Wet design hv cable

Abstract

The present invention relates to a wet-design high-voltage (HV) power cable comprising a cable core, wherein the cable core comprises an electrical conductor, and the electrical conductor is surrounded, in order, by an inner semiconducting layer, an insulating layer, and optionally an outer semiconducting layer. Furthermore, the present invention relates to a method for manufacturing a wet-design HV power cable. Furthermore, the present invention relates to an application of the wet-design HV power cable.

Description

Technology Field

[0001] The present invention relates to a wet-design high-voltage (HV) power cable comprising a cable core, wherein the cable core comprises an electrical conductor, an inner semiconducting layer, an insulating layer, and optionally an outer semiconducting layer surrounding the same in sequence. Furthermore, the present invention relates to a method for manufacturing a wet-design HV power cable. Furthermore, the present invention relates to an application of a wet-design HV power cable. Background Technology

[0002] Wet-design power cables are a type of electrical cable that does not have an impermeable moisture barrier layer around its insulation system. This design enables the cable to operate in environments where it may be exposed to moisture, such as underwater or wet conditions. Unlike dry-design cables, wet-design cables lack a sheath that forms a watertight seal, which means they do not have a complete barrier layer against moisture penetration.

[0003] These cables are commonly used in the medium voltage (MV) sector, including submarine cables for offshore wind farms and other underwater facilities. As an advantage, wet-design cables can be cost-effective due to their simpler structure, which does not require a metallic moisture barrier. Additionally, they offer excellent flexibility and mechanical performance, making them suitable for dynamic applications.

[0004] However, wet-design cables are associated with significant challenges in terms of electrical durability: one of the major challenges associated with this is the possibility of water treeing, a phenomenon in which moisture penetration leads to the formation of tree-like structures within the insulator, which can cause electrical degradation over time.

[0005] In the prior art, there is significant development activity to improve the electrical durability of wet-design cables that are not susceptible to water treeing. One such approach concerns improving the material of the insulation layer. For example, WO 2023 / 198762 A1 uses a specific polymer blend comprising a polyethylene-based copolymer and additional copolymers for such purposes.

[0006] However, this approach involves a comprehensive process for the manufacture of insulating materials. Furthermore, the accessibility of such materials is low. If the material for the insulating layer is selected from general-purpose materials, this is associated with advantageous effects. The problem to be solved

[0007] The object of the present invention is to provide a power cable configured with a wet design and capable of withstanding high voltage, wherein the insulating layer of the cable core is composed of a general-purpose material, thereby ensuring its availability. In particular, the power cable must be configured to withstand a voltage of 30 kV to 400 kV. Accordingly, the object of the present invention is to provide a wet-design HV power cable that provides high electrical strength and durability. means of solving the problem

[0008] The problem forming the basis of the present invention is solved by the features of claim 1. Accordingly, the first aspect of the present invention relates to a wet-design HV power cable comprising a cable core, wherein the cable core comprises an electrical conductor, said electrical conductor is surrounded in order by an inner semiconducting layer, an insulating layer, and optionally an outer semiconducting layer; said inner semiconducting layer comprises acetylene black within a polymer matrix of the inner semiconducting layer; said insulating layer comprises a polymer, said polymer being a non-blend polymer composed of an XLPE homopolymer, and said polymer matrix of the inner semiconducting layer comprises a copolymer composed of an olefin comonomer and a polar comonomer.

[0009] The term “wet design” power cable is understood within the scope of this application as follows: A wet design power cable is a type of electrical cable that does not have an impermeable moisture barrier layer around its insulation system. This design enables the cable to operate in environments where it may be exposed to moisture, such as underwater or wet conditions. Unlike dry design cables, wet design cables lack a sheath that forms a watertight seal, which means they do not have a complete barrier layer against moisture penetration.

[0010] Regarding electrical insulation, XLPE insulation layers are commonly used. Cross-Linked Polyethylene (XLPE) insulators in power cables are a type of insulating material used to improve the performance and durability of the cable. XLPE is manufactured by chemically or physically cross-linking polyethylene molecules, forming a three-dimensional network that enhances the thermal and mechanical properties of the material. These XLPE insulating materials are considered general-purpose materials. Their availability and processability represent the advantages of the material. The XLPE material is typically formed from linear polymers to which cross-linking is applied.

