In a first aspect the invention relates to a high voltage winding comprised in an electrical machine and comprising an insulated conductor. More specifically the invention according to this first aspect relates to a high voltage winding according to the preamble of claim 1. Specifically the invention relates to a high voltage winding comprising an insulated conductor, composed of a plurality of strands, which are electrically insulated from each other. For the purpose of this application "high voltage"means voltages up to the highest voltages being used for generation, transmission or distribution of electrical power.

In a second aspect the invention relates to a method in manufacture, mounting, service or other maintenance or repair work, for jointing such an insulated con- ductor, which is included in a high voltage winding and comprising a plurality of strands, which are electrically insulated from each other. The inventive method is fast, simple and reliable, and secures a good electrical contact between strands which are parts of the jointed conductors, and thereby a good electrical contacting in the joint.

A third aspect of the invention relates to an electrical machine comprising a high voltage winding having such a jointed, insulated conductor.

BACKGROUND OF THE INVENTION AND PRIOR ART Although the following description mainly relates to and exemplifies both prior art and the present invention by high voltage windings being part of electrical, rotating machines, and thereby in the first place high voltage stator windings, the present invention is applicable for essentially all types of electrical machines, also com- prising static machines such as transformers and reactors. In the present applica-

tion the expression"high voltage winding"means a winding which in use is at a voltage level of 20 to 800 kV, preferably a voltage level over 36 kV. Transformers and reactors comprising such high voltage windings are used for exchanging elec- trical energy between two or more systems, for transferring or distributing electrical power, and the high voltage windings are thereby used for electromagnetic induc- tion in ways known per se. Transformers and reactors having high voltage windings according to the present invention, are primarily intended to be used for power ratings from a few hundred kVA up to in excess of 1.000 MVA, and voltage ratings from a few kV up to the highest transmission voltages amounting to 400 to 800 kV or higher.

A high voltage winding for the voltage level in question, and arranged according to known techniques in a rotating machine, such as a generator, is composed of a number of insulated, rectangular copper wires. In a stator winding these wire strands are transposed, i. e. they change place with each other and are enclosed by a common insulation whereby wires and insulation are arranged such that the bundle of conductors obtain a rectangular cross section. Rectangular copper con- ductors are used since this brings about smaller eddy current losses. Such gen- erators have commonly been designed for voltages amounting to from 15 kV up to 30 kV, which normally has been regarded to be an upper limit. This has had as a consequence that the generator has been connected to the transmission network via a transformer, which has transformed the voltage up to the voltage used in the transmission network, commonly 130-400 kV. By arranging the high voltage winding so as to comprise an insulated conductor, as previously disclosed in the yet non-published international patent application PCT/SE97/00874, (said con- ductor below in this application being referred to as a high voltage cable), with an electrical insulation of the same type as that of the cables used for transmission of electrical power, it has been possible to increase the voltage of the machine to such levels that it has been possible to connect it directly to the power network used for the transmission, without intermediate transformer. Such a cable and its internal construction, manufacture and installation has been described in the previous, not yet published international applications PCT/SE97/00874, PCT/SE97/00877, PCT/SE97/00901, PCT/SE97/00902, PCT/SE97/00903. The cable includes a number of strands, often having a circular cross section and made of copper, alu- minium or other suitable metal or alloy, such as an alloy based on aluminium or copper. Preferably wires having a diameter below 4 mm have been used. These thin strands have been arranged to form a conductor surrounded by a first inner semi- conductive layer, an electrically insulating layer, preferably a layer comprising a cross-linked polyethylene composition and a second, outer, semiconductive layer.

Thus, a high voltage cable according to the present invention does not comprise the outer protective sheath surrounding and mechanically protecting a high voltage cable for use in power distribution, against e. g. abrasion and other damage. A high voltage cable according to the present invention neither exhibits any outer insulat- ing layer on the outside of the outer, semiconductive layer. A rotating electrical ma- chine having a high voltage winding comprising such a high voltage cable has been described in detail in the previous not yet published international patent applica- tions. The use of such high voltage cables presupposes that the machine has been adapted to these high voltage windings, i. a. the outer semiconductive layer has been grounded in the machine, at the same time as measures have been taken, such that the resistivity of this layer has been increased considerably, considering the risk for partial discharge and the function of the outer, semiconductive layer as a ground connection, in order to reduce the heat losses otherwise occurring as a consequence of eddy currents induced in the layer. Also the winding slots in which the high voltage cable is disposed, have been modified, preferably they have been made deeper in order to make place for a thicker insulation, which has led to other constructional changes in order to prevent the occurrence of natural resonance and to provide cooling. Introduction and fixation of the high voltage cable in the slots, as well as all mechanical wear in connection with the handling of this particular high voltage cable, lacking the outer protective sheath, and the outer insulation, has also required measures to be taken. The conductor must be introduced in the recess without damaging the outer semiconductive layer, still the ground connec- tion must be safe.

