Assembly and cell for studying the aging of high-voltage cables

Abstract

Assembly and cell for studying the aging of a high voltage cable The invention relates to a method for manufacturing an assembly (2) for studying the aging of a high voltage cable (1), the method comprising forming a multilayer stack comprising superimposing a first electrode layer (202), at least one first insulating polymer layer (201), a second electrode layer (203), such that the first insulating polymer layer (201) is arranged between the first (202) and second (203) electrode layers, and a separating layer (204) of the first (202) and second (203) layers, and winding the multilayer stack (20) at least partly on itself around a longitudinal direction (A2) to form the assembly (2). Figure for abstract: Fig. 7

Description

Title of the invention: Assembly and cell for studying the aging of high-voltage cables Technical field

[0001] The present invention relates to the field of the study of the aging of electric cables, and in particular high-voltage electric cables. It finds a particularly advantageous application in the prediction of the mechanical and electrical behavior of high-voltage cable components, with the aim of improving their manufacture and / or predicting their service life. STATE OF THE ART

[0002] Generally speaking, and for example illustrated in [Fig. 1], a high-voltage cable comprises in its cross-section a core 11 surrounded by an internal semi-conducting sheath 12, itself surrounded by an insulating material 13 based on an electrically insulating polymer. The core 11 generally comprises metal wires 110, for example braided together. The insulating material 13 is typically surrounded by an external semi-conducting sheath 14, surrounded by an electromagnetic shield 15 then by an electrically insulating outer sheath 16.

[0003] The breakage of high voltage cables is often due to the insulating material surrounding the internal semiconducting sheath, or to the material of the external semiconducting sheath. There is therefore a need to study the aging of these materials of interest in order to make high voltage cables more reliable and / or to be able to predict their service life.

[0004] The modeling, prediction and expertise of the aging of dielectrics and semiconductors making up high-voltage cables is typically done by an accelerated aging approach under conditions coupled between exposure to an electric current, and mechanical and / or thermal stresses in an environment representative of the use of the high-voltage cable, for example without oxygen with the presence of humidity.

[0005] For high-voltage electrical cables, the approach used by cable manufacturers is to develop model mini-cables, with a smaller cross-section and length than high-voltage cables. These mini-cables are then aged in thermo-regulated enclosures. These enclosures are generally associated with an external high-voltage generator to electrically power the cables. This technique makes it possible to couple two acceleration factors: temperature and the electric field.

[0006] However, the mini-cable approach offers little volume of material to study the evolutions of the properties of the materials. Material studies indeed require a large quantity of samples to correctly establish the fragility statistics. mechanical and dielectric properties. In addition, the microstructure, thermomechanical history and mechanical state of a mini-cable differs from that of a real high-voltage cable. These differences pose a problem of representativeness for aging studies and cable life prediction.

[0007] Another solution used consists of shaping the insulating material in the molten state to produce specific test pieces called Rogowski type, on which the aging study is carried out. For this, granules of the same polymer as that used in a high-voltage cable are generally used, which is shaped by compression to manufacture the test piece. In the case of the production of Rogowski test pieces, the degree of representativeness is therefore even lower. Reshaping the material leads to a significant deviation from the reality of the material, and its thermo-mechanical history during the manufacture of the high-voltage cable. In addition, the production of each test piece is tedious, which limits the aging study statistics.

[0008] An object of the present invention is therefore to propose a solution improving the study of the aging of high voltage electric cables.

[0009] Other objects, features and advantages of the present invention will become apparent from a consideration of the following description and accompanying drawings. It is understood that other advantages may be incorporated. SUMMARY

[0010] To achieve this objective, according to a first aspect, a method is provided for manufacturing an assembly for studying the aging of an electric cable, and in particular a high-voltage cable, the method comprising: - a formation of a multi-layer stack comprising at least partial superposition of: • a first layer called an electrode, based on an electrically conductive material, • at least one layer based on an electrically insulating polymer, called the first layer of insulating polymer, • a second layer called an electrode layer, based on an electrically conductive material, so that the first layer of insulating polymer is arranged between the first and second electrode layers, and • a separating layer at least partly superimposed with the assembly formed by the first and second layers of electrodes and the first layer of insulating polymer, - winding the multilayer stack at least partly on itself around a longitudinal direction to form the assembly.

[0011] The electrical aging of a cable is a function of the electromotive force in the cable. This force depends on the voltage and the thickness of the material through which the electric current flows. The use of a layer of insulating polymer in a stack, this layer being particularly thin compared to existing solutions, makes it possible to reduce the voltage necessary to obtain exposure to an electric current that is more representative of the actual wear of a high-voltage cable. The aging study is thus facilitated and is also more representative of actual aging.

[0012] Furthermore, since the insulating polymer is in the form of a layer intercalated between the electrodes, the assembly makes it possible to better expose the insulating polymer layer to electrical and thermal stresses compared to existing solutions. The aging study is thus made more reliable.

[0013] This multi-layer stacking configuration allows accelerated aging of this layer while obtaining a sufficient volume of material to carry out the aging study, and in particular the mechanical and dielectric analyses.

[0014] Furthermore, the assembly setup is simplified compared to existing solutions, which facilitates the production of several assemblies to improve the statistics of an aging study.

[0015] The aging study is therefore improved, in particular compared to existing solutions using mini-cables.

[0016] A second aspect relates to an assembly for studying the aging of an electric cable, and in particular a high-voltage cable. The assembly comprises a multilayer stack at least partly wound on itself around a longitudinal direction, the multilayer stack comprising: - a first and a second layer, called electrodes, based on an electrically conductive material, - a first layer based on an electrically insulating polymer of high voltage cable, called first layer of insulating polymer, and arranged between the first and second electrodes, and - a separating layer configured to electrically insulate the first and second electrode layers from each other, in the wound multilayer stack.

[0017] The assembly thus presents the effects and advantages described previously with reference to the manufacturing method according to the first aspect.

[0018] A third aspect concerns a cell for studying the aging of a high voltage cable, comprising: - the assembly according to the second aspect or manufactured according to the first aspect, and - a capsule configured to electrically power the assembly, the capsule including: • a body, a first cap and a second cap, defining a closed interior volume, the capsule being configured to receive the assembly in the closed interior volume, • two electrodes each configured to connect a separate electrode layer of the assembly.

[0019] The cell thus makes it possible to carry out the aging study of the assembly by electrical connection to an external electrical power source.

[0020] A fourth aspect relates to a system comprising several cells according to the third aspect and a housing configured to receive and electrically power the cells.

[0021] The system thus makes it possible to parallelize the aging study for several cells. This makes it possible in particular to obtain aging statistics for samples of the same type of electric cable. In synergy with sealed capsules, this makes it possible to carry out an aging study in parallel for different aging conditions. The system is therefore particularly advantageous given the duration of the aging studies, which can, for example, last several years.

