EP4024412A1 - Kabelkonstruktion für hochspannungskabel und qualifizierungsverfahren zur bewertung von kabeln - Google Patents

Kabelkonstruktion für hochspannungskabel und qualifizierungsverfahren zur bewertung von kabeln Download PDF

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Publication number
EP4024412A1
EP4024412A1 EP20306704.6A EP20306704A EP4024412A1 EP 4024412 A1 EP4024412 A1 EP 4024412A1 EP 20306704 A EP20306704 A EP 20306704A EP 4024412 A1 EP4024412 A1 EP 4024412A1
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EP
European Patent Office
Prior art keywords
cable
power cable
insulation layer
electric
insulation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP20306704.6A
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English (en)
French (fr)
Inventor
Øyvind IVERSEN
Torunn Lund Clasen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nexans SA
Original Assignee
Nexans SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nexans SA filed Critical Nexans SA
Priority to EP20306704.6A priority Critical patent/EP4024412A1/de
Publication of EP4024412A1 publication Critical patent/EP4024412A1/de
Pending legal-status Critical Current

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    • 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
    • H01B7/42—Insulated conductors or cables characterised by their form with arrangements for heat dissipation or conduction
    • H01B7/421—Insulated conductors or cables characterised by their form with arrangements for heat dissipation or conduction for heat dissipation
    • H01B7/423—Insulated conductors or cables characterised by their form with arrangements for heat dissipation or conduction for heat dissipation using a cooling fluid
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B9/00—Power cables

