KR101830032B1 - Jointing power cable system using joint box and joint box for power cable - Google Patents

Abstract

The present invention relates to a DC power cable intermediate connection system capable of mitigating the concentration of an electric field in a portion where insulation is weak in a connection structure of a DC power cable, and to an intermediate connection box for a DC power cable. The intermediate connection box for a DC power cable of the present invention includes a pair of DC power cables and an intermediate connection box for connecting the DC power cables to each other. The DC power cables include: a conductor; an inner semi-conductive layer formed to surround the conductor; a cable insulation layer; an outer semi-conductive layer formed to surround the cable insulation layer; and a metal sheath formed to surround the outer semi-conductive layer. The intermediate connection box for a DC power cable includes a conductor connection portion for electrically connecting conductors of the pair of cables to each other; a first reinforcing insulating layer; a second reinforcing insulating layer; and an electric field shift layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an intermediate connection system for a DC power cable intermediate connection system and a DC power cable,

The present invention relates to an intermediate connection box for a DC power cable and a power cable connection system using the same.

Generally, a power cable is used to power a desired location through the ground, ground, or seabed using a power-supplying conductor.

The power cables are connected by a joint box at intervals of several hundred meters or tens of kilometers, and the ends of the power cables are connected to the wires by a termination connection box. In the case of connecting the power cable in the intermediate connection box or the termination connection box, the conductor is first connected in a state in which the insulation layer of the cable is exposed, and the reinforcing insulation layer is formed on the surface of the insulation layer by inserting the insulation paper impregnated in the high viscosity insulation oil . In this case, the insulating paper is supported while applying the insulating oil in the course of winding the insulating paper, that is, between the insulating paper, and then the outer semiconductive layer, the metallic sheath and / or the conventional layer are restored.

The first reinforcing insulating layer may be formed up to the outer diameter of the cable insulating layer and the second reinforcing insulating layer may be formed at an outer diameter or more of the cable to reinforce the insulating performance.

In this case, a slope portion is formed on both sides of the second reinforcing insulating layer to control an electric field continuously applied in the insulating layer, and a connection box outer semiconductive layer formed by restoring the outer semiconductive layer of the cable on the slope portion is sloped The equipotential lines continuing from the insulating layer are dispersed by the volume resistance difference between the semiconductive layer outside the connection box and the second reinforcing insulating layer and the geometrical shape of the semiconductive layer outside the connection box, The electric field can be controlled.

However, there is a problem that the equipotential lines are densely distributed in the slope portion having a relatively thin insulating layer thickness, in particular, at the portion where the slope portion is started, and are densely packed to act as an insulation weak portion.

An object of the present invention is to provide a DC power cable intermediate connection system and an intermediate connection box for a DC power cable, which can relieve the concentration of an electric field in a portion where insulation is weak in a connection structure of a DC power cable.

An intermediate connection case for a power cable according to an embodiment of the present invention includes a conductor, an inner semiconductive layer, a cable insulation layer, and an outer semiconductive layer, and the inner semiconductive layer, the cable insulation layer, and the outer semiconductive layer are sequentially peeled off A conductor crimping sleeve for electrically connecting the conductors of the pair of cables to each other; A first reinforcing insulating layer formed on the conductor compression sleeve to the outer diameter of the cable insulating layer; a linear portion formed on the first reinforcing insulating layer and parallel to the longitudinal direction of the cable; A reinforcing insulating layer comprising a second reinforcing insulating layer including a slope portion whose width in the longitudinal direction in the radial direction of the reinforcing insulating layer is narrowed; And a field shift layer positioned between the slope portion and the cable insulation layer; .

In the present invention, the electric field shift layer may extend not only between the slope portion and the cable insulation layer but also between the straight line portion and the cable insulation layer.

In the present invention, the electric field shift layer may have a lower volume resistivity than the second reinforcing insulating layer or the cable insulating layer.

In the present invention, when the cable insulation layer or the second reinforcing insulation layer in contact with the electric field shift layer is made of PPLP, the electric field shift layer may have a volume resistance that is 10 ² times lower than the volume resistance of the PPLP.

In the present invention, the electric field shift layer may be formed of kraft paper.

In the present invention, the electric field shift layer may be formed on the cable insulation layer or may be an outermost portion of the cable insulation layer as a part of the cable insulation layer.

In the present invention, the electric field shift layer may be formed to have a thickness of 5 to 15% of the thickness of the cable insulation layer.

In the present invention, it is possible to further include an outer semi-conductor layer wound on the outer surface of the slope portion.

A power cable connection structure according to an embodiment of the present invention is a power cable connection structure including a pair of DC power cables and an intermediate connection box for electrically connecting the pair of DC power cables to each other, And a cable core portion including a conductor, an inner semiconductive layer surrounding the conductor, a cable insulation layer surrounding the inner semiconductive layer, and an outer semiconductive layer surrounding the cable insulation layer, A conductor crimping sleeve for electrically connecting conductors to each other; A first reinforcing insulating layer formed on the conductor compression sleeve to the outer diameter of the cable insulating layer; a linear portion formed on the first reinforcing insulating layer and parallel to the longitudinal direction of the cable; A reinforcing insulating layer comprising a second reinforcing insulating layer including a slope portion whose width in the longitudinal direction in the radial direction of the reinforcing insulating layer is narrowed; And a field shift layer positioned between the slope portion and the cable insulation layer; .

In the present invention, the electric field shift layer may extend not only between the slope portion and the cable insulation layer but also between the straight line portion and the cable insulation layer.

In the present invention, the electric field shift layer may have a lower volume resistivity than the second reinforcing insulating layer or the cable insulating layer.

In the present invention, when the cable insulation layer or the second reinforcing insulation layer in contact with the electric field shift layer is made of PPLP, the electric field shift layer may have a volume resistance that is 10 ² times lower than the volume resistance of the PPLP.

In the present invention, the electric field shift layer may be formed of kraft paper.

In the present invention, the electric field shift layer may be formed on the cable insulation layer or may be an outermost portion of the cable insulation layer as a part of the cable insulation layer.

In the present invention, the electric field shift layer may be formed to have a thickness of 5 to 15% of the thickness of the cable insulation layer.

In the present invention, it is possible to further include an outer semi-conductor layer wound on the outer surface of the slope portion.

According to an embodiment of the present invention, the equipotential lines can be densely distributed in the slope portion of the intermediate connection box having a relatively thin insulating layer thickness, thereby preventing the weak connection portion from acting as an insulating weak portion and dispersing the electric field.

1 is a perspective view showing an internal configuration of a power cable.
2 is a partial cutaway view schematically showing a cable connected by an intermediate connection box;
FIG. 3 is an enlarged view of FIG. 2C.
4 is a cross-sectional view showing a conductor crimping sleeve before crimping.
Fig. 5 is a cross-sectional view showing a conductor compression sleeve after compression. Fig.
6 is a cross-sectional view showing the first reinforcing insulating layer and the second reinforcing insulating layer of the intermediate connection box shown in FIG. 2 in more detail.
Figs. 7-11 are cross-sectional views of various embodiments illustrating the crimp sleeve after crimping.

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.

Generally, the insulating oil impregnated cable is connected by an intermediate connection box at intervals of several hundred meters or several kilometers, and the end of the insulating oil impregnated cable is connected to the working line by the termination connection port. Hereinafter, the construction of the dielectric-oil-impregnated power cable will be described first, and the connection process of the connection box will be described.

1 is a partially cutaway perspective view showing an internal configuration of an ultra high voltage direct current power cable.

1, a power cable 100 includes a conductor 11, an inner semiconductive layer 12, a cable insulation layer 14, and an outer semiconductive layer 16, And the cable core portion 10 for preventing electric current from leaking in the cable radial direction.

The conductor 11 serves as a passage through which a current flows to transmit electric power and is made of a material having excellent conductivity and strength and flexibility suitable for cable manufacturing and use such as copper or aluminum ≪ / RTI >

1, the conductor 11 is provided with a circular central wire element 11a and a flat wire element layer 11C composed of a rectangular wire element 11b stranded to surround the circular central wire element 11a May be a rectangular conductor having an entirely circular cross section, and as another example, it may be a circular compression conductor in which a plurality of circular element wires are twisted and compressed in a circular shape. The rectangular conductor has an advantage that the outer diameter of the cable can be reduced because the dot rate is relatively higher than that of the circular compressed conductor.

