KR20180069325A - Oil supply system of joint box for oil impregnated cable and method for the same - Google Patents

Abstract

The present invention relates to a refueling system of a connection box which can sufficiently impregnate insulating oil in a connection box when refueling the connection box connecting an insulating oil impregnation cable with the insulating oil, and a method thereof. The refueling system of a connection box for an insulating oil impregnation cable comprises: an insulating oil supply part receiving the insulating oil, and connected to the connection box to supply the insulating oil to the connection box; and a pressurizing part connected to the insulating oil supply part, and injecting a predetermined gas into the insulating oil supply part to pressurize the insulating oil.

Description

Technical Field [0001] The present invention relates to a joint box for oil impregnated cable,

The present invention relates to a connection box lubrication system for an insulating oil impregnated cable, and more particularly, to a connection system for connecting an insulation oil impregnated cable or an insulating oil impregnated cable to a working line, And more particularly to a connection box lubrication system and method capable of lubrication of the connection box with high-viscosity insulating oil.

Generally, a power cable is used to power a desired location through the ground, ground, or seabed using a power-supplying conductor. For such a power cable, it is very important to insulate the conductor. For this purpose, the insulating layer for insulating the conductor is made of XLPE (Cross-linked Polyethylene) or the like, I am using it.

The so-called 'ground insulated cable' in which the insulating paper is wound to form an insulating layer is referred to as an 'oil filled cable' (hereinafter referred to as 'OF') and a high viscosity insulating oil impregnated cable , And a mass impregnated (MI) cable).

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.

Meanwhile, the power cables are connected by a joint box at intervals of several hundred meters or tens of km, and the ends of the power cables are connected by a termination 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.

When the insulation-oil-impregnated cable is connected as described above, the pressure inside the cable and the junction box due to a change in the external environment such as a seasonal change is kept constant to prevent deterioration of the insulation performance of the junction box, So that the connection oil is injected into the connection box. For example, in the case of an OF cable, a cable impregnated with a low-viscosity insulating oil is used. Therefore, when the OF cables are connected to each other, the connection box is filled with the same low-viscosity insulating oil as the insulating oil of the OF cable .

However, in the case of the MI cable, impregnation is performed using a high viscosity insulating oil having a relatively high viscosity as described above. Viscosity of the high-viscosity insulating oil is relatively high and fluidity is very low. Therefore, when the insulating oil is injected into the junction box, it is difficult to inject the high viscosity insulating oil using the high viscosity insulating oil. Therefore, the connection box for the MI cable was not made of the high-viscosity insulating oil used in the cable but was injected using a low-viscosity insulating oil. As a result, the MI cable connecting box is filled with low-viscosity insulating oil different from the insulating oil used in the MI cable. Therefore, the low-viscosity insulating oil compatible with the insulating oil used in the cable must be fed, Which is inconvenient in assembling the connection box.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a connection box oiling system and method capable of satisfactorily impregnating insulating oil in a connection case when a connection case for connecting the insulating oil impregnated cables to each other is made of insulating oil.

According to an embodiment of the present invention, there is provided a connection system for connecting an insulation-oil-impregnated cable, comprising: an oil-supply system for supplying the connection oil- An insulating oil supply unit for supplying the insulating oil to the connection box; And a pressing part connected to the insulating oil supplying part and injecting a predetermined gas into the insulating oil supplying part to press the insulating oil; And the main oil of the insulating oil and the pressure of the insulating oil can be simultaneously advanced into the connection box.

In the present invention, the insulating oil in the connection box is continuously supplied to the connection box by the amount of the insulation oil reduced as the insulation oil of the connection box is impregnated into the connection box, State can be maintained.

In the present invention, while the insulating container is filled with the insulating oil, the pressing portion may apply the pressure to the insulating oil in the connection box by flowing the predetermined gas into the insulating oil supply portion.

In the present invention, the control unit may further include a controller for controlling the pressure and time of the predetermined gas injected from the pressurizing unit to the insulating oil supply unit.

