WO2013076416A1

WO2013076416A1 - High-voltage electrical cable suitable for extreme conditions

Info

Publication number: WO2013076416A1
Application number: PCT/FR2012/052675
Authority: WO
Inventors: Mohamed EL IDRISSI
Original assignee: Axon Cable
Priority date: 2011-11-23
Filing date: 2012-11-20
Publication date: 2013-05-30
Also published as: FR2982993B1; EP2783372A1; FR2982993A1; EP2783372B1

Abstract

The present invention relates to a high-voltage electrical cable including a central conductor (1) made of copper or a copper alloy coated with nickel, and at least one main insulating material layer (2) arranged around the central conductor (1), said insulating material layer consisting of an extruded thermoplastic material selected from among poly(ether-ketone), poly(ether-ketone-ether-ketone-ketone), and the mixtures thereof. The invention also relates to the use of the cable in the aerospace and/or nuclear and/or scientific research and/or oil research fields.

Description

HIGH VOLTAGE ELECTRIC CABLE ADAPTED TO CONDITIONS

EXTREME

The present invention relates to the field of high voltage electrical cables resistant to extreme conditions for aerospace, nuclear, scientific research and / or petroleum research.

Some areas of application require extreme conditions of use. The oil field is looking for materials that can withstand high temperatures (200 ° C and +) combined with resistance to high pressures (300 to 700 bar for example) and excellent resistance to chemicals (fuels, hydrocarbons, etc.). .).

The field of scientific research (particle acceleration, fusion or nuclear fission, etc.) focuses on the radiation resistance of polymers associated with resistance to cryogenic temperatures and a very low level of degassing.

Nuclear power plant applications are looking for very high radiation resistance and insulating quality for low thicknesses.

The space domain requires the combination of weight gain, very good resistance to radiation, resistance to higher and higher temperatures (250 ° C and higher), high intensity and low outgassing. The requirement of low outgassing is very important because the applications for research or space domain operate in a high vacuum environment (1 to 10-12 mbar). This property refers to the amount of volatile compounds released by a component or material when subjected to high vacuum. The condensation of these compounds on sensitive organs such as sensors or optics can cause measurement errors or malfunctions. The spatial standard ECSS-Q-70-02 is used to characterize the degassing of a material or component. According to this standard, the content of condensable volatile materials collected (CVCM) must be lower than at 0.1% and the total mass loss of the material excluding water (RML) must be less than 1%.

Increasing the power of equipment also means that new generation cables may be able to carry higher and higher voltages. These so-called high voltage applications have become commonplace in areas such as space, military or research. Radiation is known to be a critical aging factor in the space or nuclear fields. These different ionizing radiations are an integral part of these applications and can reach very high doses in some cases (several hundred megarads).

Finally, the maximum temperature of use is also a very important criterion. Space or nuclear applications may require temperatures above 250 ° C. This is also the case for aeronautical or military applications. Another trend observed is that of using the wires or cables at their thermal limit not by the external environment but rather by heating generated by the passage of a high current.

All these sectors are seeking property whose limits are constantly pushed back. In addition, the development of a solution common to all these applications supposes to take into account the combined effect of these various factors which are the temperature, the radiations and the tension.

It is therefore necessary to be able to manufacture a cable capable of meeting all the requirements of the fields mentioned above; to know in particular:

- The nuclear field

- The field of scientific or fundamental research

- The field of aerospace

- The oil field, in particular prospecting

- And all areas with similar requirements.

The cable consists of a combination of materials of different types (metal and polymer) which together must be able to withstand temperatures between -150 ° C and 280 ° C, a dose of radiation up to 200 Rad, operating voltage up to 5,000 volts. In addition, the cable must meet the degassing standards of space domain but also keep some flexibility especially to see support mechanical movements of small amplitude bends during operation (between 1 and 20 ° for example).

In particular, it is difficult to find an insulating material to meet these extreme requirements. Indeed, polymer materials are very sensitive to high temperatures.

Some thermosetting materials such as elastomers and silicones are able to withstand high temperatures, but they do not meet all the requirements and more particularly those concerning degassing and low temperatures (between -50 ° C and -150 ° C) .

In addition, although polyimide thermosetting resins are generally also resistant to high temperatures and extreme conditions, they are difficult to implement to manufacture a cable. Indeed, for son from a certain diameter, they can only be used in ribbon form to have sufficient cohesion with the central conductor and thus to avoid delamination when using the cable, it is in general it is necessary to add an adhesive or a coating which itself does not withstand these extreme conditions.

Ultra-polymers, especially thermoplastics, have excellent electrical and mechanical behavior, but are limited in temperature to 260 ° C. Radiation resistance being an intrinsic property of the material, some high performance thermoplastics are known to have good resistance to ionizing radiation. However, they also often show significant stiffness with risks of fragility when exposed to very low temperatures.

Among these, it is known that thermoplastic resins of the polyetheretherketone type can withstand temperatures of up to 260 ° C according to the manufacturers' indications. Thus, the patent application EP 0 197 227 describes an electrical cable especially for aerospace use whose insulating material may be based on polyetheretherketone. However it should be noted that the cable described in this document can be coated with a varnish that does not withstand temperatures of up to 280 ° C. Indeed, as indicated in this document page 4 line 2, the varnish layer must withstand only a temperature of at most 150 ° C. In addition, the cable comprises a second insulating layer based on band of polyimide ribbon resins. To allow bonding of the layers of the strip between them, this layer is provided with a thermoplastic coating of copolymers of ethylene and fluorinated propylene (page 4, line 14 - 16). Or this type of material is not resistant to radiation .

Furthermore, the inventors have discovered that the polyetheretherketone resins described in this document and polyetherketoneketoneextruded or in the form of a coating did not have a sufficient thermal resistance at 280.degree. C. or did not exhibit sufficient mechanical strength after thermal aging at such temperatures.

For all these reasons the electric cable described in this document was not usable under extreme conditions, in particular high temperatures. The need therefore remains to be able to manufacture a high-voltage electrical cable resistant to such extreme conditions.

Surprisingly, the inventor has discovered that certain insulating materials belonging to the same family as the polyetheretherketone and polyetherketoneketone thermoplastic resins, could be used in high-voltage cables intended for extreme conditions without electrical failure.

The inventor has also discovered that to obtain the most advantageous properties the central conductor had to be made of a particular conductive material coated with nickel. This coating could be much thinner than usually recommended while providing effective corrosion protection for up to 280 ° C. This small thickness thus avoids excess conductivity loss of the conductive material especially when the latter is in the form of alloy.

Finally, the inventor has discovered a particularly interesting construction of the high-voltage electric cable, in particular by using a multilayer insulation, which allows it to be the most efficient under extreme conditions.