Definitions

  • the present invention relates to power cables and more particular to insulation layers of medium and high voltage power cables.
  • the present invention also relates to a qualification method for rating a power cable.
  • the dimension and type of insulation system required for a power cable depends on the transmission voltage as higher voltage increase the electric gradient and charging current and thus requiring a more robust insulation to prevent breakdown of the insulation layer of the power cable.
  • the cross-section area of the conductor is often increased in order to decrease dielectric stress and draining of charging current of the cable.
  • a power cable is rated for a given voltage range from maximum (Um) to minimum with an associated insulation thickness according to standards such as IEC 60502-2 (power cable with Um 7.2 kV up to 36 kV), IEC 60840 (power cables with Um 36 kV up to Um 170 kV) and IEC 63026 (submarine power cables). If a cable design is just above the maximum voltage for a given voltage range such as 52 kV, 72.5 kV, 123kV, 145kV, 170kV, 245kV, 300kV, it automatically falls into the next voltage range, resulting in an increase in insulation thickness and cost.
  • the present invention has as its objects to overcome one or more of the disadvantages of the prior art by increasing the dimension of the insulation layer around the conductors beyond the defined standard and industry practice.
  • the inventors have surprisingly been able to design medium and high voltage power cables, i.e. cables with maximum voltage level above 36 kV, with a wet design i.e. cables traditionally comprising a metallic water barrier by demonstrating that the cables according to the invention wherein thickness of insulation layer above nominal standards limit charging currents, surprisingly without oversizing the total cable design.
  • the insulation system of the medium and high voltage power cables according to the invention provides cables with reduced dielectric stress without having to increase the conductor cross section area normally applied for decreasing dielectric stress in power cables.
  • a power cable comprising an electric conductor, an inner semi-conducting screen surrounding said conductor, an insulating layer surrounding said inner semi-conducting screen and an outer semi-conducting screen surrounding said insulating layer wherein the cable has a predefined maximum voltage level (Um) above 36 kV and wherein the insulation layer has an outer diameter (dy) and the inner diameter (di) defining the thickness of the insulation layer wherein the cable has a wet design.
  • the electric gradient (Ex) is the electric gradient (Ei) measured at di.
  • predefined maximum voltage level (Um) is from 36 kV to 700 kV.
  • predefined maximum voltage level (Um) is from 36 kV to 650 kV.
  • predefined maximum voltage level (Um) is from 36 kV to 300 kV.
  • predefined maximum voltage level (Um) is from 36 kV to 245 kV.
  • the power cable is a medium voltage power cable.
  • the power cable is a high voltage power cable.
  • the cable does not comprise a metallic water barrier.
  • the electric gradient (Ei) at the inner diameter (di) of the insulation layer range from 1.5 kV/mm to 3.5 kV/mm for a power cable having a predefined maximum voltage level, Um of 36 kV.
  • the electric gradient (Ei) at the inner diameter (di) of the insulation layer range from 1.5 kV/mm to 4.5 kV/mm for a power cable having a predefined maximum voltage level, Um of 52 kV.
  • the electric gradient (Ei) at the inner diameter (di) of the insulation layer range from 1.5 kV/mm to 5.0 kV/mm for a power cable having a predefined maximum voltage level, Um of 72 kV.
  • the electric gradient (Ei) at the inner diameter (di) of the insulation layer range from 1.5 kV/mm to 6.5 kV/mm for a power cable having a predefined maximum voltage level, Um of 123 kV.
  • the electric gradient (Ei) at the inner diameter (di) of the insulation layer range from 1.5 kV/mm to 10 kV/mm for a power cable having a predefined maximum voltage level, Um of 170 kV.
  • the electric gradient (Ei) at the inner diameter (di) of the insulation layer range from 1.5 kV/mm to 12 kV/mm for a power cable having a predefined maximum voltage level, Um of 245 kV.
  • the first aspect insulating layer is a polymer layer based on a crosslinked polyolefin.
  • the crosslinked polyolefin is selected from the group consisting of crosslinked polyethylene (XLPE), a crosslinked ethylene-propylene, a crosslinked ethylene-propylene-diene elastomer (EPDM), polypropylene (PP) and any combination thereof.
  • XLPE crosslinked polyethylene
  • EPDM crosslinked ethylene-propylene-diene elastomer
  • PP polypropylene
  • the power cable is three-phase cable.
  • the power cable is single-phase cable.
  • the power cable is an Alternating Current (AC) power cable or a Direct Current (DC) power cable.
  • AC Alternating Current
  • DC Direct Current
  • the power cable is a Direct Electric Heating (DEH) cable system.
  • DEH Direct Electric Heating
  • the cable is for use under water, under ground or in the air.
  • the cable is for use under water.
  • the insulation layer is dimensioned with an outer diameter (dy) in order to provide a decrease in charging current.
  • the present invention provides a qualification method for rating a power cable comprising an electric conductor, an inner semi-conducting screen surrounding said conductor, an insulating layer surrounding said inner screen and an outer semi-conducting screen surrounding said insulating layer wherein the cable has a predefined maximum voltage level (Um), a wet design and the insulation layer has an outer diameter (dy) and the inner diameter (di) defining thickness of the insulation layer, wherein the method comprises:
  • the thickness of the insulation layer is dimensioned to provide a decrease of Ex in order to keep E x equal to or below a prequalified Ex for said cable.
  • Ex range from 1.5 kV to 12 kV/mm.
  • the electric gradient (Ex) is the electric gradient (Ei) measured at di.
  • the cable has a predefined maximum voltage level (Um) from 7.2 kV to 36 kV.
  • the cable has a predefined maximum voltage level (Um) above 36 kV.
  • the insulation layer is dimensioned to provide a decrease in charging current.
  • Figure 1 depicts a cross section of a conductor and insulation layer according to the invention.
  • wet design is defined herein as a cable without a metallic water barrier and the outer semi-conducting layer of the electric power cable is in direct contact with water or its surroundings.
  • the term also includes a cable with polymeric jacket(s) over the outer semi-conducting layer to limit rate of water vapour ingress.
  • dry design is defined herein as a cable with a continuous hermetic metallic water barrier such as lead extrusion or any other form of metal extrusion such as copper, or longitudinally welded metallic sheath.
  • the term also includes a cable with a metallic foil radial water barrier with a longitudinal glued overlap and bonded to an outer polymeric jacket.
  • the term may also include a hybrid version with lapped metallic tapes where the intersection which is filled with polymers for water migration to occur, cf. CIGRE TB 722.
  • the medium and high voltage power cables according to the present invention does not comprise a "dry design", i.e. is without a metallic water barrier.