In the present invention, the control unit may control the pressure of the insulating oil supply unit to increase for a predetermined time, or the pressure of the pressure oil supplied from the pressure oil supply unit to the insulating oil supply unit to be constant, It is possible to control the amount of gas.

The solenoid valve may further include a solenoid valve disposed between a conduit connecting between the connection case and the insulating oil supply unit, or between a conduit connecting between the insulating oil supply unit and the pressing unit.

In the present invention, the predetermined gas may be nitrogen (N2) gas.

In the present invention, even if the power supply is interrupted, the pressure in the connection box can be maintained.

In the present invention, a discharge pipe through which the insulating oil is discharged in the connection box; A vacuum pump connected to the discharge pipe to maintain the inside of the connection box in a vacuum state; And a vacuum measurement unit connected to the discharge pipe and sensing a vacuum degree of the connection case.

According to another aspect of the present invention, there is provided a method for injecting a connection box for an insulating oil impregnated cable, the method comprising: evacuating the connection box by evacuating the connection box through which the insulating oil impregnated cable is connected by the insulating oil; Filling the connection box with the insulating oil; Filling the insulating fluid into the connection case and simultaneously injecting a predetermined gas into the insulating oil supply portion which is an inflow of the insulating oil to pressurize the insulating oil; And injecting the predetermined gas into the insulating oil supply unit to pressurize the insulating oil even after the insulating oil is filled in the connection box; .

In the present invention, the insulating oil in the connection box is continuously supplied to the connection box by the amount of the insulation oil reduced as the insulation oil of the connection box is impregnated into the connection box, State can be maintained.

In the present invention, the predetermined gas may flow into the insulating oil supply portion while applying pressure to the insulating oil in the connection box while the connection oil is kept filled with the insulating oil.

In the present invention, the predetermined gas may be nitrogen (N2) gas.

In the present invention, even if the power supply is interrupted, the pressure in the connection box can be maintained.

According to an embodiment of the present invention, when the high-viscosity insulating-oil-impregnated cables are connected to each other or connected to a working line, impregnation of the reinforcing insulating layer by the insulating oil in the connecting box provided with the reinforcing insulating layer becomes uniform, It is possible to prevent deterioration in insulation performance of the connection box according to the present invention.

1 is a partially cutaway perspective view showing the construction of an insulating oil impregnated cable according to an embodiment of the present invention.
Fig. 2 is a schematic view showing the configuration of a lubrication system for supplying a connection box when connecting the insulating-oil-impregnated cables to each other. Fig.
3 is a flowchart schematically showing a connection method for connecting a connection vessel for an insulating oil impregnated cable 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.

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, the power cable 100 includes a conductor 11, an inner semiconductive layer 12, an insulating layer 14, and an outer semiconductive layer 16, and extends along the conductor 11 in the cable longitudinal direction And a cable core portion (10) for transmitting electric power and preventing 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 has a circular central strand 11A and a rectangular strand 11C composed of a square strand 11B stranded to surround the circular central strand 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. Further, when a gap is formed between the surface of the conductor 11 and the insulating layer 14 described later, the insulating 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 insulation layer 14 described later. In addition, by suppressing uneven distribution of charge on the conductor surface, it is possible to uniformize the electric field and prevent a gap from being formed between the conductor 11 and the insulating layer 14, thereby suppressing corona discharge and dielectric breakdown .

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

The insulating layer 14 may be formed of insulating paper impregnated with insulating oil. That is, the insulating layer 14 may be formed by winding a plurality of layers of insulating paper so as to surround the inner semiconductive layer 12, and then impregnating the insulating oil after the cable core portion is formed. As the insulating oil is absorbed by the insulating paper, the insulating property of the 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.

When using a low-viscosity insulating oil with a relatively low viscosity, it is necessary to pressurize the insulating oil by using an oil supply facility or the like in order to keep the insulating paper impregnated with the insulating oil and to prevent pores in the insulating layer due to the flow of the insulating oil . 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 insulating layer 14 may be formed by winding a kraft, and impregnating the insulating 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 insulating layer 14, the thermoplastic resin such as the polypropylene resin is not impregnated with the insulating oil, and the impregnation temperature during cable manufacturing or the operation The thermal expansion is caused by the 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 radial direction of the cable, do. Therefore, the insulating oil of the insulating layer, that is, the insulating layer formed on the inner semiconductive layer 12 belonging to the conductor straight section is lowered in viscosity and thermally expanded to move outward. When the cable temperature is lowered, The viscosity becomes high and it does not return to the original state, so that voids may be generated in the insulating layer portion of the conductor straight section.

