage" (HV) refers to voltages of 30 kV and above, while the expression "extra high voltage" (EHV) refers to voltages of 300 kV and above. A "dynamic cable" is a cable used in floating offshore applications, which is subjected to various dynamic loads induced by ocean waves, unlike "static" cables that do not fatigue during use. Typically, power cables, especially HV or EHV power cables, include at least one cable core, which is usually formed by a conductive metal conductor covered with an insulation system. The insulation system can be sequentially formed by an inner polymer semiconducting layer, an intermediate polymer insulation layer and an outer polymer semiconducting layer. Next, the insulation system is surrounded by a metal shield, usually generally made of steel or copper, and a polymer sheath that can be semiconducting or insulating. When the power cable includes more than one cable core, for example three cable cores, the power cable may also include filler material or shaped filling elements between the cores. The metal shield may be surrounded by a bedding layer, which may then be surrounded by an armor.

[0003] When a power cable is installed in a wet or potentially wet environment, for example under water or underground, the cable core should be protected from ingress of moisture or water that may lead to insulation breakdown. For this purpose, in submarine power cables or high-voltage (HV) or extra-high-voltage (EHV) underground power cables, the metal shield is typically sealed and also acts as a water barrier layer surrounding the cable core of the power cable, blocking water ingress during cable laying and operation. A waterproof layer can be sealed by wrapping a foil-like waterproof layer material vertically around the cable core. The edges of the foil can be butted together or overlapped and bonded by TIG (tungsten inert gas) or laser welding. The foil can be 0.1 mm to 2 mm thick, and typically, when the foil thickness is greater than 0.4 mm, it can be optionally corrugated to improve the material's performance.

[0004] For dynamic cables, it is known that pure copper (Cu-OF, i.e., oxygen-free copper, or Cu-HCP, i.e., high-purity copper) or stainless steel (especially AISI 316L) is used for the shielding / waterproofing layer. These metals are suitable for this application due to their easy weldability, cold formability, and fatigue and corrosion resistance, which are important characteristics for dynamic cable applications. Pure copper is more commonly used due to its favorable electrical resistivity and sufficient weldability. However, the mechanical properties of pure copper are not entirely satisfactory, resulting in lower durability in dynamic applications. Furthermore, the low electrical resistivity of copper can cause current loss. On the other hand, stainless steel (AISI 316L) has good mechanical properties, but its poor conductivity is undesirable in the event of a short circuit. Different copper alloys can also be used for the shielding / waterproofing layers of power cables. See, for example, European Patent No. 3438993, which discloses the use of a copper-nickel alloy in submarine dynamic power cables, and European Patent Application Publication No. 3786982, which discloses a CuNiSi alloy for the inner sheath of submarine power cables. European Patent Application Publication No. 2706539 relates to a cable useful for underwater applications that conducts electricity and has a waterproof layer made of copper alloy selected from copper and nickel; copper and beryllium; copper, zinc and aluminum; and alloys containing copper and zinc. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] European Patent Application Publication No. 3786982 [Patent Document 2] European Patent Application Publication No. 2706539 [Overview of the project]

[0006] The applicant faces the challenge of providing power cables with improved mechanical properties, specifically fatigue properties which are crucial for dynamic applications, but which have a shielding / waterproofing layer with higher resistivity than pure copper, particularly for use in offshore floating wind farms. For that purpose, the applicant is considering using a copper-tin alloy. Specifically, the applicant has found that copper alloys with a tin content of 0.5 to 14 mass% exhibit improved mechanical properties (relating to tensile strength and yield strength) and fatigue properties compared to pure copper, while simultaneously maintaining electrical properties suitable for electrical shielding. The alloys also exhibit weldability by various techniques (TIG-tungsten inert gas-, MIG-metal inert gas-, laser) and good cold deformability, making them excellent intermediates for the specified applications even when the shielding / waterproofing layer is corrugated, and suitable for both butt welding and overlap edge techniques.