The present invention therefore relates to a high-voltage electrical cable comprising a central copper conductor coated with nickel or copper alloy coated with nickel and at least one main layer of an insulating material disposed around the central conductor, said layer of insulating material being formed by an extruded thermoplastic selected from polyetherketones, polyetherketoneetherketone ketones and mixtures thereof. For the purposes of the present invention, high-voltage cable is understood to mean a cable capable of withstanding voltages greater than 1000 V AC or 1600 V DC, without exceeding 50 000 V. Advantageously, the cable is capable of withstanding voltages higher than 3500V (medium voltage), more preferably a voltage of less than 10,000 V, still more preferably a voltage of about 5000V.

The center conductor or conductive core must fulfill the conductivity requirements combined with the thermal resistance. The purpose of the driver is to allow the passage of a significant amount of electricity characterized by a high amperage. Indeed, in the context of the present invention, the conductor can receive a voltage of up to 5 kV and an amperage of up to 12 A. The cable according to the invention must have the most optimized mass possible. It is not possible to use materials with too low conductivity which would therefore require oversizing the central conductor. Thus only copper and copper alloys fulfill these requirements. Indeed, other metals such as nickel alone, for example, despite their excellent thermal resistance, can not be used in the cable according to the invention. because of their very low electrical conductivity. Aluminum, on the other hand, is a low weight metal, but unusable for use at high temperatures because of the high elongation rate from 260 ° C. In addition, this material is characterized by a very low conductivity (25-30% of IACS, International Annealed Copper Standard, the electrical conductivity unit for metals and alloys, the reference of which is copper: 100% d Thus, the IACS value of 100% corresponds to a conductivity of 5.8 MS / m 2) and shows difficulties in being connected.

The copper alloy must of course meet the new environmental standards such as those of the European directive RoHS (2002/95 / CE) revised in 2011. Advantageously, the copper alloy comprises at least one alloy element selected from iron, aluminum and copper. non-hexavalent chromium, tin, magnesium, zirconium and their mixture, in particular chromium, zirconium and their mixture, especially a mixture of chromium and zirconium. Advantageously, the copper alloy is free of cadmium, cobalt, lead, beryllium and / or mercury. Even more advantageously, it comprises between 0 and 1.5% by weight of iron, between 0 and 1% by weight of non-hexavalent chromium, between 0 and 0.5% by weight of tin, between 0 and 1% by weight of zirconium and between 0 and 0.5% by weight of magnesium relative to the total weight of the alloy and is free of cadmium, cobalt, lead, beryllium and Mercury. Even more advantageously, the copper alloy is a high-performance copper alloy comprising chromium in a content of up to 1% and zirconium in a content of up to 1% marketed by the company Fisk Alloy under the Percon ™ 24 name.

Copper and copper alloys have the disadvantage of being very sensitive to oxidation. It is therefore necessary to coat them with a coating resistant to oxidation by chemical or electrolytic means well known to those skilled in the art.

Nickel plating is in a preferred way a coatings capable of withstanding high temperatures while keeping good mechanical properties. Indeed, a silver coating weakens if it is exposed for a long time at high temperatures. After 100 h, the silver begins to oxidize in the interfacial zone. After 2000h, the oxidation layer has grown and the remaining silver forms coalescences. Copper or copper alloy must be coated with nickel to prevent corrosion.

Unfortunately nickel (25% IACS) has an impact on the conductivity of the conductor, especially when the latter is a copper alloy which by definition already has a lower conductivity than pure copper.

It has been surprisingly discovered by the inventor that the best compromise between corrosion prevention (which is particularly important for aerospace uses due to the presence of atomic oxygen), and conductivity is a thickness of nickel coating on the central conductor between 7 and 11% by weight, preferably 10% by weight according to ASTM B355. In the prior art, preference was given to a coating of at least 27% by weight. Indeed, during prolonged exposure to high temperatures, there is a migration of nickel into the copper. This migration can lead to a reduction of the nickel layer and thus expose the driver to the risk of oxidation.

Advantageously, the central conductor is made of nickel-coated copper alloy, said alloy advantageously comprising between 0 and 1.5% by weight of iron, between 0 and 1% by weight of non-hexavalent chromium, between 0 and 0.5% by weight. of tin, between 0 and 1% by weight of zirconium and between 0 and 0.5% by weight of magnesium relative to the total weight of the alloy and is free of cadmium, cobalt, lead, beryllium and Mercury in particular a high performance copper alloy comprising chromium in a content of up to 1% by weight and zirconium in a content of up to 1% by weight marketed by Fisk Alloy under the name Percon ™ 24.

The central conductor may consist of one or more strands, preferably several strands. Indeed the use of several strands makes it possible to obtain different constructions which can improve the flexibility of the final cable. The number of strands also has an impact on the electrical conductivity in general: the more strands a conductor contains, the better its mechanical behavior (in particular the resistance to fatigue cycles and the flexibility) but its electrical performances are a little diminished. In addition, the method of assembling the strands that form the final conductor may have some impact on the electrical phenomena involved in the high voltage (especially in terms of generation of corona effect).

In general if the central conductor is not mono-stranded, it can contain 7, 19, 27, 37, 45, and 61 strands and 7 * 7. Advantageously, the central conductor according to the present invention contains 19 or 37 strands, still more advantageously 19 strands. Depending on the number of strands, the following assemblies can be used: twist, concentric (in particular 19, 61 or 37 strands), Equilay, semi-concentric, Unilay (in particular 19 strands) or Ropelay (in particular for 7 * 7 strands). Advantageously, the central conductor contains 19 strands assembled in Unilay or 37 strands assembled concentrically. These two constructions show improved resistance to thermal aging in the short and long term. Even more advantageously the central conductor contains 19 strands assembled in Unilay. Indeed in the latter case, the life of the flexibility of the cable is improved and the corona effect is reduced by the geometric construction of the driver approaching a perfect circle.

Thus, in a particularly advantageous embodiment of the invention, the central conductor is made of copper alloy, in particular Percon ™ 24 marketed by Fisk Alloy, coated with 10% nickel according to the 19 strand construction assembled in Unilay. This construction is characterized by very good conductivity (> 70% IACS).

In an advantageous embodiment, the central conductor has a cross section of between 0.05 and 22 mm ² , advantageously between 0.5 and 4.5 mm ² , more advantageously between 3.5 and 4.4 mm ² , and even more advantageously between 3.8 and 4.1 mm ² . This allows the cable to maintain flexibility while having the necessary conductivity. Thus, on average, the center conductor has a section of 3.9 mm ² .

Advantageously the central conductor can withstand continuous exposure to temperatures above 300 ° C without creep and maintaining excellent mechanical properties and very good conductivity.

The insulating material used for the manufacture of high voltage electrical cables is a dielectric material that is to say that does not conduct electricity. The principle function of the dielectric is to maintain electrical insulation performance between the main conductor of the cable and the conductive elements (at ground potential) for a definite time and in a defined environment.

In the context of the present invention, the main layer of insulating material disposed around the central conductor is formed by an extruded thermoplastic chosen from polyetherketones or PEK (more particularly PEEK HT G22 manufactured by Victrex), polyetherketoneetherketoneketones or PEKEKK ( more particularly reference PEEK ST G45 manufactured by Victrex) and their mixture. Advantageously, it is a polyetherketoneetherketoneketone and in particular that sold by Victrex under the name PEEK ST G45. Indeed, the polyetherketoneetherketoneketone has a higher temperature resistance than the polyetherketones. In addition they are easier to implement.

