KR20150117528A

KR20150117528A - Joint for DC cable

Info

Publication number: KR20150117528A
Application number: KR1020140043117A
Authority: KR
Inventors: 채병하
Original assignee: 엘에스전선 주식회사
Priority date: 2014-04-10
Filing date: 2014-04-10
Publication date: 2015-10-20

Abstract

A connection box of a DC cable according to the present invention comprises a first electrode electrically connected to a conductor of a pair of cables connected to each other, a second electrode electrically connected to the second pair, An electrode, an electric field control layer for selectively conducting the conductor and the external semiconductive layer to each other, and an external insulating layer surrounding the first electrode, the second electrode, and the electric field control layer.

Description

DC connection cable {Joint for DC cable}

The present invention relates to a junction box for a DC cable, and more particularly, to a junction box of a DC cable, which prevents a local electric field concentration of a junction box in connecting the ends of the DC cable to each other or connecting the DC cable and the processing line, The present invention relates to a connection box having a linear temperature profile and adjusting the amount of heat generated in the connection box to a predetermined value or less.

Generally, a power cable is a device that transmits electric power using an internal conductor, and can be classified into a DC (direct current) power cable and an AC (alternating current) power cable.

At this time, an intermediate connection box (PMJ: PreMolded Join) for connecting the ends of the DC power cable to each other or an end connection box for connecting the DC power cable and the processing line can be used.

Conventional intermediate junction boxes have insulating members made of EPDM (Ethylene Prophylene Diene Monomer), or have a similar structure to an AC junction box, or are made of EMJ (Extruded Molded Joint) or TMJ (Taping Molded Joint).

However, in order to apply the EPDM to an intermediate connection box, a very precise design is required according to the type and standard of a cable, and an intermediate connection box such as an EMJ or TMJ requires a very long time for connection to a site, Which is accompanied by problems such as the invasion of foreign substances and the like.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a connection box that can be used for a DC power cable to solve the above-mentioned problems, and which can easily perform a connection process in a short time at the time of field connection.

It is an object of the present invention to provide a method of manufacturing a semiconductor device, which comprises a first electrode electrically connected to a conductor of a pair of cables connected to each other, a second electrode electrically connected to the first electrode, And an external insulating layer provided to surround the first electrode, the second electrode, and the electric field control layer.

At least a part of the electric field control layer may be provided between an interface of the insulating layer of the cable and an interface of the external insulating layer. Also, the electric field control layer may have a volume resistance of 10 ⁸ to 10 ^12? M. Furthermore, the electric field control layer may have a relative dielectric constant of 15 or more.

Meanwhile, the electric field control layer may control at least one of the thickness, the length, and the inner diameter of the electric field control layer to limit the amount of heat generated in the electric field control layer. For example, the thickness of the electric field control layer satisfies the following equation,

Where, P _max is the inner diameter, the W of the amount of heat (W / m), wherein E is the voltage across the cable, wherein D is the outer diameter or the electric field of the insulating layer of the cable control layer generated by the field control layer, the The thickness of the electric field control layer, and p denotes the resistivity of the electric field control layer.

At this time, the electric field control layer may have a volume resistance of 10 ⁸ to 10 ^12? M, and further, the electric field control layer may have a relative dielectric constant of 15 or more.

According to the connection structure of the power cable for DC of the present invention having the above-described structure, the PMJ type connection can be performed in a short time by a simple process even in the field connection.

Furthermore, according to the present invention, it is possible to maintain the insulation performance of the connection box by limiting the amount of heat generated when designing the electric field control layer to a predetermined value or less.

In addition, according to the present invention, the temperature profile generated in the connection box can be linearly maintained to prevent the temperature rise locally in a part of the connection box, thereby assuring the insulation performance.

