EP3394867B1 - Electrical transformer for remote high voltage devices - Google Patents

Description

The invention relates to equipment for high voltage networks, in particular the transmission of electrical power between remote equipment of an electrical network, the galvanic isolation between these remote equipment and the transformation of the voltage level between these remote equipment.

The document of M. Arun Kadavelugu 'High-Frequency Design Considerations of Dual Active Bridge 1200V SiC Mosfet DC-DC converter', published in 2011 by the IEEE on pages 314 to 320 , describes a DC / DC converter, in which two H bridges are galvanically isolated by a coaxial transformer. The coaxial transformer includes two arms, interconnected at their ends and supported by a frame. Each arm includes an internal section provided with several windings of the primary circuit, and an external section provided with several windings of the secondary circuit. The primary and secondary windings are isolated from each other. A magnetic core is positioned at the periphery of the primary and secondary windings. This magnetic core includes several spaced sections, in order to favor the cooling of the transformer. To gain compactness, the magnetic cores of the two arms are interlaced.

If it is desired to connect two remote DC voltage equipment or networks, the converter is connected by its input to a first network, its output being connected to the second network by electrical cables.

In practice, such an installation has drawbacks, since the volume occupied by the transformer at one of the two networks turns out to be particularly bulky for high voltage applications. The cooling of the transformer induces in particular a non-negligible size.

Such a coaxial transformer then turns out to be inappropriate. We then choose more conventional transformers, fitted with a magnetic core surrounded by primary and secondary windings. Electrical insulation is most often achieved by a fluid such as gas or oil circulating between the primary and secondary windings. The management of such a fluid presents safety, environmental, maintenance and congestion problems, which are particularly troublesome when the transformer is placed in a hostile environment, for example in a field of marine wind turbines.

The cooling and electrical insulation of such more conventional transformers is also problematic, even for local transformation applications.

The document DE4318270 describes a coaxial electrical transformer, comprising a winding of a primary circuit, a magnetic core surrounding the primary circuit winding, and a winding of a secondary circuit surrounding the magnetic core.

The document US2011 / 0291792 describes a coaxial transformer where the windings of the primary and secondary circuits are arranged within a magnetic core.

The document GB2447963 describes a coaxial electrical transformer, comprising a winding of a primary circuit, a magnetic core surrounding the primary circuit winding, and a winding of a secondary circuit surrounding the magnetic core.

The invention aims to solve one or more of these drawbacks. The invention thus relates to an electric transformer, as defined in the appended claim 1.

The invention also relates to the variants defined in the appended dependent claims. Those skilled in the art will understand that each of the characteristics of these variants can be combined independently with the characteristics of claim 1, without however constituting an intermediate generalization.

The invention also relates to an electrical infrastructure, as defined in the appended claims.

• la figure 1 est une représentation schématique d'un exemple d'implantation d'un transformateur selon l'invention ;
• la figure 2 est une vue en coupe transversale schématique illustrant différentes sections d'un câble d'un exemple de transformateur selon l'invention ;
• la figure 3 est une vue en coupe transversale d'un premier mode de réalisation de câble pour un transformateur selon l'invention ;
• la figure 4 est une vue en coupe selon un plan longitudinal du câble de la figure 3 ;
• la figure 5 est une vue en coupe transversale d'un deuxième mode de réalisation de câble pour un transformateur selon l'invention ;
• la figure 6 est une vue en coupe selon un plan longitudinal du câble de la figure 5 ;
• la figure 7 est une vue en coupe longitudinale d'un exemple d'interconnexions à l'extrémité d'un câble ;
• les figures 8 et 9 sont des représentations schématiques d'un exemple de câblage entre enroulements d'un circuit secondaire ;
• la figure 10 est une vue en coupe transversale d'une variante du premier mode de réalisation de câble pour un transformateur selon l'invention.

