AU2009318820B2 - An infrared radiation reflecting cable - Google Patents

Abstract

A cable 1.02 with improved heat performance has one or more of electrical conductors 1.04, 1.06, 1.08, which are mutually electrically insulated by individual insulation jackets 1.10, 1.12, 1.14. The cable has an external cable jacket 1.16 enclosing the insulated electrical conductors. A layer 1.20 which includes infrared reflecting pigmentation is applied over the jacket 1.16 to inhibit the heating of the cable by external IR radiation. In an alternative embodiment, the IR reflecting pigment can be incorporated in the external jacket 2.16. Mixed metal oxides, such as TiO

Description

C09386 1 An Infrared Radiation Reflecting Cable Field of the Invention [001] This invention relates to an improved cable. [002] In particular, the invention can be applied to the outer layer or jacket of an electric cable exposed to sunlight. Background of the Invention [003] Cable insulation for power cables is usually made of black plastic. In the past, the black colour has been achieved by adding carbon black as a pigment to the plastics material forming the outer cable jacket. The outer jacket is coloured black, and this can assist in preventing deterioration of the inner insulation by ultra-violet light. [004] Carbon absorbs radiation in the IR, visible, and UV ranges, and thus heats up when exposed to IR. [005] US6989056 discusses various IR reflective pigments and their disadvantages. US6989056 describes a black IR reflecting pigment made from a mixture of halogenated copper phthalocyanine and C.I. Pigment Violet 29 pigment (perylenetetra-carboxylic acid diimide). The specification suggests that this can be used as a pigment in, inter alia, plastics. The specification of US6989056 is silent as to the use of such plastics in a high voltage insulation environment, and as a cable jacket having requirements of strength, flexibility, water imperviousness, etc. [006] In countries with high levels of sun exposure, such as Australia, US, and African and Middle Eastern countries, cables can absorb substantial amounts of solar heat energy. This can have a deleterious effect on the performance of the cable, so that the cable's rating must be decreased from its nominal rating to prevent overheating. [007] It is desirable to mitigate the problem of de-rating of a cable due to the absorption of heat from the environment of a cable. Summary of the Invention [008] This invention is provides a cable having IR reflecting properties adapted to mitigate the problem heat absorption such as from exposure to sunlight or other sources of IR radiation. [009] According to an embodiment of the invention, there is provided a cable having at least a layer having IR reflecting properties. [010] The invention provides a cable having at least one inner electrical conductor, and an insulating jacket, and an IR reflecting layer adapted to reflect incoming IR radiation.

