KR20180089837A - Apparatus and method for compaensating pressure of joint box - Google Patents

Abstract

The present invention relates to an intermediate connection box pressure compensation apparatus, an intermediate connection box pressure compensation system using the same, and an intermediate connection box pressure compensation method. According to the present invention, an insulation oil in a cable flows into an intermediate connection box having low pressure when a current flows in the cable to generate a cavity in an insulation layer of the cable, thereby preventing insulation breakdown of the cable.

Description

Technical Field [0001] The present invention relates to an intermediate connection box pressure compensating apparatus, an intermediate connection box pressure compensating system using the same, and an intermediate connection box pressure compensating apparatus,

The present invention relates to an intermediate junction box pressure compensating apparatus, an intermediate junction box pressure compensating system using the same, and an intermediate junction box compensating method.

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 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.

When the insulation-oil-impregnated cable is connected as described above, it is necessary to keep the pressure inside the cable and the junction box constant according to changes in the external environment such as seasonal changes.

In particular, when the power cable is energized or the outside temperature rises, the temperature of the power cable rises and the insulation oil in the intermediate cable connected to the power cable and the insulation oil in the power cable expands, The pressure of the insulating oil in the intermediate connection box is increased. In addition, when the power cable is not energized or the outside temperature falls, the temperature of the power cable is lowered and the insulating oil in the intermediate cable connected to the power cable and the insulating oil in the power cable shrinks, The pressure of the insulating oil in the cabinet is lowered.

However, since the temperature rise width of the cable in the high voltage cable is much larger than the falling width, the amount of the insulating oil moving from the cable to the intermediate connection port when the cable temperature rises is smaller than the amount of the insulating oil moving from the intermediate connection box to the cable The amount can be made larger. In other words, the flow rate of the insulation oil in the cable becomes larger than the inflow amount, and the insulation oil impregnated in the insulation layer of the cable flows out to the intermediate connection box, but is not introduced into the intermediate connection box as much as the insulation oil flowing out through the cable, And dielectric breakdown may occur in the cavity. Further, there is a possibility that a high level of internal pressure is applied to the intermediate connection box.

It is an object of the present invention to provide an intermediate connection port pressure compensating device capable of maintaining the pressure in the intermediate connection port within a predetermined range even when a cable is energized or an external temperature rises, an intermediate connection port pressure compensation system using the same, .

The pressure compensating device according to an embodiment of the present invention includes an intermediate connection chamber pressure compensator disposed between an intermediate connection chamber for connecting two cut insulation oil impregnated cables to each other and an insulation oil pressure tank, The pressure of the insulating oil impregnated cable or the intermediate connection box fluctuating with the temperature change of the insulating oil impregnated cable by flowing or blocking the insulating oil from the insulating oil pressure tank to the intermediate connection case or from the intermediate connection case to the insulating oil pressure tank Can be controlled to be within the predetermined pressure range.

In the present invention, when the pressure of the intermediate connection box rises and reaches the upper limit pressure value of the predetermined pressure range, the pressure compensation device opens the channel between the intermediate connection box and the insulating oil pressure tank, It is possible to prevent the pressure of the intermediate connection box from exceeding the upper limit pressure value by allowing the insulating oil to flow from the connection box to the insulating oil pressure tank.

In the present invention, the pressure compensation device may be configured such that, after the pipe is opened between the intermediate connection case and the insulating oil pressure tank, the insulating oil flows from the intermediate connection case to the insulating oil pressure tank, , The conduit can be shut off.

In the present invention, when the pressure in the intermediate connection box is lowered and the pressure in the intermediate connection box becomes smaller than the pressure in the insulating oil pressure tank, the pressure compensation device opens the pipe between the intermediate connection box and the pressure- So that the insulating oil flows from the insulating oil pressure tank to the intermediate connection box to prevent the pressure of the intermediate connection case from becoming lower than the lower limit pressure value of the predetermined pressure range.

In the present invention, the pressure compensation device is characterized in that after the pipe is opened between the intermediate connection case and the insulating oil pressure tank, the insulating oil flows from the insulating oil pressure tank to the intermediate connection case, If the pressure is equal to or greater than the pressure, the conduit can be shut off.