Although these materials are indicated by the manufacturers as being usable only at a maximum temperature of 250 ° C, the inventor has surprisingly found that they can be used in the case of the present invention up to a maximum of 250 ° C. temperature of at least 280 ° C.

In addition, the inventor has demonstrated that when they were used as a layer of main insulating material in the manufacture of a high voltage electrical cable, these materials were able to withstand up to thermal stresses of: - 280 ° C for 2000 hours for static applications or for low amplitude folding movements (between +/- 1 ° and +/- 10 ⁰ ).

- 280 ° C for 500 hours for dynamic applications requiring large mechanical bends (up to +/- 90 ⁰ ).

This is quite surprising since thermoplastic polymers belonging to the same family such as polyetherketoneketone (PEKK) and polyetheretherketone (PEEK) which according to the manufacturers can also be used at a maximum temperature of 250.degree. C. have been found to possess insufficient thermal resistance (polyetheretherketone such as for example PEEK 151G sold by Victrex) or mechanical strength after insufficient thermal aging (polyetherketoneketone such as for example the OXPEKK CE marketed by Arkema) when they were in the form extruded or even in the form of a coating (Polyetheretherketone coating) which causes the appearance of cracks which therefore adversely affect their role of insulator.

Advantageously, the main layer of insulating material has a thickness of between 0.1 and 3 mm, advantageously between 0.15 and 2 mm, more advantageously between 0.2 and 1.5 mm, even more advantageously between 0.5 and 1 mm, in particular the thickness is 1 mm. This thickness is sufficient to isolate the central conductor while not being too thick so that the cable can keep some flexibility.

In a second embodiment of the invention, the cable according to the invention comprises a layer of additional insulating material around the main layer of insulating material, said layer of additional insulating material being formed by a thermosetting polymer resistant to temperatures that can up to 280 ° C, in particular a thermosetting polymer polyimide or polybenzimidazole. In the case of polybenzimidazole, the layer of material is advantageously in the form of a film. In the case of polyimides, the layer is advantageously in the form of ribbon. Advantageously, the layer of additional insulating material is polyimide in the form of ribbon.

Indeed, the inventor has discovered that this additional layer of insulating material avoids the problems that may exist at the polymer / metal interface when the cable is surrounded by a metal shielding material. Indeed, the differences in thermal conductivity between a metal component and a thermoplastic insulating material that are both in close contact can create local stresses that can promote the formation of cracks. These cracks can cause a dielectric breakdown by contributing to the phenomenon such as the electrical tree. Since the heat comes mainly from the outside, especially when the cable is intended to be used near an engine, this additional layer of insulating material should rather be located around the main layer of insulating material, and in particular between the main layer of insulating material and the outer layer of shielding material.

In the context of the present invention, the polyimide, in particular in tape form, contains no adhesive, the cohesion of this layer with the central conductor being provided by the thermoplastic insulating main material. Advantageously, the polyimide is a ribboned polyimide sold by the company Dupont De Nemours under the name Kapton HN, in particular Kapton 200H.

Advantageously, the layer of additional insulating material comprises between one and four wound polyimide ribbon layers, advantageously two or three layers of banded polyimide, and even more advantageously two layers of banded polyimide, with a coverage of between 25 and 75%, advantageously of 50%. . Advantageously, the layer of additional insulating material comprises two layers of polyimide tape with a coverage of 50%, in particular that marketed by Dupont De Nemours under the name Kapton HN, in particular Kapton 200H. Advantageously, the layer of additional insulating material has a thickness between 15 and 75 μητι, more preferably between 20 and 60 μm, still more preferably between 25 and 50 μm, in particular about 50 μm.

In a third embodiment of the invention, the cable according to the present invention comprises an outer layer of metal shielding material, preferably made of the same material as the central conductor. The outer layer of metal shielding material can deal with the problems caused by electromagnetic interference. It is therefore advantageous to add such a layer to the cable according to the present invention. There is a wide variety of models and configurations of shielding material. This layer can in particular be braided, wound in the form of sheets, a combination of sheets and braiding or in helical form. Advantageously, the outer layer of metal shielding material of the cable according to the invention is braided. Indeed, the inventor has discovered that this configuration allows a very effective shielding, in particular as a shield against radiation, while maintaining sufficient flexibility during its lifetime.

The metal shielding material to be used to make this outer layer must indeed be a good shield against radiation. The best metal material solution to be used to manufacture this outer shielding layer must be a compromise between good mechanical properties, particularly with regard to folding and flexibility, and good shielding efficiency, particularly as a barrier. that barrier against radiation. In particular, it may be copper coated with nickel or a copper alloy coated with nickel. Advantageously, it is a copper alloy coated with nickel. The copper alloy must of course meet the new environmental standards such as those of the European directive RoHS (2002/95 / CE) revised in 2011. Advantageously, the copper alloy comprises at least one alloy element selected from iron, aluminum and copper. non-hexavalent chromium, tin, magnesium, zirconium and their mixture, in particular chromium, zirconium and their mixture, especially a mixture of chromium and zirconium. Advantageously, the copper alloy is free of cadmium, cobalt, lead, beryllium and / or mercury. Even more advantageously, it comprises between 0 and 1.5% by weight of iron, between 0 and 1% by weight of non-hexavalent chromium, between 0 and 0.5% by weight of tin, between 0 and 1% by weight of zirconium and between 0 and 0.5% by weight of magnesium relative to the total weight of the alloy and is free of cadmium, cobalt, lead, beryllium and Mercury. Even more advantageously, the copper alloy and a high-performance copper alloy comprising chromium in a content of up to 1% and zirconium in a content of up to 1% marketed by the company Fisk Alloy under the denomination Percon ™ 24. Advantageously, the nickel coating thickness is between 7 and 11% by weight, preferably 10% by weight according to ASTM B355.

Advantageously, the shielding material is the same material as that of the central conductor, which makes it possible to obtain a shielding layer having good temperature resistance and good conductivity for grounding.

In a fourth embodiment of the invention a layer of intermediate insulating material is interposed between the central conductor and the main layer of insulating material, said layer of intermediate insulating material being formed by a thermosetting polymer resistant to temperatures up to at 280 ° C, in particular a thermosetting polymer polyimide or polybenzimidazole. In the case of polybenzimidazole, the layer of material is advantageously in the form of a film. In the case of polyimides, the layer is advantageously in the form of ribbon. Advantageously, the layer of additional insulating material is polyimide in ribbon form. Indeed, since the cable is a high voltage cable, it is possible that there is a sharp increase in the temperature at the central conductor when used at high intensities. However, as indicated above, the differences in thermal conductivity between a metal component and a thermoplastic insulating material that are both in close contact can create local stresses that can promote the formation of cracks. These cracks can cause a dielectric breakdown by contributing to the phenomenon such as the electrical tree. This intermediate layer of thermosetting insulating material makes it possible to avoid this type of problem.