1 is a perspective view showing an internal configuration of a power cable for DC having an insulation layer composed of XLPE,
FIG. 2 is a perspective view showing an internal configuration of a DC submarine cable having an insulation layer composed of XLPE, FIG.
3 is a perspective view showing an internal configuration of a DC power cable having insulating paper impregnated with insulating oil,
Fig. 4 is a perspective view showing an internal configuration of a DC submarine cable having insulating paper impregnated with insulating oil, Fig.
5 is a cross-sectional view showing the structure of a connection box according to an embodiment of the present invention,
FIG. 6 is a perspective view showing the electric field control layer in FIG. 5,
7 is a graph showing the temperature profile from the center to the outside of the cable,
8 is a graph showing the electric field distribution in a junction box according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals designate like elements throughout the specification.

1 is a perspective view showing the internal construction of a DC power cable 100 having an insulation layer composed of XLPE.

Referring to FIG. 1, the power cable 100 has a conductor 10 along its center. The conductor 10 serves as a passage through which electric current flows, and may be composed of, for example, copper or aluminum. The conductor (10) is constituted by twining a plurality of element wires (11).

However, the surface of the conductor 10 is not smooth, so that the electric field may be uneven and corona discharge tends to occur partially. In addition, when a gap is formed between the surface of the conductor 10 and the insulating layer 14 described later, the insulating performance may be deteriorated. In order to solve such a problem, the outer surface of the conductor 10 is covered with a semiconductive material such as semiconductive carbon paper, and the layer formed by the semiconductive material is defined as the inner semiconductive layer 12.

The inner semiconductive layer 12 uniformizes the charge distribution on the conductive surface to make the electric field uniform, thereby improving the dielectric strength of the insulating layer 14 described later. Furthermore, the formation of a gap between the conductor 10 and the insulating layer 14 is prevented to prevent corona discharge and ionization. The inner semiconductive layer 12 also prevents penetration of the insulating layer 14 into the conductor 10 when the power cable 100 is manufactured.

An insulating layer 14 is provided on the outside of the inner semiconductive layer 12. The insulating layer 14 electrically insulates the conductor 10 from the outside. In general, the insulating layer 14 should have a high breakdown voltage, and the insulating performance must be stable for a long period of time. Furthermore, it should have low dielectric loss and resistance to heat such as heat resistance. Therefore, polyolefin resin such as polyethylene and polypropylene is used for the insulating layer 14, and a polyethylene resin is preferable. The polyethylene resin may be a crosslinked resin, and may be produced by a silane or an organic peroxide such as, for example, dicumylperoxide (DCP) as a crosslinking agent.

However, when the direct current high voltage is applied to the power cable, the insulation layer 14 injects charges from the conductor 10 into the inner semiconductive layer 12, the insulation layer 14, etc., A space charge can be formed. When the impulse voltage is applied to the cable or the polarity of the DC voltage applied to the cable is abruptly reversed, the space charge is accumulated in the insulating layer 13 according to the use time of the cable, And the electric field strength is rapidly increased to lower the dielectric breakdown voltage of the power cable.

The insulating layer 14 may include inorganic particles in addition to the crosslinked resin. The inorganic particles may be nano-sized aluminum silicate, calcium silicate, calcium carbonate, magnesium oxide, or the like. However, from the viewpoint of the impulse strength of the insulating layer, magnesium oxide is preferable as the inorganic particles. The magnesium oxide can be obtained from magnesium natural ore, but can also be prepared from artificial synthetic materials using magnesium salt in seawater, and it is also possible to supply the material with high purity and stable quality and physical properties.

Although the magnesium oxide has a crystal structure of a face-centered cubic structure, it may have various shapes, purity, crystallinity, physical properties and the like depending on the synthesis method. Specifically, the magnesium oxide is divided into a cubic shape, a terrace shape, a rod shape, a porous shape, and a spherical shape. The magnesium oxide may be variously used depending on its specific physical properties. Such inorganic particles including magnesium oxide exhibit an effect of suppressing the movement of charges and the accumulation of space charges by forming a potential well at the boundary between the base resin and the inorganic particles when an electric field is applied to the cable.

However, the inorganic particles added to the insulating layer 14 act as impurities when added in a large amount and have a problem of lowering the impulse strength, which is another important characteristic required in a power cable even when used in small amounts, Since the accumulated space charge can not be sufficiently reduced by the inorganic particles alone, it is preferable to add 0.2 to 5 parts by weight.