Other characteristics and advantages of the invention will emerge clearly from the description given below, by way of indication and in no way limitative, with reference to the appended drawings, in which:

• the figure 1 is a schematic representation of an example of installation of a transformer according to the invention;
• the figure 2 is a schematic cross-sectional view illustrating different sections of a cable of an example of a transformer according to the invention;
• the figure 3 is a cross-sectional view of a first embodiment of cable for a transformer according to the invention;
• the figure 4 is a sectional view along a longitudinal plane of the cable of the figure 3 ;
• the figure 5 is a cross-sectional view of a second embodiment of cable for a transformer according to the invention;
• the figure 6 is a sectional view along a longitudinal plane of the cable of the figure 5 ;
• the figure 7 is a longitudinal section view of an example of interconnections at the end of a cable;
• the Figures 8 and 9 are schematic representations of an example of wiring between windings of a secondary circuit;
• the figure 10 is a cross-sectional view of a variant of the first embodiment of cable for a transformer according to the invention.

The invention provides an electrical transformer in which the windings of the primary circuit and the secondary circuit are housed in a single cable, for example for the connection of two remote devices of a high voltage network. The cable of such a transformer comprises a central section, an intermediate section and a concentric peripheral section. The central section comprises at least one winding of the primary circuit, a winding of the secondary circuit and galvanic isolation between this winding of the primary circuit and this winding of the secondary circuit. The intermediate section surrounds the central section and has a magnetic core. The peripheral section surrounds the intermediate section and comprises a winding of the primary circuit and a winding of the secondary circuit. The peripheral section also includes galvanic isolation between this winding of the primary circuit and this winding of the secondary circuit. These two windings of the primary circuit, included respectively in the central section and in the peripheral section, are electrically connected at an axial end of the cable. These two windings of the secondary circuit, included respectively in the central section and in the peripheral section, are electrically connected at an axial end of the cable.

The figure 1 illustrates an example of installation of a transformer 1 according to the invention. The transformer 1 comprises an elongated cable 11, having axial ends 111 and 112. The cable 11 includes windings of a primary transformer circuit, windings of a secondary transformer circuit, and a magnetic core, as detailed by the after. At the end 111, the cable 11 has connection terminals 121 and 123 forming the terminals of the primary circuit of the transformer 1. At the end 112, the cable 11 has connection terminals 122 and 124 forming the terminals of the secondary circuit of transformer 1.

In this particular example, the transformer 1 is used for the transmission of electrical energy and the transformation of the voltage level between two pieces of equipment 82 and 84 distant from a direct high voltage network. The terminals 121 and 123 of the primary circuit are connected to an AC interface of a DC / AC converter 81. The equipment 82 is connected to a DC interface of the DC / AC converter 81. The terminals 122 and 124 of the secondary circuit are connected to an AC interface of a DC / AC converter 83. The equipment 84 is connected to a DC interface of the DC / AC converter 83.

The figure 2 is a schematic cross-sectional view illustrating different sections of a cable 11 of an example of transformer 1 according to the invention. In this cable 11, a central section 2, an intermediate section 3 and a peripheral section 4 can be defined, the sections 2, 3 and 4 being concentric. The peripheral section 4 surrounds the intermediate section 3, which surrounds the central section 2.

The figure 3 is a cross-sectional view of a first exemplary embodiment of the cable 11 of a transformer 1 according to the invention. The figure 4 is a sectional view along a longitudinal plane of the cable 11.

The central section 2 of the cable 11 comprises several windings 21 of the primary circuit of the transformer 1, several windings 22 of the secondary circuit of the transformer 1, and a solid galvanic insulation 23.

The galvanic isolation 23 is produced in the form of an electrically insulating layer (solid at room temperature) surrounding the windings 21 of the primary circuit. The windings 22 of the secondary circuit are positioned in contact with the external surface of this insulating layer 23. The windings 21 are distributed radially around the axis of the cable 11. The various windings 21 are separated and insulated by insulating walls 25 (solid at ambient temperature), extending in a radial direction between these windings 21. The windings 22 are distributed radially around the axis of the cable 11. The various windings 22 are separated and insulated by insulating walls 26 (solid to the room temperature), extending in a radial direction between these windings 22.

