US3749812A - High voltage cable - Google Patents

High voltage cable Download PDF

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Publication number
US3749812A
US3749812A US00240510A US3749812DA US3749812A US 3749812 A US3749812 A US 3749812A US 00240510 A US00240510 A US 00240510A US 3749812D A US3749812D A US 3749812DA US 3749812 A US3749812 A US 3749812A
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United States
Prior art keywords
cable
paper
dielectric
polypropylene
conductor
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Expired - Lifetime
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US00240510A
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English (en)
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E Reynolds
D Edwards
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Individual
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B9/00—Power cables
    • H01B9/06—Gas-pressure cables; Oil-pressure cables; Cables for use in conduits under fluid pressure
    • H01B9/0611—Oil-pressure cables
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H01B13/30—Drying; Impregnating

Definitions

  • the polypropylene is selected for low solubility in the oil, and the paper has a density of 0.85Mg/m or less, an imperrneabilityv of at least 10,000 Gurley seconds, and a thickness, at least in the inner high-stresszoneof the dielectric, of 50 micrometers or less, preferably 25 micrometers.
  • cables for service at the highest voltages invariablyhave dielectrics formed of lapped insulatingpaper tapes impregnated with a mobile hydrocarbon oil (ordinarily a selected and refined petroleum oil) maintained under pressure.
  • This type of dielectric has a dissipation factor of approximately 0.25 0.5 percent which at voltages up to around ,150 kV results in the loss of only a few percent of'the MVA rating of a cable. Losses increase rapidly, however, with increased voltage, and it has, been recognised that at a voltage of the order of SOOkV lMV it will become grossly uneconomic if not physically impos'sibleto transmit useful amounts of power by such cables.
  • the invention uses as the tape from which the dielectric is built up a laminate comprising a centre layer of polypropylene and two outer layers of cellulosic paper.
  • the paper layers fulfil three functions: they make it easy to establish and maintain impregnation of the tapes in situ on the cable; they improve the handling properties of the tapes; and they influence the swelling of the polypropylene layer when impregnated.
  • the third function is very important, and we have found that it is essential to use one specific type of laminate if adequate control is to be obtained, namely an extrusion-bonded laminate formed'by extruding a web of polypropylene from a slot die at an appropriate elevated temperature, typically about 300C, and before it cools trapping it between and bonding it by pressure to two paper webs which are at a much lower temperature (normally ambient temperature).
  • an extrusion-bonded laminate formed'by extruding a web of polypropylene from a slot die at an appropriate elevated temperature, typically about 300C, and before it cools trapping it between and bonding it by pressure to two paper webs which are at a much lower temperature (normally ambient temperature).
  • This type of laminate as prestressed laminate because in the normal working temperature range (and in the absence of impregnant) the paper layers hold the polypropylene layer in an elastically extended condition.
  • cellulosic paper is meant'paper consisting substantially entirely of cellulose fibres.
  • the paper layers of the laminate should be much thinner than normal cable papers; in no case should the thickness of a paper layer exceed 80 micrometers and in the inner highstress zone of the dielectric where the electrical stress is greatest the paper layers should have a thickness less than micrometers, preferably about 25 micrometers.
  • the paper should also be of low density, specifically with a density less than 0.85Mg/m and preferably less than JS g/ 'I R. Nevertheless the pape'r should I y have an impermeability at least as great as that of nor mal cable papers, that is 10,000 Gurley seconds or higher.
  • the preferred paper is an uncalendered electrical grade paper of intermediate fibre length of a density 0.7 g cm and a Gurley impermeability greater than 10,000 seconds.
  • Such a paper is Kraft coil winding paper manufactured generally in accordance with BS 698:1956, Class IA to the very high standard of chemical purity normally associated with capacitor tissue.
  • the paper layers can be loaded with an active material of the kind described in the Complete Specification of United Kingdom Pat. Specification v1,185,474, that is aluminium oxide or another active metal oxide, hydrated metal oxide, hydroxide, carbonate or basic carbonate that has sorptive powers comparable with that of aluminium oxide, in order to minimise the deterioration in electrical properties due to contamination of the impregnant by residues from the plastics material.
  • an active material of the kind described in the Complete Specification of United Kingdom Pat. Specification v1,185,474, that is aluminium oxide or another active metal oxide, hydrated metal oxide, hydroxide, carbonate or basic carbonate that has sorptive powers comparable with that of aluminium oxide, in order to minimise the deterioration in electrical properties due to contamination of the impregnant by residues from the plastics material.
  • the function of the paper in controlling swelling is of greater importance in outer parts of the dielectric, since inner parts will be restrained alsoby the overlying tapes of the outer parts.
  • the dielectric from a number of different composite tapes such that the proportion of the dielectric that is constituted by plastics material decreases with increasing distance from the cable conductor.
  • the number of steps desirable will increase with the dielectric wall thickness and therefore with the working voltage of the cable.
  • using polypropylene as the plastics material and a normal low viscosity cable oil as the impregnant where the dielectric wall thickness is 10 mm there will suitably be two steps and where the dielectric wall thickness is 25 mm three steps may be desirable.