On the other hand, if not only the inside but also the outside of the insulating layer 14 is not shielded, a part of the electric field is absorbed by the insulating layer 14, but most of the electric field is discharged to the outside. In this case, if the electric field becomes larger than a predetermined value, the insulating layer 14 and the outer surface of the power cable 100 may be damaged by an electric field. Therefore, a semiconductive layer is provided on the outer side of the insulating layer 14 and is defined as an outer semiconductive layer 16 to distinguish it from the inner semiconductive layer 12 described above. As a result, the outer semiconductive layer 16 is grounded, and the distribution of the electric lines of force between the outer semiconductive layer 16 and the inner semiconductive layer 12 is made equal to improve the dielectric strength of the insulating layer 14. Further, the outer semiconductive layer 16 can smooth the surface of the insulating layer 14 in the cable, thereby alleviating the electric field concentration, and preventing the corona discharge.

A shielding layer 18 made of a metal sheath or a neutral wire is provided outside the outer semiconductive layer 16 in accordance with the type of the cable. The shielding layer 18 is provided for electrical shielding and return of short-circuit current.

A jacket (20) is provided on the outer side of the power cable (100). The sheath 20 is provided on the outer side of the cable 100 to protect the internal structure of the cable 100. Therefore, the outer cover 20 is excellent in chemical resistance and mechanical strength to withstand chemicals such as weatherability, chemical substances, and the like that can withstand various environments such as light, weather, moisture, air and various climatic conditions. Generally, it is made of PVC (Polyvinyl Chloride) or PE (Polyethylene).

2 shows an internal configuration of a submarine cable for DC according to another embodiment. The power cable according to Fig. 2 shows the construction of a power cable which can be used, for example, with a so-called submarine cable connecting the land via the sea. The differences from the embodiment of FIG. 1 described above will be mainly described.

Referring to FIG. 2, the conductor 10, the inner semiconductive layer 12, the insulating layer 14, and the outer semiconductive layer 16 are similar to those of the embodiment of FIG. 1 described above, and thus a repetitive description thereof will be omitted.

In order to prevent the insulating layer 14 from being deteriorated when foreign substances such as water penetrate into the outside of the outer semiconductive layer 16, a metal sheath made of lead, a so- (30).

Furthermore, a sheath 32 made of a resin such as polyethylene or the like is provided outside the metal sheath 30 and a bedding layer 34 so as not to be in direct contact with water. A wire sheath 40 may be provided on the bedding layer 34. The wire sheath 40 is provided on the outer side of the cable 200 to enhance mechanical strength to protect the cable from the external environment of the seabed.

A jacket 42 is provided on the outer periphery of the wire sheath 40, that is, on the outer periphery of the cable 200 as an outer sheath of the cable. The jacket 42 is provided on the outer side of the cable 200 to protect the internal structure of the cable 200. In particular, in the case of a submarine cable, the jacket 42 has excellent weather resistance and mechanical strength that can withstand undersea environments such as seawater. For example, the jacket 42 may be made of polypropylene yarn or the like.

3 shows an internal configuration of a power cable for DC according to another embodiment. The power cable according to Fig. 3 differs from the power cable in the above-described embodiment in the configuration of the inner conductor and the insulating layer. Hereinafter, the differences will be mainly discussed.

3 is a partially cutaway perspective view showing the internal construction of a so-called 'ground insulation power cable' including an insulation layer having insulating paper impregnated in insulating oil.

Referring to FIG. 3, the power cable 200 has a conductor 210 along a center portion thereof. The conductor 210 serves as a passage through which the current flows. The conductor 210 may include a circular central strand 210A and a rectangular strand 210C composed of a square strand 210B stranded to surround the central strand 210A as shown in the figure. The square wire strand 210C is formed by forming a plurality of square wire strands 210B in a rectangular shape through a continuous extrusion process and twisting the plurality of square wire strands 210B on the center strand 210A. The conductor 210 is formed to have a circular shape as a whole. As shown in FIG. 3, the conductor 210 may include a plurality of circular wires. However, the conductor made of the square wire element has a relatively higher spot rate than the conductor made of the circular wire element, and can be adapted to a high-voltage power cable.

