US3780206A - Electric cables - Google Patents

Electric cables Download PDF

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Publication number
US3780206A
US3780206A US00202553A US3780206DA US3780206A US 3780206 A US3780206 A US 3780206A US 00202553 A US00202553 A US 00202553A US 3780206D A US3780206D A US 3780206DA US 3780206 A US3780206 A US 3780206A
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dielectric
loaded
active
finely divided
conductive carbon
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US00202553A
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E Reynolds
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Balfour Beatty PLC
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BICC PLC
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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
    • H01B9/00—Power cables
    • H01B9/02—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients
    • H01B9/027—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients composed of semi-conducting layers

Definitions

  • This invention relates to conductive or semiconductive fibrous material in sheet form suitable for use as an electric screen in contact with the dielectric fluid of high-voltage cables and other electrical apparatus having a fluid impregnated dielectric.
  • the invention is especially concerned with the dielectric and conductor screens of oil-filled electric cables which may be of the pipe type or of the selfcontained type having one or more internal oil ducts. It has as its principal object the provision of a permeable material for this purpose that is capable of protecting the dielectric material against contamination and that is less liable to contaminate the dielectric and/or its impregnant than are permeable materials hitherto used.
  • the material in accordance with the invention is a conductive or semi-conductive fibrous material in the form of a flexible sheet loaded both with conductive carbon and with active finely divided material selected from the group consisting of aluminium oxide and such other metal oxides, hydrated metal oxides, metal hydroxides, metal carbonates and basic metal carbonates as have adsorptive powers comparable with that of active finely divided aluminium oxide.
  • active finely divided material selected from the group consisting of aluminium oxide and such other metal oxides, hydrated metal oxides, metal hydroxides, metal carbonates and basic metal carbonates as have adsorptive powers comparable with that of active finely divided aluminium oxide.
  • aluminium oxide and titanium dioxide are preferred, in that order.
  • aluminium oxide or other active substances in the manner disclosed in U.K. Pat. No. 874,981 except that instead of incorporating these substances in a paper or other dielectric material suitable for use as a dielectric as claimed in that patnet, they are incorporated in fibrous materials suitable for use as a conducting or semi-conducting screen.
  • the invention includes cables, especially cables having an impregnated dielectric such as oil-filled cables, in which the fibrous materials are used either as a conductor screen or as a dielectric screen or both. Normally, at least two layers of the loaded fibrous material will be used in each screen, the layers breaking joint.
  • the invention also includes multi-ply fibrous sheet materials in which at least one but not all plies is loaded with the active material and conductive carbon.
  • the invention also includes multi-ply fibrous sheet materials in which at least one but not all plies is loaded with conductive carbon but not with active alumina or other active material and at least one of the remaining plies is loaded with such active material but not with conductive carbon.
  • such sheet material may be applied over an underlying layer of material loaded with conductive carbon, with the ply or plies that is or are loaded with active alumina or other active material on the outside (that is adjacent to the dielectric) but to avoid exposure of the conductive carbon loaded paper to the oil in the butt spaces between the turns of the multi-ply sheet material, it is preferable to apply a multi-ply sheet material over an underlying layer of material loaded with both active alumina and conductive carbon.
  • a similar but inverted construction may be used in forming a dielectric screen.
  • the quantities and type of conductive carbon used will be substantially the same as in conventional carbon loaded paper used for this purpose.
  • the particle size of the alumina or otheractive substance must be such that it does notinterfere with the paper making process; colloidal particles are preferably used. Although less than 2 percent of the active substance based on the weight of the paper can be used, since its effectiveness is a function of the quantity used larger quantities, e.g. 8-10 percent, are preferred.
  • the active substance must be substantially free from ionic impurities that would deleteriously affect the electrical properties of the dielectric and before incorporation in the paper it is preferably subjected to the same tests as is paper for use as the dielectric of electric cables and other electrical apparatus, i.e., tests for conductivity and acidity/alkinility of the aqueous extract.
  • the substance must not be overheated during the activation process to the extent that fusion of the particles occurs, since this would materially reduce the adsorptive power and by virtue of the increased crystalinity and abrasiveness interfer with the felting of the paper fibres.