In addition, a high electric field is applied to the insulating layer, which is formed in the direction of the outer semiconductive layer 16, belonging to the section under the metal sheath where the electric field gradually becomes higher 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 region of the insulating layer 14 including the insulation weak portion. That is, the insulating layer 14 is divided into a first insulating layer, a second insulating layer, and a third insulating layer in the direction of the external semiconductive layer 16, which will be described later, in the internal semiconductive layer 12, Alternatively, only the kraft may be used for the third insulating layer, and the composite insulating paper may be used for the second insulating layer.

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

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

The outer semiconductive layer 16 may be provided outside the insulating 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 or the like to an insulating material such as an inner semiconductive layer, Uneven charge distribution between the metal sheath 14 and a metal sheath 22 described later is suppressed to stabilize the insulation performance. The outer semiconductive layer 16 smoothes the surface of the insulating layer 14 in the cable so as to alleviate the concentration of the electric field, thereby preventing corona discharge and also physically protecting the insulating layer 14 . 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 holes may be formed to facilitate impregnation of the 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 shows a connection box 200 for connecting the dielectric-oil-impregnated cables 100A and 100B having the above-described structure to one another and a connection box oiling system 300 for supplying the connection box 200 with insulating oil Fig.

2, first, in a state where the insulating layers 14A and 14B and the conductors 11A and 11B are exposed in the pair of insulating-oil-impregnated cables 100A and 100B, the conductors 11A and 11B of the insulating-oil- And 11B are pressed or welded to the compression sleeve 19 and electrically connected to each other.

The reinforcing insulating layer 210 covering at least a part of the insulating layers 14A, 14B and 14C including the connecting portions of the conductors 11A and 11B is formed after connecting the respective conductors of the insulating oil impregnated cables 100A and 100B, Respectively.

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 an insulating paper. The outermost layer 210D may be a composite insulating paper.

The intermediate connection case 300 according to the present embodiment may include a reinforcing insulating layer made of an insulating paper and / or a composite insulating paper when the reinforcing insulating layer 210 is provided. Hereinafter, the present invention will be described in detail.

2, a predetermined space may remain between the compression sleeve 330 and the insulation layer 14A located at the innermost side of the insulation layer 14 of the cable 100 . The remaining space between the compression sleeve 330 and the insulation layer 14A located on the innermost side of the insulation layer 14 of the cable 100 encapsulates an insulating paper such as a kraft paper.

The outer surface of the innermost layer 210A made of insulating paper of the reinforcing insulating layer 210 is connected to the outer surface of the insulating layer 14A located on the innermost side of the insulating layer 14 of the cable 100, As shown in FIG.

The outer surface of the compression sleeve 330 may be surrounded by a semi-conductive tape 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, which is located on the innermost side of the insulation layer 14 of the cable, than the outer surface of the insulation layer 14A, 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.

The outer surface of the innermost layer 210A made of insulating paper of the reinforcing insulating layer 210 and the insulating layer 14A located at the innermost side of the insulating layer 14 of the cable If a step is generated because it is not located at the same distance, 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 insulating layer 14 of the cable 100. Since the exposed conductor 210 of the cable is connected by the compression sleeve 330, not only the height of the conductor section increases by the thickness of the compression sleeve 330 but also a relatively large amount of heat is generated in the conduction of the cable. Since the insulation reinforcing layer 310 is formed by winding a plurality of insulating sheets or composite insulating sheets and is relatively weak in insulation, the outermost layer 210D of the insulating reinforcing layer 310 may be formed on the outer surface of the cable insulating layer 14 It is necessary to reinforce the insulation performance.