  • the dielectric may throughout its length comprise an inner part of the composite tape and an outer part of paper; and in another example the composite tape may be utilised only in restoring the dielectric at joints and terminations.
  • the optimal thicknesses of the plastics and paper layers of the composite tape used in the joints and terminations may differ from the optimal thicknesses of the corresponding layers in the cable, owing to the different stress distribution.
  • our invention requires the use as impregnant of a selected and refined mineral oil that is substantially free of naphthenes.
  • Paraffinic oils can be used, but mixed paraffinic/aromatic mineral oils have better lowtemperature properties.
  • the viscosity of the oil should be less than 57 centistokes at C and less than ll centistokes at 60 C. Preferably the viscosity is less than centistokes at 25 C.
  • the laminate is preferably,
  • the dielectric will normally be bounded at its inner and outer surfaces by a conductor screen and a dielectric screen respectively.
  • a conductor screen and a dielectric screen are preferably formed from single or mul tiple layers of laminated tape similar to that used to form the whole or part of the dielectric suitably metallised and/or loaded with carbon or other conductive material.
  • Preferably all three layers of the laminate are loaded with conductive material but in some circumstances, for the outer layer of a conductor screen or the inner layer of a dielectric screen, a triple laminate with one paper layer not loaded may be used, that is the paper layers contiguous with the dielectric.
  • the paper not loaded with conductive material is preferably loaded with aluminium oxide or other active material of the kind referred to in an application of the first-named Applicant divided from Ser. No. 20670 filed Mar. 18, 1970.
  • the conductor screen is preferably lapped with metal tape before the conductor screen is applied. Phosphor bronze tapes with a thickness of around 0.1 mm (5 mil) have been found satisfactory for this purpose.
  • FIG. 1 is a cut-away diagram
  • FIG. 2 is a transverse cross-section of the cable
  • FIG. 3 is an enlarged cross-section of a small'portion of the cable dielectric.
  • FIG. 1 is a steel tape helix defining a central oil duct within the metallic conductor 2.
  • a conductor screen 3 Over the conductor is applied a conductor screen 3, dielectric 4 more fully described below, and dielectric screen 5, the screens 3 and 5 being formed of metallised tapes or tapes loaded with conductive material as already discussed.
  • the cable is completed by a lead sheath 6, bronze tape or other pressure-resisting reinforcement 7 and a plastics oversheath 8.
  • the radial thickness of the dielectric 4 is 5.5 mm, corresponding to a design stress of 16 MV/m.
  • the whole of the dielectric is made up of composite tapes comprising 50 p.m of polypropylene sandwiched between two paper layers each 25 pm thick.
  • the dielectric comprises three concentric parts each having aradial thickness of approximately 3.5 mm, each part being formed from composite tapes comprising a layer of polypropylene sandwiched between two paper layers.
  • the polypropylene layer is 80 ;:.m thick and each paper layer 10 pm thick; in the tapes of the intermediate part, the polypropylene layer is 50 pun thick and each paper layer 25 um'thick; and in the tapes of the outer part, the polypropylene layer is only 20 pm thick and each paper layer is 40 pm thick.
  • the dielectric in the third example, which is a 400 kV cable, the dielectric comprises four concentric parts each having a radial thickness of approximately 6.25 mm.
  • the three inner parts are each formed of composite tape in which central polypropylene layers have thicknesses of 60 40 and 20 pm respectively beginning with the innermost layer, and each of the paper layers has thicknesses of 20, 40 and p.m respectively.
  • the outer part is formed from tapes of ordinary cable insulating paper 250 m thick.
  • the paper used in the composite tape is the preferred uncalendered electrical grade of paper referred to above and the composite is prestressed by making it in the manner described above.
  • the impregnant in each case is a naphthene-free refined mineral oil having a viscosity in the range 12.5 l5 centistokes at 20 C.
  • a power cable for a working voltage of at least 200 kV comprising a central load-carrying conductor, a dielectric wall built up from lapped tapes impregnated with insulating fluid and an overall fluid-tight sheath, distinguished by the said dielectric having the following characteristics in combination, namely that a. said fluid is a refined mineral oilsubstantially free of naphthenic constituents and having a viscosity of less than 57 centistokes at 20 C and less than 11 centistokes at 60 C and b.
  • said tapes are fonned of an extrusion-bonded laminate comprising a centre layer of a polypropylene that is substantially insoluble in said fluid and two outer layers of cellulosic paper, which paper layers have i. a thickness not greater than 50 micrometers ii. a density less than 0.85Mg/rn, and
  • a cable as claimed in claim 6 wherein a further, radially outermost, part of the dielectric comprises paper tapes.
  • a cable as claimed in claim 1 wherein said paper is an uncalendered electrical grade paper of intermediate flbre length of density 0.7 Mg/rn.
  • a cable as claimed in claim 1 comprising a conductor screen defining the radially inner surface of said dielectric well and formed from a conductive extrusion-bonded laminate comprising a central layer of said tral conductor is a stranded conductor and wherein a lapped metal tape is interposed between said central conductor and said conductor screen.
  • a cable as claimed in claim 1 comprising a dielectric screen defining the radially outer surface of said dielectric wall and formed from a conductive extrusionbonded laminate comprising a central layer of' said polypropylene and two outer layers of cellulosic paper.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Organic Insulating Materials (AREA)
  • Drilling And Boring (AREA)
  • Insulating Bodies (AREA)
  • Laminated Bodies (AREA)
US00240510A 1969-10-22 1972-04-03 High voltage cable Expired - Lifetime US3749812A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB5178369 1969-10-22