[0011] Cross-linked polyethylene (XLPE) is manufactured through a process that chemically bonds polymer chains within polyethylene, thereby improving its properties. As a brief overview of the method, the process begins with high-density polyethylene (HDPE) or low-density polyethylene (LDPE) as the base material. During or after the extrusion of polyethylene, crosslinking agents such as organic peroxides, silanes, or irradiation are introduced. These crosslinking agents initiate the crosslinking reaction. The polyethylene is extruded into a desired shape, such as a pipe or cable. The crosslinking agents cause the polymer chains to bond and form a three-dimensional network. This can be accomplished by the following: 1. Mixing organic peroxides with polyethylene and heating the mixture to initiate the crosslinking reaction. 2. Grafting a silane compound onto the polyethylene and completing the crosslinking using moisture. 3. Inducing crosslinking by exposing the polyethylene to high-energy radiation. The material typically undergoes curing using heat and moisture to complete the crosslinking process. This process produces materials that are more resistant to heat, chemicals, and stress, making them ideal for applications such as electrical insulation, plumbing, and industrial piping.

[0012] Although crosslinking formally creates units within the polymer that are distinct from units derived from monomers used in polymerization to form linear chains—that is, units that do not participate in the crosslinking reaction—XLPE is referred to as a homopolymer. Despite the fact that crosslinked polymers are referred to as homopolymers, within the scope of this application, the term “homopolymer” means a polymer comprising only a single type of repeating unit.

[0013] According to a first aspect of the present invention, the insulating layer comprises a polymer that is a non-blended polymer. Those skilled in the art will understand that while the insulating layer may include additional components, the insulating layer is non-blended with respect to the polymer phase. In other words, the feature “the insulating layer comprises a polymer that is a non-blended polymer” is understood to mean that the insulating layer comprises a polymer phase that is not a polymer blend or consists of only one polymer. Those skilled in the art will understand that the one polymer may have a polymer molecular weight distribution, so that distinct polymer molecules may still be used in the insulating layer. The term “one polymer” may be understood as “one type of polymer” or “one kind of polymer.” A non-blended polymer is a material whose physical properties can be reduced to that kind of polymer. The polymer is preferably an XLPE or LDPE homopolymer. This means that, in a preferred embodiment, the polymer is a non-blended polymer that is XLPE based on the homopolymer LDPE. Conversely, the term “polymer blend” is understood in the sense of materials science; that is, a polymer blend refers to a group of materials in which at least two polymers are blended together to create a new material with different physical properties.

[0014] Accordingly, the first aspect of the present invention relates to a wet-design HV power cable comprising a cable core, wherein the cable core comprises an electric conductor, said electric conductor is surrounded in order by an inner semiconducting layer, an insulating layer, and optionally an outer semiconducting layer; said inner semiconducting layer comprises acetylene black within a polymer matrix of the inner semiconducting layer; said insulating layer comprises a non-blend polymer or said insulating layer does not comprise a polymer blend.

[0015] These alternatives described in the preceding paragraph represent different expressions of the present invention. Instead of providing a power cable having an insulating layer comprising a polymer made of a homopolymer, the insulating layer may comprise a non-blend polymer, or as an alternative expression, the insulating layer may not comprise a polymer blend.

[0016] The use of a polymer phase composed of homopolymers, particularly XLPE, is associated with the advantageous effect of ensuring availability. Additional features combined with the homopolymer as the sole polymer component of the polymer phase contribute to making it possible to use power cables having such an insulating layer as wet-design power cables.

[0017] As an additional essential component, the cable core of the wet-design HV power cable comprises an internal semiconducting layer surrounding an electrical conductor. In the present invention, the term “semiconducting layer” is understood to mean a layer whose electrical conductivity is at least 1×10⁻⁹ S / m (Siemens per meter), preferably at least 1×10⁻³ S / m, and preferably less than 1×10³ S / m (at 25°C).

[0018] High-voltage cables feature an internal semiconducting layer as a conductor shielding layer for the following advantageous effects. This semiconducting layer contributes to improving the distribution of the electric field around the electric conductor. This reduces the risk of insulation breakdown and enhances the overall performance of the power cable. Additionally, the surface of the electric conductor may have irregularities, which can lead to the concentration of the electric field. The semiconducting layer mitigates these irregularities to ensure a more uniform electric field. This contributes to forming an equipotential surface around the conductor, which means that the voltage is distributed uniformly across the entire surface and reduces the risk of high-voltage stress points that could lead to insulation breakdown.

[0019] Essentially, the aforementioned internal semiconducting layer is advantageous for ensuring the safe and efficient operation of power cables by managing the electric field and protecting the insulation.