  • the carbon and the alumina, or other active substance can each be incorporated in the fibrous material either during manufacture, i.e., by addition to the pulp in the case of paper either at the hydro pulper or the beater, or after manufacture by impregnation of the fibrous material with a suspension of the material or materials.
  • the invention is mainly concerned with sheet material based on paper of the quality normally used as the dielectric in high voltage cables, other fibrous sheet materials, both natural and synthetic, that are compatible with the dielectric materials can alternatively be used.
  • the sheet material in accordance with the invention is intended primarily to act as a barrier inhibiting the migration into the dielectric of ionic impurities carried by the fluid impregnant, which impurities may for example be derived from metals with which the fluid comes into contact within the electrical apparatus or in ancillary apparatus through which the fluid is circulated, for example the metal of cable conductors, enclosing pipes or cable sheaths, binding tape applied to the dielectric, external heat exchangers, and circulating pumps.
  • the alumina or other active substance may also inhibit migration of carbon or other semi-conducting particles derived from carbon black from the fibrous material into the adjacent dielectric or the impregnant therefor.
  • FIGS. 1 & 2 show two forms of fibrous sheet material in accordance with the invention; and FIG. 3 shows in cross-section a cable having a conductor screen and a dielectric screen of the material in accordance with the invention.
  • the presence of the alumina or other active substance will greatly increase the adsorptive power for contaminating ions of the paper or other fibrous material by virtue of the much higher adsorptive index of the alumina or other active substance as compared with the activated carbon.
  • the presence of the alumina or other active substance will however not substantially affect the permeability of the loaded fibrous material and hence will not obstruct the passage of moisture from the dielectric during the drying of the dielectric prior to impregnation.
  • the sheet materials in accordance with the invention have the advantage over carbon loaded papers hitherto used that when used instead of such materials as the conductor and/or the dielectric screen of a high voltage cable with an oil impregnated dielectric they reduce the rate at which the power factor of the cable increases over a long period of service.
  • An electric cable comprising a. at least one metallic conductor
  • a fluid impregnated dielectric surrounding said conductor and bounded at each of its inner and outer circumferential surfaces by an electric screen in contact with said fluid and formed from a fibrous material in the form of a flexible sheet loaded with conductive carbon black and c. an external fluid-tight sheath, said cable being characterized in that the said fibrous material of said electric screens comprises distinct plies loaded respectively with said conductive carbon black and with an active finely divided adsorbent material selected from the group consisting of aluminum oxide and such other active metallic oxides, hy-
  • An electric cable comprising a. at least one metallic conductor
  • a fluid impregnated dielectric surrounding said conductor and bounded at each of its inner and outer circumferential surfaces by an electric screen in contact with said fluid and formed from a fibrous material in the form of a flexible sheet loaded with conductive carbon black and c.
  • the said cable being characterized in that the said electric screens each comprise a first layer of a multi-ply fibrous sheet material comprising one ply contiguous with the dielectric and loaded with an active finely divided adsorbent material selected from the group consisting of aluminum oxide and such other active metallic oxides, hydrated metal oxides, metal hydroxides, metal carbonates and basic metal carbonates as have adsorptive powers comparable with that of active finely divided aluminum oxide and another ply loaded with conductive carbon black and a sec-- ond layer of material loaded with conductive carbon black and contiguous with said other play and further characterized in that the said dielectric is free of any adsorbent material.
  • an active finely divided adsorbent material selected from the group consisting of aluminum oxide and such other active metallic oxides, hydrated metal oxides, metal hydroxides, metal carbonates and basic metal carbonates as have adsorptive powers comparable with that of active finely divided aluminum oxide and another ply loaded with conductive carbon black and a sec-- ond layer of material

Abstract

A conductive or semiconductive fibrous sheet material used as an electric screen in contact with the dielectric fluid of high voltage cables having a fluid impregnated dielectric is loaded both with conductive carbon and with at least one active, finely divided material selected from the group consisting of aluminium oxide and such other metallic oxides, hydrated metal oxides, metal hydroxides, metal carbonates and basic metal carbonates as have adsorptive powers comparable with that of active finely divided aluminum oxide. The dielectric is free of any adsorbent.

