WO2018135700A1

WO2018135700A1 - Power cable

Info

Publication number: WO2018135700A1
Application number: PCT/KR2017/003511
Authority: WO
Inventors: 이인회; 남기준
Original assignee: 엘에스전선 주식회사
Priority date: 2017-01-20
Filing date: 2017-03-30
Publication date: 2018-07-26
Also published as: KR101867224B1

Abstract

The present invention relates to a direct current power transmission cable, particularly, an extra-high voltage underground or submarine cable. Specifically, the present invention relates to a power cable which: can suppress the occurrence of a deoiled void in an insulation layer and the like to suppress partial discharge, dielectric breakdown, etc., which may be caused by an electric field concentrated on the void, and thus extends lifespan of the cable; can effectively prevent degradation of dielectric strength, which may be caused by permeation of copper powder from a copper conductor into the insulation layer, and thus additionally extends lifespan of the cable; can restrain the damage of an insulation sheet, a semi-conductive film, etc. in spite of repetitive bending and unbending, thereby maintaining an interlayer structure formed by winding thereof; and can have improved flexibility and workability, and an improved bending property and pulling installation property, etc.

Description

Power cable

The present invention relates to direct current transmission power cables, in particular ultra-high voltage underground or submarine cables. Specifically, the present invention suppresses the occurrence of deoiling voids in the insulating layer and the like, thereby suppressing partial discharge, insulation breakdown and the like caused by the electric field concentrated in the voids, thereby extending the lifespan, and copper powder from the copper conductor is applied to the insulating layer. It effectively prevents the breakdown of the dielectric strength by penetrating, further extending the service life, and preventing the breakage of the insulating paper and the semiconducting film even after repeated bending and bending, thereby maintaining the interlayer structure formed by the winding thereof. The present invention relates to a power cable that can improve flexibility, flexibility, installation, workability, and the like.

As an insulating layer, a power cable using a polymer insulator such as crosslinked polyethylene (XLPE) is used.However, due to a problem of forming a space charge in a DC high electric field, an ultra-high voltage DC power transmission cable is impregnated with insulating oil in a cross winding insulating paper so as to surround a conductor. Paper-insulated cables having an insulating layer are used.

The geo-insulated cable includes an OF (Oil Filled) cable for circulating low-viscosity insulating oil, a Mass Impregnated Non Draining (MIND) cable impregnated with high-viscosity or medium viscosity insulating oil, and the OF cable transmits hydraulic pressure for circulation of the insulating oil. Due to the limitation in length, it is unsuitable for long distance transmission cables, and in particular, there is a problem that it is difficult to install insulating oil circulating equipment in the seabed, which is also unsuitable for submarine cables.

Therefore, MIND cable is commonly used for long distance direct current transmission or subsea high voltage cable. The MIND cable is formed by wrapping insulation paper such as kraft paper, semi-synthetic paper laminated with thermoplastic resin such as kraft paper and polypropylene resin when the insulation layer is formed in a plurality of layers, and an internal semiconducting layer inside and outside the insulation layer and The outer semiconducting layer may be formed by enclosing a semiconducting battery such as carbon black paper in a plurality of layers, and the insulating oil is impregnated in the semisynthetic paper, the semiconducting battery, and the like.

However, in the conventional MIND cable, the insulating paper which forms the insulating layer and the semiconducting layer by the heat generation of the conductor during the operation thereof, the insulating oil impregnated in the semiconductor battery, and the insulating oil filled in the gap generated when the insulating paper and the semiconductor battery are wound are expanded. The insulation oil contracts when the heating of the cable stops, and the heating of the conductor stops when the electricity is stopped, and the internal temperature of the cable starts to decrease, so that the insulation oil, the semi-conducting layer, the gap, or the interface between the layers is absent. Deoiling voids are formed, and partial discharge occurs due to an electric field concentrated in the voids generated by the insulating paper, resulting in a breakdown of the insulation.

On the other hand, as shown in FIG. 1, when forming the plurality of layers by transversely winding the semiconductor cell 10 to the conductor portion 20, a constant gap (gap) between the semiconductor cells wound to form each layer ( 30 is formed, and the gaps 30 formed in an arbitrary layer are generally applied with a gap right to be covered by the semiconductor cell 10 or the like constituting the outer and inner layers of the arbitrary layer, respectively. Even when winding insulating paper to form an insulating layer, a gap winding that is advantageous for securing a moving path of insulating oil is generally applied.

However, the conventional MIND cable is advantageous in terms of securing the movement path of the insulating oil when the insulating oil is impregnated when the insulating layer and the inner semiconducting layer are formed by the gap winding of the insulating paper, the semiconductor battery, etc. as described above, but is shown in FIG. As described above, copper powder of the conductor portion 20, in particular, copper powder from the copper stranded wire conductor is dispersed in the insulating oil, thereby easily penetrating into the insulating layer with the movement of the insulating oil, thereby causing a problem that the insulation strength is greatly reduced.

