Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B7/00—Insulated conductors or cables characterised by their form
  • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
  • H01B7/18—Protection against damage caused by wear, mechanical force or pressure; Sheaths; Armouring
  • H01B7/1805—Protections not provided for in groups H01B7/182 - H01B7/26
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B7/00—Insulated conductors or cables characterised by their form
  • H01B7/04—Flexible cables, conductors, or cords, e.g. trailing cables
  • H01B7/045—Flexible cables, conductors, or cords, e.g. trailing cables attached to marine objects, e.g. buoys, diving equipment, aquatic probes, marine towline
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B7/00—Insulated conductors or cables characterised by their form
  • H01B7/02—Disposition of insulation
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B7/00—Insulated conductors or cables characterised by their form
  • H01B7/02—Disposition of insulation
  • H01B7/0208—Cables with several layers of insulating material
  • H01B7/0225—Three or more layers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B7/00—Insulated conductors or cables characterised by their form
  • H01B7/14—Submarine cables
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B7/00—Insulated conductors or cables characterised by their form
  • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
  • H01B7/18—Protection against damage caused by wear, mechanical force or pressure; Sheaths; Armouring
  • H01B7/182—Protection against damage caused by wear, mechanical force or pressure; Sheaths; Armouring comprising synthetic filaments
  • H01B7/183—Protection against damage caused by wear, mechanical force or pressure; Sheaths; Armouring comprising synthetic filaments forming part of an outer sheath
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B7/00—Insulated conductors or cables characterised by their form
  • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
  • H01B7/18—Protection against damage caused by wear, mechanical force or pressure; Sheaths; Armouring
  • H01B7/22—Metal wires or tapes, e.g. made of steel
  • H01B7/226—Helicoidally wound metal wires or tapes

Definitions

• the present disclosure generally relates to power cables. In particular it relates to dynamic submarine power cables.
• Submarine power cables typically comprise a conductor and an electrical insulation system. Power cables of this type may further comprise a screen arranged around the electrical insulation system for carrying earth fault, and capacitive current and leakage currents. For medium voltage cables, without a metallic sheath, helically laid copper wires or overlapping copper tape is normally used as screen.
• Submarine power cables may be designed to be utilised in dynamic
• Dynamic submarine power cable may for example be hanging into the sea from an offshore structure.
• the submarine power cable will thus be exposed to wave-induced bending forces as well as to varying degrees of tension.
• the screen will therefore be exposed to fatigue stresses.
• the magnitude of the fatigue stresses depends on the design of the screen, contact forces and friction coefficient between the screen and surrounding layers.
• the contact force onto each core depends on the tensile force in the cable, radial pressure from sheaths and contact with surrounding structures such as a bend stiffener or bell mouth.
• the helix geometry of the screen wires allows the screen wires to slip in order to release axial stresses built up when the submarine power cable is bent.
• the main stresses in the screen wires resulting from bending are 1.) local bending stress due to bending of the screen wire, and 2.) friction stresses resulting from the stick-slip behaviour of the helical screen wire when the power cable is bent.
• the diameter of the screen wires is comparatively small and the bending stresses of the wire will therefore not contribute significantly to the fatigue stresses in the wire.
• the friction stresses which are related to the contact forces onto the wire and the friction coefficient, are significantly larger compared to the bending stresses since they are related to the radial distance from the centre of the core to the screen wire.
• the friction stresses are thus more important for the fatigue life of the screen wires than the local bending stress.
• the friction stresses increase with increasing contact forces onto the screen wire.
• the contact forces onto the screen wires increase with increasing forces onto the cores for instance due to larger tensile force in the cable.
• an object of the present disclosure is to solve, or at least mitigate, the problems of the prior art.