The intermediate section 3 surrounds the central section 2. The intermediate section 3 comprises a magnetic core or circuit 31. The magnetic core 31 here surrounds the central section 2. The magnetic core 31 here occupies the entire volume of the intermediate section 3.

The peripheral section 4 of the cable 11 comprises several windings 41 of the primary circuit of the transformer 1, several windings 42 of the secondary circuit of the transformer 1, and a solid galvanic insulation 43.

The galvanic isolation 43 is produced in the form of an electrically insulating layer (solid at room temperature) surrounding the windings 42 of the secondary circuit. The windings 42 are distributed radially around the axis of the cable 11. The windings 42 are here in contact with the magnetic core 31. The different windings 42 are separated and isolated by insulating walls 46 (solid at room temperature), extending in a radial direction between these windings 42. The windings 41 of the primary circuit are positioned in contact with the external surface of this insulating layer 43. The windings 41 are distributed radially around of the axis of the cable 11. The various windings 41 are separated and insulated by insulating walls 45 (solid at ambient temperature), extending in a radial direction between these windings 41.

Such a transformer 1 has convection cooling over the entire length of the cable 11. The length of the cable 11 thus promotes the cooling of the transformer 1, which makes it possible to avoid or limit the need to immerse the cable 11 in a flow of coolant. Furthermore, the galvanic insulation is here obtained by solid materials, which makes it possible to limit the risk of leakage, the maintenance constraints for the transformer 1. In addition, the electrical transformation being carried out over the length of the cable 11 also used for power transmission, the size of the transformer 1 is particularly reduced at the level of the remote equipment to which it is connected.

In this embodiment, the aim is to promote the ease of manufacture of the cable 11, by arranging the windings of the primary circuit and the windings of the secondary circuit in different layers. In addition, the manufacture of such a cable is facilitated, the galvanic isolations 23 and 43 can easily be produced by extrusion or wrapping, by methods known per se. Furthermore, this embodiment easily makes it possible to produce galvanic insulations of significant thickness between the various windings.

The peripheral section 4 of the cable 11 further comprises an insulating wall 48 (solid at room temperature) surrounding the windings 41. The peripheral section 4 of the cable 11 also advantageously comprises a conductive layer 49 (for example a metallic layer forming a screen or electromagnetic shielding The layer 49 forming a screen surrounds the insulating wall 48.

In the illustrated embodiment, the cable 11 advantageously comprises a mechanical reinforcement 29. The mechanical reinforcement advantageously extends over the entire length of the cable 11 (or even projecting relative to the cable 11, to allow its fixing by its ends). The mechanical reinforcement 29 is advantageously positioned in the center of the central section 2, at the level of the axis of the cable 11, in order to undergo less deformation during bending of the cable 11. The mechanical reinforcement 29 can for example include a wire rope covered with insulation, synthetic fibers, or a fiber-reinforced polymer.

In the illustrated embodiment, the insulating walls 25 extend radially between the mechanical reinforcement 29 and the insulating layer 23. In the illustrated embodiment, the insulating walls 26 extend radially between the insulating layer 23 and the magnetic core 31. In the exemplary embodiment illustrated, the insulating walls 46 extend between the magnetic core 31 and the insulating layer 43. In the exemplary embodiment illustrated, the insulating walls 45 extend between the insulating layer 43 and the insulating layer 48.

The magnetic core 31 has for example a shape which can be obtained by extrusion or concentric wrapping. The magnetic core 31 can for example be formed from a polymer resin loaded with magnetic powder. The magnetic core 31 can for example also be formed from rolled sheet and coated with an insulator. Such a material could for example be chosen to have a relative magnetic permeability of at least 150, preferably at least 200, advantageously 500. According to simulations, the magnetic coupling is at least 0.99 for a relative magnetic permeability at least 150 of the magnetic core 31.