Therefore, it is possible to prevent deoiling voids from occurring in the inner semiconducting layer, the insulating layer, the outer semiconducting layer, the gap or the interface between the layers, and to suppress partial discharge and insulation breakdown due to the electric field concentrated in the voids, thereby reducing the insulation performance of the cable. Increasing the cable life and increasing the life of the cable, effectively preventing the copper from being penetrated into the insulating layer to lower the dielectric strength, there is an urgent need for a power cable that further extends the life.

The present invention suppresses deoiling voids in the inner semiconducting layer, the insulating layer, the outer semiconducting layer, the gap or the interlayer interface, and thus prolongs the lifespan by suppressing partial discharge and insulation breakdown due to the electric field concentrated in the voids. It is an object to provide a power cable.

Moreover, an object of this invention is to provide the electric power cable which extends a lifetime by effectively preventing copper powder from a copper conductor penetrating into an insulating layer, and falling insulation strength.

In addition, an object of the present invention is to provide a power cable capable of maintaining the interlayer structure formed by the winding of the insulating paper, semi-conducting film and the like is suppressed even after repeated bending and bending.

Further, an object of the present invention is to provide a power cable that can be improved in flexibility, flexibility, installation, workability and the like.

In order to solve the above problems, the present invention,

Conductor; An inner semiconducting layer surrounding the conductor; An insulating layer surrounding the inner semiconducting layer; An outer semiconducting layer surrounding the insulating layer; A metal sheath layer surrounding the outer semiconducting layer; And a cable protection layer surrounding the metal sheath layer, wherein the inner semiconducting layer is formed by a transverse winding of a semi-conductive film formed from a polymer composite material in which conductive particles are incorporated into a polymer resin. A power cable is provided.

Here, the polymer resin provides a power cable, characterized in that the melting point (Tm) is 120 ℃ or more.

In addition, the polymer resin is high density polyethylene (HDPE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyamide (PA), polypropylene (PP), polyvinylidene fluoride (PVDF), fluorine Provided is a power cable comprising at least one member selected from the group consisting of rubber and silicone rubber.

The conductive particles provide 10 to 50% by weight of carbon black based on the total weight of the polymer composite material.

Further, the polymer composite material is characterized in that it comprises 0.05 to 2% by weight antioxidant, 0.05 to 2% by weight thermal stabilizer and 0.05 to 2% by weight metal antioxidant based on the total weight of the polymer composite material, Provide the cable.

On the other hand, the inner semiconducting layer includes a plurality of layers formed by the transverse winding of the semiconducting film, the plurality of layers comprises at least one layer formed by the wrap winding of the semiconducting film, power cable To provide.

Here, the remaining layer other than the layer formed by the wrap winding of the semiconducting film of the plurality of layers includes a layer formed by the gap winding of the semiconducting film, provides a power cable.

In addition, at least one layer formed by the wrap winding of the semiconducting film, characterized in that it comprises a layer disposed directly above the conductor, provides a power cable.

And, at least one layer formed by the wrap winding of the semiconducting film provides an electric power cable, characterized in that the overlap rate is 20 to 60% of the overlapping ratio of the width of the semiconducting film forming it. .

Further, the plurality of layers of the semiconducting film is 2 to 25, the total thickness of the inner semiconducting layer is 0.1 to 3.0 mm, the width of the semiconducting film is characterized in that the power cable is 10 to 30 mm, to provide.

The insulating layer further includes a plurality of layers formed by the transverse winding of the insulating paper, and the plurality of layers includes a layer formed by the gap winding of the insulating paper.

On the other hand, the insulating layer is formed by the transverse winding of the insulating paper, the insulating paper includes kraft paper or semi-synthetic paper impregnated with insulating oil, the semi-synthetic paper is kraft (kraft) laminated on at least one side of the plastic film and the plastic film It provides a power cable, characterized in that it comprises a).

Here, the insulating layer is formed by sequentially stacking an inner insulating layer, an intermediate insulating layer and an outer insulating layer, and the inner insulating layer and the outer insulating layer are each formed of kraft paper impregnated with insulating oil, and the intermediate insulating layer Provided is a power cable, characterized in that formed from a semi-synthetic paper impregnated with insulating oil.

In addition, the insulating oil provides a power cable, characterized in that it comprises a high viscosity insulating oil.

Here, the high viscosity insulating oil provides a power cable, characterized in that the kinematic viscosity of 60 ℃ more than 500 centistokes (cSt).

On the other hand, the cable protection layer is characterized in that it comprises an inner sheath, a bedding layer, a metal reinforcing layer and an outer sheath, provides a power cable.

Here, the cable protective layer further provides a power cable, characterized in that it further comprises an outer wire and the outer serving layer.

The power cable according to the present invention improves the adhesion between the conductor and the semiconducting layer and suppresses the movement of insulating oil by replacing the semiconducting battery applied to form the inner semiconducting layer of the conventional cable with the polymer composite material and forming the deoiling voids. Minimize or avoid, thereby preventing the occurrence of partial discharge, insulation breakdown, etc. due to the electric field concentrated in the voids exhibits an excellent effect of extending the life.

In addition, the power cable according to the present invention by forming at least one of the plurality of layers formed in the process of drawing the semi-conducting film to form the inner semi-conducting layer on the conductor portion by the wrap winding of the semi-conducting film, By effectively preventing copper powder from penetrating into the insulating layer and lowering the dielectric strength, an excellent effect of extending the service life is obtained.

