Technical field

[0001 ] The present invention relates generally to wires and cables for electrical transmission. Specifically, the present invention relates to cables and wires for power transmission.

Background art

[0002] Transmission of electricity is vital to society today. Wherever we look, we find cables of all shapes and sizes, from the thin wires in our headphones, to the cables running underground to supply us with electricity. Constantly improving the functionality of cables is vital, to keep up with an increasing population, growing cities, and a transition to an electrified society as a step to impede climate change.

[0003] Providing more cost-efficient cables will be central in the electrified society to which we are headed. Furthermore, lower cost increases the availability to emerging technologies. A high availability means that more people can adapt to more environmentally friendly lifestyles and is furthermore a matter of equality.

[0004] The weight is also a central property for cables and wires. For example, weight greatly affects transportation costs and greenhouse gas (GHG) emissions, wherein a lighter cable may be transported at a lower cost and with a reduced GHG footprint. A lower weight naturally effects both transportation of cables preinstallation, as well as cables in transportation means such as cars, ships, trains and airplanes. Furthermore, heavy cables are a hazard to the people which are tasked with the installation, specifically relating to airborne cables.

[0005] One way to both decrease cost and weight of cables is the use of alternative materials. However, research projects regarding new materials for electrical transmission often focus on, and result in, expensive, specialized materials.

[0006] Aluminum is a material which is often overlooked as a suitable material for cables because aluminum has a lower conductivity and higher resistivity than for example copper, gold and silver. Specifically, the higher impedance of aluminum is seen as an obstacle to its use in cables. However, aluminum is less expensive, and furthermore lighter than for example copper.

[0007] For example in the SIS standard IEC60228, acceptable values of the impedance of cables for electrical transmission are defined. There is therefore a need for a light and cost efficient wire which provides an impedance satisfying this or comparable standards.

[0008] Therefore, there is a need for improved wires and cables which are lower in cost, have lower weight, and still maintains high quality and does not negatively affect people or the environment.

Summary of invention

[0009] An object of the present invention is to overcome at least some of the above discussed problems.

[0010] In a first aspect of the disclosure there is provided a wire for electrical transmission comprising a core comprising at least one metal strand formed by a first metal, and a surrounding layer comprising a plurality of surrounding metal strands formed by a second metal, the surrounding metal strands being twisted around the core, wherein one of the first and second metal is aluminum and the other is copper, and wherein 20 - 55 volume percent of the wire is aluminum, and the rest is copper.

[0011 ] The disclosure is based on the insight that a wire comprising both aluminum and copper, wherein one metal is arranged in the core and the other surrounding the core, provides improved properties relating to for example weight, cost, flexibility. Furthermore, the general view in the cable business is that an increased amount of aluminum would decrease properties such as the electrical impedance, and thus such high levels of aluminum are not utilized today.

However, according to the present disclosure there is provided a wire which utilizes a higher share of aluminum than what is commonly utilized in the business, which does not display levels of the electrical impedance above acceptable levels. [0012] In one embodiment, 25 - 55 volume percent of the wire is aluminum, and the rest is copper.

[0013] In one embodiment, 35 - 55 volume percent, more preferably 40 - 55 volume percent, even more preferably 40 - 50 volume percent of the wire is aluminum, and the rest is copper.

[0014] In one embodiment, 20 - 40 volume percent, more preferably 25 - 40 volume percent, even more preferably 25 - 35 volume percent of the wire is aluminum, and the rest is copper.

[0015] In one embodiment, 20 - 45 volume percent, more preferably 25 - 45 volume percent, even more preferably 35 - 45 volume percent of the wire is aluminum, and the rest is copper.

[0016] In one embodiment, the first metal is aluminum, and the second metal is copper.

[0017] In one embodiment, the first metal is copper, and the second metal is aluminum.

[0018] In one embodiment, the aluminum is annealed aluminum.

[0019] In a second aspect of the disclosure there is provided a cable for electrical transmission, comprising at least one wire, and at least one cable component chose from a filler, a braid and a jacket, wherein the at least one wire is a wire according to the present disclosure.

[0020] In one embodiment, the cable is a power cable for electric power transmission, wherein the cable comprises two wires.

[0021 ] In one embodiment, the cable is a power cable for electric power transmission, wherein the cable comprises three wires.

[0022] In one embodiment, the cable is a power cable for electric power transmission, wherein the cable comprises four wires. [0023] In one embodiment, the cable is a power cable for electric power transmission, wherein the cable comprises five wires.

