WO2015139737A1

WO2015139737A1 - A method for manufacturing a high-power cable

Info

Publication number: WO2015139737A1
Application number: PCT/EP2014/055401
Authority: WO
Inventors: Marc Jeroense; Henrik Hillborg
Original assignee: Abb Technology Ltd
Priority date: 2014-03-18
Filing date: 2014-03-18
Publication date: 2015-09-24

Abstract

The disclosure relates to a method 30 for manufacturing a high-power cable 20. The method 30 comprises providing 1a, 1b, 1c, 1d a synthetic conductor comprising carbon 4, and preparing 13 the synthetic conductor comprising carbon 4 with one or more layers, providing the high-power cable 20. A high-power cable 20 obtainable by the method is also provided.

Description

A method for manufacturing a high-power cable Technical field

The technology disclosed herein relates generally to the field of high-power cables, and in particular to methods for manufacturing of such power cables.

Background

A high-power cable should ideally fulfil a number of requirements. The power cable should of course first and foremost enable transmission of as large amounts of energy as possible in as efficient manner as possible. The power cable should also, besides having such high power transport capability allowing the efficient energy

transmission, provide high mechanical strength. The mechanical strength is required e.g. since the power cable should be usable for many years and sometimes in difficult environments. The high-power cable of today comprises a metal conductor and is thus heavy, and the weight of the power cable is an aggravating circumstance rendering both manufacturing and subsequent installation difficult, the weight thus being another aspect.

One way to improve on the above aspects could be to examine alternative conductor materials. There has lately been an increasing interest directed towards using carbon based materials and it has been envisaged to use it as conductor material in electrical wires, for example within the area of electronics. A carbon nanotube electrical wire is known, that is used as signal cable, i.e. at low voltages. Although functioning satisfactory at such low voltage application, it would have too high losses at higher currents, i.e. the conductivity at higher currents would be too poor.

Graphene, which is such a carbon based material, has a structure of a single molecular sheet of bonded carbon atoms which are packed in a sheet-like crystal lattice. Due to its unique two dimensional structures, graphene differs from most conventional three dimensional counterparts: it has high electron mobility at room temperature, high transparency in the spectra visible for the human eye, excellent thermal properties, high chemical stability, large surface area and it is mechanically strong. Recent application driven research evaluates graphene in various fields such as electronics, chemical sensors, electrode material and batteries. It has also been envisaged that graphene could be used as conductor material in electrical wires. Owing to the properties of the graphene, it could be an interesting alternative to use graphene as conductor material in high-power cables. However, the graphene is difficult to handle properly, so as to maintain the desired high conductivity. For instance, even though the conductivity within each individual graphene sheet is high, the contact resistance between the sheets leads to a significant reduction in

conductivity. There are thus various aspects that need to be considered when trying to replace the metal conductors of the high-power cables with conductors comprising carbon-based materials.

From the above it follows that the manufacturing processes of power cables also need consideration, in order to give the power cables the required and desired

characteristics, preferably using a cost efficient manufacturing process.

Summary

An object of the present disclosure is to solve or at least alleviate at least one of the above mentioned problems. It is a particular object of the present disclosure to incorporate in a manufacturing process of high-power cables, conductors of carbon based materials.

The object is according to a first aspect achieved by a method for manufacturing a high-power cable. The method comprises providing a synthetic conductor comprising carbon, and preparing the synthetic conductor comprising carbon with one or more layers, providing the high-power cable.

In contrast to manufacturing of conventional power cables, the method for

manufacturing of a synthetic conductor comprising carbon does not require as costly and difficult preparation measures, e.g. owing to its reduced weight compared to conventional metal conductors. The method for manufacturing may use at least parts of an existing factory line for manufacturing power cables, such as for example the cooling and extrusion steps whereby additional layers are provided.

In an embodiment, the providing comprises extruding a polymer comprising carbon, thereby providing a synthetic conductor comprising carbon.

In a variation of the above embodiment, the method comprises applying an electric or magnetic field to the polymer comprising carbon during the extruding and while being in a molten state. This ensures alignment of e.g. graphene sheets if used as the carbon.