Also the strands and their connection with the inner semiconductive layer differs from common insulated high voltage cables, used for transmission of electrical power. In contrast to these transmission cables, the cable being a part of a high voltage winding is exposed to magnetic fields, inducing currents with accompany- ing losses. Therefore at least some of the strands in such cables are arranged to have an electrically insulating surface layer, or having an electrically insulating coating, such that all strands are electrically insulated from each other, but at the same time at least one strand in the layer in contact against the inner semicon- ductive layer has been arranged to be in electrical contact with the inner semicon- ductive layer. In this way it has been ensured that the inner semiconductive layer in operation has essentially the same potential as the strands, at the same time a uniform current distribution in the conductor has been ensured, and the eddy- current losses have been counteracted. This has preferably been achieved by using both insulated and uninsulated strands in the high voltage cable, arranged such that two uninsulated wires are not in electrical contact. The employed insulated

layers should be stable during manufacture, and installation of the high voltage cable, i. e. preferably at temperatures up to 220°C. The insulating layers should also be stable during use of the electrical machine. Suitable insulations comprise insulation-lacquers such as lacquers based on formaldehyde, polyesters, polyes- terimides, polyurethanes, polyamides, polyimides, polyamidimides, thermoset plastics, extruded thermoplastics, oxides, nitrides which could be generated or coated, silicates or other ceramic compounds, preferably applied by surface coating or deposition techniques known for the deposition of thin surface layers, and gen- erating thin layers exhibiting sufficient adhesion in combination with strength and compactness.

As mentioned above the high voltage cables, comprised in high voltage winding ac- cording to the present invention lack outer insulation and/or an outer protective sheath, the mechanical strain, and especially the abrasion of the outer semicon- ductive layer, must be minimise during manufacture, storage and installation.

Consequently it is obvious that a long high voltage cable cannot be pulled through the slots in its entire length when installating it in a winding, such as a stator winding. The high voltage winding can comprise up to 10 km high voltage cable.

Therefore the high voltage cable is subdivided in suitable pieces which thereafter are jointed. Thereby the number of joints will often be large. At the same time the strains experience will require that these joints exhibit a minimal influence on the electrical properties of the cable, whereby it must be ensured that all the strands being part of the high voltage cable are contacted. Peeling or similar mechanical methods for removing the insulation from insulated strands will thereby be to time- consuming to be economically interesting. Removal of the insulation by means of high temperature processes such as pyrolysis or burning, leaves residues that may influence both the mechanical connection and the electrical contacting. Use of chemical methods such as immersing in an etching or dissolving agent may also lead to residues of the insulation and/or the agent used remaining on the surfaces of the strands.

THE INVENTION An object with the present invention is to provide a high voltage winding including an easily applicable and reliable joint. The joint should be adapted to be applied with ease and reproducibly in connection with the manufacture, assembly or repair of an electrical machine, comprising such high voltage winding. This is achieved with a high voltage winding according to the preamble of claim 1, which is charac- terized by the features or the characterising part of claim 1. The present invention

also has as an object to provide a method for jointing an insulated conductor, in manufacture, assembly, service or other maintenance or repair work, said con- ductor being comprised in such a high voltage winding, and which comprises a plurality of strands which are electrically insulated from each other. This is achieved according the preamble of claim 14, which is characterized by the features of a characterising part of claim 14. In addition the present invention has as an object to provide an electrical machine comprising such a high voltage winding.

