US3541228A - Medium voltage cables - Google Patents

Medium voltage cables Download PDF

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US3541228A
US3541228A US730657A US3541228DA US3541228A US 3541228 A US3541228 A US 3541228A US 730657 A US730657 A US 730657A US 3541228D A US3541228D A US 3541228DA US 3541228 A US3541228 A US 3541228A
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semiconductive
layer
insulating layer
conductor
medium voltage
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US730657A
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Luigi Lombardi
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Pirelli and C SpA
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Pirelli SpA
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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
    • H01B9/02—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
    • 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
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • 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
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
    • H01B3/441—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from alkenes
    • 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
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
    • H01B3/443—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from vinylhalogenides or other halogenoethylenic compounds

Definitions

  • These cables are often designed with an insulating layer disposed or sandwiched between two semiconductive layers in order to provide an equipotential surface to make the electric field of the insulating material uniform.
  • the semiconductive layer forming the outer covering can be placed either by extruding the semiconductive composition on the conductor which is coated with at least the insulating layer, or by helically winding a tape of semiconductive composition on the same unit.
  • the semiconductive composition is normally a tape of fabric impregnated with conductive carbon particles and an adhesive agent.
  • This invention provides medium voltage cables in which a conductor is insulated with a layer of a cured polyolefin copolymer insulating material.
  • the insulating layer is in a contiguous relationship with at least one semiconductive layer which is derived from a semiconductive composition comprising conductive carbon particles dispersed in chlorosulfonated polyethylene.
  • the insulating layer may be adjacent to the conductor and under the semiconductive layer, or it may be sandwiched between two semiconductive layers, one of which is adjacent the conductor.
  • contiguous is used herein to define the relationship between the layers. It means that there is close, intimate, nonadhesive contact between the surfaces of adjacent layers, and that there is substantially no air space between the surfaces.
  • the contact between the adjacent surfaces is a pressure contact similar to the contact achieved by the well known process of force fitting a metal shaft in a disc. Because of the adhesive free contact between layers they can be readily separated for splicing.
  • the semiconductive screen layer is placed over the insulating layer by winding a tape of the semiconductive composition obtained from a calendered sheet.
  • the insulating elastomeric materials utilized in the instant invention are cured compositions which are either saturated or unsaturated amorphous polyolefins. They are known insulating materials which are substantially linear, amorphous, high molecular weight copolymers obtained by copolymerization of ethylene with a-olefins containing one or more double bonds. If the olefin is a diene the double bonds may be conjugated or unconjugated. Copolymerization is effected by known techniques. The most common a-Olefill used in the preparation of these products is propylene.
  • Unsaturated products are obtained from conjugated or unconjugated dienes such as butadiene; isoprene; 2,3-dimethyl butadiene; 1,4-pentadiene; 2-methyl- 1,4-pentadiene; 1,5-hexadiene; 2-methyl-1,5-hexadiene; 1,4-hexadiene; 1,4-heptadiene; 1,5-heptadiene; 1,5-octadiene; dicyclopentadiene; Z-methylene 2,5 norbornene; 4,7,8,9-tetrahydromethylindene; and similar compounds.
  • conjugated or unconjugated dienes such as butadiene; isoprene; 2,3-dimethyl butadiene; 1,4-pentadiene; 2-methyl- 1,4-pentadiene; 1,5-hexadiene; 2-methyl-1,5-hexadiene; 1,4-hexadiene; 1,4-heptadiene; 1,5-
  • the insulating compositions are compounded by previously known methods with the appropriate curing or cross-linking agents, accelerators, plasticizers, antioxidants, reinforcing fillers and the like.
  • the composition may be extruded onto the base conductor or onto the conductor already coated with a semiconductive layer. They are then cured as described in more detail below.
  • the chlorosulfonated polyethylenes used in the invention are known products obtained by reacting polyethylone with chlorine and sulfur dioxide in accordance with known methods.
  • the polyethylene utilized has a number average molecular weight of the order of about 20,000.
  • the sulfur content of the product is normally from about 1.2% to 1.7%, and the chlorine content from about 26% to 40%.
  • the use of chlorosulfonated polyethylene as the carrier for the semiconductive compositions is a special feature of this invention.
  • the polymer also has excellent physical and mechanical characteristics. This makes it possible to obtain calendered sheets of minimum thickness to be utilized in the preparation of the winding tapes employed in the invention.
  • Such products are described, for example, at pages 387-390 of Polymers and Resins, by Brage Golding, Van Nos- I trand co; Inc'., New York, 1959.
  • the chlorosulfonated polyethylene is compounded with the appropriate ingredients, including the conductive particles, plasticizers such as basic lead phthalate and stabilizers such as polyethylene glycol.
  • plasticizers such as basic lead phthalate
  • stabilizers such as polyethylene glycol.
  • Useful compositions suggested by way of example may contain, for example, from about 40 to 70 parts carbon black, to 20 parts basic lead phthalate and 0.5 to 1 parts of polyethylene glycol per 100 parts of chlorosulfonated polyethylene.
  • the composition is calendered to produce a sheet having a thickness of from about 0.1 to 0.5 mm. from which the tapes can be prepared by cutting. I
  • the products of this invention may be prepared by any of a number of methods. All of them include a step in which a semiconductive layer in contact with an insulating layer is heated at a temperature of from about 100 C. to 200 C. for a sufficient period of time to elfect the contiguous relationship. During this period the semiconductive material may seal to itself at overlapping points.
  • the time of heating may vary within a very wide range, and the best time will be selected on the basis of the selected temperature, the dimensions of the cable, economy and ease of operation. Suitable heating periods will normally be within the range of from about 30 minutes to 3 hours.
  • a tape of the semiconductive composition is helically wound on a conductor previously coated with the cured polyolefin elastomer and the resulting product heated as described above. 7
  • the semiconductive composition may be coated directly on the conductor by extruding or by winding a tape, and the insulating material extruded onto the first layer.
  • This product may be coated with a second semiconductive layer, and the completedunit heated to effect simultaneous curing of the insulator and pressure fitting of the semiconductive layers to the conductor and to the insulating layer.
  • the semiconductive composition may be extruded directly on an insulated conductor at a temperature in the above defined range so as to obtain a semiconductive layer in contiguous relationship with the insulating layer in one operation.
  • One very convenient procedure for heating the unit comprising the conductor and the insulating and semiconductive layers is to cover it with a protective sheath in the form of a heat stable fabric such as cotton, rayon,
  • the protected unit is' then conducted through a heating zone such'as an oven to bring the temperature to the defined level.
  • the protective sheath is then removed.
  • a permanent protective sheath can also be used.
  • the unit could be coated with an elastomer such as polychloroprene, by any of the usual methods such as extrusion, and the protected unit then heated to cure the elastomer while at the same time bringing the semiconductive layer into contiguous relationship with the insulating layer.
  • an elastomer such as polychloroprene
  • 1 is a conductive cable
  • 2 is the insulating layer
  • 3 is the semiconductive layer.
  • a medium voltage electric cable comprising a conductor insulated with-an insulating layer of a cured amorphous olefine copolymer selected among the saturated and unsaturated amorphous olefine copolymers,'a surface of said insulating layer being in nonadhesive pressure contact with an adjacent surface of a semiconductive layer comprising conductive carbon particles dispersed in chlorosulfonated polyethylene, there being substantially no hollow spaces between said insulating layer and said semiconductive layer.
  • a cable as in claim -1 in which the insulating layer is sandwiched between two semiconductive layers.