Since the conductor 11 is formed by twisting a plurality of elemental wires, the surface of the conductor 11 may not be smooth and the electric field may be uneven, and corona discharge is likely to occur partially. In addition, when a gap is formed between the surface of the conductor 11 and the cable insulation layer 14 described later, the insulation performance may be deteriorated.

In order to solve the above-mentioned problems, an inner semiconductive layer 12 may be formed outside the conductor 11. The inner semiconductive layer 12 may have semiconducting properties by adding conductive particles such as carbon black, carbon nanotube, carbon nanoplate, or graphite to the insulating material.

The inner semiconductive layer 12 functions to stabilize the insulation performance by preventing a sudden change in the electric field between the conductor 11 and the cable insulation layer 14 described later. In addition, by suppressing the uneven distribution of electric charge on the conductor surface, it is possible to make the electric field uniform and prevent the gap between the conductor 11 and the cable insulation layer 14 from being formed, thereby suppressing the corona discharge and dielectric breakdown do.

The cable insulation layer 14 is provided on the outer side of the inner semiconductive layer 12 to electrically isolate the cable insulation layer 14 from the outside so that a current flowing along the conductor 11 does not leak to the outside.

The cable insulation layer 14 may be formed of insulating paper impregnated with insulating oil. That is, the cable insulation layer 14 may be formed by winding up insulation paper in multiple layers so as to surround the inner semiconductive layer 12 and impregnating the insulation oil after the cable core is formed. As the insulating oil is absorbed by the insulating paper, the insulating property of the cable insulating layer 14 can be improved.

The insulating oil is filled in gaps between the voids inside the insulating paper and the gap formed between the layers formed by winding the insulating paper to improve the insulating property and reduce the frictional force between the insulating paper at the time of bending the cable to improve the bending property of the cable. Although the kind of the insulating oil is not particularly limited, it should be in contact with copper or aluminum constituting the conductor 11 and not be oxidized by heat. It is preferable that the insulating paper be impregnated at an impregnation temperature, for example, It is preferable to use a medium-viscosity insulating oil having a sufficiently low viscosity and a kinematic viscosity at 60 DEG C of 10 to 500 centistokes or a high-viscosity insulating oil having a kinematic viscosity at 60 DEG C of 500 centistokes or more.

In the case of using a low-viscosity insulating oil having a relatively low viscosity, it is necessary to pressurize the insulating oil using a lubricating device or the like in order to keep the insulating paper impregnated with the insulating oil and prevent the gap from being generated in the cable insulating layer due to the flow of the insulating oil There is a need. However, when medium viscosity or high viscosity insulating oil is used, the flow of insulating oil is small, so there is no need for an oil supply device for pressurizing the insulating oil, or the number of required oil supply facilities can be reduced, thereby extending the cable extension length. For example, the insulating oil may be at least one insulating oil selected from the group consisting of naphthenic insulating oil, polystyrene insulating oil, mineral oil, alkylbenzene, polybutene-based synthetic oil, heavy alkaline,

The insulating paper may be a kraft paper in which kraft pulp is used as a raw material and an organic electrolyte in the pulp is removed, or a composite insulating paper in which a kraft paper is adhered to one side or both sides of a plastic film. The plastic film has a resistivity higher than that of the kraft paper adhered to one side or both sides thereof, so that even if bubbles are generated in the kraft paper due to the flow of the insulating oil during the impregnation process or cable operation, the voltage distributed to the bubbles can be relaxed, A polyolefin resin such as polypropylene or polybutylene, a tetrafluoroethylene-hexafluoropropylene copolymer, an ethylene-tetrafluoroethylene copolymer, an ethylene-tetrafluoroethylene copolymer, And a polypropylene homopolymer resin which is excellent in heat resistance.

Specifically, the cable insulation layer 14 can be formed by winding up a kraft and impregnating the insulation oil. In this case, the insulating oil may flow in the direction of the cable load, and the gap may be generated. On the other hand, when the composite insulating paper is wound and impregnated with the insulating oil to form the cable insulating layer 14, the thermoplastic resin such as the polypropylene resin is not impregnated with the insulating oil, and the impregnation temperature at the time of cable production, Thermal expansion is caused by operating temperature. When the thermoplastic resin thermally expands, a surface pressure is applied to the laminated kraft paper, thereby narrowing the passage of the insulating oil. Therefore, the flow of the insulating oil due to the gravity or the shrinkage / expansion of the insulating oil according to the temperature can be suppressed. In addition, the composite insulating paper has an advantage of being able to reduce the outer diameter of the cable because the dielectric insulating strength is higher than that of the craft paper.

On the other hand, when the power cable is energized, heat is generated in the conductor serving as a passage through which the current flows, and the temperature gradually decreases from the inside toward the outside in the cable radial direction, Occurs. Therefore, the insulation oil of the cable insulation layer, that is, the cable insulation layer formed on the inner semiconductive layer 12, which belongs to the conductor directly above the section, moves to the outside due to low viscosity and thermal expansion, The viscosity of the insulating oil is increased and it does not return to the original state, so that voids may be generated in the portion of the cable insulation layer in the region directly above the conductor.

In addition, a high electric field acts on the cable insulation layer, that is, the cable insulation layer formed in the direction of the outer semiconductive layer 16, which belongs to the section under the metal sheath where the electric field gradually increases due to the temperature difference. The conductor straight section and the metal sheath lower section have a high possibility of occurrence of voids and can act as an insulation weak portion which is a starting point of partial discharge and dielectric breakdown as a region where a high electric field acts in accordance with a temperature change in the cable.

In order to solve the above-described problems, only a kraft may be used as an insulating paper in the area of the cable insulation layer 14 including the insulation weak portion. That is, the cable insulation layer 14 is divided into the first cable insulation layer, the second cable insulation layer, and the third cable insulation layer in the direction of the outer semiconductive layer 16 described later from the inner semiconductive layer 12, Only the kraft may be used for the cable insulation layer and / or the third cable insulation layer, and the composite insulation paper may be used for the second cable insulation layer.

In this case, a difference in resistivity occurs between the second cable insulating layer on which the composite insulating paper is wound and the first cable insulating layer and / or the third cable insulating layer on which the kraft paper is wound, and the cable insulation layer The first cable insulation layer and / or the third cable insulation layer of the second insulation layer 14 has a relatively low resistivity and functions to alleviate an electric field shared among the insulation fragile portions. Specifically, a high electric field acts on the second cable insulating layer on which the composite insulating paper having a high resistivity is wound due to the resistive electric field distribution characteristic of the DC cable in which the electric field is distributed according to the resistivity, and the first cable insulating layer and / A relatively low electric field acts on the conductor straight section and / or the metal sheath lower section included in the insulation layer, so that the electric field acting on the insulation weak portion is relaxed and the insulation performance can be stabilized.

In addition, the cable insulation layer 14 may form the third cable insulation layer to be thicker than the first cable insulation layer. In the case of forming a metallic sheath 22 described later on the outside of the cable insulation layer 14 or restoring the metallic sheath 22 after connecting two power cables exposed sequentially from the inside of the cable core portion The second cable insulation layer may be formed to have a larger thickness than the first cable insulation layer so that the second cable insulation layer 14 may be deformed, It is preferable to protect the plastic film from heat. In this case, the thickness of the first cable insulation layer can be selected in consideration of the impulse surge voltage required for the power cable and the like.

The outer semiconductive layer 16 may be provided outside the cable insulation layer 14. The outer semiconductive layer 16 is formed of a material having semiconducting properties by adding conductive particles such as carbon black, carbon nanotube, carbon nanoplate, graphite and the like to an insulating material such as an inner semiconductive layer, Uneven charge distribution between the layer 14 and the metal sheath 22 described later is suppressed to stabilize the insulation performance. In addition, the outer semiconductive layer 16 functions to smooth the surface of the cable insulation layer 14 in the cable so as to prevent corona discharge by alleviating electric field concentration, and to physically protect the cable insulation layer 14 Can be performed. The outer semiconductive layer 16 may further include a metalized paper. The metalized sheet may be formed by laminating an aluminum foil on a kraft paper, and a plurality of perforations may be present to facilitate impregnation of the cable insulating layer 14 with insulating oil.

