CA2003427C - Electric power cable - Google Patents

Electric power cable

Info

Publication number
CA2003427C
CA2003427C CA002003427A CA2003427A CA2003427C CA 2003427 C CA2003427 C CA 2003427C CA 002003427 A CA002003427 A CA 002003427A CA 2003427 A CA2003427 A CA 2003427A CA 2003427 C CA2003427 C CA 2003427C
Authority
CA
Canada
Prior art keywords
composite tape
electric power
power cable
metal
moisture
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.)
Expired - Fee Related
Application number
CA002003427A
Other languages
French (fr)
Other versions
CA2003427A1 (en
Inventor
Neil Robert Plant
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.)
Prysmian Cables 2000 Ltd
Original Assignee
Phillips Cables Ltd
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 Phillips Cables Ltd filed Critical Phillips Cables Ltd
Publication of CA2003427A1 publication Critical patent/CA2003427A1/en
Application granted granted Critical
Publication of CA2003427C publication Critical patent/CA2003427C/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01BCABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B9/00Power cables
    • H01B9/02Power cables with screens or conductive layers, e.g. for avoiding large potential gradients
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01BCABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00Insulated conductors or cables characterised by their form
    • H01B7/17Protection against damage caused by external factors, e.g. sheaths or armouring
    • H01B7/28Protection against damage caused by moisture, corrosion, chemical attack or weather
    • H01B7/282Preventing penetration of fluid, e.g. water or humidity, into conductor or cable
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02ATECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A30/00Adapting or protecting infrastructure or their operation
    • Y02A30/14Extreme weather resilient electric power supply systems, e.g. strengthening power lines or underground power cables

Landscapes

  • Insulated Conductors (AREA)

Abstract

ABSTRACT
AN IMPROVED ELECTRIC POWER CABLE

In a single core or multi-core electric power cable, the dielectric screen of the or each cable core is surrounded by a moisture barrier consisting of a composite tape comprising a carrier layer of plastics material which is sandwiched between radially inner and outer metal foils bonded to the major surfaces of the carrier layer and electrically connected together. The composite tape surrounds the dielectric screen with its longitudinally extending edges overlapping and secured to one another throughout their lengths to form a moisture-tight seal. The moisture barrier so formed effects electrical interconnection between the underlying dielectric screen and a surrounding neutral, earth or ground conductor of the core. The moisture barrier is less expensive than moisture barriers hitherto proposed and used.

Description

AN IMPROVED ELECTRIC POWER CABLE
This invention relates to electric power cables of the kind comprising at least one cable core consisting of an electric conductor, an electrically conductive or semi-conductive conductor screen surrounding the conductor, a dielectric wall of electrically insulating material surrounding the conductor screen, an electrically conductive or semi-conductive dielectric screen surrounding the dielectric wall, a moisture-barrier surrounding the dielectric screen and, surrounding the moisture-barrier, a layer of metal or metal alloy suitable for use as a neutral, earth or ground conductor. An electric power cable of this construction will, for convenience, hereinafter be referred to as "an electric power cable of the kind described".
It is an object of the present invention to provide, in an electric power cable of the kind described, an improved moisture~barrier which can be readily applied during assembly of the or eaah cable core and which is substantially less expensive than moisture-barriers hitherto proposed and used.
In an electric power cable of the kind described in accordance with the invention, the moisture-barrier of the or each cable core consists of a composite tape comprising a carrier layer of plastics material which is sandwiched between radially inner and outer ~ "
2.

substantially fluid-impermeable foils of metal or metal alloy mechanically bonded to the major surfaces of the carrier layer and electrically connected together, which composite tape surrounds the dielectric screen of the core with its longitudinally extending edges overlapping - and secured to one another throughout their lengths to form a substantially moisture-tight seal between said overlapping edges, the moisture-barrier thereby effecting electrical interconnection between the underlying dielectric screen and the surrounding neutral, earth or ground conductor of the core.
By virtue of the fact that the improved moisture-barrier consists of a composite tape comprising a plastics carrier layer sandwiched between radially inner and outer foils of metal or metal alloy, the chances that a pin hole in one foil will immediately overlie or underlie a pin hole in the other foil are remote, with the result that the risk of moisture penetration is substantially reduced as compared with the same risk where a moisture barrier consists of a single foil of metal or metal alloy which may be prone to pin holes.
Electrical connection between the metal foils of the composite tape of the improved moisture barrier may be effected,by using for the carrier layer a plastics material which is sufficiently semi-conductive to 20~3427 electrically interconnect the metal foils but, with a view to keeping the moisture-barrier as inexpensive as possible, preferably electrical connection between the metal foils is effected, before the composite tape is applied over the dielectric screen, by folding a - longitudinally extending marginal portion of the composite tape in the same sense along two longitudinally extending transversely spaced lines so that the longitudinally extending part of said marginal portion of the composite tape nearer the longitudinally extending edge of the marginal portion is sandwiched between the other part of the marginal portion and the main portion of the composite tape; the two metal foils of the composite tape are thereby in a direct electrical contact.
The overlapping edges of the composite tape constituting the improved moisture barrier preferably are sealed together throughout their lengths by a double-sided adhesive tape or by a hot melt adhesive, the thickness of each of which may be approximately equal to three times the overall thickness of the composite tape~
The composite tape with said marginal portion of the tape folded as described may extend helically around the dielectric screen of the core but preferably the Z003~27 composite tape extends lengthwise along and is transversely folded around the dielectric screen.
The plastics material of the carrier layer of the composite tape of the improved moisture-barrier may be of polyethylene, polypropylene, polyester or any other - plastics material capable of withstanding the physical and thermal conditions to which it will be subjected when the cable is manufactured and installed and when the cable is in service.
Each metal foil of the composite tape of the improved moisture-barrier is preferably of aluminium but it may be of copper, lead or any other metal or metal alloy of high electrical conductivity which can be used in the form of a foil.
For ease of application to the underlying screened insulated conductor of the core, preferably the composite tape has an overall thickness lying in the range 1.5 to 5 mils (0.038 - 0.127mm). In a preferred embodiment, each foil of aluminium has a thickness of approximately 0.35 mil (0.009 mm) and the carrier layer of plastics material has a thickness of approximately 2 mils (0.051 mm).
Preferably, each metal foil of the composite tape is mechanically bonded to a ma~or surface of the carrier layer by a substantially continuous layer of hot-melt adhesive.