The outermost layer 210D of the insulating reinforcing layer 310 is composed of a composite insulating paper having an excellent dielectric strength as compared with an insulating paper. In this case, in the operation of the cable 100, the insulation layer 14 of the cable 100 and the regions 301A to 210C located inside the outermost layers of the reinforcing insulation layer 210 The concentrated electric field can 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 .

Only 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 The electric field is distributed in 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 of the innermost layer 210A of the insulating reinforcing layer 210A according to the resistive electric field distribution characteristic of the DC cable . Accordingly, the relatively high temperature in the operation of the cable causes the contraction / expansion of the insulating oil to be relatively actively generated, so that there is a high possibility that air bubbles are generated and the electric field shared by the innermost layer 210A of the insulating reinforcing layer, It is possible to stabilize the insulation performance.

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.

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 may be formed of an insulating layer Are disposed at the same distance from the center of the cable 200 and the composite insulation layer 214B and the outer insulation layer 214C of the cable 214. The reinforcing insulating layer 210 may be formed of the same material and / or the same material as that of the insulating layer 214 of the cable 200 under the outer diameter of the exposed insulating layer 214 of the cable 200. In other words, Or configuration. The innermost layer 210A and the outermost layer 210D of the cable 200 are made of insulating paper and composite insulating paper, respectively, as in the above-described embodiment.

In this case, since the innermost layer 210A of the reinforcing insulating layer 210 is composed of an insulating layer and the first intermediate layer 210B is composed of a composite insulating paper, the resistive electric field distribution of the DC cable, The electric field is distributed to the first intermediate layer 210B formed of the composite insulating paper having a relatively higher resistivity than the kraft paper of the innermost layer 210A of the insulating reinforcing layer depending on the characteristics. Accordingly, the relatively high temperature in the operation of the cable causes the contraction / expansion of the insulating oil to be relatively actively generated, so that there is a high possibility that air bubbles are generated and the electric field shared by the innermost layer 210A of the insulating reinforcing layer, It is possible to stabilize the insulation performance.

A semiconductive layer electrically connected to the outer semiconductive layer 16 of the cable and a metal layer electrically connected to the metal sheath 22 of the cable are restored on the reinforcing insulating layer 210 and covered with the protective copper tube 240 . 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.

It is necessary to insulate the connection box 200 with insulating oil to ensure insulation performance. Specifically, it is necessary to fill the space between the reinforcing insulating layer 210 and the protective copper pipe 240 with insulating oil, and to impregnate the reinforcing insulating layer formed by winding the kraft insulating paper or the composite insulating paper with insulating oil to improve the insulating performance . but, The composite insulating paper is a structure in which a kraft paper is adhered to both sides or one side of a thermoplastic resin film such as a polypropylene resin. The thermoplastic resin film such as polypropylene resin does not permeate insulating oil, Since the insulating layer 240 is formed only in the gap of the composite insulating paper and impregnated with the high viscosity insulating oil, impregnation is difficult.

Further, in the structure of the connection box having the above-described configuration, the reinforcing insulating layer 210 is in a state of being impregnated with the insulating oil, but when bubbles or the like are formed between the insulating oil or impurities penetrate, ≪ / RTI >

Therefore, the following will describe a connection box lubrication system for preventing deterioration of the insulation performance as described above and further improving the overall insulation performance.

The connection box oiling system 300 includes an inlet pipe 310 provided in a protective copper pipe 240 forming the connection case 200 to provide a passage through which the insulating oil moves, A pressurizing unit 350 connected to the insulative oil supply unit 340 and injecting a predetermined gas into the insulative oil supply unit 340 to pressurize the insulative oil, A discharge pipe 330 provided in a direction opposite to the inflow pipe 310 along the protective copper pipe 240 to discharge the insulating oil and a discharge pipe 330 connected to the discharge pipe 330 to discharge the inside of the connection case 200 into a vacuum state A vacuum measurement unit 370 connected to the discharge pipe 330 for sensing a degree of vacuum of the connection case 200 and a pressure sensor 350 for detecting the degree of vacuum of the connection case 200 from the pressure supply unit 340, And a controller 38 for controlling the pressure and time of the predetermined gas 0).