The cable core portion 10 may further include a water absorbing portion 21 for preventing water from penetrating into the cable. The moisture absorbing portion can be formed between the stranded strands of the conductor 11 and / or the outside of the conductor 11. The water absorbing portion can absorb the moisture penetrated into the cable at a high speed, Tape, a coating layer or a film including a super absorbent polymer (SAP) so as to prevent moisture from penetrating in the longitudinal direction of the cable. In addition, the water absorbing part may have a semiconductive property to prevent a sudden change in the electric field.

A cable protecting portion 20 is provided outside the cable core portion 10 and a power cable installed in the seabed may further include a cable covering portion 30. The cable protector and cable protector protects the core from various environmental factors such as moisture penetration, mechanical trauma, and corrosion which may affect the power transmission performance of the cable.

The cable protection portion 20 includes a metal sheath 22 and a polymer sheath 24 to protect the cable from an accident current, an external force or other external environmental factors.

The metallic sheath 22 may be formed so as to surround the core portion 10. In particular, when the power cable is installed in an environment such as a seabed, the cable core portion 10 may be sealed to prevent foreign matter such as moisture from entering the cable core portion 10, The melted metal is extruded outside the cable core portion 10 so as to have a continuous outer surface having no seams, so that the order performance can be improved. Lead or aluminum is used as the above metal. In the case of a power cable installed on the seabed, it is preferable to use lead having excellent corrosion resistance against seawater. To compensate for mechanical properties, It is more preferable to use a lead alloy. The metal sheath 22 serves as a passage through which a fault current flows when a ground fault or a short circuit occurs in the ground at a power cable end, protects the cable from external impacts, and prevents an electric field from being discharged to the outside of the cable .

The metal sheath 22 may be coated with a corrosion inhibiting compound such as a blown asphalt or the like in order to further improve the corrosion resistance, water repellency and the like of the cable and improve the adhesive strength with the polymer sheath 24 .

In addition, a copper wire-directing tape or a moisture absorbing layer 21 may be additionally provided between the metal sheath 22 and the cable core portion 10. The copper wire direct tape is composed of a copper wire and a nonwoven tape and acts to smooth electrical contact between the outer semiconductive layer 16 and the metal sheath 22. The moisture absorbing layer absorbs moisture penetrating the cable A tape, a coating layer or a film including a super absorbent polymer (SAP) excellent in the ability to maintain the absorbent state at a high speed and to prevent moisture from penetrating in the cable longitudinal direction It plays a role. The copper wire-directing tape and the water-absorbing layer preferably have a semiconducting property in order to prevent a sudden change in the electric field, and may include a copper wire in the water-absorbing layer so as to be capable of both conducting and absorbing water.

The polymer sheath 24 is formed outside the metal sheath 22 to improve the corrosion resistance and water repellency of the cable and to protect the cable from mechanical damage and other external environmental factors such as heat and ultraviolet rays . The polymer sheath 24 may be formed of a resin such as polyvinyl chloride (PVC), polyethylene or the like. In the case of a power cable installed in the seabed, it is preferable to use a polyethylene resin having excellent water repellency. In the environment, polyvinyl chloride resin is preferably used.

The power cable 100 includes a metal reinforcing layer 26 made of a steel cap or the like galvanized on the inner side or the outer side of the polymer sheath so that the metal sheath 22 expands due to expansion of the insulating oil . The upper and / or lower portions of the metal reinforcing layer 26 may be provided with a bedding layer (not shown) made of a semiconductive nonwoven tape or the like to buffer an external force applied to the power cable, and may be made of polyvinyl chloride or polyethylene It is possible to further improve the corrosion resistance, water resistance and the like of the power cable, and further protect the cable from other external environmental factors such as mechanical trauma and heat and ultraviolet rays.

In addition, the power cable installed on the seabed may be easily damaged by an anchor or the like of a ship, and may be damaged by a bending force due to currents or waves, a frictional force with the sea floor, etc. Therefore, (30) may be additionally provided.

The cable sheathing may include an armor layer 34 and a covering layer 38. The armor layer 34 may be composed of at least one layer made of steel, zinc-plated steel, copper, brass, bronze, etc., And performance as well as additional protection from external forces.

Polypropylene yarn or the like is formed in one or more layers on the upper and / or lower portions of the armor layer 34 to protect the cable, and the serving layer 34 formed at the outermost portion is formed of a color Can be made of two or more different materials to ensure the visibility of the cable installed at the seabed.

2 is a partial cutaway view schematically showing a cable connected by an intermediate connection box; 1 is a partial cut-away view schematically showing a state in which DC power cables 100A and 100B having the configuration shown in Fig. 1 are connected to each other by an intermediate connection box 200. Fig. FIG. 3 is an enlarged view of FIG. 2C.

Referring to FIGS. 2 and 3, first, a pair of DC power cables 100A and 100B are connected to the DC power cables 100A and 100B in a state in which the cable insulating layers 14A and 14B and the conductors 11A and 11B are exposed. The conductor connecting portions can be formed by electrically connecting the respective ends of the conductors 11A and 11B. The conductor connection portion serves as a current path through the electrically conductive conductors 11A and 11B, through which the power can be transmitted. The conductor connecting portions are formed by pressing and welding the conductors 11A and 11B with the conductor crimping sleeve 1P and electrically connecting the conductors 11A and 11B to each other.

The cable insulation layer 14A may be composed of the first cable insulation layer 14A1, the second cable insulation layer 14A2, and the third cable insulation layer 14A3 as described above. The cable insulation layer 14A can be pen-sled to have a multi-stage structure. As an example, as shown in FIGS. 2 and 6, the cable insulation layer 14A may be configured to have a multi-stage structure of a first pen sling end 14a1, a second pen sling end 14a2, and a third pen sling end 14a3. Can be pen sling. The first pen sling end 14a1 is made up of a part of the inner semiconductive layer 12, the first cable insulating layer 14A1 and the second cable insulating layer 14A2, And the third pen sling end 14a3 may be formed of a part of the second cable insulating layer 14A2 and the third cable insulating layer 14A3. This will be described later together with the reinforcing insulating layer.

A counterflow leakage preventing portion PC for preventing the copper powder generated from the conductors 11A and 11B from flowing out may be positioned between the conductor crimping sleeve 1P and the conductors 11A and 11B.

When a pair of cables, for example, a DC power cable, is connected by an intermediate junction, the conductor in the cable is heated as the current flows through the cable, so that the viscosity of the dielectric oil in the cable decreases, . ≪ / RTI > The copper moving in the gravity direction flows out to the reinforcing insulating layer, and there is a problem that insulation breakdown occurs in the copper powder flowing out to the reinforcing insulating layer.

According to one embodiment of the present invention, the counterpart leakage preventing portion PC is provided between the conductor crimping sleeve 1P and the conductors 11A and 11B and / or between the innermost layer 2101A of the first reinforcing insulating layer 2101 It is possible to prevent the copper generated from the conductors 11A and 11B from flowing out to the reinforcing insulating layer 210 by being disposed between the conductors 11A and 11B.

The counterflow leakage preventing portion PC includes a first electric field smoothing layer 12 located on the conductor 11A exposed between the first pen sling end 14a1 of the cable 100A and the conductor crimping sleeve 1P And a copper flow-out prevention plate 211 disposed between the conductor compression sleeve 1P and the conductor 11A.

The first electric field uniforming layer 12 may be disposed between the conductor compression sleeve and the conductor, and between the reinforcing insulation layer and the conductor. That is, the first electric field smoothing layer 12 can extend not only between the first cable insulation layer 14A1 and the conductor compression sleeve 1P, but also extends between the conductor compression sleeve 1P and the conductor 11A.