In an embodiment, the providing comprises passing a number of synthetic fiber wires through a solution comprising carbon nanotubes and/or graphene sheets, and twisting the synthetic fiber wires, providing a stranded synthetic conductor comprising carbon.

In a variation of the above embodiment, the method comprises applying an electric or magnetic field over the synthetic fiber wires and/or the solution when passing the synthetic fiber wires through the solution.

In variations of the above two embodiments, the method comprises repeating the passing of the synthetic fiber wires through the solution, with intermediate washing and drying steps.

In a variation of the above embodiment, the method comprises extruding the stranded synthetic conductor comprising carbon with an electrically conducting or semi-conducting polymer material, providing the c synthetic conductor comprising carbon having a surrounding conducting or semi-conducting layer.

In an embodiment, the providing comprises twisting a number of carbon nanotube strands.

In an embodiment, the providing comprises covering individual polymer threads or stranded polymer threads with a carbon-based material.

In a variation of the above embodiment, the covering comprises depositing a carbon- based material on the individual polymer threads or stranded polymer threads in a chemical vapor deposition process or an electrostatic deposition method.

In a variation of the above embodiment, the method comprises extruding the covered polymer threads or stranded polymer threads with an electrically conducting or semiconducting polymer material, providing the synthetic conductor comprising carbon having a surrounding conducting or semi-conducting layer.

In an embodiment, the preparing of the synthetic conductor comprising carbon comprises: cooling the synthetic conductor comprising carbon, and extruding the synthetic conductor comprising carbon with an electrically insulating polymer or with an electrically conducting or semiconducting polymer.

In a variation of the above embodiment, the method comprises repeating the cooling and extruding providing a high-power cable comprising one or more of an outer conductive shield, an outer jacket, a layer of metal armoring.

In an embodiment, the preparing comprises providing one or more layers of: an inner conductive shield, an electrically insulating layer, an outer conductive shield, an outer jacket, a layer of metal armoring.

In an embodiment, the method comprises performing a crosslinking process on the synthetic conductor comprising carbon.

The object is according to a second aspect achieved by high -power cable obtainable by any embodiment of the method as above.

The object is according to a third aspect achieved by high-power cable for power ratings over 80 kV. The high-power cable comprises a synthetic conductor

comprising carbon, and one or more layers of: an inner electrically conducting or semiconducting layer, an electrically insulating layer, an outer electrically semiconducting or conducting layer, a metal armoring layer, and an outer jacket.

In an embodiment, the synthetic conductor comprising carbon comprises an extruded synthetic conductor comprising carbon, or a number of synthetic fiber wires covered with carbon nanotubes and/or graphene sheets or a number of polymer threads or stranded polymer threads covered with a carbon-based material, or a number of twisted carbon-based fiber wires.

Further features and advantages of the present teachings will become clear upon reading the following description and the accompanying drawings.

Brief description of the drawings

Figures 1, 2, 3 and 4 illustrate different embodiments of providing a synthetic conductor comprising carbon.

Figure 5 illustrates a manufacturing process of a high-power cable. Figure 6 illustrates a high-power cable resulting from the manufacturing process of figures 1-5.

Figure 7 is a flow chart illustrating a method according to the present disclosure. Detailed description

In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular architectures, interfaces, techniques, etc. in order to provide a thorough understanding. In other instances, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description with unnecessary detail. Same reference numerals refer to same or similar elements throughout the description.

Figures 1, 2, 3 and 4 illustrate schematically different embodiments of a first part of a high-power cable manufacturing process according to an aspect of the present disclosure. The first part of the manufacturing process comprises providing la, lb, ic, id a synthetic conductor comprising carbon 4. This first part may be done in different ways, as illustrated in figures 1, 2, 3 and 4, and may comprise a number of sub-steps.