• a dynamic submarine power cable comprising: a first conductor, a first insulation system layer arranged around the first conductor, a first sheath arranged around the first insulation system layer, and a first screen layer arranged between the first insulation system layer and the first sheath, wherein the first screen layer comprises a plurality of first screen wires each having a first diameter and a plurality of first polymer wires each having a second diameter which is larger than the first diameter, wherein the first screen wires and the first polymer wires are arranged in a helical manner around the first insulation system layer, along the axial direction of the first conductor, and wherein in any cross-section of the dynamic submarine power cable the first screen wires and the first polymer wires are arranged alternatingly along the periphery of the first insulation system layer, wherein a radial distance between the central axis of any of the first screen wires and the central axis of the first conductor is less than a radi
• first screen wires will be subjected to less radial contact forces and hence reduced friction stress, in particular because they do not contact the first sheath as a result of the position of the larger diameter first polymer wires.
• the first polymer wires will hence transmit the majority of any radial forces onto the cores.
• Polymers have a higher mechanical strength in terms of being able to withstand large strains compared to metallic screen wires acting as means for shielding. To this end, the risk of fatigue failure of the first screen wires is greatly reduced.
• each first polymer wire simultaneously abuts both the first insulation system layer and the first sheath.
• the number of first screen wires is equal to the number of first polymer wires.
• the second diameter is at least 1.2 times greater than the first diameter.
• each first polymer wire consists of a polymer material.
• One embodiment comprises a second conductor, a second insulation system layer arranged around the second conductor, a second sheath arranged around the second insulation system layer, and a second screen layer arranged between the second insulation system layer and the second sheath, wherein the second screen layer comprises a plurality of second screen wires each having said first diameter and a plurality of second polymer wires each having said second diameter, wherein the second screen wires and the second polymer wires are arranged in a helical manner around the second insulation system layer, along the axial direction of the second conductor, and wherein in any cross-section of the dynamic submarine power cable the second screen wires and the second polymer wires are arranged alternatingly along the periphery of the second insulation system layer, wherein a radial distance between the central axis of any of the second screen wires and the central axis of the second conductor is less than a radial distance between the central axis of any of the second polymer wires and the central axis of the second conductor.
• each second polymer wire simultaneously abuts both the second insulation system layer and the second sheath.
• the number of second screen wires is equal to the number of second polymer wires. According to one embodiment each second screen wire is made of metal.
• each second polymer wire consists of a polymer material.
• One embodiment comprises a third conductor, a third insulation system layer arranged around the third conductor, a third sheath arranged around the third insulation system layer, a third screen layer arranged between the third insulation system layer and the third sheath, wherein the third screen layer comprises a plurality of third screen wires each having said first diameter and a plurality of third polymer wires each having said second diameter, wherein the third screen wires and the third polymer wires are arranged in a helical manner around the third insulation system layer, along the axial direction of the third conductor, and wherein in any cross-section of the dynamic submarine power cable the third screen wires and the third polymer wires are arranged alternatingly along the periphery of the third insulation system layer, wherein a radial distance between the central axis of any of the third screen wires and the central axis of the third conductor is less than a radial distance between the central axis of any of the third polymer wires and the central axis of the third conductor.
• each third polymer wire simultaneously abuts both the third insulation system layer and the third sheath.
• the number of third screen wires is equal to the number of third polymer wires.
• each third polymer wire consists of a polymer material.
• the first sheath forms part of a first core
• the second sheath forms part of a second core
• the third sheath forms part of a third core
• the dynamic submarine power cable comprises an armouring layer comprising a plurality of armouring wires, three filler devices, each filler device being arranged between a respective pair of adjacent cores of the first core, the second core and the third core, wherein the armouring layer is arranged around the first core, the second core, the third core and the three filler devices, and an outer sheath arranged around the armouring layer.
• the dynamic submarine power cable is a medium voltage power cable or a high voltage power cable.
• Fig. 2 shows one of the cores of the dynamic submarine power cable in Fig. 1.
• the dynamic submarine power cable comprises a conductor, an insulation system, comprising an insulation system layer, arranged around the conductor, a sheath arranged around the insulation system layer, and a screen layer arranged between the insulation system layer and the sheath.
• the conductor, the insulation system layer, the screen layer and the sheath are hence concentrically or essentially concentrically arranged.
• the screen layer is arranged to provide electrical shielding of the conductor.
• the insulation system layer may for example be a semiconducting layer, for example a cross-linked polyethylene (XLPE) layer comprising carbon black.
• the insulation system layer may define or form part of an electrical insulation system.