In the present invention, the pressure compensating device may include: a first valve that opens when the pressure of the intermediate connection box exceeds a preset pressure value, so that the insulating oil flows from the intermediate connection box to the insulating oil pressure tank; And a second valve that is opened to allow the insulating oil to flow from the insulating oil pressure tank to the intermediate connection box when the pressure of the intermediate connection box drops to become lower than the pressure of the insulating oil pressure tank; .

In the present invention, in the first valve, when the insulating oil impregnated cable is energized, the insulating oil expands due to the temperature rise of the insulating oil, so that the pressure in the intermediate connection chamber rises, , The insulating oil flows into the insulating oil pressure tank which maintains a pressure lower than the preset pressure value in the intermediate connection box, and the pressure of the intermediate connection box after the flow of the insulating oil flows The first valve may be closed so that the insulating oil does not flow from the intermediate junction box to the insulating oil pressure tank.

In the present invention, the first valve may be a relief valve.

In the present invention, the second valve is opened when the pressure in the intermediate connection box is lowered due to the cooling and contraction of the insulating oil, and when the pressure of the intermediate connection box becomes smaller than the pressure of the insulating oil pressure tank, When the pressure of the intermediate connection port becomes equal to or greater than the pressure of the insulating oil pressure tank after the flow of the insulating oil, the second valve is closed, The insulating oil may not flow from the pressure tank to the intermediate connection box.

In the present invention, the second valve may be a check valve.

An intermediate junction box pressure compensating system according to an embodiment of the present invention is a pressure compensating system for an intermediate junction box for connecting two cut insulating oil impregnated cables, comprising: an insulating oil pressure tank for accommodating insulating oil; A first valve that is opened to allow the insulating oil to flow from the intermediate junction box to the insulating oil pressure tank when the pressure of the intermediate junction box exceeds a preset pressure value; And a second valve that is opened to allow the insulating oil to flow from the insulating oil pressure tank to the intermediate connection box when the pressure of the intermediate connection box drops to become lower than the pressure of the insulating oil pressure tank; .

In the present invention, in the first valve, when the insulating oil impregnated cable is energized, the insulating oil expands due to the temperature rise of the insulating oil, so that the pressure in the intermediate connection chamber rises, , The insulating oil flows into the insulating oil pressure tank which maintains a pressure lower than the preset pressure value in the intermediate connection box, and the pressure of the intermediate connection box after the flow of the insulating oil flows The first valve may be closed so that the insulating oil does not flow from the intermediate junction box to the insulating oil pressure tank.

In the present invention, the first valve may be a relief valve.

In the present invention, the second valve is opened when the pressure in the intermediate connection box is lowered due to the cooling and contraction of the insulating oil, and when the pressure of the intermediate connection box becomes smaller than the pressure of the insulating oil pressure tank, When the pressure of the intermediate connection port becomes equal to or greater than the pressure of the insulating oil pressure tank after the flow of the insulating oil, the second valve is closed, The insulating oil may not flow from the pressure tank to the intermediate connection box.

In the present invention, the second valve may be a check valve.

A method of compensating an intermediate connection box pressure according to an embodiment of the present invention is a method of compensating the pressure of the intermediate connection box by filling an intermediate connection box connected to an insulating oil pressure tank and connecting two cutaway insulating oil impregnated cables with insulating oil Wherein when the pressure of the intermediate connection box exceeds a predetermined pressure value, a first valve disposed between the intermediate connection box and the insulation oil pressure tank is opened so that the insulation oil flows from the intermediate connection box to the insulation oil pressure tank step; Closing the first valve when the insulation oil flows from the intermediate junction box to the insulating oil pressure tank so that the pressure of the intermediate junction box becomes less than the predetermined pressure value; The second valve disposed between the intermediate connection box and the oil pressure tank is opened so that the insulating oil is discharged from the oil pressure tank to the intermediate connection box when the pressure of the intermediate connection box is lowered to become smaller than the pressure of the oil pressure tank. Flowing; And closing the second valve when the insulating oil flows from the insulating oil pressure tank to the intermediate connection box so that the pressure of the intermediate connection box becomes equal to or greater than the pressure of the insulating oil pressure tank; .

In the present invention, in the first valve, when the insulating oil impregnated cable is energized, the insulating oil expands due to the temperature rise of the insulating oil, so that the pressure in the intermediate connection chamber rises, , The insulating oil flows into the insulating oil pressure tank which maintains a pressure lower than the preset pressure value in the intermediate connection box, and the pressure of the intermediate connection box after the flow of the insulating oil flows The first valve may be closed so that the insulating oil does not flow from the intermediate junction box to the insulating oil pressure tank.