Such a machine is defined in claim 26. A high voltage winding for an electrical ma- chine comprises according to the present invention at least one jointed, multi- stranded, electrically insulated conductor, and is characterized in that the multi- stranded, insulated conductor comprises a core having a plurality of conductor wires, strands electrically insulated and a multi-layered conductor insulation which is provided around the composite, multi-stranded conductor-core, for electrical in- sulation of the conductor, whereby the conductor-insulation comprises an inner semiconductive layer which encloses the conductor-core, a layer of a solid insula- tion provided around the inner semiconductive layer, and a second, outer semicon- ductive layer provided on the outside of the solid insulation, all said strands being arranged in electrical with a contact with each other at the joint. Further embodi- ments of the aspect of the invention relating to a high voltage winding are charac- terized by the features according claims 2 to 13. Further developments relating to the inventive method are characterized by the features of claims 15 to 25.

An electrical machine having a high voltage winding, comprising a jointed, multi- stranded, electrically insulated cable, where the joint exhibits two partial conduc- tors in electrical contact and connected with each other, is in accordance with the present invention provided with a multi-wire, insulated cable. The cable comprises a conductor having a plurality of conductor wires (strands) electrically insulated from each other, strands and a multi-layered cable insulation arranged around the composite multi-wire conductor. The cable insulation comprises a first, inner semi- conductive layer enclosing the conductor, a layer of a solid insulation arranged around the inner semiconductive layer, and a second, outer semiconductive layer, enclosing the solid insulation, and wherein all strands of each cable core at the joint are arranged in electrical contact with each other. This is preferably achieved by one or both of the cable cores being arranged with a stable, electrically con- ducting connection, which is attached to the end surface of the cable core, such that the connection ties all strands comprising the cable cores together and electri- cally insulates the same. Alternatively this is achieved by establishing stable, elec- trical contact points between the strands.

According to one embodiment of the invention there is provided a stable, electrically conducting connection by applying a coherent, electrically conducting binder phase layer, such as a metallic solder to the end surface of the cable core. Preferably a soft solder is used, such as a soft solder based on silver. By the coherent electri- cally conducting binder phase layer which is applied to the end surface of the cable core, it is secured that the insulated strands are in electrical contact and tied to- gether. According to a preferred embodiment the electrically conducting binder phase layer is jointed with an electrically conducting body, attached to the end surface and to the layer, said body preferably being a part of a jointing sleeve pro- vided on a cable core.

According to an alternative embodiment the solid electrically conducting joint com- prises an electrically conducting body, which is provided and attached to the end surface of the cable core by means of friction welding, said body exhibiting an es- sentially metallic bonding to all end surfaces of the strands. Preferably the electri- cally conducting body constitutes a part of a jointing sleeve provided on a cable core.

Stable electrical contact points between the strands in the cable core has, accord- ing to one embodiment of the present invention, been established with a cable core which is inserted in a jointing sleeve, where insulated strands comprised in the ca- ble core after or in connection with the introduction have been deformed such that by the deformation, stable electrical contact points have been established between the strands and between the outer strands and the attached jointing sleeve. Pref- erably also the attached jointing sleeve has been deformed, e. g. by clamping it around the inserted cable core. In order to ensure that stable electrical contact points have been established, in accordance with an alternative embodiment, hard and sharp electrically conducting particles have been applied to the strands at the end of the cable core or have been introduced in the insulating layer. Preferably these hard and sharp electrically conducting particles comprise an electrically con- ducting ceramic such as nitride, or a carbide of titanium, suitably having been ap- plied to the insulation of the strands, dispersed in an electrically conducting con- tact grease. According to another alternative embodiment, at least a part of the ca- ble core which has been inserted into the sleeve, is twisted such that by the twist- ing, the strands in the twisted part have been deformed to such a degree that the strand insulation by deformation, fully or partly, has been removed, and such that the sleeve is compressed around the twisted conductor part. Of course it is possible to combine a twisted cable core and hard, electrically conducting particles in order to establish stable electrical contact points between all strands.

According to one embodiment the joint comprises a first cable core having been provided with a jointing sleeve. This jointing sleeve is provided, at the end surface of itself and of the cable core, with a pointed tip, which is run into an opposite sec- ond cable core when the joint has been established. This second cable core is thereby held together by a clamping means, such that the run in pointed tip of the jointing sleeve brings essentially all of the strands of this second cable core in elec- trical contact. Electrical contacting of all strands of the first cable cores against each other and against the jointing sleeve has been achieved in accordance with any of the previously described embodiments. After the jointing sleeve provided with a pointed tip has been attached and contacted, the tip of the contacted joint- ing sleeve has been run into the second cable core. The second cable core is clamped together with a clamping means, such that the run in tip of the jointing sleeve is electrically contacted with essentially all of the strands of the second cable core.

