KR100981239B1 - An Electric Power Cable For Windturbine And Method For Producing The Same - Google Patents

Abstract

 The present invention relates to a power cable for a wind generator for transmitting power generated from the wind generator. The power cable includes a center conductor in which a plurality of metal wires are gathered, a binding tape, an insulation layer, and an outer sheath that sequentially surround the outer circumference of the center conductor, wherein the insulation layer has a tensile strength from the center to the outside. It has a gradually decreasing strength gradient characteristic.

Wind turbine, power cable, strength gradient, insulation layer

Description

An Electric Power Cable For Windturbine And Method For Producing The Same}

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, wind power generation has emerged as an alternative to fossil fuels and has continued to grow rapidly. Since 2005, new generation capacity has grown at an annual average of 36%.

Accordingly, the power generation capacity of the wind generator is also increasing in size from 1,000Kw to 2,000Kw.

1 is a schematic configuration diagram of a conventional wind generator. Referring to FIG. 1, in the wind generator 10, a power generation unit including a windmill 12 and a rotational force transmission mechanism, a generator, and the like is rotatably installed around 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 power cable is also twisted at a large angle. Generally the torsion angle reaches up to ± 540 °.

2 shows a cross-sectional structure of such a power cable for a wind generator. Referring to FIG. 2, the conventional power cable has a configuration in which the center conductor 100, the binding tape 101, the insulating layer 102, and the outer sheath 103 are sequentially arranged.

The center conductor 100 is a composite stranded structure in which a plurality of copper wires or copper alloy wires are intentionally twisted about a central axis of a cable, and a binding tape 101 surrounds the outer circumference of the center conductor 100. In addition, on the outer circumference of the binding tape 101, the insulating layer 102 made of synthetic rubber and the outer sheath 103 made of PVC are positioned.

In such a conventional power cable, repeated twisting behavior is applied to the power cable installed in the power generation unit as the power generation unit rotates with respect to the tower. Due to such torsional behavior, the metal wires forming the center conductor may be easily broken or broken by rubbing or bending (eg, bending, bending, buckling) with each other.

To solve this problem, it is necessary to increase the mechanical strength of the insulating layer or the outer sheath to minimize the transmission of external shocks to the center conductor. However, in order to enhance the mechanical strength, there is only a method of increasing the thickness of the sheath layer (insulating layer and the external sheath) or increasing the material strength of the sheath layer.

However, increasing the thickness of the sheath layer is contrary to the trend of miniaturization of the cable, and increasing the material strength of the sheath layer sacrifices the flexibility of the sheath layer, and the sheath layer may be destroyed by a large external impact.

Therefore, there is a need for the development of a power cable that is resistant to torsional deformation while at the same time having flexibility for large bending radii.

It is an object of the present invention to provide a power cable for a wind power generator which is robust against torsional deformation.

 Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

A power cable according to an aspect of the present invention includes a center conductor in which a plurality of metal wires are gathered, a binding tape, an insulation layer, and an outer sheath that sequentially surround the outer circumference of the center conductor, wherein the insulation layer is formed at the center. It has a strength gradient characteristic that the tensile strength gradually decreases toward the outside. In addition, the polymer resin constituting the insulating layer has an elastic gradient characteristic in which the elastic modulus gradually increases from the center to the outside because the degree of crosslinking decreases from the center of the cable to the outside.

In addition, the center conductor is formed of a composite twisted pair unit in which several strands of metal wires are twisted at a constant pitch.

In addition, a method of manufacturing a power cable according to another aspect of the present invention, comprising the steps of forming a central conductor by intentionally twisting several strands of metal strands to form a composite stranded wire; Surrounding the outer circumference of the center conductor with a binding tape; Extruding an insulating polymer resin on the outside of the binding tape to form an insulating layer, but forming a strength gradient insulating layer whose tensile strength gradually decreases from the center to the outside; And forming an outer sheath outside of the insulating layer. In addition, the strength gradient insulating layer also has an elastic gradient characteristic that the elastic modulus gradually increases from the center to the outside.

This strength gradient insulating layer is molded by extruding using an extrusion machine in which the extrusion temperature is lowered from the center to the outside.

The insulating layer (or strength gradient insulating layer) has an inner wall in contact with the binding tape and an outer wall in contact with the outer sheath, the inner wall has a tensile strength of 1.5 kgf / mm 2 or more, an elastic modulus of 200 kg / cm 2 or less, and the outer wall is The tensile strength is 1.0 kgf / mm 2 or less, and the modulus of elasticity is 400 kg / cm 2 or less.

The power cable according to the present invention not only has strong durability against repeated torsional deformation, but also the flexibility of the sheath layer against large bending. Thus, the power cables of the present invention are suitable for harsh environments where frequent torsional deformations and large bendings are applied. In particular, the power cable of the present invention exhibits very good properties when used for a wind generator.

Hereinafter, the present invention will be described in detail with reference to the drawings. In each figure, the same reference numerals indicate the same or equivalent components.

