KR20130008878A - Electric power cable for wind turbine - Google Patents

Abstract

The present invention discloses a power cable for a wind generator. The power cable according to the present invention comprises: an inner semiconducting layer that surrounds a center conductor and an outer circumference of the center conductor in order, at least one power line consisting of an insulating layer and an outer semiconducting layer and extending in a longitudinal direction; A metal shielding layer surrounding an outer circumference of each power line to shield or ground unstable power generated from the power lines; And an inner and outer sheath layer surrounding the at least one power line, wherein the metal shielding layer is made of element wires of element wire diameters, and the element wires are formed by wiping in a single direction.

Description

Electric power cable for wind turbine

The present invention relates to a power cable, and more particularly to a power cable for a wind generator for transmitting power generated from the wind generator.

Recently, as the depletion of fossil energy resources such as oil and coal is accelerated, interest in alternative energy that can replace them is increasing. Among them, wind power generation converts the kinetic energy of the wind into electrical energy, and has no problems with resource depletion or environmental pollution. Accordingly, the power generation capacity of the wind generator is also increasing in size from 1,000KW to 2,000KW.

The wind power generator is provided with a windmill, a power generation unit equipped with a rotational force transmission mechanism, a generator, and the like on the top of the tower to be rotatable about the tower. In this power generation unit, a power cable for power transmission is installed. As the power generation unit rotates left and right, the cable is twisted at a large angle. Generally the torsion angle reaches up to ± 540 degrees.

In addition, in the case of power cables applied to wind power generators of 1MW or more, a high voltage of 15 kV or more is added, so that a semi-conductive or conductive metal shielding layer is inevitably applied inside and outside of the insulator to prevent high voltage discharge and breakdown voltage of the cable insulator. Will be.

Figure 1 shows a cross-sectional structure of such a power cable for a wind generator. Referring to FIG. 1, a conventional wind generator power cable includes one or more power lines 10 extending along a length direction, an inner sheath layer 20, a binding tape 30, and an outer sheath layer 40. The power line 10 has a configuration in which a center conductor 11, an inner semiconducting layer 12, an insulating layer 13, an outer semiconducting layer 14, and a metal shielding layer 15 are sequentially arranged.

The center conductor 11 is a composite twisted-pair structure in which metal wires made of copper, aluminum, iron, nickel, and the like are intentionally twisted around a central axis of the cable, and the outer circumference of the center conductor 11 is the inner semiconducting layer 12. Wrapping In addition, the insulating layer 13 and the outer semiconducting layer 14 are wrapped around the outer circumference of the inner semiconducting layer 12. Particularly, in the case of high-voltage power transmission, a metal shielding layer 15 made of metal is formed on the outer circumference of the outer semiconducting layer 14 to block leakage of unstable power generated inside the center conductor 11 so that the center conductor 11 is formed. It has a structure that prevents current from flowing through the liver.

The conventional wind generator power cable is subjected to repeated torsional behavior inside the cable due to the continuous rotational movement of the nacelle portion in which the tower upper generator is positioned according to the wind generator operating environment after installation in the tower of the wind generator. Such torsional behavior may cause mechanical breakage due to friction, bending, torsion, etc. between power lines in the cable.

For this reason, power cables for wind generators should be manufactured with sufficient flexibility and durability to meet the external tension load and torsion environment, and the center conductor 11 and the metal shielding layer 15 to satisfy these product characteristics. ) Shall be manufactured so that sufficient material strength and elongation can be compensated.

However, in the case of the power line 10 in which the metal shielding layer 15 is located outside, the metal shielding layer 15 may be easily cut and broken by repeated twisting and fatigue loads. Due to the gap between the interfacial layers of the material, there is a problem that the power shielding performance is deteriorated and leaks are likely to occur. In particular, the metal shielding layer 15 has a difficulty in satisfying flexibility such as long-term durability and bending for torsion, which is a main characteristic of the wind power generator power cable, due to the use of a metal material. When the metal shielding layer 15 is broken, there is a problem that high voltage dielectric breakdown may occur and lead to an accident because it cannot serve as a return current of a fault current when a ground fault or a short circuit accident occurs.