And, the power cable according to the present invention by precisely controlling the overlap rate of the semi-conducting film wrapped in the plurality of layers formed by the winding of the semi-conducting film and the remaining layer is formed by the gap winding of the semi-conducting layer, iterative bending The breakage of the semiconducting film is suppressed even in the bending and bending, and the interlayer structure formed by the winding thereof can be maintained.

Furthermore, the power cable according to the present invention exhibits an excellent effect of improving flexibility, flexibility, laying property, workability, etc. by avoiding unnecessary increase in outer diameter.

FIG. 1 schematically shows a case in which a semiconductor cell is gap-wound on a conductor part in a conventional power cable, and copper from the conductor part penetrates into the insulating layer on the semi-conducting layer through the movement path of the insulating oil formed by the gap winding. .

Figure 2 schematically shows the cross-sectional structure of one embodiment of a power cable according to the invention.

FIG. 3 schematically illustrates a longitudinal cross-sectional structure of the power cable shown in FIG. 2.

4 is a graph schematically illustrating a process in which an electric field is relaxed in an insulating layer of a power cable according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail. However, the invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosure may be made thorough and complete, and to fully convey the spirit of the present invention to those skilled in the art. Like numbers refer to like elements throughout.

2 and 3 schematically show the cross-sectional and longitudinal cross-sectional structures of one embodiment of a power cable according to the invention, respectively.

As shown in FIGS. 2 and 3, the power cable according to the present invention includes a conductor 100, an inner semiconducting layer 200 surrounding the conductor 100, and an insulating layer surrounding the inner semiconducting layer 200 ( 300, an outer semiconducting layer 400 surrounding the insulating layer 300, a metal sheath layer 500 surrounding the outer semiconducting layer 400, and a cable protection layer surrounding the metal sheath layer 500 ( 600) and the like.

The conductor 100 is a movement path for electric current for transmission, and has high electrical conductivity to minimize power loss, and has high purity copper (Cu), aluminum (Al), etc. having appropriate strength and flexibility required for use as a conductor of a cable. In particular, it may be made of a linkage line having a high elongation and a high conductivity. In addition, the cross-sectional area of the conductor 100 may be different depending on the amount of power transmission, the use of the cable.

Preferably, the conductor 100 may be composed of a circular compression conductor compressed by placing a flat element wire in multiple layers on a flat conductor or a circular center line composed of multiple flat angle wires on a circular center line. Since the conductor 100 made of a flat conductor formed by a so-called keystone method has a high conductor area ratio, it is possible to reduce the outer diameter of the cable and to form a large cross-sectional area of each element wire. It is economical to reduce. Moreover, since there are few voids in the conductor 100 and the weight of the insulating oil contained in the conductor 100 can be made small, it is effective.

The inner semiconducting layer 200 suppresses electric field distortion and electric field concentration due to surface unevenness of the conductor 100, thereby interfacing the inner semiconducting layer 200 and the insulating layer 300 or inside the insulating layer 300. It functions to suppress partial discharge and insulation breakdown caused by electric field concentrated on.

As shown in FIG. 3, the inner semiconductive layer 200 includes a plurality of semi-conductive films formed from a polymer composite material formed by mixing conductive particles such as carbon black in a polymer resin. It can form by transverse winding in two layers.

The semiconducting film formed from the polymer composite material has an excellent adhesion to the conductor 100 when wound on the conductor 100 due to excellent elasticity, surface adhesiveness, etc., which is realized from the material thereof, and thus the conductor 100 and the inner semiconducting film. The gap between the front layer 200 and the gap between the internal semiconducting layer 200 and the insulating layer 300 may be effectively removed to more effectively suppress partial discharge and dielectric breakdown.

In addition, since the polymer composite material forming the semiconducting film does not pass the insulating oil, unlike the conventional semiconducting battery, the conductor 100, the conductor 100 and the semiconducting layer 200 by the heat generation of the conductor 100 when the cable is operated. It is possible to suppress the movement of the insulating oil between the outside of the cable to minimize or avoid the formation of deoiling voids.

Furthermore, the polymer composite material forming the semiconductive film may contain an insulating oil to some extent by impregnating the insulating oil. In this case, the semiconductive film is expanded by swelling, so that the conductor 100 and the internal semiconducting layer ( Partial discharge, dielectric breakdown, etc. can be further suppressed by effectively eliminating gaps and deoiling voids between the gaps 200 and gaps and voids between the internal semiconducting layer 200 and the insulating layer 300.

In the electric power cable of the present invention, the transverse winding of the semiconducting film to form the internal semiconducting layer 200 is performed when the internal semiconducting layer is formed through the extrusion process of the polymer composite material separately from the insulating paper winding process for forming the insulating layer. Compared to the conventional semiconductor cell, the semiconducting film has excellent adhesion with the conductor 100 and the internal semiconducting layer or the internal semiconducting layer in the conductor. It effectively suppresses the movement of insulating oil and expands when the insulating oil is contained, effectively eliminating gaps and voids between conductors and internal semiconducting layers, and gaps and voids between internal semiconducting layers and insulating layers. It can be minimized or avoided more effectively.