Description

lei
A was 1 N VEN TOR. 0/ 6/ 10 *15440/ BY United States Patent 3,541,228 MEDIUM VOLTAGE CABLES Luigi Lombardi, Milan, Italy, assiguor to Pirelli Societa per Azioni, Milan, Italy, a corporation of Italy Filed May 20, 1968, Ser. No. 730,657 Claims priority, application Italy, May 23, 1967,
Int. Cl. H01b 7/00 US. Cl. 174-120 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Medium voltage cables, i.e., cables designed for the range of about 1,000 to 30,000 volts are known. Generally they comprise a conductor such as a copper wire or tube insulated with elastomeric materials, particularly cured polyolefin polymers, especially amorphous copolymers which may be saturated or unsaturated. The cables also include at least one semiconductive or screening layer.
These cables are often designed with an insulating layer disposed or sandwiched between two semiconductive layers in order to provide an equipotential surface to make the electric field of the insulating material uniform. The semiconductive layer forming the outer covering can be placed either by extruding the semiconductive composition on the conductor which is coated with at least the insulating layer, or by helically winding a tape of semiconductive composition on the same unit. In the latter case the semiconductive composition is normally a tape of fabric impregnated with conductive carbon particles and an adhesive agent.
Medium voltage cables prepared by either of these measures have proved deficient in that the semiconductive layer is merely superimposed on the insulating layer and that there are hollow spaces between the two layers which give rise to loss of efliciency due to ionization phenomena.
Attempts to avoid these difiiculties by the use of adhesives to adhere the one layer to the other have been unsatisfactory because of the difiiculties which arise in separating the layers when it is necessary to join or splice one cable to another.
It has therefore long been a problem in the art to provide a medium voltage cable characterized by a close, intimate, contiguous surface to surface contact between the insulating and semiconductive layers to thereby avoid losses due to ionization phenomena. The contact should be nonadhesive so that separate cables can be readily spliced without undue ditficulty.
THE INVENTION This invention provides medium voltage cables in which a conductor is insulated with a layer of a cured polyolefin copolymer insulating material. The insulating layer is in a contiguous relationship with at least one semiconductive layer which is derived from a semiconductive composition comprising conductive carbon particles dispersed in chlorosulfonated polyethylene. The insulating layer may be adjacent to the conductor and under the semiconductive layer, or it may be sandwiched between two semiconductive layers, one of which is adjacent the conductor.
The term contiguous is used herein to define the relationship between the layers. It means that there is close, intimate, nonadhesive contact between the surfaces of adjacent layers, and that there is substantially no air space between the surfaces. The contact between the adjacent surfaces is a pressure contact similar to the contact achieved by the well known process of force fitting a metal shaft in a disc. Because of the adhesive free contact between layers they can be readily separated for splicing.
It has been discovered that a contiguous relationship can be achieved between adjacent layers of cured, amorphous, saturated or unsaturated, polyolefin elastomerS and semiconductive compositions comprising conductive carbon particles dispersed in a chlorosulfonated poly ethylene polymer. This relationship is achieved by a heat treatment either subsequent to the placing of the layers in adjacent contact or while the layers are being placed in this relationship.
In one embodiment of the invention, which is preferred because for economy and efficiency, the semiconductive screen layer is placed over the insulating layer by winding a tape of the semiconductive composition obtained from a calendered sheet.
The insulating elastomeric materials utilized in the instant invention are cured compositions which are either saturated or unsaturated amorphous polyolefins. They are known insulating materials which are substantially linear, amorphous, high molecular weight copolymers obtained by copolymerization of ethylene with a-olefins containing one or more double bonds. If the olefin is a diene the double bonds may be conjugated or unconjugated. Copolymerization is effected by known techniques. The most common a-Olefill used in the preparation of these products is propylene. Unsaturated products are obtained from conjugated or unconjugated dienes such as butadiene; isoprene; 2,3-dimethyl butadiene; 1,4-pentadiene; 2-methyl- 1,4-pentadiene; 1,5-hexadiene; 2-methyl-1,5-hexadiene; 1,4-hexadiene; 1,4-heptadiene; 1,5-heptadiene; 1,5-octadiene; dicyclopentadiene; Z-methylene 2,5 norbornene; 4,7,8,9-tetrahydromethylindene; and similar compounds.
1 Such products are illustrated, for example, in Canadian Pat. No. 703,930, which issued on Feb. 16,1965.
For use in this invention the insulating compositions are compounded by previously known methods with the appropriate curing or cross-linking agents, accelerators, plasticizers, antioxidants, reinforcing fillers and the like. The composition may be extruded onto the base conductor or onto the conductor already coated with a semiconductive layer. They are then cured as described in more detail below.