[0007] According to the first aspect, this disclosure is: • At least one cable core containing a conductor surrounded by an insulating system; A metal foil-like metal layer wrapped around at least one cable core wire along its longitudinal direction, made of a copper-tin (Cu-Sn) alloy, with a tin content of 0.5 to 14% by mass relative to the total mass of the alloy, This relates to dynamic power cables, including those mentioned above. In one embodiment, the tin content is 0.5 to 10%. For example, the tin content is 1 to 7% by mass relative to the total mass of the alloy. The Cu-Sn alloys of this disclosure may contain small amounts of impurities. These impurities may include lead, manganese, iron, zinc, and other metals. These impurities may be present because they are typically too difficult or too costly to remove during the manufacturing of the metal or alloy. These impurities may be present in amounts ranging from 0.0001%, 0.001%, 0.005%, or 0.01% to 0.1%, 0.5%, 1%, 2%, or 4% (mass / mass). It will be understood that such amounts of impurities may be present in the alloys of this disclosure without affecting or deviating from the scope of the disclosure. The Cu-Sn alloys disclosed herein may have an ultimate tensile strength of 250 MPa to 550 MPa, calculated in accordance with ISO 6892-1:2009(E). The Cu-Sn alloy disclosed herein may have a fracture elongation of 15% to 50% calculated in accordance with ISO 6892-1:2009(E). The Cu-Sn alloys disclosed herein may have an electrical conductivity of 10%IACS (International Annealed Copper Standard) to 25%IACS. IACS is a standard established by the U.S. Department of Commerce in 1914. 100%IACS has an electrical conductivity of 58 × 10⁻¹⁰ at 20°C. 6 It is equivalent to S / m.

[0008] In one embodiment, the metal layer has a thickness of 0.1 to 2 mm. In one embodiment, the metal layer is corrugated. In one embodiment, the metal layer has a butt-welded edge. In an alternative embodiment, the metal layer has overlapping longitudinal edges bonded together with a binder. In one embodiment, the binder is based on a metal, such as copper. In one embodiment, the dynamic power cable includes, if the tin content is at least 8% by mass relative to the total mass of the alloy, a pure copper layer, such as a tape, braid, or wire, sandwiched between the cable core and the metal layer and in direct contact with the latter. In this specification and in the claims, “pure copper” means oxygen-free copper (Cu-OF) or high-purity copper (Cu-HCP). In either case, the pure copper according to this disclosure has an electrical conductivity of 98–100% IACS (International Annealed Copper Standard) at 20°C. The metal layer of the cable in this disclosure can function as both a water-blocking layer and an electrical shield.

[0009] The dynamic power cable relating to this disclosure may include one to three cable cores. Each cable core is surrounded by a corresponding metal layer relating to this disclosure. In this specification and in the claims, “insulating system” means an assembly of an internal semiconducting layer, an insulating layer, and an external semiconducting layer, from radially inward to outward. The layers of the insulating system are based on polymer materials. Generally, insulating systems are manufactured by co-extruding the aforementioned layers. In one embodiment, the cable core of the cable further includes at least one semiconducting water-swelled layer that is in direct contact with the outer semiconducting layer of the insulation system. In one embodiment, the semiconducting water-swelled layer is in direct contact with the metal layer. The semiconductive water-swelled layer may be wound in a spiral shape or formed as a tape lengthwise. In one embodiment, each cable core according to this specification may further include a discontinuous electrical shield surrounding the insulation system and located radially inward with respect to the water-blocking layer. The discontinuous electrical shield may be made of a conductive material and may be in the form of a wire, braid, rod, or spirally wound tape. If a discontinuous electrical shield is present, each cable core of the cable may include two semiconducting water-swelled layers in direct contact with the shield, one located radially inward with respect to the discontinuous electrical shield and the other located radially outward and in direct contact with the metal layer. In one embodiment, the metal layer is surrounded and in direct contact with a semiconductive inner sheath, which can be the outermost layer of the cable.

[0010] The dynamic cable according to the present disclosure may further comprise at least one armoring layer surrounding the metal layer, for example two armoring layers. The armoring layer can be made of metal rods or wires such as steel, or high-tensile polymer bundles such as aramid filament bundles. The at least one armoring layer surrounds the metal layer, and consequently surrounds the corresponding cable core. For example, a cushion layer made of polyethylene may be interposed between the metal layer and the armor. When the dynamic cable according to the present disclosure comprises at least one armoring layer, a jacket surrounding the at least one armoring layer is present. The jacket can be made of extruded polyethylene, for example high-density polyethylene (HDPE). When present, the jacket is the outermost layer of the present cable.