In order to joint a multi-wire electrically insulated cable at manufacture or repair of an electrical machine comprising a high voltage winding, by jointing and electrically contacting two cable cores of an insulating, multi-wire cable comprised in a high voltage winding according to the present invention, all conductor wires, strands, which are part of the joint, are arranged in stable electrical contact with each other, whereby it is ensured that the two cable cores are brought into electrical contact with each other. The multi-wire, insulated cable comprises a core with a plurality of from each other electrically insulated conductor wires, strands and a multi-layered cable insulation, arranged around the composite multi-wire conductor. The cable insulation comprises a first, inner, semiconductive layer enclosing the conductor, a layer of a solid insulation arranged around the inner semiconductive layer, and a second, outer semiconductive layer, enclosing the solid insulation.

According to a preferred embodiment of the inventive method an electrical con- ducting connection is attached against the end surface of the cable core, whereby all strands comprised in the cable core are tied together and are held in a stable electrical contact to each other. Preferably this is achieved by applying an electri- cally conducting binder phase, such as an electrically conducting metallic solder, onto the end surface of the multi-wire cable core. In order to lower the resistance over the joint, in certain cases an electrically conducting body is bonded with the end surface of the cable core by means of the binder phase. In order to achieve this the body is thereby attached against the end surface of the cable core, and is bonded with and brought into contact against the end surfaces of the strands, by

means of the applied binder phase layer, which suitably is constituted of a soft sol- der, such as one based on silver. Alternatively an electrically conducting body can be friction welded against the end surface of the cable core and bonded with and brought into contact with the end surfaces of the strands. Preferably the electrically conducting body is part of a jointing sleeve of an electrically conducting material, which in this way is bonded with and brought into contact with the end surfaces of the strands.

Alternatively a cable core is inserted into a jointing sleeve, whereupon the strands are deformed such that stable electrical contact points are established between the strands and between the outer strands and the sleeve. Preferably also the sleeve is deformed, suitably by clamping it around the cable core. In order to ensure that stable electrical contact points are established also in those cases where only a limited deformation is desirable or when for some reason, such as high ductility and adhesion of the insulating layer applied to the strands, the layer does not crack or is removed, and that thus no or only insufficient contact surfaces are ex- posed between strands, in accordance with one embodiment of the invention, hard, electrically conducting particles are applied to the electrically insulated strands before a cable core is introduced into the sleeve. These particles will already at a limited deformation penetrate a strand insulation whereby stable, electrical contact points are established between the strands and between the outer strands and the sleeve by means of the hard particles. A preferred and very suitable way of applying the particles is to disperse the particles in an electrically conducting contact grease, whereupon the contact grease, containing the dispersed particles is applied to the strands. Of course the particles can be applied in any other suitable way, such as dry spraying of the particles or by spraying, dipping etc., dispersed in a solvent. Particles can also already when insulating the strands have been intro- duced into the strand insulation, provided that it had been possible to combine this with the existing requirements of electrical insulation of the strands relative to each other.

According to one embodiment the strands and the strand insulation are deformed such that at least portions of insulation provided on a strand are removed, whereby contact surfaces occur between the strands of a cable core, by the cable core being twisted in a section at the end surface of the cable core, such that strands and strand insulation are deformed due to the twisting, whereby the strand insulation fully or partly is removed, whereupon the cable core is inserted into a sleeve. Sub- sequently the sleeve is compressed, and is pressing at least around the twisted section, and stable electrical contact points are established between the strands

and the outer strands and the sleeve in this twisted section. Of course the cable core can be twisted in the presence of hard particles such that, as has been de- scribed above, it is ensured that sufficient and sufficiently stable electrical contact points are established.

It is also suitable to use methods offering a quick removal of at least portions of insulation present on a strand, whereby contact surfaces occur on the strand in which it bears against on other strands, and which are essentially free form resi- dues of insulation, and any treatment medium. For example a cable core may be rapidly cooled such that the insulation becomes brittle and entirely or partly crackles, resulting in at least portions of the surfaces of the strands being exposed by flaking. This flaking can occur either in connection with the cryo treatment or in a subsequent deformation. Preferably the cryo treatment is performed by exposing the end of the cable core to a cooling air or gas stream, e. g. a stream of sub-cooled liquid such liquid nitrogen or dry ice, alternatively by the cooling effect occurring when a gas expands, the principle of Rank.

