Classifications

• • 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
  • H01B9/00—Power cables
  • H01B9/02—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients
  • H01B9/025—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients composed of helicoidally wound wire-conductors

Definitions

• the present invention relates to a metal screen for a power cable with a predetermined number of mutually twisted cable cores.
• a power cable metal screen has the task of leading off the current passing through the insulation layers of the cable cores, and also to serve as a conductor for earth fault currents in operational disturbances such as dielec ⁇ tric breakdown in the cable insulation layers.
• Such a screen usually consists of a plurality of metal wires or ribbons along the cable surface, but may also be a solid metal tube, e g of lead.
• a metal screen e g built up from copper wires, generally has considerably less conductive area than the main or phase conductors in the cable. There are standards prescribing that the screening conductor shall have a given density or largest average opening in respect of the cable circumference. The number of wires in the screen will thus be minimized and the wire diameter relatively small, usually about 1 mm.
• One object of the present invention is to provide a metal screen with which the risk of rupture is reduced simultaneously as good bending properties of the cable are .maintained. Another object is to provide a metal screen which is protected from corrosion. A third object is to provide a metal screen, which simplifies the manufacture of a screened power cable. This is achieved by the metal screen in accordance with the invention having been given the charac ⁇ terizing features disclosed in the claims.
• Figure 1 is a cross section of a power cable with a first embodiment of the metal screen in accordance with the invention
• Figure 2 is a perspective view of a power cable with a second embodiment of the metal screen in accordance with the invention
• Figure 3 is a cross section of a power cable with a third embodiment of the metal screen in accordance with the invention
• Figure 4 is- a cross section of a power cable with a fourth embodiment of the metal screen in accordance with the invention.
• FIG. 1 A cross section of- a power cable with three cores is illustrated in Figure 1, each of the cores containing a conductor 1, e g of copper or aluminium, on which a semiconductive layer 2, e g of conductive plastics, has been extruded.
• An insulating layer 3 is extruded on said layer 2, and a second semiconductive layer 4, e g of conductive plastics, is extruded on the insulation layer 3.
• the cross section of each core is sector-shaped, and the three cores are laid in relation to each other such that their cylindrical backs face outwards to provide a substantially circular cross-sectional shape for the collected cores.
• the screen 5 illustrated in Figure 1 includes a predetermined number of metal
• the wires 7 may be bedded into a layer of a material which is preferably electrically conductive and protects the wires against corrosion.
• the thickness of this layer exceeds by. some tenths of a millimeter the thickness of the wires.
• the layer in which the wires 7 are embedded can be applied by direct extrusion in the cable-making machine shortly after the
• the cores and associated screening wires are simultaneously twisted and laid in their final position.
• the screening wires 7 will then be situated on the back of the respective core and at substantially uniform spacing.
• the plastics jacket 6 is extruded on the outside of the screen 5 with the screen wires 7.
• FIG. 15 A second embodiment of the metal screen in accordance with the invention is illustrated in Figure 2 for a cable of the same type as shown in Figure 1.
• Figure 1 may have certain practical disadvantages, e g during changing drums,
• the cable includes three cores, as with the embodiment according to Figure 1, these cores being made up in the same way as those of Figure 1 with a conductor 1 surrounded, in
• the screen comprises a separate screening ribbon 8 for each core, i e three screening ribbons 8 in the present case. These screening ribbons 8 are
• FIG. 3 there is shown an embodiment of a cable with cores having circular cross section, as is the case with small cable dimensions.
• the cores shown in Figure 3 are otherwise built up in the same way as those in Figure 1 and Figure 2, i e with a conductor 1, in order surrounded by a semiconductive layer 2, an insulating layer 3 and a further semiconductive layer 4.
• the intermediate spaces between the cores must be filled out. This can be attained, for example, by the type of screening ribbon 8 shown in Figure 2, which has been thickened out along its edges in the manner shown in Figure 3.
• the screening ribbons 8 shown in Figure 3 also include a predetermined number of screening wires 7, which have been embedded beforehand in a layer of material, e g conductive plastics or rubber.
• the latter may be ' provided on their backs with longitudinal, parallel grooves 10 for accommodat ⁇ ing a predetermined number of mutually parallel wires 7 in a manner illustrated in Figure 4, the construction of the cores illustrated in Figure 4 otherwise corresponding to the construction of the cores in Figures 1 and 2, i e they include an inner conductor 1, in order surrounded by a semiconductive layer 2, an insulating layer 3 and an outer semiconductive layer 4, in which the grooves 10 are provided.
• the cores with their respective screening wires 7 may be wound with a band or tape 9 before the jacket 6 is extruded onto the cable body.
• the screen will also be able to function as a diffusion barrier against moisture in the surroundings.

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• Insulated Conductors (AREA)
• Communication Cables (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=20344692

Family Applications (1)

Country Status (10)

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• 1981
  • 1981-10-02 SE SE8105835A patent/SE455906B/sv not_active IP Right Cessation
• 1982
  • 1982-09-22 JP JP57502983A patent/JPS58501647A/ja active Granted
  • 1982-09-22 AU AU89567/82A patent/AU551371B2/en not_active Ceased
  • 1982-09-22 DE DE8282902993T patent/DE3265626D1/de not_active Expired
  • 1982-09-22 EP EP82902993A patent/EP0089993B1/de not_active Expired
  • 1982-09-22 WO PCT/SE1982/000292 patent/WO1983001337A1/en active IP Right Grant
  • 1982-09-22 BR BR8207885A patent/BR8207885A/pt not_active IP Right Cessation
  • 1982-10-01 IT IT23574/82A patent/IT1152869B/it active
• 1983
  • 1983-05-13 FI FI831690A patent/FI72222C/sv not_active IP Right Cessation
  • 1983-06-01 DK DK249283A patent/DK149375C/da active

Non-Patent Citations (1)

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