[0022] A fifth aspect relates to a method for studying the aging of an electric cable, and in particular a high-voltage cable, the method comprising: - an exposure of at least one assembly according to the second aspect or manufactured according to the method according to the first aspect, to an electric current, - at least one measurement of an electrical property, and for example of the internal resistance, of at least one assembly so as to obtain data representative of the aging of a high-voltage cable.

[0023] The assembly may be comprised in a cell according to the third aspect. The assembly may be comprised in a cell according to the fourth aspect. BRIEF DESCRIPTION OF THE FIGURES

[0024] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of an embodiment thereof which is illustrated by the following accompanying drawings.

[0025] [Fig.l] [Fig.l] represents a cross-sectional view of a high-voltage cable, according to an exemplary embodiment.

[0026] [Fig.2] [Fig.2] represents a side view of a portion of high voltage cable, according to an example of realization.

[0027] [Fig.3] [Fig.3] represents a view of one end of a cut portion of high voltage cable, according to an exemplary embodiment.

[0028] [Fig.4] [Fig.4] represents a perspective view of the steps of straightening the cut portion of high voltage cable, according to an exemplary embodiment.

[0029] [Fig.5] [Fig.5] represents a perspective view of the cutting of the portion of high voltage cable, according to an exemplary embodiment.

[0030] [Fig.6A] Figures 6A to 6C respectively represent side, top and other side views of the multilayer stack before it is wound, according to an exemplary embodiment.

[0031] [Fig.ôB]

[0032] [Fig.ôC]

[0033] [Fig.7] [Fig.7] represents a cross-sectional view of the assembly, according to an exemplary embodiment.

[0034] [Fig.8] [Fig.8] represents a cross-sectional view of the cell comprising the assembly illustrated in [Fig.7], according to an exemplary embodiment.

[0035] [Fig.9] [Fig.9] represents a cross-sectional view of the system, according to an exemplary embodiment.

[0036] [Fig. 10] [Fig. 10] represents a cross-sectional view of the system illustrated in [Fig.9], in a thermoregulated enclosure, according to an exemplary embodiment.

[0037] The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily on the scale of practical applications. In particular the relative dimensions of the layers and layer thicknesses in the stack are not representative of reality. DETAILED DESCRIPTION

[0038] Before commencing a detailed review of embodiments of the invention, optional features are set out below which may optionally be used in combination or alternatively.

[0039] According to one example, the method further comprises: - a supply of a portion of high-voltage cable comprising a core extending in a main direction of extension of the cable and surrounded around said direction by a material based on the electrically insulating polymer, - formation of a film based on the electrically insulating polymer, by trimming the portion of high voltage cable around the main extension direction of the cable, at least a portion of the film being used during the formation of the multilayer stack.

[0040] Thus, the assembly for the study of aging is manufactured from a real high-voltage cable. The material studied has a maximum degree of representativeness because the microstructural structure, any additives, thermomechanical history and mechanical state at the end of manufacturing is that of a real cable, for example from its transport drum. By clipping, the film formed is also representative of the aging of the material of interest at a given location in the cross-section of the high-voltage cable. It is therefore possible to study the aging over all or part of the cross-section of the cable material(s) constituting the film.

[0041] Furthermore, this method makes it possible to expose the cable portion to aging, or to study a cable portion already aged by use. This makes it possible to carry out aging studies under conditions that are even closer to the actual wear of a cable, and for example to analyze the possible causes in the event of a observed break in the high-voltage cable. According to one example, the method comprises, before the formation of the film, aging the high-voltage cable comprising exposing the cable portion to an electric current, and / or in which the cable portion comes from a previously used high-voltage cable.

[0042] According to one example, the winding of the multilayer stack is carried out under an atmosphere of controlled humidity level and / or controlled oxygen level. Thus, the environmental conditions of aging of the cable can be reproduced at the scale of the assembly at the level of the insulating polymer layer.

[0043] According to one example, the method comprises arranging the assembly in the capsule described in the third aspect of the invention.

[0044] According to one example, the arrangement of the assembly in the capsule described in the third aspect of the invention is carried out under an atmosphere of controlled humidity level. The arrangement of the assembly in the capsule may be followed by the sealing of the capsule.

[0045] According to one example, the method further comprises, before forming the multilayer stack, selecting the portion of the film to form the multilayer stack, according to the corresponding position of the electrically insulating polymer-based material in the high-voltage cable. It is thus possible to analyze the aging according to the location of the material in the cable, and for example to conduct these analyses for distinct locations radially and / or longitudinally in the cable.

[0046] According to one example, the method comprises, before the formation of the film: - straightening a lateral periphery of the cable portion, and / or - a dressing of at least one, and preferably each, end of the portion of cable.

[0047] Due to the mechanical constraints exerted inside a high-voltage cable, and in particular following cutting to obtain the cable portion, these dressings each allow a better quality working surface to be found for trimming. Thus, the defects induced by cutting and not linked to manufacturing or normal aging of the cable can be eliminated from the resulting assembly.

[0048] According to one example, the insulating polymer layer comes from the cutting of a high-voltage cable.

[0049] The assembly can be obtained by the method according to the first aspect.

[0050] According to one example, at least one of the first and second electrode layers protrudes at least partially from the first insulating polymer layer and the separating layer in the longitudinal direction. The electrical connection of the electrode is thus facilitated on the portion of the electrode protruding from the other layers.

[0051] Preferably, each of the first and second electrode layers protrudes from the first insulating polymer layer and the separating layer in the longitudinal direction, such that the first electrode layer protrudes from the first insulating polymer layer and the separating layer on a first side of the stack relative to the longitudinal direction, preferably without protruding on a second side opposite the first side, and the second electrode layer protrudes from the first insulating polymer layer and the separating layer on the second side of the stack, preferably without protruding on the first side,

[0052] According to one example, the first and second electrode layers are arranged offset from the first insulating polymer layer and the separating layer in the longitudinal direction, so that: - the first electrode layer protrudes from the first insulating polymer layer and the separating layer on a first side of the multi-layer stack relative to the longitudinal direction, without protruding on a second side of the multi-layer stack opposite the first side, - the second electrode layer protrudes from the first insulating polymer layer and the separating layer on the second side of the multilayer stack, without protruding on the first side.

[0053] The electrical connection of each electrode is thus simplified while maintaining a simple configuration of the assembly. In addition, the offset of the electrode layers allows these layers to protrude beyond the others over a large part of their length, and preferably over their entire length. The electrical connection will therefore be further simplified. Thus, each of the electrodes is exposed on one of the faces of the winding, and more particularly on these ends on either side of the longitudinal direction, which faces will be used for the accessible electrical connection.