  • insulated conductor it is meant an electrical conductor 1 surrounded by an insulating system comprising, an inner semiconducting layer 2 surrounding the conductor, an insulating layer 3 surrounding the inner semiconducting layer, and an outer semiconducting layer 4 surrounding the insulating layer as depicted in figure 1 .
  • the thickness or dimension of the insulation layer is defined according to the present invention as the difference between the outer diameter (dy) of the insulation layer and the inner diameter of the insulation layer (di).
  • dielectric stress is maximum at the inner diameter of the insulation layer (di) and minimum at outer diameter of the insulation layer (dy).
  • the dielectric stress decreases from the inner diameter of the insulation layer (di) to the outer diameter of the insulation layer (dy).
  • a non - uniform distribution of dielectric stress leads to insulation break down in the cable. To avoid this insulation break down, the dielectric stress is distributed throughout the dielectric material.
  • a dielectric material is an electrical insulator that can be polarized by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor but only slightly shift from their average equilibrium positions causing dielectric polarization.
  • dielectric stress is defined herein as the maximum voltage required to produce a dielectric breakdown through the insulation material and is expressed in terms of Volts per unit thickness, for example kV/mm.
  • the inner diameter of the insulation layer (di) 6 ( figure 1 ) is predefined by the conductor of the cable.
  • a power cable comprising an electric conductor, an inner semi-conducting screen surrounding said conductor, an insulating layer surrounding said inner semi-conducting screen and an outer semi-conducting screen surrounding said insulating layer wherein the cable has a predefined maximum voltage level (Um) above 36 kV and wherein the insulation layer has an outer diameter (dy) and an inner diameter (di) and thickness of the insulation layer is defined as the difference between the outer diameter (dy) and the inner diameter (di) wherein the cable has a wet design; and in an embodiment
  • a power cable according to the present invention comprises an electric conductor 1 , an inner semi-conducting screen 2 surrounding said conductor, an insulating layer 3 surrounding said inner screen and an outer semi-conducting screen 4 surrounding said insulating layer.
  • the electrical insulation is chosen according to the conductor material of the electrical medium and high voltage power cable. If the conductor material of the power cable is copper, then the electrical insulation will be an insulation material which is suitable for a copper conductor. If the conductor material of the power cable is aluminium, or aluminium alloy then the electrical insulation will be an insulation material which is suitable for an aluminium conductor.
  • the medium or high voltage power cable according to the invention can be an electric direct current (DC) power transmission cable or an electric alternating current (AC) power transmission cable.
  • DC direct current
  • AC electric alternating current
  • the power cable according to the invention may be a Direct Electric Heating (DEH) cable system.
  • DEH is a flow assurance technology developed to safeguard the well stream through the pipeline to the platform.
  • the pipe is heated by running alternating or direct current through the steel in the pipe.
  • the power cable according to the present invention may also be one of many elements such as multiple power cables, fiber optical cables or tubes bundled together in a single slender structure.
  • Subsea power cables may also include one or more dedicated load bearing armoring elements in the shape of steel wires or another material if needed.
  • Power cables comprise one or more cores or conductors, usually disposed within outer layers of insulating materials.
  • Power cables typically comprise one or more insulated conductors.
  • Cables with a single insulated conductor are also referred to as “single-core” cables, while cables with more than one insulated conductor are also referred to as “multi-core” cables; for example, cables with three insulated conductors are referred to as “3-core” cables.
  • the power cables according to the invention may be cables submerged in sea or fresh waters, submarine water cables or land cables.
  • a power cable according to the invention is preferably a power cable submerge in sea or fresh water, i.e. under water.
  • An electric insulation system 3 ( figure 1 ) may comprise one or more insulation layers.
  • the electrically insulating layer may be a polymer layer based on a crosslinked polyolefin, such as a crosslinked polyethylene (XLPE) or a crosslinked ethylene/propylene or ethylene/propylene/diene elastomer (EPDM) polypropylene (PP) and any combination thereof.
  • a crosslinked polyolefin such as a crosslinked polyethylene (XLPE) or a crosslinked ethylene/propylene or ethylene/propylene/diene elastomer (EPDM) polypropylene (PP) and any combination thereof.
  • the present invention provides a a qualification method for rating a power cable comprising an electric conductor (1), an inner semi-conducting screen (2) surrounding said conductor (1), an insulating layer (3) surrounding said inner screen and an outer semi-conducting screen (4) surrounding said insulating layer wherein the cable has a predefined maximum voltage level Um, a wet design and the insulation layer has an outer diameter (dy) and an inner diameter (di) defining thickness of the insulation layer, wherein the method comprises :
  • the thickness of insulation layer is dimensioned to provide a decrease of Ex in order to keep E x equal to or below a prequalified Ex for said cable and provide a decrease in charging current.
  • a skilled person knows how to perform prequalification tests for direct current (DC) or alternating (AC) current power transmission cable for example according to CIGRE TB 496, CIGRE TB 722, IEC 60502-2, IEC 60840 or IEC 62067.
  • Ex range from 1.5 kV to 12 kV/mm.
  • the electric gradient (Ex) is the electric gradient (Ei) measured at di.
  • the cable has a predefined maximum voltage level (Um) from 7.2 kV to 36 kV.
  • the cable has a predefined maximum voltage level (Um) above 36 kV.
  • a medium or high voltage power transmission cable with a maximum voltage level above 36 kV can have a wet design and preventing the use of a metallic water barrier by providing a dimension of the insulation layer around the conductors beyond the defined standard and industry practice.
  • the dimension of the insulation layer and thus the thickness of the insulation layer is defined by an outer diameter of the insulation layer and an inner diameter of the insulation layer wherein the dimension of the insulation layer is providing a reduction charging current and of the electric gradient over the insulation layer in order to keep the electric gradient equal to or below the prequalified electric gradient for the cable.
  • Ex is defined as the electric gradient equal to or below the prequalified electric gradient for the cable.
EP20306704.6A 2020-12-29 2020-12-29 Kabelkonstruktion für hochspannungskabel und qualifizierungsverfahren zur bewertung von kabeln Pending EP4024412A1 (de)