Where the electric power cable of the present invention is a single core cable, preferably the neutral, earth or ground conductor of the cable surrounding the moisture-barrier is a layer of helically wound wires of metal or metal alloy and, in this case, - preferably there is provided between the moisture-barrier and the layer of wires an electrically conductive bedding layer for the wires, e.g. a layer of helically applied semi-conductive fibrous tape or a water-swellable semi-conductive tape.
Where the electric power cable of the present invention is a multi-core cable, the neutral, earth or ground conductor of each cable core preferably comprises a layer of helically applied tape of metal or metal alloy.
The invention is further illustrated by a description, by way of example, of a preferred composite tape to be used to form the improved moisture barrier of a cable core and of a single core electric power cable incorporating the improved moisture barrier with reference to the accompanying drawings, in which:-Figure 1 is a traverse cross-sectional view, drawn on a greatly enlarged scale, of the preferred composite tape;
Figure 2 is a fragmental transverse cross-sectional view, drawn on a greatly enlarged scale, of the preferred method of effecting electrical connection between the metal foils of the composite tape shown in Figure l;
Figure 3 is a transverse cross-section~l diagrammatic view of the single core electric power cable, and Figure 4 is a fragmental transverse cross-sectional view, drawn on a greatly enlarged scale, of detail of the single core electric power cable shown in Figure 3.
Referring to Figure 1, the preferred composite tape 1 to be used to form the improved moisture barrier of a cable core comprises a carrier layer 2 of polyethylene having a thickness of approximately 2 mils (0.051 mm) which is sandwiched between fluid impermeable 15 foils 3 of aluminium, each having a thickness of `.
approximately 0.35 mils (0.009 mm), mechanically bonded to major surfaces of the carrier layer by a continuous layer 4 of hot melt adhesive.
Before composite tape 1 is to be used to form the improved moisture barrier of a cable core, as will be seen in referring to Figure 2 a longitudinally extending marginal portion of the composite tape i8 folded in the same sense along two longitudinally extending transversely spaced lines 5 and 6 so that the longitudinally extending part 9 of the marginal portion of the composite tape nearer the longitudinally extending edge of the marginal portion is sandwiched 20034;27 between the other part 8 of the marginal portion and the main part 7 of the composite tape 50 that the two aluminium foils 3 of the composite tape are directly electrically connected. The double-folded composite tape 1 as shown in Figure 2 is in a form suitable for - applying longitudinally to and foldinq transversely around the dielectric screen of a cable core.
The single core electric power cable shown in Figures 3 and 4 comprises an electric conductor 11, an electrically semi-conductive conductor screen 12 surrounding the conductor, a dielectric wall 13 of electrically insulating material surrounding the conductor screen, an electrically semi-conductive dielectric screen 14 surrounding the dielectric wall, a moisture barrier 15 surrounding the dielectric screen, a bedding layer 16 of helically applied semi-conductive fibrous tape surrounding the moisture barrier and, surrounding the layer of semi-conductive fibrous tape, a layer 17 of helically wound wires suitable for use as a neutral, earth or ground conductor.
The moisture barrier 15 of the cable core consists of the composite tape l which was initially folded as illustrated in Figure 2 and which has been longitudinally applied to and transversely folded around the dielectric screen 14 in such a way that longitudinally extending edges of the composite tape overlap and are secured to one another throughout their lengths to form a moisture-tight seal by a double-sided adhesive tape 18.
By virtue of the fact that the aluminium foils 3 of the composite tape 1 are in direct electrical contact along the double-folded marginal portion of the - composite tape, the moisture barrier 15 formed therefrom effects electrical interconnection between the underlying dielectric screen 14 and, via the bedding layer 16 of semi-conductive fibrous tape, the -surrounding layer 17 of helically wound wires constituting the neutral, earth or ground conductor of the core.

