Power cable with stripable sheath

Abstract

There is provided a power cable (1) comprising: a conductor (2) extending along a centre axis (C), an insulation system (3) arranged around the conductor, a metallic screen (4) arranged around the insulation system (3) and a multilayer outer sheath (5) arranged around the metallic screen (4), wherein the multilayer outer sheath (5) comprises: a first layer (6) being a separable layer and comprising a base polymer, a second layer (7), being a semiconductive layer comprising a base polymer, wherein the first layer (6) is arranged radially inside of the second layer, and wherein the second layer is the outermost layer of the power cable.

Description

TECHNICAL FIELD

[0001] The present disclosure generally relates to power cables.BACKGROUND

[0002] A typical power cable comprises a conductor surrounded by an insulation system composed of at least an inner semiconductive layer, an insulation layer and optionally an outer semiconductive layer, in that order. The power cables are typically produced by extruding the layers onto the conductor. Radially outside of the insulation system there is a metallic screen and a sheath, or jacket, that provides mechanical and environmental protection for the layers underneath. Further, this layer is typically used to or facilitate easier access to the inner components of the cable during installation or maintenance.

[0003] It is desirable to be able to dismantle the cable sheath without damaging the underlying layers. It is also desirable to joint cables easily. A common operation is to strip the sheath of the cable, by peeling off the layer(s) mechanically by cutting in longitudinal and radial direction. In particular for symmetric cables having a circular cross-section such operation is widely used. However, by such operation, there is a risk of damaging the layers underneath the sheath and the operation is also time consuming and challenging in field work. For asymmetric cables, having a non-circular cross section the cable body can be filled with fillers making the cable round. However, such solution is costly and less environmentally friendly.

[0004] There are, thereby, issues of the existing solutions to overcome.SUMMARY

[0005] A general object of the present disclosure is to provide a power cable that solves or at least mitigates the problems of the prior art.

[0006] According to the present disclosure, there is provided a power cable comprising: a conductor extending along a centre axis, an insulation system arranged around the conductor, a metallic screen arranged around the insulation system and a multilayer outer sheath arranged around the metallic screen, wherein the multilayer outer sheath comprises: a first layer being a separable layer and comprising a base polymer, a second layer, being a semiconductive layer comprising a base polymer, wherein the first layer is arranged radially inside of the second layer, and wherein the second layer is the outermost layer of the power cable.

[0007] Hereby, an advantageous outer sheath is provided. Thus, an improved power cable is provided. Owing to that the first layer is a separable layer arranged radially inside of the second layer and the second layer is semiconductive and the outermost layer of the power cable, the semiconductive layer of the outer sheath can easily be separated from the cable. Thereby, damages on the layer(s) underneath is avoided. There are also benefits in terms of facility and speed of the removal of the semiconductive layer. It is beneficial that the outer layer of the power cable is semiconductive, in particular when performing testing of quality of the outer sheath.

[0008] The first layer is a separable layer. Meaning that it is a separable layer from the layer arranged radially inside and in contact with the first layer, i.e. the directly underlying layer. Typically, the first layer is a strippable layer, peelable layer or a non-adhesive layer. A strippable layer is a coating that can be easily removed or stripped away from the surface it is applied to, typically in one piece or in large sections. A peelable layer is similar to a strippable layer. A non-adhesive layer is a layer that has low adhesive properties, thereby it does not stick to the surface it is applied to but is instead held in place by mainly mechanical means. The first layer may be a foamed layer. It is advantageous that the first layer is a separable layer when forming joints or terminations of the cable since the semiconductive layer(s) arranged in the multilayer outer sheath needs to be removed in such operation.

[0009] The second layer is a semiconducting layer. Thereby, the second layer comprises an additive to the base polymer of the second layer which provides for the semiconductivity. Typically, the second layer is made from a polymer composite infused with conductive or semiconductive material like carbon black. A semiconductive layer in the outer sheath in a power cable enables electrical test of the outer sheath of the power cable.