Figure 1 illustrates a first embodiment of providing la a synthetic conductor comprising carbon 4. A number of synthetic fiber wires 2 may be passed through a solution comprising the carbon nanotubes and/or graphene sheets, which then adhere to the surfaces of the synthetic fibers. Such step is illustrated schematically at reference numeral 3. In order to maximize the conductivity of the resulting

conductor, it is desirable to align the graphene sheets along the synthetic fiber surfaces. Such alignment may be achieved by utilizing an electric or magnetic field. That is, in the process step 3, a magnetic field may be applied to the synthetic fiber wires 2, or over the solution bath through which the synthetic fiber wires 2 are passed, whereby the graphene sheets are aligned along the synthetic fiber wires, thus reducing contact resistance and increasing electrical conductivity. The synthetic fiber wires 2 may for example comprise carbon nanotube wires or strands or synthetic- fibers such as e.g., polymer fibers, thermoplastic fibers (such as for example aramid fibers), glass fibers,basalt fibers or carbon fibers (extremely strong thin fibers made by pyrolyzing synthetic fibers, such as rayon, until charred). Multiple layers may be provided by repeatedly passing the synthetic fiber wires 2 through the solution, combined with intermediate washing and drying steps.

The synthetic fiber wires 2 are then twisted, this twisting being illustrated

schematically at reference numeral 7. In this embodiment, the providing la thus begins with the preparing 3 of the synthetic fiber wires 2 and then twisting 7 them, whereby a stranded synthetic conductor comprising carbon 4 is obtained.

After steps 3 and 7 twisted synthetic fiber wires 2 embedded with carbon nanotubes and/or graphene sheets is obtained. The number of synthetic fiber wires 2 may be, e.g. in the range of hundreds to thousands, obtaining a total cross section of the synthetic conductor comprising carbon 4, higher than for example approximately 600 mm², or even larger e.g. 2000 mm² and higher. A cross section about such first mentioned exemplary size would provide a conductor able to withstand e.g. 80 kV or higher (the latter mentioned example providing a conductor able to withstand about 320 kV).

The synthetic conductor comprising carbon 4, possibly with carbon nanotubes and/or graphene sheets, may then be fed into an extruder, wherein it is extruded 5a with an electrically conducting or semi-conducting polymer material. Examples of such polymer material comprise cross linked polyethylene (PEX), polyethylene (PE), polypropylene (PP), PP-PE copolymers, polyethylene-co-butylacrylate, silicone rubber, ethylene propylene diene monomer (EPDM) and ethylene-propylene-rubber (EPR). The polymer matrix is filled with conductive fillers, such as carbon black, carbon nanotubes or graphene.

From the extruder, the synthetic conductor comprising carbon 4 having a

surrounding electrically conducting or semiconducting layer is then ready for a next process step. The extrusion 5a with the electrically conducting or semi-conducting polymer material is performed in order to smooth out the stranded synthetic conductor comprising carbon 4 so as to be able to control the electrical fields around it. A synthetic conductor comprising carbon, having a surrounding conducting or semi-conducting layer 6 is thus provided. The surrounding conducting or semiconducting layer provides a smooth bedding for the next layer, which typically is an insulating layer. The extrusion 5a may be compared to the extrusion performed in conventional high-power manufacturing, wherein an inner electrically conducting or semiconducting ("inner semicon") layer is provided surrounding the metal

conductor.

It is noted that the synthetic conductor comprising carbon 4 may be provided with e.g. two layers simultaneously, i.e. in a co-extrusion step. As a particular example, the synthetic conductor comprising carbon 4 may be provided with an inner semicon layer and an electrically insulating layer in a co-extrusion process.

The stranded synthetic conductor comprising carbon having a surrounding conducting or semi-conducting layer 6 may be provided with an insulating layer by another extrusion process (not illustrated). Such insulating layer may be cross-linked in order to give the resulting cable a higher mechanical strength. The crosslinking process is illustrated at reference numeral 15 and may for instance comprise adding a cross-linking agent in the extrusion process and use of elevated temperatures, ultraviolet (UV) electromagnetic radiation or infrared (IR) electromagnetic radiation.

Figure 2 illustrates a second embodiment of the providing lb of the synthetic conductor comprising carbon 4. In this embodiment, synthetic carbon-based fibers ("strands"), are used, such as e.g. carbon nanotube strands 2', which are twisted 3 into a single synthetic conductor comprising carbon 4. The twisting 3 may also comprise compressing the carbon nanotubes strands 2'.