The material used for one of the solid insulators 23, 25, 26, 43, 45 or 46 is for example chosen from the group comprising cross-linked insulating polyethylene, polypropylene, rubber (EPR, HEPR) or silicone.

The material used for the windings 21, 22, 41 or 42 is for example chosen from the group comprising copper and its alloys or aluminum and its alloys.

• la transmission d'une puissance de 10MW par le transformateur 1 ;
• une tension de 10 kV aux bornes du circuit primaire, une tension de 100 kV aux bornes du circuit secondaire ;
• un courant de 1000 A à travers le circuit primaire, un courant de 100 A à travers le circuit secondaire, avec une fréquence de 20 kHz ;
• une densité de courant de 1 A/mm² ;
• une induction magnétique de 0,2T.

An example of sizing for a cable 11 of transformer 1 according to the first embodiment may be the following. We expect:

• the transmission of a power of 10MW by the transformer 1;
• a voltage of 10 kV across the primary circuit, a voltage of 100 kV across the secondary circuit;
• a current of 1000 A through the primary circuit, a current of 100 A through the secondary circuit, with a frequency of 20 kHz;
• a current density of 1 A / mm ² ;
• 0.2T magnetic induction.

• Avec N : le nombre de spires de l'enroulement,
• B : l'induction magnétique,
• S : la section du circuit magnétique,
• F : la fréquence de fonctionnement.

As a reminder, the sinusoidal voltage V across a wound winding is calculated by Boucherot's formula: $$\mathrm{V}=\mathrm{\pi }*\surd 2*\mathrm{NOT}*\mathrm{B}*\mathrm{S}*\mathrm{f}$$

• With N: the number of turns of the winding,
• B: magnetic induction,
• S: the section of the magnetic circuit,
• F: the operating frequency.

The material chosen for the windings 21, 22, 41 and 42 is copper.

The material chosen for the screen layer 49 is aluminum.

The material used for the solid insulators 23, 26, 43 and 46 is crosslinked polyethylene.

The number of windings of the primary circuit in the central section 2 (and in the peripheral section 4) is 1. The number of windings of the secondary circuit in the central section 2 (and in the peripheral section 4) is 10.

An air passage opening (not shown in the figure 3 ) is provided in the center of the central section 2 to replace the mechanical reinforcement 29 and has a radius of 10 mm. The thickness of the winding 21 is 10.5 mm. The thickness of the insulating layer 23 is 5 mm. The thickness of the windings 22 is 5.6 mm. The width of the insulating walls 26 is at least 1 mm, preferably at least 2 mm. The thickness of the magnetic core 31 is 10 mm. The thickness of the windings 42 is 3.7 mm. The thickness of the insulating layer 43 is 5 mm. The thickness of the winding 41 is 3.1 mm. The thickness of the insulation layer 48 is 5 mm. The thickness of the screen layer 49 is 2.75 mm. Cable 11 has a length of 62.5 m.

The winding pitch of the windings 21 and 41 (here identical to the pitch for the windings 22 and 42) is for example between 5 and 30 times the diameter of the cable 11.

In the examples illustrated above, the terminals 121 and 123 on the one hand and 122 and 124 on the other hand, are arranged at opposite ends of the cable 11. However, the transformer 1 can also be used for local application, with terminals 121 to 124 positioned at the same end of the cable 11. Such a transformer 1 also makes it possible to benefit from cooling over the length of the cable and on the insulation capacity of solid galvanic insulation.

An example of a structure for the end of a cable 11, with terminals at the same end, is illustrated in a view in longitudinal section on the figure 7 . This illustration aims to represent interconnections between windings of the primary circuit of the central section 2 and of the peripheral section 4, or between windings of the secondary circuit of the central section 2 and of the peripheral section 4.

An end piece 5 is thus fixed to one end of the cable 11. The end piece 5 may include connection terminals for the primary or secondary, not illustrated here. The end piece 5 comprises an electrical connector 52, electrically connecting a winding 42 of the peripheral section to a winding 22 of the central section 2. The electrical connector 52 is for example fixed by welding to its respective windings 22 and 42.