[0010] The function of the metallic screen is to e.g. conduct capacitive currents, unbalanced network currents and faults currents in case of ground faults. Typically, the metallic screen is made from aluminum, aluminum covered in a semiconducting polymer, copper, copper clad aluminum or braided copper bands. The metallic screen can be made from foil and / or wires.

[0011] The insulation system typically comprises a first semiconducting layer provided around the conductor, an insulation layer provided around the first semiconducting layer, and a second semiconducting layer provided around the insulation layer.

[0012] In one embodiment the multilayer outer sheath is an extruded layer, i.e. has been produced by extrusion, such as co-extrusion.

[0013] According to one embodiment, the power cable further comprises a rip cord arranged radially inside and in contact with the first layer. A ripcord in cable insulation is an embedded strong, typically nylon or polyester, cord. Its primary function is to facilitate easy and clean removal of the outer sheath without damaging the inner components of the cable. By pulling the ripcord, technicians can quickly and safely strip away the outer layer, exposing the insulated layer(s) inside, making it easier to access and work with the cable's internal structure.

[0014] According to one embodiment, the base polymer of the second layer has a higher density than the base polymer of the first layer. Thereby the second layer can act as a protective layer to the layer underneath. Moreover, the friction of the second layer is typically lower than of the first layer, which is advantageous when the power cable is laid out. The second layer is typically also more robust than the first layer.

[0015] There is no limitation on the base polymer to be used in the first layer. Examples of a base polymer suitable in the first layer is a polyolefin, e.g. polyethylene (PE), such as crosslinked PE (XLPE), or polypropylene (PP), the base polymer of the first layer may also be polyvinyl chloride (PVC), polyamides (PA), thermoplastic elastomers (TPEs) or EPDM, ethylene-polypropylene rubber (EPR), silicone rubber, polyurethane (PUR), chloroprene rubber (CR), preferably the base polymer is polyethylene, more preferably medium density polyethylene (MDPE) or high density polyethylene, (HDPE).

[0016] Examples of a base polymer suitable in the second layer is a polyolefin, e.g. polyethylene (PE), such as crosslinked PE (XLPE), or polypropylene (PP), the base polymer of the second layer may also be polyvinyl chloride (PVC), polyamides (PA), thermoplastic elastomers (TPEs) or EPDM, ethylene-polypropylene rubber (EPR), silicone rubber, polyurethane (PUR), chloroprene rubber (CR), preferably the base polymer is polyethylene, more preferably medium density polyethylene (MDPE) or high density polyethylene, (HDPE).

[0017] In one embodiment, the first layer and the second layer are in contact. Preferably, the first layer adheres well to the second layer. Accordingly, when the first layer is separated from the power cable, the second layer is separated as well being adhered to the first layer.

[0018] In one embodiment, the first layer is a non-conductive separable layer. Preferably it is only the second layer that is semiconductive in the multilayer outer sheath. In particular for terminations and joints, it is advantageous that there is no residual semiconducting layer and / or material after removal of the second layer as such residual layer(s) and / or material interfere with the lifetime of the cable. Accordingly, it is beneficial that the first layer is non-conductive since such arrangement facilitates in complete removal of the semiconducting layer in the cable.

[0019] In one embodiment, the second layer is thinner than the first layer. It is beneficial that the second layer can act as a durable protective layer, while the first layer is thicker and provides mechanical support to the metallic screen and potential inner layer(s).

[0020] In one embodiment, the Shore D according to ASTM D2240-5(2021) is higher for the second layer than for the first layer. Thereby, the second layer is a harder layer than the first layer. Shore D hardness is a standardized measure of the hardness of polymers and other materials. It is part of the Shore hardness scale, which quantifies the resistance of a material to indentation. Shore D is specifically used for harder materials, including harder plastics and rubbers. The measurement process involves using a durometer, an instrument with a blunt indenter and a calibrated spring. The indenter is pressed into the material, and the depth of penetration is measured. The Shore D hardness value is then read from a scale ranging from 0 to 100, where higher values indicate harder materials.