In this second embodiment, one process step is eliminated compared to the first embodiment, but also compared to existing manufacturing methods that use stranded metal wires. In the first embodiment, as well as in the case of conventional stranded metal wires, the stranded conductor needs to be extruded with an

electrically conducting or semi-conducting material so as to smooth out the electrical fields, as mentioned earlier. That is, the conventional method requires extruding of the inner semi-conducting layer as a separate process step, while this is not required at all in the second embodiment lb. Owing to the very small diameter of each carbonnanotubes strands 2', the surface of the resulting synthetic conductor comprising carbon 4 will be smooth enough, so as to not require the electrically conducting or semi-conducting layer (inner semicon layer). This embodiment may thereby reduce manufacturing costs and manufacturing time. The stranded synthetic conductor comprising carbon 4 may thus be provided with an insulating layer by another extrusion process (not illustrated). As in the previous embodiment, such insulating layer may be cross-linked in order to give the resulting cable a higher mechanical strength. The crosslinking process may for instance, and as mentioned earlier, comprise adding a cross-linking agent in the extrusion process and use of elevated temperatures, UV electromagnetic radiation or IR

electromagnetic radiation.

Figure 3 illustrates a third embodiment of providing lc the synthetic conductor comprising carbon 4. In this embodiment, instead of the synthetic fiber wires 2 used in the previous two embodiments la, lb, individual polymer threads 14 or stranded polymer threads are covered with a carbon-based material, for example covered 8 with graphene. A synthetic conductor comprising carbon 4 is thus provided. The polymer threads 14 or stranded polymer threads may be covered 8 by the carbon- based material e.g. by deposition. Single sheets of graphene may be deposited on the polymer threads 14, for example in a chemical vapour deposition (CVD) process. In such case, care has to be taken in the selection of polymer and/or process conditions, such as not to deteriorate the selected carbon-based material or break the polymer threads 14. For example, the process parameters such as temperature and process speed should be set in view of e.g. the polymer threads 14 not breaking in the CVD process. In another embodiment, the polymer threads 14 may be deposited by an electrostatic deposition method, wherein the graphene is absorbed on a charged surface. Such deposition method does not require a high temperature and may be applied to many types of polymer threads 14. The result of this third embodiment of providing lc is again a synthetic conductor comprising carbon 4.

The synthetic conductor comprising carbon 4 may, but need not, next be extruded 5c in an extruder with an electrically conducting or semi-conducting polymer material. In correspondence with the previous embodiment, each individual polymer thread 14 has a small diameter, which provides a surface of the resulting synthetic conductor comprising carbon 4 that is smooth enough, so as to not require the electrically conducting or semi-conducting layer (inner semicon layer). However, if stranded polymer threads are used, such inner semicon layer may (depending on size thereof) be needed. A synthetic conductor comprising carbon thus results, having a

surrounding conducting or semi-conducting layer 6. As for the previous embodiments, an insulating layer may be extruded, which may also be cross-linked 14, as described earlier.

Figure 4 illustrates a fourth embodiment of providing id the synthetic conductor comprising carbon 4. In this embodiment, a polymer (in particular a synthetic polymer) filled with carbon material in some form, forming a percolated network, i.e. conductive fillers, e.g. graphene platelets and/or carbon black and/or carbon nanotubes is fed 9 into a first extruder. Alternatively, polymer pellets and e.g.

graphene powder are fed 9 together into the first extruder. Thus, in this fourth embodiment, the providing id comprises extruding 5d a polymer comprising carbon or a mixture of polymer and carbon material, whereby the synthetic conductor comprising carbon 4 is provided.

This embodiment, like the embodiment of figure 2, provides a synthetic conductor comprising carbon 4 that is smooth, and which does not require the electrically conducting or semi-conducting (inner semicon layer) to be provided. Also this embodiment may thereby reduce manufacturing costs and manufacturing time.

The embodiment of figure 4 requires a number of considerations. For example, if using graphene/polymer pellets, some synthetic fibers such as aramid ("aromatic polyamide") fibers, glass fibers or basalt may be needed in order to reinforce the mechanical strength of the resulting high-power cable. This reinforcement could alternatively be applied at a later stage, e.g. after providing of an outer conducting or semi-conducting layer (compare description in relation to figure 5).