The protective copper pipe 240 may include an inflow pipe 310 and a discharge pipe 330. The inlet pipe 310 and the outlet pipe 330 provide a passage through which the insulating oil to be described later moves. The inlet pipe 310 and the outlet pipe 330 are formed in opposite directions along the outer circumference of the protective copper pipe 240.

That is, a pair of pipes are formed in opposite directions along the outer circumference of the protective copper pipe 240, and a pipe (or a pipe facing gravity direction) facing the ground from the protective copper pipe 240 is connected to the inlet pipe 310, And a pipe (opposite to the gravity direction) located in the opposite direction of the inflow pipe 310 in the protective copper pipe 240 may be defined as a discharge pipe 330. The connection pipe 300 is filled with the insulating oil from the bottom of the connection case 300 because the insulating oil flows in the opposite direction to the gravity direction through the inlet pipe 310 facing the ground, Air bubbles may be generated within the chamber.

The inflow pipe 310 and the discharge pipe 330 are configured to penetrate the protective copper pipe 240 and to supply the reinforcing insulating layer 210 and the insulating oil to the metal layer and the semiconductor layer restored on the reinforcing insulating layer . Therefore, when the insulating oil is injected through the inlet pipe 310 as described later, the injected insulating oil impregnates the reinforcing insulating layer 210 through the semiconductive layer and the metal layer, . This will be described in detail later.

The inflow pipe 310 may be connected to an insulating oil supply unit 340 containing an insulating oil or an insulating compound for impregnating the reinforcing insulating layer 210. The insulating oil supply unit 340 may be, for example, a pressure tank for storing insulating oil. The inlet pipe 310 may be provided with a first valve 312 for selectively cutting off the supply of the insulating oil supplied from the insulating oil supply unit 340. The insulating oil supplied into the metal sheath 20 can be selectively blocked by operating the first valve 312.

The pressing portion 350 is connected to the insulating oil supplying portion 340 and a predetermined gas in the pressing portion 350 may be injected into the insulating oil supplying portion 340 to press the insulating oil. The pressing portion 350 may be formed of, for example, a pump. The pressurizing unit 350 may be directly connected to the insulating oil supply unit 340 and may not be connected to the inflow pipe 310. That is, a pipe connecting the pressurizing unit 350 and the insulating oil supply unit 340 is provided separately from the inflow pipe 310, and the pressurizing unit 350 is not connected to the inflow pipe 310, (340) via the conduit.

The pressing portion 350 may include a predetermined gas therein. For example, the predetermined gas may be a nitrogen (N2) gas. The pressurizing unit 350 can pressurize the insulating oil in the insulating oil supply unit 340 by injecting the predetermined gas into the insulating oil supply unit 340. The insulating oil supply unit 340 is connected to the connection box 200. The predetermined gas is injected into the insulation oil supply unit 340 to press the insulation oil so that the insulation oil in the connection case 200 is also pressurized, The pressure in the junction box 200 may increase.

A second valve 314 may be disposed in a line connecting the pressurizing unit 350 and the insulating oil supply unit 340. The predetermined gas may be introduced into or cut off from the insulating oil supply portion 340 by the pressing portion 350 as the second valve 314 is opened or closed. Accordingly, it is possible to determine whether the pressurizing unit 350 is pressurized through the second valve 314.

The connection box lubrication system for an insulating oil impregnated cable according to an embodiment of the present invention may simultaneously advance the oil of the insulating oil and the oil of the insulating oil into the connection case 200. That is, by supplying the insulating oil to the connection box 200 continuously by the amount of the insulation oil that decreases as the insulation oil in the connection box 200 is impregnated into the insulation layer 240 of the connection box 200 So that the insulating fluid can be maintained in the connection box 200. The pressurizing unit 350 may be configured to allow the predetermined gas to flow into the insulating oil supply unit 340 so that the pressure of the insulating gas in the connection case 200 Pressure can be applied.

