US3594489A - Extra high voltage cables - Google Patents

Extra high voltage cables Download PDF

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Publication number
US3594489A
US3594489A US765447A US3594489DA US3594489A US 3594489 A US3594489 A US 3594489A US 765447 A US765447 A US 765447A US 3594489D A US3594489D A US 3594489DA US 3594489 A US3594489 A US 3594489A
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Prior art keywords
paper
dielectric
layers
embossing
insulation
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Expired - Lifetime
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US765447A
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English (en)
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Carlos Katz
George S Eager Jr
George Bahder
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General Cable Corp
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General Cable Corp
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    • 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
    • H01B13/06—Insulating conductors or cables
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/002—Inhomogeneous material in general

Definitions

  • this invention provides insulation consisting of synthetic plastic material [52] .8. Cl 174/25, with paper bonded to both sides to form a laminated trip In l74/l 10 PM, 17 120 PP place of the porous paper previously used, this invention uses [51 1 Int. Cl .1 01b 7/02 very thin paper such as capacitor tissue; space for the ther- M 0 Search 174/25, 24, ma] expansion of the synthetic and passages for the removal of 120, 120.1 1, -1, 1 1 1 l0 moisture and the introduction of oil are obtained by embossing the strip.
  • the embossing is preferably embossed with UNITE STATES PATENTS a random pattern, or plain unembossed strips are wrapped al- 3,078,333 2/1963 Kang 174/25 X temately between embossed strips.
  • the invention includes the 3,105,872 10/1963 Thompson eta1.. 174/25 X novel strip, cable made with the strip and the method of mak- 3,194,872 7/1965 Garner 174/25 ing the strip.
  • the Kang U.S. Pat. No. 3,078,333 proposes the use of a dielectric comprising a single plastic strip bonded to a single paper strip.
  • the paper provides a partial mechanical reinforcement to the plastic, it does not provide protection against corona discharges in the butt spaces or avoid the plastic swelling and/or sinking in the butt spaces.
  • Other insufficiencies of such a cable involve difficulties in saturation and changes in diameter with changes in temperature.
  • plastics are incompatible with suitable liquid dielectrics; swelling, softening, elongating or tearing under load, etc. when in contact with these liquids especially at elevated temperatures.
  • Garner U.S. Pat. No. 3,194,872 A construction which overcomes almost all of the shortcomings of other high-voltage cable constructions is disclosed in Garner U.S. Pat. No. 3,194,872.
  • This Garner patent has the cable manufactured with a composite of paper-synthetic filmpaper.
  • the present invention is an improvement on the construction of this Garner patent.
  • One of the improvements effected by this invention is a reduction in the power factor for extra high voltage cables.
  • the total thickness of the strip or tape must be limited to about 3 to mils.
  • One problem has been to obtain thin paper having an acceptable low air resistance which is necessary to obtain an efficient flow of the moisture out of the paper and the flow of liquid dielectric into the voids of the paper-plastic insulation.
  • This invention makes possible the use of low loss, impermeable, extremely thin papers in the insulation of cables.
  • Another improvement relates to providing enough space for the expansion of the synthetic used in the insulating wall, so that the overall dimensions ofthe cable are not altered and the physical integrity of the cable is not disrupted when subjected to heating, allowing the use of the same electrical shielding and mechanical protecting materials and the use of the same potheads at cable terminations than in conventional paper-insulated cables.
  • Another improvement relates to the use of synthetic films having good electrical properties but relatively poor mechanical and thermal characteristics.
  • Another improvement relates to the bonding of the paper to the plastic. In prior bonding operation, part of the plastic has migrated among the cellulose fibers of the paper forming barriers for moisture removal and liquid dielectric penetration.
  • This invention provides a composite insulation of good dielectric properties and relatively good mechanical and thermal properties.
  • a synthetic film is bonded between special thin paper which occupies a total not more than about 50 percent of the total thickness of the strip or tape.
  • the composite strip is embossed in a pattern to provide space for the expansion of the synthetic and for passage of liquid dielectric.
  • the expansion of the synthetic is produced by in service increases in temperature of the cable,
  • One feature of the invention is an irradiation of the composite to improve the thermal stability of the dielectric.
  • Cable made in accordance with this invention can be wrapped with the composite strip or tape having only every alternate layer embossed and the other plain. This prevents lockout of the embossed patterns when the cable is bent and does not necessitate the use of random patterns of embossing to avoid lockout.
  • the invention includes methods of making the strip or tape and the cable.
  • the invention results in an improved cable having lower power factors, low dielectric constant, good mechanical and thermal properties, high resistance to corona discharges, and at the same time assures an effective moisture removal and liquid saturation.
  • FIG. 2 is a view similar to FIG. I but showing a strip or tape embossed with a regular pattern
  • FIG. 3 is an enlarged sectional view showing a strip or tape with a regular embossing pattern wrapped between unembossed strips to prevent lockup of the embossing when the cable is bent;
  • FIG. 4 is a fragmentary view partly broken away and in section showing a cable made with the strip or tape of this invention
  • FIG. 5 is an enlarged fragmentary view through several layers ofthe insulation of the tape shown in FIG. 4;
  • FIG. 6 is a diagrammatic view illustrating the method of making the strip or tape shown in the other views.
  • the tape insulation shown in FIG. 1 consists of a strip or tape 8 of composite material, bonded, embossed and in some cases irradiated in accordance with this invention.
  • the composite consists of a layer of suitable synthetic film I0 of the high polymer type such as polypropylene or polyethylene respectively, bonded between two very thin sheets 12, each 0.00075 inch to 0.0015 inch thick, of high purity, low loss 1 paper of the type used in the manufacture of capacitors and known generally as capacitor tissue.