The polymer resin included in the polymer composite material forming the semiconductive film has a melting point (Tm) of 120 ° C. or higher in consideration of the high temperature environment applied during the insulation oil impregnation process and the heat generation of the conductor during cable operation, and should not be dissolved in the insulation oil. . Here, the melting point (Tm) of the polymer resin was measured while heating up at a temperature increase rate of 10 ° C./min from room temperature to 300 ° C. using a DSC (Differential Scanning Calorimeter) device.

The polymer resin is, for example, high density polyethylene (HDPE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyamide (PA), polypropylene (PP), polyvinylidene fluoride (PVDF), Fluorine rubber, silicone rubber, etc. may be included, and among these, it is preferable to select a material having high heat resistance such as polypropylene (PP).

The polymer composite material may include 10 to 50% by weight of conductive particles, such as carbon black, based on the total weight of the polymer composite material to implement semiconductive properties, and additionally 0.05 to 2% by weight of an antioxidant, 0.05 to 2% by weight of the thermal stabilizer, 0.05 to 2% by weight of the metal antioxidant, and the like.

As illustrated in FIG. 3, at least one layer 210 of the plurality of layers of the semiconducting film overlaps a portion of the width of the semiconducting film when the wrap winding of the semiconducting film, that is, the transverse winding of the semiconducting film, The remaining layers 220 are transversely wound so that a constant gap is formed between the semi-conductive film, that is, between the semiconducting films, and the gap is the semiconducting film. When a new semiconducting film is rolled on top of it, it is covered by the new semiconducting film and at the same time it can be rolled in such a way that it is repeatedly rolled so that a gap is formed between the new semiconducting films. Preferably, at least one layer formed by the wrap winding of the semiconductive film may include an innermost layer, that is, a layer in contact with the conductor 100.

Unlike the layer 220 formed by the gap winding of the semiconducting film, the layer 210 formed by the wrap winding of the semiconducting film may have a gap in the layer, that is, the same amount from the conductor 100. Since there is no passage therein, the copper powder is prevented from moving through the internal semiconducting layer 200 to the insulating layer 300, thereby effectively reducing the dielectric strength of the insulating layer 300 by the copper powder. It is possible to suppress, thereby extending the life of the power cable and at the same time avoid unnecessary increase in the outer diameter of the power cable can be improved flexibility, flexibility, installation, workability and the like.

Further, the layer 220 formed by the gap winding of the semiconducting film forming the remaining layer other than the layer 210 formed by the wrap winding of the semiconducting film may be a semiconductive film forming an arbitrary layer. Between the semiconducting films forming the outer and inner layers of the respective layers and the outermost layer are stably slid between the insulating layers, so that even if repeated bending and flexing are applied to the power cable, By preventing friction or collision between conductive films, the damage of the semiconducting film may be suppressed and the structure of the inner semiconducting layer 200 may be stably maintained.

Preferably, by disposing the layer 210 formed by the wrap winding of the semiconducting film directly on the innermost layer, that is, the conductor 100, the movement of the same from the conductor 100 can be blocked at the source. Instead, the overlapping portion between adjacent semiconducting films can be suppressed during bending of the power cable by adjusting an overlap rate, which is a ratio at which the semiconducting films overlap with each other when the wrapper of the semiconducting film is wrapped. It is possible to prevent the collision between the semiconducting film during bending, and as a result, it is possible to stably maintain the structure of the inner semiconducting layer 200 by suppressing the breakage of the semiconducting film.

Here, the number of the plurality of layers of the semiconducting film may be 2 to 25, whereby the total thickness of the inner semiconducting layer 200 may be about 0.1 to 3.0 mm, while the width of the semiconducting film is about It may be 10 to 30 mm, the overlap rate of the wrapper of the semiconducting film is formed by the outer diameter of the conductor 100, the width of the semiconducting film, wrap wrap of the semiconducting film in the inner semiconducting layer 200 It may be different depending on the position of the layer 210 to be, for example, may be 20 to 60%.

When the overlap rate of the semiconducting film is less than 20%, the overlapped portions between the semiconducting films are separated during the bending of the power cable, and the semiconducting films separated during the bending of the power cable are trying to overlap again. While the semiconducting film may be damaged due to a collision, the excess of the semiconducting film unnecessarily increases the productivity of the power cable due to the excessive overlap of the semiconducting film, and the outer diameter of the power cable is unnecessarily increased, resulting in flexibility, flexibility, laying property, and work. Sex and the like may be degraded.

Meanwhile, in forming the inner semiconducting layer 200, two or more semiconducting films may be simultaneously wrapped in the wrapper of the semiconducting film in order to continuously perform layer formation by the wrap winding and the gap winding of the semiconducting film. have.

The insulating layer 300 is formed by wrapping the insulating paper in a plurality of layers, and the insulating paper is, for example, using a kraft paper or a semi-synthetic paper in which a thermoplastic resin such as kraft paper and a polypropylene resin is laminated. Can be used.