In the context of the present invention, the polyimide, in particular in tape form, contains no adhesive, the cohesion of this intermediate layer with the central conductor being provided by the thermoplastic insulating main material. Advantageously, the polyimide is a ribboned polyimide sold by the company Dupont De Nemours under the name Kapton HN, in particular Kapton 100H.

Advantageously, the layer of intermediate insulating material comprises between one and four layers of wound ribbon polyimide, advantageously two or three layers of banded polyimide, and even more advantageously two layers of banded polyimide, with a covering of between 25 and 75%, advantageously of 50. %. Advantageously, the layer of intermediate insulating material comprises two layers of polyimide tape with a recovery of 50%, in particular that marketed by Dupont De Nemours under the name Kapton HN, in particular Kapton 100H.

Advantageously, the layer of intermediate insulating material has a thickness of between 15 and 75 μm, more advantageously between 20 and 60 μm, more advantageously between 25 and 50 μm, in particular about 25 μm.

In a fifth embodiment of the invention the intermediate layer of insulating material and the additional layer of insulating material are both present in the cable according to the present invention in order to avoid problems of dielectric breakdown, that the temperature comes from outside or inside the driver. Indeed, the inventor has discovered that this construction is more advantageous to avoid dielectric breaks at very high temperatures. Advantageously, the intermediate layer of insulating material and the additional layer of insulating material are manufactured using the same insulating material, in particular polyimide. Advantageously they have different thicknesses, the additional layer having a thickness greater than the intermediate layer. Advantageously, the thickness of the intermediate layer is 25 μm and the thickness of the additional layer is 50 μm.

In a sixth embodiment of the invention the cable comprises the central conductor, the intermediate layer of insulating material disposed around the central conductor, the main layer of insulating material disposed around the intermediate layer, the additional layer of insulating material arranged around the main layer and the outer layer of shielding material disposed around the additional layer.

In a seventh embodiment of the invention, the cable according to the invention comprises an intermediate semiconducting layer interposed between the main layer of insulating material or the layer of additional insulating material if the latter is present and the outer layer of insulating material. shielding.

This semiconductor layer is intended to evacuate the electrostatic discharges due to the friction between the shielding layer and the layer or layers of insulating material, so that they do not reach the central conductor. This layer therefore makes it possible in particular to improve the service life of the high-voltage cable. Without this layer, the cable according to the present invention already has a good life. However, this layer has an additional advantage.

The material used for this semiconductor layer must have excellent elasticity so that it can follow the movement of the cable but without leaving the insulation. It is generally made from a polymer material loaded with a conductive filler. As before, this semiconductor layer must withstand the extreme conditions of use of the cable and therefore the material The polymer of which it is made must in particular withstand very high temperatures. This layer may be made of thermosetting polymer or thermoplastic polymer resistant to very high temperatures. Advantageously, the semiconductor layer is a polyimide ribbon loaded in the mass by a charge advantageously chosen from carbon black or carbon nanotubes. It may be in particular the material sold by Dupont De Nemours under the name Kapton 100XC10E5 or Kapton 100XC10E7.

Thus, in this particular embodiment of the invention, the cable according to the invention comprises

or the central conductor, the main layer of insulating material disposed around the conductor, the intermediate semiconducting layer and the outer layer of shielding material disposed around the semiconductor layer; or the central conductor, the intermediate layer of insulating material disposed around the central conductor, the main layer of insulating material disposed around the intermediate layer, the intermediate semiconducting layer and the outer layer of shielding material arranged around the semiconductor layer. - conductor;

or the central conductor, the main layer of insulating material disposed around the central conductor, the additional layer of insulating material disposed around the main layer, the intermediate semiconducting layer and the outer layer of shielding material arranged around the semiconductor layer. - conductor;

or the central conductor, the intermediate layer of insulating material disposed around the central conductor, the main layer of insulating material disposed around the intermediate layer, the additional layer of insulating material disposed around the main layer, the intermediate semiconducting layer and the outer layer of shielding material disposed around the semiconductor layer. This latter configuration is particularly advantageous. The cable according to the present invention is able to withstand for at least 2000 hours without electrical failure:

operating temperatures between -50 ° C and 280 ° C,

- resting temperatures between -100 and 280 ° C,

a radiation dose of up to 1000 Megarads, advantageously of up to 200 Megarads,

an operating voltage of up to 10000 V advantageously up to 5000V and

in operation of the mechanical movements of flexions with an amplitude of between 1 and 20 °.

The cable according to the present invention is manufactured by techniques well known to those skilled in the art. In particular the main insulation layer and extruded around the central conductor or the intermediate layer of insulating material if the latter is present.

Advantageously, the intermediate layer of insulating material, when present, is wound around the central conductor. Also, advantageously, the additional layer of insulating material, when present, is wrapped around the main layer of insulating material. It is the same for the semiconductor layer when it is present which is wound around the additional layer.

Finally, the outer layer of metal shielding is advantageously braided on the cable. The present invention also relates to the use of the cable according to the present invention in the petroleum field, in particular for prospecting equipment, aerospace, nuclear particularly for the areas close to the reactor, scientific research requiring extreme conditions, petroleum research, aeronautics and / or the military field. The present invention will be better understood with reference to the following figures and examples.

FIG. 1 is an exploded perspective view of the first embodiment of the cable according to the invention.

FIG. 2 is an exploded perspective view of the third embodiment of the cable according to the invention.

FIG. 3 is an exploded perspective view of the sixth embodiment of the cable according to the invention.

FIG. 4 is an exploded perspective view of the seventh embodiment of the cable according to the invention.

The cable according to the invention illustrated in FIG. 1 comprises the main layer of insulating material (2) made of thermoplastic material extruded around the copper alloy core (1) marketed by the company Fisk Alloy under the name Percon 24 coated with 10 % nickel and having the Unilay 19 strand configuration.

The cable according to the invention illustrated in FIG. 2 comprises the main layer of insulating material (2) made of polyetherketoneetherketoneketone sold by Victrex under the name PEEK STG 45 extruded around the central conductor (1) made of copper alloy marketed by the company Fisk Alloy under the name Percon 24 coated with 10% nickel configuration Unilay 19 strands. It further comprises the additional layer (3) of thermosetting polyimide insulating material sold by Dupont De Nemours under the name Kapton 200H which is wound around the main layer of insulating material (2) and the outer layer of shielding (5). copper alloy sold by the company Fisk Alloy under the name Percon 24 coated with 10% nickel braided around the additional layer of insulating material (3).

The cable according to the invention illustrated in FIG. 3 comprises, in addition to the layers present in the cable illustrated in FIG. 2, the intermediate layer of polyimide thermosetting insulating material (4) marketed by the Pont du Pont company. Nemours under the name Kapton 100H wrapped around the central conductor (1). The main layer of the insulating material (2) made of polyetherketoneetherketoneketone sold by Victrex under the name PEEK STG 45 is thus extruded around this intermediate layer (4).