The electrical connector 52 is covered at its periphery by an insulator 53. The insulator 53 is arranged in the continuity of the insulating layers 23 and 43 and covers the axial end of the electrical connector 52. The insulator 53 envelops the electrical connector 52 .

The end piece 5 also comprises an electrical connector 51, electrically connecting a winding 41 of the peripheral section to a winding 21 of the central section 2. The electrical connector 51 is for example fixed by welding to its respective windings 21 and 41. The connector electrical 51 is covered at its periphery by an insulator 54. The insulator 54 is arranged in the continuity of the insulating layer 48 and covers the axial end of the electrical connector 51.

The mechanical reinforcement 29 here extends axially through the end piece 5 and beyond.

• les enroulements 22 et 42 d'indice 1 sont connectés électriquement par l'interconnexion 521 ;
• les enroulements 22 d'indice 1 et 42 d'indice 2 sont connectés électriquement par l'interconnexion 612 ;
• les enroulements 22 et 42 d'indice 2 sont connectés électriquement par l'interconnexion 522 ;
• les enroulements 22 d'indice 2 et 42 d'indice 3 sont connectés électriquement par l'interconnexion 623 ;
• les enroulements 22 et 42 d'indice 3 sont connectés électriquement par l'interconnexion 523 ;
• les enroulements 22 d'indice 3 et 42 d'indice 4 sont connectés électriquement par l'interconnexion 634 ;
• les enroulements 22 et 42 d'indice 4 sont connectés électriquement par l'interconnexion 524 ;
• les enroulements 22 d'indice 4 et 42 d'indice 5 sont connectés électriquement par l'interconnexion 645 ;
• les enroulements 22 et 42 d'indice 5 sont connectés électriquement par l'interconnexion 525 ;
• les enroulements 22 d'indice 5 et 42 d'indice 6 sont connectés électriquement par l'interconnexion 656 ;
• les enroulements 22 et 42 d'indice 6 sont connectés électriquement par l'interconnexion 526 ;
• les enroulements 22 d'indice 6 et 42 d'indice 7 sont connectés électriquement par l'interconnexion 667 ;
• les enroulements 22 et 42 d'indice 7 sont connectés électriquement par l'interconnexion 527 ;
• les enroulements 22 d'indice 7 et 42 d'indice 8 sont connectés électriquement par l'interconnexion 678 ;
• les enroulements 22 et 42 d'indice 8 sont connectés électriquement par l'interconnexion 528 ;
• les enroulements 22 d'indice 8 et 42 d'indice 9 sont connectés électriquement par l'interconnexion 689 ;
• les enroulements 22 et 42 d'indice 9 sont connectés électriquement par l'interconnexion 529 ;
• les enroulements 22 d'indice 9 et 42 d'indice 10 sont connectés électriquement par l'interconnexion 690 ;
• les enroulements 22 et 42 d'indice 10 sont connectés électriquement par l'interconnexion 520.

In order to limit the electric field applied to the various insulating walls 26 and 46, the Figures 8 and 9 illustrate an example of interconnection for windings 22 and 42 of a secondary circuit according to the digital application detailed above (10 windings of the secondary circuit in each of sections 2 and 4). The Figures 8 and 9 illustrate the interconnections at respective opposite ends of the cable 11. The interconnections illustrated here make it possible to limit the difference in potential between adjacent windings 22, or between adjacent windings 42. The interconnections are shown here schematically in dotted lines. To the figure 9 , only the interconnection terminations have been illustrated, for the sake of readability. The windings 22 and 42 are numbered with an index n, windings 22 and 42 of index n being positioned facing each other radially. The windings 22, identified by their index n (and by analogy the windings 42), are positioned radially in the following order: 1-2-4-6-8-10-9-7-5-3. The interconnections between the windings are as follows:

• the windings 22 and 42 of index 1 are electrically connected by the interconnection 521;
• the windings 22 of index 1 and 42 of index 2 are electrically connected by the interconnection 612;
• the windings 22 and 42 of index 2 are electrically connected by the interconnection 522;
• the windings 22 of index 2 and 42 of index 3 are electrically connected by the interconnection 623;
• the windings 22 and 42 of index 3 are electrically connected by the interconnection 523;
• the windings 22 of index 3 and 42 of index 4 are electrically connected by the interconnection 634;
• the windings 22 and 42 of index 4 are electrically connected by the interconnection 524;
• the windings 22 of index 4 and 42 of index 5 are electrically connected by the interconnection 645;
• the windings 22 and 42 of index 5 are electrically connected by the interconnection 525;
• the windings 22 of index 5 and 42 of index 6 are electrically connected by the interconnection 656;
• the windings 22 and 42 of index 6 are electrically connected by the interconnection 526;
• the windings 22 of index 6 and 42 of index 7 are electrically connected by the interconnection 667;
• the windings 22 and 42 of index 7 are electrically connected by the interconnection 527;
• the windings 22 of index 7 and 42 of index 8 are electrically connected by the interconnection 678;
• the windings 22 and 42 of index 8 are electrically connected by the interconnection 528;
• the windings 22 of index 8 and 42 of index 9 are electrically connected by the interconnection 689;
• the windings 22 and 42 of index 9 are electrically connected by the interconnection 529;
• the windings 22 of index 9 and 42 of index 10 are electrically connected by the interconnection 690;
• the windings 22 and 42 of index 10 are electrically connected by the interconnection 520.

In the case where the primary circuit comprises several windings in the central section 2 and in the peripheral section 4, a similar interconnection mode can be used for the windings 21 and 41 in order to limit the electric field applied to the insulating walls 25 and 45.

• la transmission d'une puissance de 1MW par le transformateur 1 ;
• une tension de 5 kV aux bornes du circuit primaire, une tension de 5 kV aux bornes du circuit secondaire ;
• un courant de 200 A à travers le circuit primaire, un courant de 200 A à travers le circuit secondaire, avec une fréquence de 5 kHz ;
• une densité de courant de 1 A/mm² ;
• un champ magnétique de 0,2T.

Another example of sizing for a cable 11 of transformer 1 according to the first embodiment may be the following. We expect:

• the transmission of a power of 1MW by the transformer 1;
• a voltage of 5 kV across the primary circuit, a voltage of 5 kV across the secondary circuit;
• a current of 200 A through the primary circuit, a current of 200 A through the secondary circuit, with a frequency of 5 kHz;
• a current density of 1 A / mm ² ;
• a magnetic field of 0.2T.

The material chosen for the windings 21, 22, 41 and 42 is copper.

The material chosen for the screen layer 49 is aluminum.

The material used for the solid insulators 23 and 43 is crosslinked polyethylene.

The number of windings of the primary circuit in the central section 2 (and in the peripheral section 4) is 1. The number of windings of the secondary circuit in the central section 2 (and in the peripheral section 4) is 1.

An air passage opening (not shown in the figure 3 ) is provided in the center of the central section 2 to replace the mechanical reinforcement 29 and has a radius of 10 mm. The thickness of the winding 21 is 2.8 mm. The thickness of the insulating layer 23 is 5 mm. The thickness of the winding 22 is 1.7 mm. The thickness of the magnetic core 31 is 10 mm. The thickness of the winding 42 is 1.1 mm. The thickness of the insulating layer 43 is 5 mm. The thickness of the winding 41 is 0.9 mm. The thickness of the insulation layer 48 is 5 mm. The thickness of the screen layer 49 is 2.75 mm. Cable 11 has a length of 125 m.

The winding pitch of the windings 21 and 41 (here identical to the pitch for the windings 22 and 42) is for example between 5 and 30 times the diameter of the cable 11.

The figure 5 is a cross-sectional view of a second exemplary embodiment of the cable 11 of a transformer 1 according to the invention. The figure 6 is a sectional view along a longitudinal plane of the cable 11.