According to a preferred embodiment of the present invention, the insulating layer 300 includes an inner insulating layer 310, an intermediate insulating layer 320 and an outer insulating layer 330, the inner insulating layer 310 and the outer The insulating layer 330 is made of a material having a lower resistivity than the intermediate insulating layer 320, whereby the inner insulating layer 310 and the outer insulating layer 330 are each connected to the conductor 100 when the cable is operated. To suppress the application of a high electric field formed by applying a direct current above the conductor 100 or directly below the metal sheath layer 500, and further suppress the deterioration of the intermediate insulating layer 320 It works for.

4 is a graph schematically illustrating a process in which an electric field is relaxed in an insulating layer of a power cable according to the present invention. As shown in FIG. 4, a direct current (DC) electric field is relaxed in the inner insulation layer 310 and the outer insulation layer 330 having a relatively low resistivity, thereby directly above the conductor 100 and directly below the metal sheath layer 500. In addition to effectively suppressing the application of a high electric field generated in a conventional DC cable, in the case of an impulse, an internal insulation layer is controlled while controlling the maximum impulse electric field applied to the intermediate insulation layer 320 to 100 kV / mm or less. Since the high impulse electric field applied is reduced to suppress the deterioration of the internal insulating layer 310, the deterioration of the intermediate insulating layer 320 can also be suppressed. Here, the impulse electric field means an electric field applied to the cable when an impulse voltage is applied to the cable.

Therefore, as shown in FIG. 4, the maximum impulse electric field value of the internal insulation layer 310 is designed to be smaller than the maximum impulse electric field value of the intermediate insulation layer 320 so that the high electric field does not act directly on or under the sheath. The maximum impulse electric field applied to the intermediate insulating layer 320 is an inner electric field of the intermediate insulating layer 320, and the inner electric field is the maximum impulse electric field of the intermediate insulating layer 320, for example, 100 kV / mm. By controlling below, the degradation of the intermediate insulating layer 320 can be suppressed.

Accordingly, the high electric field is suppressed from being applied to the inner insulation layer 310 and the outer insulation layer 330, particularly, a cable connection member vulnerable to an electric field, and further, the performance of the intermediate insulation layer 320 is maximized. In this way, the entire insulation layer 300 can be made compact, the deterioration can be suppressed, and the insulation strength and other physical properties of the insulation layer 300 can be suppressed from being lowered. As a result, the impulse withstand voltage is higher than that of the cable. Not only can it be done with a cable, but it can also suppress the shortening of the cable life.

The inner insulating layer 310 and the outer insulating layer 330 may be formed by transversely kraft paper made of kraft pulp and impregnated with an insulating oil, whereby the inner insulating layer 310 and the outer layer are impregnated. The insulating layer 330 may have a lower resistivity and a higher dielectric constant than the intermediate insulating layer 320. The kraft paper can be prepared by washing the kraft pulp with deionized water in order to remove the organic electrolyte in the kraft pulp to obtain good dielectric loss tangent and permittivity.

The intermediate insulating layer 320 may be formed by transversely winding a semi-synthetic paper having kraft paper laminated on the surface, the back surface, or both of the plastic film and impregnating insulating oil. The intermediate insulating layer 320 formed as described above has a higher resistivity, lower dielectric constant, higher DC dielectric strength, and impulse breakdown voltage than the inner insulating layer 310 and the outer insulating layer 330 because it includes a plastic film. Due to the high resistivity of the intermediate insulating layer 320, a direct current field is concentrated on the intermediate insulating layer 320 resistant to the DC electric field strength, and an impulse electric field is applied to the intermediate insulating layer 320 resistant to the impulse electric field at a low dielectric constant. By concentrating, the insulating layer 300 as a whole can be made compact, and as a result, the outer diameter of the cable can be reduced.

Here, the kraft paper or semi-synthetic paper which forms the inner insulating layer 310, the intermediate insulating layer 320 and the outer insulating layer 330, respectively, is transversely wound by a gap winding when transverse winding, so that the insulating oil is impregnated when the insulating oil is impregnated. It is advantageous to secure a passage so that the impregnation time can be shortened, and at the same time, the breakage of the kraft paper and the semi-synthetic paper can be effectively suppressed even when repeated bending and bending are applied to the power cable.

In the semi-synthetic paper forming the intermediate insulating layer 320, the plastic film is expanded by heat generation during operation of the cable to increase the oil resistance, the insulating oil impregnated in the insulating layer 300 is the outer semiconducting layer 400 It is possible to suppress the movement toward the side) to suppress the production of deoiled voids due to the movement of the insulating oil, and consequently to suppress electric field concentration and dielectric breakdown caused by the deoiled voids. Here, the plastic film may be made of a polyolefin resin such as polyethylene, polypropylene, polybutylene, fluorine resin such as tetrafluoroethylene-hexafluoro polypropylene copolymer, ethylene-tetrafluoroethylene copolymer, Preferably it may be made of a polypropylene homopolymer resin excellent in heat resistance.

In addition, the semi-synthetic paper may be 40 to 70% of the total thickness of the plastic film. When the thickness of the plastic film is less than 40% of the total thickness of the semi-synthetic paper, the resistivity of the intermediate insulating layer 320 may be insufficient, so that the outer diameter of the cable may be increased. Difficulties can be made difficult due to lack of distribution of insulating oil, which can be expensive.