Description

ELECTRIC CABLES This is a division of U.S. Pat. application Ser. No. 20,670, filed Mar. 18, 1970 now abandoned.
This invention relates to conductive or semiconductive fibrous material in sheet form suitable for use as an electric screen in contact with the dielectric fluid of high-voltage cables and other electrical apparatus having a fluid impregnated dielectric.
The invention is especially concerned with the dielectric and conductor screens of oil-filled electric cables which may be of the pipe type or of the selfcontained type having one or more internal oil ducts. It has as its principal object the provision of a permeable material for this purpose that is capable of protecting the dielectric material against contamination and that is less liable to contaminate the dielectric and/or its impregnant than are permeable materials hitherto used.
The material in accordance with the invention is a conductive or semi-conductive fibrous material in the form of a flexible sheet loaded both with conductive carbon and with active finely divided material selected from the group consisting of aluminium oxide and such other metal oxides, hydrated metal oxides, metal hydroxides, metal carbonates and basic metal carbonates as have adsorptive powers comparable with that of active finely divided aluminium oxide. Of these materials aluminium oxide and titanium dioxide are preferred, in that order.
I prefer to use aluminium oxide or other active substances in the manner disclosed in U.K. Pat. No. 874,981 except that instead of incorporating these substances in a paper or other dielectric material suitable for use as a dielectric as claimed in that patnet, they are incorporated in fibrous materials suitable for use as a conducting or semi-conducting screen.
The invention includes cables, especially cables having an impregnated dielectric such as oil-filled cables, in which the fibrous materials are used either as a conductor screen or as a dielectric screen or both. Normally, at least two layers of the loaded fibrous material will be used in each screen, the layers breaking joint.
The invention also includes multi-ply fibrous sheet materials in which at least one but not all plies is loaded with the active material and conductive carbon.
The invention also includes multi-ply fibrous sheet materials in which at least one but not all plies is loaded with conductive carbon but not with active alumina or other active material and at least one of the remaining plies is loaded with such active material but not with conductive carbon. in forming a conductor screen from such sheet material, such sheet material may be applied over an underlying layer of material loaded with conductive carbon, with the ply or plies that is or are loaded with active alumina or other active material on the outside (that is adjacent to the dielectric) but to avoid exposure of the conductive carbon loaded paper to the oil in the butt spaces between the turns of the multi-ply sheet material, it is preferable to apply a multi-ply sheet material over an underlying layer of material loaded with both active alumina and conductive carbon. A similar but inverted construction may be used in forming a dielectric screen.
The quantities and type of conductive carbon used will be substantially the same as in conventional carbon loaded paper used for this purpose.
The particle size of the alumina or otheractive substance must be such that it does notinterfere with the paper making process; colloidal particles are preferably used. Although less than 2 percent of the active substance based on the weight of the paper can be used, since its effectiveness is a function of the quantity used larger quantities, e.g. 8-10 percent, are preferred. The active substance must be substantially free from ionic impurities that would deleteriously affect the electrical properties of the dielectric and before incorporation in the paper it is preferably subjected to the same tests as is paper for use as the dielectric of electric cables and other electrical apparatus, i.e., tests for conductivity and acidity/alkinility of the aqueous extract. Also, as stated in the above mentioned British Patent Specification, the substance must not be overheated during the activation process to the extent that fusion of the particles occurs, since this would materially reduce the adsorptive power and by virtue of the increased crystalinity and abrasiveness interfer with the felting of the paper fibres. The carbon and the alumina, or other active substance, can each be incorporated in the fibrous material either during manufacture, i.e., by addition to the pulp in the case of paper either at the hydro pulper or the beater, or after manufacture by impregnation of the fibrous material with a suspension of the material or materials.