  • the depth of embossing I4 is such that enough space is provided for the expansion of the synthetic during the drying impregnation part of the manufacturing operation and during continuous in service operation, at the same time the unrestricted longitudinal flow of moisture and oil is not restricted to a relatively slow movement. At the same time it is not too deep to affect adversely the best dielectric performance ofthe composite.
  • FIG. 1 shows astrip of bonded composite embossed with a random pattern. Random embossing patterns are advantageous to avoid locking the overlying tapesin cables where all the insulating tapes are embossed. Locking of the tapes could cause electrical and/or mechanical weakness of thecable when it is bcnt.
  • FIG. Z- shows a strip 8' of bonded composite embossed with a uniformlyrep'eated embossing pattern 16.
  • the parts of the strip 8' are indicated by the same reference characters as in FIG. 1 with a prime appended.
  • 4 A variation of the extra high voltage cable described is shown in FIG. 3. It has composite tapes 8A embossed with a random or uniformly repeated embossing pattern I8. In this variation only alternate layers of the dielectric need to be embossed, while the remaining layers 8B are of the same dielectric but not embossed. Paper and plastic laminations are indicated by the same reference characters as in FIG. I with an A or B appended..Except'for the correlation of embossed and unembossed layers, the cable made according to FIG, 3 can be the same as that which will be described in connection with FIG. 4.
  • a second variation of this FIG. 3cable can be made with an embossed composite having capacitor tissue only at one side and synthetic film at the other.
  • the conductor 20 of this particular cable is segmental, having two of its opposite segmentsinsulated with a high-purity, mechanically strong, dielectric tape'material 24.
  • the conductor of this cable is wrapped in an electrostatic shield 26 formed by conducting tapes over which the mass of the embossed composite tape insulation 8 is carefully precisely applied open butt.
  • the direction of tape application has been changed at regular intervals (every 10 tapes) to obtain an electrically efficient and mechanically strong cable. Two lay directions of the applied insulating tapes 8 are shown.
  • the capacitor tissue 12, 12', 12A or 128 has a power factor of about 0.07 percent at 80 C a dielectric constant of about l.7 at 80 C.; and an oil-impregnated dielectric strength of about 2,800 v./mil. These values are given by way of illustration and are more favorable than thoseof the highest purity papers conventionally used in cable manufacture. In addition, because of its relatively high mechanical strength, the capacitor tissue allows the use of synthetic film materials having relatively poor mechanical strength but good-electrical characteristics.
  • capacitor tissue is used herein to'designate a paper made from short fibered stock to obtain a pinhole free, .very high impermeable paper, having a thickness from 0.0002 inch to 0.00l 5 inch and a density in the range from about 0.7 to 1.2 g./cc.
  • the tissue has a low power factor and low dielectric constant.
  • the capacitor tissue has a dry percent power factor of about 0.07 at 80 C.,'and the power factor of the oiled composite of this invention is less than 0.0015 and preferably about 0.0005 or less at 80 C. with an overall dielectric constant of less than 3.0 at 80 C.
  • the preferred capacitor tissue has a maximum of conducting'particles per square foot less than L4; and has a pH of about 6.3
  • the capacitor tissue provides the composite with the necessary mechanical strength (reinforcement) and protects the synthetic, when it softens and expands, from sinking in the butt spaces of the adjacent layers of dielectric. Because the capacitor tissue is strong and permanently laminated the synthetic when a raise in temperature occurs, the synthetic cannot elongate significantly (if the paper would be weak the longitudinal expansion of the synthetic would break the paper). The space left between the tapes by the embossing is more than enough to absorb the increase in synthetic volume.
  • capacitor tissue protects the synthetic and provides the composite with the necessary lation shield 30, consisting of conducting tapes, is applied over tion the removal of moisture and liquid impregnation are improved and a better high-voltage stress distribution is obtained.
  • Another variation of this cable can be made by using in the cable manufacture composite tapes having various depths of embossing. These depths will depend on the thickness of the tape and'the position of the same with respect to the conductor. with this construction, the greater the thickness of the tape and the further away the individual layer of composite tape is from the conductor the greater is the depth of embossing.
  • FIG. 5 illustrates, in detail, a longitudinal cross section'of several embossed insulating tapes 8 ofthe cable shown inFlG. 4.
  • embossed composite insulated cables would change as isthe case with synthetic insulated cables, it would have been'necessary to search for new materials to be used in the electrostatic shielding, moisture and mechanical protection of the cable. Only materials having similar thermal characteristics to the synthetics used in these cables and having unusual elastomeric and mechanical properties could be used.
  • embossed composite dielectric popular and well known I materials as, for example, copper tapes, foil backed mylar, metallic skid wires, etc. can be used. It also would have been necessary to invent and design a kind of pothead which changes its radial dimensions with changes in temperature.
  • Theembossing of the composite provides space for the thermal expansion of the plastic and permits a fast moisture removal and oil impregnation and makes negligible the possibility of void formation.
  • a dielectric composite material consisting of a continuous sheet of polypropylene bonded between two thin sheets of very high purity, low-loss capacitor tissue.
  • the bonded composite is permanently embossed with a random or uniformly repeated pattern which may add up to about 2 mils to the thickness of a single strip of composite 5 mils thick.
  • Synthetic materials such as polyphenylene oxide, polysiloxane fluonnated ethylene propylene polycarbonate, polyimide, olysulfone. polytetrafluoroethylene, poly-4-methylpentene. polystyrene. and their irradiated variations and all others having good electrical properties, as for example, low dissipation factor. low dielectric constant, good dielectric strength and in addition. relatively good thennal properties are appropriate for use in this composite.
  • the extra high voltage cable of this invention is manufactured by wrapping the stranded coated or uncoatcd copper or aluminum conductor with an electrostatic shield formed by conducting tapes.