The present invention has been made to solve the problems of the prior art as described above, by improving the structure of the metal shielding layer of the outer portion of the power line included in the power cable, satisfies the mechanical and electrical properties and improve the flexibility for high pressure It is an object of the present invention to provide a power cable for a wind generator with improved long-term durability by shielding or grounding power and maintaining excellent torsional and bending durability.

According to an aspect of the present invention, there is provided a power cable, including at least one of an inner semiconducting layer surrounding an outer circumference of a center conductor and the center conductor, an insulating layer, and an outer semiconducting layer and extending in a longitudinal direction. More power lines; A metal shielding layer surrounding an outer circumference of each power line to shield or ground unstable power generated from the power lines; And an inner and outer sheath layer surrounding the at least one power line, wherein the metal shielding layer is made of element wires of element wire diameters, and the element wires are formed by wiping in a single direction.

Preferably, the metal shielding layer is formed by wiping a ray angle, which is an angle of the element wire to the longitudinal direction of the power line, to satisfy 60 ° to 70 °.

Preferably, the metal shielding layer has a diameter of 0.1 mm to 0.7 mm.

Preferably, the metal shielding layer has an elongation of at least 15% of the element wire.

Preferably, the metal shielding layer has a tensile strength of 20 kgf / mm 2 or more.

According to the present invention, by improving the structure of the metal shielding layer on the outer portion of the power line included in the power cable, it satisfies the mechanical and electrical properties and improves the flexibility to allow the shielding or grounding of the high-voltage power, while providing excellent torsional and bending durability It is possible to provide a power cable with improved long-term durability. In addition, when installing a power cable with a metal shielding layer with improved torsional and bending durability in a tower of a wind generator, it can act as a return of fault current due to a ground fault or a short circuit accident in the environment of use. It is effective to prevent accidents by preventing them.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and, together with the description, And shall not be interpreted.
1 is a cross-sectional view showing the configuration of a power cable for a conventional wind generator.
2 is a cross-sectional view showing the configuration of a power cable for a wind generator according to the present invention.
3 is a diagram illustrating a configuration of the power line of FIG. 2.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

2 is a cross-sectional view showing the configuration of a power cable for a wind generator according to the present invention, Figure 3 is a view showing the configuration of the power line of FIG.

Referring to FIG. 2, the power cable for a wind generator according to the present invention includes at least one power line 100 extending in a longitudinal direction and an inner and outer sheath layer 200 surrounding the at least one power line 100. 400).

The power line 100 is composed of one or more in order to transmit the high-voltage power generated from the wind generator, in Figure 2 is a three-phase conductor, the number of power lines 100 is shown as three. However, the present invention is not limited by the number of power lines 100.

The power line 100 has a configuration in which the center conductor 110, the inner semiconducting layer 120, the insulating layer 130, the outer semiconducting layer 140, and the metal shielding layer 150 are sequentially disposed.

The center conductor 110 is a composite stranded wire structure made by twisting a plurality of metal wires at a constant pitch, and the metal wires are made of a single metal or at least two metal alloys. That is, the metal element wire is made of a metal selected from copper, aluminum, iron, nickel or an alloy of these metals.

The inner semiconducting layer 120 binds the twisted metal wires by surrounding and surrounding the outer circumference of the center conductor 110, and also uniformly distributes the electric field induced from the surface of the center conductor 110. The inner semiconducting layer 120 is made of an EVA-based polymer resin layer that is extruded.

The insulating layer 130 is an insulating polymer resin layer that is extruded on the outer circumference of the central conductor 110 surrounded by the inner semiconducting layer 120 and is made of polyurethane (PU), polystyrene (PS), polyolefin (PO), and polyvinyl. Chloride (PVC), polycarbonate (PC), and ethylene propylene rubber (EPR).

The outer semiconducting layer 140 is a layer surrounding the outer circumference of the insulating layer 130 and serves to uniformly disperse the electric field like the inner semiconducting layer 120 and is an extrusion-based polymer resin layer of the EVA series Is done.

Meanwhile, the inner semiconducting layer 120 and the outer semiconducting layer 140 may be made of a binding tape. In this case, a tape woven from cotton yarn, a polyester tape (for example, Teflon tape) or a polystyrene tape may be used. have.