In the present invention, the first valve may be a relief valve.

In the present invention, the second valve is opened when the pressure in the intermediate connection box is lowered due to the cooling and contraction of the insulating oil, and when the pressure of the intermediate connection box becomes smaller than the pressure of the insulating oil pressure tank, When the pressure of the intermediate connection port becomes equal to or greater than the pressure of the insulating oil pressure tank after the flow of the insulating oil, the second valve is closed, The insulating oil may not flow from the pressure tank to the intermediate connection box.

In the present invention, the second valve may be a check valve.

According to the present invention, by maintaining the pressure within the cable within a certain range, the pressure difference between the cable and the pressure in the insulating oil pressure tank causes the insulating oil in the cable to flow to the insulating oil pressure tank, causing a cavity in the insulating layer of the cable, .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cutaway perspective view showing a constitution of an insulating oil impregnated cable. FIG.
2 is a schematic diagram illustrating an intermediate splice pressure compensation system having an intermediate splice pressure compensation device and an intermediate splice in accordance with an embodiment of the present invention.
3 is a diagram showing an embodiment of an intermediate junction box pressure compensating apparatus.
4 is a flowchart illustrating an intermediate junction box pressure compensation method 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 is a schematic diagram illustrating an intermediate splice pressure compensation system 1000 having an intermediate splice pressure compensation device 1100 and an intermediate splice 200 according to an embodiment of the present invention. In FIG. 2, a part is cut out to show the internal configuration of the intermediate connection box 200, and the internal configuration is shown.

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 1P 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 1P 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 1P and the insulation layer 14A located at the innermost side of the insulation layer 14 of the cable 100 surrounds 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 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, 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 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 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.

An intermediate junction box pressure compensating system 1000 according to an embodiment of the present invention includes an insulating oil pressure tank 1200 in which the insulating oil is accommodated to fill the insulating oil in the intermediate junction box 200 having the above structure, An intermediate connection port pressure compensating device 1100 disposed between the pressure tank 1200 and the intermediate connection port 200 and a connection port for connecting the insulation oil pressure tank 1200 and the intermediate connection port pressure compensating device 1100, And a third conduit 1330 connecting the intermediate connection box pressure compensator 1100 and the intermediate connection box 200 to provide a passage for the insulating oil .

The insulating oil pressure tank 1200 may receive the insulating oil. The insulation oil may be the same as the insulation oil filled in the cable and the intermediate connection box 200 and the first, second and third pipes 1310 and 1320 connecting the insulation oil pressure tank 1200 and the intermediate connection box 200, 1320 and 1330 to flow between the insulating oil pressure tank 1200 and the intermediate connection box 200. [

The insulating oil may flow to the insulating oil pressure tank 1200 or to the intermediate junction box 200 by the pressure difference in the insulating oil pressure tank 1200 and the intermediate connection box 200. Specifically, the insulating oil pressure tank 1200 can maintain a constant pressure. However, as the temperature of the cable connected to the intermediate connection box 200 is increased, the insulation oil in the cable is expanded, so that the pressure in the intermediate connection box 200 also increases. When the pressure in the intermediate connection box 200 is larger than the pressure in the insulation oil pressure tank 1200, the pressure difference causes the oil to move from the intermediate connection box 200 to the insulation oil pressure tank 1200, When the pressure in the container 200 becomes smaller than the pressure in the insulating oil pressure tank 1200, the pressure difference causes the oil to move from the insulating oil pressure tank 1200 to the intermediate connection case 200.

The insulating oil accommodated in the insulating oil pressure tank 1200 flows from the insulating oil pressure tank 1200 to the insulating oil pressure tank 1200 or to the intermediate connection box 200 by a pressure difference in the intermediate connection box 200, . For example, when the power cable 100 is energized, as the temperature of the cable connected to the intermediate connection box 200 rises, the insulation oil filled in the intermediate connection box 200 expands and the insulation oil in the cable expands The pressure in the intermediate connection box 200 also increases, and when the pressure is excessively increased, the cable insulation layer may be deformed. When the pressure in the intermediate connection box 200 is greater than the pressure in the insulation oil pressure tank 1200, the pressure difference causes the oil to move from the intermediate connection box 200 to the insulation oil pressure tank 1200 , When the pressure in the intermediate connection case 200 becomes smaller than the pressure in the insulation oil pressure tank 1200, the oil pressure shifts the insulating oil from the insulation oil pressure tank 1200 to the intermediate connection case 200.

