WO2022064107A1

WO2022064107A1 - Composite core for crack-resistant electrical conductor

Info

Publication number: WO2022064107A1
Application number: PCT/FR2020/051683
Authority: WO
Inventors: Baptiste GARY
Original assignee: Gary BAPTISTE
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2022-03-31

Abstract

One aspect of the invention relates to a composite core (1) for an electrical conductor which is filled and comprises a centre (2) made of glass fibres (20), an inner layer (3) made of carbon fibres (30), an outer layer (4) made of a glass fibres (40) and resin. The composite core is characterised in that the centre (2) and the outer layer (4) have a lower tension than the inner layer (3). Since the inner layer (3) has a higher tension than the tension of the centre (2), it is more rigid; a crack (5) will therefore spread towards the centre, where the tension is lower, and will then be diverted or stopped depending on the profile or the dimension of the centre. In this manner, the core will not be split into two equal parts causing its resistance to reduce by half.

Description

DESCRIPTION

TITLE: Composite core for crack-resistant electrical conductor

TECHNICAL FIELD OF THE INVENTION

The technical field of the invention is that of electrical conductors, more particularly those having a composite core.

The present invention relates in particular to this composite core and an electric cable comprising said core made of composite materials.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] The demand for cables for electrical transport and distribution is increasing with the ever-increasing demand for electricity. As the need for power increases, new electric cables have to be laid. On the other hand, to increase the capacity, the existing electric cables must be replaced by cables of greater capacity.

[0004] Usually, these cables comprise a central core of stranded steel wires on which is wrapped one or more stranded aluminum conductors. These type of cables have been used for decades without much change. Among other disadvantages, this type of cable is prone to excessive sag in certain climates and under certain operating conditions.

[0005] Solutions have been proposed to respond to these defects, such as for example patent EP 1 506 085, incorporated by reference, which proposes making a single-strand composite core comprising continuous lengthwise carbon fibers forming an inner layer and a non-conductive insulating layer comprising glass fibers and surrounding the inner layer. Although the outer layer protects the inner layer, the latter can crack under the effect of a shock during uncontrolled manipulations on the composite core and/or the cables comprising a central core made of composite materials, which will weaken the electrical cables that contain them and sometimes cause it to break completely. [0006] It has also been proposed to introduce a composite core consisting of a strand of glass fibers coated in a resin in the internal carbon layer coated in a resin, the core and the internal layer being introduced into the layer external fiberglass coated in a resin in patent EP 2 1 18 909, incorporated by reference, and a method of manufacture has been described. However, on the one hand, the single-strand core obtained does not make it possible to achieve a yield greater than 90% of the carbon fiber, on the other hand the overmolding of the core in composite materials made of fiberglass makes the interface between the core and the inner layer sensitive to crack propagation, the chemical and mechanical adhesion of the interface being limited by the independent firing of the core and the inner layer. The single-strand core thus formed may present transverse fragilities in the event of impact during uncontrolled manipulations on the composite core and/or the cables comprising a central core made of composite materials. By composite yield, we mean the ratio between the theoretical performance of the composite in tension, calculated in relation to the values given by the suppliers of the batches of fibers used for the manufacture weighted by the volume rate of fiber in the composite and the actual value obtained. in a laboratory test on the manufactured composite.

[0007] It has also been proposed to introduce solutions in multi-strand composite materials to respond to these defects, such as for example US Patent 8,250,845, incorporated by reference, which proposes to produce a composite core comprising a plurality of composite materials, carbon fibers coated in a resin, all the sections being stranded with each other to form a core, thus limiting the ability of a shock to be transmitted between the sections constituting the core of the conductor, the core obtained does not make it possible to achieve a yield greater than 90% of the carbon fiber. This design, requiring an additional step of stranding the strands constituting the multi-strand core, also has the disadvantage of being much more complex and expensive than single-strand solutions to produce.

[0008] In addition, the various standards, such as the ASTM standard (American Society for Testing Material) or the European standard define the size of the electric cables according to the current load. These cables of various sizes can carry between 100A (ampere) and over 3200A, a range of operation between 40°C and 230°C, preferably between 75°C and 180°C. The composite material core must also be able to withstand a stress of more than 2100MPa.

[0009] However, these single-strand composite cores, which are more economical to manufacture compared to multi-strand cores, have the drawback of being more fragile and therefore more prone to breakage than prior art metal cores or composite multi-strand cores. So if the core receives a shock, a crack may be created and spread across the entire width of the core, making it more fragile in terms of mechanical resistance, until it becomes unusable.

SUMMARY OF THE INVENTION

The invention offers a solution to the problems mentioned above, by limiting the propagation of the crack while using a competitive single-strand manufacturing technology.

The composite core for an electrical conductor according to the invention is solid and comprises a glass fiber core, an inner layer of carbon fibers, an outer layer of glass fibers, it is characterized in that the heart and the outer layer have a lower mechanical tension than the inner layer and the core has a non-uniform surface. The resin is used to coat the fibers of the core and of the two inner and outer layers. As the inner layer has a tension greater than the tension of the core, it is more constrained, the crack will therefore propagate towards this one where the tension is lower then will be deflected or stopped according to the profile or the dimension of the core by dissipating the energy required for crack propagation. Due to the non-uniform surface of the heart, the crack moving towards the heart, it will stop dissipating its energy on its surface and as this one is not flat, it will bounce on another outgrowth and s 'Stop. This way, the core will not be split into two parts causing its resistance to drop drastically.

[0012] Advantageously, the tension of the fibers of the inner layer is 2 to 10 times greater than the tension of the fibers of the core. This voltage difference allows good transmission of the crack to the glass fiber core. It is possible, for example, to have an average tension of the glass fibers before impregnation of 100 to 300 centinewtons (cN) and preferably of 150 to 250 cN with a tension of the fibers of carbon before impregnation from 200 to 600 centinewtons (cN) and preferably from 300 to 500 cN.