[0054] According to one example, the first layer of insulating polymer has a thickness substantially between 50 μm and 200 μm, preferably a thickness substantially between 70 μm and 150 μm, preferably substantially equal to 100 μm. The thickness of the layer of insulating polymer in these ranges is particularly suitable for reducing the voltage to be applied while maintaining an electrical force. representative tromotive. This thickness is particularly advantageous for obtaining homogeneous aging throughout the thickness. A thinner thickness exacerbates the fragility of the material after aging. Too great a thickness induces heterogeneous aging, typically with an oxidized layer on either side of the insulating polymer layer. With 100 pm, we prevent any possible porosity from piercing and weakening the insulating film.

[0055] According to one example, the separating layer is a layer based on an electrically insulating material, and preferably an electrically insulating polymer.

[0056] According to one example, the separating layer is a second layer based on the electrically insulating polymer of high voltage cable, called second layer of insulating polymer. Preferably, each layer of insulating polymer has a thickness substantially between 50 μm and 200 μm, preferably a thickness substantially between 70 μm and 150 μm, preferably substantially equal to 100 μm.

[0057] According to one example, the separating layer is an adhesive. According to one example, the separating layer is a film resulting from a different trimming.

[0058] According to one example, the separating layer is a layer based on a polymer selected from the group consisting of polyimide (PI), polypropylene (PP), high density polyethylene (HDPE), low density polyethylene (LDPE), crosslinked polyethylene (PEr), ultrahigh molecular weight polyethylene (UHMWPE), ethylene-propylene-diene monomer rubber (EDPM), polyamide (PA), polyoxymethylene (POM), polyetheretherketone (PEEK), polyethyleneterephthalate (PET).

[0059] According to one example, the separating layer is a layer based on a polymer chosen from the group consisting of polyimide (PI). The assembly is thus particularly suitable for very high voltage aging studies, for example for voltages substantially equal to 10,000 V.

[0060] According to one example, the separating layer may be obtained by cutting out a portion of cable distinct from the portion of cable from which the insulating polymer layer originates. It is thus possible to age two samples of different cable sectors under identical conditions.

[0061] According to one example, the assembly comprises an internal support around which the multilayer stack is wrapped. Preferably, the internal support is electrically insulating.

[0062] According to one example, the cell body and the first and second caps are configured to define the sealed interior volume. The sealed capsule thus maintains an internal atmosphere, so as to adapt to the aging conditions as needed, and for example according to the humidity level and / or the presence or absence of oxygen.

[0063] According to one example, in the assembly, at least one of the first and second electrode layers protrudes at least partially from the first insulating polymer layer and the separating layer in the longitudinal direction, so as to be in electrical contact with the corresponding electrode of the capsule, arranged opposite said electrode layer. The capsule thus allows a simplified electrical connection with the assembly, in synergy with the protrusion of the electrode(s) of the assembly.

[0064] Preferably, each of the first and second electrode layers protrudes from the first insulating polymer layer and the separating layer in the longitudinal direction, such that the first electrode layer protrudes from the first insulating polymer layer and the separating layer on a first side of the stack relative to the longitudinal direction, preferably without protruding on a second side opposite the first side, and the second electrode layer protrudes from the first insulating polymer layer and the separating layer on the second side of the stack, preferably without protruding on the first side, so as to be in electrical contact with the corresponding electrode, arranged opposite said electrode layer.

[0065] According to one example, at least one and preferably each electrode of the capsule is compressed against the corresponding electrode layer of the assembly, and against the corresponding plug. The electrical connection is made more reliable. The aging study will therefore be made more reliable.

[0066] According to one example, each plug is electrically conductive and is electrically connected to an electrode of the capsule, and in which the body of the capsule is configured to electrically insulate the first and second plugs from each other. The electrical connection of the capsule to an external power source is thus facilitated. In synergy with the protrusion characteristics of the electrode layers and / or the compression of the electrode(s) of the capsule, it is understood that the successive electrical connections are made more reliable.

[0067] According to one example, the body of the capsule comprises: - a first electrically insulating sleeve laterally surrounding the assembly, - a second metal sleeve laterally surrounding the first sleeve, the second sleeve preferably being in electrical contact with the second plug, and - an electrically insulating collar separating the first plug from the second sleeve.

[0068] The assembly is thus electrically insulated from the body of the capsule. The second metal sleeve improves the thermal conduction of the capsule. This improves therefore the transmission of thermal energy to the assembly during an aging study.

[0069] According to one example, the capsule is configured to form a sealed and removable junction at the collar. For example, a first seal may be disposed at an abutment area of ​​the first cap on the collar.

[0070] For example, a second seal may be arranged at a zone where the second sleeve abuts the collar.

[0071] According to one example, the system comprises a number of cells greater than or equal to 50, preferably greater than or equal to 100.

[0072] According to one example, the housing comprises: - a first cover comprising several electrical connectors, the electrical connectors being configured to each electrically connect at least one cell, separately from the at least one cell connected by the other electrical connectors, and - a second cover configured to electrically connect together the electrical connectors of the first cover to an external electrical power source.

[0073] The first cover makes it possible to analyze the electrical properties of each cell, and therefore of each assembly, in a differentiated manner. As variability between cells can be observed, a measurement for each assembly can be made. It is also possible to make in situ measurements without dismantling the entire system. This is all the more advantageous given the duration of the aging studies, and therefore the number of measurements to be made.

[0074] The second cover allows parallelization of the power supply for the aging of the assemblies, and simplifies the connection of the cells to the external power source. The system is thus modular between diagnostic phases and aging phases, which simplifies the aging study.

[0075] According to one example, the cell and / or the system comprises the external electrical power source.

[0076] According to one example, the electric current has a voltage between 5,000 V and 20,000 V in the aging study method. These voltages allow aging of the assembly to evaluate the aging of a corresponding high-voltage cable. In synergy with the thickness of the insulating polymer layer, these voltages allow homogeneous aging representative of the electromotive force in a high-voltage cable in use.

[0077] In the remainder of the description, the term “on” does not necessarily mean “directly on”. Thus, when it is indicated that a part or a member A is in bearing "on" a part or organ B, this does not mean that the parts or organs A and B are necessarily in direct contact with each other. These parts or organs A and B can either be in direct contact or be bearing on each other through one or more other parts. The same applies to other expressions such as, for example, the expression "A acts on B" which can mean "A acts directly on B" or "A acts on B through one or more other parts".

[0078] In the present patent application, when it is indicated that two parts are distinct, this means that these parts are separate. They can be: - positioned at a distance from each other, and / or - movable relative to each other and / or - secured to each other by being fixed by added elements, this fixing being removable or not.

[0079] A single-piece unit cannot therefore be made up of two separate parts.

[0080] In the present patent application, the term "integral" used to qualify the connection between two parts means that the two parts are linked / fixed relative to each other, according to all degrees of freedom, unless explicitly specified differently. For example, if it is indicated that two parts are integral in translation according to a direction X, this means that the parts can be movable relative to each other, possibly according to several degrees of freedom, excluding the freedom in translation according to the direction X. In other words, if one part is moved according to the direction X, the other part performs the same movement.