[0021] In one embodiment, the multilayer outer sheath comprises a third layer, wherein the first layer is arranged radially outside of the third layer. The third layer is typically an inner layer of the outer sheath being in contact with and around the metallic screen. The third layer is typically a protective layer for the first and second layer. In such case, the third layer may be a thicker layer than the first and second layer, respectively. The third layer may be a foamed layer. Typically, the density of the third layer is lower than the density of the second layer. Examples of a base polymer suitable in the third layer is a polyolefin, e.g. polyethylene (PE), such as crosslinked PE (XLPE), or polypropylene (PP), the base polymer of the third layer may also be polyvinyl chloride (PVC), polyamides (PA), thermoplastic elastomers (TPEs) or EPDM, ethylene-polypropylene rubber (EPR), silicone rubber, polyurethane (PUR), chloroprene rubber (CR), preferably the base polymer is a polyolefin, preferably linear low-density polyethylene (LLDPE) or low-density polyethylene (LDPE). Thermoplastic elastomers (TPEs) are a class of copolymers or a physical mix of polymers (usually a plastic and a rubber) that consist of materials with both thermoplastic and elastomeric properties. The third layer may also be a mixture comprising a polyethylene and a TPE. The hardness of the layer can be adjusted by the addition of TPE. It is beneficial that the first layer is not directly adhering to the metallic screen as the metallic screen may be damaged in case all of the above layers are separated. The third layer may be of a different colour than the first layer, which facilitates for installers to verify a successful removal of the first and second layer.

[0022] In one embodiment, the multilayer outer sheath comprises the third layer and a fourth layer comprising a base polymer, wherein the fourth layer is non-conductive and arranged radially outside of the third layer and radially inside of the first layer. In such embodiment, the outer sheath typically consists of four layers. Examples of a base polymer suitable in the fourth layer is is a polyolefin, e.g. polyethylene (PE), such as crosslinked PE (XLPE), or polypropylene (PP), the base polymer of the fourth layer may also be polyvinyl chloride (PVC), polyamides (PA), thermoplastic elastomers (TPEs) or EPDM, ethylene-polypropylene rubber (EPR), silicone rubber, polyurethane (PUR), chloroprene rubber (CR), preferably the base polymer is polyethylene, more preferably medium density polyethylene (MDPE) or high density polyethylene, (HDPE). An example of a suitable base polymer for the fourth layer is polyethylene, preferably medium density polyethylene, (MDPE), or high density polyethylene (HDPE). Yet another example of base polymer suitable in the fourth layer is thermoplastic elastomers (TPEs). Thermoplastic elastomers (TPEs) are a class of copolymers or a physical mix of polymers (usually a plastic and a rubber) that consist of materials with both thermoplastic and elastomeric properties. The fourth layer may also be a mixture comprising a polyethylene, preferably HDPE or MDPE, and a TPE. The hardness of the layer can be adjusted by the addition of TPE.

[0023] In one embodiment, the adhesion of the first layer to its directly underlying layer of the power cable is in the range of ≤45 N in a peel test according to HD 605 S3:2019. Such adhesion is beneficial in terms of providing enough adhesion the underlaying layer to be secured, but still be separable from the directly underlying layer of the power cable.

[0024] In one embodiment, the power cable is an asymmetric power cable having a non-circular cross-section. In such embodiment, the power cable typically comprises: three power cores, wherein each power core comprises the respective conductor extending along the centre axis and the insulation system arranged around the conductor, wherein the cross-section of the power cable is generally triangular, wherein the metallic screen is arranged around the three power cores, and the multilayer outer sheath is arranged around the metallic screen.