The metal shielding layer 150 is a layer surrounding the outer circumference of the outer semiconducting layer 140 and is made of a nonmagnetic material to serve as a ground for the power line 100 and a fault current in the event of a ground fault and a short circuit.

In the present invention, the conventional metal shielding layer is a braided braided form or a metal tape form is made of the element wire of the wire diameter and is formed by wiping in a single direction to improve the metal shielding layer 150 of the wind generator It has a structure to disperse the concentrated stress applied from bending, bending, buckling, etc. by repeated torsional behavior according to the use environment. Through this, the metal shielding layer 150 may be prevented from being damaged.

As shown in FIG. 3, the metal shielding layer 150 is formed of element wires 151 having a wire diameter, and the element wires 151 are formed by wiping in a single direction.

The metal shielding layer 150 is formed by wiping a ray angle α, which is an angle between the element wires 151 and the length direction of the power line 100, to satisfy 60 ° to 70 °. At this time, when the ray angle α is 60 ° or less, deformation due to torsion may occur largely and the metal shielding layer 150 may be damaged. In addition, when the ray angle α is 70 ° or more, the time required for wiping the element wire 151 becomes long, and the element wires 151 overlap each other during the wiping operation, so that the material requirement is not easy. It is not preferable because it can be increased.

The metal shielding layer 150 preferably has a diameter of the element wire 151 of 0.1 mm to 0.7 mm. At this time, when the diameter of the element wire 151 is 0.1 mm or less, there exists a problem that elongation and strength characteristics are low, and workability is remarkably inferior. In addition, when the diameter of the element wire 151 is 0.7 mm or more, there is a problem of inferior flexibility, which is not preferable.

In the metal shielding layer 150, the elongation of the element wire 151 is 15% or more, and the tensile strength is preferably 20 kgf / mm 2 or more. At this time, when the elongation of the element wire 151 is 15% or less, or the tensile strength is 20kgf / mm 2 or less, cracks may occur during long-term use and disconnection may occur, which is not preferable.

The power cable employing the metal shielding layer 150 having such a structure satisfies mechanical and electrical properties and improves flexibility to shield or ground high voltage power while maintaining excellent torsional and bending durability. Long-term durability can be improved.

The inner and outer sheath layers 200 and 400 are layers that surround and protect the power lines 100, and the inner sheath layer 200 directly surrounds and protects the power lines 100, and the outer sheath layer 400. ) Is provided on the outermost side of the cable to protect the cable from external impact or corrosion. In addition, a binding tape 300 may be interposed between the inner sheath layer 200 and the outer sheath layer 400 to strengthen the assembly structure of the power line 100.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments of the present invention and comparative examples in order to help the understanding of the present invention. However, the embodiments are only illustrative of the present invention, and the scope of the present invention is not limited thereto.

Torsional Strength Test According to Metal Shield Layer Structure Example 1 , Comparative Example 1 )

A power cable specimen (Example 1) according to the present invention and a conventional power cable siphon (Comparative Example 1) were prepared.

Example 1 according to a preferred embodiment of the present invention by twisting the tin-plated copper with a diameter of 0.4mm to produce a center conductor of 35SQ standard, the inner semiconducting layer of EVA series, the insulating layer of EPR material on the outer circumference of the center conductor , The outer semiconducting layer of the same material as the inner semiconducting layer was sequentially extruded, and the outer circumference of the copper with 0.45 mm in diameter, 20% elongation and 20 kgf / mm in tensile strength so that the ray angle is 60 ° To form a metal shielding layer to prepare a power line. The three power lines were fabricated and extruded EVA inner and outer sheath layers to produce power cable specimens.

In Comparative Example 1, a 35SQ standard center conductor was manufactured by twisting tin-plated copper having a diameter of 0.4 mm, and the outer periphery of the center conductor was the same as that of the EVA-based inner semiconducting layer, the EPR insulating layer, and the inner semiconducting layer. The outer semiconducting layer of the material was sequentially extruded, and a power shield was manufactured by forming a metal shielding layer made of a copper material having a diameter of 0.18 mm and a braiding type on the outer circumference thereof. The three power lines were fabricated and extruded EVA inner and outer sheath layers to produce power cable specimens.

Each specimen was installed in an MTS axial torsional tester, and repeated 5000 times at 108 degrees / m and then observed whether or not the specimen was broken.