[0020] According to the present invention, the inner semiconducting layer comprises acetylene black within the polymer matrix of the inner semiconducting layer.

[0021] The aforementioned internal semiconducting layer and its constituent components and characteristics are particularly important in the wet-design HV power cable of the present invention. The electrical characteristics of the wet-design HV power cable, which are imparted by the characteristics of the insulation layer of the power cable—specifically, the characteristics of the non-blend polymer constituting the insulation layer—must be adjusted so that the cable is suitable as a wet-design HV power cable. While the use of general-purpose materials alone as the insulation layer does not sufficiently improve the desired electrical characteristics, additional characteristics influence the electrical characteristics, enabling the power cable to be constructed as a wet-design. These characteristics are realized by acetylene black within the internal semiconducting layer. By using acetylene black, the electrical characteristics are improved, so that the power cable becomes suitable for wet-design power cable technology despite the use of general-purpose materials for the insulation layer. The functions of the internal semiconducting layer mentioned above are enhanced by using acetylene black within the internal semiconducting layer.

[0022] In one aspect, the wet-design HV power cable may have an internal semiconducting layer, and the polymer matrix of the internal semiconducting layer comprises a copolymer composed of an olefin comonomer and a polar comonomer, wherein the polar comonomer is preferably selected from the group consisting of alkyl acrylate, alkyl methacrylate, and vinyl acetate.

[0023] In a preferred aspect, the polymer matrix of the inner semiconducting layer comprises low density ethylene-ethylacrylate, low density ethylene-propylacrylate, low density ethylene-butylacrylate, or low density ethylene-vinyl acetate. In a more preferred aspect, the polymer matrix of the inner semiconducting layer comprises ethylene-vinyl acetate having a vinyl acetate content of 12% to 38%, more preferably 18% to 33%, based on the total weight of the ethylene-vinyl acetate.

[0024] The above polymer matrix ensures the dispersion of acetylene black and contributes to obtaining a smooth surface. Accordingly, a combination of features regarding the polymer matrix of the inner semiconducting layer, the acetylene black contained in the inner semiconducting layer, and the insulating layer comprising a polymer phase made of a homopolymer is advantageous in light of the purpose of the present invention. Furthermore, a combination of features regarding the polymer matrix of the inner semiconducting layer, the acetylene black contained in the inner semiconducting layer, the insulating layer comprising a polymer phase made of a homopolymer, and a low concentration of monomeric organic components is advantageous in light of the purpose of the present invention.

[0025] In one aspect, the acetylene black may have a BET specific surface area of ​​5 to 100 m² / g, preferably 10 to 90 m² / g, more preferably 20 to 80 m² / g.

[0026] The BET (Brunauer, Emmett, and Teller) theory is commonly used to evaluate gas adsorption data and calculate specific surface area results. As a measurement method, commercially available devices are used.

[0027] Acetylene black having these characteristics provides the most advantageous properties for the power cable.

[0028] As an alternative, furnace black can replace acetylene black. However, the advantageous effects associated with the present invention cannot be achieved. Nevertheless, there are advantageous effects in terms of the availability of furnace black material. While it is important for the inner semiconducting layer to contain acetylene black for electrical properties, the outer semiconducting layer may contain furnace black.

[0029] Accordingly, in one embodiment, the inner semiconducting layer comprises acetylene black, the insulating layer comprises a polymer phase made of a homopolymer, and the outer semiconducting layer comprises furnace black. Such a wet-design HV power cable can be operated up to a voltage between 30 kV and 290 kV.

[0030] In one aspect, the amount of monomeric organic component is 0.1 μg to 10 mg per 1 kg of polymer, preferably 0.001 mg to 5 mg per 1 kg of polymer, more preferably 0.1 mg to 1 mg per 1 kg of polymer.

[0031] It is well known in the art that the crystallinity of polyethylene affects its electrical properties. The higher the crystallinity, the greater the tendency for adverse electrical properties to appear. Crystallinity also affects water treeing. To reduce crystallinity, certain polar substances that inhibit the crystallization of polyethylene are added. CA 1154220 A discloses the use of vinyl acetate to reduce crystallinity. Within the scope of this application, the term “polar substance” refers to a polar monomeric substance, that is, a substance having a non-uniform distribution of electron density that forms partial positive and negative charge regions.

[0032] Surprisingly, it has been found that intentionally reducing the total amount of polar organic components reduces the tendency for water treeing, which may be an effect associated with the low crystallinity of XLPE homopolymers. In this regard, it is desirable for the amount of monomeric organic components to be zero, but achieving such a goal may be practically difficult.