[0025] As is clear from that this embodiment is part of the present disclosure, the multilayer outer sheath comprises at least a first layer being a separable layer and comprising a base polymer, a second layer, being a semiconductive layer comprising a base polymer, wherein the first layer is arranged radially inside of the second layer, and wherein the second layer is the outermost layer of the power cable.

[0026] By provision of the first layer being a separable layer in the outer sheath dismantling of the sheath in an asymmetric power cable is facilitated. The separable layer provides for that the stripping off the sheath mechanically by cutting in longitudinal and radial direction, peeling the layer(s) off or scraping off the layers in a tedious process can be avoided. In particular for symmetric cables having a circular cross-section such operation is widely used. However, by such operation, there is a risk of damaging the layers underneath the sheath and the operation is also time consuming and challenging in field. Regarding asymmetric cables, having a non-circular cross section, the need for fillers making the cable round can also be eliminated, which is beneficial from a cost and environmental perspective.

[0027] In one embodiment, the power cable is a medium voltage power cable or a high voltage power cable. Typically in such case, the power cable is a high voltage power cable having a voltage rating in a range of ≥1 kV.

[0028] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise.BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Aspects and embodiments are now described, by way of example, with reference to the accompanying drawings, in which: Fig. 1a schematically shows a radial cross section of a power cable of an example embodiment; Fig. 1a schematically shows a side view of at least a part of the power cable of Fig. 1a; and Fig. 2a schematically shows a radial cross section of a power cable of an example embodiment; Fig. 2b schematically shows a side view of at least a part of the power cable of Fig. 2a; and Fig. 3a schematically shows a radial cross section of a power cable of an example embodiment; Fig. 3b schematically shows a side view of at least a part of the power cable of Fig. 3a; and Fig. 4a schematically shows a radial cross section of a power cable of an example embodiment; Fig. 4b schematically shows a side view of at least a part of the power cable of Fig. 4a; and Fig. 5 schematically shows a radial cross section of a power cable of an example embodiment. Fig. 6 schematically shows a radial cross section of a power cable of an example embodiment. Fig. 7 schematically shows a radial cross section of a power cable of an example embodiment. DETAILED DESCRIPTION

[0030] The aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown.

[0031] These aspects may, however, be embodied in many different forms and should not be construed as limiting; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and to fully convey the scope of all aspects of invention to those skilled in the art. Like numbers refer to like elements throughout the description.

[0032] Figs. 1, 2, 3 and 4 show an example of a power cable 1. The power cable 1 is in this example a single power core power cable. However, it should be mentioned that the power cable could comprise several identical power cores to form a multi-core power cable, such as three-phase power cable. The power cable 1 may be a high voltage power cable having a voltage rating in a range of ≥1 kV.

[0033] Figs. 5, 6 and 7 show an example of an asymmetric power cable 101 having a non-circular cross-section as it contains three power cores.

[0034] Just as the power cable 1 of Figs. 1, 2, 3 and 4, the power cable 105 may be a high voltage power cable having a voltage rating in a range of ≥1 kV.

[0035] In Fig. 1, a radial cross section of an embodiment of a power cable 1 is shown. The radial cross section is a cross section in the radial direction r of the power cable 1, i.e. a plane perpendicular to a centre axis of the power cable 1 (extending into the paper). The power cable 1 may e.g. be defined by cylindrical coordinates (by a radial distance r, azimuth φ which is the angle along the circumferential direction, and an axial coordinated along the longitudinal axis).

[0036] In Fig. 1b, a side view of the power cable 1 of Fig. 1a, in which the power cable 1 extends along the centre axis C (or centre longitudinal axis).

[0037] In the following, the power cable 1 will be described with reference to both Figs. 1a and 1b. The power cable 1 comprises a conductor 2 extending along the centre axis C. The conductor 2 may for example be stranded, segmental of Milliken type, solid, or a profile wire conductor. The conductor 2 may for example comprise copper or aluminum.