  • the dielectric tape application is performed with the help of multiple-head taping machines, changing the direction of tape application at regular intervals (for example every l0 tapes). This operation is performed in a closed room, free of contaminants, maintained at about 25 to 30 C. and a relative humidity not in excess of percent.
  • the cable is picked up on a reel and subsequently dried under vacuum to a moisture content of less than 0.1 percent and later impregnated with a liquid dielectric which also occupies all the spaces among the solid dielectric. Shielding, moisture and mechanical protecting tapes are applied over the composite in a subsequent operation.
  • the manufacture of the permanently embossed composite dielectric can be accomplished in one continuous operation as illustrated in a simplified way in FIG. 6, where right after the synthetic film 10 has been extruded it is passed between feed rolls 40 to a bonding station 44 where the film 10 is passed over or between a series of heated rollers 46 to which the very thin paper 12 is also conveyed. Previous to the meeting of the paper 12 and the synthetic film 10, the paper 12 is passed over other steel rollers 50 heated to about 140 C. The heating operation of the paper serves the double purpose of removing moisture and preheating the paper to obtain a better bond between the paper 12 and the synthetic film 10.
  • the conditions of heat and pressure, to obtain the intimate and permanent bond depend on the nature of the synthetic film and may be, for example, in the order of 130 to 140 C. for polypropylene and for polyethylene.
  • the composite is passed between embossing rollers 5455, one of which is of a hard rubberlike material and the other is of steel having the embossing pattern engraved on its surface.
  • the depth and quality of the embossing will depend on the temperature of the composite at the time of embossing and on the speed with which the composite moves between the embossing rollers. For example, in case of a composite made with a 0.0025 inch-thick film of polypropylene between two sheets of capacitor tissue, each 0.001, inch, a speed of about 12 feet per minute and a temperature of about 130 C. were used to obtain a suitable embossed composite having a total overall thickness of about 0.0055 inch. These figures are given by way of illustration. The patterns used during embossing may be of any practical and feasible configuration.
  • the composite After the embossing operation is finished the composite is cooled to an intermediate temperature between the embossing temperature and room temperature, for example 60 C., at the same time that it is moved to a low relative humidity environment (to avoid, as much as possible, the pickup of moisture by the paper).
  • the cooled composite is slit by knives 62 and taken off into individual rolls 64 having width of three-fourths, seven-eighths or 1 inch, in a suitable fashion, up to, for example, inch in diameter.
  • the rolls are placed in moistureproof containers and shipped to the side of the cable-taping machines where they will be wrapped over an electrical conductor.
  • the described, continuous process is the most economical for the production of this extra high voltage dielectric wrapping, however, this process can be separated into individual operationswithout any consequence to the good performance of the dielectric.
  • the embossing can also be performed by a more complicatedprocedurein which more than one embossing roll is used.
  • this operation is performed after thecomposite has been enibossed. 1n the case of a composite made with polyethylene an irradiation dose of 7 to 17 megarads, applied under vacuum is most effective.
  • the irradiation operation can also be performed effectively in a neutral gas environment.
  • the bond between the paper and the synthetic film can also be achieved by using any adhesive which will not adversely affect the good electrical and mechanical properties of the corriposite.
  • adhesives of the polyisobutylene type are suitable.
  • Oil impregnated, embossed composite dielectric 5 mils thick (60% polypro- Pylene, 40% paper) O l impregnated, embossed, irradiated composite dielectric, 5 mils thick (70% Polyethylene, 30% paper) 078 0 limprcgnated high purity aper used in hi h voltage cables, 5 mils t ick 154 ili i ir lain it di 1 tri mregnac,p compos e eec c 5 thick (60% polypropylene, 40%
  • Corona Resistance Test Test performed by placing samples, 13 10.5 mils thick, under corona discharges. Keeping a clearance of 5 mils between the sample and one of the electrodes and maintaining a stress of 15 kv. on the samples.
  • Oil Flow Test Tests showed that under similar test conditions the forced flow of oil along the surface of permanently embossed composite tape is about 10 times faster than on the surface of porous low density, highpurity paper of the type used in high.
  • the electrical cable described in claim I characterized by v the composite dielectric layers having capacitor tissue bonded to the plastic whereby the laminate including the paper is highly impermeable to liquid dielectric, the embossing being between successive convolutions bridged by the paper of underlying and overlying layers to prevent the plastic from flowing into the butt spaces when the cable is heated. l
  • each layer of embossed dielectric strip having a uniform pattern of embossing and being in alternating relation with a layer of plain unembossed dielectric strip to prevent locking of embossedsurfaces of strips with confronting surfaces of other strips'when the'cable is bent.
  • the electrical cable described in claim I characterized by the plastic film being about 2 to 10 mils in thickness and the paper being sheets of capacitor tissue bonded to both surfaces of the plastic.
  • the electrical cable described in claim 1 characterized by some of the layers of dielectric'material being of greater radial thickness than others, and the layers of greaterthickness have their paper sheets embossed to a greater depth to provide more space for the expansion of the plastic film, and for moistureremoval and liquid impregnation.
  • the electrical cable described in claim 1 characterized by insulation including tapes comprising plastic film bonded between sheets of paper and including other tapes of conventional high purity, low-loss paper insulation, the conventional paper tapes being limited to not more than about 15 percent of the total insulation cross section.
  • the electrical cable described in claim 1 characterized by the insulation having inner and outermost layers of tape, at least one ofwhich is a paper tape.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Insulating Bodies (AREA)
  • Organic Insulating Materials (AREA)
  • Paper (AREA)
  • Laminated Bodies (AREA)
  • Lining Or Joining Of Plastics Or The Like (AREA)
US765447A 1968-10-07 1968-10-07 Extra high voltage cables Expired - Lifetime US3594489A (en)