As a result, in Example 1, there were no cracks or breakages in the inner semiconducting layer, the insulating layer, and the outer semiconducting layer in the power line, and no damage was caused to the metal shielding layer and the center conductor so that the breakage rate was 0%. On the other hand, in Comparative Example 1, there were no cracks or breakages in the inner semiconducting layer, the insulating layer, and the outer semiconducting layer inside the power line, and no damage occurred in the center conductor, but overall breakage occurred in the metal shielding layer. Therefore, it can be seen that the power cable of Example 1 exhibits high durability against repeated torsional deformation compared to Comparative Example 1.

Metal shielding layer Lay  Torsional strength test according to angle Example 2 , Comparative Example 2  4)

A power cable specimen (Example 2) and a power cable specimen (Comparative Examples 1 to 4) according to the present invention were prepared.

Example 2 according to a preferred embodiment of the present invention by twisting the tin-plated copper with a diameter of 0.4mm to produce a center conductor of 35SQ standard, the inner semiconducting layer of EVA series, the insulating layer of EPR material on the outer circumference of the center conductor , The outer semiconducting layer of the same material as the inner semiconducting layer was sequentially extruded, and the outer circumference of the copper was 0.45 mm in diameter, 20% elongation, and 20 kgf / mm2 tensile strength of copper so that the ray angle was 69.5 °. To form a metal shielding layer to prepare a power line. The three power lines were fabricated and extruded EVA inner and outer sheath layers to produce power cable specimens. Also, in Comparative Examples 2 to 4, the ray angle of the metal shielding layer was changed and the remaining elements except for the same were manufactured in the same manner.

Each specimen was installed in an MTS axial torsional tester, repeated 5000 times at 180 degree / m, and the number of break strands of each wire forming the metal shield layer of the specimen was measured, and the results are shown in Table 1 below. . At this time, the breakage result was expressed as the breakage rate (%) obtained by dividing the number of break strands by the total number of bases.

Example 2 Comparative Example 2 Comparative Example 3 Comparative Example 4 Ray angle 69.5 55 40.4 27.8 % Failure rate 0 3.5 68.8 45.3

As can be seen from Table 1, in Comparative Examples 2 to 4 having a ray angle of 60 ° or less, breakage occurred in the element wires forming the metal shielding layer. In particular, the breakage rate increased as the ray angle became smaller and then 40 °. It showed the maximum breakage rate in the vicinity and tended to decrease again. However, it was confirmed experimentally that breakage still occurred. In addition, when larger than 70 °, the wires burned to each other, resulting in uneven shielding. On the other hand, in Example 2, when the ray angle was 69.5 °, no breakage occurred in the element wire forming the metal shielding layer. Accordingly, it can be seen that the power cable of Example 2, which has a lay angle of 69.5 degrees, exhibits high durability against repeated torsional deformation, as compared to Comparative Examples 2 to 4 having a lay angle of 60 degrees or less.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be understood that various modifications and changes may be made without departing from the scope of the appended claims.

100: power line 110: center conductor
120: inner semiconducting layer 130: insulating layer
140: outer semiconducting layer 150: metal shielding layer
200: inner sheath layer 300: binding tape
400: outer sheath layer

Claims (5)

At least one power line consisting of an inner semiconducting layer, an insulating layer, and an outer semiconducting layer which surround the center conductor and the outer circumference of the center conductor in order;
A metal shielding layer surrounding an outer circumference of each power line to shield or ground unstable power generated from the power lines; And
An inner and outer sheath layer surrounding the at least one power line,
The metal shielding layer is made of a wire of the element diameter, the power cable, characterized in that the wire is formed by wiping in a single direction. The method of claim 1,
The metal shielding layer is a power cable, characterized in that formed by wiping so that the lay angle (Lay Angle) that is the angle that the element wires and the longitudinal direction of the power line satisfies 60 ° ~ 70 °. The method of claim 2,
The metal shielding layer is a power cable, characterized in that the diameter of the element wire is 0.1mm to 0.7mm. The method of claim 3,
The metal shielding layer, the power cable is characterized in that the elongation of the wire is 15% or more. 5. The method of claim 4,
The metal shielding layer has a tensile strength of 20 kgf / mm 2 or more.

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