[0038] The power cable 1 further comprises an insulation system 3 provided around, and covering, the conductor 2. The power cable 1 further comprises a metallic screen 4 provided around, and covering, the insulation system 3. Arranged around, and covering, the metallic screen 4 there is provided a multilayer outer sheath 5.

[0039] The multilayer outer sheath 5 comprises a first layer 6 being a separable layer and comprising a base polymer, a second layer 7, being a semiconductive layer comprising a base polymer, wherein the first layer 6 is arranged radially inside of the second layer, and wherein the second layer is the outermost layer of the power cable 1.

[0040] The metallic screen 4 is typically arranged to prevent, or at least greatly reduce, water penetrating into the insulation system 3 from the outside. The metallic screen may e.g. exhibit a water permeability of below 0.1 g / (m2*24 h) or below 0.05 g / (m2*24 h).

[0041] In the embodiment of Figs. 1a and 1b, the multilayer outer sheath is arranged in direct contact with, and radially outside of, the metallic screen 4. Thus, the metallic screen 4 is arranged in between the insulation system 3 and the multilayer outer sheath 5.

[0042] The multilayer outer sheath 5 may e.g. comprise a polymeric material that is extruded around the metallic screen 4. The multilayer outer sheath 5 of the embodiment of Figs. 1a and 1b and may be wholly or partly water impermeable.

[0043] The multilayer outer sheath 5 may be extruded and comprise comprise thermosetting and / or thermoplastic polymer material. For example, the layers 6 and 7 of the multilayer outer sheath 5 may be different in the aspect of being made of thermosetting and thermoplastic polymer material. The second layer 7 is a semiconductive layer and thereby comprises an electrically conductive compound, e.g. carbon black. The first layer 6, on the other hand, may be non-conductive.

[0044] The second layer 7 is typically containing a base polymer having a higher density than the base polymer of the first layer 6. Further, the second layer 7 is typically thinner than the first layer 6. The second layer 7 may be a polyolefin, e.g. polyethylene (PE), such as crosslinked PE (XLPE), or polypropylene (PP), the base polymer of the second layer may also be polyvinyl chloride (PVC), polyamides (PA), thermoplastic elastomers (TPEs) or EPDM, ethylene-polypropylene rubber (EPR), silicone rubber, polyurethane (PUR), chloroprene rubber (CR), preferably the base polymer is polyethylene, more preferably medium density polyethylene (MDPE) or high density polyethylene, (HDPE), while the first layer 6 may be a polyolefin, e.g. polyethylene (PE), such as crosslinked PE (XLPE), or polypropylene (PP), the base polymer of the first layer may also be polyvinyl chloride (PVC), polyamides (PA), thermoplastic elastomers (TPEs) or EPDM, ethylene-polypropylene rubber (EPR), silicone rubber, polyurethane (PUR), chloroprene rubber (CR), preferably the base polymer is polyethylene, more preferably medium density polyethylene (MDPE) or high density polyethylene, (HDPE). The thickness of the second layer may for example be 0.1-0.5 mm. The XLPE is a crosslinked low density homopolymer of ethylene (LDPE homopolymer), i.e. has been crosslinked by using a crosslinking agent such as peroxide. The LDPE used for the XLPE may e.g. have a density between 915 and 940 kg / m 3< , or between 917 and 930 kg / m 3< . Density is measured according to ISO 1183-1:2019.

[0045] Shore D according to ASTM D2240-5(2021) is typically higher for the second layer 7 than for the first layer 6.

[0046] The adhesion of the first layer 6 to its directly underlying layer is typically in the range of ≤45 N in a peel test according to HD 605 S3:2019. Accordingly, the adhesion of the first layer 6 to the metallic screen 4 may be in the range of ≤45 N.