[0081] For the purposes of this disclosure, the expression "A and / or B" means (A), (B), or (A and B). For the purposes of this disclosure, the expression "A, B and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).

[0082] A layer, or a material based on a species A, is understood to mean a layer, or a material comprising this species A only or this species A and possibly other species, for example additives.

[0083] A parameter “substantially equal / greater / less than” a given value means that this parameter is equal / greater / less than the given value, within plus or minus 10% of this value. A parameter “substantially between” two given values ​​means that this parameter is at least equal to the smallest given value, within plus or minus 10% of this value, and at most equal to the largest given value, within plus or minus 10% of this value.

[0084] The various aspects of the invention are now described according to exemplary embodiments with reference to the figures.

[0085] As illustrated in Figures 2 to 7, an assembly 2 is used for the study of the aging of a high voltage electric cable 1. A high voltage electric cable, or equivalently a high voltage cable, means an electric cable configured to be crossed by a voltage greater than or equal to 200,000 V, typically between 200,000 V and 500,000 V, for example 225,000 V and / or 275,000 V. A high voltage cable may typically have a cross-section having a dimension greater than or equal to 80 mm. In the following, the term "cable" is used to designate a high voltage cable.

[0086] The assembly 2 is manufactured by forming a multilayer stack 20 comprising an at least partial superposition of layers. This superposition comprises, with reference to FIGS. 6A to 7: - a first electrode layer 202, based on or made of an electrically conductive material, - a layer of insulating polymer 201 of high voltage cable, - a second layer called electrode 203, based on or made of an electrical material strictly conductive, and - a separating layer 204.

[0087] This stack 20 is wound on itself around a winding direction A2, to form a coil of the multilayer stack having a longitudinal direction A2. The term longitudinal is more particularly used to designate the main extension direction of the assembly, once wound. The direction A2 is here more particularly parallel to the direction z. Preferably, the multilayer stack 20 is entirely wound on itself along the direction of the length of the layers of the stack. According to one example, the multilayer stack 20 wound on itself comprises only the aforementioned layers, that is to say without an additional layer included in the stack.

[0088] The insulating polymer layer, also referred to as the first insulating polymer layer 201, is arranged between the first 202 and second 203 electrode layers. Thus, the insulating polymer layer 201 can be exposed to an alternating or direct electric current, so as to simulate accelerated aging of this material, within the framework of an aging study of a high-voltage cable 1.

[0089] The separating layer 204 is configured to electrically insulate the first 202 and second 203 electrode layers from each other. The separating layer 204 is for this purpose at least partly superimposed with the assembly formed by the first 202 and second 203 electrode layers and the first insulating polymer layer 201. The separating layer 204 may more particularly be arranged below or above the assembly formed by the first 202 and second 203 electrode layers and the first insulating polymer layer 201. Once the multilayer stack 20 is wound, the separating layer 204 is arranged between the first 202 and second 203 layers of electrodes so as to electrically insulate them.

[0090] To manufacture this assembly 2, as illustrated by [Fig.2], a portion 10 of cable 1 can be provided. Thus, the assembly 2 is manufactured from an actual high-voltage cable. As illustrated by [Fig.l], this portion 10 can comprise in its cross-section a core 11 surrounded by an internal semi-conducting sheath 12, itself surrounded by an insulating material 13 based on an electrically insulating polymer. The core 11 can comprise metal wires 110, for example braided together. The insulating material 13 can be surrounded by an external semi-conducting sheath 14, surrounded by an electromagnetic shield 15 and then by an electrically insulating outer sheath 16.

[0091] The portion 10 can be cut from a cable 1, for example by cutting. This cutting operation can cause numerous defects at the ends 10a and 10b. These defects can be explained by the internal stresses in the cable 1. These internal stresses can in particular cause a shrinkage of the dielectric material 13 along the main extension direction A1 of the portion 10 of cable 1. In addition, defects linked to the cutting operation, such as metal particles or sheath waste, can be observed.

[0092] In order to eliminate these defects, and as illustrated in [Fig.4] for example, the method may comprise a straightening of the portion 10 of cable. A straightening of the lateral periphery 100 of the portion 10 of cable 10 may be carried out, for example according to the arrow FL. This straightening may be configured so as to remove the elements of the cable 1 up to the electromagnetic shielding 15, and in particular the insulating outer sheath 16. Thus, a cylindricity of the circumference of the cable 1 is found. A straightening may be carried out at at least one and preferably at each end 10a, 10b of the portion 10 of cable 1, for example according to the arrows F2 and F3. This straightening is preferably done so as to flatten the cross-section at the end 10a, 10b, preferably until the shrinkage of the insulating material is corrected. This allows the correction of defects linked to cutting and linked to internal constraints in cable 1. These dressings can be carried out on a conventional lathe.

[0093] These cutting and / or dressing steps can cause a lot of debris and dust, which can impact the behavior of the assembly 2 during the aging study, and for example induce a breakdown of the insulating polymer of the first layer 201. The data collected during the aging study can therefore be impacted. The method can include one or more cleaning operations in order to avoid metallic and plastic contamination. This or these cleaning operations can be with compressed air, mechanical type (for example brush, by ultrasound), in a liquid medium, or a mixture of these conditions (for example in an ultrasonic bath).

[0094] A film 200 can then be formed by trimming the portion 10 of cable 1 around of the main extension direction Al of the portion 10 of cable 1. As illustrated for example by [Fig.5], a blade 6 can cut a film 200 by relative rotation between the blade 6 and the portion 10 of cable 1 around the axis Al, and in particular by rotation of the portion 10 of cable 1. This operation can be done by a conventional turning device. The trimming operation can be done from the electromagnetic shielding 15 to the internal semi-conductor sheath 12. According to our example, the electromagnetic shielding 15 can be removed before the trimming operation, the trimming then being carried out from the external semi-conductor sheath 14. The shielding can be removed by a turning operation on the outer periphery of the portion 10 of cable. This operation also makes it possible to compensate for the cylindricity of the portion 10 often curved by the winding of the cable on the reel.Depending on the position of the cable section on the reel, the curvature is more or less pronounced.

[0095] It is possible to also trim the internal semi-conductor sheath 12. For this, it is possible to completely machine the metal core 11 to remove all the metal elements from the cable portion 10, cleaning to eliminate all the metal contamination. It would then be possible to plug the hole left by the core 11 with a core made of insulating polymer (polyethylene for example), for example force-fitted to be able to finally trim down to the semiconductor of the internal sheath and even beyond into the insulating polymer core to completely recover the internal semiconductor.