• the electrical insulation system may thus comprise one or more insulation system layers.
• the insulation system layers may be different; one layer may for example be an electrically insulating layer and one or more layers may for example be semiconducting layer(s).
• an electrical insulation system may comprise three concentrically arranged insulation system layers, an inner semiconducting layer, an outer semiconducting layer, and an electrically insulating layer arranged between the inner semiconducting layer and the outer semiconducting layer.
• the conductor, the insulation system layer, the screen layer and the sheath forms or forms part of a core of the dynamic submarine power cable.
• the dynamic submarine power cable furthermore comprises one or more armouring layer(s) arranged around the screen layer, and an outer sheath.
• the screen layer comprises a plurality of screen wires each having a first diameter and a plurality of polymer wires each having a second diameter that is larger than the first diameter.
• Each screen wire is normally circular or essentially circular in cross section, and typically consists of a single wire or a plurality of thinner parallel wires which together form a screen wire with a circular or essentially circular cross section.
• Each polymer wire is typically circular or essentially circular in cross-section.
• Other cross-sectional shapes of the polymer wires are also contemplated; the polymer wires may for example have a square-shaped cross-section, or other polygonal cross- sectional shape such as hexagonal or octagonal cross-sectional shape.
• the second diameter is preferably at least 1.2 times greater than the first diameter, for example 1.5 times greater, 1.7 times greater or 2 times greater than the first diameter.
• the screen wires and the polymer wires are arranged helically around the insulation system layer.
• the screen wires and the polymer wires are preferably arranged in tension such that that they abut the insulation system layer.
• the screen wires and the polymer wires are arranged alternatingly with one or more screen wires arranged between every adjacent pair of polymer wires. To this end, the central axis of each screen wire is closer to the central axis of the conductor than the central axis of any polymer wire.
• the screen wires may be made of an electrically conductive material, preferably metal such as copper.
• the polymer wires may comprise or consist of a polymer.
• An example of a polymeric material suitable for the polymer wires is polyethylene such as low density, medium density or high density polyethylene.
• the polymeric wires could alternatively be made of
• the polymer wires may advantageously be made of the same material as either the insulation system layer or the sheath. No new material, which would have to be subjected to comprehensive testing in the context of the dynamic submarine power cable, is introduced into the design of the dynamic submarine power cable in this manner.
• the dynamic submarine power cable may comprise more than one core depending on the number of electrical phases and whether the dynamic submarine power cable is for AC use or DC use.
• each conductor is surrounded by a respective insulation system layer, sheath and screen layer in the same manner as described above, thereby forming or forming part of a respective core.
• the first screen layer 9a comprises a plurality of first screen wires 13a and a plurality of first polymer wires 15a.
• the plurality of first screen wires 13a and the plurality of first polymer wires 15a are evenly distributed around the periphery of the first insulation system layer 7a.
• the first screen wires 13a and the first polymer wires 15a are arranged in an alternating manner around the periphery of the first insulation system layer 7a.
• first screen wires 13a and the first polymer wires 15a are arranged in a helical manner around the first insulation system layer 7a in the axial direction of the first conductor 5a.
• the first screen wires 13a and the first polymer wires 15a are arranged in tension such that they all lie against, i.e. bear on, the outer surface of the first insulation system layer 7a.
• the number of first screen wires 13a hence equals the number of first polymer wires 15a.
• Each first screen wire 13a hence abuts two first polymer wires 15a and is squeezed in between two first polymer wires 15a to ensure that it lies essentially still and in physical contact with the first insulation system layer 7a.
• Each first screen wire 13a has a first diameter Di and each first polymer wire 15a has a second diameter D2, which second diameter D2 is greater than the first diameter Di, as shown in Fig. 2.
• Each first polymer wire 15a hence simultaneously abuts both the layer radially inside the first screen layer 9a and the layer radially outside the first screen layer 9a, e.g. the first insulation system layer 7a and the first sheath 11a.
• the first screen wires 13a however normally only abut the first insulation system layer 7a due to their tensioned state.