[0033] As described above, the internal semiconducting layer and its constituent components and characteristics are particularly important in the wet-design HV power cable of the present invention. The electrical characteristics of the wet-design HV power cable, which are imparted by the characteristics of the insulation layer of the power cable—namely, the non-blend polymer constituting the insulation layer—must be adjusted so that the cable is suitable as a wet-design HV power cable. While the use of general-purpose materials alone as the insulation layer does not improve the desired electrical characteristics, additional characteristics influence the electrical characteristics, enabling the power cable to be constructed as a wet-design. These characteristics are realized by acetylene black within the internal semiconducting layer. By using acetylene black, the electrical characteristics are improved, so that the power cable becomes suitable for wet-design power cable technology despite the use of general-purpose materials as the insulation layer material. The functions of the internal semiconducting layer mentioned above are enhanced by using acetylene black within the internal semiconducting layer. The improvement imparted by the internal semiconducting layer is similar to the improvement imparted by characteristics regarding the total amount of polar organic components. In other words, the total amount of organic components plays a role in providing power cables configured with a wet design, even though general-purpose materials are used as the insulating layer.

[0034] A reduction in the total amount of monomeric organic components can be achieved by increasing the purity of the monomeric components before polymerization.

[0035] In measuring the total amount of monomeric organic components, the insulating layer is subjected to a peeling method, and the thin film slice of the insulating material is subjected to infrared (IR) spectroscopy. From the manufacturing process of the insulating layer, it is known what monomeric organic components are expected to be present in the material. These monomeric organic components originate from the starting materials of the polymerization, which provides the possibility of deriving the expected substances in the product. Their amount can be measured using IR technology.

[0036] In one aspect, the wet-design HV power cable does not include a metal sheath layer. This feature represents an important characteristic that makes the power cable a “wet-design” HV power cable.

[0037] In one aspect, the polymer of the insulating layer is preferably composed of a homopolymer, preferably an XLPE homopolymer, and more preferably a cross-linked LDPE homopolymer, which is XLPE. This means that the polymer of the insulating layer is composed of a single homopolymer. XLPE is the most suitable general-purpose material for use as an insulating material. As an alternative to this aspect, the polymer of the insulating layer (4) is preferably composed of a copolymer composed of two or more non-polar comonomers. It should be understood that the copolymer does not contain a polar comonomer.

[0038] In the scope of this application, the term “non-polar comonomer” is understood to mean a comonomer that does not contain heteroatoms; and the term “polar comonomer” is understood to mean a comonomer that contains heteroatoms, preferably a comonomer that contains carboxyl groups or oxygen atoms.

[0039] In one aspect, the insulating layer has a thickness of 5 mm to 50 mm, preferably 8 mm to 40 mm, more preferably 12 mm to 35 mm, and most preferably 15 mm to 30 mm.

[0040] This thickness range enables manufacturing that allows the power cable to have sufficient electrical durability while exhibiting sufficient flexibility to ensure adequate bending ability.

[0041] In one aspect, the electric conductor is a metal containing Cu or Al.

[0042] The metal used for the electrical conductors of the above-mentioned wet-design HV power cable is a general-purpose metal.

[0043] In one aspect, the wet design HV power cable can operate at a voltage of 30 kV to 400 kV, preferably 50 kV to 300 kV, more preferably 70 kV to 200 kV.

[0044] An advantageous effect associated with the present invention is that the operating voltage is higher compared to conventional wet-design HV power cables.

[0045] In one aspect, the power cable may include at least one of a metal armoring layer, an outer protective sheath layer, preferably an outer protective polymer sheath layer.

[0046] The above additional layers have an advantageous effect in terms of mechanical resistance to impacts applied to the power cable from the outside.

[0047] In one aspect, the wet design HV power cable comprises at least three cable cores. According to a preferred aspect, the armoring layer surrounds the at least three cable cores, and the outer protective sheath layer surrounds the armoring layer.

[0048] The above wet design HV power cable can be implemented as an AC power cable.

[0049] In one aspect, the first semiconducting layer, the insulating layer, and the second semiconducting layer can form a three-layer insulating structure. In other words, the insulating layer is in direct physical contact with the first semiconducting layer, and the second semiconducting layer is in direct physical contact with the insulating layer.

[0050] The above inner and outer semiconducting layers are preferably made of a thermosetting polymer material.

