GB2165690A - Electrical cables - Google Patents

Electrical cables Download PDF

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Publication number
GB2165690A
GB2165690A GB08524318A GB8524318A GB2165690A GB 2165690 A GB2165690 A GB 2165690A GB 08524318 A GB08524318 A GB 08524318A GB 8524318 A GB8524318 A GB 8524318A GB 2165690 A GB2165690 A GB 2165690A
Authority
GB
United Kingdom
Prior art keywords
electrical
water
cable
cables
surrounded
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.)
Granted
Application number
GB08524318A
Other versions
GB2165690B (en
GB8524318D0 (en
Inventor
Timothy George Marsh
Anthony Edward Williamson
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.)
Associated Electrical Industries Ltd
Original Assignee
Associated Electrical Industries 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 Associated Electrical Industries Ltd filed Critical Associated Electrical Industries Ltd
Publication of GB8524318D0 publication Critical patent/GB8524318D0/en
Publication of GB2165690A publication Critical patent/GB2165690A/en
Application granted granted Critical
Publication of GB2165690B publication Critical patent/GB2165690B/en
Expired legal-status Critical Current

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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
    • H01B7/28—Protection against damage caused by moisture, corrosion, chemical attack or weather
    • H01B7/282—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable
    • H01B7/285—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable by completely or partially filling interstices in the cable
    • H01B7/288—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable by completely or partially filling interstices in the cable using hygroscopic material or material swelling in the presence of liquid
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B11/00—Communication cables or conductors
    • H01B11/22—Cables including at least one electrical conductor together with optical fibres
    • 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
    • H01B7/28—Protection against damage caused by moisture, corrosion, chemical attack or weather
    • H01B7/2813—Protection against damage caused by electrical, chemical or water tree deterioration
    • 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

Landscapes

  • Insulated Conductors (AREA)
  • Communication Cables (AREA)

Abstract

In order to reduce the risk of "water-tree growth" on the surface of a conductor in an electrical underwater cable, the conductor 1 is surrounded by an extruded aluminum sheath 2 having a water-impermeable medium 7 therein. A semiconductor screen 3 surrounds the sheath and a layer of insulation 4 is provided around the screen. Several such cables may be stranded together with optical cables in an outer sheath. The water-impermeable medium may be petroleum jelly mixed with bentonite, or sodium carboxymethyl cellulose. <IMAGE>