The chlorosulfonated polyethylenes used in the invention are known products obtained by reacting polyethylone with chlorine and sulfur dioxide in accordance with known methods. Generally the polyethylene utilized has a number average molecular weight of the order of about 20,000. The sulfur content of the product is normally from about 1.2% to 1.7%, and the chlorine content from about 26% to 40%. The use of chlorosulfonated polyethylene as the carrier for the semiconductive compositions is a special feature of this invention. In addition to the fact that it is possible by utilization of the polymer to effect the above described contiguous relationship, the polymer also has excellent physical and mechanical characteristics. This makes it possible to obtain calendered sheets of minimum thickness to be utilized in the preparation of the winding tapes employed in the invention. Such products are described, for example, at pages 387-390 of Polymers and Resins, by Brage Golding, Van Nos- I trand co; Inc'., New York, 1959.
For the preparation of the semiconductive compositions, the chlorosulfonated polyethylene is compounded with the appropriate ingredients, including the conductive particles, plasticizers such as basic lead phthalate and stabilizers such as polyethylene glycol. The compounding procedures are in accordance with standard practice. Useful compositions suggested by way of example may contain, for example, from about 40 to 70 parts carbon black, to 20 parts basic lead phthalate and 0.5 to 1 parts of polyethylene glycol per 100 parts of chlorosulfonated polyethylene. For the preparation of tapes the composition is calendered to produce a sheet having a thickness of from about 0.1 to 0.5 mm. from which the tapes can be prepared by cutting. I
The products of this invention may be prepared by any of a number of methods. All of them include a step in which a semiconductive layer in contact with an insulating layer is heated at a temperature of from about 100 C. to 200 C. for a sufficient period of time to elfect the contiguous relationship. During this period the semiconductive material may seal to itself at overlapping points. The time of heating may vary within a very wide range, and the best time will be selected on the basis of the selected temperature, the dimensions of the cable, economy and ease of operation. Suitable heating periods will normally be within the range of from about 30 minutes to 3 hours.
In one procedure a tape of the semiconductive composition is helically wound on a conductor previously coated with the cured polyolefin elastomer and the resulting product heated as described above. 7
Alternatively the semiconductive composition may be coated directly on the conductor by extruding or by winding a tape, and the insulating material extruded onto the first layer. This product may be coated with a second semiconductive layer, and the completedunit heated to effect simultaneous curing of the insulator and pressure fitting of the semiconductive layers to the conductor and to the insulating layer.
In still another embodiment of the invention the semiconductive composition may be extruded directly on an insulated conductor at a temperature in the above defined range so as to obtain a semiconductive layer in contiguous relationship with the insulating layer in one operation.
One very convenient procedure for heating the unit comprising the conductor and the insulating and semiconductive layers is to cover it with a protective sheath in the form of a heat stable fabric such as cotton, rayon,
nylon or the like, or to cover it with a metallic sheath.
In either event the protected unit is' then conducted through a heating zone such'as an oven to bring the temperature to the defined level. The protective sheath is then removed.
A permanent protective sheath can also be used. For example, the unit could be coated with an elastomer such as polychloroprene, by any of the usual methods such as extrusion, and the protected unit then heated to cure the elastomer while at the same time bringing the semiconductive layer into contiguous relationship with the insulating layer.
The invention may be better understood by reference to the attached drawing illustrating one aspect of the invention. In the drawing, 1 is a conductive cable, 2 is the insulating layer, and 3 is the semiconductive layer.
What is claimed is:
1. A medium voltage electric cable comprising a conductor insulated with-an insulating layer of a cured amorphous olefine copolymer selected among the saturated and unsaturated amorphous olefine copolymers,'a surface of said insulating layer being in nonadhesive pressure contact with an adjacent surface of a semiconductive layer comprising conductive carbon particles dispersed in chlorosulfonated polyethylene, there being substantially no hollow spaces between said insulating layer and said semiconductive layer.
2. Acable as in claim 1 in which the insulating layer is under the semiconductive layer.
3. A cable as in claim -1 in which the insulating layer is sandwiched between two semiconductive layers.
4. A cable as in claim 1 in which the semiconductive layer is under the insulating layer.
5. A cable as in claim 1 in which the semiconductive layer is a tape winding.
References Cited UNITED STATES PATENTS 2,090,510 8/1937 Bower 174-121.2
3,049,584 8/1962 DAscoli 174120.2
3,098,893 7/1963 Pringle 174102.2
. 3,260,694 7 1966 Wang.
3,325,325 6/1967 Ward 174-110.44 X
703,930 2/ 1965 Canada.
E. A. GOLDBERG, Primary Examiner U.S. Cl. X.R. l17218; 174-102
US730657A 1967-05-23 1968-05-20 Medium voltage cables Expired - Lifetime US3541228A (en)