In one embodiment a first cable core is introduced and brought into contact against a jointing sleeve provided with a pointed tip. With a pointed tip is meant that the jointing sleeve comprises a protruding means of a suitable shape such that when it is run into a second cable core it provides electrical contact with all strands present in the second cable core, either directly or after this second cable core having been tightened around the run in pointed tip. Electrical contacting of all strands of the first cable core against each other and against the jointing sleeve is achieved in any of the ways previously described. After having applied and contacted the jointing sleeve provided with a pointed tip, said tip of a contacted jointing sleeve is run into a second cable core, whereby the second cable core, at the time of running in or thereafter, is clamped together with a clamping means, such that the tip of run in jointing sleeve is brought into contact with essentially all strands of the second ca- ble core.

The invention also relates to an electrical machine comprising a high voltage wind- ing. Preferably an electrical machine comprising a high voltage winding and which is adapted for generation, transmission or distribution of electrical power such a generator, a transformer, a reactor or machine, provided in a plant for production of electrical power, a plant for transmission of electrical power or in a network for distribution of electrical power form a producer to a consumer. The invention also relates to an electrical machine such as a motor, a transformer, a reactor or any

other machine located at a large consumer of electrical power, such as a larger in- dustrial plant.

FIGURES The invention will be explained in closer detail in the following and will be exempli- fied with a preferred embodiment with reference to the figures.

Figure 1 shows a cross section of a high voltage cable of the type being comprised in a high voltage winding according to the invention.

Figure 2a shows in detail a cable core, comprised in an embodiment of the inven- tion, arranged with a layer of an electrically insulating material applied to the end surfaces of the strands, according to one embodiment of the present invention, fig- ure 2b shows an alternative embodiment with an electrically conducting body at- tached to and brought into contact with the end surface of the strands by means of an electrically conducting binder phase.

Figure 3 shows a cable core comprised in an embodiment of the invention where an electrically conducting body has been friction welded against the end surfaces of the strands.

Figures 4a and 4b shows in detail two strands with an intermediate insulation comprised in an embodiment of the invention. A compound comprising hard elec- trically conducting particles has been applied to insulating layer in figure 4a, and as shown in figure 4b it has penetrated the insulating layers after deformation, such that stable electrical contact points have been established between the strands.

Figures Sa, 5b, 5c and 5d illustrates an embodiment of the present invention, com- prising a cable core with strands having been deformed by twisting. Stable electri- cal contact points have been established between the strand by the twisting.

Figure 6 shows in a longitudinal section through a jointed high voltage cable ac- cording to one embodiment of the invention, where a first cable core comprises a jointing sleeve having a pointed tip, run into a second cable core.

DESCRIPTION OF THE FIGURES The high voltage cable 10 shown in figure 1 comprises an electrical conductor which exhibits a plurality of conductor wires, strands 12. The strands 12 preferably exhibits a circular cross section, a diameter less than 4 mm and comprises an electrically conducting metal such as copper or aluminium, or an alloy based on such an electrically conducting metal. These strands 12 are arranged in the centre of the high voltage cable 10, surrounded by an insulating system which from the centre and outwards comprises a first inner semiconductive layer 14, a tubular insulating body 16 and a second, outer semiconductive layer 18.

In the embodiment shown in figure 1 the tubular insulating body 16 comprises an extruded and cross-linked polymer composition, such as a cross-linked polyethyl- ene composition. Also the two semiconductive layers are comprised of polymer lay- ers which have been co-extruded with the insulation, but which comprise a filler in the form of electrically conducting particles or an electrically conducting polymer, that is a polymer with intrinsic electrical conductivity. Preferably a particular filler is used, such as particles of soot, graphite or other electrically conducting modifi- cations of carbon, metals such as silver, copper, aluminium, nickel or an alloy comprising any of these or combinations of those, an electrically conducting ce- ramic such as a carbide or nitride. Furthermore some of the strands 12 are ar- ranged with a thin insulating layer 11, whereby all strands will be electrically in- sulated from each other by an electrical insulation, why at least one strand 1 la is in electrical contact with the inner semiconductive layer 14. This is achieved with a high voltage cable 10 according to figure 1, which comprises both insulated an uninsulated strands arranged such that two uninsulated strands are not in electri- cal contact. The used insulating layers 11 are stable during manufacture, and in- stallation of the high voltage cable 10, that is preferably at temperatures up to 220°C. Suitable insulations comprise insulation lacquers, such as lacquers based on formaldehydes, polyesters, polyesterimides, polyurethanes, polyamides, poly- imides, polyamidimides, thermoset plastics, extruded thermoplastics, oxides, ni- trides which can be generated or applied, silicates or other ceramic compounds, preferably applied by known surface coating or deposition techniques for the depo- sition of thin surface layers, which generate thin layers exhibiting sufficient adhe- sion in combination with strength and compactness.