Description

SPECIFICATION Improvements relating to electrical cables This invention relates to improvements in electrical cables, but it may also have applications in composite electrical/optical cables.
Electrical cables generally consist of at least one electrical conductor, which may consist of several wires stranded together, surrounded by a layer of insulation possibly with a semiconductor screen between the conductor and the insulation so as to equalise the electrical stresses.
When such cables are used underwater, such as for submarine cables, a water impermeable compound such as Bentonite in petroleum jelly may be provided in the interstices between the conductor wires. However, water may nevertheless seep into the cable and spread along the surface of the conductors where it could initiate what is known as "water-tree growth". This can cause deterioration and ultimate breakdown of the insulation, and is clearly undesirable.
It is thus an object of the present invention to provide a cable in which such water-tree growth is prevented from affecting the insulation.
Accordingly, the invention provides an electrical cable comprising at least one electrical conductor surrounded by an extruded aluminium sheath having a water-impermeable compound therein, a semiconductor screen surrounding said aluminium sheath and a layer of insulation around the semiconductor screen.
Preferably, the electrical conductor is made up of several electrically conducting wires stranded together.
The water impermeable compound may be petroleum jelly which may have Benonite mixed in it, or may be a water blocking material such as sodium carboxymethyl cellulose.
The aluminium sheathing provides a water barrier thus preventing "water-tree growth" affecting the insulation and also provides a smooth interface between the conductor and the semiconductor screen. The invention is thus particularly applicable to high voltage submarine cables.
When used in composite electrical/optical cables, several electrical cables of the type described above may be stranded together with optical fibres in the interstices or may possibly be stranded together with known optical cables.
In either case an outer protective sheath will normally be applied.
The invention will be further explained by describing by way of example, with reference to figs. 1 and 2 of the accompanying drawing, two difference embodiments of it.
The electrical cable 8 illustrated in Fig. 1 comprises an electrical conductor consisting of a plurality, in the case seven, wires 1 stranded together, surrounded by an extruded layer of aluminium 2 in electrical contact with the wires. The layer of aluminium 2 is surrounded by a semi-conductor screen 3 which, in turn, is surrounded by a layer of insulation 4. The layer of insulation 4 may be surrounded by an outer protective sheath 5. The wires 1 have between them several interstices 6 which are provided with a water-impermeable compound 7 therein. Different numbers of stranded together wires may be similarly incorporated in a cable structure of this form.
Fig. 2 shows a multiconductor cable structure 9 incorporating three electrical cable elements 10 constructed in the same manner as the cable 8 of Fig. 1 but without the outer sheaths 5, the elements 10 being stranded together and surrounded by a common extruded outer sheath 11. The structure 9 may include, a plurality, in this case three, optical cable elements 12 as described below stranded together with the conducting elements within the outer sheath 11. Each optical cable element 12 may consist, as shown, of one or more optical fibres 13 loosely accommodated within a channel 14 surrounded by a protective casing 15 although other forms of optical elements may be employed.The interstices 6 between the electrical cable elements 10, between the electrical cable elements 10 and optical cable elements 12 and between the electrical cable elements 10, optical cable elements 12 and the outer sheath 11 may also include a water blocking material 7.
1. An electrical cable comprising at least one electrical conductor surrounded by an extruded aluminium sheath having a water-impermeable compound therein, a semiconductor screen surrounding said aluminium sheath and a layer of insulation around the semiconductor screen.
2. An electrical cable according to Claim 1, wherein the electrical conductor is made up of a plurality of electrically conducting wires stranded together.
3. An electrical cable according to Claim 1 or 2, wherein the water impermeable compound is petroleum jelly.
4. An electrical cable according to Claim 3, wherein the petroleum jelly has Bentonite mixed in it.
5. An electrical cable according to Claim 1 or 2, wherein the water impermeable compound is a water blocking material.
6. An electrical cable according to Claim 3, wherein the water blocking material is sodium carboxymethyl cellulose.
7. An electrical cable according to any preceding claim wherein an outer protective sheath is applied.
8. An electrical cable substantially as herein described with reference to Fig. 1 of the accompanying drawing.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements relating to electrical cables This invention relates to improvements in electrical cables, but it may also have applications in composite electrical/optical cables. Electrical cables generally consist of at least one electrical conductor, which may consist of several wires stranded together, surrounded by a layer of insulation possibly with a semiconductor screen between the conductor and the insulation so as to equalise the electrical stresses. When such cables are used underwater, such as for submarine cables, a water impermeable compound such as Bentonite in petroleum jelly may be provided in the interstices between the conductor wires. However, water may nevertheless seep into the cable and spread along the surface of the conductors where it could initiate what is known as "water-tree growth". This can cause deterioration and ultimate breakdown of the insulation, and is clearly undesirable. It is thus an object of the present invention to provide a cable in which such water-tree growth is prevented from affecting the insulation. Accordingly, the invention provides an electrical cable comprising at least one electrical conductor surrounded by an extruded aluminium sheath having a water-impermeable compound therein, a semiconductor screen surrounding said aluminium sheath and a layer of insulation around the semiconductor screen. Preferably, the electrical conductor is made up of several electrically conducting wires stranded together. The water impermeable compound may be petroleum jelly which may have Benonite mixed in it, or may be a water blocking material such as sodium carboxymethyl cellulose. The aluminium sheathing provides a water barrier thus preventing "water-tree growth" affecting the insulation and also provides a smooth interface between the conductor and the semiconductor screen. The invention is thus particularly applicable to high voltage submarine cables. When used in composite electrical/optical cables, several electrical cables of the type described above may be stranded together with optical fibres in the interstices or may possibly be stranded together with known optical cables. In either case an outer protective sheath will normally be applied. The invention will be further explained by describing by way of example, with reference to figs. 1 and 2 of the accompanying drawing, two difference embodiments of it. The electrical cable 8 illustrated in Fig. 1 comprises an electrical conductor consisting of a plurality, in the case seven, wires 1 stranded together, surrounded by an extruded layer of aluminium 2 in electrical contact with the wires. The layer of aluminium 2 is surrounded by a semi-conductor screen 3 which, in turn, is surrounded by a layer of insulation 4. The layer of insulation 4 may be surrounded by an outer protective sheath 5. The wires 1 have between them several interstices 6 which are provided with a water-impermeable compound 7 therein. Different numbers of stranded together wires may be similarly incorporated in a cable structure of this form. Fig. 2 shows a multiconductor cable structure 9 incorporating three electrical cable elements 10 constructed in the same manner as the cable 8 of Fig. 1 but without the outer sheaths 5, the elements 10 being stranded together and surrounded by a common extruded outer sheath 11. The structure 9 may include, a plurality, in this case three, optical cable elements 12 as described below stranded together with the conducting elements within the outer sheath 11. Each optical cable element 12 may consist, as shown, of one or more optical fibres 13 loosely accommodated within a channel 14 surrounded by a protective casing 15 although other forms of optical elements may be employed.The interstices 6 between the electrical cable elements 10, between the electrical cable elements 10 and optical cable elements 12 and between the electrical cable elements 10, optical cable elements 12 and the outer sheath 11 may also include a water blocking material 7. CLAIMS
1. An electrical cable comprising at least one electrical conductor surrounded by an extruded aluminium sheath having a water-impermeable compound therein, a semiconductor screen surrounding said aluminium sheath and a layer of insulation around the semiconductor screen.
2. An electrical cable according to Claim 1, wherein the electrical conductor is made up of a plurality of electrically conducting wires stranded together.
3. An electrical cable according to Claim 1 or 2, wherein the water impermeable compound is petroleum jelly.
4. An electrical cable according to Claim 3, wherein the petroleum jelly has Bentonite mixed in it.
5. An electrical cable according to Claim 1 or 2, wherein the water impermeable compound is a water blocking material.
6. An electrical cable according to Claim 3, wherein the water blocking material is sodium carboxymethyl cellulose.
7. An electrical cable according to any preceding claim wherein an outer protective sheath is applied.
8. An electrical cable substantially as herein described with reference to Fig. 1 of the accompanying drawing.
9. An electrical cable structure substantially as herein described with reference to Fig. 2 of the accompanying drawing.
GB08524318A 1984-10-08 1985-10-02 Electrical cables Expired GB2165690B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB848425378A GB8425378D0 (en) 1984-10-08 1984-10-08 Electrical cables