[0096] The trimming operation may for example produce a length of film 200 greater than or equal to 10 m, preferably greater than or equal to 20 m, and more preferably still substantially equal to 30 m. The film 200 may comprise a portion based on or made of the electrically insulating polymer, and a portion based on or made of the outer cladding semiconductor 14. The portion based on or made of the outer cladding semiconductor 14 may have a length greater than or equal to 1 m, for example substantially equal to 1.5 m.

[0097] Only a portion 200a of the film 200 can be used to form the multilayer stack 20. The method can therefore comprise cutting this portion 200a from the film 200. This portion 200a can be selected from the film 200 according to its corresponding location in the cable 1, for example the locations 200b or 200c illustrated in [Fig.5].

[0098] Note that the film 200 obtained by trimming has scratches (traces of the cutting edge) on the wire, coming from the vibration during cutting. Under polarized light, it is possible to observe by birefringence local deformations linked to cutting. On an extruded film, the surface is smooth and free from local deformations

[0099] From a film 200, it is therefore understood that several assemblies 2 can be manufactured. The method therefore makes it possible to manufacture, in a simplified manner compared to existing solutions, several assemblies 2. It is thus possible to have more data for the study of aging and therefore more statistics available. As seen above, these data can for example take into account the radial location of the insulating material 13 in the cable 1. It is also possible to provide that the portion 10 of cable 1 is chosen according to the location of the portion 10 in the cable 1. Even more statistical data can be obtained from the study.

[0100] Prior to the formation of the film 200, the method may comprise aging the portion 10 of cable 1, for example by exposing it to given electrical, mechanical and / or thermal conditions, described as an example later. Due to the use of only a portion 10 of cable 1, and not an entire high-voltage cable, it is in fact possible to subject this portion to aging to study its impact on the structure of the materials as close as possible to real conditions. As an alternative in addition, it is possible to use a portion 10 coming from a cable 1 already used for high-voltage electrical power supply, already aged naturally in real operating conditions, for example in a particularly stressed area of ​​the electrical network.

[0101] The portion 200a will thus form the first layer of insulating polymer 201 of the multilayer stack 20. The multilayer stack 20 is now described in more detail with reference [Fig.6A] to 6C.

[0102] Each layer of the stack 20 has a length and a width, the length in the y direction being greater than the width in the z direction. The longitudinal winding direction A2 may be substantially perpendicular to the length direction of each layer.

[0103] The different layers of the stack 20 can be arranged between them so as to facilitate the electrical connection of the electrode layers 202, 203.

[0104] For this, and as illustrated by FIGS. 6A to 6C, the layers of the multilayer stack 20 may be offset from each other. More particularly, each electrode layer 202, 203 may protrude from the first insulating polymer layer 201 and the separating layer 204 in the winding direction A2. The first electrode layer 202 may protrude from a first side of the multilayer stack 20. The second electrode layer 203 may protrude from the other side of the multilayer stack 20 opposite the first side. Contact portions 202a, 203a are thus formed.

[0105] Preferably, at least one, and preferably each, of the first and second electrode layers 202, 203 protrudes from the first insulating polymer layer and the separating layer in the longitudinal direction, over substantially at least 80% of their length and preferably over their entire length.

[0106] As an alternative or in addition to a shift of the electrode layers, it is possible providing that the electrode layers comprise at least one and preferably several tabs which protrude from the first insulating polymer layer 201 and the separating layer 204 in the winding direction A2.

[0107] According to one example, the edges of the lengths of the electrode layers 202, 203 protrude from the edges of the lengths of the first insulating polymer layer 201 by a distance d1, d6 substantially greater than 5 mm, preferably substantially greater than or equal to 10 mm.

[0108] The different layers of the stack 20 may be arranged between them so as to limit the risk of contact between the electrode layers 202 and 203, and thus avoid a short circuit when an electric current is applied. For example, the electrode layer protruding from one side of the multilayer stack 20 may be set back from the separating layer 204 and / or the first insulating polymer layer 201 on the other side, as illustrated for example [Fig. 6B]. This setback may correspond to the distance d3 and be greater than or equal to 5 mm.

[0109] For this, the length L1 along the Y direction of the first insulating polymer layer 201 and of the separating layer 204 may be strictly greater than the length L2 of the electrode layers 202, 203. The risk of contact between the electrode layers 202, 203 once the multilayer stack 20 is wound is thus reduced. For example, the difference L1-L2 may be greater than or equal to 10 mm, preferably greater than or equal to 20 mm. The maximum length of the layers of the multilayer stack 20 may be greater than or equal to 50 cm, preferably greater than or equal to 70 cm.

[0110] For example, the width d2 of the first layer of insulating polymer 201 may be greater than or equal to 40 mm, preferably greater than or equal to 50 mm. The separating layer 204 may further have at least one distance d4 strictly greater than the distance taken in the same direction of the first layer of insulating polymer 200, for example d4 is greater than or equal to 5 mm.

[0111] The assembly may be under a determined mechanical tension to be in a fixed stretching state, for example between 1% and 5% (i.e. 1%, 2% or 5% for example), so as to reproduce the actual axial stress state of the cable as the real cable may be, or when the cable expands during operation (the expansion of the cable core produces an axial tensile stress via the Poisson effects of the insulating material). The cable core may in fact reach 90°C.

[0112] The length of the separating layer 204 may be greater than the length of the insulating layer L1, especially if the separating layer is a polyimide adhesive. This makes it possible to maintain the mechanical tension state of the winding.

[0113] The different layers of the multilayer stack 20 are now described in more detail.

[0114] The first layer of insulating polymer 201 is based on or made of an electrically insulating polymer used as an insulating material in high-voltage cables. This polymer may be a polymer from the family of extrudable and insulating thermoplastics, for example polyethylene PE, polypropylene (PP), high-density polyethylene (HDPE), low-density polyethylene (LDPE), crosslinked polyethylene (PEr), ethylene-propylene-diene monomer rubber (EDPM), polyoxymethylene (POM), and in particular depending on the composition of the cable 1 whose aging is to be studied. Preferably, this polymer has: - a Young's modulus between 80 MPa and 200 MPa, and / or - flow thresholds less than 20 MPa, and / or - strains at break greater than 500%.

[0115] The polymer is thus particularly suitable for forming a film 200 by the trimming operation.

[0116] The insulating polymer layer comprises at least one portion based on an electrically insulating polymer of high voltage cable. It may comprise a second portion based on a sheath semiconductor material. The assembly studied may in fact comprise sheath semiconductor, the electrical voltage applied during aging being able to be adapted for this.

[0117] The separating layer 204 may be a second layer of insulating polymer, for example from the same film 200. Thus, the same trimming operation forms the intercalary layers for the electrode layers 202, 203. According to another example, the separating layer 204 is a layer based on or made of a polymer distinct from the polymer of the layer 201. Preferably, the separating layer 204 is based on or made of polyimide. For very high voltage studies (typically for voltages greater than or equal to 100 kV), the insulator should be thicker than 100 μm to avoid breakdown. To also avoid increasing the thickness of the separator, a high-performance dielectric material is preferable. Polyimide is a high-performance material, having a high relative electrical permittivity greater than 3.