C09386 2 [011] The insulating jacket can incorporate or consist of the IR reflecting layer. [012] The cable can include an IR reflecting layer applied over the insulating layer. [013] The IR reflecting layer can be the external layer. [014] The electrically insulating layer can be applied over the electrically conducting core, the IR reflecting layer can be applied over the electrically insulating layer, and an outer skin can be applied over the IR reflecting layer. [015] The outer skin can be abrasion resistant. [016] The outer skin can be substantially transparent to IR radiation. [017] The IR transparent layer can include perylene. [018] The IR reflecting layer can incorporate one or more IR reflecting pigments. [019] The IR reflecting pigments can be mixed metal oxides. [020] The pigments include oxides of one or more of titanium, iron, and cobalt. [021] The outer layer can be the outer jacket of the cable. [022] The outer layer can be a skin applied to the cable jacket. [023] The IR reflecting properties can be provided by an IR reflecting pigment. [024] The outer layer can be black. [025] The cable jacket can be black. [026] The pigment can produce a black appearance. [027] The pigment can replace carbon black as the pigment in the cable jacket. [028] The jacket can be opaque to UV light. [029] Preferably, the cable is an AC power cable. [030] The cable mentioned in the paragraphs above can be an overhead high voltage power cable. [031] The IR reflective layer of the high voltage power table can disperse incident visible light. Brief Description of the Drawings [032] An embodiment or embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: C09386 3 [033] Figure 1 is a schematic representation of a cross section of a three conductor cable according to a first embodiment of the invention; [034] Figure 2 is a schematic representation of a cross section of a three conductor cable according to a second embodiment of the invention; [035] Figure 3 illustrates a single core cable according to an embodiment of the invention; [036] Figure 4 illustrates a second single core cable according to a further embodiment of the invention; [037] Figure 5 illustrates a third single core cable according to an embodiment of the invention. [038] Figure 6 illustrates a cable section according to a further embodiment of the invention. [039] Figure 7 illustrates a further embodiment of the invention comprising an overhead cable with a multi-wire core having an IR reflective coating. [040] The numbering convention used in the drawings is that the digits in front of the full stop or period indicate the drawing number, and the digits after the full stop or period are the element reference numbers. Where possible, the same element reference number is used in different drawings to indicate corresponding elements. Detailed Description of the Embodiment or Embodiments [041] The embodiments of the invention will be described with reference to the drawings. [042] Figure 1 illustrates a three conductor cable 1.02 having three multi-wire conductors 1.02 1.06, 1.08, each having an electrical insulation jacket 1.10, 1.12, 1.14. The electrical insulation can be, for example XLPE (cross-linked polyethylene). The three insulated conductors are contained in an external sheath 1.16. The sheath 1.16 can be coloured black, for example, by the addition of black pigments which either reflect or do not absorb IR radiation. A metallic foil moisture barrier 1.022 and a conductive screen 1.24 are provided within the sheath 1.16. [043] An outer skin 1.20 is applied over the sheath 1.16. The outer skin 1.20 has IR reflecting properties. The IR reflecting properties can be provided by incorporation of IR reflecting pigment in the skin. The skin can be made of the same material as the jacket with the addition of IR reflecting pigment, or it can be made from another suitable material whose composition has IR reflecting properties. Suitable IR reflecting pigments can include, but are not limited to IR reflecting metal oxides, particularly mixed metal oxides, and include those of titanium, iron, and cobalt, and mixtures thereof. The pigments can be prepared at calcining temperatures so are very heat stable and light stable and durable to weathering. Some commercial examples are Sicopal K 0095 from BASF, Ludwigshafen, Germany and Arctic black 462 from the Shepherd Color Company, Ohio C09386 4 USA. In plastic 2-4% is required for colour. These pigments may not contribute the same degree of opacity as carbon black, and preferably a range of IR reflective pigments from 3% to 4% is preferred. This means that additional stabilisers may be required. Hindered amine stabilisers can be used in a range of about 0.1% to 0.3%. Suitable commercial products include Chimassorb 944 from Ciba Specialty Chemicals Ltd, Basel, Switzerland. [044] The pigments such as TiO 2 are easier to disperse than carbon black when mixing the constituents and this facilitates processing. [045] The skin and IR reflective layers need to have adequate mechanical properties for the environment in which the cable will be used. Thus they may need to be flexible, abrasion resistant, water resistant, UV resistant, etc., depending on the specific application of the cable. [046] The skin 1.16 of Figure 1 can be applied to the entire length of the cable, for example, as an extrusion while the cable is being manufactured, or can be applied in the field to exposed sections of cable. The reflective layer can be applied as an extrusion or it can be applied in the manner of applying paint. [047] Figure 2 illustrates a cable according to a second embodiment of the invention. The cable 2.02 is a multi-core cable having three conductors 2.04, 2.06, 2.08, having corresponding electrically insulating jackets 2.10, 2.12, 2.14. In the cable shown in Figure 2, the IR reflective pigment is incorporated directly into the cable jacket 2.16. A water blocking compound 2.18 can be used to impede longitudinal water penetration id the outer jacket 2.16 is damaged. [048] The reflective pigment can completely replace the carbon black because carbon black strongly absorbs IR radiation. [049] In a preferred embodiment, additional additives, such as heat and UV stabilizers as discussed below can be included with the IR reflecting pigment. [050] Optionally, an outer jacket 2.17 can be applied over the IR reflective layer to improve physical characteristics such as abrasion resistance. This outer jacket can be transparent to IR. [051] Figure 3 illustrates a single core cable in which the single core 3.04 is enclosed by an electrically insulating jacket 3.10. An IR reflecting skin 3.16 is applied over the electrically insulating jacket 3.10. [052] Figure 4 illustrates a cable according to a further embodiment, in which the core 4.04 is enclosed by a single jacket which has both electrical insulating properties and IR reflecting properties.