Publications (1)

Publication Number Publication Date
US3749812A true US3749812A (en) 1973-07-31

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ID=10461370

Family Applications (1)

Application Number Title Priority Date Filing Date
US00240510A Expired - Lifetime US3749812A (en) 1969-10-22 1972-04-03 High voltage cable

Country Status (10)

Country Link
US (1) US3749812A (de)
CA (1) CA922000A (de)
CH (1) CH523580A (de)
DE (1) DE2051562C3 (de)
FR (1) FR2065473B1 (de)
GB (1) GB1311867A (de)
IT (1) IT1019007B (de)
NO (1) NO133386C (de)
SE (1) SE376814B (de)
ZA (1) ZA707101B (de)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4117260A (en) * 1977-08-17 1978-09-26 Comul Scope Company Coaxial drop wire
US4118593A (en) * 1975-12-05 1978-10-03 Industrie Pirelli Societa Per Azioni Process for manufacturing multi-core electric power cables and cables so-produced
US4376229A (en) * 1980-09-16 1983-03-08 Raychem Corporation Shielded conduit
US4487991A (en) * 1983-07-15 1984-12-11 The United States Of America As Represented By The United States Department Of Energy Fully synthetic taped insulation cables
US4602121A (en) * 1984-01-17 1986-07-22 Societa' Cavi Pirelli S.P.A. Oil-filled electric cable with alternate layers of plastic and paper tape insulation
US4853490A (en) * 1985-11-08 1989-08-01 Societa' Cavi Pirelli S.P.A. Laminated paper-plastic insulating tape and cable including such tape
US4859804A (en) * 1983-09-09 1989-08-22 Sumitomo Electric Industries Electric power supply cable using insulating polyolefin laminate paper
US4994632A (en) * 1988-10-21 1991-02-19 Societa' Cavi Pirelli S.P.A. Electric cable with laminated tape insulation
EP0684614A1 (de) 1994-05-24 1995-11-29 PIRELLI CAVI S.p.A. Hochspannungskabel
US5481070A (en) * 1992-06-26 1996-01-02 Sumitomo Electric Industries, Ltd. Direct current oil-filled self contained cable
US6399878B2 (en) * 1998-02-03 2002-06-04 Sumitomo Electric Industries, Ltd. Solid cable, manufacturing method thereof, and transmission line therewith
US20060054281A1 (en) * 2004-09-10 2006-03-16 Pingree Richard E Jr Hydrocarbon dielectric heat transfer fluids for microwave plasma generators
US20120285725A1 (en) * 2009-12-16 2012-11-15 Mauro Maritano High voltage direct current cable having an impregnated stratified insulation
US20200051713A1 (en) * 2017-02-16 2020-02-13 Ls Cable & System Ltd. Power cable