The inner semiconductive layer 212 formed on the surface of the conductor 210 and the outer semiconductive layer 16 formed on the surface of the insulating layer 214 to be described later are similar to the description of FIG. It is omitted.

An insulating layer 214 is provided on the outer side of the inner semiconductive layer 212. The insulating layer 214 electrically insulates the conductor 210 from the outside. In FIG. 3, the insulating layer 214 is formed through an insulation process in which an insulating paper is wound around the surface of the inner semiconductive layer 212. Further, in order to improve the insulation characteristic, the insulator is impregnated in the insulating oil while the insulator is wound on the surface of the conductor 210. The insulating oil is absorbed by the insulating paper through the impregnation process and can be divided into 'OF (oil filled) cable' and 'MI (mass impregnated) cable' depending on the viscosity of the insulating oil.

The OF cable is impregnated with insulating paper using a relatively low-viscosity insulating oil. Since the oil must be pressurized to keep the hydraulic pressure at a certain level, the extension length is limited. On the other hand, the MI cable impregnates insulating paper using a relatively high-viscosity insulating oil, so there is a merit that the length of the extension is long since there is no need to maintain the hydraulic pressure because the flow of the insulating oil is small in the insulating paper.

In the present embodiment, the insulating layer 214 is formed by wrapping a plurality of insulating paper, and may be formed by repeatedly wrapping a thermoplastic resin such as kraft paper or kraft paper and polypropylene resin .

Specifically, an insulating layer may be formed by winding only a kraft paper, but it is preferable to form an insulating layer by winding an insulating paper having a structure in which a kraft paper is laminated on the upper and lower surfaces of a composite insulating paper such as a polypropylene resin can do.

In the case of a MI cable in which a craft is wound and impregnated with an insulating oil, the MI cable is radially inward due to the current flowing in the cable conductor during operation of the cable (during energization), that is, radially outward in the insulating layer portion in the direction of the inner semiconductive layer, That is, a temperature difference occurs in a portion of the insulating layer in the outer semiconductive layer direction described later. Therefore, the viscosity of the insulating oil in the portion of the insulating layer at the higher temperature, that is, the upper half of the inner semiconductive layer is lowered and thermally expanded to move to the insulating layer at the outer semiconductive layer side. So that air bubbles are generated in the radially inward portion, that is, in the insulating layer portion on the inner semiconductive layer side, resulting in lowering of the insulation performance.

However, in the case of forming the insulating layer with the composite insulating paper as described above, the thermoplastic resin such as polypropylene resin which is not impregnated with the oil during the operation of the cable thermally expands, so that the flow of the insulating oil can be suppressed. Since the insulation resistance is larger than that of the craft paper, even if bubbles are generated, the voltage shared by the bubbles can be mitigated.

In addition, since the polypropylene resin is not impregnated with the insulating oil, it is possible to suppress the flow of the insulating oil in the cable diameter direction due to gravity. In addition, depending on the impregnation temperature during cable production or the operating temperature during cable operation, The thermal expansion causes the surface pressure to be applied to the kraft paper, so that the flow of the insulating oil can be further suppressed.

The composite insulating paper may be prepared by laminating kraft paper on one side of a thermoplastic resin such as polypropylene resin, thermoplastic resin such as polypropylene resin on the upper and lower surfaces of kraft paper, or thermoplastic resin such as kraft paper and polypropylene resin alternately in four layers Or the like can be used. In this case, the action and effect are the same as those of the insulating paper having a structure in which a craft paper is laminated on the upper and lower surfaces of the above-mentioned polypropylene resin.

The insulating layer 214 may be formed of a kraft paper by winding the composite insulating paper and both or both of the surface contacting the inner semiconductive layer 212 and the surface contacting the outer semiconductive layer 216 , Preferably both the surface in contact with the inner semiconductive layer 212 and the surface in contact with the outer semiconductive layer 216 can be formed by winding with a kraft paper.