[0051] In one aspect, the inner semiconducting layer and the outer semiconducting layer are manufactured from the same material. In understanding this aspect, the term "same material" may mean that the raw materials used in the inner and outer semiconducting layers are the same, or that the raw materials and their respective contents are the same in the inner and outer semiconducting layers. According to another aspect disclosed above, the carbon black used in the inner and outer semiconducting layers may be different from each other.

[0052] The wet-design HV power cable according to the present invention may further include an electrical insulation sheath surrounding a second semiconducting layer, which may be in direct physical contact with the second semiconducting layer. This sheath is distinguished from a metal sheath layer that protects against moisture penetration.

[0053] The final wet-design HV power cable is typically an assembly comprising interconnected cable lengths and connecting accessories such as terminals, GIS terminals, asymmetric joints, HV or MV joints, MV terminals, MV plug-in terminals, etc. The wet-design HV power cable can be easily equipped with factory joints or field / repair joints.

[0054] The problem forming the basis of the present invention is further solved by the features of claim 11. Accordingly, a second aspect of the present invention relates to a wet-design HV power cable comprising a cable core, wherein the cable core comprises an electrical conductor, said electrical conductor is surrounded in sequence by an inner semiconducting layer, an insulating layer, and optionally an outer semiconducting layer; and wherein,

[0055] - The above-mentioned inner semiconducting layer comprises acetylene black within the polymer matrix of the inner semiconducting layer; and

[0056] - The above insulating layer includes a polymer, and

[0057] The polymer is a polymer blend comprising at least a first polymer and a second polymer, wherein the first polymer is an XLPE homopolymer, preferably a cross-linked LDPE homopolymer, and the second polymer is a copolymer that does not contain a polar comonomer.

[0058] The above second aspect represents an alternative to the first aspect of the present invention. In the prior art, the insulation layer of a wet-design cable is made of a polymer blend comprising polyethylene and a polar copolymer. According to the second aspect of the present invention, polyethylene is combined with a non-polar copolymer. The use of such a blend and the combination with an internal semiconducting layer containing acetylene black and a low amount of monomeric components are associated with advantageous effects, thereby solving the objective underlying the present invention.

[0059] In one aspect, the wet-designed HV power cable comprises an insulating layer which is a polymer blend comprising at least a first polymer and a second polymer, wherein the first polymer is composed of an XLPE homopolymer which is a cross-linked LDPE homopolymer. According to a further aspect, the wet-designed HV power cable comprises an insulating layer, wherein the second copolymer does not comprise a polar comonomer, and the polar comonomer is preferably composed of linear low-density polyethylene (LLDPE), ethylene-propylene rubber (EPR), or ethylene-propylene-diene rubber (EPDM).

[0060] On the one hand, the effects related to the composition of the inner semiconducting layer and on the other hand, the composition of the insulating layer, are related to the compatibilization of these two layers and the compatibilization of a specific carbon black within the inner semiconducting layer. When the acetylene black is advantageously compatibilized within the polymer matrix of the inner semiconducting layer, the inner semiconducting layer must be attached to the insulating layer such that the interface is as smooth as possible. The smoothness of the interface exhibits characteristics that favorably influence the electrical properties of the power cable. The combination of materials improves the power cable to realize the above favorable effects.

[0065] In one aspect, the polymer matrix of the inner semiconducting layer comprises low-density ethylene-ethyl acrylate, low-density ethylene-propyl acrylate, low-density ethylene-butyl acrylate, or low-density ethylene-vinyl acetate.

[0066] The problem forming the basis of the present invention is also solved by the features of claim 15. Accordingly, a third aspect of the present invention relates to a method for manufacturing at least a portion of a power cable, comprising the following steps: providing an electric conductor; forming a cable core by radially surrounding the electric conductor in sequence an inner semiconducting layer, an insulating layer, and optionally an outer semiconducting layer; and optionally placing at least one additional layer radially around the cable core.

[0067] In one aspect, the above method is a method for manufacturing a wet-designed HV power cable according to the present invention, that is, according to the first aspect or the second aspect.

[0068] The problem forming the basis of the present invention is also solved by the features of claim 15. Accordingly, the fourth aspect of the present invention relates to a use for operating a wet-designed HV power cable according to the present invention at a voltage of 30 kV to 400 kV, preferably 50 kV to 300 kV, more preferably 70 kV to 200 kV.

[0069] The problem underlying the present invention is further solved by a fifth aspect of the present invention, which relates to a method for installing and / or operating a wet-designed HV power cable in a submarine environment according to the first aspect, i.e., claim 1, or the second aspect, i.e., claim 14.

