Composite termination of high or very high voltage electrical transmission cable and method for preparing a cable termination

Abstract

Composite termination (8) of a high or very high voltage cable (1), suitable for being surrounded by a deflector cone (20) to form an electrical termination, particularly inside a blast-resistant terminal (10), the termination being prepared by successive steps of stripping an external semiconducting layer (5) of the cable in order to expose a longitudinal portion (9) and forming a bevel (14) at the free end (13) of this layer. Figure for the abbreviation: Fig. 2

Description

Title of the invention: Composite termination of high or very high voltage electrical transmission cable and method for preparing a cable termination

[0001] The present invention relates to a composite end of a high or very high voltage cable, in particular these composite ends are arranged in electrical terminations for connection with a connector. The invention also relates to a method for preparing an end of a high or very high voltage cable. In particular, the invention finds its application in association with an explosion-proof terminal arranged externally around a termination of such a high voltage cable.

[0002] As described in patent documents EP 2 259 401 and DE 2 746 566, it is known that one end of a cable is coupled to a connector inside a sealed terminal, the sealed terminal forming an explosion-proof terminal and comprising a cylindrical sleeve, a lower plate and an upper plate, the plates respectively sealing the sleeve at its two opposite ends in order to define a sealed volume suitable for containing insulating material. Together, the composite end of the cable and the connector define a cable termination.

[0003] To enable the connection between the connector and the composite end of the high-voltage cable in such a terminal, it is known in particular from patent documents EP 2 461 448 and FR 3 009 901, to arrange a deflector cone made of flexible material around a central conductor of the composite end of the cable. Such a deflector cone is of relatively limited length and volume.

[0004] The invention applies to the field of high-voltage power cables (in particular above 60 kV, and up to 800 kV), whether direct or alternating current. Power cables typically comprise a central electrical conductor and at least one electrically insulating layer of cross-linked or thermoplastic material using techniques well known to those skilled in the art.

[0005] Since electrical terminations are generally arranged in explosion-proof terminals erected vertically on the ground, there is a need to improve the tensile strength of the ends of the cables held in connectors inside these terminals, including for operating temperatures of more than 100°C, for example on the order of 130°C.

[0006] To this end, the invention relates to a composite end of a high or very high voltage electrical transmission cable comprising a free end of a cable, the cable comprising an elongated central conducting element, and a plurality of layers arranged successively from innermost to outermost, coaxially around this conducting element, this plurality of layers comprising an inner semiconducting layer, an electrically insulating layer, an outer semiconducting layer, such that a portion of the layers is stripped from a distal end of the free end of the cable, the outer semiconducting layer being stripped over an axial length greater than the length over which the electrically insulating layer is stripped, and one end of the outer semiconducting layer forming a bevel.

[0007] Preferably, the bevel may have a slope of less than 2°. In particular, since the outer semiconducting layer is annular, it can be defined by a radial thickness of between 1 and 2 mm. More specifically, one edge of the bevel, the one in contact with the electrically insulating layer, can be defined in an annular area of ​​less than 5 mm in axial length along a longitudinal axis of the cable, to improve the contact surface with an annular lip of a deflector cone.

[0008] Furthermore, the invention also relates to a termination for a high or very high voltage electrical transmission cable comprising a composite end according to the invention and such that it includes a deflector cone provided with an annular lip, the lip of the cone being arranged around the bevel such that a free edge of this lip bears against the bevel. The interaction of the annular lip with a gently sloping bevel, the annular lip preferably having a cylindrical inner circumference, makes it possible to form an annular seal over an axial length sufficient to withstand the temperature and pressure variations that are common in such a termination.

[0009] In particular, the external semiconductor layer can be made of a thermoplastic material, and more particularly have a hardness below a predetermined threshold, in particular for a shore A hardness below 95 and for a shore D hardness below 43.

[0010] The invention also relates to a method for preparing one end of a cable according to the invention, in which the preparation steps, in particular for stripping it, comprise the following steps: - from a distal end of a free end of the cable, the electrically insulating layer is stripped with a stripping device such that the outer semiconductor layer is removed over an axial length greater than the length over which the electrically insulating layer is stripped, - a glass plate is used to modify the slope of the end of the outer semiconductor layer in order to form a bevel.

[0011] More particularly, and with regard to the mechanical characteristics of the semi-layer external conductor, the process can use a stripping device comprising a flat blade oriented perpendicular to a longitudinal axis of the cable. Brief description of the drawings

[0012] The attached drawings illustrate the invention:

[0013] [Fig-1] represents a power cable according to the invention presented in an exploded view in order to identify the main layers that make it up;

[0014] [Fig.2] represents a detailed view of a termination according to the invention implementing a composite end of a cable according to the invention in cooperation with a deflection cone;

[0015] [Fig.3] represents a view of detail A of [Fig.2];

[0016] [Fig.4] and [Fig.5] represent a perspective view of a stripping device placed in work in the process according to the invention;

[0017] [Fig.6] represents a schematic view of principle allowing representing the blade of the stripping device relative to the end of the cable in a method according to the invention;

[0018] [Fig. 7] represents the beveling step of the process according to the invention in which the outer semiconductor layer is beveled with a glass plate. Description of embodiment(s)

[0019] A high-voltage power cable 1, illustrated in [Fig. 1], comprises an elongated central conductive element 2, in particular made of copper or aluminum. The power cable 1 further comprises several layers arranged successively and coaxially around this conductive element 2, considered successively from the innermost to the outermost, namely: a first semiconducting layer 3 called the "inner semiconducting layer", an electrically insulating layer 4, a second semiconducting layer 5 called the "outer semiconducting layer", a metallic screen 6 for grounding and / or protection, and an outer protective sheath 7. The presence of the metallic screen 6 and the outer protective sheath 7 is preferable, but not essential, this cable structure being as such well known to those skilled in the art.

