US2532152A - Thin paper insulated electric cable - Google Patents

Thin paper insulated electric cable Download PDF

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Publication number
US2532152A
US2532152A US696144A US69614446A US2532152A US 2532152 A US2532152 A US 2532152A US 696144 A US696144 A US 696144A US 69614446 A US69614446 A US 69614446A US 2532152 A US2532152 A US 2532152A
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United States
Prior art keywords
paper
thickness
layers
strips
insulation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US696144A
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English (en)
Inventor
Domenach Louis
Macardier Louis
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Alcatel Lucent SAS
Original Assignee
Compagnie Generale dElectricite SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Compagnie Generale dElectricite SA filed Critical Compagnie Generale dElectricite SA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00—Insulated conductors or cables characterised by their form
    • H01B7/02—Disposition of insulation
    • 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
    • H01B9/0616—Oil-pressure cables with enclosed conduits

Definitions

  • Our invention relates to electric cables for high voltages of the type obtained by winding strips or impregnated insulating paper or a number of layers thereof round the conductor member.
  • Our present invention removes these drawbacks. It is based on the fact that for a given radius of curvature the tensile stresses which have a tendency of producing tears breadthwise are smaller when the breadth of the strips is smaller. As to the transverse stresses which produce longitudinal tears by reason of the elongation of the outer fibres of the cable, it is apparent that the sliding of the strips over one another under the action of a common transverse tensile stress becomes more and more easy when the surface through which the strips engage one another is more reduced, whereby the tearing of the thin paper under the action of transverse stresses may also be avoided through the use of narrow paper strips.
  • Our invention has thus for its object to provide electric cables for high voltages, which cables are insulated with impregnated paper the strips of which are wound so as to form a number of layers round the cable conductors.
  • the cables according to our invention are provided with insulating material constituted at least in the vicinity or the conductors of thin paper strips the thickness of which is equal to or less than 0.04 millimeter, said strips being cut in small widths in order to avoid or at least to reduce the risks of tearing.
  • the breadth of the strips will be chosen in accordance with our invention preferably between 7 and 14 ms.
  • Our invention has particularly for its object, cables insulated by means of paper impregnated with viscous material or fluid oil, and it is particularly applicable in the case of cables the insulation of which is maintained under the pressure either through the action of a compressed gas contained inside the fluid-tight sheath and forming part of the dielectric material, or else through the action of a compressed gas on the outside of the fluid-tight sheath, or again by means of oil communicating with the channels inside the cables as in the case of cables containing fluid oil.
  • the relative values of the pressure and of the thicknesses of the paper strips to be chosen are related to one another by the value required for the safety coefficient of the cable with reference to voltage rises.
  • This coefilcient may be expressed as a ratio between the breakdown gradient Go with reference to the surges and the working gradient g under the service voltage at commercial frequencies, said operating gradient g being itself a fraction of the breaking gradient Gr at usual service frequency.
  • the cables submitted to oil or gas pressure and including a dielectric material made of thin paper are, in accordance with our invention, submitted to absolute working pressures above kgs. per sq. cm. throughout their length.
  • the electric capacity of the insulation per unit length is in our improved cable greater than in any known cables, and the radial circulation leads to a difference in pressure or loss of head which is greater between the conductor and the metal sheath.
  • said increase in the thickness of the paper should preferably be executed so as to retain a constant ratio between the working gradient in the different layers of insulation and the break-down gradient in the corresponding gaps.
  • the progressive variation in the thickness of the paper will be advantageously provided in a manner such that, taking into account the pressure applied, it may be possible to obtain throughout the thickness of the insulation and for the working gradient thereof, substantially the same safety coefiicient with reference to voltage rises of internal and atmospheric origin.
  • the paper used in the vicinity of the conductor is preferably constituted by paper made with rags of flax paste, cut into sufilciently narrow strips; it is possible to use in usual ribbon winding machines such papers under a thickness of 15 thousandths of a millimeter. It is also possible with greater care, to make use of thinner papers such as those used in the manufacture of condensers and the thickness of which may be as low as about 7 thousandths of a millimeter.
  • Rag papers having a flax paste basis possess the advantage of having a mechanical strength and an elongation which are greater than those of the kraft paper normally used in the case of high voltage cables. Their dielectric losses are also smaller.
  • the thickness of the paper When, by increasing the thickness of the paper, it is possible to reach a thickness for which the gradient of working is that of normal paper, we wind over the layer of thin paper made of flax paste, normal kraft paper. By reason of its thickness, the latter does not require possessing mechanical properties as good as those of the thin paper. Its thickness which is first equal to about 4 to 5 hundredths of a millimeter may increase up to 13 to 15 hundredths of a millimeter on the outside of the insulation.
  • the breadth of the thin paper strips in the vicinity of the conductor is advantageously comprised between 7 and 14 millimeters according to the cross-section of the conductors.
  • Fig. l is a cross-sectional view of the cable.
  • Fig. 2 is a perspective view of the cable with the several elements broken away;
  • Fig. 3 is an enlarged partial sectional view showing a few of the metal conductors of the cable and some of the cable insulating paper nearest to them which is constituted according to the above-described modification in which that portion of the paper is made up of groups of a few layers of the thinnest paper and the groups are separated from one another by layers of thicker paper, the thickness of all of the layers of paper being greatly exaggerated to enable legible showing in cross-section of the relative thicknesses of the layers.
  • I designates the central channel of the cable for the oil while 2 designates the copper or aluminium conductor made of suitably shaped wires assembled together, or else of cylindrical wires wound over a steel helix I0.
  • the thinnest paper ribbons surrounding the conductor are illustrated at 3; the breadth of said strips is comprised between 7 and 14 mms. according to the value of the radius of the conductor.
  • Their thickness is equal to or less than 4 hundredths of a millimeter and they are made of rag paper having flax paste as a basis.