In this case, since the kraft paper having a resistivity lower than that of the composite insulating paper is formed on one surface or both surfaces of the insulating layer contacting the inner semiconductive layer 212 or the surface contacting the outer semiconductive layer 216, Even if air bubbles are generated in a portion where the inner semiconductive layer is in contact or in a portion where the insulating layer and the outer semiconductive layer are in contact with each other, it is possible to prevent impulse breakdown characteristics from deteriorating due to the electric field relaxation effect of the kraft ground layer. In addition, since the craft paper has little polarity effect on impulse breakage, it can reduce the impulse polarity effect caused by using plastic laminate paper.

The outer semiconductive layer 216 is provided outside the insulating layer 214 and has been described above with reference to FIG. 1, so that a repetitive description thereof will be omitted.

The insulating oil or the insulating compound impregnated into the insulating layer has a deteriorated insulation performance when foreign substances such as water are intruded into the insulating semiconductive layer 216. In addition, A metal sheath made of lead is formed on the outside of the copper wire directing tape 218 to prevent it.

Furthermore, a bed layer 222 is provided on the outer surface of the metal sheath 220 so as not to be in direct contact with water. A nonwoven fabric tape 224 and a reinforcing tape 226 are wrapped on the beding layer 222 and a jacket 232 is provided on the outer side of the cable 200 as a jacket of the cable. The jacket 232 is provided at the outer periphery of the MI cable 200 to protect the internal structure of the cable 200. The jacket 232 may be made of, for example, polyethylene (PE) or the like so as to have excellent weather resistance and mechanical strength that can withstand various environments.

4 is a partially cutaway perspective view showing the internal construction of the ground-insulated power cable 200 according to another embodiment. The ground-insulated power cable according to Fig. 4 shows the construction of a power cable which can be used, for example, as a so-called submarine cable connecting the land via the sea. The difference from the embodiment of FIG. 3 described above will be mainly described.

Referring to FIG. 4, a ground-insulated power cable 200 used as a submarine cable includes a wire enclosure 230 surrounding a wire for increasing the mechanical strength to report a cable from the external environment of the submarine, . 3, the reinforcing tape 226 may be provided on the outer periphery of the reinforcing tape 226 or may be formed by winding a nonwoven fabric tape (not shown) on the outer periphery of the reinforcing tape 226, An enclosure 230 may be provided.

A jacket 232 is provided as an outer surface of the cable at the outer periphery of the wire sheath 230, that is, the outer periphery of the cable 200. The jacket 232 is provided on the outer periphery of the ground-insulated power cable 200 to protect the internal structure of the cable 200. In particular, in the case of a submarine cable, the jacket 232 has excellent weather resistance and mechanical strength that can withstand undersea environments such as seawater. For example, the jacket 232 may be formed of polypropylene yarn or the like. Hereinafter, a structure of a connection box for connecting a DC cable having the above configuration will be described.

5 is a cross-sectional view illustrating the structure of a connection box 300 according to an embodiment of the present invention.

5, the connection box 300 includes a first electrode 310 electrically connected to the conductors 10 and 210 of a pair of cables connected to each other, An electric field control layer 330 for electrically connecting the conductor and the external semiconductive layer to each other, and a second electrode 320 formed on the first electrode 310, the second electrode 320, And an outer insulating layer 340 surrounding the insulating layer 340.

The first electrode 310 and the second electrode 320 may be formed using, for example, semiconductive liquid silicone rubber (LSR). The first electrode 310 functions to spread the electric field between the first electrode 310 and the second electrode 320 without being concentrated locally.

Specifically, the first electrode 310 is electrically connected to the conductors 10 and 210 of the cable to serve as a so-called high voltage electrode, and the second electrode 320 is electrically connected to the external semiconductive layer 16, and 216 to serve as a so-called shielding electrode (deflector). Therefore, the electric field distribution in the connection box 300 is distributed between the first electrode 310 and the second electrode 320. In this case, the shapes, sizes, and materials of the first electrode 310 and the second electrode 320 are appropriately adjusted so that the electric field distribution between the first electrode 310 and the second electrode 320 is not concentrated can do.