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AT (1) AT278124B (en)
BE (1) BE713479A (en)
CH (1) CH475636A (en)
DE (1) DE1765376A1 (en)
ES (1) ES354025A1 (en)
FR (1) FR1568381A (en)
GB (1) GB1150690A (en)
LU (1) LU55968A1 (en)
NL (1) NL6805644A (en)
NO (1) NO127886B (en)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3705257A (en) * 1972-03-06 1972-12-05 Anaconda Wire & Cable Co Electric cable and method of making
US3787255A (en) * 1972-05-30 1974-01-22 Essex International Inc Insulated cable with sheath of controlled peel strength and method
JPS4913680A (en) * 1972-05-17 1974-02-06
US3876462A (en) * 1972-05-30 1975-04-08 Essex International Inc Insulated cable with layer of controlled peel strength
US3878319A (en) * 1974-07-08 1975-04-15 Gen Electric Corona-resistant ethylene-propylene rubber insulated power cable
US3888718A (en) * 1971-07-21 1975-06-10 Anaconda Co Apparatus for applying a dual extrusion over a cable conductor
US3935042A (en) * 1974-07-08 1976-01-27 General Electric Company Method of manufacturing corona-resistant ethylene-propylene rubber insulated power cable, and the product thereof
US4008113A (en) * 1974-05-11 1977-02-15 Kabel-Und Metallwerke Gutehoffnungshutte Aktiengesellschaft High voltage cable
US4170575A (en) * 1974-05-16 1979-10-09 General Electric Company Compound for patching voids in a semi-conductive component of insulated electric cable