That is, the predetermined gas flows into the insulating oil supply part 340, so that the injection of the insulating oil into the connection case 200 and the pressing of the insulating oil can proceed simultaneously. It is possible to solve the problem that a part of the reinforcing insulating layer 210 is not impregnated because the pressure in the connecting box 200 due to the inflow of the predetermined gas is maintained while keeping the insulating oil filled, The insulation breakdown phenomenon due to the non-impregnation of the layer 210 can be improved. Also, since the reinforcing insulating layer 210 can be impregnated even when the connection box 200 is filled with the insulating oil, the insulating oil can be easily impregnated without keeping the connection box 200 horizontal.

The control unit 380 may control the pressure and time of the predetermined gas injected from the pressing unit 350 into the insulating oil supply unit 340. That is, the control unit 380 is connected to the pressurizing unit 350 and the insulating oil supply unit 340 to control the predetermined gas inflow from the pressing unit 350 to the insulating oil supply unit 340, The supply of the insulating oil from the supply part 340 to the connection box 200 can be controlled.

The control unit 380 may control the pressure in the insulating oil supply unit 340 to increase for a predetermined time or increase the pressure in the insulating oil supply unit 340 to a predetermined value, The amount of the predetermined gas injected into the insulating oil supply unit 340 can be controlled. The control unit 380 controls the amount of the predetermined gas injected from the pressing unit 350 to the insulating oil supply unit 340 to be greater than the predetermined amount of time The pressing unit 350 can be controlled to increase the pressure. When the pressure in the insulating oil supply unit 340 is to be maintained constant for a predetermined time, the controller 380 controls the pressure of the predetermined gas injected from the pressure unit 350 to the insulating oil supply unit 340 It is possible to control the pressing portion 350 so that the amount is constant with time.

A first valve 312 disposed between the connection box 200 and the insulation oil supply unit 340 and disposed between the insulation oil supply unit 340 and the pressure unit 350; The third valve 332 disposed between the vacuum pump 360 and the connection box 200 may be a solenoid valve as an example.

The first valve 312, the second valve 314 and the third valve 332 which are solenoid valves are connected to the insulating oil supply unit 340, the pressing unit 350, the control unit 380, and / When the power supply of the connection box 200 is turned off, the pressure in the connection box 200 can be maintained in a state before the power supply is turned off. Therefore, stable impregnation is possible.

The discharge pipe 330 provided in the direction opposite to the inflow pipe 310 may be connected to a vacuum pump 360 capable of maintaining the interior of the metal sheath 20 in a vacuum state having a predetermined degree of vacuum. The discharge pipe 330 may include a third valve 332 for selectively blocking the discharge pipe 330. The discharge pipe 330 may include a vacuum pump 360 and a vacuum pump 360. [ And is connected to the vacuum measurement unit 370. The vacuum pump 360 discharges the air inside the metal sheath 20 through the discharge pipe 330 so that the inside of the metal sheath 20 is formed into a vacuum state having a predetermined degree of vacuum, The bubbles and the like remaining in the reinforcing insulating layer 210 in the insulating layer 20 are removed.

Hereinafter, the impregnation process for impregnating the reinforcing insulating layer 210 to prevent deterioration of insulation performance will be described.

3 is a flow chart of the impregnation process according to one embodiment of the present invention. 3, the impregnating process includes a defoaming step 500A for removing bubbles from the reinforcing insulating layer 210 in the protective copper pipe 240, a feeding step 500B for injecting the insulating oil into the protective copper pipe 240, And an injection / pressurization step (500C) of injecting the insulating oil while applying a predetermined pressure into the protective copper pipe (240).

The defoaming step 500A is a step of discharging the bubbles remaining in the reinforcing insulating layer 210 in the protective copper pipe 240 to the outside of the protective copper pipe 240 and removing the bubbles.