The inner insulating layer 310 may have a thickness of 1 to 10% of the total thickness of the insulating layer 300, and the outer insulating layer 330 may have a thickness of 1 to 15% of the total thickness of the insulating layer 300. The intermediate insulating layer 320 may have a thickness of 75% or more of the total thickness of the insulating layer 300. As a result, the maximum impulse electric field value of the inner insulation layer 310 may be lower than the maximum impulse electric field value of the intermediate insulation layer 320. If the thickness of the inner insulation layer is increased more than necessary, the maximum impulse electric field value of the intermediate insulation layer 320 becomes larger than the allowable maximum impulse electric field value, and in order to alleviate this problem, the cable outer diameter increases. Done. In addition, the outer insulating layer 330 preferably has a sufficient thickness than the inner insulating layer, which will be described later.

In addition, in the present invention, the internal insulation layer 310 and the external insulation layer 330 having a small resistivity are provided to prevent the direct current high electric field from being applied directly above the conductor 100 and directly below the metal sheath layer 500. In addition, by designing the thickness of the intermediate insulating layer 320 having a high resistivity of 75% or more, it is possible to reduce the cable outer diameter while maintaining a sufficient dielectric strength.

As such, the inner insulation layer 310, the intermediate insulation layer 320, and the outer insulation layer 330 constituting the insulation layer 300 each have the precisely controlled thickness, so that the insulation layer ( 300 may have a desired dielectric strength while minimizing the outer diameter of the cable. In addition, the direct current and the impulse electric field applied to the insulating layer 300 can be most effectively designed on the electric field, and the high electric field of the direct current and the impulse is directly above the conductor 100 and directly below the metal sheath layer 500. It is possible to apply design means that can raise the dielectric strength of the cable connection member, which is particularly susceptible to electric fields, to a sufficient height.

Preferably, the thickness of the outer insulating layer 330 is greater than the thickness of the inner insulating layer 310, for example, in a cable of 500 kV DC, the thickness of the inner insulating layer 310 is 0.1 to 2.0 mm. The thickness of the outer insulating layer 330 may be 0.1 to 3.0 mm, and the thickness of the intermediate insulating layer 320 may be 15 to 25 mm.

Since the heat generated during soft connection for the cable connection according to the present invention is applied to the insulating layer 300 to melt the plastic film of the semi-synthetic paper forming the intermediate insulating layer 320, the plastic from the heat In order to protect the film, it is necessary to sufficiently secure the thickness of the outer insulating layer 330, and it is preferable to be formed thicker than the thickness of the inner insulating layer 310, the thickness of the outer insulating layer 330 The thickness of the internal insulating layer 310 is preferably 1 to 30 times.

In addition, the thickness of the sheet of semi-synthetic paper forming the intermediate insulating layer 320 is 70 to 200 ㎛, the thickness of the kraft paper forming the inner and outer insulating

layers

310, 320 may be 50 to 150 ㎛. The thickness of the kraft paper forming the inner and outer insulating

layers

310 and 320 is greater than that of the kraft paper constituting the semi-synthetic paper.

If the thickness of the kraft paper forming the inner and outer insulating layers (310,320) is too thin, the strength is insufficient, can cause mechanical damage when the paper rolls, and the number of side windings for forming the insulating layer of the desired thickness is increased Productivity of the kraft paper may be reduced, and the total volume of the gap between the kraft papers forming the main passage of the insulating oil when the kraft paper is transversely reduced may take a long time when the insulating oil is impregnated, and the content of the insulating oil impregnated is lowered, thereby reducing the desired dielectric strength. It may be difficult to implement.

Since the insulating oil impregnated in the insulating layer 300 is fixed without being circulated in the cable length direction like a low viscosity insulating oil used in a conventional OF cable, an insulating oil having a relatively high viscosity is used. The insulating oil may perform a lubrication role to facilitate the movement of the insulating paper when the cable is bent, as well as the function of implementing the desired dielectric strength of the insulating layer 300.

The insulating oil is not particularly limited but may be a medium viscosity insulating oil having a kinematic viscosity of 5 to 500 centistokes (cSt) at 60 ° C., or a high viscosity insulating oil having a kinematic viscosity of 60 ° C. or more at 500 centistokes (cSt) or more. . For example, one or more insulating oils selected from the group consisting of naphthenic insulating oils, polystyrene insulating oils, mineral oils, alkyl benzene or polybutene synthetic oils, heavy alkylates, and the like can be synthesized and used.

In the process of impregnating the insulating layer 300 with the insulating oil, the kraft paper constituting the inner insulating layer 310, the intermediate insulating layer 320 and the outer insulating layer 330 are formed to a desired thickness, respectively And each of the semi-synthetic paper is rolled up a plurality of times, and vacuum dried to remove residual moisture of the insulating layer 300, and then the insulating oil is heated to a high temperature impregnation temperature, for example, 100 to 120 ° C. under a high pressure environment. After the insulating oil is injected into the tank and the insulating oil is impregnated in the insulating layer 300 for a predetermined time under the condition, it may be performed by gradually cooling.