The central section 2 of the cable 11 comprises several windings 21 of the primary circuit of the transformer 1, several windings 22 of the secondary circuit of the transformer 1. The central section 2 here comprises alternating windings distributed around the axis of the cable 11. The number of windings 22 is here twice the number of windings 21.

The cable 11 further comprises galvanic insulation in the form of insulating elements 27 (solid at room temperature). The insulating elements 27 are distributed radially around the axis of the cable 11. The insulating elements 27 separate two adjacent windings from the central section 2. The insulating elements 27 here form insulating walls extending in a radial direction between two windings 21 or 22 adjacent.

The intermediate section 3 surrounds the central section 2. The intermediate section 3 comprises a magnetic core or circuit 31. The magnetic core 31 here surrounds the central section 2. The magnetic core 31 here occupies the entire volume of the intermediate section 3.

The peripheral section 4 of the cable 11 comprises several windings 41 of the primary circuit of the transformer 1 and several windings 42 of the secondary circuit of the transformer 1. The peripheral section 4 here comprises alternating windings distributed around the axis of the cable 11. The number of windings 42 is here twice the number of windings 41.

The cable 11 further comprises galvanic insulation in the form of insulating elements 47 (solid at room temperature). The insulating elements 47 are distributed radially around the axis of the cable 11. The insulating elements 47 separate two adjacent windings of the peripheral section 4. The insulating elements 47 here form insulating walls extending in a radial direction between two windings 41 or 42 adjacent.

The windings 41 of the primary circuit and the windings 42 of the secondary circuit are positioned in contact with the external surface of the magnetic core 31.

The peripheral section 4 of the cable 11 further comprises an insulating wall 48 (solid at room temperature) surrounding the windings 41 and 42. The peripheral section 4 of the cable 11 also advantageously comprises a conductive layer 49 (for example a metallic layer forming a screen or electromagnetic shielding. The screen layer 49 surrounds the insulating wall 48.

In the illustrated embodiment, the cable 11 advantageously comprises a mechanical reinforcement 29. The mechanical reinforcement advantageously extends over the entire length of the cable 11 (or even projecting relative to the cable 11, to allow its fixing by its ends). The mechanical reinforcement 29 is advantageously positioned in the center of the central section 2, at the level of the axis of the cable 11, in order to undergo less deformation during bending of the cable 11. The mechanical reinforcement 29 can have the same composition as for the first exemplary embodiment.

In the illustrated embodiment, the insulating walls 27 extend radially between the mechanical reinforcement 29 and the magnetic core 31. In the exemplary embodiment illustrated, the insulating walls 47 extend between the magnetic core 31 and the insulating layer 48.

The various embodiments of the cable 11 of a transformer 1 according to the invention have been illustrated described with a cable 11 having a rectilinear axis, for the sake of simplification. However, such a cable 11 will be flexible in most configurations. The axis of the cable 11 may thus be curvilinear, for example when the cable 11 is wound in a reel or when the middle part of the cable 11 has deformations by bending.

In the various embodiments described, the primary circuit and the secondary circuit of the transformer 1 each include several windings in the central section 2, and several windings in the peripheral section 4. It can however also be envisaged that the primary circuit and / or the secondary circuit of transformer 1 include a single winding in the central section 2 and a single winding in the peripheral section 4.

To promote the cooling of the cable 11 and serve for the transmission of power between remote network equipment, the length of the cable 11 is advantageously at least 100 times greater than its outside diameter.

In the examples illustrated, the transformer 1 is used for the transmission of power between remote high-voltage equipment. The distance between the high-voltage equipment can be greater than the length of the cable 11. In such a case, a power transmission cable can be connected to the terminals of the primary circuit and / or to the terminals of the secondary circuit to adapt the distance between these high voltage equipment.

• par la présence d'une isolation galvanique 91 ceinturant la section centrale 2. L'isolation galvanique 91 isole ici avantageusement les enroulements 22 par rapport au noyau magnétique 31 ;
• par la présence d'une isolation galvanique 92 ceinturant la section intermédiaire 3. L'isolation galvanique 92 isole ici avantageusement les enroulements 42 par rapport au noyau magnétique 31.