[0011] For the purposes of the following specification and claims, unless otherwise indicated, all numbers expressing quantities, amounts, percentages and the like are to be understood as being modified in all instances by the term "about". Moreover, all ranges include any combination of the disclosed maximum and minimum points, and any intermediate ranges therein, whether or not such intermediate ranges are specifically enumerated herein. Furthermore, the terms "a" and "an" are utilized to describe elements and components of the present disclosure. This is merely for convenience and indicates the general meaning of the present disclosure. This description should be construed to include one or at least one, and the singular form also includes the plural unless the contrary is clearly indicated. "Insulating layer" means a layer made of a material having an electrical conductivity of 10 -16 to 10 -14 S / m. "Semiconducting layer" means a layer made of a material having an electrical conductivity of 10 -1 to 10 S / m. A "dynamic" cable means a cable used for connecting floating offshore platforms, for example collective wind power plants, and is therefore used underwater and subjected to dynamic loads (fatigue) originating from the floating platforms.

[0012] At least one of the above aspects of the present disclosure can be implemented by arbitrarily combining one or more of the present embodiments. Further features will become apparent from the detailed description set forth below with reference to the accompanying drawings. [Brief Description of the Drawings]

[0013] [Figure 1] Figure 1 is a schematic perspective cross-sectional view of a dynamic power cable according to an embodiment of the present disclosure. [Figure 2] Figure 2 is a schematic cross-sectional view of a dynamic power cable according to a different embodiment of the present disclosure. [Figure 3] Figure 3 shows the metal foil of the dynamic power cable in Figures 1 to 2 before being wound around the core wire. [Mode for Carrying Out the Invention]

[0014] Referring to the drawings, the dynamic power cable 100 according to the present disclosure is schematically represented. The dynamic power cable 100 according to the present disclosure can be either HV or EHV, for either AC or DC. The dynamic power cable 100 includes at least one cable core 110 extending along the longitudinal direction A. In the embodiment described in Figure 1, the dynamic power cable 100 includes one cable core 110, while in the embodiment of Figure 2, the cable 100 includes three cable cores 110 that are helically assembled with one another along the longitudinal axis A. In all embodiments, each cable core 110 includes a conductor 115 surrounded by an electrical insulation system 200. Each electrical insulation system 200 is continuously formed by an inner polymer semiconducting layer 210, a polymer insulation layer 220, and an outer polymer semiconducting layer 230. The dynamic power cable 100 includes a metal layer 120 in the form of a metal foil 121 that is longitudinally wound around the cable core 110. The discontinuous metal shield (not shown) is made of a conductive metal such as copper, aluminum, or a composite thereof, and is in the form of a wire, braid, or spirally wound tape. It is located around each insulating system 200 and can be located radially inward with respect to the metal layer 120.

[0015] A semiconductive water-swellable layer 135 (not shown in the cable of Figure 2) may be provided around the insulation system 200 or around all of the insulation systems 200 (below the discontinuous metal shield, if present). Thus, the power cable 100 includes the semiconductive water-swellable layer 135 which may be in direct contact with the metal layer 120. According to this specification, if present, the water-swellable layer 135 is part of the cable core wire 110. For example, the semiconductive water-swellable layer 135 may be a helically wound tape or a longitudinally wound foil. The semiconductive water-swellable layer 135 may be made of a water-swellable powder such as polyacrylate and a nonwoven fabric to which carbon black, for example, has been added. If a discontinuous metal shield is present, each cable core wire 110 may include two semiconductive water-swelled layers 135 that are in direct contact with the shield, one of which is located radially inward with respect to the discontinuous electrical shield and the other is located radially outward and is in direct contact with the metal layer 120. In the embodiment shown in Figure 1, the metal foil of the metal layer 120 has a welded portion 124 that joins its longitudinal edge. In the embodiment shown in Figure 2, the longitudinal edges of the metal layer 120 overlap each other and are joined together by the binder 123. In one embodiment, the binder 123 may be, for example, a polymer adhesive resin or a conductive metal such as copper. If the bonding layer 123 is a metal, it can be made of copper, for example, as reported in European Patent No. 4258294. If the bonding layer 123 is a polymer adhesive resin, it may be provided on overlapper edges and on the bonding layer 123, for example, as reported in European Patent No. 3069354, which includes a metal coating such as a copper coating.