C09386 5 [053] Figure 5 illustrates a cable structure according to a further embodiment of the invention. The conductive core 5.04 is enclosed by a two layer jacket. The jacket has an outer layer 5.24 and an inner layer 5.16. The outer layer 5.24 is a black layer which is transparent to IR radiation. Pigments such as perylene are transparent to IR, but not reflective. The inner layer 5.16 is an IR reflecting layer of any chosen colour achievable by the use of IR reflecting pigments or by the use of IR reflecting pigments in conjunction with other suitable pigments. In this embodiment, the inner layer 5.16 also provides electrical insulation. [054] This arrangement can be used to assist in reducing heat buildup. In the embodiment including a black layer over an inner substrate, the inner substrate can be an IR reflecting layer and the outer black layer can be an IR transparent layer. The inner substrate can be of any suitable colour achievable with suitable IR reflecting pigments, and can be white. This arrangement enables the use of non-black IR reflecting pigments while still providing a cable with a black exterior. Commercial pigments for the IR transparent outer layer include Paliogen black L0086 and Lumogen Black from BASF. [055] The external IR transparent layer 5.24 permits the incoming IR radiation to pass without significant heat increase. The inner IR reflecting layer 5.16 then reflects the incoming IR radiation back through the transparent outer layer 5.24, so the amount of IR radiation heating is significantly reduced. [056] Figure 6 illustrates a modified version of the arrangement of Figure 5 with an inner electrically insulating layer 6.22. As shown in Figure 6, the inner electrically insulating layer 6.22 is applied over the electrical conductors 6.04 between the conductors and the IR reflecting layer 6.016 and the IR transparent layer 6.024 is applied over the IR reflecting layer . A further IR transparent abrasion resistant layer (not shown) can be added to the outside of the cable if required. [057] While the cable illustrated in Figures 3, 4, 5, and 6 are single core cables, the same IR protection arrangements can be readily adapted for use with multi-core cables. [058] The cable can include an insect barrier such as nylon jacket. A sacrificial layer can be added as an outer layer to prevent abrasion from wearing away the. nylon jacket or the IR reflecting jacket. The sacrificial layer can be an IR transmitting layer, or it can be an IR reflective layer. [059] The IR reflective layer can be applied to cables in ducts, buried cables and aerial high tension wires. [060] Figure 7 illustrates a further embodiment of the invention comprising an overhead cable with a multi-wire core 7.04 having an IR reflective coating 7.16. At present, for aesthetic reasons, it is C09386 6 usual to sand blast overhead HT wires to reduce the reflection therefrom. It is also known to paint such wires black. However, this causes additional heating of the overhead wires. According to an embodiment of the invention, IR reflecting coating can be applied to overhead wires. In this embodiment, the cable does not require electrical insulation or other layers in addition to the IR reflecting layer. the IR reflective layer can be designed to reduce reflection of visible light. The IR layer can be designed to disperse incident visible light. for example, the surface of the IR reflective layer can be rough. The IR reflective layer can have a dark colour. [061] In this specification, reference to a document, disclosure, or other publication or use is not an admission that the document, disclosure, publication or use forms part of the common general knowledge of the skilled worker in the field of this invention at the priority date of this specification, unless otherwise stated. [062] In this specification, terms indicating orientation or direction, such as "up", "down", "vertical", "horizontal", "left", "right" "upright", "transverse" etc. are not intended to be absolute terms unless the context requires or indicates otherwise. [063] Where ever it is used, the word "comprising" is to be understood in its "open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of". A corresponding meaning is to be attributed to the corresponding words "comprise", "comprised" and "comprises" where they appear. [064] It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text. All of these different combinations constitute various alternative aspects of the invention. [065] While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, and all modifications which would be obvious to those skilled in the art are therefore intended to be embraced therein.

Claims (12)

1. A cable having at least one inner electrical conductor , and an insulating jacket, wherein the insulation jacket constitutes or is enclosed in an IR reflecting layer adapted to reflect incoming IR radiation, the IR reflecting layer incorporates one or more IR reflecting pigments.

2. A cable as claimed in claim 1, wherein the insulating jacket incorporates or consists of the IR reflecting layer.

3. A cable as claimed in claim 1, includeing an IR reflecting layer applied over the insulating jacket .

4. A cable as claimed in any one of the preceding claims, wherein the IR reflecting layer is the external layer.

5. A cable as claimed in any one of the preceding claims, wherein the electrically insulating jacket is applied over the electrically conducting core, the IR reflecting layer is applied over the electrically insulating layer, and an outer skin is applied over the IR reflecting layer.

6. A cable as claimed in claim 5, wherein the outer skin is abrasion resistant.

7. A cable as claimed in claim 5 or claim 6, wherein the outer skin is substantially transparent to IR radiation.

8. A cable as claimed in claim 7, wherein the IR transparent layer includes perylene.

9. A cable as claimed in claim 1, wherein the IR reflecting pigments are mixed metal oxides.

10. A cable as claimed in claim 9, wherein the pigments include one or more of the oxides of titanium, iron, and cobalt.

11. A cable as claimed in any one of claims 1 to 10, wherein the cable is an overhead high voltage cable .

12. A cable as claimed in claim 11 wherein the IR reflective layer disperses incident visible light.