  • the working gradient is gradually reduced, whereby the thickness of the paper may be rapidly increased while retaining in the layers furthest removed from the conductor 2, the same coefficient of safety for the working gradient as that which exists in close proximity with the conductor.
  • the cable is manufactured and impregnated by any known method.
  • the fluidtight sheath of lead or aluminum is shown at I; over this sheath is applied a hoop 8 for binding same, which hoop is protected in its turn by a fluidtight sheath 0 protected by the usual cover.
  • the pressure required is kept up inside the cable by means of containers of oil under pressure distributed at intervals along the pipe and connected with the inner central channel I of the cable through Junction joints and terminal boxes.
  • the central oil channel I of the cable may be supplemented or else replaced by peripheral channels II provided in any suitable manner at the inner surface of the metal sheath 1 in contact with the impregnated insulating material.
  • All these channels instead of being filled with oil under pressure may contain a compressed gas acting on the insulation made of impregnated paper according to our invention.
  • a high voltage electric cable comprising a conductor, an enclosing sheath, and a dielectric layer between said conductor and said sheath, said layer comprising wound narrow strips of thin paper and oil under heavy pressure, said paper being rag paper made with flax paste, and at least near said conductor including a substantial number of strips not exceeding 0.015 millimeter in thickness, and said pressure being substantially in the range of 10 to 20 kilograms per square centimeter.
  • a high voltage electric cable comprising a conductor, an enclosing sheath, and insulation between said conductor and said sheath, said insulation comprising wound narrow strips of thin paper and oil under heavy pressure, at least the layers of said insulation near said conductor being constituted by winding in alternation, first two strips of paper substantially 0.02 millimeter thick, and then one strip of paper substantially 0.04 millimeter thick, and said pressure being substantially in the range of 10 to 20 kilograms per square centimeter.
  • a high voltage electric cable comprising a conductor, an enclosing sheath, and a dielectric layer between said conductor and said sheath, said layer comprising wound narrow strips of thin paper and oil under heavy pressure, said paper being rag paper made with flax paste, and at least near said conductor including a substantial number of strips substantially 0.007 millimeter in thickness, and said pressure being substantially in the range of 10 to 20 kilograms per square centimeter.
  • An insulated electric conductor including an electrically conductive element having insulation surrounding said conductive element, said insulation including paper and oil under pressure, said paper being disposed in a plurality of superposed layers, a plurality of said layers of said paper being thin paper the maximum thickness of which it not substantially in excess of 0.04 millimeter, and a substantial number of said layers of thin paper being adjacent to said conductive element, and said oil pressure being substantially in excess of atmospheric pressure.
  • An insulated electric conductor including an electrically conductive element having insulation surrounding said conductive element, said in sulation including paper and oil under pressure, said paper being disposed in a plurality of superposed layers, a plurality of said layers of said paper being thin flax paste paper the maximum thickness of which is not substantially in excess of 0.04 millimeter, and a substantial number of said layers or thin paper being adjacent to said conductive element, and said oil pressure being substantially in excess of atmospheric pressure.
  • an insulated conductor including an electrically conductive element and an insulating element surrounding said conductive element, and a liquid-tight enclosure surrounding said elements, said insulating element including paper and oil under pressure, a-substantial proportion of said paper being thin paper the maximum thickness of which is not substantially in excessof 0.04 millimeter, and a substantial portion of said thin paper being adiacent to said conductive element, and said oil pressure being substantially in excess of atmospheric pressure.
  • An insulated electric conductor including an electrically conductive element having insulation surrounding said conductive element, said insulation including paper and oil under pressure, said paper being disposed in a plurality of superposed layers, a substantial number of said layers of said paper adjacent said conductive element being thin paper the maximum thickness of which is not substantially inexcess of 0.04 millimeter and said layers increasing in thickness in the successive strata from the stratum of layers adjacent said conductive element to the stratum of layers at the outer periphery of said paper insulation, and said oil pressure being substantially in excess of. atmospheric pressure.
  • an insulated electric conductor includingan electrically conductive element and an insulating element enclosing said conductivev element, and a liquid-tight enclosure surrounding said elements, said insulating element including paper and oil under pressure substantially in excess of atmospheric pressure, said paper including strips of paper wound in layers about the axis of said conductive element, a substantial number of said layers of paper being thin paper the maximum thickness of which is not substantially in excess of 0.04 millimeter and the maximum width of which is not substantially in excess of 14 millimeters. and a plurality of said 8 layers of thin paper being adjacent to said conductive element.
  • an insulated electric conductor including an electrically conductive element and an insulating element enclosing said conductive element, and a liquid-tight enclosure surrounding said elements, said insulating element including paper and oil under pressure, said paper including narrow strips of paper wound in layers about the axis of said conductive element, a plurality of said layers of paper being thin paper the maximum thickness of which'is substantially within the range of 0.007 to 0.04 millimeter and a substantial number of said layers of thin paper being adjacent to said conductive element, and said oil pressure being substantially within the range of approximately 10 to 20 kilograms per square centimeter.
  • An insulated electric conductor including an electrically conductive element having insulation surrounding said conductive element, said insulation including paper and oil under pressure substantially in excess of atmospheric pressure, said paper including a plurality of groups of layers of thin paper which'has a thickness not substantially in excess of 0.04 millimeter and layers of substantially thicker paper respectively separating each group of layers of thin paper from its next adjacent groups, at least one such group of layers of thin paper being adjacent to said conductive element.
  • an insulated electric conductor including an electrically conductive element having an insulating element enclosing said conductive element, a liquid-tight sheath surrounding said elements, and a fluid-tight enclosure surrounding said sheath and containing fluid under a pressure in excess of 5 kilograms per square centimeter, said insulating element including paper impregnated with fluid oil and disposed about the axis of said conductive element in a plurality of layers, a plurality of said layers of said paper being thin paper the maximum thickness of which is not substantially in excess of 0.04 millimeter, and a substantial number of said layers of thin paper being adjacent said conductive element.