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2002684B (en) * 1977-08-06 1982-02-17 Showa Electric Wire & Cable Co Laminated insulating paper and oil-filled cable insulated thereby

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3194872A (en) * 1963-04-23 1965-07-13 Gen Cable Corp Paper and polyolefin power cable insulation
US3427394A (en) * 1966-11-14 1969-02-11 Phelps Dodge Copper Prod High voltage cable

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB854774A (en) * 1958-06-05 1960-11-23 British Insulated Callenders Improvements in electric power cables
GB1185474A (en) * 1967-01-02 1970-03-25 British Insulated Callenders Improvements in Electrical Apparatus Incorporating a Laminated Dielectric.
US3594489A (en) * 1968-10-07 1971-07-20 Gen Cable Corp Extra high voltage cables

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3194872A (en) * 1963-04-23 1965-07-13 Gen Cable Corp Paper and polyolefin power cable insulation
US3427394A (en) * 1966-11-14 1969-02-11 Phelps Dodge Copper Prod High voltage cable

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4118593A (en) * 1975-12-05 1978-10-03 Industrie Pirelli Societa Per Azioni Process for manufacturing multi-core electric power cables and cables so-produced
US4117260A (en) * 1977-08-17 1978-09-26 Comul Scope Company Coaxial drop wire
US4376229A (en) * 1980-09-16 1983-03-08 Raychem Corporation Shielded conduit
US4487991A (en) * 1983-07-15 1984-12-11 The United States Of America As Represented By The United States Department Of Energy Fully synthetic taped insulation cables
US4859804A (en) * 1983-09-09 1989-08-22 Sumitomo Electric Industries Electric power supply cable using insulating polyolefin laminate paper
US4602121A (en) * 1984-01-17 1986-07-22 Societa' Cavi Pirelli S.P.A. Oil-filled electric cable with alternate layers of plastic and paper tape insulation
US4704170A (en) * 1984-01-17 1987-11-03 Societa' Cavi Pirelli S.P.A. Method of making an oil-filled electric cable with alternate layers of plastic and paper tape insulation
US4853490A (en) * 1985-11-08 1989-08-01 Societa' Cavi Pirelli S.P.A. Laminated paper-plastic insulating tape and cable including such tape
US4994632A (en) * 1988-10-21 1991-02-19 Societa' Cavi Pirelli S.P.A. Electric cable with laminated tape insulation
EP0365873B1 (de) * 1988-10-21 1994-01-19 PIRELLI CAVI S.p.A. Elektrisches Kabel
US5481070A (en) * 1992-06-26 1996-01-02 Sumitomo Electric Industries, Ltd. Direct current oil-filled self contained cable
EP0684614A1 (de) 1994-05-24 1995-11-29 PIRELLI CAVI S.p.A. Hochspannungskabel
US5850055A (en) * 1994-05-24 1998-12-15 Pirelli Cavi S.P.A. High voltage cable
US6399878B2 (en) * 1998-02-03 2002-06-04 Sumitomo Electric Industries, Ltd. Solid cable, manufacturing method thereof, and transmission line therewith
US20060054281A1 (en) * 2004-09-10 2006-03-16 Pingree Richard E Jr Hydrocarbon dielectric heat transfer fluids for microwave plasma generators
US7338575B2 (en) * 2004-09-10 2008-03-04 Axcelis Technologies, Inc. Hydrocarbon dielectric heat transfer fluids for microwave plasma generators
US20120285725A1 (en) * 2009-12-16 2012-11-15 Mauro Maritano High voltage direct current cable having an impregnated stratified insulation
US9595367B2 (en) * 2009-12-16 2017-03-14 Prysmian S.P.A. High voltage direct current cable having an impregnated stratified insulation
US20200051713A1 (en) * 2017-02-16 2020-02-13 Ls Cable & System Ltd. Power cable
US11049631B2 (en) * 2017-02-16 2021-06-29 Ls Cable & System Ltd. Power cable

Also Published As

Publication number Publication date
DE2051562A1 (de) 1971-04-29
SE376814B (de) 1975-06-09
FR2065473A1 (de) 1971-07-30
CA922000A (en) 1973-02-27
NO133386B (de) 1976-01-12
FR2065473B1 (de) 1975-01-10
ZA707101B (en) 1971-08-25
GB1311867A (en) 1973-03-28
CH523580A (de) 1972-05-31
DE2051562B2 (de) 1980-02-28
DE2051562C3 (de) 1980-10-23
IT1019007B (it) 1977-11-10
NO133386C (no) 1981-09-04

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