The first electric field uniforming layer 12 may be formed, for example, by extending the inner semiconductive layer of the cable 100A. That is, the first electric field uniforming layer 12 is removed as the inner semi-conductive layer itself of the cable 100A together with the first cable insulating layer 14A1 without being removed and leaving a predetermined length, The conductor 11A is exposed.

The first electric field smoothing layer 12 may be formed by inserting at least one insulating paper on the conductor 11A, but the first two sheets of paper may be formed in a gap region after the first two sheets are formed.

Specifically, the first electric field uniforming layer 12 has a plurality of semi-conductive layers (not shown) so as to overlap the innermost layer adjacent to the conductors 11A and 11B of the DC power cables 100A and 100B in the longitudinal direction of the cable, The tape may be formed by transversely winding the semi-conductive tape, which is a kind of insulating paper, in the longitudinal direction of the DC power cables 100A and 100B.

As another example, the first electric field uniforming layer 12 may be formed on the conductors 11A and 11B of the direct current power cables 100A and 100B with the innermost layer adjacent to the conductors of the direct current power cables 100A and 100B. A plurality of carbon paper, which is a semiconductive tape, is laid across the length of the cable in the longitudinal direction of the DC power cables 100A and 100B, (Carbon paper), which is a kind of insulating paper, is horizontally spaced apart in the longitudinal direction of the DC power cables 100A and 100B.

Since the first electric field uniforming layer 12 is formed in a gap region after the air gap, the air gap of a plurality of insulating paper sheets (carbon paper) is minimized, and thus the flow of the same amount can be primarily prevented. Further, since a plurality of sheets of insulating paper (carbon paper) are allowed to pass through the gap, and the gap is inspected, the bending characteristics can be improved.

The first electric field smoothing layer 12 can be removed from the first cable insulating layer 14A1 to expose the inner semiconductive layer of the exposed cable 100A and extend between the conductor crimping sleeve 1P and the conductor 11A . That is, one end of the first electric field smoothing layer 12 may be positioned between the conductor compression sleeve 1P and the conductor 11A.

The first electric field uniforming layer 12 is formed at a position where the corrugated acid (1 Pa 'in FIG. 5) on the inner side of the conductor crimp sleeve 1P formed by the pressing of the conductor crimp sleeve 1P, And may extend to one end of the sleeve 1P. As another example, as shown in FIG. 5, the first electric field uniforming layer 12 may extend to the immediately before the highest ridge T in the corrugated acid (1 Pa 'in FIG. 5). By extending in this way, a sufficient current path can be ensured between the conductor 11A of the cable and the conductor crimping sleeve 1Pa. As another example, as shown in FIG. 6, the first electric field uniforming layer 12 may extend beyond the highest ridge T in the corrugated acid (1 Pa 'in FIG. 5). This will be described later.

The foul spill preventing plate 211 can be disposed between the conductor crimping sleeve 1P and the conductor 11A. That is, the counterflow leakage preventing plate 211 is disposed so as to correspond to the inside of the conductor crimping sleeve 1P and may not exceed the conductor crimping sleeve 1P. As another example, as shown in Figs. 9 and 10, the spill preventing plate 211 " can extend beyond both ends of the conductor crimping sleeve 1P as well as between the conductor crimping sleeve 1P and the conductor 11A .

The copper leakage preventing plate 211 may be formed of a metal material having a structure that is dense enough to prevent the copper from permeating, and may preferably be formed of a metal material capable of withstanding a force acting upon pressing of the pressing sleeve. The copper leakage preventing plate 211 may be made of copper, aluminum, a copper alloy, or an aluminum alloy so as to correspond to the material of the conductors 11A and 11B of the cables 100A and 100B.

The copper leakage preventing plate 211 may be formed by wrapping a part of the first electric field uniforming layer 12 and the conductor 11A with a copper tape and attaching or brazing an end portion of the copper tape which is in contact with each other. When both ends of the copper tape are soldered to form the copper portion leakage prevention plate 211, it is preferable that the connection portion of the solder is smoothly processed so that no edge is generated.

The outflow route of the copper foil generated in the conductor 11A formed so as to enclose the cable conductor 11A by the tangs between the conductor crimping sleeve 1P and the conductor 11A is minimized So that the fingers can be blocked by the fingertip leakage preventing plate 211.

One end of the copper spill preventing plate 211 which faces the end of the cable conductor 11A is pressed against the crimp trough 1Pb 'beyond the crimp mountain 1Pa' formed on the inner side by pressing the conductor crimping sleeve 1P It can be pressed against the conductor crimp sleeve 1P by extending from the adjacent position a1 to the first cable insulating layer 14A1. For example, as shown in FIG. 5, the flow dividing plate 211 preferably extends beyond the ridge T, which is the highest point in the ridge 1Pa '.

The other end a2 of the copper flow-out prevention plate 211 that faces the first cable insulation layer 14A1 of the cable may protrude from the conductor compression sleeve 1P and may not act as an edge.

Referring to FIGS. 4 and 5, the arrangement of the first field equalization layer 12 and the counterflow leakage prevention plate 211 will be described below.

4 and 5 are cross-sectional views showing a state in which a pair of conductors 11A and 11B are electrically connected to each other by a conductor crimping sleeve. 4 is a cross-sectional view showing a conductor crimping sleeve before crimping, and Fig. 5 is a cross-sectional view showing a crimp sleeve after crimping.

4, when the pair of conductors 11A and 11B are electrically connected, the respective ends of the pair of conductors 11A and 11B are fitted in the conductor accommodating portion of the conductor compression sleeve 1P , The outer surface of the conductor crimping sleeve is pressed by the crimping device to grip the pair of conductors to firmly support the connection state as shown in FIG. 5, and after the crimping, the outer surface of the conductor crimping sleeve is uniformly polished, .

5, the conductor compression sleeve 1P includes at least two protrusions 1Pa protruding from the outer surface, at least one recess 1Pb formed between the protrusions 1Pa, As shown in FIG. 5, the area where the protrusion 1Pa is formed is pressed by the compression device and protruded to the inside of the conductor compression sleeve 1P to form a corrugated acid 1Pa ' And the outer surface of the conductor crimping sleeve 1P, which is uneven due to the pressing, can be flattened to prevent the electric field concentration on the outer surface of the conductor crimping sleeve, the corona discharge, and the like.

The first electric field uniforming layer 12 extends in the direction toward the conductor compression sleeve 1P from the inner semiconductive layer of the cable 100A as described above and one end of the first electric field uniformizing layer 12 is sandwiched between the conductor compression sleeve 1P and the conductor 11A The other end portion of the cable 100A facing the first cable insulating layer 14A1 does not protrude from the conductor crimping sleeve 1P and one end portion of the cable 100A facing the end portion of the conductor 11A As shown in FIG.

As shown in Fig. 5, by pressing the conductor crimping sleeve 1P, a corrugated acid 1Pa 'is formed on the inner surface of the conductor crimp sleeve 1P, and the first electric field uniforming layer 12 is formed of the corrugated acid 5A and 5B) extends to a point just before the highest ridge T in FIG. 5 and extends to a point beyond the ridge T which is the highest point in the ridge 1Pa ' .

Figs. 7 to 11 are views showing various modifications of the first electric field homogenizing layer and the coarse leakage preventing plate.

7, the first electric field smoothing layer 121 extends from the inner semiconductive layer of the cable 100A in the direction toward the conductor compression sleeve 1P, and one end of the first electric field uniformization layer 121 contacts the conductor crimping sleeve 1P and the conductor 11A. And the other end portion of the cable 100A which faces the first cable insulating layer 14A1 is not protruded from the conductor crimping sleeve 1P and is disposed between the end portions of the conductors 11A The portion can be extended to a predetermined length.

As shown in Fig. 7, by pressing the conductor crimping sleeve 1P, a corrugate acid 1Pa 'is formed on the inner surface of the conductor crimp sleeve 1P, and the first field uniforming layer 121 is formed of the corrugated acid 1Pa '), and the equipotential leakage preventing plate 211 can extend beyond the ridge T, which is the highest point in the ridge 1Pa'.