The outer semiconducting layer 400 suppresses the uneven charge distribution between the insulating layer 300 and the metal sheath layer 500 to mitigate electric field distribution, and the insulating layer may be formed from various types of metal sheath layers 500. 300) to physically protect.

The outer semiconducting layer 400 may be formed by a transverse winding of a semi-conductive paper, such as, for example, carbon paper treated with conductive carbon black on insulating paper, and preferably formed by the transverse winding of the semiconducting battery. The lower layer and the semiconductor cell and the metallization paper may include an upper layer formed to be transversely wound in a gap winding or an empty winding.

In addition, when the semiconductor cell and the metallization paper are wound in the upper layer, the metallization paper and the semiconductor cell may be alternately rolled so as to overlap, for example, about 20 to 80%.

Here, the metallized paper may have a structure in which a metal foil such as aluminum tape and aluminum foil is laminated on a base paper such as kraft paper or carbon paper, and the insulating oil easily penetrates into a semiconductor cell, an insulating paper, a semi-synthetic paper, and the like below the metal foil. A plurality of perforations may exist so that the semiconductor cell of the lower layer is in smooth electrical contact with the metal foil of the metallized paper through the semiconductor cell of the upper layer, and as a result, the external semiconducting layer 400 and the As the metal sheath layer 500 is in smooth electrical contact, a uniform electric field distribution may be formed between the insulating layer 300 and the metal sheath layer 500.

In addition, the outer semiconducting layer 400 may further include a copper wire direct fabric (not shown) between the metal sheath layer 500. The copper wire direct fabric has a structure in which 2 to 8 strands of copper wire are directly inserted into a nonwoven fabric and performs a function of smoothly and electrically contacting the outer semiconducting layer 400 and the metal sheath layer 500 by the copper wire. To form the outer semiconducting layer 400, the wound semi-conductor cell, metallized paper, etc. may perform a function of tightly binding them so as to maintain the above-described structure without being released. As the metal sheath layer 500 moves during bending, damage to the metallized paper or the like may be prevented.

The metal sheath layer 500 prevents the insulating oil from leaking to the outside of the cable, and fixes the voltage applied to the cable during direct current transmission between the conductor 100 and the metal sheath layer 500 so as to ground at one end of the cable. It acts as a return of fault current in the event of a ground fault or short circuit of the cable to protect safety, protect the cable from shocks, pressures, etc. outside the cable, and improve cable order and flame retardancy.

The metal sheath layer 500 may be formed by, for example, a soft sheath made of pure lead or lead alloy. As the metal sheath layer 500, the soft sheath has a relatively low electric resistance, which serves as a large current collector, and can further improve cable ordering, mechanical strength, and fatigue characteristics when formed as a seamless type. have.

In addition, the soft psi is a surface of the anti-corrosion compound, for example, in order to further improve the corrosion resistance, water resistance of the cable and the adhesion between the metal sheath layer 500 and the cable protection layer 600, Blown asphalt, or the like.

The cable protection layer 600 includes, for example, a metal reinforcement layer 630 and an outer sheath 650, and further includes an inner sheath 610 and

bedding layers

620 and 640 disposed above and below the metal reinforcement layer 630. It can be included as. Here, the inner sheath 610 improves the corrosion resistance, the degree of ordering of the cable, and performs a function of protecting the cable from mechanical trauma, heat, fire, ultraviolet rays, insects or animals. The inner sheath 610 is not particularly limited, but may be made of polyethylene having excellent cold resistance, oil resistance, chemical resistance, and the like, or polyvinyl chloride having excellent chemical resistance, flame resistance, and the like.

The metal reinforcement layer 630 may be formed of a galvanized steel tape, a stainless steel tape, etc. to perform a function of protecting a cable from mechanical shock and to prevent corrosion, and the galvanized steel tape may have an anti-corrosion compound on its surface. Can be applied. In addition, the bedding layers 620 and 640 disposed above and below the metal reinforcing layer 630 may perform a function of alleviating impact, pressure, and the like from the outside, and may be formed by, for example, a nonwoven tape.

In addition, the metal reinforcement layer 630 may be provided directly on the metal sheath layer 500 or through the bedding layers 620 and 640. In this case, the expansion deformation of the metal sheath layer 500 by the high temperature expansion of the insulating oil in the metal reinforcing layer 630 is suppressed to improve the mechanical reliability of the cable and at the same time, the insulating layer 300 and the metal sheath layer 500. The portion of the

semiconducting layers

200 and 400 is intrinsically pressured to improve the dielectric strength.

The outer sheath 650 has substantially the same functions and characteristics as the inner sheath 610, and fires in submarine tunnels, land tunnel sections, etc. are used in the region because they are dangerous factors that greatly affect the safety of personnel or facilities. The outer sheath of the cable is applied to polyvinyl chloride excellent in flame retardant properties, the cable outer sheath of the pipe section can be applied to polyethylene with excellent mechanical strength and cold resistance.