• the first screen wires 13a will therefore not be subjected to, or at least be subjected to substantially less, radial contact loads thereby reducing the build-up of frictional stress due to stick-slip during dynamic load conditions.
• the polymer material of the first polymer wires 15a is able to withstand large strain variations due to bending as well as frictional forces better than the first screen wires 13a, the latter being made of an electrically conductive material to provide electrical shielding of the first conductor 5a.
• the second diameter D2 is at least 1.2 times greater than the first diameter Di, according to one example at least 1.5 times greater than the first diameter Di. According to a further example, the second diameter D2 is at least 1.7 times or 2 times greater than the first diameter Di.
• the ratio between the first diameter Di and the second diameter D2 shall be chosen on the basis that when e.g. the first core is subjected to radial loads
• the radial dimension, in the first screen layer, of any first polymer wire, due to ovalisation and penetration into adjacent layers, is larger than the first diameter Di.
• the first polymer wires are hence the only wires that are in physical contact with the first sheath.
• the first polymer wires therefore bear all radial load.
• the first screen wires do not contact the sheath.
• the ratio between the first diameter Di and the second diameter D2 will thus depend on a number of design parameters, for example on the sheath material of the core, on the hardness of the sheath material, on the material of the first polymer wires 15a, and on the magnitude of the radial forces onto the cores during operation of the dynamic submarine power cable 1.
• the second core 3b is identical to the first core 3a and to the third core.
• the second core 3b for example, comprises a second conductor 5b, a second insulation system layer 7b arranged around the second conductor 5b, a second screen layer 9b comprising a plurality of second screen wires 13b and a plurality of second polymer wires 15b, and a second sheath 11b. Since the second core 3b and the third core 3c are identical to the first core 3a, the second core 3b and the third core 3c will not be described in any further detail herein.
• the dynamic submarine power cable 1 further comprises three filler devices 17, each filler device 17 being arranged between a respective pair of two adjacent cores of the first core 3a, the second core 3b and the third core 3c.
• the filler device 17 shown in Fig. 1 is arranged between the first core 3a and the second core 3b.
• the dynamic submarine power cable 1 comprises an armouring layer 19 and an outer sheath 23 arranged around the armouring layer 19.
• the armouring layer 19 comprises a plurality of helically wound armouring wires 21 arranged around the periphery formed by the first core 3a, the second core 3b, the third core 3c and the three filler devices 17.
• the armouring wires 21 may typically be arranged around the periphery of an intermediate sheath that is arranged around the three cores 3a, 3b, 3c and the three filler devices 17.
• Fig. 2 shows half of the first core 3a in cross section.
• the radial distance di between the central axis of any of the first screen wires 13a and the central axis of the first conductor 5a is less than the radial distance d2 between the central axis of any of the first polymer wires 15a and the central axis of the first conductor 5a.
• the first screen wires 13a are only in physical contact with the inner layer of the two layers surrounding the first screen layer 9a, i.e. with the first insulation system layer 7a. Radial loads onto the core during operation are hence absorbed by the first polymer wires 15a.
• the core configuration shown in Fig. 2 could be used in dynamic submarine power cables for AC applications, with the number of cores depending on the number of electrical phases, or for DC applications.

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• Engineering & Computer Science (AREA)
• Ocean & Marine Engineering (AREA)
• Insulated Conductors (AREA)
• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)

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• 2015
  • 2015-04-10 WO PCT/EP2015/057795 patent/WO2016162076A1/en not_active Ceased
  • 2015-04-10 BR BR112017020821-0A patent/BR112017020821B1/pt active IP Right Grant
  • 2015-04-10 JP JP2017552829A patent/JP6543352B2/ja active Active
  • 2015-04-10 ES ES15715263T patent/ES2718068T3/es active Active
  • 2015-04-10 KR KR1020177031769A patent/KR102300410B1/ko active Active
  • 2015-04-10 US US15/562,623 patent/US10083778B2/en active Active
  • 2015-04-10 EP EP15715263.8A patent/EP3281209B1/en active Active
  • 2015-04-10 AU AU2015390863A patent/AU2015390863B2/en active Active
  • 2015-04-10 CA CA2982202A patent/CA2982202C/en active Active

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