Other additives may also have to be considered, such as surface treatments of the conductive fillers in order to avoid or at least minimize agglomeration, while still achieving a percolated network or conductive particles. Cross-linking additives, such as for example peroxides or silanes, may be added for enhancing thermal stability of the synthetic conductor comprising carbon 4.

Yet other considerations of the fourth embodiment of providing id comprise the importance of obtaining high conductivity of the synthetic conductor comprising carbon 4. It is therefore important to have high anisotropy. If for example using graphene as the carbon based material, then the graphene sheets need to be aligned so as to provide such anisotropic characteristics to the synthetic conductor

comprising carbon 4. To obtain this, i.e. to align the graphene sheets, one consideration may be to adapt the process parameters used during the extrusion so as to ensure a continuous flow without any turbulence. A few examples of such process parameters comprise the temperature and extrusion rate. Another way of ensuring alignment of the graphene sheets comprises applying an electric or magnetic field when the polymer is in its molten state.

In this embodiment, when performing the extruding 5d for providing the synthetic conductor comprising carbon 4, a cross-linking process 15 may be included. When providing the resulting synthetic conductor comprising carbon 4 with an insulating layer, also this layer may be cross-linked, in correspondence with earlier description.

An advantage of all four embodiments of providing la, lb, ic, id a synthetic conductor comprising carbon 4 is that a compact and void free all synthetic conductor is obtained. This is in contrast to the conventional manufacturing methods using metal wires that are stranded and extruded with a polymer. In such conventional

manufacturing there will unavoidably be gaps between the strands. In addition, this synthetic conductor has lower weight and higher flexibility, compared to the conventional metal conductors.

With reference now to figure 5, a remaining part 13 of the manufacturing process for manufacturing a high-power cable is described. The synthetic conductor comprising carbon 4 is now to be prepared with a number of layers, resulting in a high-power cable. The synthetic conductor comprising carbon 4 may first be cooled 10, e.g. in a water bath.

The synthetic conductor comprising carbon 4, if requiring an electrically conducting or semiconducting layer (in particular embodiments of figure 1 and 3), is now to be prepared so as to provide it with such electrically conducting or semiconducting layer. The synthetic conductor comprising carbon 4 may be provided with such layer by extruding 11 the synthetic conductor comprising carbon 4 with a conducting or semiconducting polymer. From this extrusion 11 then, a synthetic conductor comprising carbon with an electrically conducting or semi-conducting layer results.

The synthetic conductor comprising carbon 4, having been provided with an electrically conducting or semiconducting layer if required, may then be provided with an electrically insulating layer, which may be accomplished by extruding 11 the synthetic conductor comprising carbon 4 with an electrically insulating polymer material. Examples of such electrically insulating polymer material comprise linked polyethylene (PEX), polyethylene (PE), polypropylene (PP), PP-PE copolymers, silicone rubber, ethylene propylene diene monomer (EPDM) and ethylene-propylene- rubber (EPR). From this extrusion 11 then, a synthetic conductor comprising carbon 4 and also having an insulation layer results.

The above steps may then be repeated for each layer that is required in the particular high-power cable to be manufactured. For example, the synthetic conductor comprising carbon and having an insulation layer may be cooled, and then extruded with a thin layer of conductive polymer, e.g. a polymer filled with carbon black or graphene. Examples of polymers comprise cross-linked polyethylene (PEX), polyethylene (PE), polypropylene (PP), PP-PE copolymers, polyethylene-co-butyl acrylate, silicone rubber, ethylene propylene diene monomer (EPDM) and ethylene- propylene-rubber (EPR). The result is thus a synthetic conductor comprising carbon having an electrically conducting or semi-conducting layer, an insulation layer and an outer conductive layer. This outer conductive layer is comparable with an outer conductive shield ("outer semi-con") as used in conventional high-power cables.

Still further layers may be provided in a corresponding way, i.e. by cooling and extruding. The high-power cable may thus be provided with any required layers. For example, the high-power cable may be provided with one or more layer of: an inner conductive shield (as described), an electrically insulating layer (as described), an outer conductive shield (as described), a layer of metal armoring, and an outer jacket.