Finally, the cable according to the invention illustrated in FIG. 4 comprises, in addition to the layers present in the cable illustrated in FIG. 3, the layer of dielectric material (6) arranged around the additional layer (3), the shielding layer ( 5) being braided on this layer of dielectric material (6).

Example 1: selection and evaluation of the material of the central conductor

To choose the material of the central conductor the tests were carried out on a mono-strand configuration. The materials tested were either copper or a particular copper alloy (the Percon 24 marketed by Fisk Alloy) with different thicknesses of nickel coating. These different materials are found in Table 1 below:

Table 1: materials tested in mono strand

AWG Material Coating Diameter Section

(mm) (mm ² )

2401 Percon 24 27% Ni 0.511 0.163

2401 Percon 24 10% Ni 0.511 0.163

2401 Percon 24 7% Ni 0.511 0.163

2401 Copper 27% Ni 0.511 0.163

coated with

nickel (NPC)

2401 Copper 1.5% Ni 0.511 0.163

coated with

nickel (NPC) The following tests were carried out in order to choose the most suitable material: mechanical characterization test (dimension measurement (D), alternating flexural strength (RFA) according to ASTM B470, elongation and breaking load (A & CR) ) according to FED STD 228 Method 3211 and metallographic (SM) according to ESCC 3901) and electrical (linear resistance (RL) according to ASTM B193), thermal critical test (thermal stability (ST) which corresponds to aging at short term, thermal aging (VT) which corresponds to long-term aging). For thermal characterization, mechanical and electrical tests are carried out after storing the materials at a given temperature for a given time and the results are compared with those obtained initially to verify if these characteristics have been modified.

The test results are summarized in Table 2 below: Table 2: Test results

Type Requirements Results

of

test

D 0.511 mm +/- 0.005 27% Ni Percon24: 0.508

10% Ni Percon24: 0.507

7% Ni Percon 24: 0.513

NPC 27% Ni: 0.513

NPC 1.5% Ni: 0.508

LR 27% Ni Percon24: 136.5Q / km +/- 27% Ni Percon24: 135.23 Ω / km 10% 10% Ni Percon24: 109.59 Ω / km

10% Ni Percon24: 109.73Q / km +/- 7% Ni Percon 24: 102.56 Ω / km 10% NPC 27% Ni: 107.79 Ω / km

7% Ni Percon 24: 110 Ω / km +/- NPC 1.5% Ni: 87.36 Ω / km

10%

NPC 27% Ni: 120 Ω / km maximum

NPC 1.5% Ni: 88 Ω / km +/- 10%

A & CR 27% Ni Percon24: 450 MPa & 6% 27% Ni Percon24: 534.57 MPa & mini 7.02% 10% Ni Percon24: 10% Ni Percon24: 557,83MPa &

414 MPa & 6% min 4.34%

7% Ni Percon 24: 7% Ni Percon 24: 476, llMPa & 414 MPa & 6% mini 7.66%

NPC 27% Ni: NPC 27% Ni: 301.92MPa & 270MPa & 15% mini 26.25%

NPC 1,5% Ni: NPC 1,5% Ni: 261,17MPa & 250MPa & 20% mini 26,47%

RFA about 100 cycles 27% Ni Percon24: about 116 cycles

10% Ni Percon24: about 67 cycles

7% Ni Percon 24: about 67 cycles

NPC 27% Ni: about 43 cycles NPC 1.5% Ni: about 35 cycles

SM 27% Ni Percon24: thickness 40pm 27% Ni Percon24: 50.43 to 50.54 mini pm

10% Ni Percon24: thickness 10% Ni Percon24: 11.54 to 12.48 12,01pm mini pm

7% Ni Percon24: thickness 8,14pm 7% Ni Percon 24: 9.52 pm mini NPC 27% Ni: 43.57 pm

NPC 27% Ni: thickness 40pm mini NPC 1.5% Ni: 7.48 pm

NPC l, 5% Ni: thickness 1,27pm mini

ST The variation of the characteristics 27% Ni Percon24: CR = 0,32% E mechanical and electrical must be = 23,29% and LR = -3,33% lower than 10% for 60 minutes 10% Ni Percon24: CR = - 0.74% E exposure at 450 ° C for all = 0.001% and LR = -4.09% materials 7% Ni Percon 24: CR = 1.07% E

= -9.14% and LR = -3.84%

NPC 27% Ni: CR = 1.87% E =

-0.75% and LR = -1.36%

NPC 1.5% Ni: CR = -6.08% E =

-5.64% and LR = -1.86% T Samples are exposed for 27% Ni Percon24: D = 0.507mm

504 hours at 350 ° C, then all CR = 528.37 MPa E = 10.45% LR =

168 hours of samples are 128.93 Ω / km and RFA = 86 cycles taken and tested. The variations of 10% Ni Percon24: D = 0.509mm these characteristics must remain CR = 535.5 MPa E = 7.35% LR = less than 10% 105.21 Ω / km and RFA = 75 cycles

7% Ni Percon 24: D = 0.513mm

CR = 466.41 MPa E = 8.92% LR =

102.74 Ω / km and RFA = 67 cycles

NPC 27% Ni: D = 0.512mm CR =

316.97 MPa E = 26.95% LR =

116.33 Ω / km and RFA = 26 cycles

NPC 1.5% Ni: D = 0.507mm CR =

247.9 MPa E = 24.37% LR = 91.1

Ω / km and RFA = 21 cycles

It should be noted that the test of resistance to alternating bending is not successful by the majority of the tested materials. In reality this test is not crucial because the conductors will essentially be assembled in strands with higher mechanical properties. The advantage of measuring the bending resistance of a single strand is to evaluate the influence of aging on this characteristic and thus to identify the material that has the best property for aging.

In conclusion, the 27% nickel-coated Percon 24 copper alloy is distinguished only from other materials by its alternating flexural strength performance which is 50 times greater than for the other nickel coated Percon 24s. Unfortunately this performance decreases after 168 hours of aging and falls to be only 25% higher compared to the Percon 24 coated with 7% nickel and 15% higher compared to the Percon 24 coated with 10% nickel. As a result, there does not seem to be any obvious difference between the three Percon 24 materials.

In terms of resistance to alternating bending, nickel coated copper appears to be relatively weak. Tensile strength is better for the Percon series 24 only for copper coated with nickel. Among the Percon 24, the Percon 24 coated with 10% nickel and the Percon 24 coated with 27% nickel are equivalent in terms of tensile strength.

In terms of elongation, there are no significant differences between the different Percon 24. The nickel coated copper shows a better electrical linear resistance but the Percon 24 coated with 7% nickel and the Percon 24 coated with 10% nickel also show good properties. The Percon 24 coated with 27% nickel shows a significant reduction in its breaking load after exposure to 500 ° C.

Thus it seems that nickel coating thicknesses of 7 or 10% are sufficient to keep good mechanical characteristics. The best compromise between these two thicknesses of coating seems to be the thickness of 10% nickel. Indeed Percon 24 coated with 10% nickel shows a high resistance to traction and alternating flexion combined with good conductivity. It differs from Percon 24 coated with 7% nickel in terms of tensile strength. Aging has relatively little influence on these properties.