8, the first electric field smoothing layer 122 extends from the inner semiconductive layer of the cable 100A in the direction toward the conductor compression sleeve 1P, and one end thereof is connected to the conductor compression sleeve 1P and the conductor 11A. And the copper flow-out prevention plate 211 'may be disposed over the entire surface between the conductor compression sleeve 1P and the conductor 11A. 5 and 6, a single flow leakage preventing plate 211 is disposed between the conductor 11A and the conductor crimping sleeve 1P and another one between the conductor 11B and the conductor crimping sleeve 1P In the embodiment shown in FIG. 8, one flow dividing prevention plate 211 'is disposed between the conductor crimping sleeve 1P and the conductors 11A and 11B. The end portion of the cable flow-out prevention plate 211 'facing the first cable insulation layer 14a1 of the cable 100A and the end portion of the cable 100A facing the first cable insulation layer 14A1 are electrically connected Can be disposed between the conductor crimping sleeve 1P and the conductors 11A and 11B without protruding from the sleeve 1P.

As shown in Fig. 8, the conductor pressing sleeve 1P is pressed to form a corrugated acid 1Pa 'on the inner surface of the conductor crimp sleeve 1P, and the first field uniforming layer 122 is formed of the corrugated acid 1 Pa ') beyond the highest ridge (T).

9, the first electric field leveling layer 123 extends in the direction from the inner semiconductive layer of the cable 100A toward the conductor compression sleeve 1P, and one end thereof is connected to the conductor compression sleeve 1P and the conductor 11A. And the copper flow-out prevention plate 211 'may be disposed over the entire surface between the conductor compression sleeve 1P and the conductor 11A. 5 and 7, one flow-out preventing plate 211 is disposed between the conductor 11A and the conductor crimping sleeve 1P and another one between the conductor 11B and the conductor crimping sleeve 1P In the embodiment shown in FIG. 9, one flow dividing prevention plate 211 'is disposed between the conductor crimping sleeve 1P and the conductors 11A and 11B. The end portion of the cable flow-out prevention plate 211 'facing the first cable insulation layer 14a1 of the cable 100A and the end portion of the cable 100A facing the first cable insulation layer 14A1 are electrically connected Can be disposed between the conductor crimping sleeve 1P and the conductors 11A and 11B without protruding from the sleeve 1P.

As shown in Fig. 9, by pressing the conductor crimping sleeve 1P, a corrugate acid 1Pa 'is formed on the inner surface of the conductor crimp sleeve 1P, and the first field uniforming layer 123 is formed by the corrugated acid 1Pa ') without extending beyond the highest ridge (T).

10, the first electric field smoothing layer 124 extends from the inner semiconductive layer of the cable 100A in the direction toward the conductor compression sleeve 1P, and one end of the first electric field smoothing layer 124 contacts the conductor crimping sleeve 1P and the conductor 11A. The other end portion of the cable 100A which faces the first cable insulating layer 14A1 protrudes from the conductor crimping sleeve 1P and extends from the end portion of the conductor 11A A part of the flow blocking plate 211 "may be disposed between the conductor crimping sleeve 1P and the conductors 11A, 11B while the other portion may be a conductor crimping sleeve (not shown) 1P and extend toward the cable insulation layer 14A.

As shown in Fig. 10, by pressing the conductor crimping sleeve 1P, a corrugate acid 1Pa 'is formed on the inner surface of the conductor crimp sleeve 1P, and the first field uniforming layer 124 is formed by the corrugated acid 1Pa '), and the equipotential leakage preventing plate 211 can extend beyond the ridge T, which is the highest point in the ridge 1Pa'. The other part of the flow blocking preventing plate 211 " and the first electric field equalizing layer 124 may overlap with each other in a region beyond the conductor crimping sleeve 1P.

11, the first electric field smoothing layer 125 extends from the inner semiconductive layer of the cable 100A in the direction toward the conductor compression sleeve 1P, and one end of the first electric field smoothing layer 125 contacts the conductor crimp sleeve 1P and the conductor 11A. The other end portion of the cable 100A which faces the first cable insulating layer 14A1 protrudes from the conductor crimping sleeve 1P and extends from the end portion of the conductor 11A A part of the flow blocking plate 211 "may be disposed between the conductor crimping sleeve 1P and the conductors 11A, 11B while the other portion may be a conductor crimping sleeve (not shown) 1P and extend toward the cable insulation layer 14A.

As shown in Fig. 11, by pressing the conductor crimping sleeve 1P, a corrugate acid 1Pa 'is formed on the inner surface of the conductor crimp sleeve 1P, and the first field uniforming layer 124 is formed of the corrugated acid 1 Pa '), and the peaks leakage preventing plate 211 can extend beyond the ridge T, which is the highest point of the pebble mountain 1Pa'. In addition, the first electric field equalizing layer 125 and the other part of the first flow blocking plate 211 " may overlap with each other in the region beyond the conductor crimping sleeve 1P.

Referring to FIG. 3, the counterflow leakage preventing portion PC includes a first electric field equalization layer 12, a first flow blocking layer 211 surrounding the first electric field uniforming layer 12, a second electric field smoothing layer 211 surrounding the conductor compression sleeve 1P, And a pressing layer 213 wound on the second electric field uniforming layer 212. The first and second electric field uniforming layers 212,

The second electric field smoothing layer 212 is formed by wrapping the carbon creep paper so as to surround the first electric field uniforming layer 12, the flow blocking plate 211 and the conductor compression sleeve 1P, It is possible to additionally prevent the copper from flowing out by strongly adhering the layer 12, the copper leakage preventing plate 211, and the conductor compression sleeve 1P. In other words, it is difficult to maintain a high degree of smoothness while pressing the surface of the conductor crimping sleeve 1P. The second electric field smoothing layer 212 can uniform the electric field on the outer circumferential surface of the conductor crimp sleeve 1P by covering the outer circumferential surface of the finished conductor crimp sleeve 1P and making the surface even.

In addition, the second electric field uniforming layer 212 can press the first electric field uniforming layer 212 and the coarse leakage preventing plate 211.

The second electric field smoothing layer 212 may, for example, bond the carbon creep paper in a wraparound manner. That is, the second electric field uniforming layer 212 can be formed by directing the carbon creep paper to overlap in the longitudinal direction of the cable.

The second electric field smoothing layer 212 may be made of carbon paper as another example. It is preferable that the second electric field homogenizing layer 212 is made of corrugated carbon paper considering the step at both ends of the conductor crimp sleeve 1P.

Since the second electric field uniforming layer 212 is semi-conductive, it is possible to prevent a sudden electric field change between the conductor crimping sleeve 1P and the reinforcing insulating layer 210 from occurring.

A pressing layer 213 may be wound on the second field uniforming layer 212. The pressing layer 213 is formed to closely contact the first electric field uniforming layer 12, the flow blocking plate 211, the conductor pressing sleeve 1P and the second electric field uniforming layer 212 to each other to prevent .

The pressing layer 213 is preferably deposited on the second field uniforming layer 212 in a gap in consideration of bending characteristics. That is, the pressing layer 213 can be formed by horizontally stacking the kraft paper in the longitudinal direction of the cable as an example.

The pressing layer 213 can be wound with an insulating paper in order to alleviate the electric field on the conductor crimping sleeve 1P in which a high electric field is applied when the cable is energized.

The pressing layer 213 may have a volume resistance lower than that of the reinforcing insulating layer 2110 by 10 ² or more.

6 is a cross-sectional view showing the first reinforcing insulating layer and the second reinforcing insulating layer of the intermediate connection box shown in FIG. 2 in more detail.

6, the respective conductors of the DC power cables 100A and 100B are crimped and connected to the conductor crimping sleeve 1P to form the copper leakage preventing portion PC and then the conductors 11A and 11B The reinforcing insulating layer 210 covering at least a part of the cable insulating layers 14A1, 14A2, and 14A3 including the connection portions of the cable insulating layers 14A1, 14A2, and 14A3.