[0016] The dynamic cable 100 in Figure 2 further includes fillers positioned in the spaces between the cable cores 110. The fillers can be made, for example, from an extruded polymer material, a polymer filament, or may be plastic inserts 111 having a substantially triangular cross-section, as described, for example, in European Patent Application Publication No. 3244423 (only one is shown, but there are actually three). The metal layer 120 is made of a copper-tin alloy in which the tin content is 0.5 to 14 mass% of the total mass of the alloy. In one embodiment, the tin content is 0.5 to 10% by mass relative to the total mass of the alloy. In one embodiment, the tin content is 1 to 7% by mass relative to the total mass of the alloy. The metal layer made of this alloy can withstand cold forming and welding (i.e., gas shielded arc welding and laser welding). The metal layer 120 can have a thickness of 0.1 to 2 mm. In one embodiment, the metal layer 120 has a thickness of 0.1 to 1.5 mm. In one embodiment, the metal layer 120 is corrugated. In one embodiment, the metal layer 120 is corrugated and has a thickness of more than 0.4 mm to 1.5 mm.

[0017] As already mentioned, the metal layers of this dynamic cable may have butt-welded edges or edges that are overlapped vertically and joined with a bonding agent 123. In one embodiment, the metal layer has butt-welded edges and a thickness of 0.4 to 1.5 mm. In one embodiment, the metal layers have overlapping edges bonded together with a binder, and have a thickness of 0.1 to 0.4 mm. In one embodiment, when the metal layer 120 has a tin content of at least 8% by mass relative to the total mass of the alloy, the dynamic power cable 100 of the present disclosure may include a pure copper layer (not shown) sandwiched between the cable core wire 110 and the metal layer 120 in direct contact with it. If a pure copper layer is present, it is positioned radially inward relative to the metal layer 120 and radially outward relative to the semiconducting water-swelled layer 135. In one embodiment, a pure copper layer may be placed between two water-swelled layers 135. The pure copper layer may be in the form of a tape, braid, or wire. The thickness of the pure copper layer is determined by the design of the entire cable and the metal layer and can be suitably selected by those skilled in the art.

[0018] In one embodiment, the dynamic power cable 100 of the present disclosure further includes at least one outer sheath 140. In the cable 100 of Figures 1 and 2, the outer sheath 140 is a single layer of wire which may be metal, polymer, or both. The outer sheath 140 is provided around the metal layer 120 and separated, in order, by an inner sheath 143 and a cushion layer 141. Both the inner sheath 143 and the cushion layer 141 may be made of polymer material, and in the case of the inner sheath, it may be made of polymer material to which a semiconducting material such as carbon black is optionally added. For example, a polyethylene jacket 142, such as HDPE, surrounds the outer layer 140 as the radially outermost layer. In other embodiments not shown, the power cable may be without an outer sheath. In this case, the outermost layer of the cable is an internal sheath 143, i.e., a polymer layer in direct contact with the metal layer 120 of the present disclosure. To ensure secure adhesion between the internal sheath 143 and the metal layer 120, an adhesive layer (not shown) can be sandwiched between the metal layer 120 and the internal sheath 143.

[0019] As shown in Figure 3, the metal layer 120 of this disclosure can be manufactured by winding the metal foil 121 longitudinally around the cable core wire 110. In one embodiment, the longitudinal edges 122 can be closed by butt welding using TIG or laser welding. In one embodiment, a metal protective strip can be provided on the power cable core wire 110 at a location substantially coinciding with the weld, as disclosed in European Patent No. 3792938. In another embodiment, the longitudinal edges 122 can be overlapped and bonded together with a binder 123. When the binder is dielectric (i.e., nonmetallic), a metal coating can be provided, for example, as disclosed in European Patent No. 3069354. According to this disclosure, the metal layer functions as an electrical shielding and water-blocking layer in the cable. The alloy disclosed herein allows the metal layer to withstand higher fatigue than pure copper and has high corrosion resistance, thus making it a good waterproof layer. At the same time, the alloy has conductivity suitable for electrical shielding. For electrical shielding, stainless steel layers such as AISI 316L, which has a conductivity of 2.3% IACS and is commonly used for waterproof layer applications, are unsuitable. [Examples]

[0020] Tests conducted by the applicant showed that metal layers made from this alloy have suitable conductivity, which is lower than that of pure copper (high-purity copper Cu-HCP or oxygen-free copper Cu-OF) but higher than that of stainless steel (stainless steel AISI 316L, conductivity: 2.3% IACS), and have substantially better mechanical properties than pure copper, particularly in ultimate tensile strength (Rm) and yield strength (Rsn). The measured mechanical properties in the table below are the ultimate tensile strength (Rm), yield strength (Rsn), and elongation at break (A) measured in accordance with ISO 6892-1:2009(E). 50mm ). Furthermore, the conductivity values ​​in the table below are shown as those measured under annealing treatment at 20°C.