Thus, the material that was used in the rest of the examples is Percon 24 coated with 10% nickel marketed by Fisk Alloy.

Example 2: Selection and evaluation of central conductor construction

To choose the type of construction of the central conductor tests were carried out on different constructions muiti strands. The materials tested were copper alloy Percon 24 sold by the company Fisk Alloy coated with 10% nickel. We find the different constructs tested in Table 3 below: Table 3; Multi-stranded construction tested

The same tests as those used to choose the most suitable material in Example 1 were carried out on the different constructions. Additional tests were implemented: weldability (S) according to IEC 68-2-69 or NF A 89-400, torsional torque (CT) and temperature rise under amperage variation (ET).

In particular, to perform the temperature rise test under amperage variation, a sample 1 millimeter long is placed in an oven. Different currents are applied on the cable and the temperature rise is measured at 50 ° C, 100 ° C, 150 ° C, 200 ° C, 260 ° C and 300 ° C with two thermocouples attached to the cable. A third thermocouple is used to control the temperature in the oven. The temperature rise must not exceed 10 ° C for an applied current of 6 and 12 A. This test makes it possible to characterize the configuration of the most suitable conductor in terms of temperature rise induced by the current.

The test results are summarized in Table 4 below: Table 4: Test Results

Type Requirements Results

of

test

D 19 * 0.511 Unilay: 0.511 mm +/- 1% 19 * 0.511 Unilay: 0.539 mm and and 2.55 mm nominal 2.545 mm nominal

19 * 0.511 concentric: 0.511 mm 19 * 0.511 concentric: 0.509 +/- 1% and 2.55 mm nominal mm and 2.535 mm nominal

7 * 7 * 0.320 ropelay: 0.320 mm +/- 7 * 7 * 0.320 ropelay: 0.321 mm 1% and 2.88 mm nominal and 2.845 mm nominal

37 * 0.361 concentric: 0.361 mm 37 * 0.361 concentric: 0.358 +/- 1% and 2.527 mm nominal mm and 2.528 mm nominal

RL 19 * 0.511 Unilay: 5.95 Ω / km maximum 19 * 0.511 Unilay: 4.91 Ω / km

19 * 0.511 concentric: 5.95 Ω / km 19 * 0.511 concentric: 5.42 maxi Ω / km

7 * 7 * 0.320 ropelay: 5.94 Ω / km max 7 * 7 * 0.320 ropelay: 5.42 Ω / km 37 * 0.361 concentric: 6.20 Ω / km 37 * 0.361 concentric: 5.60 max Ω / km

A & CR 6% & 450 MPa mini 19 * 0.511 Unilay: E = 9.217% and CR = 480.74 MPa

19 * 0.511 concentric: E = 9.5024% and CR = 485.78 MPa 7 * 7 * 0.320 ropelay: E = 10.578% and CR = 457.1 MPa

37 * 0.361 concentric: E = 10.02% and CR = 529.22 MPa

RFA About 500 cycles 19 * 0.511 Unilay: about 480 cycles

19 * 0.511 concentric: about 287 cycles

7 * 7 * 0.320 ropelay: about 983 cycles

37 * 0.361 concentric: about 427 cycles SM 19 * 0.511 Unilay: 13.2 μ nominal 19 * 0.511 Unilay: 21.86 μ 19 * 0.511 concentric: 13.2 μ nominal

nominal 19 * 0.511 concentric: 18.31

7 * 7 * 0.320 ropelay: 8.13 μ nominal nominal μ

37 * 0.361 concentric: 16.21 μ 7 * 7 * 0.320 ropelay: 12.28 μ rated nominal

37 * 0.361 concentric: 13.94 μ nominal

ST Variation of characteristics 19 * 0.511 Unilay: C = 0.93%, mechanical and electrical must be E = 7.94%, LR = 0.20%

less than 10% for 60 minutes 19 * 0.511 concentric: CR = exposure at 450 ° C for all 8,19%, E = 5,56%, LR = -0,37% materials 7 * 7 * 0,320 ropelay : CR = 12 96

%, E - 11.53%, LR = -0.56% 37 * 0.361 concentric: CR = 0.90%, E = 6.97%, LR = -0.18%

VT Samples are exposed for 19 * 0.511 Unilay: D = 504 hours at 350 ° C, then all 168 0.542mm and 2.543 mm nominal hours of samples are taken and CR = 474.02 MPa E = 10.85% LR = tested. The variations of these 5 Ω / km and RFA = 581 characteristic cycles must remain 19 * 0,511 concentric: D = less than 10% 0,0,510mm and 2,551 mm nominal

CR = 507.36 MPa E = 10.07% LR = 5.54 Ω / km and RFA = 252 cycles 7 * 7 * 0.320 ropelay: D = 0.325mm and 2.849 mm nominal CR - 491.54MPa E = 11.33 % LR =

5.7 Ω / km and RFA = 737 cycles 37 * 0.361 concentric: D = 0.359mm and 2.558mm nominal CR = 521.14 MPa E = 11.5% LR =

5.8 Ω / km and RFA = 318 cycles

S Immersion for 10 seconds at 270 ° C Complies with requirements

CT Measurement of the weight required to obtain a 19 * 0.511 Unilay: 2.1 kg angle of 45 ° 19 * 0,511 concentric: 2 kg

7 * 7 * 0.320 ropelay: 1.1 kg

37 * 0.361 concentric: 1.3 kg

No damage to the cable No damage for all configurations

Finally, the preferred constructions are 19 * 0.511 Unilay and 37 * 0.361 concentric. Indeed, in particular their results in the alternating flexural strength tests are among the best even after aging at high temperature.

This is not the case of the 7 * 7 * 0.320 ropelay which shows a significant reduction in resistance to alternating flexion after aging, even if it remains the best compared to the other three constructions. In addition, degradation of its elongation properties is important after short-term exposure to temperatures of 450 and 500 ° C. In addition this construction is not quite suitable for high voltage applications because can withstand corona discharges.

The concentric 19 * 0 511 construction has the lowest alternating flexural strength of all constructions. It is for this reason that it is not the preferred construction.

Similarly between the 19 * 0.511 Unilay and 37 * 0.361 concentric construction, the 19 * 0.511 Unilay construction will be preferred because it has better resistance to alternating bending.

In the following examples, the driver will have the construction 19 * 0.511 Unilay

Example 3: Selection and evaluation of the layer of main insulating material

The list of potential materials that can be used as the main insulating material is summarized in the following Table 5 together with the reasons for which only four of them have been tested. Table 5: Potential List of Materials

Types of polymer Material Reason for choice

Thermoplastic Polyimide

thermoplastic (TPI):

AURUM PL450C Tested

marketed by the

bridge society

Nemours

EXTEM XH1005 and Not tested because having less good characteristics than AURUM

EXTEM XH1015 Not tested because having marketed by the less good company Sabic characteristics than AURUM

Polyetheretherketone Not tested because held

(PEEK): PEEK 151G insufficient thermal and marketed by the too rigid.