[0118] The first insulating polymer layer 201 and / or the separating layer 204, preferably each of these layers, has a thickness el, taken along the X direction with reference to [Fig.6A], substantially between 50 μm and 200 μm, preferably a thickness substantially between 70 μm and 150 μm, preferably substantially equal to 100 μm. These thicknesses are particularly suitable for reducing the voltage to be applied while maintaining a representative electromotive force. More particularly, the voltage applied to the assembly for the aging study may then be between 700 V and 20,000 V, for example greater than 5,000 V and / or less than 17,000 V.

[0119] For example, the thickness of the insulation of the 225,000 V cable is 20 mm, which makes an electromotive force E = 11,250,000 V / m. This electromotive force is the non-accelerated force. Keeping this same electromotive force corresponding to the real situation of the cable, if we take an insulator of 70 pm thickness, it will be necessary to apply 787.5 V to have the same force E. For 100 pm thickness, 1,125 V and for 150 pm, 1687.5 V. For the aging test, there is an acceleration factor which will depend on the high voltage retained for the aging study, typically 10,000 V. With an acceleration factor of 10, we arrive at 16,875 V for a 150 pm film.

[0120] The electrode layers 202, 203 may be made of metal, and preferably of aluminum. These layers may have a thickness a2, taken along the X direction with reference to [Fig.6A], substantially between 10 μm and 20 μm.

[0121] When the insulating polymer layer is placed under mechanical tension, preferably the assembly before winding is also under mechanical tension. For this, a removable spray adhesive of the post-it adhesive type can be deposited on the face in contact with the insulating polymer layer to enable mechanical tension to be generated in the electrodes and at the same time possible sliding to prevent tearing of the electrode layers.

[0122] The multilayer stack 20 is wound on itself around the direction A2 to obtain the assembly 2 for example illustrated in [Fig.7]. The assembly 2 may comprise at least two turns, and preferably at least five turns of the multilayer stack 20. This will for example depend on the diameter of the insulating support 21. The insulating support may be a polypropylene tube, for example with a diameter of 16 mm. After winding, the assembly may have a diameter of approximately 25 mm, i.e. 6 stacks. The idea is to minimize the number of stacks to limit winding defects which could cause the capsules to age prematurely.

[0123] This winding can be done on a winding machine, for example semi-automatic, and preferably a winding machine capable of managing the mechanical tension of the insulating layer of several percent deformation (of deformation between 1% and 10%). The stack comprising the insulating polymer layer can in fact be put under tension to reproduce the axial stress state of the cable. The tensioning process can be done by a weight or a roller tensioner in the case where the winding is done on a roller bench.

[0124] Preferably the winding is configured to respect the inside / outside direction of the portion 200a in the initial cable 1. The end of the portion 200a being originally arranged towards the inside of the assembly 2, will thus be wound first to be arranged inside the assembly 2. The aging study will be all the more representative of the original cable 1.

[0125] When winding the cable, the multi-layer stack 20 may be exposed to conditions corresponding to the desired aging study conditions. For example, during winding, the atmosphere can be controlled. The humidity level and / or the presence of oxygen can be controlled. For example, an anhydrous atmosphere can be used to meet the buried conditions of high-voltage cables. An atmosphere without oxygen but with a high humidity level could be used to mimic underwater conditions of high-voltage cables. To mimic buried cable conditions, the atmosphere will be inert (for example under argon) with a humidity level. To mimic aerial cable conditions, the atmosphere will be air including humidity.

[0126] The assembly 2 may further comprise a support 21, for example an electrically insulating support. This support may allow the winding of the multi-layer stack 20, as well as its manipulation; the support 21 may have a transverse dimension d7, for example a diameter, taken along the direction Y with reference to [Fig. 7], greater than or equal to 15 mm, preferably substantially equal to 16 mm.

[0127] According to one example, the assembly 2 has a diameter, taken along the Y direction with reference to [Fig.7], greater than or equal to 20 mm, preferably substantially equal to 24 mm.

[0128] As illustrated for example in [Fig.8], the assembly 2 can be arranged in a capsule 30 configured to electrically power the assembly 2. A cell 3 is thus obtained. For this, the capsule 30 comprises a body 301, a first cap 301 and a second cap. These elements define a closed interior volume 303 in which the assembly 2 is received.

[0129] The capsule 30 is now described in more detail with reference to [Fig.8].

[0130] Inside the closed volume 303, two electrodes 304, 305 may be arranged so as to each connect a separate electrode layer 202, 203 of the assembly 2. The capsule 30 may be configured so as to electrically contact the two electrodes 304, 305 with an external electrical power source. According to one example, electrodes 303, 304 are arranged on either side of the interior volume 303 in the Z direction, or equivalently in the winding direction A2 of the assembly 2. Each electrode may be configured to be compressed against the ends 2a, 2b of the assembly 2, illustrated in [Fig.7], and more particularly the contact portions 202a, 203a. The electrodes 304, 305 are for example made of aluminum.

[0131] Each plug 301, 302 may be electrically conductive, for example made of metal, and in electrical contact, preferably in direct contact, with the corresponding electrode 304, 305. Resumption of contact at the capsule 30 is thus facilitated. The plugs 301, 302 may be made of stainless steel, or preferably based on or made of copper or copper alloy (for example brass).

[0132] The body 300 of the capsule 30 may comprise a first electrically insulating sleeve 300a laterally surrounding the assembly 2 in the plane (x,y). Preferably, the first sleeve extends in the Z direction over a length d10 substantially equal to the assembly formed by the electrodes 304, 305 and the assembly 2. d10 may be greater than or equal to 60 mm, preferably substantially equal to 66 mm. The first sleeve 300a may have a transverse dimension taken in the Y direction with reference to [Fig.8], for example an internal diameter, greater than or equal to 20 mm, preferably substantially equal to 26 mm.

[0133] The body 300 of the capsule 30 may further comprise a second sleeve 300b, for example metallic, laterally surrounding the first sleeve 300a. The second sleeve 300b may extend over the first and second plugs 301, 302. According to one example, the second sleeve 300b is in electrical contact with the second plug 302. Preferably, the second sleeve 300b is made of copper. The thermal conduction by the second sleeve 300b is thus improved. The exposure of the assembly 2 to thermal stress is thus improved during the aging study.

[0134] The body 300 of the capsule 30 may further comprise an electrically insulating collar 306 configured to separate the first cap 301 from the second sleeve 300b. The collar 306 may be arranged around the first sleeve 300a. The collar 306 and the first sleeve 300a may, for example, form a single-piece assembly.