[0070] Surprisingly, it has been discovered that the wet-design HV power cable can be used in a seabed environment, even though it was developed without using a separate moisture barrier layer, and specifically without a metal sheath. The wet-design HV power cable can be installed on the seabed as is known to those skilled in the art. Surprisingly, it has been discovered that the wet-design HV power cable according to the present invention has sufficient durability in a seabed environment. In one aspect, the wet-design HV power cable according to the present invention can be installed and / or operated at a depth of 300 m to 3,000 m, preferably 1,000 m to 2,500 m. In an additional aspect, the wet-design HV power cable according to the present invention can be operated at a voltage of 30 kV to 400 kV, preferably 50 kV to 300 kV, more preferably 70 kV to 200 kV.

[0071] The features disclosed in relation to the wet-design HV power cable of the present invention are deemed to be disclosed in relation to the method of the present invention and the use of the present invention, and vice versa. Brief explanation of the drawing

[0072] Specific aspects of the subject matter disclosed herein will be described with reference to the accompanying drawings, which are illustrative and schematic in nature and should not be construed as limiting in any respect with respect to the scope of the subject matter disclosed herein: FIG. 1 illustrates the main configuration of a cable core; FIG. 2 illustrates an example of a wet-design HV power cable according to the present invention. Specific details for implementing the invention

[0073] FIG. 1 illustrates the main configuration of a cable core (1) having an electric conductor (2), wherein the electric conductor (2) is surrounded in order by an inner semiconducting layer (3), an insulating layer (4), and an outer semiconducting layer (5), which is not essentially required by the present invention.

[0074] The medium or high voltage power cable illustrated in FIG. 2 comprises a central conductive element (2) made particularly of copper or aluminum, and sequentially and coaxially around the conductive element (2) a first semiconducting layer (3) known as an “inner semiconducting layer,” an electrical insulation layer (4), a second semiconducting layer (5) known as an “outer semiconducting layer,” a cylindrical tube-type metal shielding layer (6) (non-waterproof), and an outer protective sheath (7) for mechanical protection, wherein the electrical insulation layer (4) is made of a homopolymer.

[0075] In an exemplary embodiment of the first aspect disclosed herein, a wet-design HV power cable is disclosed that comprises a cable core made of a metal, particularly copper or aluminum. The cable core comprises a metal as an electrical conductor surrounded by an inner semiconducting layer. The inner semiconducting layer comprises a polymer matrix in which acetylene black is embedded. The inner semiconducting layer is surrounded by an insulating layer and optionally an outer semiconducting layer. The layers follow the order mentioned. The insulating layer comprises a polymer, and the polymer is a non-blend polymer composed of an XLPE homopolymer. It is important that the insulating layer of the wet-design cable of this first aspect does not contain additional polymers. The polymer matrix of the inner semiconducting layer comprises a copolymer composed of an olefin comonomer and a polar comonomer. The insulating layer composed of the XLPE homopolymer substantially does not contain monomeric organic components. This can be achieved by performing crosslinking without using additional crosslinking agents and / or by using monomer components of very high purity to produce XLPE homopolymers. The content of the monomeric organic component is 0.001 mg to 1 mg per 1 kg of polymer. These characteristics are achieved by the measures described above.

[0076] In an exemplary embodiment of the second aspect disclosed herein, a wet design HV power cable comprising a cable core (1) is disclosed, wherein the cable core (1) comprises an electrical conductor (2) and the electrical conductor (2) is surrounded in sequence by an inner semiconducting layer (3), an insulating layer (4), and optionally an outer semiconducting layer (5); wherein,

[0077] - The above-mentioned inner semiconducting layer comprises acetylene black within the polymer matrix of the inner semiconducting layer; and

[0078] - The insulating layer comprises a polymer blend including at least a first polymer and a second polymer, wherein the first polymer is composed of an XLPE homopolymer which is a cross-linked LDPE homopolymer, and the second polymer is composed of a copolymer that does not include a polar comonomer.

[0079] Accordingly, the insulating layer is a polymer blend, and the blend does not include a copolymer containing polar monomers such as acrylate. The second copolymer, i.e., the second polymer, is selected from the group consisting of linear low-density polyethylene (LLDPE), ethylene-propylene rubber (EPR), and ethylene-propylene-diene rubber (EPDM).