Victrex company

Polyetherketone (PEK):

PEEK HTG22 Tested

marketed by the

Victrex company

polyether ketone

(PEKK):

OXPEKK C-E, Tested

OXPEKK C and Not tested because of insufficient thermal resistance and too rigid

OXPEKK C03DRT Not tested because too much commercialized by the difficult to put in company Arkema work

Polyethercétoneéthercét

onecétone

(PE EKK): PEEK ST Tested

G45 marketed by

Victrex company

Thermosetting Polyimide Not tested due to insufficient thermal resistance

Varnish Not tested because the polybenzimidazole varnish crackles during simple mechanical stress

Coating of Untested because of insufficient thermal polyetheretherketone

So only four materials were tested. These are only thermoplastics. The tests were carried out on a cable as indicated in FIG. 1, the central conductor (1) having been chosen following the tests of examples 1 and 2 and thus is in Percon 24 coated with 10% nickel marketed by Fisk Alloy. under construction 19 * 0.511 Unilay and AWG 1245. The tested material is extruded to form the main layer of insulating material (2) with a thickness of 1 mm on the central conductor (1).

The following tests are carried out on the cable thus obtained: standard mechanical tests (external visual inspection according to ESCC 3901 §9.1., Measurement of mass according to the CCHS 3901 §9.1., Measurement of dimensions according to the CCHS 3901 standard. §9.1., Elongation and breaking load according to FED STD 228 Method 3211, strippability according to ESCC 3901 §9.1., High temperature insulation removal according to ESCC 3901 §9.1.), Mechanical tests specific (deployment mode characterization tests: 180 ° alternating bending test around the X axis and 135 ° alternating bending test around the Z axis), standard electrical tests (sparktest in line, rupture test dielectric, insulation resistance measurement according to ESCC 3901 §9.1.), specific electrical tests (measurement of partial discharges, high-temperature dielectric breakdown test, over-current resistance), aging tests (thermal shock tests , thermal aging test without voltage at a temperature of 280 ° C), and other tests such as degassing and cold and room winding test.

For thermal characterization, mechanical and electrical tests are carried out after storing the materials at a given temperature for a given time and the results are compared with those obtained initially to verify if these characteristics have been modified. The cable in which the main insulation layer (2) is made of AURUM PL450C material was severely affected during the aging test at 280 ° C. The damage results in a change in its appearance and the appearance of several cracks. The material becomes very brittle. Even manual manipulation can easily break the insulation. This material can not therefore be used as an insulator in the context of the cables according to the present invention.

The OXPEKK C-E material was the most difficult to implement among the four materials tested. The cable in which the main insulation layer (2) is made of OXPEKK C-E material did not pass the winding test at room temperature. Indeed several major cracks appeared after the completion of this test. This material can not therefore be used as an insulator in the context of the cables according to the present invention.

The other two materials are particularly interesting for the production of cables according to the present invention. Indeed, their mechanical characteristics are not really affected by the aging phases. The variations of the mechanical characteristics do not exceed 10 to 20%, which is not really significant given the tolerance of the measurements of this type of test. These materials still have good flexibility even after 200 hours of heat treatment at 280 ° C as demonstrated by the winding test. A decrease in elongation can be observed after thermal aging at 280 ° C which is normal for a semi-crystalline material. At 280 ° C the material reaches its maximum crystallinity and this structure is characterized by a lower elongation.

These two materials therefore have similar mechanical and electrical behavior. These are materials from the same family and their properties are very close. Their performance makes them both usable for making cables according to the present invention. No significant degradation was shown by the measurement of partial discharges. This is important because it means that there are no micro cracks or micro defects that appear during the aging phases.

Finally, what distinguishes these two materials is that the PEEK STG 45 has a slightly higher melting temperature which makes it more attractive for high temperature applications. This difference was observed during the high current test where it was noticed that the PEEK HT G22 material melted before the PEEK STG45 material. In view of all these elements, the preferred material is PEEK STG45. It is therefore this material that will be chosen in the rest of the tests and examples.

To better characterize its long-term resistance at high temperature, a thermal aging test for 2000 hours at 280 ° C was carried out on this material. It is observed that the samples become brittle after 1000 hours at an exposure of 280 ° C which is shown by the results of the winding test. These results show that the material after aging (more than 1000 hours) can only withstand small flexural stress amplitudes. When it is exposed to too high flexural amplitudes, it breaks. Electrically, this material still keeps interesting properties since the dielectric breakdown test is greater than 10kV DC at 300 ° C. These dielectric breaks are higher for samples aged between 1500 and 2000 hours than for those aged 500 to 1000 hours and these differences can be explained by the high degree of crystallinity achieved during the aging test. The higher the crystallinity, the higher the electrical resistance.

Example 3; evaluation of the final construction of the cable

a - preliminary tests for selection of the composition of layers of insulating materials

Since the final construction of the cable will include a metal shield to remove electromagnetic interference (EMI), it seems interesting to add thermosetting layers between the outer layer of metal shielding and the thermoplastic layer to avoid problems that may appear at the metal / polymer interface at high temperature. The question may also arise whether such a layer may also be present between the main layer of thermoplastic insulating material and the central conductor. Two configurations and have been tested:

The first is similar to that shown in Figure 2 with the exception of the absence of the layer (5) of metal shielding. The second is similar to that shown in Figure 3 with the exception of the absence of the metal shielding layer (5).

In these two configurations the central conductor (1) is in the alloy Percon 24 coated with 10% nickel sold by the company Fisk Alloy with the construction 19 * 0.511 Unilay. The layer of main insulating material (2) is PEEK STG45 extruded with a thickness of 1 mm.

In both configurations, an additional thermosetting polyimide layer (3) made of KAPTON 200 HN tape sold by Dupont De Nemours is wound on the main layer of insulating material (2) to form two layers with a covering of 50% and having a thickness 50 pm.

In the second configuration, a polyimide intermediate layer (4) made of KAPTON 100 HN tape sold by Dupont De Nemours is wound on the center conductor (1) to form 2 layers with a 50% overlap and having a thickness of 25 μm.

The main test implemented on these two configurations is the high temperature dielectric breakdown test. The results of these tests show that the second configuration gives better results than the first one. This configuration was thus kept by adding the metal shielding material layer (5) as shown in FIG. 3 to test the construction of the final cable according to the present invention. b - Evaluation of the final construction of the cable

The final construction tested corresponds to that illustrated in FIG.

Thus, it comprises a central conductor (1) made of copper alloy Percon 24 coated with 10% of nickel marketed by the company Fisk Alloy having the construction 19 * 0.511 Unilay on which is wound a polyimide intermediate layer (4) made of tape KAPTON 100 HN sold by the company Dupont De Nemours to form 2 layers with a coverage of 50% and having a thickness of 25 pm. The layer of main insulating material (2) is PEEK STG45 extruded with a thickness of 1 mm. An additional thermosetting polyimide layer (3) made of KAPTON 200 HN tape sold by the Dupont De Nemours company is wound on the main layer of insulating material (2) to form 2 layers with an overlap of 50% and having a thickness of 50 μm.