Claims (13)

1. An electric power cable comprising at least one cable core consisting of an electric conductor, a conductor screen surrounding the conductor, a dielectric wall of electrically insulating material surrounding the conductor screen, a dielectric screen surrounding the dielectric wall, a moisture-barrier surrounding the dielectric screen and, surrounding the moisture-barrier, a layer of metal or metal alloy, wherein the moisture-barrier of said at least one cable core consists of a composite tape comprising a carrier layer of plastics material which is sandwiched between radially inner and outer substantially fluid-impermeable foils of metal or metal alloy mechanically bonded to major surfaces of the carrier layer and electrically connected together, which composite tape surrounds the dielectric screen of the core with its longitudinally extending edges overlapping and secured to one another throughout their lengths to form a substantially moisture-tight seal between said overlapping edges, the moisture-barrier thereby effecting electrical interconnection between the underlying dielectric screen and the surrounding layer of metal or metal alloy.
2. An electric power cable as claimed in claim 1, wherein a longitudinally extending marginal portion of the composite tape of the moisture-barrier is folded along two longitudinally extending transversely spaced lines which define first and second portions of said marginal portion so that said first portion of said marginal portion of the composite tape including one of said longitudinally extending edges of said composite tape is sandwiched between said second portion of the marginal portion and a main portion of the composite tape, the two metal foils of the composite tape thereby being directly electrically connected.
3. An electric power cable as claimed in claim 1, wherein the overlapping edges of the composite tape are sealed together throughout their lengths by a hot-melt adhesive.
4. An electric power cable as claimed in claim 1, wherein said longitudinally extending edges of said composite tape are secured to one another by adhesive tape.
5. An electric power cable as claimed in claim 1, wherein electrical connection between the metal foils of the composite tape of the moisture-barrier is effected by using for the carrier layer a plastics material which is sufficiently semi-conductive to electrically interconnect the metal foils.
6. An electric power cable as claimed in claim 1, wherein the composite tape extends lengthwise along and is transversely folded around the dielectric screen.
7. An electric power cable as claimed in claim 1, wherein each metal foil of the composite tape is mechanically bonded to a major surface of the carrier layer by a substantially continuous layer of hot-melt adhesive.
8. An electric power cable as claimed in claim 1, wherein the plastics material of the carrier layer of the composite tape comprises polyethylene.
9. An electric power cable as claimed in claim 1, wherein each metal foil of the composite tape of the moisture-barrier comprises aluminium.
10. An electric power cable as claimed in claim 1, wherein the composite tape has an overall thickness lying in the range of 1.5 to 5 mils (0.038 to 0.127 mm).
11. An electric power cable as claimed in claim 10, wherein each foil of the composite tape comprises aluminium and has a thickness of approximately 0.35 mils (0.009 mm) and the carrier layer of the composite tape has a thickness of approximately 2 mils (0.051 mm).
12. An electric power cable as claimed in claim 1, which has a single core, wherein an electrically conductive bedding layer is sandwiched between the moisture-barrier and the surrounding layer of metal or metal alloy and wherein the layer of metal or metal alloy is a layer of helically wound wires.
13. An electric power cable as claimed in claim 1, which has at least two cable cores, wherein the layer of metal or metal alloy of each cable core comprises a layer of helically applied tape of metal or metal alloy.
CA002003427A 1988-11-25 1989-11-21 Electric power cable Expired - Fee Related CA2003427C (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8827628.2 1988-11-25
GB888827628A GB8827628D0 (en) 1988-11-25 1988-11-25 Improved electric power cable

Publications (2)

Publication Number Publication Date
CA2003427A1 CA2003427A1 (en) 1990-05-25
CA2003427C true CA2003427C (en) 1994-04-26

Family

ID=10647501

Family Applications (1)

Application Number Title Priority Date Filing Date
CA002003427A Expired - Fee Related CA2003427C (en) 1988-11-25 1989-11-21 Electric power cable

Country Status (2)

Country Link
CA (1) CA2003427C (en)
GB (2) GB8827628D0 (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2096066C (en) * 1993-05-12 1998-02-24 John Chung Chan Power cable with longitudinal waterblock elements
NO303755B1 (en) * 1996-12-10 1998-08-24 Alsthom Cge Alcatel Shielded cable
GB0418731D0 (en) * 2004-08-21 2004-09-22 Ventcroft Ltd Fire resistant cable and method of manufacture

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4327246A (en) * 1980-02-19 1982-04-27 Belden Corporation Electric cables with improved shielding members
US4406914A (en) * 1981-08-10 1983-09-27 Belden Corporation Slotless multi-shielded cable and tape therefor

Also Published As

Publication number Publication date
GB8827628D0 (en) 1988-12-29
GB2225480B (en) 1992-08-12
CA2003427A1 (en) 1990-05-25
GB8926657D0 (en) 1990-01-17
GB2225480A (en) 1990-05-30

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