[0080] Accordingly, the wet design cable according to the second aspect comprises an interface between a layer comprising acetylene black within a polymer matrix of an inner semiconducting layer comprising low-density ethylene-ethyl acrylate, low-density ethylene-propyl acrylate, low-density ethylene-butyl acrylate, or low-density ethylene-vinyl acetate, and a layer comprising an insulating layer comprising a polymer blend comprising a copolymer selected from the group consisting of XLPE and linear low-density polyethylene (LLDPE), ethylene-propylene rubber (EPR), and ethylene-propylene-diene rubber (EPDM).

[0081] The following items are disclosed in this specification:

[0082] 1. In a wet design HV power cable comprising a cable core (1), the cable core (1) comprises an electrical conductor (2), and the electrical conductor (2) is surrounded in order by an inner semiconducting layer (3), an insulating layer (4), and optionally an outer semiconducting layer (5);

[0083] - The inner semiconducting layer (3) comprises acetylene black within the polymer matrix of the inner semiconducting layer; and

[0084] - The above insulating layer (4) includes a polymer,

[0085] The above polymer is a non-blend polymer.

[0086] 2. In a wet-design HV power cable according to Item 1, the polymer matrix of the inner semiconducting layer comprises a copolymer composed of an olefin comonomer and a polar comonomer, wherein the polar comonomer is preferably selected from the group consisting of alkyl acrylate, alkyl methmethacrylate, and vinyl acetate.

[0087] 3. In a wet-design HV power cable according to Item 2, the polymer matrix of the inner semiconducting layer comprises low density ethylene-ethylacrylate, low density ethylene-propylacrylate, low density ethylene-butylacrylate, or low density ethylene-vinylacetate.

[0088] 4. In the wet design HV power cable according to Item 1, the acetylene black has a BET surface area of ​​5 to 100 m² / g, preferably 10 to 90 m² / g, more preferably 20 to 80 m² / g.

[0089] 5. As a wet-design HV power cable according to Item 1, the amount of monomeric organic component is 0.001 mg to 10 mg per 1 kg of polymer, preferably 0.01 mg to 5 mg per 1 kg of polymer, more preferably 0.1 mg to 1 mg per 1 kg of polymer.

[0090] 6. In the wet design HV power cable according to Item 1, the wet design HV power cable does not include a metal sheath layer.

[0091] 7. In the wet design HV power cable according to Item 1, the polymer of the insulation layer (4) is composed of a homopolymer, preferably an XLPE homopolymer, and more preferably an XLPE homopolymer which is a cross-linked LDPE homopolymer.

[0092] 8. In the wet design HV power cable according to Item 1, the polymer of the insulating layer (4) is composed of a copolymer made of two or more nonpolar comonomers.

[0093] 9. In the wet design HV power cable according to Item 1, the insulation layer (4) has a thickness of 5 mm to 50 mm, preferably 8 mm to 40 mm, more preferably 12 mm to 35 mm, most preferably 15 mm to 30 mm.

[0094] 10. In the wet design HV power cable according to Item 1, the wet design HV power cable can be operated at a voltage of 30 kV to 400 kV, preferably 50 kV to 300 kV, more preferably 70 kV to 200 kV.

[0095] 11. In a wet design HV power cable according to Item 1, the power cable (1) comprises at least one of the following:

[0096] - Metal armoring layer,

[0097] - External protective sheath layer, preferably an external protective polymer sheath layer.

[0098] 12. In the wet design HV power cable according to Item 1, the inner semiconducting layer (3) and the outer semiconducting layer (5) are made of the same material.

[0099] 13. A wet design HV power cable comprising a cable core (1), wherein the cable core (1) comprises an electric conductor (2), and the electric conductor (2) is surrounded in order by an inner semiconducting layer (3), an insulating layer (4), and optionally an outer semiconducting layer (5);

[0100] - The inner semiconducting layer (3) comprises acetylene black within the polymer matrix of the inner semiconducting layer; and

[0101] - The insulating layer (4) comprises a polymer blend including at least a first polymer and a second polymer, wherein the first polymer is an XLPE homopolymer, preferably a cross-linked LDPE homopolymer, and the second polymer is a copolymer that does not contain a polar comonomer.

[0102] 14. A method for manufacturing at least a portion of a power cable, wherein the method comprises:

[0103] - Step of providing an electric conductor (2),

[0104] - A step of forming a cable core (1) by radially surrounding the electrical conductor (2) with an inner semiconducting layer (3), an insulating layer (4), and optionally an outer semiconducting layer (5) in sequence; and

[0105] - Optionally includes the step of placing at least one additional layer radially around the cable core (1).