[0024] In a third aspect of the disclosure there is provided a method for producing a wire for electrical transmission, wherein the wire comprises a core comprising at least one metal strand formed by a first metal, and a plurality of surrounding metal strands formed by a second metal, wherein one of the first and second metal is aluminum and the other is copper, the method comprising; providing at least one strand formed by a first metal, assembling the core from the provided at least one metal strand, providing the plurality of surrounding metal strands, twisting the plurality of surrounding metal strands around the core to form a surrounding layer, wherein the core and the plurality of surrounding metal strands are provided such that a total volume of the wire comprises 20 - 55 volume percent aluminum, and the rest is copper.

[0025] In one embodiment, 25 - 55 volume percent of the wire is aluminum, and the rest is copper.

[0026] In one embodiment, 35 - 55 volume percent, more preferably 40 - 55 volume percent, even more preferably 40 - 50 volume percent of the wire is aluminum, and the rest is copper.

[0027] In one embodiment, 20 - 40 volume percent, more preferably 25 - 40 volume percent, even more preferably 25 - 35 volume percent of the wire is aluminum, and the rest is copper.

[0028] In one embodiment, 20 - 45 volume percent, more preferably 25 - 45 volume percent, even more preferably 35 - 45 volume percent of the wire is aluminum, and the rest is copper.

[0029] In a fourth aspect of the disclosure, there is provided a method for producing a cable, comprising providing at least one first wire produced by to the method according to the present disclosure, providing at least one cable component chosen from a filler, a shield and a braid, assembling the at least one first wire and the at least one cable component into a cable. The method may further comprise providing at least one second wire produced by to the method according to the present disclosure.

Brief description of drawings

[0030] The invention is now described, by way of example, with reference to the accompanying drawings, in which:

[0031 ] Figs. 1 a-1 b display embodiments of a wire comprising a stranded core.

[0032] Fig. 2 displays an embodiment of a wire comprising a solid core.

[0033] Fig. 3 displays the bending radius of a wire.

[0034] Figs. 4a-4b display embodiments of a cable comprising two and three wires, respectively.

[0035] Fig. 5 displays a method for producing a wire according to the present disclosure.

Definition of terms

[0036] The following terms are used in the present disclosure, and are defined below only to increase understanding and transparency, and should not be considered limiting to the scope of the protection as defined by the appended claims.

Strand: A single thread of metal through which electricity is conducted.

Wire: One or a plurality of strands. Also known as a conductor.

Solid wire: A wire only comprising one strand, optionally comprising a surrounding insulation.

Stranded wire: A wire comprising a plurality of strands, optionally comprising a surrounding insulation. The plurality of strands may or may not be twisted around each other. Cable: A plurality of wires, wherein each wire may or may not be insulated. A cable commonly comprises additional components such as fillers and a surrounding jacket for protection.

Description of embodiments

[0037] In the following, a detailed description of wires, cables and methods according to the disclosure are provided. In the figures, dashed lines are provided to more clearly distinguish between components of the wire and are provided for understanding only. However, in some embodiments, additional components such as insulation may be provided at positions corresponding to the dashed lines in the figures.

[0038] With reference to Figs. 1a and 1 b, there is displayed embodiments of a wire 100 for electrical transmission comprising a core 110 and a surrounding layer 120 of conducting strands. The surrounding layer 120 is preferably twisted around the core 110.

[0039] In Figs. 1 a and 1 b, the core 110 comprises a plurality of strands of a first metal. The core 110 may be twisted, such that the strands of the first metal are arranged twisted around each other. The core 110 may also be straight, such that the strands of the first metal are arranged parallel to each other. The surrounding layer 120 comprises a plurality of strands of a second metal. In Fig. 1a, the surrounding layer 120 is a single layer. In Fig. 1b the surrounding layer 120 comprises two layers. In alternative embodiments, the surrounding layer 120 may comprise a plurality of layers of the second metal.

[0040] With reference to Fig. 2 there is displayed an embodiment of wire 200 for electrical transmission. The wire 200 comprises a core 210 comprising one single strand of the first metal. The wire 200 furthermore comprises surrounding layer 220 comprising a plurality of strands of a second metal. The plurality of strands in the surrounding layer 220 may be any number of strands. The surrounding layer 220 may be arranged in one or a plurality of layers of metal strands of the second metal. [0041] Both the first and second metal are preferably high purity metals. High purity metals are herein defined as metals having a composition comprising at least 95% of one metal, wherein the balance may be alloying elements or impurities. Having high purity metals increases conductivity, decreases resistivity and provides good contact between adjacent strands, if they are uncoated.