The reinforcing insulating layer 210 may include a first reinforcing insulating layer 2101 and a second reinforcing insulating layer 2102. The first reinforcing insulating layer 2101 is formed up to the outer diameter of the third insulating layer 14A3 of the cable 100A and the innermost layer 2101A, the first intermediate layer 2101B, and the second intermediate layer 2101B of the reinforcing insulating layer 210 2101C). The second reinforcing insulating layer 2102 may be formed on the first reinforcing insulating layer 2101. That is, the second reinforcing insulating layer 2102 may be laminated in the radial direction of the first reinforcing insulating layer 2101. The second reinforcing insulating layer 2102 may be the outermost layer 2101D of the reinforcing insulating layer 210.

2 and 6, the first reinforcing insulating layer 2101 may be formed by restoring to the outer diameter of the cable insulating layer 14A on the conductor compression sleeve 1P. The first reinforcing insulating layer 2101 has slopes at both ends so as to have a shape corresponding to the ends of the pen slings ends 14a1, 14a2 and 14a3 of the cable insulation layer 14A exposed to have a slope shape By winding an insulating paper.

The first reinforcing insulating layer 2101 has an inclined surface at both ends and is in contact with each of the pen slings 14a1, 14a2 and 14a3 of the cable insulating layer 14A. The first reinforcing insulating layer 2101 has both end portions of the first reinforcing insulating layer 2101 A sufficient interface length can be secured compared with the case where each of the pen slings 14a1, 14a2 and 14a3 of the cable insulation layer 14A contacts vertically without a slope. As the interface length between the first reinforcing insulating layer 2101 and the cable insulating layer 14A increases, the surface electric field characteristics between the first reinforcing insulating layer 2101 and the cable insulating layer 14A can be improved.

Therefore, as shown in FIGS. 2 and 6, the interfacial length between the first reinforcing insulating layer 2101 and the cable insulating layer 14A is increased by pen-slitting the cable insulating layer 14A in multiple steps and forming an inclined surface at the end portion thereof . Furthermore, by reducing the angle of the inclined surfaces of the respective ends of the cable insulating layer 14A, the interface length between the first reinforcing insulating layer 2101 and the cable insulating layer 14A can be further increased. The increase of the interfacial length can further improve the surface electric field characteristics between the first reinforcing insulating layer 2101 and the cable insulating layer 14A.

It is not possible to configure the length of the intermediate connection box on the customer's demand, specification, or manufacturing cost for a long time without limitation. As described above, according to the present invention, it is possible to reduce the angle of the inclined surface where the first reinforcing insulating layer 2101 and the cable insulating layer 14A contact with each other within a predetermined intermediate connecting box length without increasing the length of the intermediate connecting box, By increasing the interface length between the layer 2101 and the cable insulating layer 14A, it is possible to maintain a constant surface electric field level without increasing the overall length of the intermediate connection box. Thus, the length of the intermediate connection box can be kept shorter while maintaining a constant level of ground surface electric field, thereby reducing the manufacturing cost of the intermediate connection box.

The second reinforcing insulating layer 2102 may be made of a composite insulating paper having excellent dielectric strength as compared with insulating paper. As an example, the second reinforcing insulating layer 2102 may be made of PPLP, which is a type of composite insulating paper. In this case, the electric field concentrated on the insulating layer 14 and the first reinforcing insulating layer 2101 of the cable 100 having a relatively high temperature during the operation of the cable 100 is referred to as the second reinforcing insulating layer 211, So that the insulation performance of the intermediate connection box 200 can be enhanced.

The second reinforcing insulating layer 2102 which is the outermost layer 210D of the reinforcing insulating layer 210 may be composed of a straight portion 210A and a slope portion 210B.

The straight portion 210A is formed on the first reinforcing insulating layer 2101 formed to the outer diameter of the cable insulating layer 14A on the conductor crimping sleeve 1P and is configured to be parallel to the longitudinal direction of the cable 100A . The slope portion 210B may be formed so that the width of the slope portion 210B in the longitudinal direction of the cable 100A is narrower at both ends of the straight portion 210A.

The connection box outer semiconductive layer 230 formed by restoring the outer semiconductive layer 16 of the cable 14A is formed along the outer surface of the slope portion 210B of the second reinforcing insulating layer 2102, May be formed to cover the linear portion 210A of the insulating layer 2102. [ The connection semiconductors outer semiconductive layer 230 formed on the outer surface of the slope portion 210B has a slope shape as a whole and the equipotential lines extending from the cable insulation layer 14A to the intermediate connection box 200 are formed in a slope shape Can be distributed according to the geometric shape of the connection semiconductors external semiconductive layer (230). That is, it is possible to control the electric field distribution according to the slope shape of the connection semiconductive layer 230.

The first reinforcing insulating layer 2101 and the second reinforcing insulating layer 2102 may be formed of a plurality of insulating ground layers 212L as shown in FIG. The insulating paper layer 212L is formed by winding insulating paper in a radial direction of the intermediate connection box 210, and each insulating paper layer 212L is not continuous with the wrapping insulating paper. That is, the insulating paper constituting the insulating layer 212L of the same layer is formed of continuous insulating paper, but the insulating paper layer 212L of the other layer is not continuous with the insulating paper. In other words, the insulation layer 212L refers to a radial layer of the intermediate connection box 200 that is not continuous in its longitudinal direction with insulating paper having a certain width and length.

The first reinforcing insulating layer 2101 and the second reinforcing insulating layer 2102 are insulated by using an insulating paper roll wound with insulating paper having a predetermined length. When all of the insulating paper having the predetermined length is wound, Is repeated to form a plurality of insulating ground layers 212L. Since the reinforcing insulating layer 210 can be formed using insulating paper having different widths / lengths for each insulating layer 212L, the size of the first reinforcing insulating layer 2101 and the size of the second reinforcing insulating layer 2102 And can be configured in various forms. Particularly, the slope portion 210B at both ends of the second reinforcing insulating layer 2102 can be formed such that the inclination of the slope portion 210B gradually increases toward the ends of the cable conductors 11A and 11B. That is, since insulating paper having different widths and lengths is used for each insulating layer 212L, the slope of the slope portion 210B can be precisely controlled.

Each layer of the plurality of insulating ground layers 212L may be composed of a wide width winding portion W and a triple winding portion N as shown in FIG. 6, for example. The insulating paper forming the insulating ground layer 212L can be divided into wide and narrow widths depending on its width. Wide Width means the insulating paper whose width is larger than three Width. The wide width winding portion W is formed by winding a wide width portion, and the triple winding portion N is formed by winding a small width portion.

One insulating layer 212L may be composed of a plurality of wide area winding sections W and at least one triple winding section N. [ That is, a plurality of wafers W are formed by winding the wafers W. The wafers W are wound in a narrow space between the wafers W to form the wafers W.

In particular, when the second reinforcing insulating layer 2102 is formed, the slope surface of the slope portion 210B can be formed by forming the wide width winding portion W. [ Another optical fiber winding portion adjacent to the optical fiber winding portion W may be formed. That is, in each of the slope portions 210B formed at both ends of the second reinforcing insulating layer 2102, a wide width portion is wound to form a wide width winding portion W, and another wide width portion adjacent to the wide width winding portion W And the optical fiber winding portion W can be formed. After the wide width winding section W is formed, a space that can not be wound by the wide width can be formed between the wide width winding sections W, and a narrow width winding section N is formed . The entire shape of the second reinforcing insulating layer 2102 can be precisely controlled by forming the triangular winding portion N between the wide-width winding portions W.

However, the triple winding section N is formed by winding an insulating paper having a relatively small width in comparison with the wide width in the longitudinal direction and the radial direction of the intermediate connection, There is a lot of gaps between the insulation paper and it is dense. The gap may be an insulation weak portion which is likely to act as a gap. Therefore, it is preferable that the triple winding take-up portion N is formed only on the straight portion 210A, not on the slope portion 210B.

It is preferable that each insulation layer of the slope portion 210B is formed by one wide-width winding portion W. That is, the slope portion 210B is not provided with the buttress portion C where the optical fiber winding portion W and the optical fiber winding portion W in contact therewith meet. The optical fiber winding portion W forming the slope portion 210B extends to the straight portion 210A of the second reinforcing insulating layer 2102. [

The second reinforcing insulating layer 2102 includes a plurality of insulating ground layers 212L stacked in the radial direction as described above, and a plurality of (e.g., two or more) insulating layers 2102 surrounding the electric field shifting layer 220 in the radial direction Each of the insulating ground layers of the light guide plate may be formed as a light guide winding portion.