[0047] Turning to Figs. 2a and 2b showing another example of a power cable 1. The power cable 1 is in this example a single power core power cable as that described with reference to Figs. 1a and 1b. However, it should be mentioned that the power cable could comprise several identical power cores to form a multi-core power cable, such as three-phase power cable. The power cable 1 in Figs. 2a and 2b is in large corresponding to the power cable 1 of Figs. 1a and 1b, why mainly the differences between the power cables 1 are described in the following. Like number are used for like references.

[0048] The insulation system 3 comprises a first semiconducting layer 11 provided around the conductor 2, and an insulation layer 12 provided around the first semiconducting layer 11.

[0049] Turning to Figs. 3a and 3b showing another example of a power cable 1. The power cable 1 is in this example a single power core power cable as that described with reference to Figs. 1a, 1b, 2a and 2b. However, it should be mentioned that the power cable could comprise several identical power cores to form a multi-core power cable, such as three-phase power cable. The power cable 1 in Figs. 3a and 3b is in large corresponding to the power cable 1 of Figs. 1a, 1b, 2a and 2b why mainly the differences between the power cables 1 are described in the following. Like number are used for like references.

[0050] The multilayer outer sheath 5 comprises a first layer 6 being a separable layer and comprising a base polymer, a second layer 7, being a semiconductive layer comprising a base polymer and a third layer 8. The first layer 6 is arranged radially outside of the third layer 8 and the first layer 6 is arranged radially inside of the second layer 7, and the second layer 7 is the outermost layer of the power cable 1.

[0051] The third layer 8 typically act as a damping layer between the metallic screen 4 and the first layer 6. Moreover, a separation of the first layer 6 from the underneath layer is facilitated when the third layer 8 is provided. It is beneficial that the first layer 6 is not directly adhering to the metallic screen 4 as the metallic screen 4 may be damaged in case all of the layers arranged radially outside of the metallic screen 4 are separated. The third layer 8 may be a foamed layer.

[0052] The adhesion of the first layer 6 to its directly underlying layer is typically in the range of ≤45 N in a peel test according to HD 605 S3:2019. Accordingly, the adhesion of the first layer 6 to the third layer 8 maybe in the range of ≤45 N.

[0053] Turning to Figs. 4a and 4b showing another example of a power cable 1. The power cable 1 is in this example a single power core power cable as that described with reference to Figs. 1a, 1b, 2a, 2b, 3a and 3b. However, it should be mentioned that the power cable could comprise several identical power cores to form a multi-core power cable, such as three-phase power cable. The power cable 1 in Figs. 4a and 4b is in large corresponding to the power cable 1 of Figs. 1a, 1b, 2a, 2b, 3a and 3b why mainly the differences between the power cables 1 are described in the following. Like number are used for like references.

[0054] The multilayer outer sheath 5 comprises a first layer 6 being a separable layer and comprising a base polymer, a second layer 7, being a semiconductive layer comprising a base polymer a third layer 8 and a fourth layer 9 comprising a base polymer. The fourth layer 9 is non-conductive and arranged radially outside of the third layer 8 and radially inside of the first layer 6. The first layer 6 is arranged radially inside of the second layer 7, and the second layer 7 is the outermost layer of the power cable 1.

[0055] The fourth layer 9 is an intermediate layer between the third layer 8 typically acting as a damping layer to the metallic screen 4 and the first layer 6. The fourth 9 layer is non-conductive as it is beneficial that the separable layer 6 is not separated from a conductive or semiconductive layer. The fourth layer 9 may be HDPE.

[0056] Turning to Figs. 5, 6 and 7 showing another example of a power cable 101. The power cable 101 is in these examples a multi-core power cable being a three-phase power cable having three power cores. The layers of the power cable 101 in Figs. 5, 6 and 7 is in large corresponding to the power cable 1 of Figs. 1a, 1b, 2a, 2b, 3a, 3b, 4a and 4b why mainly the differences between the power cables 1, 101 are described in the following. Like number are used for like references, but with an additional value of "100" for each feature, i.e. "power cable 1" of Figs. 1a, 1b, 2a, 2b, 3a, 3b, 4a and 4b relates to "power cable 101" of Figs. 5, 6 and 7.

