Capacitive Cable

Abstract

A capacitive cable comprised six long, thin and narrow electrode plates or strips 101, 102, 103, 104, 105, 106. Typically they are 5 km long, 10 cm wide and 0.5 mm thick of aluminium or copper foil. Individual ones of them are separated by 0.25 mm thick polypropylene ribbons 107 insulating the individual strips from each other in an insulating manner. The assembly of strips and ribbons is contained within an insulating sheath 108.

At opposite ends 111,112, the alternate strips are cut off short and the remaining fingers 114,115 are joined together and to connection wires 116,117, typically by riveting 118. The wires are insulated and the insulating sheath extends onto the insulation of the wires, whereby the entire cable is insulated for safe contact with foreign objects between the ends.

Claims

1. A multi-phase cable comprising a plurality of capacitive cables, wherein each capacitive cable comprises: at least two elongate electrode plates of one polarity, these plates being inter-connected at one end of the cable; at least two elongate electrode plates of another polarity, these plates being: interdigitated with the plates of the one polarity and being interconnected at the other end of the cable; and dielectric material between the interdigitated plates, wherein the plates are collectively encased in an outer casing or sheath.

2. A multi-phase cable as claimed in claim 1, wherein the interdigitated plates are housed between resilient binding members, to retain the plates close to each other for maintained capacitance.

3. A multi-phase cable as claimed in claim 2, wherein the resilient binding members are adapted to be held together along their edges.

4. A multi-phase cable as claimed in claim 3, wherein the resilient binding members comprise a trough and tongue each having interengaging formations adapted to hold them together.

5. A multi-phase cable as claimed in claim 2, wherein the resilient binding members have a free curvature away from the plates, whereby the binding members are flattened when interengaged and apply pressure across the area of the plates pressing them in towards each other.

6. A multi-phase cable as claimed in claim 1, wherein the individual capacitive cables are placed parallel to each other.

7. A multi-phase cable as claimed in claim 1, wherein the individual capacitive cables are arranged to radiate from a central axis, forming radiating capacitive cables.

8. A multi-phase cable as claimed in claim 7, including divergent spacers between the radiating capacitive cables.

9. A multi-phase cable as claimed in claim 8, wherein the divergent spacers are circular cylindrical in shape, squeezed to divergent shape when in place.

10. A multi-phase cable as claimed in claim 8, wherein the divergent spacers are individual 120? divergent plastics material extrusions or a single 360? extrusion with flat cable slots set at 120?.

11. A multi-phase cable as claimed in claim 1, including a central earth wire and/or an outer casing of helically arranged earth wires.

Description

[0018] To help understanding of the invention, a specific embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which:

[0019] FIG. 1 is FIG. 1 of WO 2010/026380,

[0020] FIG. 2 is a perspective, broken view of the plates at both ends of a capacitive cable of indefinite length in accordance with the invention,

[0021] FIG. 3 is a cross-sectional side view of one end of the cable of FIG. 2,

[0022] FIG. 4 is a plan view of the one end of the cable of FIG. 2,

[0023] FIG. 5 is a cross-sectional end view of the cable of FIG. 2 in position to be closed in a sheath comprising a trough and a cover, which are outwardly concave,

[0024] FIG. 6 is a view similar to FIG. 5, showing the sheath closed,

[0025] FIG. 7 is a similar cross-sectional view of three cables in a tri-radial carrier having an armoured casing.

[0026] Referring to FIGS. 2 to 4 of the drawings, the cable thereshown is comprised of six long, thin and narrow electrode plates or strips 101, 102, 103, 104, 105, 106. Typically they are 5 km long, 10 cm wide and 0.5 mm thick of aluminium or copper foil. Individual ones of them are separated by 0.25 mm thick polypropylene ribbons 107 insulating the individual strips from each other in an insulating manner. The assembly of strips and ribbons is contained within an insulating sheath 108.

[0027] At opposite ends 111,112, the alternate strips are cut off short and the remaining fingers 114,115 are joined together and to connection wires 116,117, typically by riveting 118. The wires are insulated and the insulating sheath extends onto the insulation of the wires, whereby the entire cable is insulated for safe contact with foreign objects between the ends.