[0135] The first sleeve 300a and the collar 306 may be based on or made of an electrically insulating polymer, preferably polyetheretherketone (commonly referred to as PEEK from the English PolyEtherEtherKeton).

[0136] Preferably, the capsule 30 is configured to define the closed interior volume 303 in a sealed manner. The assembly 2 can thus be placed under a controlled atmosphere, as described previously, in the capsule 30 in order to maintain the desired conditions for the study of aging.

[0137] For this, the second plug 302 can be secured to the body 300, and more particularly to the second sleeve 300b, by brazing. The first plug 301 can cooperate with the body 300, and more particularly the first sleeve 300a, by screwing with complementary threads.

[0138] The first cap 300 can therefore be screwed onto the body 300 until a sealed joint is obtained to close the closed volume 303. For this, one or more seals 307, for example annular seals, can be arranged at the level of the collar 306. The seals 307 can be arranged on either side of the collar 306 in the direction Z. Thus, the first cap 301 comes into abutment against a sealing seal 307 and pushes the collar 306 against the second sleeve 300b by means of a second seal 307.

[0139] One or preferably more cells 3 may be arranged in a housing 40 to form a system 4. The housing 40 is now described in more detail with reference to [Fig.9]. The housing 40 is configured to electrically power the cells 3.

[0140] For this, the housing 40 may comprise a body 400 comprising at least one and preferably several housings 400a, 400b, 400c, 400d, 400e. Each housing may be configured to accommodate a cell 3, and preferably a single cell 3. The body 400 may be based on or made of an electrically insulating material. According to one example, the body 400 is made of bakelite. Thus, the body is electrically insulating and heat resistant. This is therefore particularly advantageous for studying the aging of a cable 1 under thermal stress.

[0141] The housing 40 can be configured to accommodate a number of cells 3 greater than or equal to 50, and preferably greater than or equal to 100. According to one example, the body 400 forms a matrix of housings to accommodate the cells 3, for example a 10 x 10 matrix. The system 4 thus allows the study of a large number of assemblies 2 in parallel.

[0142] The housing 40 may further comprise at least one cover configured to electrically connect the cells 3 to some sort of external power supply 5.

[0143] The housing 40 may comprise a first cover 401 configured to electrically connect each cell 3 in isolation from the other cells 3. Thus, the electrical properties of each cell 3 may be tested for each cell 3 individually. For this, the first cover 401 may comprise several electrical connectors 401a. Each electrical collector 401a may be configured to form an electrical connection for a given cell 3. In the cover 401, the electrical connectors 401a are not electrically connected to each other. The electrical connectors 401a may be separated from each other by an electrically insulating material, for example Bakelite.

[0144] The housing 40 comprises a second cover 402 configured to connect the electrical connectors 401a of the first cover 401 to the external electrical power source 5, for example illustrated in [Fig. 10]. The second cover 402 thus allows contact to be reestablished at the connectors 401a of the first cover 401 and paralleling of the cells 3. For this, the second cover 402 may comprise an electrical connector 402a configured to electrically connect the connectors 401a of the first cover 401 together. The electrical connector 402a may be configured to be electrically connected to the external electrical power source 5. Except for its parts in contact with the electrical connectors 401a and the portion for connection to the external power source external 5, the electrical connector 402a may be electrically isolated from its environment by an electrically insulating material, for example bakelite.

[0145] The housing 40 may further comprise a bottom 403 configured to electrically connect each cell 3 so as to close the electrical circuit with the external power source 5. For this, the bottom 403 may comprise an electrical connector 403a configured to electrically connect the cells 3 together. The electrical connector 403a may be configured to be electrically connected to the external electrical power source 5. Except for its parts in contact with the cells 3, the electrical connector 403a may be electrically insulated from its environment by an electrically insulating material, for example bakelite.

[0146] The electrical connectors 401a, 402a, 403a of the housing 40 are preferably made of copper.

[0147] Some dimensions of the housing 40 are now given, dl 1 is preferably greater than or equal to the height of a cell in the z direction, and preferably substantially equal to 100 mm. dl2, dl3 and dl4 may be equal, for example substantially equal to 15 mm. The housing may have a width in y and a depth in x substantially equal to 400 mm. The housings 400a, 400b... may be spaced apart by a distance along x and / or y substantially equal to 10 mm.

[0148] The method for studying the aging of a high-voltage cable 1 is now described. This method can implement the various objects described previously. More particularly, the method can comprise exposing at least one assembly 2 to an electric current, and preferably several assemblies 2. The electric current can be alternating or direct depending on the types of high-voltage cable 1 and / or depending on the desired aging conditions. The electric current can have a voltage of between 5,000 V and 20,000 V, preferably between 10,000 V and 20,000 V. The external electrical power source 5 can be configured to generate this current. According to one example, the electrical power source 5 is a high-voltage generator.This electric current can be brought to the assembly 2 via the system 4 and the various electrical connectors connecting the external power source 5 to the cell 3 and therefore the assembly 2. The external electrical energy source 5 and the regulated term enclosure can be part of the system 4.

[0149] In addition to exposure to an electric current, the study method may include exposing the assemblies 2 to a thermal stress, and for example a temperature greater than or equal to 60°C, and / or mechanical stresses. For this, the system 4 may be placed in a thermally regulated enclosure 7, as illustrated in [Fig. 10]. The choice of temperature depends on the duration of the study. Because the lower it is, the lower the acceleration and therefore the slower the aging. 60°C is the minimum temperature for the insulating material of the cable, because it is the temperature where there is a mechanical transition that promotes macromolecular mobility in the insulating material (thus accelerating diffusion and chemical aging reactions). This study temperature preferably remains lower than the melting temperature of the polymer of interest

[0150] To study the aging of the assemblies 2, the method may comprise at least one measurement of an electrical property, and in particular of the internal resistance, of the assemblies 2. For this, in the system 4, the second cover 402 of the housing 40 may be removed. The internal resistance of an assembly 2 may be measured via the corresponding connector 401a. The variability between the different cells 3 may therefore be analyzed in situ by minimizing the manipulations of the assemblies 3.

[0151] The study method may comprise the study of a number of assemblies 2 greater than or equal to 50 and preferably greater than or equal to 100. This is particularly advantageous given the duration of the aging studies which may for example last up to five years. In the same study, study conditions may be different between different cells 3, for example the humidity level and / or the presence of oxygen or not. The sealed capsules 30 are particularly advantageous for this purpose. The aging study can therefore take into account a greater number of variables for the prediction of the service life of the high voltage cable. In the same study, several assemblies 2 from the same high voltage cable can be studied under the same conditions. This makes it possible to improve the statistics of the study and therefore to improve the visibility of the result.In the box 40, several assemblies 2 from different high voltage cables can be studied, under the same atmospheric conditions or not.