Specifically, the first valve 312 and the second valve 314 of the inflow pipe 310 are closed to open the third valve 332 in a state in which there is no inflow of the insulating oil through the inflow pipe 310 do. The vacuum pump 360 is driven in a state where the third valve 332 is open to discharge the air inside the protective copper pipe 240 to the outside so as to maintain the inside of the protective copper pipe 240 in a predetermined vacuum state . In this case, it is preferable that the degree of vacuum is appropriately maintained so that the air bubbles remaining in the reinforcing insulating layer 210 may be discharged when the air inside the protective copper pipe 240 is discharged. The vacuum degree maintenance is performed by controlling the driving of the vacuum pump 360 so as to maintain a predetermined degree of vacuum through the vacuum measurement unit 370.

The air inside the protective copper pipe 240 is discharged by driving the vacuum pump 360 so that bubbles remaining in the reinforcing insulating layer 210 are discharged to the outside through the discharge pipe 330. Then, the oiling step 500B for injecting the insulating oil into the protective copper pipe 240 is started.

The lubrication is performed by opening the first valve 312 with the third valve 332 opened. The first valve 312 is opened and the insulating oil is supplied to the inside of the protective copper pipe 240 through the insulating oil supply portion 340. At this time, since the inflow pipe 310 is provided toward the ground as described above, it may be difficult to inflow the insulating oil due to gravity. Therefore, the second valve 314 is opened and the pressing portion 350 is driven to apply a predetermined pressure toward the insulating oil supply portion 340, so that the inflow of the insulating oil can be performed more smoothly.

In addition, a predetermined temperature may be applied to smooth the inflow of the insulating oil. A heater 341 may be disposed at one side of the insulating oil supply unit 340 to apply a temperature to the insulating oil. If the temperature is increased as described above, the flow of the insulating oil can be promoted and the inflow of the insulating oil can be performed more easily.

The insulating oil flowing into the protective copper pipe 240 through the inflow pipe 310 rises at a lower portion of the protective copper pipe 240 to reinforce the insulating paper constituting the reinforcing insulating layer 210. In this case, since the outer semiconductive layer 16 provided outside the reinforcing insulating layer 210 is formed by winding the insulating paper or the like, the insulating oil impregnates the reinforcing insulating layer 210 through the outer semiconductive layer 16 do.

Meanwhile, since the vacuum pump 360 connected to the inflow pipe 310 is continuously driven even when the insulating oil is injected into the protective copper pipe 240, the insulating oil introduced into the protective copper pipe 240 is bubbled The bubbles are discharged through the discharge pipe 330 to the outside. The inside of the protective copper pipe 240 is filled with insulating oil and then the third valve 332 is closed. Here, when the insulating oil is discharged to the outside through the discharge pipe 330, it can be determined that the inside of the protective copper pipe 240 is filled with the insulating oil.

Subsequently, a lubrication / pressurization step (500C) is performed to apply a predetermined pressure to the inside of the protective copper pipe (240). The lubrication / pressurization step 500C is performed in a state where the third valve 332 is closed and the first valve 312 and the second valve 314 are opened. That is, even after the insulating oil is filled in the protective copper pipe 240, the predetermined gas may be injected into the insulating oil supply unit 340 to pressurize the insulating oil.

In more detail, according to an embodiment of the present invention, a connecting fluid supplying method for an insulating oil impregnated cable can simultaneously advance the oil of the insulating oil and the insulating oil to the connection case 200. By continuously supplying the insulating oil to the connection box 200 by the amount of the insulating oil that decreases as the insulating oil in the connection box 200 is impregnated into the insulating layer 240 of the connection box 200, So that the insulating oil can be kept filled in the connection box 200. The pressurizing unit 350 may be configured to allow the predetermined gas to flow into the insulating oil supply unit 340 so that the pressure of the insulating gas in the connection case 200 Pressure can be applied.

That is, the predetermined gas flows into the insulating oil supply part 340, so that the injection of the insulating oil into the connection case 200 and the pressing of the insulating oil can proceed simultaneously. It is possible to solve the problem that a part of the reinforcing insulating layer 210 is not impregnated because the pressure in the connecting box 200 due to the inflow of the predetermined gas is maintained while keeping the insulating oil filled, The insulation breakdown phenomenon due to the non-impregnation of the layer 210 can be improved. Further, the insulating oil filled in the protective copper pipe 240 can uniformly impregnate the reinforcing insulating layer 210, and further, the air bubbles can be removed and the remaining voids can be filled with insulating oil, thereby preventing deterioration of the insulation performance.