Priority Applications (1)

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EP20306704.6A EP4024412A1 (de) 2020-12-29 2020-12-29 Kabelkonstruktion für hochspannungskabel und qualifizierungsverfahren zur bewertung von kabeln

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Application Number Priority Date Filing Date Title
EP20306704.6A EP4024412A1 (de) 2020-12-29 2020-12-29 Kabelkonstruktion für hochspannungskabel und qualifizierungsverfahren zur bewertung von kabeln

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EP4024412A1 true EP4024412A1 (de) 2022-07-06

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EP20306704.6A Pending EP4024412A1 (de) 2020-12-29 2020-12-29 Kabelkonstruktion für hochspannungskabel und qualifizierungsverfahren zur bewertung von kabeln

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150041171A1 (en) * 2012-02-20 2015-02-12 Aker Subsea As Arrangement for cooling power cables, power umbilicals and cables

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150041171A1 (en) * 2012-02-20 2015-02-12 Aker Subsea As Arrangement for cooling power cables, power umbilicals and cables

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
JAMES YOUNG: "Innovative 72 kV Wet-Design Cables for Dynamic Deepwater Power Umbilicals", 5 April 2017 (2017-04-05), pages 1 - 14, XP055808782, Retrieved from the Internet <URL:https://mcedd.com/wp-content/uploads/2017/Proceedings/04/MCEDD%20Slide%20Outline%202017%20James%20Young%20JDR%20R1.pdf> [retrieved on 20210528] *

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