In addition, although not shown here, the metal sheath 500 may be provided with a metal reinforcing layer 630 immediately omitted, and a bedding layer may be provided inside and outside the metal reinforcing layer 630 as necessary. have. That is, the metal sheath layer may be formed to be provided with a bedding layer, a metal reinforcing layer, a bedding layer and an outer sheath sequentially. In this case, since the metal reinforcement layer 630 allows deformation of the metal sheath 500, but suppresses the change in the outer circumference, it is preferable in view of the fatigue characteristics of the metal sheath 500, and the cable insulation layer in the metal sheath 500 during cable energization. Increasing the hydraulic pressure of (300) and, on the contrary, compensates for the lowering of the hydraulic pressure due to shrinkage of the insulating oil due to the temperature drop when the cable is turned off, and the hydraulic pressure is rapidly increased as in the inner semiconducting layer 200 in the high hydraulic pressure portion. It is desirable to have the effect of replenishing the oil by moving the oil to the down portion.

In addition, when the cable is a submarine cable, the cable protection layer 600 may further include, for example, an outer serving layer 670 made of an iron sheath 660 and polypropylene yarn. The outer wire sheath 660, the outer serving layer 670 may perform a function of additionally protecting the cable from the sea current, reefs and the like.

In addition, when the cable is a submarine cable, the cable protection layer 600 may further include, for example, an outer serving layer 670 made of an iron sheath 660, polypropylene yarn, or the like. The outer wire sheath 660, the outer serving layer 670 may perform a function of additionally protecting the cable from the sea current, reefs and the like.

Although the present specification has been described with reference to preferred embodiments of the invention, those skilled in the art may variously modify and change the invention without departing from the spirit and scope of the invention as set forth in the claims set forth below. Could be done. Therefore, it should be seen that all modifications included in the technical scope of the present invention are basically included in the scope of the claims of the present invention.

Claims

Conductor;

An inner semiconducting layer surrounding the conductor;

An insulating layer surrounding the inner semiconducting layer;

An outer semiconducting layer surrounding the insulating layer;

A metal sheath layer surrounding the outer semiconducting layer; And

A cable protective layer surrounding the metal sheath layer;

The inner semiconducting layer is a power cable, characterized in that formed by the transverse winding of a semi-conductive film (semi-conductive film) formed from a polymer composite material in which conductive particles are incorporated in a polymer resin.
The method of claim 1,

The polymer resin is characterized in that the melting point (Tm) is 120 ℃ or more, power cable.
The method of claim 2,

The polymer resin is high density polyethylene (HDPE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyamide (PA), polypropylene (PP), polyvinylidene fluoride (PVDF), fluorine rubber and A power cable, characterized in that it comprises one or more selected from the group consisting of silicone rubber.
The method according to any one of claims 1 to 3,

The conductive particles, characterized in that containing 10 to 50% by weight carbon black based on the total weight of the polymer composite material, power cable.
The method according to any one of claims 1 to 3,

The polymer composite material is characterized in that it comprises 0.05 to 2% by weight antioxidant, 0.05 to 2% by weight thermal stabilizer and 0.05 to 2% by weight metal antioxidant based on the total weight of the polymer composite material.
The method according to any one of claims 1 to 3,

The inner semiconducting layer includes a plurality of layers formed by the transverse winding of the semiconducting film,

Wherein the plurality of layers comprises one or more layers formed by the voids of the semiconducting film.
The method of claim 6,

The remaining cable other than the layer formed by the void of the semiconducting film among the plurality of layers includes a layer formed by the gap winding of the semiconducting film.
The method of claim 6,

And at least one layer formed by the void of the semiconducting film includes a layer disposed directly above the conductor.
The method of claim 6,

At least one layer formed by the void of the semiconducting film has an overlap ratio of 20 to 60%, the overlapping ratio of the width of the semiconducting film forming the power cable.
The method of claim 6,

The plurality of layers of the semiconducting film is 2 to 25, the total thickness of the inner semiconducting layer is 0.1 to 3.0 mm, the paper width of the semiconducting film, characterized in that 10 to 30 mm, the power cable.
The method according to any one of claims 1 to 3,

The insulating layer includes a plurality of layers formed by the transverse winding of the insulating paper,

And the plurality of layers comprises a layer formed by a gap winding of insulating paper.
The method according to any one of claims 1 to 3,

The insulating layer is formed by the transverse winding of the insulating paper,

The insulating paper includes kraft paper or semi-synthetic paper impregnated with insulating oil,

The semi-synthetic paper comprises a plastic film and kraft paper laminated on at least one side of the plastic film.
The method of claim 12,

The insulating layer is an inner insulating layer, an intermediate insulating layer and an outer insulating layer are sequentially stacked,

And the inner insulation layer and the outer insulation layer are each formed of kraft paper impregnated with insulating oil, and the intermediate insulation layer is formed of semi-synthetic paper impregnated with insulating oil.
The method of claim 12,

And the insulating oil comprises a high viscosity insulating oil.
The method of claim 14,

The high viscosity insulating oil is a power cable, characterized in that the kinematic viscosity of 60 ℃ more than 500 centistokes (cSt).
The method according to any one of claims 1 to 3,

Wherein said cable protection layer comprises an inner sheath, a bedding layer, a metal reinforcement layer and an outer sheath.
The method of claim 16,

The cable protective layer is characterized in that it further comprises a wire sheath and an outer serving layer, power cable.