The outer insulating layer 340 provided on the outer side of the connection case 300 may be made of, for example, liquid silicone rubber (LSR). The outer insulating layer 340 may be provided on the outer side of the connection case 300, 300).

The electric field control layer 330 is configured to selectively conduct the conductors 10 and 210 and the outer semiconductive layers 16 and 216 of a pair of DC power cables connected to each other. At least a portion of the electric field control layer 330 is provided between an interface of the insulating layer 10, 210 of the cable and the external insulating layer 340. The electric field control layer 330 may be formed using, for example, liquid or solid silicone rubber.

Referring to the connection box 300 of the DC power cable, space charges can be locally accumulated in the connection box when the cable is driven, that is, when a predetermined DC voltage is applied for a predetermined time or more. Particularly, space charge can be accumulated between the interface of the insulating layer 14, 214 of the cable having different materials and the outer insulating layer 340, that is, between the different interfaces. Such accumulation of space charge can act as a weak point in terms of insulation performance, so it is necessary to discharge the accumulated space charge as described above.

Accordingly, the connection box 300 may include the electric field control layer 330 for discharging the space charge. As described above, the electric field control layer 330 selectively conducts the conductors 10 and 210 of the DC power cable and the outer semiconductive layers 16 and 216 to each other. If necessary, Or more), the space charge is discharged.

As described above, the electric field control layer 330 may be made of liquid or solid silicone rubber and may have a volume resistivity of 10 ⁸ to 10 ¹² Ωm, preferably a volume resistivity of 10 ⁸ to 10 ¹⁰ Ωm. Lt; / RTI > In addition, in the case of having the volume resistivity, the electric field control layer 330 may have a relative dielectric constant of about 15 or more.

The meaning that the electric field control layer 330 selectively conducts the conductors 10 and 210 and the external semiconductive layers 16 and 216 is as follows. The electric field control layer 330 having the above-described physical properties has a relatively high resistance value during normal operation, so that the conductor and the outer semiconductive layer are not electrically connected. On the other hand, when space charges are accumulated between the interfaces of the insulating layers 14 and 214 and the outer insulating layer 340, that is, between different interfaces, space charges larger than a predetermined value are accumulated and discharged do. For example, the electric field control layer 330 may have an electrical characteristic such that the resistance value decreases nonlinearly when a voltage higher than a predetermined value is applied. Therefore, when a space charge is accumulated between the interfaces of the insulating layers 14 and 214 and the outer insulating layer 340, that is, between the two interfaces, the voltage of the electric field control layer 330 becomes non- The space charges are discharged through the outer semiconductive layer 16 and 216 by electrically connecting the conductors 10 and 210 of the DC power cable and the outer semiconductive layers 16 and 216 to each other. Therefore, the electric field control layer 330 may be made of a so-called FGM (Field Grading Material) material. As a result, the electric field control layer 330 functions as a discharge passage through which the accumulated space charge is discharged.

However, when the accumulation and discharge of the space charge are repeated in the electric field control layer 330 as described above, heat due to the movement of the space charge is generated. Particularly, in a DC cable, if heat is generated in the connection box at a predetermined value or more, it affects the electric field distribution. Therefore, it is necessary to limit the generation of heat in the connection box to a predetermined value or less.

6 is a perspective view showing the electric field control layer 330 in FIG.

Referring to FIG. 6, the electric field control layer 330 may have a cylindrical shape provided outside the insulation layers 14 and 214 of the cable, and may be formed using a liquid or solid silicone rubber .

A necessary factor for designing the electric field control layer 330 corresponds to the thickness W, the length L and the inner diameter D of the electric field control layer 330. Therefore, in the present embodiment, at least one of the thickness W, the length L and the inner diameter D of the electric field control layer 330 is suitably adjusted to reduce the amount of heat generated in the electric field control layer 330 to a predetermined value or less .

Here, the inner diameter of the electric field control layer 330 corresponds to the outer diameter of the insulation layers 14 and 214 of the cable, and the length does not significantly affect the design of the electric field control layer 330. Therefore, in this embodiment, the thickness of the electric field control layer 330 is controlled to limit the amount of heat generated in the electric field control layer 330. Equation (1) below shows the relationship between the amount of heat generated in the electric field control layer 330 and other factors.