The insulating oil accommodated in the insulating oil pressure tank 1200 flows into the insulating oil pressure tank 1200 or into the intermediate connecting box 200 due to the pressure difference in the insulating oil pressure tank 1200 and the pressure difference in the intermediate connection box 200 . However, the insulating oil pressure tank 1200 may include a pressure buffering member to maintain a constant pressure. As the temperature of the cable connected to the intermediate connection box 200 is increased, the insulation oil in the cable is expanded, so that the pressure in the intermediate connection box 200 also increases. When the pressure in the intermediate connection box 200 is larger than the pressure in the insulation oil pressure tank 1200, the pressure difference causes the oil to move from the intermediate connection box 200 to the insulation oil pressure tank 1200, When the pressure in the container 200 becomes smaller than the pressure in the insulating oil pressure tank 1200, the pressure difference causes the oil to move from the insulating oil pressure tank 1200 to the intermediate connection case 200.

However, when the cable is energized, particularly when a high voltage is applied, the temperature of the cable rises to a very high temperature, so that the pressure in the intermediate junction box 200 can rise to several tens to several hundreds of bar or more. As the temperature of the cable connected to the intermediate connection box 200 increases, the insulation oil filled in the intermediate connection box 200 expands and the insulation oil in the cable expands and flows into the intermediate connection box 200. Therefore, If the pressure is excessively increased, a problem such as deformation of the cable insulation layer may occur.

On the other hand, when the temperature of the cable is lowered due to an external environmental factor or interruption of power supply, the pressure in the intermediate connection box 200 may be lower than a certain level or may be partially negative pressure. The amount of the insulating oil moving from the intermediate junction box 200 to the insulating oil pressure tank 1200 when the cable temperature rises is larger than the temperature rising width of the cable in the high voltage cable because the temperature rise width of the cable is much larger than the temperature falling width of the cable. The amount of the insulating oil moving from the intermediate connection box 200 to the intermediate connection box 200 can be made larger. That is, the amount of the insulating oil in the cable becomes larger than the inflow amount, and the insulating oil impregnated in the insulating layer of the cable flows out to the insulating oil pressure tank 1200, but does not flow into the middle connecting box 200 due to the discharged insulating oil, A cavity may be formed in the insulating layer of the layer, and dielectric breakdown may occur in the cavity.

In another embodiment of the present invention, an intermediate connection pressure compensating device 1100 is disposed between the intermediate connection case 200 and the insulating oil pressure tank 1200, and the intermediate connection case pressure compensating device 1100 includes an intermediate connection case 200 and the insulating oil pressure tank 1200, it is possible to prevent the excessive flow of the insulating oil and to prevent the cavity from being generated in the insulating layer of the cable.

More specifically, the pressure compensating device 1100 may block or allow the flow of the insulating oil between the insulating oil pressure tank 1200 and the intermediate connection box 200, thereby varying the temperature of the insulating oil- It is possible to control the pressure of the insulating oil-impregnated cable or the intermediate connection box 200 to be within a predetermined pressure range. That is, in the pressure compensating device 1100, when the temperature of the cable rises due to the energization of the cable or the external environment, the insulation oil in the cable expands and the pressure of the intermediate connection box 200 rises and the pressure of the intermediate connection box 200 When the upper limit pressure value of the predetermined pressure range is reached, the first conduit 1310 between the intermediate junction box 200 and the insulating oil pressure tank 1200 can be opened. The insulating oil may flow along the opened first conduit 1310 to the insulating oil pressure tank 1200 from the intermediate connection box 200 where the pressure is relatively higher and the pressure of the intermediate connection box 200 Can be lowered.

The pressure compensating device 1100 may be installed in the intermediate connection box 200 after opening the first conduit 1310 between the intermediate connection box 200 and the insulating oil pressure tank 1200, The first conduit 1310 can be shut off when the insulation oil flows and the pressure of the intermediate connection box 200 becomes less than the upper limit pressure value.