[0021] In the table, Cu-HCP-A and Cu-HCP-B are high-purity copper; UNS (Unified Numbering System) C10300; Cu-OF-A and Cu-OF-B are oxygen-free copper; UNS C10200; CuSn0.20 is a Cu-Sn alloy containing 0.2 mass% tin; it is UNS C14410; CuSn4-A and CuSn4-B are two different tempered Cu-Sn alloys containing 4% by mass of tin; UNS C51100; CuSn5-A and CuSn5-B are two different tempered Cu-Sn alloys containing 5% by mass of tin; UNS C51000; CuSn6-A and CuSn6-B are two different tempered Cu-Sn alloys containing 6% by mass of tin; UNS C51900; CuSn8-A and CuSn8-B are two different tempered Cu-Sn alloys containing 8% by mass of tin; UNS C52100. asterisk( * The metals marked with ) are comparative metals. [Table 1]

[0022] Although the alloys described herein have a lower conductivity IACS than Cu-HCP-A / B, Cu-OF-A / B, and the comparative alloy CuSn0.20, they are sufficient for metal layers useful as electrical shielding for power cables such as high-voltage power cables. The low conductivity of these alloys is advantageous in that it reduces or eliminates current loss. In the case of CuSn8-A and CuSn8-B, which have a conductivity of 11%IACS, metal layers made from one of these alloys could be bonded to a pure copper sheet located radially inward. The alloys according to this disclosure have better overall mechanical properties than the comparative metals, making them suitable materials for the water-insulating layer of dynamic cables. With respect to pure copper (Cu-HCP-A / B and Cu-OF-A / B), when the ultimate tensile strength (Rm) is equivalent to that of the alloys according to this disclosure, the elongation at break (A 50mmThe break elongation (A) is significantly lower, and when bent or handled normally, the cable inevitably becomes brittle. Conversely, the break elongation (A) is lower. 50mm When ) is equivalent to the alloy of this disclosure, the ultimate tensile strength (Rm) is significantly lower, and the cable is inevitably unable to maintain tension. The same is true for the comparative alloy CuSn0.20 (whose tin content is outside the scope of this disclosure). In all of the alloys in the examples, the applicant found that they possessed very good cold formability (compared to pure copper), good ability to withstand gas-shielded arc welding and laser welding, and good corrosion resistance.

Claims

1. - At least one cable core wire (110) including a conductor (115) surrounded by an electrical insulation system (200); - A metal layer (120) in the form of a metal foil (121) wrapped around the cable core wire (110) along the longitudinal direction (A), the metal layer (120) being made of a copper-tin alloy, the tin content of which is 0.5 to 14% by mass relative to the total mass of the alloy, A dynamic power cable (100) including the above.

2. The dynamic power cable (100) according to claim 1, wherein the tin content is 0.5 to 10% by mass relative to the total mass of the alloy.

3. The dynamic power cable (100) according to claim 1, wherein the tin content is 1 to 7% by mass relative to the total mass of the alloy.

4. The dynamic power cable (100) according to claim 1, wherein the metal layer (120) has a thickness of 0.1 to 2 mm.

5. The dynamic power cable (100) according to claim 1, wherein the metal layer (120) is corrugated.

6. The dynamic power cable (100) according to claim 1, wherein the metal layer (120) has a butt welded edge (122).

7. The dynamic power cable (100) according to claim 1, wherein the metal layer (120) has overlapping longitudinal edges (122) bonded together with a binder (123).

8. The dynamic power cable (100) according to claim 7, wherein the binder (123) is made of metal.

9. The dynamic power cable (100) according to claim 1, wherein the tin content is at least 8% by mass of the total mass of the alloy, and the dynamic power cable (100) includes a pure copper layer sandwiched between the cable core wire (110) and the metal layer (120) and in direct contact with the metal layer (120).

10. A dynamic power cable (100) according to claim 1, comprising one to three cable cores (110), each cable core (110) being surrounded by a corresponding metal layer (120).

11. The dynamic power cable (100) according to claim 1, comprising a semiconducting water-swellable layer in direct contact with the metal layer (120).

12. The dynamic power cable (100) according to claim 1, comprising at least one outer layer (140) surrounding the metal layer (120).

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