Although the invention is mainly concerned with sheet material based on paper of the quality normally used as the dielectric in high voltage cables, other fibrous sheet materials, both natural and synthetic, that are compatible with the dielectric materials can alternatively be used.
The sheet material in accordance with the invention is intended primarily to act as a barrier inhibiting the migration into the dielectric of ionic impurities carried by the fluid impregnant, which impurities may for example be derived from metals with which the fluid comes into contact within the electrical apparatus or in ancillary apparatus through which the fluid is circulated, for example the metal of cable conductors, enclosing pipes or cable sheaths, binding tape applied to the dielectric, external heat exchangers, and circulating pumps. The alumina or other active substance may also inhibit migration of carbon or other semi-conducting particles derived from carbon black from the fibrous material into the adjacent dielectric or the impregnant therefor. In the accompanying drawings FIGS. 1 & 2 show two forms of fibrous sheet material in accordance with the invention; and FIG. 3 shows in cross-section a cable having a conductor screen and a dielectric screen of the material in accordance with the invention.
The presence of the alumina or other active substance will greatly increase the adsorptive power for contaminating ions of the paper or other fibrous material by virtue of the much higher adsorptive index of the alumina or other active substance as compared with the activated carbon. The presence of the alumina or other active substance will however not substantially affect the permeability of the loaded fibrous material and hence will not obstruct the passage of moisture from the dielectric during the drying of the dielectric prior to impregnation.
The sheet materials in accordance with the invention have the advantage over carbon loaded papers hitherto used that when used instead of such materials as the conductor and/or the dielectric screen of a high voltage cable with an oil impregnated dielectric they reduce the rate at which the power factor of the cable increases over a long period of service.
They have the advantage over screens of solid metal foils (usually aluminium the alloy sold under the trademark Aluman, copper or bronze) and of metal foil laminated with fibrous material that they are permeable and that in comparison with the latter type of material the risk of contamination of the dielectric by the adhesive used to bond the metal foil to the fibrous material is avoided.
What I claim as my invention is:
1. An electric cable, comprising a. at least one metallic conductor,
b. a fluid impregnated dielectric surrounding said conductor and bounded at each of its inner and outer circumferential surfaces by an electric screen in contact with said fluid and formed from a fibrous material in the form of a flexible sheet loaded with conductive carbon black and c. an external fluid-tight sheath, said cable being characterized in that the said fibrous material of said electric screens comprises distinct plies loaded respectively with said conductive carbon black and with an active finely divided adsorbent material selected from the group consisting of aluminum oxide and such other active metallic oxides, hy-
'drsted metal oxides, metal hydroxides, metal car bonates and basic metal carbonates as have adsorptive powers comparable with that of active finely divided aluminum oxide and that the said dielectric is free of any adsorbent material.
2. An electric cable, comprising a. at least one metallic conductor,
b. a fluid impregnated dielectric surrounding said conductor and bounded at each of its inner and outer circumferential surfaces by an electric screen in contact with said fluid and formed from a fibrous material in the form of a flexible sheet loaded with conductive carbon black and c. an external fluid-tight sheath, the said cable being characterized in that the said electric screens each comprise a first layer of a multi-ply fibrous sheet material comprising one ply contiguous with the dielectric and loaded with an active finely divided adsorbent material selected from the group consisting of aluminum oxide and such other active metallic oxides, hydrated metal oxides, metal hydroxides, metal carbonates and basic metal carbonates as have adsorptive powers comparable with that of active finely divided aluminum oxide and another ply loaded with conductive carbon black and a sec-- ond layer of material loaded with conductive carbon black and contiguous with said other play and further characterized in that the said dielectric is free of any adsorbent material.
3. A cable as claimed in claim 2 in which said second layer is also loaded with an active finely divided material selected from the group consisting of aluminium oxide and such other metallic oxides, metal hydroxides, metal carbonates and basic metal carbonates as have adsorptive powers comparable with that of active finely divided aluminium oxide.