Publications (3)

Publication Number Publication Date
GB8524318D0 GB8524318D0 (en) 1985-11-06
GB2165690A true GB2165690A (en) 1986-04-16
GB2165690B GB2165690B (en) 1987-10-28

Family

ID=10567858

Family Applications (2)

Application Number Title Priority Date Filing Date
GB848425378A Pending GB8425378D0 (en) 1984-10-08 1984-10-08 Electrical cables
GB08524318A Expired GB2165690B (en) 1984-10-08 1985-10-02 Electrical cables

Family Applications Before (1)

Application Number Title Priority Date Filing Date
GB848425378A Pending GB8425378D0 (en) 1984-10-08 1984-10-08 Electrical cables

Country Status (1)

Country Link
GB (2) GB8425378D0 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2193583B (en) * 1986-08-07 1990-05-16 Telephone Cables Ltd Optical cables
WO1997015258A2 (en) * 1995-10-24 1997-05-01 Camelot Superabsorbents Limited Absorbent articles
US7783147B2 (en) 2001-11-19 2010-08-24 Prysmian Cables & Systems Limited Optical fibre drop cables
EP2863398A1 (en) * 2013-10-18 2015-04-22 Nexans Water and gas tight stranded conductor and umbilical comprising this
EP3002763A1 (en) * 2002-05-27 2016-04-06 NKT Cables Group A/S An insulated electrical cable

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1277505A (en) * 1969-11-19 1972-06-14 British Insulated Callenders Improvements in or relating to telecommunication cables
GB1290905A (en) * 1968-12-02 1972-09-27
US3918281A (en) * 1973-11-21 1975-11-11 Pirelli Method for sheathing a cable core with the core surrounded by impregnating fluid during sheathing
GB1448617A (en) * 1973-10-01 1976-09-08 Gen Cable Corp Telecommunication cables
GB1523433A (en) * 1975-09-15 1978-08-31 Delta Enfield Cables Ltd Electric cables
GB2080998A (en) * 1980-07-21 1982-02-10 Pirelli Treficable Telecommunications Cable

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1290905A (en) * 1968-12-02 1972-09-27
GB1277505A (en) * 1969-11-19 1972-06-14 British Insulated Callenders Improvements in or relating to telecommunication cables
GB1448617A (en) * 1973-10-01 1976-09-08 Gen Cable Corp Telecommunication cables
US3918281A (en) * 1973-11-21 1975-11-11 Pirelli Method for sheathing a cable core with the core surrounded by impregnating fluid during sheathing
GB1523433A (en) * 1975-09-15 1978-08-31 Delta Enfield Cables Ltd Electric cables
GB2080998A (en) * 1980-07-21 1982-02-10 Pirelli Treficable Telecommunications Cable

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2193583B (en) * 1986-08-07 1990-05-16 Telephone Cables Ltd Optical cables
WO1997015258A2 (en) * 1995-10-24 1997-05-01 Camelot Superabsorbents Limited Absorbent articles
WO1997015258A3 (en) * 1995-10-24 1997-08-14 Camelot Superabsorbents Ltd Absorbent articles
US7783147B2 (en) 2001-11-19 2010-08-24 Prysmian Cables & Systems Limited Optical fibre drop cables
EP3002763A1 (en) * 2002-05-27 2016-04-06 NKT Cables Group A/S An insulated electrical cable
EP2863398A1 (en) * 2013-10-18 2015-04-22 Nexans Water and gas tight stranded conductor and umbilical comprising this

Also Published As

Publication number Publication date
GB8425378D0 (en) 1984-11-14
GB2165690B (en) 1987-10-28
GB8524318D0 (en) 1985-11-06

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Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee

Effective date: 19991002