[0057] In Fig. 5 a radial cross section of an embodiment of a power cable 101 is shown. The power cable 101 comprises three power cores 110, wherein each power core 110 comprises a conductor 102 extending along the centre axis C, and an insulation system 103 provided around, and covering, the conductor 102. The power cable 101 further comprises a metallic screen 104 surrounding the three power cores 110 and a multilayer outer sheath 105 provided around the metallic screen 104. The multilayer outer sheath 105 comprises a first layer 106 being a separable layer and comprising a base polymer, a second layer 107, being a semiconductive layer comprising a base polymer, wherein the first layer 106 is arranged radially inside of the second layer, and wherein the second layer is the outermost layer of the power cable 101. All layers maybe the same as the corresponding layers of the power cable 1 of Figs. 1a, 1b, 2a, 2b, 3a, 3b, 4a and 4b.

[0058] Turning to Fig. 6 showing another example of a power cable 101. The power cable 101 is in this example a three-phase power cable as that described with reference to Fig. 5. The power cable 101 in Fig. 6 is in large corresponding to the power cable 101 of Fig. 5, why mainly the differences between the power cables 101 are described in the following. Like number are used for like references.

[0059] The multilayer outer sheath 105 comprises a first layer 106 being a separable layer and comprising a base polymer, a second layer 107, being a semiconductive layer comprising a base polymer and a third layer 108. The first layer 106 is arranged radially outside of the third layer 108 and the first layer 106 is arranged radially inside of the second layer 107, and the second layer 107 is the outermost layer of the power cable 101.

[0060] The third layer 108 typically act as a damping layer between the metallic screen 104 and the first layer 106. Moreover, a separation of the first layer 106 from the underneath layer is facilitated when the third layer 108 is provided. It is beneficial that the first layer 106 is not directly adhering to the metallic screen 104 as the metallic screen 104 may be damaged in case all of the layers arranged radially outside of the metallic screen 104 are separated. The third layer 108 may be a foamed layer.

[0061] Turning to Fig. 7 showing another example of a power cable 101. The power cable 101 is in this example a three-phase power cable as that described with reference to Figs. 5 and 6. The power cable 101 in Fig. 7 is in large corresponding to the power cable 101 of Figs. 5 and 6, why mainly the differences between the power cables 101 are described in the following. Like number are used for like references.

[0062] The multilayer outer sheath 105 comprises a first layer 106 being a separable layer and comprising a base polymer, a second layer 107, being a semiconductive layer comprising a base polymer a third layer 108 and a fourth layer 109 comprising a base polymer. The fourth layer 109 is non-conductive and arranged radially outside of the third layer 108 and radially inside of the first layer 106. The first layer 106 is arranged radially inside of the second layer 107, and the second layer 107 is the outermost layer of the power cable 101.

[0063] The fourth layer 109 is an intermediate layer between the third layer 108 typically acting as a damping layer to the metallic screen 104 and the first layer 106. The fourth 109 layer is non-conductive as it is beneficial that the separable layer 106 is not separated from a conductive or semiconductive layer. The fourth layer 109 may be HDPE.EXAMPLES

[0064] In the following, various samples were prepared and analyzed by specific material parameters. Each sample correspond to a previously described multilayer outer sheath.Example 1

[0065] A power cable was produced having a multilayer outer sheath consisting of three layers. In radial direction from inside, closest to the conductor, those three layers were: 1. A layer of linear low density polyethylene (LLDPE) 2. A layer of a separable polyolefin 3. A layer of semiconducting high density polyethylene (HDPE) including carbon black

[0066] The layers were produced by co-extrusion and the semiconducting layer was the outer layer of the power cable.Example 2

[0067] A power cable was produced having a multilayer outer sheath consisting of four layers. In radial direction from inside, closest to the conductor, those four layers were: 1. A layer of LLDPE 2. A layer of HDPE being non-conductive 3. A layer of a separable polyolefin 4. A layer of semiconducting HDPE including carbon black

[0068] The layers were produced by co-extrusion and the semiconducting layer was the outer layer of the power cable.