[0042] In a first embodiment of the present disclosure the first metal is aluminum. When reference is made to aluminum, this should be understood as high purity aluminum. High purity aluminum preferably comprises at least 95 % aluminum, even more preferably at least 99 % aluminum. In this embodiment, the second metal is copper. When reference is made to copper, this should be understood as high purity copper. High purity copper preferably comprises at least 95 % copper, even more preferably at least 99% copper.

[0043] In a second embodiment of the present disclosure the first metal is copper. When reference is made to copper, this should be understood as high purity copper. High purity copper preferably comprises at least 95 % copper, even more preferably at least 99% copper. In this embodiment, the second metal is aluminum. When reference is made to aluminum, this should be understood as high purity aluminum. High purity aluminum preferably comprises at least 95 % aluminum, even more preferably at least 99 % aluminum.

[0044] Having a suitable relation between the amount of copper and the amount of aluminum in the wire is central in order to achieve desired levels of properties such as flexibility, weight and cost, without deviating from desired levels of performance properties such as electrical impedance. In the present disclosure, the relation between the amount of aluminum and the amount of copper in the wire is defined as the volume relation between the first metal and the second metal. For a given length, the relation between the amount of aluminum and the amount of copper in the wire may thus be defined as a relation between a measured volume percentage of the core and a measured volume percentage of the surrounding layer of the wire. In the present disclosure, the sum of the volume percentage of the core and the volume percentage of the surrounding layer substantially equals 100%. As an example, if the core constitutes 30 volume% of the wire, and the first metal is aluminum, this gives that the wire comprises 30 volume% aluminum.

[0045] In one embodiment the wire comprises 20-55 volume% aluminum and the rest is copper. In one embodiment the wire comprises 25-55 volume% aluminum and the rest is copper. In one embodiment the wire comprises 35-55 volume% aluminum, more preferably 40-55 volume% aluminum, even more preferably 40-50 volume% aluminum and the rest is copper. In one embodiment the wire comprises 20-40 volume% aluminum, more preferably 25-40 volume% aluminum, even more preferably 25-35 volume% aluminum, and the rest is copper. In one embodiment the wire comprises 20-45 volume% aluminum, more preferably 25-45 volume% aluminum, even more preferably 35-45 volume% aluminum, and the rest is copper. The disclosed ranges are provided regardless of whether the aluminum is provided as the first or second metal.

[0046] With reference to Fig. 3, the flexibility of the wire 100;200 may be defined as the bending radius R of the wire 100;200, wherein a larger bending radius R corresponds to a less flexible material. The bending radius R of a wire 100;200 is commonly defined in terms of the diameter D of the wire 100;200. For example, a given wire 100;200 has a diameter of 3 mm and the achieved bending radius of said wire 100;200 is 15 mm, this gives that the bending radius R is five times the diameter of the wire 100;200, the value of the flexibility of said wire 100;200 is thus commonly given as “x5”. In an embodiment of the present disclosure the aluminum is annealed aluminum. Annealed aluminum is provided by heat treating aluminum in order to increase the ductility of the aluminum. Using annealed aluminum increases the flexibility of the wire 100;200. In certain applications today, cables are required which comprise wires 100;200 formed by annealed copper, sometimes known as class 5 copper or class 6 copper. According to the present disclosure there is provided wires 100;200 comprising annealed aluminum, with comparable flexibility to conventional wires 100;200 produced by annealed copper.

[0047] The dimension of a wire 100;200, defined herein as the cross-sectional area of the wire 100;200, may be any one of the dimensions 2.5 mm ² , 6 mm ² , 10 mm ² , 16 mm ² , 25 mm ² , 35 mm ² , 50 mm ² , 70 mm ² , 95 mm ² , 120 mm ² , 150 mm ² . Preferably, the dimension is one of 2.5 mm ² , 6 mm ² , 10 mm ² , 16 mm ² , 25 mm ² , 35 mm ² , 50 mm ² , 70 mm ² , 95 mm ² . More preferably the dimension is one of 6 mm ² , 10 mm ² , 16 mm ² , 25 mm ² , 35 mm ² , 50 mm ² . Even more preferably the dimension is one of 10 mm ² , 16 mm ² , 25 mm ² , 35 mm ² .