Claims (2)

  1. 2. An electric cable, comprising a. at least one metallic conductor, b. a fluid impregnated dielectric surrounding said conductor and bounded at each of its inner and outer circumferential surfaces by an electric screen in contact with said fluid and formed from a fibrous material in the form of a flexible sheet loaded with conductive carbon black and c. an external fluid-tight sheath, the said cable being characterized in that the said electric screens each comprise a first layer of a multi-ply fibrous sheet material comprising one ply contiguous with the dielectric and loaded with an active finely divided adsorbent material selected from the group consisting of aluminum oxide and such other active metallic oxides, hydrated metal oxides, metal hydroxides, metal carbonates and basic metal carbonates as have adsorptive powers comparable with that of active finely divided aluminum oxide and another ply loaded with conductive carbon black and a second layer of material loaded with conductive carbon black and contiguous with said other play and further characterized in that the said dielectric is free of any adsorbent material.
  2. 3. A cable as claimed in claim 2 in which said second layer is also loaded with an active finely divided material selected from the group consisting of aluminium oxide and such other metallic oxides, metal hydroxides, metal carbonates and basic metal carbonates as have adsorptive powers comparable with that of active finely divided aluminium oxide.
US00202553A 1971-11-26 1971-11-26 Electric cables Expired - Lifetime US3780206A (en)

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Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3988526A (en) * 1973-04-05 1976-10-26 Felten & Guilleaume Kabelwerke Ag Internally cooled high-voltage high-energy cable
US4039740A (en) * 1974-06-19 1977-08-02 The Furukawa Electric Co., Ltd. Cryogenic power cable
US4091139A (en) * 1975-09-17 1978-05-23 Westinghouse Electric Corp. Semiconductor binding tape and an electrical member wrapped therewith
US4095204A (en) * 1975-01-27 1978-06-13 Mitsubishi Denki Kabushiki Kaisha Transformer having forced oil cooling system
US4176238A (en) * 1976-01-08 1979-11-27 Gosudarstvenny Nauchno-Issledovatelsky Energetichesky Institut Imeni G.M. Krzhizhanovskogo (ENIN) Cooled multiphase ac cable
US4184042A (en) * 1977-05-03 1980-01-15 Gosudarstvenny Nauchno-Issledovatelsky Energetichesky Institut Imeni G.M. Krzhizhanovskogo Multisection superconducting cable for carrying alternating current
US4308312A (en) * 1979-07-24 1981-12-29 General Electric Company Dielectric films with increased voltage endurance
US4487996A (en) * 1982-12-02 1984-12-11 Electric Power Research Institute, Inc. Shielded electrical cable
US4536610A (en) * 1983-06-21 1985-08-20 Societa' Cavi Pirelli, S.P.A. Oil-filled, multi-core cable with at least one conductor differing from others
EP0971371A1 (en) * 1998-07-06 2000-01-12 PIRELLI CAVI E SISTEMI S.p.A. High voltage direct current electrical cable with mass-impregnated insulation
US6246006B1 (en) 1998-05-01 2001-06-12 Commscope Properties, Llc Shielded cable and method of making same
US6245426B1 (en) * 1996-07-04 2001-06-12 Abb Research Ltd. Electric device with a porous conductor insulation impregnated with a dielectric fluid exhibiting a rheologic transition point
US6384337B1 (en) 2000-06-23 2002-05-07 Commscope Properties, Llc Shielded coaxial cable and method of making same
US6395975B1 (en) 1998-07-06 2002-05-28 Pirelli Cavi E Sistemi S.P.A. High voltage direct current electrical cable with mass-impregnated insulation
US20090071400A1 (en) * 2007-09-17 2009-03-19 Svein Soyland Flexible Hose And A Paint Application Apparatus And System With Same

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2112322A (en) * 1935-01-18 1938-03-29 Detroit Edison Co Cable
US2266810A (en) * 1939-03-13 1941-12-23 Ruben Samuel Dielectric for electrostatic condensers
CA463893A (en) * 1950-03-21 L. Beede Harry Electric cable
US2594872A (en) * 1945-06-26 1952-04-29 Gen Electric Stabilization of halogenated hydrocarbons
GB744481A (en) * 1952-01-31 1956-02-08 Pirelli Improvements in or relating to high-tension electric cables
US2967902A (en) * 1956-03-16 1961-01-10 Pirelli Paper screening tapes for high tension electric cables
GB874981A (en) * 1958-01-17 1961-08-16 Tervakoski Osakeyhtioe Improvements in and relating to impregnated paper
GB896066A (en) * 1959-08-21 1962-05-09 Anaconda Wire & Cable Co Improvements in insulating oils
US3090705A (en) * 1958-01-17 1963-05-21 Tervakoski Osakeyhtio Impregnated paper to serve as a dielectric, especially in condensers to improve their critical performance