[0152] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention. The present invention is not limited to the examples previously described. Many other variant embodiments are possible, for example by combining features previously described, without departing from the scope of the invention. In addition, the features described in relation to one aspect of the invention may be combined with another aspect of the invention.

Claims

Claims

1. Method of manufacturing an assembly (2) for studying the aging of a high voltage cable (1), the method comprising: • a formation of a multilayer stack (20) comprising the at least partial superposition of: • a first layer called electrode (202), based on an electrically conductive material, • at least one layer based on an electrically insulating polymer, called the first layer of insulating polymer (201), • a second layer called an electrode layer (203), based on an electrically conductive material, so that the first layer of insulating polymer (201) is arranged between the first (202) and second (203) electrode layers, and • a separating layer (204) at least partly superimposed with the assembly formed by the first (202) and second (203) electrode layers and the first insulating polymer layer (201), • a winding of the multilayer stack (20) at least partly on itself around a longitudinal direction (A2) to form the assembly (2).

2. A method according to the preceding claim, further comprising: • a supply of a portion (10) of high-voltage cable (1) comprising a core (11) extending in a main extension direction (Al) of the cable (1) and surrounded around said direction by a material (13) based on the electrically insulating polymer, • a formation of a film (200) based on the electrically insulating polymer, by trimming the portion (10) of high voltage cable (1) around the main extension direction (Al) of the cable (1), at least one portion (200a) of the film (200) being used during the formation of the multilayer stack (20).

3. A method according to any preceding claim, comprising, prior to forming the film (200), aging the high voltage cable (1) comprising exposing the portion (10) of cable (1) to an electric current, and / or wherein the portion (10) of cable (1) is derived from a previously used high voltage cable (1).

4. A method according to any preceding claim, wherein the winding of the multi-layer stack (20) is carried out under an atmosphere of controlled humidity level and / or controlled oxygen level.

5. A method according to any preceding claim, further comprising, prior to forming the multi-layer stack (20), selecting the portion (200a) of the film (200) for forming the multi-layer stack (20), according to a corresponding position of the electrically insulating polymer-based material in the high voltage cable (1).

6. Method according to any one of the preceding claims, comprising, before the formation of the film (200): • straightening a lateral periphery (100) of the portion (10) of cable (1), and / or • straightening at least one end (10a, 10b) of the portion (10) of cable (1).

7. Assembly (2) for studying the aging of a high-voltage cable (1), characterized in that the assembly (2) comprises a multilayer stack (20) at least partly wound on itself around a longitudinal direction (A2), the multilayer stack (20) comprising: • a first (202) and a second (203) layer, called electrode layers, based on an electrically conductive material, • a first layer based on an electrically insulating polymer of high-voltage cable, called first insulating polymer layer (201), and arranged between the first (202) and second (203) electrodes, and • a separating layer (204) configured to electrically insulate the first (202) and second (203) electrode layers from each other, in the wound multilayer stack (20).

8. Assembly (2) according to the preceding claim, in which at least one of the first (202) and second (203) electrode layers protrudes at least partly from the first insulating polymer layer (201) and the separating layer (204) in the longitudinal direction (A2).

9. Assembly (2) according to the preceding claim, in which the first (202) and second (203) electrode layers are arranged offset from the first insulating polymer layer (201) and the separating layer (204) in the longitudinal direction (A2), so that: • the first electrode layer (202) protrudes from the first insulating polymer layer (201) and the separating layer (204) on a first side (20a) of the multilayer stack (20) relative to the longitudinal direction (A2), without protruding on a second side (20b) of the multilayer stack (20) opposite the first side (20a), • the second electrode layer (203) protrudes from the first insulating polymer layer (201) and the separating layer (204) on the second side (20b) of the multilayer stack (20), without protruding on the first side (20a).

10. Assembly (2) according to any one of the three preceding claims, in which the first layer of insulating polymer (201) has a thickness of between 50 pm and 200 pm.

11. Assembly (2) according to any one of the four preceding claims, in which the separating layer (204) is a second layer based on the electrically insulating polymer of high voltage cable, called second layer of insulating polymer (204a).

12. Assembly (2) according to any one of claims 7 to 10, in which the separating layer (204b) is a polyimide-based layer.

13. Cell (3) for studying the aging of a high-voltage cable (1), comprising: • the assembly (2) according to any one of claims 7 to 12, and • a capsule (30) configured to electrically supply the assembly (2), the capsule (30) comprising: • a body (300), a first cap (301) and a second cap (302), defining a closed interior volume (303), the capsule (30) being configured to receive the assembly (2) in the closed interior volume (303), • two electrodes (304, 305) each configured to connect an electrode layer (202, 203) distinct from the assembly (2).

14. Cell (3) according to the preceding claim, in which the body (300) and the first (301) and second (302) plugs are configured to define the closed interior volume (303) in a sealed manner.

15. Cell (3) according to any one of the two preceding claims, in which, in the assembly (2), at least one of the first (202) and second (203) electrode layers protrudes at least partly from the first insulating polymer layer (201) and the separating layer (204) in the longitudinal direction (A2), so as to be in electrical contact with the corresponding electrode (304, 305) of the capsule (30), arranged opposite said electrode layer (202, 203).

16. Cell (3) according to any one of the three preceding claims, wherein each plug (301, 302) is electrically conductive and is electrically connected with an electrode (304, 305) of the capsule (30), and wherein the body (300) of the capsule (30) is configured to electrically insulate the first (301) and second (302) plugs from each other.

17. Cell (3) according to the preceding claim, in which the body (300) of the capsule (30) comprises: • a first electrically insulating sleeve (300a) laterally surrounding the assembly (2), • a second metal sleeve (300b) laterally surrounding the first sleeve (300a), the second sleeve being in electrical contact with the second cap (302), and • an electrically insulating collar (306) separating the first cap (301) from the second sleeve (300b).

18. System (4) comprising several cells (3) according to the five preceding claims and a housing (40) configured to receive and electrically power the cells (3).

19. System (4) according to the preceding claim, comprising a number of cells (3) greater than or equal to 50, preferably greater than or equal to 100.

20. System (4) according to any one of the two preceding claims, wherein the housing (40) comprises: • a first cover (401) comprising several electrical connectors (401a), the electrical connectors (401a) being configured to each electrically connect at least one cell (3), separately from the at least one cell (3) connected by the other electrical connectors (401a), and • a second cover (402) configured to electrically connect together the electrical connectors (401a) of the first cover (401) to an external electrical power source (5).

21. Method for studying the aging of a high voltage cable (1) comprising: • exposure of at least one assembly (2) according to any one of claims 7 to 12, to an electric current, • at least one measurement of an electrical property, and for example of the internal resistance, of at least one assembly (2) so as to obtain data representative of the aging of a high voltage cable (1).

22. Method according to the preceding claim, in which the electric current has a voltage between 700 V and 17,000 V.

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