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3569610A (en) * 1969-10-15 1971-03-09 Gen Cable Corp Ethylene-propylene rubber insulated cable with cross-linked polyethylene strand shielding
US3748369A (en) * 1971-03-08 1973-07-24 Gen Cable Corp Method of shielding high voltage solid dielectric power cables
US3735025A (en) * 1971-07-30 1973-05-22 Anaconda Wire & Cable Co Semiconducting composition and cable jacketed therewith
FR2245058B1 (en) * 1973-09-25 1977-08-12 Thomson Brandt
FR2359488A1 (en) * 1976-07-22 1978-02-17 Telecommunications Sa Semiconducting electric cable layer - contg. ethylene! vinyl! acetate copolymer is non-adherent and heat-resistant
DE2723488C3 (en) * 1977-05-21 1983-12-29 AEG-Telefunken Kabelwerke AG, Rheydt, 4050 Mönchengladbach Electrical cable with plastic insulation and outer conductive layer
US4487828A (en) * 1983-06-03 1984-12-11 At&T Technologies, Inc. Method of manufacturing printed circuit boards

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2090510A (en) * 1931-05-09 1937-08-17 Gen Cable Corp Electrical conductor and method of manufacture
US3049584A (en) * 1959-02-10 1962-08-14 Anaconda Wire & Cable Co High voltage shielding composition
US3098893A (en) * 1961-03-30 1963-07-23 Gen Electric Low electrical resistance composition and cable made therefrom
CA703930A (en) * 1965-02-16 B. Feild George Insulated electrical conductors
US3260694A (en) * 1962-01-09 1966-07-12 Phelps Dodge Copper Prod Cross-linked chlorinated polyethylene
US3325325A (en) * 1958-05-21 1967-06-13 Gen Electric Method of making polyethylene insulated electrical conductors

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA703930A (en) * 1965-02-16 B. Feild George Insulated electrical conductors
US2090510A (en) * 1931-05-09 1937-08-17 Gen Cable Corp Electrical conductor and method of manufacture
US3325325A (en) * 1958-05-21 1967-06-13 Gen Electric Method of making polyethylene insulated electrical conductors
US3049584A (en) * 1959-02-10 1962-08-14 Anaconda Wire & Cable Co High voltage shielding composition
US3098893A (en) * 1961-03-30 1963-07-23 Gen Electric Low electrical resistance composition and cable made therefrom
US3260694A (en) * 1962-01-09 1966-07-12 Phelps Dodge Copper Prod Cross-linked chlorinated polyethylene

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3888718A (en) * 1971-07-21 1975-06-10 Anaconda Co Apparatus for applying a dual extrusion over a cable conductor
US3705257A (en) * 1972-03-06 1972-12-05 Anaconda Wire & Cable Co Electric cable and method of making
JPS4913680A (en) * 1972-05-17 1974-02-06
JPS5514489B2 (en) * 1972-05-17 1980-04-16
US3787255A (en) * 1972-05-30 1974-01-22 Essex International Inc Insulated cable with sheath of controlled peel strength and method
US3876462A (en) * 1972-05-30 1975-04-08 Essex International Inc Insulated cable with layer of controlled peel strength
US4008113A (en) * 1974-05-11 1977-02-15 Kabel-Und Metallwerke Gutehoffnungshutte Aktiengesellschaft High voltage cable
US4170575A (en) * 1974-05-16 1979-10-09 General Electric Company Compound for patching voids in a semi-conductive component of insulated electric cable
US3878319A (en) * 1974-07-08 1975-04-15 Gen Electric Corona-resistant ethylene-propylene rubber insulated power cable
US3935042A (en) * 1974-07-08 1976-01-27 General Electric Company Method of manufacturing corona-resistant ethylene-propylene rubber insulated power cable, and the product thereof

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ES354025A1 (en) 1969-10-16
LU55968A1 (en) 1968-07-12
BE713479A (en) 1968-08-16
GB1150690A (en) 1969-04-30
AT278124B (en) 1970-01-26
US3677849A (en) 1972-07-18
NO127886B (en) 1973-08-27
FR1568381A (en) 1969-05-23
CH475636A (en) 1969-07-15
NL6805644A (en) 1968-11-25
DE1765376A1 (en) 1971-07-22

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Owner name: SOCIETA PIRELLI S.P.A., PIAZZALE CADORNA 5, 20123

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