3 is a longitudinal sectional view of a power cable for a wind generator according to the present invention. Referring to FIG. 3, the power cable 200 of the present invention has a center conductor 201 at the center of the cable, and a binding tape 202, an insulating layer 203, and an outer circumference of the center conductor 201 in order. The outer sheath 204 is arranged in sequence.

The center conductor 201 is a composite twisted pair unit in which a plurality of metal wires are intentionally twisted. The metal wires are made of a single metal or an alloy of at least two metals. That is, the metal element wire is made of a metal selected from copper (Cu), aluminum (Al), iron (Fe), nickel (Ni) or an alloy of these metals. The center conductor 201 preferably has an elongation of 15% or more and a tensile strength of 27 kgf / mm 2 or less.

The binding tape 202 binds twisted metal wires by surrounding and surrounding the outer circumference of the center conductor 201. The binding tape 202 may be a cotton woven tape, a polyester tape (for example, tetron tape), a polystyrene tape, or the like. The binding tape 202 preferably has an elongation of 50% or more and a tensile strength of 6 kgf / mm 2 or less.

The insulating layer 203 is an insulating polymer resin layer that is extruded to the outer circumference of the center conductor 201 bound by the binding tape 202 and minimizes the transmission of external torsional strain to the center conductor. Should have flexible physical properties. To this end, the insulating layer 203 is characterized in that the tensile strength and elastic modulus of the inner region adjacent to the binding tape 202 and the outer region adjacent to the outer sheath 204 are different. That is, the inner region, which should have toughness in torsional deformation, has a relatively high tensile strength and a relatively low modulus of elasticity, while the outer region, which should have flexibility for large bends, has a relatively low tensile strength and a relatively high It is set to have an elastic modulus.

Referring to FIG. 3, when the radius of the surface in contact with the binding tape 202 is r _i and the radius of the surface in contact with the outer sheath 204 is r _f , the radius r of the insulating layer 203 is at r _i . As it increases to r _f (ie, from center to out), the tensile strength gradually decreases, and the modulus of elasticity has a strength gradient and elastic gradient that gradually increase.

The insulating layer 203 is formed of a polymer resin selected from the group consisting of polyurethane, polystyrene, polyolefin, polyvinyl chloride, polycarbonate, ethylene propylene rubber (EPR), and the like. These polymer resins are all substances whose degree of crosslinking varies with temperature (or degree of light irradiation). Therefore, it is possible to form a gradient with respect to tensile strength and modulus of elasticity by varying the degree of crosslinking by forming a gradient at a temperature heated as the radius r increases from r _i to r _f during extrusion of the insulating layer. . That is, by lowering the heating temperature from the center to the outside at the time of extrusion molding, the degree of crosslinking can be lowered from the inner region to the outer region. Accordingly, the tensile strength of the insulating layer is lowered from the center to the outside, and the elastic modulus is increased from the center to the outside.

For example, the elongation rate of the polymer resin layer constituting the insulating layer 203 is preferably 200% or more, and the insulating layer (hereinafter, the inner wall) at the point r _i has a tensile strength of 1.5 kgf / mm 2 or more and an elastic modulus of 200 kg. / Cm 2 or less, and the insulating layer (hereinafter, the outer wall) at the point r _f is preferably 1.0 kgf / mm 2 or more in tensile strength and 400 kg / cm 2 or less in elastic modulus.

On the outer circumference of the insulating layer 203, an outer sheath 204 made of PVC is extruded to a certain thickness. This outer sheath 204 preferably has an elongation of 120% or more and a tensile strength of 2.0 kgf / mm 2 or less.

The power cable formed of this structure has a relatively high tensile strength and a low modulus of elasticity of the sheath layer close to the center conductor, and the tensile strength of the sheath layer is lowered and the modulus of elasticity is higher as the distance from the center conductor is increased. As a result, it is robust against bite deformation and can exhibit more flexible elasticity during bending.

Hereinafter, a brief look at a method of manufacturing a power cable for a wind generator of the above-described structure.

First, a plurality of strands of metal wires of a constant diameter are prepared, and the metal conductors are passed through the side wound device to form a twist of a constant pitch to produce a center conductor 201. Winding the binding tape 202 on the outer circumference of the center conductor 201 thus manufactured, and passing through an extrusion molding machine having a constant temperature gradient, the tensile strength gradually decreases as the radius increases, and the insulating layer (the elastic modulus gradually increases) 203). By further extruding the PVC outer sheath 204 on the insulating layer 203, the wind power generator power cable according to the present invention is completed.

Hereinafter, a power cable according to a specific embodiment of the present invention will be described in comparison with a comparative example.

Example

Twist 1830 copper wires of 0.012 mm φ to produce a center conductor having a diameter of 22 mm, an elongation rate of 20%, and a tensile strength of 25 kgf / mm2. Winding a Tron Tape, the inner wall has a constant tensile strength of 1.9 kgf / mm2, an elastic modulus of 380 kg / cm2, an outer wall of 1.2 kgf / mm2, and an elastic modulus of 195 kg / cm2. The tensile strength is reduced, and the modulus of elasticity is extruded from an insulating layer made of polyurethane with a thickness of 2.8 mm and an elongation of 205%. A power cable specimen was manufactured by extruding an outer sheath made of PVC having a thickness of 3.2 mm, an elongation of 125%, and a tensile strength of 1.8 kgf / mm 2 on the outer circumference of the insulating layer.