A field shift layer 220 may be disposed between the slope section 210B and the cable insulation layer 14A and as another example the field shift layer 220 may be disposed between the slope section 210B And the cable insulation layer 14A as well as between the rectilinear section 210A and the cable insulation layer 14A.

The electric field shift layer 220 may have a lower volume resistance than the second reinforcing insulating layer 2102 or the cable insulating layer 14A. For example, when the cable insulation layer 14A or the second reinforcing insulation layer 2102 in contact with the electric field shift layer 220 is formed of PPLP, the electric field shift layer 220 may have a volume resistance of 10 ^And the electric field shift layer 220 may be formed of kraft paper.

The intermediate junction box 210 is formed with slope portions 210B on both sides of the second reinforcing insulating layer 2102 to control an electric field applied continuously in the cable insulating layer 14A as described above, The outer half-conduction layer 230 and the second reinforcing insulating layer 212 are formed to have the shape of a slope, so that the connection box outer semiconductive layer 230, which is formed by restoring the outer semiconductive layer 16 of the cable, The electric field in the intermediate connection box 200 can be controlled by dispersing the continuous equipotential lines from the cable insulation layer 14A by the difference in volume resistance with the connection box and the geometric shape of the semiconductive layer 230 outside the connection box.

However, there is a problem that the equipotential lines are densely distributed and densely formed at the portion where the insulating layer thickness is relatively thin, particularly at the portion where the slope portion 210B starts, as a weak insulating portion.

The intermediate junction box 200 according to an embodiment of the present invention includes the electric field shift layer 220 having a low volume resistance between the cable insulation layer 14A and the slope portion 210B of the second reinforcing insulation layer 2102 The electric field at the slope portion 210B of the second reinforcing insulating layer 2102 which is the insulative weakening portion can be dispersed to the straight portion 210A of the second reinforcing insulating layer 2102. [

The electric field shift layer 220 may be formed on the cable insulation layer 14A or may be the outermost portion of the cable insulation layer 14A as a part of the cable insulation layer 14A. The third cable insulation layer 14A3 can function as the electric field shift layer 220 when the third cable insulation layer 14A3 that is the outermost edge of the cable insulation layer 14A is made of kraft paper. In other words, in order to prevent a high electric field from being applied directly under the metal sheath 22 of the cable, the electric field shift layer (not shown) formed of the kraft paper on the third cable insulating layer 14A3 located at the outermost portion of the cable insulating layer 14A The third cable insulation layer 14A3 of the cable insulation layer 14A is extended and connected to the electric field shift layer 220 Lt; / RTI >

The electric field shift layer 220 may have a thickness of 5 to 15% of the thickness of the cable insulation layer 14A. That is, the electric field shift layer 220 is formed to 5 to 15% of the thickness of the cable insulation layer 14A and extends to the straight portion 210A beyond the slope portion 210B (at least the portion where the straight portion 210A starts) The electric field of the slope portion 210B can be shared by the straight portion 210A.

The reinforcing insulating layer 210 may be formed of insulating paper and / or composite insulating paper. The innermost layer 210A of the reinforcing insulating layer 210 may be formed of insulating paper. The outermost layer 210D may be a composite insulating paper Lt; / RTI >

Hereinafter, the present invention will be described in detail. 2, between the conductor crimping sleeve 1P and the first cable insulating layer 14A1 located at the innermost side of the cable insulating layer 14A of the cable 100A, Can remain. The remaining space between the compression sleeve (1P) and the first end (14a1) located on the innermost side of the cable insulation layer (14A) can be covered with insulating paper. The insulating paper may be a kraft paper.

In this case, the outer surface of the innermost layer 210A made of insulating paper of the reinforcing insulating layer 210 is located at substantially the same distance from the outer surface of the first end 14a1 and the central axis in the longitudinal direction of the cable .

The outer surface of the compression sleeve 1P may be surrounded by a semi-conductive tape so as to make the electric field distribution uniform. At this time, when the outer surface of the semi-conductive tape is located at a distance from the longitudinal center axis of the cable from the outer surface of the first end (14a1) located on the innermost side of the insulating layer (14A) of the cable, 210 may be formed so that the outer surface of the innermost layer 210A of the first and second electrodes 210, 210 is located at substantially the same distance from the longitudinal center axis of the cable.

If the outer surface of the first end 14a1 located at the innermost one of the innermost layer 210A made of insulating paper of the reinforcing insulating layer 210 and the multi-end structure of the cable insulating layer 14A is located at the center If a step is generated because it is not located at substantially the same distance from the axis, the portion where the step is generated acts as an electric field weak point, and the electric field may be concentrated and cause dielectric breakdown.

The outermost layer 210D of the reinforcing insulating layer 210 is formed at an outer diameter of the exposed cable insulation layer 14A of the cable 100. [ Since the exposed conductor 11A of the cable is connected by the compression sleeve 1P, not only the height of the conductor section is increased by the thickness of the compression sleeve 1P but also a relatively large amount of heat is generated in the conduction of the cable. Since the reinforcing insulating layer 210 is formed by winding a plurality of insulating sheets or composite insulating sheets and is relatively vulnerable to insulation, the outermost layer 210D of the reinforcing insulating layer 210 is formed to have an outer diameter of the cable insulating layer 14A It is necessary to reinforce the insulation performance.

The outermost layer 210D of the reinforcing insulating layer 210 is composed of a composite insulating paper having excellent dielectric strength as compared with insulating paper. In this case, at the time of operating the cable 100, the insulating layer 14 of the cable 100 having a relatively high temperature and the regions 210A to 210C located inside the outermost layer 210D of the reinforcing insulating layer 210 May be dispersed in the outermost layer 210D of the reinforcing insulating layer 210. [

Intermediate layers 210B and 210C may be provided between the innermost layer 210A and the outermost layer 210D of the reinforcing insulating layer 210. [ The intermediate layer of the reinforcing insulating layer 210 may include a first intermediate layer 210B and a second intermediate layer 210C sequentially from the inner side to the outer side between the innermost layer 210A and the outermost layer 210D .

The innermost layer 210A of the reinforcing insulating layer 210 is made of insulating paper and the first intermediate layer 210B, the second intermediate layer 210C, and the outermost layer 210D of the reinforcing insulating layer 210, Can be made of composite insulating paper.

That is, when the innermost layer 210A of the reinforcing insulating layer 210 is composed of an insulating layer and the first and second intermediate layers 210B and 210C are composed of composite insulating paper, the electric field is distributed according to the resistivity According to the resistive electric field distribution characteristic of the DC power cable, the first intermediate layer 210B and the second intermediate layer 210C, which are formed of composite insulating paper having a relatively higher resistivity than the kraft paper as the insulating paper of the innermost layer 210A, It is widely distributed. Accordingly, since a relatively high temperature is generated in the operation of the cable, contraction / expansion of the insulating oil is relatively actively generated, and there is a high possibility that bubbles are generated, and the electric field to be distributed to the innermost layer 210A, So that the insulation performance of the intermediate connection box can be stabilized.

In addition, since the remaining regions 210B to 210D except for the innermost layer 210A of the reinforcing insulating layer 210 are all covered with the composite insulating paper, the productivity can be improved and the productivity can be improved remarkably and the defect ratio can be further reduced .

Meanwhile, in another embodiment, the reinforcing insulating layer 210 may include a first intermediate layer 210B made of composite insulating paper and a second intermediate layer 210C made of insulating paper.

At this time, the first intermediate layer 210B and the second intermediate layer 210C provided between the innermost layer 210A and the outermost layer 210D of the reinforcing insulating layer 210 have the second ends 14a2, And may be disposed at the same distance from the center of the cable (100A) and the end (14a3).