[0020] The end 8 of this cable is intended to be connected to a connector (not shown) to form a termination, in particular within a blast-proof terminal 10, the cylindrical sleeve 18 of which is shown [Fig. 2]. This end 8 refers to a portion 9 of the cable 1 extending between its free end 11 and an unstripped edge 12 of the outer semiconductor layer 5. The cable 1 is surrounded by a deflector cone 20. This cone 20 has a body 21 mounted around the insulating layer 4, this body having an annular lip 22 extending over a portion of the cable portion 9. More particularly, this annular lip 22 extends partially around a free end 13 of the outer semiconductor layer 5. Preferably the annular lip 22 extends around the outer semiconductor layer 5, beyond the unexposed edge 12.

[0021] The lip 22 is made of a flexible material, capable of deforming radially around the cable 1 in order to create an annular seal around the external semiconducting layer 5.

[0022] As shown in [Fig.3], the outer semiconductor layer 5 has a bevel 14 between its free end 13 and an unstripped edge 12 of this layer 5. Thus the annular lip can cover the bevel 14 over its entire length.

[0023] The free end 13 forms an edge of the bevel 14. The bevel 14 defines a frustoconical surface. In particular, the slope α of this bevel is less than 10°, preferably less than 2°, for example, on the order of 1.6°. This slope α extends over an axial length of approximately 10 cm along the longitudinal axis of the cable. In particular, the edge of the bevel 13 defines a ring extending substantially in a plane orthogonal to the longitudinal axis. Thanks to the preparation method according to the invention, the edge of the bevel 13 extends into an annular zone of length 1 of less than 10 mm, preferably less than 5 mm.

[0024] Figure 4 represents a stripping device 30, in which a blade 31 is driven in a helical motion around the cable. In particular, according to the invention, the stripping begins from the free end 11 of the cable to the free end 13 of the outer semiconductor layer 5.

[0025] As shown in Figures 4 and 6, the blade 31 defines a cutting edge 32 substantially in the plane orthogonal to the longitudinal axis X. Along the axis X, the blade 31 is also in a plane forming a slight angle [3 with the tangency to the outer edge of the insulating layer 4. An edge of this blade 31 remains in contact with the insulating layer 4 during its helical movement around the cable.

[0026] To prepare the end of the cable, the material from the outer semiconducting layer 5 is removed by stripping up to the free end 13.

[0027] Then, to finalize the preparation of the free end of the cable, depending on the radial thickness of the external semiconducting layer 5 and the desired bevel angle 14, an operator in charge of the preparation places a circumferential marker 33 around the external semiconducting layer 5, in order to delimit the area to be beveled.

[0028] To modify the slope of the end of the outer semiconductor layer 5 in order to bevel the previously determined area and to modify the surface finish to make it as smooth as possible, the operator uses a glass blade 34 and performs longitudinal back-and-forth movements, which are repeated over all angular sectors of the area to be beveled. The beveling is carried out manually so that the slope varies by only ±0.2° between the bevel edge 13 and the unstripped edge 12.

Claims

Demands

1. High or extra-high voltage electrical transmission cable termination comprising a composite end (8) of a high or extra-high voltage electrical transmission cable (1) comprising a free end of a cable, the cable comprising an elongated central conductive element (2), and a plurality of layers arranged successively from the innermost to the outermost, coaxially around this conductive element, this plurality of layers comprising an inner semiconducting layer (3), an electrically insulating layer (4), an outer semiconducting layer (5), such that a portion of the layers is stripped from a distal end of the free end of the cable, the outer semiconducting layer being stripped over an axial length greater than the length over which the electrically insulating layer is stripped, characterized in that an end of the outer semiconducting layer forms a bevel,characterized in that it comprises a deflector cone (20) provided with an annular lip (22), such that this lip of the cone (22) covers the bevel (14) along its entire length.

2. Termination according to claim 1 characterized in that the bevel (14) has a slope of less than 2°.

3. Termination according to claim 1 or 2 characterized in that an edge of the bevel (13), in contact with the electrically insulating layer, is defined in an annular area of ​​less than 5 mm of axial length (1) along a longitudinal axis of the cable.

4. Termination according to any one of the preceding claims characterized in that the external semiconductor layer is made of a thermoplastic material.

5. Termination according to any one of the preceding claims characterized in that the external semiconductor layer has a hardness below a predetermined threshold, in particular for a shore A hardness below 95 and for a shore D hardness below 43.

6. A method for preparing a termination for a high or very high voltage power transmission cable comprising a high or very high voltage power transmission cable having a free composite end of a cable, the cable comprising an elongated central conductive element (2), and a plurality of layers arranged successively from the innermost to the outermost, coaxially around this

7. conductive element, this plurality of layers comprising an inner semiconductor layer (3), an electrically insulating layer (4), an outer semiconductor layer (5), characterized in that it comprises the steps - from a distal end of a free end of the cable, the electrically insulating layer is stripped with a stripping device (30) so that the outer semiconducting layer is removed over an axial length greater than the length over which the electrically insulating layer is stripped, - a glass plate (34) is used to modify the slope of the end of the outer semiconductor layer in order to form a bevel (14) - a deflector cone (20) provided with an annular lip (22) is brought around this free end so that this lip of the cone (22) covers the bevel (14) over its entire length. Method according to claim 6 characterized in that the stripping device comprises a flat blade (31) oriented perpendicularly to a longitudinal axis (X) of the cable.

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