 Accordingly, the present invention can prevent the pressure of the intermediate connection box 200 from rising beyond the upper limit pressure value. When the pressure of the intermediate connection box 200 is lower than the upper limit pressure value, the first conduit 1310 is closed to block the flow of the insulation oil. In the intermediate connection box 200, It is possible to prevent the leakage of the insulating oil. That is, according to the present invention, when the pressure of the intermediate connection box 200 is less than the upper limit pressure value, the first conduit 1310 can be closed to prevent the leakage of the oil from the intermediate connection box 200 to the insulation oil pressure tank 1200, When the pressure of the intermediate connection box 200 exceeds the upper limit pressure value, the first conduit 1310 is opened to prevent the pressure in the intermediate connection box 200 from exceeding the upper limit pressure value .

Also, the pressure compensating device 1100 is configured such that the temperature of the cable is lowered due to the cable disconnection or the external environment, the oil in the cable is contracted to lower the pressure of the intermediate connection box 200, The second conduit 1320 between the intermediate connection box 200 and the insulating oil pressure tank 1200 can be opened. The insulating oil may flow along the second open channel 1320 to the intermediate junction box 200 from a relatively higher pressure oil pressure tank 1200 and the pressure of the intermediate junction box 200 may be increased . Accordingly, the present invention can prevent the pressure of the intermediate connection box 200 from falling below the pressure of the insulation oil pressure tank 1200. [

The pressure compensating device 1100 may open the second channel 1320 between the intermediate connection box 200 and the insulating oil pressure tank 1200 and then open the intermediate connection box 200 from the insulating oil pressure tank 1200 to the intermediate connection box 200. [ When the insulating oil flows and the pressure of the intermediate connection box 200 is equal to or greater than the pressure of the insulating oil pressure tank 1200, the second conduit 1320 can be shut off.

Accordingly, the present invention can prevent the pressure of the intermediate connection box 200 from falling below the pressure of the insulation oil pressure tank 1200. [ When the pressure of the intermediate connection box 200 is greater than the pressure of the insulation oil pressure tank 1200, the second conduit 1320 is closed to block the flow of the insulation oil, It is possible to prevent the insulating oil from flowing out to the insulating oil pressure tank 1200. That is, in the present invention, when the pressure of the intermediate connection box 200 is greater than the pressure of the insulation oil pressure tank 1200, the second conduit 1320 is closed so that the connection from the intermediate connection box 200 to the insulation oil pressure tank 1200 When the pressure of the intermediate connection box 200 drops below the pressure of the insulation oil pressure tank 1200, the pressure in the intermediate connection box 200 is increased by opening the second conduit 1320, It is possible to prevent the pressure of the oil pressure tank 1200 from dropping below the pressure of the oil pressure tank 1200.

3 is a diagram illustrating an intermediate junction box pressure compensating apparatus 1100 according to an embodiment of the present invention.

Referring to FIG. 3, an intermediate joint chamber pressure compensating apparatus 1100 according to an embodiment of the present invention may include a first valve 1110 and a second valve 1120. The first valve 1110 is opened when the pressure of the intermediate connection box 200 exceeds a preset pressure value so that the insulating oil flows from the intermediate connection box 200 to the insulating oil pressure tank 1200 can do. The second valve 1120 is opened when the pressure of the intermediate connection box 200 is lowered to be lower than the pressure of the insulation oil pressure tank 1200 so that the intermediate connection box 200 To allow the insulating oil to flow.

In the first valve 1110, the temperature of the insulating oil in the cable rises due to the energization of the insulating oil-impregnated cable or a change in the external environment, thereby expanding the insulating oil, The intermediate connection box 200 is opened when the pressure in the intermediate connection box 200 is higher than the predetermined pressure value due to an increase in the pressure in the intermediate connection box 200, The insulating oil may flow into the tank 1200.

When the pressure of the intermediate connection box 200 becomes lower than the predetermined pressure value after the insulating oil flows into the insulating oil pressure tank 1200, the first valve 1110 is closed and the intermediate connection box 200 is closed The insulating oil may not flow into the insulating oil pressure tank 1200.

That is, the first valve 1110 is generally closed, and may be opened when the pressure of the intermediate connection box 200 becomes equal to or higher than a preset pressure at the first valve 1110. The first valve 1110 may be, for example, a relief valve.

The second valve 1120 may be configured such that the insulation oil in the cable is cooled and contracted due to a short circuit of the cable or a change of the external environment so that the pressure in the intermediate connection box 200 is lowered, Is opened when the pressure of the insulating oil is lower than the pressure of the pressure oil tank (1200), the insulating oil flows from the insulating oil pressure tank (1200) maintaining a constant pressure to the intermediate connection box (200) The second valve 1120 is closed to prevent the intermediate connection box 200 from being opened in the insulating oil pressure tank 1200 when the pressure of the intermediate connection box 200 becomes equal to or greater than the pressure of the insulating oil pressure tank 1200. [ ), The insulating oil may not flow.