In figure 2 a there is shown a cable core adapted to be part of a joint of a jointed high voltage winding according to one embodiment of present invention. The cable core 20 is comprised of a high voltage cable of the type shown in figure 1. On the

end surface 21 of the cable core 20 has been applied a coherent electrically con- ducting binder phase layer 25, such as a metallic solder. A soft solder, such as a soft solder based on silver, has preferably been used. The coherent electrically con- ducting binder phase layer 25 applied to the end surface 21 of the cable core, ties together an electrically contacts all the strands 23 comprised in the cable core. Ac- cording to the embodiment shown in figure 2b the electrically conducting binder phase layer 25 has been jointed with an electrically conducting body 26 attached to the end surface 21 and the layer 25, the body preferably being a portion of a joint- ing sleeve attached to the cable core 20. According to the alternative embodiment of a cable core 30 according to the invention shown in figure 3, an electrically con- ducting body 35 has been connected to and electrically contacted with the end surface 31 of the cable core by means of friction welding. The resulting connection exhibits an essentially metallic bonding to all the end surfaces of the strands 33, and constitutes a stable electrical contacting of all strands. The embodiment shown in figure 3, comprises also a cylindrical holder 38 for holding together the strands 33. Preferably the electrically conducting body 35 is part of a jointing sleeve at- tached to the cable core 30.

Stable electrical contact points between the strands of the cable core has been es- tablished according to particular embodiments of the present invention, in a cable core which is introduced in a jointing sleeve, in that the insulated strands com- prised in the cable core after or in connection with introduction into the jointing sleeve have been deformed such that stable electrical contact points have been es- tablished between the strands and between the outer strands and the applied jointing sleeve by the deformation. Often also the applied jointing sleeve has been deformed, such as by clamping around the inserted cable core.

Figures 4a and 4b show in detail two strands 43a, 43b with intermediate insulation 44a, 44b comprised in one embodiment of the invention. A compound 47 compris- ing hard electrically conducting particles 48 has been applied to the insulating layer of figure 4a, and as shown in figure 4b they have penetrated the insulating layers 44a, 44b after deformation such that stable electrical contact points have been established between the strands 43a, 43b. Preferably these hard and sharp electrical conducting particles 48 comprise an electrically conducting ceramic such as a nitride or a carbide of titanium, which suitably have been applied to the insu- lation of the strands dispersed in an electrically conducting contact grease 47.

In accordance with a further alternative embodiment, illustrated with figures 5a, 5b, 5c and 5d at least section 59 of the cable core 50 inserted into a sleeve 55 is

twisted, such that by the twisting, the strands 53,53a, 53b, 53c in the twisted part 59 have been deformed to such a degree that the strand insulation 54,54a, 54b, 54c by the deformation, entirely or partly has been removed, and such that the sleeve is compressed around the twisted conductor part, see the detail shown in figure 5d.

According to the embodiment of the present invention shown in figure 6 the joint which is part of the high voltage winding comprises a first cable core 60 which has been provided with a jointing sleeve 65. The jointing sleeve 65 is in its own end surface and the end surface 61 of the cable core provided with a pointed tip 650, which is run into an opposite second cable core 70 when the joint has been estab- lished. This second cable core 70 is held together by a clamp 75 such that the run in pointed tip 650 of the jointing sleeve electrically contacts essentially all strands 73 of this second cable core. Electrical contacting of all strands 63 of the first cable core 60 against each other and against the jointing sleeve has been achieved by means of any of the previously described embodiments. After the jointing sleeve 65 having a pointed tip is applied to the first cable core 60 and brought in contact against the strands 63 comprised in this cable core 60, the contacted pointed tip 650 of the jointing sleeve has been run into the second cable core 70. The other cable core 70 is tied together with a clamping means 75, such that the run in pointed tip 650 of the jointing sleeve is electrically contacted with essentially all strands 73 of the second cable core.