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US76544768A 1968-10-07 1968-10-07

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US (1) US3594489A (xx)
JP (1) JPS4844791B1 (xx)
CA (1) CA922394A (xx)
CH (1) CH520389A (xx)
DE (1) DE1950404A1 (xx)
ES (1) ES372275A1 (xx)
FR (1) FR2020036A1 (xx)
GB (1) GB1287948A (xx)
SE (1) SE374448B (xx)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3775549A (en) * 1971-06-23 1973-11-27 Sumitomo Electric Industries Electrically insulating polyproplyene laminate paper and oil-impregnated electric power cable using said laminate paper
US3928705A (en) * 1971-04-15 1975-12-23 Celanese Corp Dielectric insulation employing open-celled microporous film
US4095205A (en) * 1977-07-28 1978-06-13 Westinghouse Electric Corp. Transformer with improved insulator
US4237334A (en) * 1977-08-06 1980-12-02 Showa Electric Wire & Cable Co., Ltd. Laminated insulating paper and oil-filled cable insulated thereby
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
US20100167582A1 (en) * 2008-12-30 2010-07-01 Schlumberger Technology Corporation Pothead connectors for submersible motor head and methods of assembly thereof
US20160155537A1 (en) * 2013-09-24 2016-06-02 Furukawa Electric Co., Ltd. Submarine cable and multilayer tape for impermeable layer of same