[0069] The aspects of the present disclosure have mainly been described above with reference to a few embodiments and examples thereof. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.

Claims

1. A power cable (1) comprising: a conductor (2) extending along a centre axis (C), an insulation system (3) arranged around the conductor, a metallic screen (4) arranged around the insulation system (3) and a multilayer outer sheath (5) arranged around the metallic screen (4), wherein the multilayer outer sheath (5) comprises: - a first layer (6) being a separable layer and comprising a base polymer, - a second layer (7), being a semiconductive layer comprising a base polymer, wherein the first layer (6) is arranged radially inside of the second layer (7), and wherein the second layer (7) is the outermost layer of the power cable (1).

2. The power cable (1) of claim 1, wherein the base polymer of the second layer (7) has a higher density than the base polymer of the first layer (6).

3. The power cable (1) of claim 1 or 2, wherein the base polymer of the second layer (7) is a polyolefin, polyvinyl chloride, PVC, polyamides, PA, thermoplastic elastomer, TPE, EPDM, ethylene-polypropylene rubber, EPR, silicone rubber, polyurethane, PUR, or chloroprene rubber, CR, preferably, the base polymer is polyethylene, more preferably medium density polyethylene, MDPE, or high density polyethylene, HDPE.

4. The power cable (1) of any one of the preceding claims, wherein the first layer (6) and the second layer (7) are in contact.

5. The power cable (1) of any one of the preceding claims, wherein the multilayer outer sheath comprises a third layer (8), wherein the first layer (6) is arranged radially outside of the third layer (8).

6. The power cable (1) of claim 5, wherein the multilayer outer sheath (5) comprises a fourth layer (9) comprising a base polymer, wherein the fourth layer (9) is non-conductive and arranged radially outside of the third layer (8) and radially inside of the first layer (6).

7. The power cable (1) of claim 6, wherein the base polymer of the fourth layer (9) is a polyolefin, polyvinyl chloride, PVC, polyamides, PA, thermoplastic elastomer, TPE, EPDM, ethylene-polypropylene rubber, EPR, silicone rubber, polyurethane, PUR, or chloroprene rubber, CR, preferably, the base polymer is polyethylene, more preferably medium density polyethylene, MDPE, or high density polyethylene, HDPE.

8. The power cable (1) of any one of the preceding claims, wherein the second layer (7) is thinner than the first layer (6).

9. The power cable (1) of any one of the preceding claims, wherein the power cable (1) is an asymmetric power cable having a non-circular cross-section.

10. The power cable (1, 101) of claim 9, comprising: - three power cores (10, 110), wherein each power core comprises the respective conductor (2, 102) extending along the centre axis (C) and the insulation system (3, 103) arranged around the conductor (2, 102), wherein - the cross-section of the power cable is generally triangular, wherein - the metallic screen (4, 104) is arranged around the three power cores (10, 110), and - the multilayer outer sheath (5, 105) is arranged around the metallic screen (4, 104).

11. The power cable (1) of any one of the preceding claims, wherein the first layer (6) is a non-conductive separable layer.

12. The power cable (1) of any one of the preceding claims, wherein the adhesion of the first layer 6 to its directly underlying layer is in the range of ≤45 N in a peel test according to HD 605 S3:2019.

13. The power cable (1) of any one of the preceding claims, wherein Shore D according to ASTM D2240-5(2021) is higher for the second layer (7) than for the first layer (6).

14. The power cable (1) of any one of the preceding claims, wherein the power cable is a medium voltage power cable or a high voltage power cable.

15. The power cable (1) of claim 14, wherein the power cable is a high voltage power cable having a voltage rating in a range of ≥1 kV.

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