Comparative example

Twist 1830 copper wires of 0.012 mm φ to produce a center conductor having a diameter of 22 mm, an elongation rate of 20%, and a tensile strength of 25 kgf / mm2, and have a thickness of 0.03 mm, an elongation rate of 55%, and a tensile strength of 5 kgf / mm2 on the outer circumference of the center conductor. The Tron tape is wound and extruded a polyurethane insulation layer having a thickness of 2.8 mm, an elongation of 205%, a tensile strength of 1.1 kgf / mm 2, and an elastic modulus of 240 kg / cm 2. At this time, the tensile strength and the elastic modulus of the insulating layer have a uniform value with respect to the radial direction. A power cable specimen was manufactured by extruding an outer sheath made of PVC having a thickness of 3.2 mm, an elongation of 125%, and a tensile strength of 1.8 kgf / mm 2 on the outer circumference of the insulating layer.

Torsion Fatigue Strength Test

The specimen of Example and the specimen of Comparative Example were each installed in an MTS axial torsional tester, and after 15,000 repetitions at 144 degree / m, the number of strands of breakage of the metal wire constituting the center conductor was measured, and the results are shown in Table 1. Indicated. At this time, the same test was conducted three times in order to increase the accuracy of the test.

Example Comparative example Breakage Breakage rate [%] Breakage Strands [pcs] Breakage rate [%] Primary 61 strands 3% 233 strands 13% Secondary 29 strands 1.6% 353 strands 19% 3rd 23 strands 1.3 245 strands 13%

Here,% failure represents the percentage of the number of strands broken against the total number of strands (1,830 strands).

  As can be seen from Table 1, the comparative example showed a breakage rate of 10% or more while the example showed a breakage rate of 3% or less. Thus, it can be seen that the power cable of the example shows a higher durability against repeated torsional deformation than the comparative example.

In the above described with reference to the accompanying drawings, preferred embodiments of the present invention in detail. However, embodiments of the present invention can be variously modified or applied by those skilled in the art, the scope of the technical idea according to the present invention should be determined by the claims to be described later will be.

The following drawings, which are attached to this specification, illustrate exemplary embodiments of the present invention, and together with the detailed description of the present invention, serve to further understand the technical spirit of the present invention. It should not be construed as limited to.

1 is a side view of a wind generator.

2 is a cross-sectional view of a power cable for a conventional wind generator.

3 is a cross-sectional view of a power cable for a wind generator according to the present invention.

<Explanation of symbols for the main parts of the drawings>

201: center conductor 202: binding tape

203: insulating layer 204: outer sheath

Claims (10)

A power cable comprising a center conductor in which a plurality of metal wires are gathered, a binding tape surrounding an outer circumference of the center conductor, an insulating layer, and an outer sheath, And the insulating layer has a strength gradient in which the tensile strength gradually decreases from the center of the cable to the outside. The method of claim 1, And the insulating layer has an elastic gradient in which the elastic modulus gradually increases from the center of the cable to the outside. The method according to claim 1 or 2, The polymer resin constituting the insulating layer, the cross-linking degree gradually decreases toward the outside from the center of the cable power cable, characterized in that. The method of claim 3, wherein The central conductor is a power cable, characterized in that formed by twisting a plurality of strands of metal wire to a constant pitch. The method of claim 4, wherein The insulating layer has an inner wall in contact with the binding tape and an outer wall in contact with the outer sheath, The inner wall has a tensile strength of 1.5 kgf / mm 2 or more, an elastic modulus of 200 kg / cm 2 or less, The outer wall has a tensile strength of 1.0 kgf / mm 2 or less and an elastic modulus of 400 kg / cm 2 or less. The method of claim 5, And the elongation of the insulating layer is 200% or more. Intentionally twisting several strands of metal wires to form a central conductor; Surrounding the outer circumference of the center conductor with a binding tape; Extruding an insulating polymer resin on the outside of the binding tape to form an insulating layer, but forming a strength gradient insulating layer whose tensile strength gradually decreases from the center to the outside; Forming an outer sheath outside the insulation layer. The method of claim 7, wherein The strength gradient insulating layer is a method of manufacturing a power cable, characterized in that the elastic modulus gradually increases from the center to the outside. The method of claim 8, The strength gradient insulating layer is a power cable manufacturing method characterized in that it is manufactured using an extrusion molding machine that the extrusion temperature is lowered toward the outside from the center. The method of claim 9, The strength gradient insulating layer has an inner wall in contact with the binding tape and an outer wall in contact with the outer sheath, The inner wall has a tensile strength of 1.5 kgf / mm 2 or more, an elastic modulus of 200 kg / cm 2 or less, The outer wall has a tensile strength of 1.0 kgf / mm 2 or less, elastic modulus of 400 kg / cm 2 or less, characterized in that the power cable manufacturing method.

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