Figure 6 illustrates a high-power cable 20 resulting from the above described manufacturing process la, lb, IC, id, 13. The high-power cable 20 comprises the synthetic conductor comprising carbon 4, provided in any of the ways as described with reference to figures 1, 2, 3 and 4. The high-power cable 20 may, but need not, comprise an electrically conducting or semi-conducting layer 13 as has been described. Next, the high-power cable 20 may comprise an electrically insulating layer 16 surrounding the synthetic conductor comprising carbon 4. The illustrated high-power cable 20 may further comprises an outer electrically semi-conducting or conducting layer (not illustrated) which may have been extruded or co-extruded as described. The outer electrically semi-conducting or conducting layer 16 surrounds the electrically insulating layer 13 and thus also the synthetic conductor comprising carbon 4. Although not illustrated in the figure 6, the high-power cable 20 may comprise still further layers, as has been described earlier, e.g. metal armoring, outer jacket etc. The high -power cable 20 is suitable for various high current applications.

The synthetic conductor comprising carbon 6 having a surrounding conducting or semiconducting layer is an all synthetic conductor and has a much reduced weight compared to conventional high-power cables comprising a metal conductor. The step of wire twisting is, owing to the reduced weight, highly facilitated compared to the known power cable manufacturing. For example, in the manufacturing of the conventional metal conductor power cable, measures are required in order to keep the conductor straight. As a particular example, a stranded copper conductor may need to be extruded while being fed vertically (gravity fed) in order for the conductor to be correctly aligned within the extruded layer. Such vertical feeding requires towers of heights up to about hundred meters. In contrast to this conventional manufacturing, the stranded synthetic conductor does not require as costly and difficult preparation measures. Further, the synthetic conductor comprising carbon having a surrounding conducting or semiconducting layer has a high conductivity, which is an important characteristic of a power cable. Further, the carbon-based synthetic conductor comprising carbon having a surrounding conducting or semiconducting layer has a small bend radius which is advantageous e.g. in that it can be rolled on smaller rolls and transported more easily if needed. Further still, the power cable is provided with a high mechanical strength.

The method for manufacturing may use at least parts of an existing factory line for manufacturing power cables, such as for example the cooling and extrusion steps whereby additional layers are provided.

The various embodiments and features as have been described may be combined in various ways. Figure 7 is a flow chart illustrating a method 30 according to the present disclosure. The method 30 for manufacturing a high-power cable 20 comprises providing la, lb, lc, id a synthetic conductor comprising carbon 4 e.g. in accordance with any of the embodiments as described with reference to figure 1-4. The providing may thus comprise extruding a polymer comprising carbon, or passing a number of synthetic fiber wires 2 through a solution comprising carbon nanotubes and/or graphene sheets and then twisting the synthetic fiber wires, providing a stranded synthetic conductor comprising carbon, or twisting 7 a number of carbon nanotube strands 2', or covering 8 individual polymer threads 14 or stranded polymer threads with a carbon-based material, e.g. by a deposition method.

The method 30 further comprises preparing 13 the synthetic conductor comprising carbon 4 with one or more layers, providing the high-power cable 20. Such preparing 13 may comprise extruding additional layers such as electrically conducting or semiconducting layers, insulating layers etc., and intermediate steps such as cooling and drying.

In an aspect of the present disclosure, a high-power cable 20 is provided which is obtainable by the method according to any of the above described embodiments.

In an aspect of the present disclosure a high-power cable 20 for power ratings over 80 kV, is provided. The high-power cable 20 comprises a synthetic conductor comprising carbon 4 and one or more layers of: an inner electrically conducting or semiconducting layer 13, an electrically insulating layer 16, an outer electrically semiconducting or conducting layer, a metal armoring layer, and an outer jacket. Each of the layers may be cross-linked.

In an embodiment of the above high-power cable 20, the synthetic conductor comprising carbon 4 comprises an extruded synthetic conductor comprising carbon, or a number of synthetic fiber wires 2 covered with carbon nanotubes and/or graphene sheets or a number of polymer threads 14 or stranded polymer threads covered with a carbon-based material, or a number of twisted carbon nanotube strands 2'.