Finally, a layer of outer metal shielding material (5) is woven based on Percon 24 copper alloy coated with 10% nickel marketed by Fisk Alloy, each strand having a diameter of 0.127 mm.

Several tests are carried out on this cable such as aging tests (high voltage thermal cycle (5kV DC) from -80 ° C to +180 ° C: 100 cycles with a temperature ramp of 2 ° C per minute and 1 hour of maintenance at each plateau, thermal aging under high voltage (5kV DC) divided into two phases: 200 hours at 280 ° C and 100 hours at 300 ° C, irradiation test with a dose of 200 Mrad at each stage of the aging: initial stage, after thermal cycle, after thermal aging). Electrical and mechanical testing standards (visual appearance, tension test, winding test, bending test at 6 +/- ^0, bending test +/- 90 ^0, bending test at +/- 67 °), dielectric strength tests at high temperature (100 ° C, 180 ° C, 260 ° C and 300 ° C) and partial discharge tests are implemented in the initial state and after each aging phase using the device described in patent application FR11 / 60136. Finally, a cold bending test is implemented. The results of these tests are as follows:

Before irradiation: the mechanical properties are in conformity. The winding test which is carried out at each phase of aging is still in conformity and shows that the cable retains its mechanical properties even after exposure to 280 ° C under high voltage.

After irradiation: no degradation of the mechanical or electrical properties is observed. The cable keeps its mechanical and electrical properties compliant after a thermal cycle and an aging phase at 280 ° C under high voltage (5 kV).

Thermal aging at 300 ° C: this test causes advanced degradation of the insulation material resulting in cracking and pronounced color change.

High temperature dielectric strength: the insulating material shows high electrical properties even at very high temperatures. At 300 ° C, the dielectric breakdown of aged samples is always greater than 10kV AC. These results show that the proposed construction meets the requirements for maximum voltage combined with maximum temperature.

Partial discharge measurements: in view of the overall results, the insulation material is homogeneous in its initial state and has not been significantly degraded during the aging phases. In view of all the results of the evaluation of the cable and its various components presented in Examples 1 to 3, it can be concluded that the Insulating material was not significantly damaged during thermal aging and after irradiation. The main effects observed are a stiffening of the material is a darker color. Finally, the cold bending results comply with the required conditions.

Thus, after the aging phases it was found that the final construction of the cable was able to withstand small amplitude (+/- 6 °) bending tests characteristic of normal operation, even after an aging of 2000 hours at 280 ° C. Thus, even if the aging phases significantly stiffen the cable, it is able to perform its functions without fail (cracks etc.).

The selected conductor, in the first evaluation part (example 1), is able to withstand very high temperature for a long time. Its design meets the requirements of the maximum voltage and the risk of oxidation is absent due to the defined thickness of the nickel coating. The test results show that the selected construction is capable of withstanding a large number of large amplitude bending cycles and that high temperature aging has only a small impact in the case of low amplitude movements. The final assembly of the chosen construction is suitable for high voltage applications because of its external shape. The evaluation showed that the combination of aging phases followed by winding tests was not sufficient to damage the insulation. Partial discharge measurements revealed the absence of micro defects during the aging of the insulating material.

Even after an aging of 2000 hours at 280 ° C, the cable is still able to withstand induced movements (+/- 6 ° of bending tests) in normal operation and its electrical properties are still satisfactory. The radiation level of 200 Mrad has little effect on the properties of the cable. The results obtained allow to conclude that the construction of the defined and evaluated cable is able to fulfill all the conditions to be usable in extreme conditions.

Claims

A high-voltage electrical cable comprising a central conductor (1) of copper or copper alloy coated with nickel and at least one main layer of insulating material (2) arranged around the central conductor (1), said layer of insulating material being formed by an extruded thermoplastic selected from polyetherketones, polyetherketoneetherketoneketones and mixtures thereof.

2. Cable according to claim 1, characterized in that the main layer of insulating material (2) is formed of polyetherketoneetherketoneketones.

3. Cable according to any one of claims 1 or 2, characterized in that the main layer of insulating material (2) has a thickness between 0.1 and 3 mm, preferably between 0.2 and 1.5 mm, even more preferably the thickness is 1 mm.

4. Cable according to any one of claims 1 to 3, characterized in that the nickel coating of the central conductor (1) has a thickness of between 7 and 11% by weight, preferably 10% by weight according to ASTM B355 .

5. Cable according to any one of claims 1 to 4, characterized in that the central conductor (1) is nickel-coated copper alloy, said alloy advantageously comprising chromium up to a content of 1% by weight and zirconium up to a content of 1% by weight and being free of cadmium, cobalt, lead, beryllium and mercury.

6. Cable according to any one of claims 1 to 5, characterized in that it comprises a layer of additional insulating material (3) around the main layer of insulating material (2), said layer of insulating material further (3) being formed by a thermosetting polymer polyimide or polybenzimidazole, preferably a polyimide in ribbon form.

7. Cable according to any one of claims 1 to 6, characterized in that it comprises a layer of intermediate insulating material (4) interposed between the central conductor (1) and the main layer of insulating material (2), said layer of intermediate insulating material (4) being formed by a thermosetting polymer polyimide or polybenzimidazole, preferably a polyimide in ribbon form.

8. Cable according to any one of claims 6 or 7, characterized in that the layer of additional insulating material (3) and / or the layer of intermediate insulating material (4) each comprises between one and four layers of coiled ribbon polyimide , advantageously two or three layers of tape-coated polyimide, still more advantageously 2 layers of tape-coated polyimide, with a covering of between 25 and 75%, advantageously of 50%.

9. Cable according to any one of claims 1 to 8, characterized in that it comprises an outer layer (5) of metal shielding material, preferably made of the same material as the central conductor.

10. Cable according to claim 9, characterized in that it comprises an intermediate semiconductor layer (6) interposed between the main layer of insulating material (2) or the layer of additional insulating material (3) and the outer layer (5). ) of shielding material, said semiconductor layer (6) being advantageously a polyimide tape loaded in the mass by a charge selected from carbon black or carbon nanotubes.

11. Cable according to any one of claims 1 to 10, characterized in that the central conductor (1) consists of several strands, preferably 19, assembled in Unilay.

12. Cable according to any one of claims 1 to 11, characterized in that the central conductor (1) has a section between 0.05 and 22 mm ² , preferably between 0.5 and 4.5 mm ² even more advantageously against 3.8 and 4.1 mm ² .

13. Cable according to any one of claims 1 to 12, characterized in that it is able to withstand for at least 2000 hours without electrical failure:

operating temperatures between -50 ° C and 280 ° C,

- resting temperatures between -100 and 280 ° C for static applications,

- a radiation dose of up to 1000 egarads,

an operating voltage of up to 10 000 V and

14. Use of the cable according to any one of claims 1 to 13 in the field of petroleum, aeronautics, aerospace, nuclear, scientific research and / or petroleum research.