[0028] To maintain the electrode strips in contact with their separation ribbons, the cable, including the insulation sheath is held within an outer sleeve 121 made up of shallow channel-shaped trough 122 with over-hanging rims 123 and a closure tongue 124 with up-standing lips 125. The trough and the tongue of the sleeve are or plastics material extrusions, moulded with outwardly concave curvature. For use, with the cable in the trough, the tongue is pushed into the trough, with both being flattened. The lips 125 engage under the rims, holding the curvature flattened and applying pressure to hold the strips against dielectric ribbons and the capacitance of the cable high.

[0029] For a single phase supply, two pairs of cables are required. They can be bound together flat and edge-to-edge within an earth screen. The edge to edge arrangement mitigates against capacitive interference between cables. Alternatively they can be laid against the opposite sides of a hollow square extrusion of dielectric material, again to mitigate interference and again within an earth screen.

[0030] For three phases, the arrangement of FIG. 7 can be used. A tri-radial plastics material extrusion 131 has a small central tube 132, from which radiate three pairs of webs 133, leaving between them radial slots 134 of a size to accommodate a cable within its outer sleeve 121. Circularly shaped flanges 135 extend between neighbouring webs 133 between adjacent slots 134.

[0031] With three cable cables accommodated, a wrapping 136 secures them. Around this earthing, armouring of steel wires 137 is wound followed by an external waterproof sheath 138.

[0032] We envisage the following typical parameters for our cables: [0033] Lengthsbetween 1 km and 1000 km, usually between 1 km and 100 km [0034] Widthsbetween 50 mm and 150 mm [0035] Combined Thickness (Foil and Dielectric)up to 10 mm [0036] No of platesbetween 8 and 30 [0037] Plate thickness up to 0.1 mm [0038] Plate materialAluminium or Copper [0039] Dielectric thicknessup to 0.5 mm [0040] Dielectric materialPolypropylene [0041] Capacitance80 microF per km [0042] Power capacity0.5 to 5 GVA.
The invention is not intended to be restricted to the details of the above described embodiments. For instance:

[0043] The first embodiment can in place of the trough 122 and tongue 124 have two concave tongues and two U-shaped extrusions clipped onto the edges of the tongues to urge them against the strip and ribbon assembly;

[0044] The second embodiment can have an earth wire may be incorporated in a central tube 130 of the tri-radial moulding, with the armouring of the cable being polymeric. Further the voids between the radial webs 133 may be filled with material to urge the plates into close capacitive contact.

[0045] The invention also provides the following embodiments:

1. A capacitive cable comprising: [0046] at least two elongate electrode plates of one polarity, these plates being inter-connected at one end of the cable; [0047] at least two elongate electrode plates of another polarity, these plates being: [0048] interdigitated with the plates of the one polarity and being [0049] interconnected at the other end of the cable; and [0050] dielectric material between the interdigitated plates.
2. A capacitive cable as disclosed in embodiment 1, wherein the interdigitated plates are housed between resilient binding members, to retain the plates close to each other for maintained capacitance, the resilient binding members are preferably adapted to be held together along their edges and preferably comprise a trough and tongue each having interengaging formations adapted to hold them together.
3. A capacitive cable as disclosed in embodiment 2, wherein the resilient binding members have a free curvature away from the plates, whereby the binding members are flattened when interengaged and apply pressure across the area of the plates pressing them in towards each other.
4. A capacitive cable as disclosed in embodiment 1, embodiment 2 or embodiment 3, wherein the plates are encased in an outer casing or sheath, either individually forming a single phase cable or collectively forming a multi-phase cable.
5. A capacitive cable as disclosed in embodiment 4, wherein the individual cables are placed parallel to each other.
6. A capacitive cable as disclosed in embodiment 4, wherein the individual cables are arranged to radiate from a central axis.
7. A capacitive cable as disclosed in embodiment 6, including divergent spacers between the radiating cables.
8. A capacitive cable as disclosed in embodiment 7, wherein the divergent spacers are circular cylindrical in shape, squeezed to divergent shape when in place.
9. A capacitive cable as disclosed in embodiment 7, wherein the divergent spacers are individual 120? divergent plastics material extrusions or a single 360? extrusion with flat cable slots set at 120?.
10. A capacitive cable as disclosed in any preceding embodiment, including a central earth wire and/or an outer casing of helically arranged earth wires.