[0106] 15. Use for operating a wet-design HV power cable according to any one of items 1 to 11 at a voltage of 30 kV to 400 kV, preferably 50 kV to 300 kV, more preferably 70 kV to 200 kV. Explanation of the symbols

[0107] 1 Cable core 2 electric conductor 3 Internal semiconducting layer 4 insulating layer 5 External semiconducting layer 6 Metal shielding layer (non-watertight) 7 External protection sheath (for mechanical protection)

Claims

Claim 1 A wet-design HV power cable comprising a cable core (1), wherein the cable core (1) comprises an electrical conductor (2), and the electrical conductor (2) is surrounded in order by an inner semiconducting layer (3), an insulating layer (4), and optionally an outer semiconducting layer (5); wherein the inner semiconducting layer (3) comprises acetylene black within a polymer matrix of the inner semiconducting layer; and wherein the insulating layer (4) comprises a polymer, wherein the polymer is a non-blended polymer composed of an XLPE homopolymer, and the polymer matrix of the inner semiconducting layer comprises a copolymer composed of an olefin comonomer and a polar comonomer. Claim 2 A wet-design HV power cable according to claim 1, wherein the polymer matrix of the inner semiconducting layer comprises a copolymer composed of an olefin comonomer and a polar comonomer, and the polar comonomer is selected from the group consisting of alkyl acrylate, alkyl methacrylate, and vinyl acetate. Claim 3 A wet-design HV power cable according to claim 2, wherein the polymer matrix of the inner semiconducting layer comprises low density ethylene-ethylacrylate, low density ethylene-propylacrylate, low density ethylene-butylacrylate, or low density ethylene-vinylacetate. Claim 4 A wet-design HV power cable according to claim 1, wherein the acetylene black has a BET surface area of ​​5 to 100 m² / g, preferably 10 to 90 m² / g, more preferably 20 to 80 m² / g. Claim 5 A wet-design HV power cable according to claim 1, wherein the amount of monomeric organic component is 0.001 mg to 10 mg per 1 kg of polymer, preferably 0.01 mg to 5 mg per 1 kg of polymer, more preferably 0.1 mg to 1 mg per 1 kg of polymer. Claim 6 In claim 1, the wet-design HV power cable is a wet-design HV power cable that does not include a metal sheath layer. Claim 7 A wet-design HV power cable according to claim 1, wherein the polymer of the insulating layer (4) is a cross-linked LDPE homopolymer or an XLPE homopolymer. Claim 8 A wet-design HV power cable according to claim 1, wherein the polymer of the insulating layer (4) is a copolymer composed of two or more nonpolar comonomers. Claim 9 In claim 1, the power cable (1) is a wet-design HV power cable comprising: - a metal armoring layer, - an outer protective sheath layer, preferably an outer protective polymer sheath layer. Claim 10 A wet-design HV power cable according to claim 1, wherein the inner semiconducting layer (3) and the outer semiconducting layer (5) are made of the same material. Claim 11 A wet-design HV power cable comprising a cable core (1), wherein the cable core (1) comprises an electrical conductor (2), and the electrical conductor (2) is surrounded in order by an inner semiconducting layer (3), an insulating layer (4), and optionally an outer semiconducting layer (5); wherein the inner semiconducting layer (3) comprises acetylene black within a polymer matrix of the inner semiconducting layer; and wherein the insulating layer (4) comprises a polymer blend comprising at least a first polymer and a second polymer, wherein the first polymer is composed of an XLPE homopolymer and the second polymer is composed of a copolymer not comprising a polar comonomer. Claim 12 A wet-design HV power cable according to claim 11, wherein the first polymer is a cross-linked LDPE homopolymer or an XLPE homopolymer. Claim 13 In claim 11, the copolymer not containing the polar comonomer is a wet-design HV power cable composed of linear low-density polyethylene (LLDPE), ethylene-propylene rubber (EPR), and ethylene-propylene-diene rubber (EPDM). Claim 14 A wet-design HV power cable according to claim 11, wherein the polymer matrix of the inner semiconducting layer comprises low density ethylene-ethylacrylate, low density ethylene-propylacrylate, low density ethylene-butylacrylate, or low density ethylene-vinylacetate. Claim 15 A method for manufacturing at least a portion of a power cable according to claim 1, comprising: - providing an electric conductor (2); - forming a cable core (1) by radially surrounding the electric conductor (2) an inner semiconducting layer (3), an insulating layer (4), and optionally an outer semiconducting layer (5) in sequence; and - optionally placing at least one additional layer radially around the cable core (1).

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