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1311867A (en) * 1969-10-22 1973-03-28 British Insulated Callenders Electric cables
JPS5396293A (en) * 1977-02-02 1978-08-23 Masami Takahara Selffcuring instrument utilizing bath tank
JPS5460980U (xx) * 1977-10-05 1979-04-27
DE4121547A1 (de) * 1991-06-28 1993-01-14 Daimler Benz Ag Mehrschichtisolierfolie

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3078333A (en) * 1963-02-19 High voltage power cable
GB925403A (en) * 1960-07-06 1963-05-08 Felten & Guilleaume Carlswerk An electrical high-tension cable whereof the wound dielectric is filled with a gaseous or liquid substance
US3105872A (en) * 1960-11-10 1963-10-01 Anaconda Wire & Cable Co Electric cable
CA690353A (en) * 1964-07-07 C. Brastow William Electric cable and insulation
US3194872A (en) * 1963-04-23 1965-07-13 Gen Cable Corp Paper and polyolefin power cable insulation
US3250850A (en) * 1961-02-17 1966-05-10 Moser Glaser & Co Ag Laminated insulating body
US3358071A (en) * 1967-05-29 1967-12-12 Anaconda Wire & Cable Co High voltage cables insulated with polysulfone tapes
US3429983A (en) * 1963-11-27 1969-02-25 Bayer Ag Insulated power cables

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3078333A (en) * 1963-02-19 High voltage power cable
CA690353A (en) * 1964-07-07 C. Brastow William Electric cable and insulation
GB925403A (en) * 1960-07-06 1963-05-08 Felten & Guilleaume Carlswerk An electrical high-tension cable whereof the wound dielectric is filled with a gaseous or liquid substance
US3105872A (en) * 1960-11-10 1963-10-01 Anaconda Wire & Cable Co Electric cable
US3250850A (en) * 1961-02-17 1966-05-10 Moser Glaser & Co Ag Laminated insulating body
US3194872A (en) * 1963-04-23 1965-07-13 Gen Cable Corp Paper and polyolefin power cable insulation
US3429983A (en) * 1963-11-27 1969-02-25 Bayer Ag Insulated power cables
US3358071A (en) * 1967-05-29 1967-12-12 Anaconda Wire & Cable Co High voltage cables insulated with polysulfone tapes

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3928705A (en) * 1971-04-15 1975-12-23 Celanese Corp Dielectric insulation employing open-celled microporous film
US3775549A (en) * 1971-06-23 1973-11-27 Sumitomo Electric Industries Electrically insulating polyproplyene laminate paper and oil-impregnated electric power cable using said laminate paper
US4095205A (en) * 1977-07-28 1978-06-13 Westinghouse Electric Corp. Transformer with improved insulator
US4237334A (en) * 1977-08-06 1980-12-02 Showa Electric Wire & Cable Co., Ltd. Laminated insulating paper and oil-filled cable insulated thereby
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
US20100167582A1 (en) * 2008-12-30 2010-07-01 Schlumberger Technology Corporation Pothead connectors for submersible motor head and methods of assembly thereof
WO2010077726A1 (en) * 2008-12-30 2010-07-08 Schlumberger Canada Limited Pothead connectors for submersible motor head and methods of assembly thereof
US7942696B2 (en) 2008-12-30 2011-05-17 Schlumberger Technology Corporation Pothead connectors for submersible motor head and methods of assembly thereof
GB2478484A (en) * 2008-12-30 2011-09-07 Schlumberger Holdings Pothead connectors for submersible motor head and methods of assembly thereof
GB2478484B (en) * 2008-12-30 2013-01-02 Schlumberger Holdings Pothead connectors for submersible motor head and methods of assembly thereof
US20160155537A1 (en) * 2013-09-24 2016-06-02 Furukawa Electric Co., Ltd. Submarine cable and multilayer tape for impermeable layer of same
US10056171B2 (en) * 2013-09-24 2018-08-21 Furukawa Electric Co., Ltd. Submarine cable and multilayer tape for impermeable layer of same

Also Published As

Publication number Publication date
GB1287948A (xx) 1972-09-06
ES372275A1 (es) 1971-09-16
JPS4844791B1 (xx) 1973-12-26
FR2020036A1 (xx) 1970-07-10
CH520389A (de) 1972-03-15
SE374448B (xx) 1975-03-03
DE1950404A1 (de) 1970-06-04
CA922394A (en) 1973-03-06

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