Where, P _max is the field-control layer heat (W / m) generated in the unit 330, the E is a voltage applied to the cable, wherein D is the outer diameter (or the field-control layer 330 of the insulating layer of the cable , W is a thickness of the electric field control layer 330, and p is a resistivity of the electric field control layer 330. [

(E) of the cable, the outer diameter of the insulation layer of the cable (or the inner diameter of the electric field control layer 330) D, and the resistivity p of the electric field control layer 330, And the electrical properties and physical properties of the control layer. The amount of heat P generated in the electric field control layer 330 may be determined according to the specification of the connection box 300. For example, the amount of heat (heat dissipation property) may be maintained at 1 W / m or less . &Lt; / RTI >

Therefore, all the values except for the thickness W of the electric field control layer 330 in Equation (1) can be determined to be specific values. Therefore, the electric field control layer 330 can be determined by using Equation (1) The thickness can be determined.

FIG. 7 is a graph showing a temperature profile from the center to the outside in a junction box having the above-described electric field control layer. In the graph, the vertical axis represents the temperature (占 폚), and the horizontal axis represents the length toward the outside of the connection box at the center of the cable.

Referring to FIG. 7, a relatively high temperature is shown in the insulating layers 14 and 214 (region A) of the cable, and the electric field control layer 330 (region B) and the external insulating layer 340 The temperature profile decreases linearly. That is, in the case of applying the electric field control layer 330 according to Equation (1), it is possible to prevent the temperature of the specific region from rising locally in the connection box 300 and to maintain the temperature profile linearly. Therefore, it is possible to prevent the occurrence of a weak point in the insulation performance of the connection box 300 and to improve the insulation performance.

8 is a graph showing an electric field distribution in a connection box according to an embodiment of the present invention.

8, the electric field distribution inside the connection case 300 having the above-described configuration is uniformly distributed between the first electrode 310 and the second electrode 320 as shown in FIG. 8, But does not represent a locally focused area.

7 and 8, in the case of the connection box 300 having the electric field control layer 330 according to the present invention, when the space charge is accumulated to a predetermined value or more, And further, it is possible to prevent the local temperature rise and the electric field concentration, thereby improving the insulation performance.

10, 210 ... conductors
12, 212 ... inner semiconductive layer
14, 214 ... insulating layer
16, 216 ... outer semiconductive layer
300 ... connection box
310 ... first electrode
320 ... second electrode
330 ... electric field control layer
340 ... outer insulating layer

Claims

A first electrode electrically connected to a conductor of a pair of cables connected to each other;
A second electrode provided in a pair so as to face each other;
An electric field control layer for selectively conducting the conductor and the outer semiconductive layer to each other; And
And an outer insulating layer covering the first electrode, the second electrode, and the electric field control layer.

The method according to claim 1,
Wherein at least a part of the electric field control layer is provided between an interface of the insulating layer of the cable and an interface of the external insulating layer.

3. The method of claim 2,
Wherein the electric field control layer has a volume resistance of 10 ⁸ to 10 ^12? M.

The method of claim 3,
Wherein the electric field control layer has a relative dielectric constant of 15 or more.

3. The method of claim 2,
Wherein the electric field control layer regulates at least one of a thickness, a length and an inner diameter of the electric field control layer to restrict the amount of heat generated in the electric field control layer.

6. The method of claim 5,
Wherein the thickness of the electric field control layer satisfies the following equation,

Where, P _max is the inner diameter, the W of the amount of heat (W / m), wherein E is the voltage across the cable, wherein D is the outer diameter or the electric field of the insulating layer of the cable control layer generated by the field control layer, the The thickness of the electric field control layer, and the reference symbol p denotes the resistivity of the electric field control layer.

The method according to claim 6,
Wherein the electric field control layer has a volume resistance of 10 ⁸ to 10 ^12? M.

8. The method of claim 7,
Wherein the electric field control layer has a relative dielectric constant of 15 or more.