In this case, since the innermost layer 210A of the reinforcing insulating layer 210 is composed of an insulating ground layer and the first intermediate layer 210B is composed of composite insulating paper, the resistance electric field of the direct current power cable, A large amount of electric field is distributed in the first intermediate layer 210B, which is formed of composite insulating paper having a relatively higher resistivity than the kraft paper of the innermost layer 210A of the reinforcing insulating layer 210 according to the distribution characteristics. As a result, relatively high temperature occurs in the operation of the cable, and the contraction / expansion of the insulating oil is relatively actively generated. Therefore, there is a high possibility that air bubbles are generated and an electric field shared in the innermost layer 210A of the reinforcing insulating layer, So that it is possible to stabilize the insulation performance.

The intermediate connection case 200 may further include a slope part 210B of the second reinforcing insulating layer 2102 and a connection case external semiconductive layer 230 wound on the outer surface of the straight part 210A.

The connection box outer semiconductive layer 231 disposed on the straight portion 210A of the second reinforcing insulating layer 2102 may be formed to surround the straight portion 210A of the second reinforcing insulating layer 2102, For example, carbon black having semi-conductive properties can be formed by extrusion.

A connection box outer semiconductive layer 232 disposed on the slope portion 210B of the second reinforcing insulating layer 2102 is formed by restoring the cable semiconductive layer 16 along the outer surface of the slope portion 210B. The connection box outer semiconductive layer 232 is formed in a slope shape corresponding to the outer surface of the slope portion 210B so that an equipotential line continuing from the cable insulation layer 14A to the intermediate connection box 200 is connected to the outer side The electric field can be controlled so as to be distributed according to the geometrical shape of the semiconductive layer 232.

The connection box outer semiconductive layer 230 can be energized with the outer semiconductive layer 16 of the cable.

The connection box outer semiconductive layer 230 may have a lower volume resistance than the cable insulation layers 14A and 14B, the reinforcing insulation layer 210, and the electric field shift layer 220. [ The connection box outer semiconductive layer 230 has a lower volume resistivity than the cable insulation layers 14A and 14B, the reinforcing insulation layer 210 and the electric field shift layer 220. The second reinforcing insulation layer 2102, And the metal shielding layer 260 can be prevented from being abruptly changed.

Then, a metal layer that is electrically connected to the metal sheath 22 of the cable 100A is restored on the reinforcing insulating layer 210, and the protective copper pipe 240 is covered.

The protective copper pipe 240 protects the inside of the connection box from the outside and is energized with the metal sheath 22 of the cable 100 to serve as a path for the fault current.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention.

Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments.

The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

100: Cable
11: Conductor
12: inner semiconductive layer
14: Cable insulation layer
16: outer semiconductive layer
200: Medium connection
210: reinforced insulation layer
220: electric field shift layer
230: Outer sheath layer

Claims (22)

A direct current power cable intermediate connection system comprising a pair of direct current power cables and an intermediate connection box connecting the direct current power cables to each other,
The DC power cable
A conductor serving as a path of current for transmitting power;
An inner semiconductive layer formed to surround the conductor;
A cable insulation layer formed on the outer side of the inner semiconductive layer and made of insulating paper impregnated with insulating oil so that a current flowing along the conductor does not leak to the outside;
An outer semiconductive layer formed to surround the cable insulation layer;
A metal sheath formed to surround the outer semiconductive layer; And,
The end portions of the pair of power cables in which the conductor, the inner semiconductive layer, the cable insulating layer, and the outer semiconductive layer are sequentially exposed are formed so as to face each other,
The intermediate junction box includes:
A conductor connecting portion for electrically connecting the conductors of the pair of cables to each other;
A first reinforcing insulating layer having an insulating paper wound around the conductor connecting portion, the exposed inner semiconductive layer and the cable insulating layer to form an outer diameter of the cable insulating layer and having inclined surfaces at both ends in the longitudinal direction;
Wherein the first reinforcing insulating layer and the exposed cable insulating layer are formed on both ends of the straight portion and the width in the cable longitudinal direction is constant in the radial direction, A second reinforcing insulating layer having a slope portion decreasing in a direction of the first reinforcing insulating layer; And
A field shift layer disposed between the slope portion and the cable insulation layer; And,
Further comprising a connection box outer semiconductive layer wound on an outer surface of the slope portion,
Wherein the second reinforcing insulating layer is composed of a plurality of insulating ground layers laminated in the radial direction and each of the plurality of insulating ground layers constituting the slope portion of the second reinforcing insulating layer is formed of a wide width winding portion system. The method according to claim 1,
Wherein the electric field shift layer extends not only between the slope portion and the cable insulation layer but also to the straight portion. The method according to claim 1,
Wherein the electric field shift layer has a lower volume resistance than the second reinforcing insulating layer or the cable insulating layer. The method of claim 3,
The cable insulation layer, the first reinforcing insulation layer, and the second reinforcing insulation layer are formed of composite insulation paper,
Wherein the electric field shift layer is made of a material whose volume resistance is 10 ² times or more lower than that of the composite insulating paper. 5. The method of claim 4,
Wherein the electric field shift layer is formed to extend between the cable insulation layer and the metal sheath. 6. The method of claim 5,
Wherein the electric field shift layer is formed to have a thickness of 5 to 15% of the thickness of the cable insulation layer. delete The method according to claim 1,
Wherein the connection box outer semiconductive layer is made of a material having a volume resistivity lower than that of the second reinforcing insulation layer and the electric field shift layer. The method according to claim 1,
Wherein the electric field shift layer is made of kraft paper. delete The method according to claim 1,
Wherein the second reinforcing insulating layer is composed of a plurality of insulating ground layers laminated in the radial direction,
Wherein each of the plurality of dielectric layers surrounding the electric field shift layer in the radial direction is formed of a wide-width winding portion. A pair of DC power cables having a conductor, an inner semiconductive layer, a cable insulation layer, an outer semiconductive layer, and a metal sheath and sequentially exposing the conductor, the inner semiconductive layer, the cable insulating layer and the outer semiconductive layer, In an intermediate connection box for a DC power cable for connection,
A conductor connecting portion for electrically connecting the conductors of the pair of cables to each other;
A first reinforcing insulating layer having an insulating paper wound around the conductor connecting portion, the exposed inner semiconductive layer and the cable insulating layer to form an outer diameter of the cable insulating layer and having inclined surfaces at both ends in the longitudinal direction;
Wherein the first reinforcing insulating layer and the exposed cable insulating layer are formed on both ends of the straight portion and the width in the cable longitudinal direction is constant in the radial direction, A second reinforcing insulating layer having a slope portion decreasing in a direction of the first reinforcing insulating layer; And
A field shift layer disposed between the slope portion and the cable insulation layer; And,
Further comprising a connection box outer semiconductive layer wound on an outer surface of the slope portion,
Wherein the second reinforcing insulating layer is composed of a plurality of insulating ground layers laminated in the radial direction,
Wherein each of the plurality of insulating ground layers constituting the slope portion of the second reinforcing insulating layer is formed of a wide-width winding portion. 13. The method of claim 12,
Wherein the electric field shift layer extends not only between the slope portion and the cable insulation layer but also extends to the straight portion. 13. The method of claim 12,
Wherein the electric field shift layer has a volume resistance lower than that of the second reinforcing insulating layer or the cable insulating layer. 15. The method of claim 14,
The cable insulation layer, the first reinforcing insulation layer, and the second reinforcing insulation layer are formed of composite insulation paper,
Wherein the electric field shift layer is made of a material whose volume resistance is 10 ² times or more lower than that of the composite insulating paper. 16. The method of claim 15,
Wherein the electric field shift layer is formed to extend between the cable insulation layer and the metal sheath. 17. The method of claim 16,
Wherein the electric field shift layer is formed to have a thickness of 5 to 15% of the thickness of the cable insulation layer. delete 13. The method of claim 12,
Wherein the connection box outer semiconductive layer is made of a material having a volume resistivity lower than that of the second reinforcing insulation layer and the electric field shift layer. 13. The method of claim 12,
Wherein the electric field shift layer is made of kraft paper. delete 13. The method of claim 12,
Wherein the second reinforcing insulating layer is composed of a plurality of insulating ground layers laminated in the radial direction,
Wherein each of the plurality of insulating ground layers surrounding the electric field shift layer in the radial direction of the plurality of insulating ground layers is formed of a wide-width winding portion.

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