[0013] Advantageously, the core has a section 10 to 35 times smaller than the section of the inner layer. The inner layer being more tense and therefore more constrained than the core, it must remain small in size compared to the inner layer which provides most of the rigidity and resistance of the core.

[0014] In a first embodiment, the resin is common and continuous throughout the fibers. This guarantees an optimum chemical bond between the different fibres. The continuity of the resin means that all the elements constituting the core are cured at the same time and therefore that there is no physical and chemical discontinuity of the matrix between the fibres, neither between the layers, nor between the core and layers.

[0015] In a second embodiment, the resins impregnating the different layers and the fiber core are chemically compatible together during the polymerization. By chemically compatible together, we mean the fact that the resins are capable of polymerizing together without discontinuity during joint curing. This guarantees an optimum chemical bond between the different fibres. The chemical continuity between the different resins allows all the elements constituting the core to be cured at the same time and therefore there is no physical and chemical discontinuity of the matrices between the fibers and the matrices, nor between the layers, nor between the heart and the layers.

[0016] Advantageously, the core is placed in the center of the inner layer. This position makes it possible to limit the crack to half the section of the core.

The invention also relates to an electric cable comprising a composite core with at least one of the preceding characteristics.

The invention and its various applications will be better understood on reading the following description and on examining the accompanying figures.

BRIEF DESCRIPTION OF FIGURES

The figures are presented for information only and in no way limit the invention.

[0020] [Fig. 1] is a schematic view of a core according to the invention [0021] [Fig. 2] shows the propagation of a crack on a core of the state of the art;

[0022] [Fig. 3] shows the propagation of a crack on a core of the state of the art;

[0023] [Fig. 4] shows the propagation of a crack on a core of the invention according to a first embodiment;

[0024] [Fig. 5] shows the propagation of a crack on a core of the invention according to a variant of the first embodiment;

[0025] [Fig. 6] is a perspective view of a cable according to the invention.

DETAILED DESCRIPTION

Unless otherwise specified, the same element appearing in different figures has a single reference.

The core 1 illustrated in Figure 1 comprises a core 2, an inner layer 3 and an outer layer 4. The core 2 consists of continuous glass fibers 20 secured by resin. The inner layer 3 consists of continuous carbon fibers 30 and resin. The outer layer 4 consists of continuous glass fibers 40 and resin. In this example, the carbon fibers 30 and the glass fibers 40 are advantageously positioned parallel to each other and in the axis of the core.

[0029] The heart 2 is of reduced size compared to the diameter of the core 1 in order to limit the impact of the performance in terms of rigidity and global resistance of the core 1 .

[0030] When the core 1 of the state of the art illustrated in Figure 2 receives a shock (represented by the hammer M), a crack 5 is created, it will spread to dissipate the energy of the impact at the both on the outer layer 4 and in the center 3 ', consisting of continuous carbon fibers 30 and resin, or over the entire section of the core until it is completely cut into two parts 31 and 32.

[0031] In the same way, when a core 2 consisting of a composite containing glass fibers 20 and of a uniform surface, is placed in the middle of the layer interior 3 (see figure 3), the core will deviate the crack 5 on one side until the core is completely cut into two parts, in the latter case there will be two parts 33 and 34.

In the examples of Figures 4 and 5, the core 2 has a non-uniform surface: with pointed projections 21 in the case of Figure 4 or with rounded beads 22 in the case of Figure 5. Of course, other surface profiles are possible, in particular by choosing protrusions of different shapes: circular, oval, trapezoidal, rectangular or other. Here, the difference in tension between the glass fibers 20 and the carbon fibers 30 facilitates the dissipation of energy at the interface of the two fibers and therefore the crack 5 will move towards the zone of least stress, it that is to say towards the core 2. The surface of the core being non-uniform, it will further dissipate the propagation of the crack 5 towards one of the growths which will stop it. In this way, core 1 will not be completely cracked and the resistance of the cable will not be reduced too much.

[0033] The core 2, the inner layer 3 and the outer layer 4 can be joined together in the same resin by a single curing of the assembly, which makes it possible to have chemical continuity of the resin at the interface of the different fibers and to improve the dissipation of crack energy until its propagation in the longitudinal direction of the core is stopped.

The electrical cable 6 shown in Figure 6 comprises a core 1 described above and two layers of conductors 60 and 61 consisting of conductive strands, for example aluminum, trapezoidal in shape and wound helically around the core 1.

Claims

7 CLAIMS

[Claim 1] Solid composite core (1) for an electrical conductor comprising a core (2) of glass fibers (20), an inner layer (3) of carbon fibers (30), an outer layer (4) of carbon fibers glass (40) and at least one resin, characterized in that the core (2) and the outer layer (4) have a lower mechanical tension than the inner layer (3) and that the core (2) has an uneven surface .

[Claim 2] Core (1) according to claim 1, characterized in that the tension of the fibers of the inner layer (3) is 2 to 10 times greater than the tension of the fibers of the heart (2).

[Claim 3] Core (1) according to one of the preceding claims, characterized in that the core (2) has a section 10 to 35 times smaller than the section of the inner layer (3).

[Claim 4] Core (1) according to one of the preceding claims, characterized in that the resin is common and continuous throughout the fibers (20, 30, 40).

[Claim 5] Core (1) according to one of claims 1 to 3, characterized in that the resins impregnating the different layers and the fiber core are chemically compatible together during the polymerization.

[Claim 6] Core (1) according to one of the preceding claims, characterized in that the core (2) is arranged in the center of the inner layer (3).

[Claim 7] Electric cable (6) comprising a core (1) according to one of the preceding claims.