The figure 10 is a cross-sectional view of a variant of the first exemplary embodiment of the cable 11 of a transformer 1 according to the invention. Cable 11 differs from that of figure 3 :

• by the presence of galvanic isolation 91 surrounding the central section 2. The galvanic isolation 91 here advantageously isolates the windings 22 relative to the magnetic core 31;
• by the presence of galvanic isolation 92 surrounding the intermediate section 3. The galvanic isolation 92 here advantageously isolates the windings 42 with respect to the magnetic core 31.

Claims (11)

1. Electrical transformer (1), having a cable (11) with first and second axial ends (111,112), wherein the cable comprises:

   - a central section (2), an intermediate section (3) and a peripheral section (4) concentric with respect to each other;

   - the central section (2) having at least one first winding (21) of a primary circuit and at least one first winding of a secondary circuit (22), and at least a first solid galvanic insulation (23) between the said first winding of the primary circuit and the said first winding of the secondary circuit;

   - the intermediate section (3) surrounding the central section (2) and having a magnetic core (31);

   - the peripheral section (4) surrounding the intermediate section (3) and having at least one second winding (41) of the primary circuit and at least one second winding (42) of the secondary circuit, and at least a second solid galvanic insulation (43) between the said second winding of the primary circuit and the said second winding of the secondary circuit;

   - a first electrical connection (51) connected to one of the said axial ends (111,112) of the cable (11) between the first and second windings of the primary circuit;

   - a second electrical connection (52) connected to one of the said axial ends (111,112) of the cable (11) between the first and second windings of the secondary circuit.
2. Electrical transformer (1) according to claim 1, comprising two connection terminals (121, 123) connected to the primary circuit located at the first end (111) of the cable (11), and comprising two connection terminals (122, 123) connected to the secondary circuit located at the second end (112) of the cable (11).
3. Electrical transformer (1) according to claim 1 or 2, wherein the central section (2) comprises a mechanical reinforcement (29) extending throughout the entire length of the cable (11), the said mechanical reinforcement (29) being positioned at the centre of the central section.
4. Electrical transformer (1) according to any one of the preceding claims, wherein the central section (2) has an insulating layer (23) surrounding several windings of one between the primary circuit and the secondary circuit, and the other between the primary circuit and the secondary circuit having several windings in contact with the external surface of the insulating layer (23).
5. Electrical transformer (1) according to claim 4, wherein the said windings (22) in contact with the external surface of the insulating layer (23) are separated from each other by insulating walls (26) with a width at least equal to 1 mm.
6. Electrical transformer (1) according to any one of claims 1 to 3, wherein the central section (2) has alternating windings of the primary circuit and alternating windings of the secondary circuit distributed radially around the axis of the cable, the first galvanic insulation comprising insulating elements (27) distributed radially around the axis of the cable and separating the windings alternating in this manner.
7. Electrical transformer (1) according to any one of the preceding claims, wherein the said first galvanic insulation comprises a material selected from the group including polypropylene, or cross-linked polyethylene.
8. Electrical transformer (1) according to any one of the preceding claims, wherein the length of the cable (11) is at least 100 times greater than its diameter.
9. Electrical transformer (1) according to any one of the preceding claims, wherein the thickness of the said first galvanic insulation is at least 2 mm.
10. Electrical transformer (1) according to any one of the preceding claims, wherein the said windings of the primary circuit are wound with an axial pitch comprising between 5 and 30 times the diameter of the cable of circular section.
11. Electrical infrastructure, having:

    - a transformer according to claim 2;

    - a first electrical device (81) connected to connection terminals (121, 123) at the primary circuit at the first end of the cable (11);

    - a second electrical device (83) connected to connection terminals (122, 124) at the secondary circuit at the second end of the cable (11), the first or the second electrical device being configured so as to apply a voltage at least equal to 1 kV between the connection terminals to which it is connected.

Images