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA463893A (en) * 1950-03-21 L. Beede Harry Electric cable
US2112322A (en) * 1935-01-18 1938-03-29 Detroit Edison Co Cable
US2266810A (en) * 1939-03-13 1941-12-23 Ruben Samuel Dielectric for electrostatic condensers
US2594872A (en) * 1945-06-26 1952-04-29 Gen Electric Stabilization of halogenated hydrocarbons
GB744481A (en) * 1952-01-31 1956-02-08 Pirelli Improvements in or relating to high-tension electric cables
US2967902A (en) * 1956-03-16 1961-01-10 Pirelli Paper screening tapes for high tension electric cables
GB874981A (en) * 1958-01-17 1961-08-16 Tervakoski Osakeyhtioe Improvements in and relating to impregnated paper
US3090705A (en) * 1958-01-17 1963-05-21 Tervakoski Osakeyhtio Impregnated paper to serve as a dielectric, especially in condensers to improve their critical performance
GB896066A (en) * 1959-08-21 1962-05-09 Anaconda Wire & Cable Co Improvements in insulating oils

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3988526A (en) * 1973-04-05 1976-10-26 Felten & Guilleaume Kabelwerke Ag Internally cooled high-voltage high-energy cable
US4039740A (en) * 1974-06-19 1977-08-02 The Furukawa Electric Co., Ltd. Cryogenic power cable
US4095204A (en) * 1975-01-27 1978-06-13 Mitsubishi Denki Kabushiki Kaisha Transformer having forced oil cooling system
US4091139A (en) * 1975-09-17 1978-05-23 Westinghouse Electric Corp. Semiconductor binding tape and an electrical member wrapped therewith
US4176238A (en) * 1976-01-08 1979-11-27 Gosudarstvenny Nauchno-Issledovatelsky Energetichesky Institut Imeni G.M. Krzhizhanovskogo (ENIN) Cooled multiphase ac cable
US4184042A (en) * 1977-05-03 1980-01-15 Gosudarstvenny Nauchno-Issledovatelsky Energetichesky Institut Imeni G.M. Krzhizhanovskogo Multisection superconducting cable for carrying alternating current
US4308312A (en) * 1979-07-24 1981-12-29 General Electric Company Dielectric films with increased voltage endurance
US4487996A (en) * 1982-12-02 1984-12-11 Electric Power Research Institute, Inc. Shielded electrical cable
US4536610A (en) * 1983-06-21 1985-08-20 Societa' Cavi Pirelli, S.P.A. Oil-filled, multi-core cable with at least one conductor differing from others
US6245426B1 (en) * 1996-07-04 2001-06-12 Abb Research Ltd. Electric device with a porous conductor insulation impregnated with a dielectric fluid exhibiting a rheologic transition point
US6246006B1 (en) 1998-05-01 2001-06-12 Commscope Properties, Llc Shielded cable and method of making same
EP0971371A1 (en) * 1998-07-06 2000-01-12 PIRELLI CAVI E SISTEMI S.p.A. High voltage direct current electrical cable with mass-impregnated insulation
US6395975B1 (en) 1998-07-06 2002-05-28 Pirelli Cavi E Sistemi S.P.A. High voltage direct current electrical cable with mass-impregnated insulation
US6384337B1 (en) 2000-06-23 2002-05-07 Commscope Properties, Llc Shielded coaxial cable and method of making same
US20090071400A1 (en) * 2007-09-17 2009-03-19 Svein Soyland Flexible Hose And A Paint Application Apparatus And System With Same
US8272407B2 (en) * 2007-09-17 2012-09-25 Abb As Flexible hose and a paint application apparatus and system with same

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