[0048] With reference to Figs. 4a and 4b, there is also provided a cable 300 for electrical transmission. The cable 300 comprises at least one wire 100;200. Preferably, the cable 300 comprises two wires 100;200, three wires 100;200, four wires 100;200 or five wires 100;200. The cable 300 furthermore optionally comprises a plurality of additional components depending on the intended use of the cable 300. The cable 300 may for example comprise a filler 310. A filler 310 may be used between separate wires 100;200 in order to provide a substantially circular cross-section of the cable 300. A filler 310 may be any material, for example polymer, cotton, Kevlar or other. The cable 300 may furthermore comprise a braid 320 surrounding the length of the cable 300 to shield the cable 300. The braid 320 may for example decrease the electromagnetic radiation from the cable 300. The braid 320 may function as earth. An additional conductor may be provided as earth, which is known as an earth wire. The cable 300 may furthermore comprise a jacket 330, surrounding the length of the cable 300 for protecting the cable 300. Furthermore, each wire 100;200 may be provided with an insulation 340 surrounding the length of the wire 100;200.

[0049] With reference to Fig. 4a, there is provided a cable 300 comprising two wires 100;200. The two wires 100;200 may be substantially identical. Alternatively, the two wires 100;200 may be different such that they for example comprise a different number of strands in the core and/or a different number of strands in the surrounding layer and/or the surrounding layer of each wire 100;200 comprises a different number of layers or another feature may be different between the individual wires 100;200.

[0050] In another embodiment of the present disclosure displayed in Fig. 4b, the cable 300 comprises three wires 100;200. The three wires 100;200 may be different or substantially identical. [0051] The lay length is a term which defines the distance required to complete one revolution of a wire 100;200 when it is twisted together with at least one additional wire 100;200 to form a cable. Surprisingly, it has been discovered that the lay length highly affects properties of the wire 100;200 such as the electromagnetic field radiated from the wire 100;200. Specifically, a shorter lay length provides that the electromagnetic field radiated from the wire 100;200 is decreased, compared to a wire 100;200 having a longer lay length.

[0052] With reference to Fig. 5, there is also provided a method 400 for producing a wire. The method 400 generally comprises providing S1 at least one metal strand formed by a first metal, assembling S2 a core comprising the at least one metal strand, providing S3 a plurality of metal strands formed by a second metal and twisting S4 the plurality of metal strands around the core to form a surrounding layer. Preferably, the surrounding layer is twisted around the core such that the core is completely covered.

[0053] Preferably, one of the first and second metal is copper, and the other is aluminum. In one embodiment, the first metal is aluminum and the second metal is copper. In one embodiment the first metal is copper and the second is aluminum. In one embodiment, the aluminum is annealed aluminum.

[0054] The steps of providing S1 the at least one metal strand formed by the first metal and providing S3 the plurality of metal strands formed by the second metal are carried out such that the resulting wire comprises a desired volume ratio of the at least one metal strand formed by the first metal and the plurality of metal strands formed by the second metal. In the present disclosure, the desired volume ratio is 20-55 volume% aluminum and the rest is copper. In one embodiment the wire comprises 25-55 volume% aluminum and the rest is copper. In one embodiment the wire comprises 35-55 volume% aluminum, more preferably 40-55 volume% aluminum, even more preferably 40-50 volume% aluminum and the rest is copper. In one embodiment the wire comprises 20-40 volume% aluminum, more preferably 25-40 volume% aluminum, even more preferably 25-35 volume% aluminum, and the rest is copper. In one embodiment the wire comprises 20-45 volume% aluminum, more preferably 25-45 volume% aluminum, even more preferably 35-45 volume% aluminum, and the rest is copper. The disclosed ranges are provided regardless of whether the aluminum is provided as the first or second metal.

[0055] There is also provided a method for producing a cable according to the present disclosure. The method comprises providing at least one first wire produced according to the disclosed method for producing a wire, and assembling said wire with at least one additional component chosen from a filler, a shield, a braid. The method of producing a cable may furthermore comprise arranging at least one second wire produced according to the disclosed method for producing a wire together with the at least one first wire.

[0056] Preferred embodiments of a wire, a cable and methods have been described. Although the description above contains a plurality of specificities, these should not be construed as limiting the scope of the concept described herein but as merely providing illustrations of some exemplifying embodiments of the described concept. It will be appreciated that the scope of the presently described concept fully encompasses other embodiments which may become obvious to those skilled in the art and that the scope of the presently described concept is accordingly not to be limited. Reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more." All structural and functional equivalents to the elements of the above-described embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed hereby. Moreover, it is not necessary for an apparatus or method to address each and every problem sought to be solved by the presently described concept, for it to be encompassed hereby.