In addition, a predetermined temperature may be applied to facilitate impregnation with insulating oil. When the temperature is increased as described above, the flow of the insulating oil is promoted, so that the impregnation of the reinforcing insulating layer by the insulating oil can be performed more easily.

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.

10. Conductor
12. Internal semiconducting layer
14. Insulation layer
16 .. outer semiconductive layer
100 .. Cables
200 .. connection box
240 .. Protection duct
300 .. Lubrication system
310 .. inlet pipe
312. First valve
314 .. Second valve
330 .. discharge pipe
332 .. Third valve
340. Insulating oil supply part
350,
360 .. Vacuum pump
370 .. Vacuum measuring part

Claims (14)

A lubrication system for lubricating a connection box to which an insulating oil-impregnated cable is connected by the insulating oil,
An insulating oil supply unit that receives the insulating oil and is connected to the connection case to supply the insulating oil to the connection case; And
A pressing part connected to the insulating oil supplying part and injecting a predetermined gas into the insulating oil supplying part to press the insulating oil; And,
Wherein the main oil of the insulating oil and the pressure of the insulating oil proceed simultaneously in the connection box. The method according to claim 1,
The insulating oil in the connection box is continuously supplied to the connection box by the amount of the insulation oil which decreases as the insulation oil of the connection box is impregnated into the connection box to maintain the state of the insulation oil in the connection box Features a connecting box for insulating oil impregnated cable lubrication system. 3. The method of claim 2,
Wherein the pressurizing portion applies pressure to the insulating oil in the connection box by introducing the predetermined gas into the insulating oil supply portion while the connection portion is kept filled with the insulating oil. system. The method according to claim 1,
Further comprising a control unit for controlling the pressure and time of the predetermined gas injected from the pressurizing unit to the insulating oil supply unit. 5. The method of claim 4,
Wherein the control unit controls the amount of the predetermined gas injected from the pressing unit to the insulating oil supply unit so that the pressure in the insulating oil supply unit is increased for a predetermined time or the pressure in the insulating oil supply unit is maintained constant And a control unit for controlling the operation of the compressor. The method according to claim 1,
Further comprising a solenoid valve disposed between a conduit connecting between the connection box and the insulating oil supply unit or between a conduit connecting between the insulation oil supply unit and the pressurization unit. The method according to claim 1,
Wherein the predetermined gas is nitrogen (N2) gas. The method according to claim 1,
And the pressure in the connection box is maintained even when the power supply is interrupted. The method according to claim 1,
A discharge pipe through which the insulating oil in the connection box is discharged;
A vacuum pump connected to the discharge pipe to maintain the inside of the connection box in a vacuum state; And
And a vacuum measurement unit connected to the discharge pipe and sensing a degree of vacuum of the connection box. A filling method for filling a connection box to which an insulating oil-impregnated cable is connected with the insulating oil,
Evacuating the junction box;
Filling the connection box with the insulating oil;
Filling the insulating fluid into the connection case and simultaneously injecting a predetermined gas into the insulating oil supply portion which is an inflow of the insulating oil to pressurize the insulating oil; And
Injecting the predetermined gas into the insulating oil supply unit to pressurize the insulating oil even after the insulating oil is filled in the connection box; And a connection pipe for the insulating oil-impregnated cable. 11. The method of claim 10,
The insulating oil in the connection box is continuously supplied to the connection box by the amount of the insulation oil which decreases as the insulation oil of the connection box is impregnated into the connection box to maintain the state of the insulation oil in the connection box Characterized in that a connection box for insulating oil-impregnated cable is fed. 12. The method of claim 11,
Wherein the predetermined gas is introduced into the insulating oil supply unit to apply pressure to the insulating oil in the connection box while the connection oil is kept filled with the insulating oil. 11. The method of claim 10,
Wherein the predetermined gas is nitrogen (N2) gas. 11. The method of claim 10,
Wherein the pressure in the connection box is maintained even when the power supply is interrupted.

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