The invention has mainly been described herein with reference to a few

embodiments. However, as is appreciated by a person skilled in the art, other embodiments than the particular ones disclosed herein are equally possible within the scope of the invention, as defined by the appended patent claims.

Claims

1. A method (30) for manufacturing a high-power cable (20), the method (30) comprising:

- providing (la, lb, lc, id) a synthetic conductor comprising carbon (4), and

- preparing (13) the synthetic conductor comprising carbon (4) with one or more layers, providing the high-power cable (20).

2. The method (30) as claimed in claim 1, wherein the providing (id) comprises:

- extruding (sd) a polymer comprising carbon, thereby providing a synthetic conductor comprising carbon (4).

3. The method (30) as claimed in claim 2, comprising applying an electric or magnetic field to the polymer comprising carbon during the extruding (sd) and while being in a molten state.

4. The method (30) as claimed in claim 1, wherein the providing (la) comprises:

- passing (3) a number of synthetic fiber wires (2) through a solution comprising carbon nanotubes and/or graphene sheets, and

- twisting (7) the synthetic fiber wires (2), providing a stranded synthetic conductor comprising carbon (4).

5. The method (30) as claimed in claim 4, comprising applying an electric or magnetic field over the synthetic fiber wires (2) and/or the solution when passing (3) the synthetic fiber wires (2) through the solution.

6. The method (30) as claimed in claim 4 or 5, comprising repeating the passing (3) of the synthetic fiber wires (2) through the solution, with intermediate washing and drying steps.

7. The method (30) as claimed in claim 4, 5 or 6, comprising extruding (5a) the stranded synthetic conductor comprising carbon (4) with an electrically conducting or semi-conducting polymer material, providing the synthetic conductor comprising carbon (4) having a surrounding conducting or semi-conducting layer.

8. The method (30) as claimed in claim 1, wherein the providing (lb) comprises twisting (7) a number of carbonnanotube strands (2').

9. The method (30) as claimed in claim 1, wherein the providing (lc) comprises:

- covering (8) individual polymer threads (14) or stranded polymer threads with a carbon-based material.

10. The method (30) as claimed in claim 9, wherein the covering (8) comprises depositing a carbon-based material on the individual polymer threads (14) or stranded polymer threads in a chemical vapor deposition process or an electrostatic deposition method.

11. The method (30) as claimed in claim 10, comprising extruding (5c) the covered polymer threads (14) or stranded polymer threads with an electrically conducting or semi-conducting polymer material, providing the synthetic conductor comprising carbon (4) having a surrounding conducting or semi-conducting layer.

12. The method (30) as claimed in any of the preceding claims, wherein the preparing (13) the synthetic conductor comprising carbon (4) comprises:

- cooling (10) the synthetic conductor comprising carbon (4), and

- extruding (11) the synthetic conductor comprising carbon (4) with an electrically insulating polymer or with an electrically conducting or semiconducting polymer.

13. The method (30) as claimed in claim 12, comprising repeating the cooling (10) and extruding (11) providing a high-power cable (20) comprising one or more of an outer conductive shield, an outer jacket, a layer of metal armoring.

14. The method (30) as claimed in any of the preceding claims, wherein the preparing (13) comprises providing one or more layer of: an inner conductive shield, an electrically insulating layer, an outer conductive shield, an outer jacket, a layer of metal armoring.

15. The method (30) as claimed in any of the preceding claims, comprising

performing a crosslinking process (14) on the synthetic conductor comprising carbon (4).

16. A high-power cable (20) obtainable by the method as claimed in any of the preceding claims.

17. A high-power cable (20) for power ratings over 80 kV, comprising:

- a synthetic conductor comprising carbon (4), and

- one or more layers of: an inner electrically conducting or semiconducting layer (13), an electrically insulating layer (16), an outer electrically semi-conducting or conducting layer, a metal armoring layer, and an outer jacket.

18. The high-power cable (20) as claimed in claim 17, wherein the synthetic conductor comprising carbon (4) comprises an extruded synthetic conductor comprising carbon, or a number of synthetic fiber wires (2) covered with carbon nanotubes and/or graphene sheets or a number of polymer threads (14) or stranded polymer threads covered with a carbon-based material, or a number of twisted carbon-based fiber wires (2').