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  • Organic Insulating Materials (AREA)
US696144A 1944-02-25 1946-09-11 Thin paper insulated electric cable Expired - Lifetime US2532152A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR989668T 1944-02-25

Publications (1)

Publication Number Publication Date
US2532152A true US2532152A (en) 1950-11-28

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Family Applications (1)

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US696144A Expired - Lifetime US2532152A (en) 1944-02-25 1946-09-11 Thin paper insulated electric cable

Country Status (5)

Country Link
US (1) US2532152A (en, 2012)
BE (1) BE467409A (en, 2012)
FR (1) FR989668A (en, 2012)
GB (1) GB613797A (en, 2012)
NL (1) NL61796C (en, 2012)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2668186A (en) * 1948-05-28 1954-02-02 Comp Generale Electricite Electric cable with oil pressure outside the insulation
EP0012560A1 (en) * 1978-12-11 1980-06-25 Dielectric International Limited Electrical equipment employing insulants
WO2013071945A1 (en) * 2011-11-14 2013-05-23 Abb Research Ltd A solid direct current (dc) transmission system comprising a laminated insulation layer and method of manufacturing

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1524124A (en) * 1920-07-03 1925-01-27 Standard Underground Cable Co Canada Construction of cables
US2015063A (en) * 1935-09-24 Electric cable
US2047000A (en) * 1931-02-24 1936-07-07 Gen Electric Electrical connecter unit for metal clad switch gears
US2067169A (en) * 1932-02-09 1937-01-12 Glover & Co Ltd W T Electric cable

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2015063A (en) * 1935-09-24 Electric cable
US1524124A (en) * 1920-07-03 1925-01-27 Standard Underground Cable Co Canada Construction of cables
US2047000A (en) * 1931-02-24 1936-07-07 Gen Electric Electrical connecter unit for metal clad switch gears
US2067169A (en) * 1932-02-09 1937-01-12 Glover & Co Ltd W T Electric cable

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2668186A (en) * 1948-05-28 1954-02-02 Comp Generale Electricite Electric cable with oil pressure outside the insulation
EP0012560A1 (en) * 1978-12-11 1980-06-25 Dielectric International Limited Electrical equipment employing insulants
WO2013071945A1 (en) * 2011-11-14 2013-05-23 Abb Research Ltd A solid direct current (dc) transmission system comprising a laminated insulation layer and method of manufacturing

Also Published As

Publication number Publication date
GB613797A (en) 1948-12-02
BE467409A (en, 2012)
FR989668A (fr) 1951-09-12
NL61796C (en, 2012)

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