That is, the second valve 1120 is disposed between the intermediate connection box 200 and the insulation oil pressure tank 1200 and is generally closed, but the pressure in the intermediate connection box 200 can be variably set to a substantially constant pressure When the pressure of the oil pressure tank 1200 is lowered. When the second valve 1120 is opened, the insulating oil may flow from the insulating oil pressure tank 1200 to the intermediate junction box 200, the pressure of which is higher than the pressure of the second valve 1120. The insulating oil is discharged from the intermediate connection box 200 through the insulating oil pressure tank 1200 through the second valve 1120 opened by the pressure difference between the intermediate connection box 200 and the insulating oil pressure tank 1200, The pressure of the intermediate connection box 200 and the pressure of the insulating oil pressure tank 1200 becomes equal or the temperature of the cable 100 rises due to external factors such as energization of the cable 100, The second valve 1120 is closed when the temperature of the insulating oil in the cabinet 200 or the cable 100 rises and the pressure rises and the temperature of the oil in the cabinet 200 or the oil pressure tank 1200 The oil does not flow. The second valve may be, for example, a check valve.

4 is a flowchart illustrating an intermediate junction box pressure compensation method according to an embodiment of the present invention.

Referring to FIG. 4, the intermediate junction box pressure compensating method according to an embodiment of the present invention first includes the steps of, when the pressure of the intermediate junction box 200 exceeds a predetermined pressure value of the first valve 1110, The first valve 1110 disposed between the insulating oil pressure tank 1200 and the insulating oil pressure tank 1200 is opened to allow the insulating oil to flow from the intermediate connection box 200 to the insulating oil pressure tank 1200 S101).

The temperature of the dielectric oil in the cable rises due to the energization of the dielectric-oil-impregnated cable or a change in the external environment, the dielectric oil expands and the pressure in the intermediate connection box 200 rises, The first valve 1110 is opened when the pressure exceeds a preset pressure value of the first valve 1110 and the pressure difference between the intermediate connection box 200 and the insulating oil pressure tank 1200 The insulating oil may flow from the intermediate junction box 200 to the insulating oil pressure tank 1200.

The first valve 1110 is opened so that the insulating oil flows from the intermediate connection box 200 to the insulating oil pressure tank 1200 and then the pressure of the intermediate connection box 200 becomes less than the preset pressure value , The first valve 1110 is closed (S102).

As described above, after the first valve 1110 is opened, the oil may flow into the insulating oil pressure tank 1200 having a lower pressure in the intermediate connection box 200 having a higher pressure.

After the first valve 1110 is opened, the intermediate connection box 200 through which the insulating oil flows out is continuously lowered in pressure. However, the insulating oil pressure tank 1200 maintains a constant pressure even when the insulating oil flows. When the pressure in the outflow of the insulating oil is lowered and the pressure reaches the pressure for opening the first valve 1110, that is, the pre-set pressure value, the first valve 1110 And the flow of the insulating oil between the intermediate connection box 200 and the insulating oil pressure tank 1200 may be interrupted.

A second valve 1120 disposed between the intermediate connection case 200 and the insulating oil pressure tank 1200 when the pressure of the intermediate connection case 200 is lowered to be smaller than the pressure of the insulating oil pressure tank 1200, Is opened to allow the insulating oil to flow from the insulating oil pressure tank 1200 to the intermediate connection box 200 (S103).

Specifically, when the temperature of the dielectric oil in the cable is lowered due to a break in the cable or a change in the external environment, the dielectric oil shrinks and the pressure of the cable and the intermediate connection box 200 is lowered. The second valve 1120 may be opened when the pressure in the intermediate connection box 200 is lowered and the pressure of the intermediate connection box 200 is lower than the pressure of the insulation oil pressure tank 1200. The pressure difference may cause the insulating oil to flow from the insulating oil pressure tank 1200 to the intermediate junction box 200.

The second valve 1120 is opened so that the insulating oil flows from the insulating oil pressure tank 1200 to the intermediate connection case 200 and then the pressure of the intermediate connection case 200 is applied to the insulating oil pressure tank 1200, The second valve 1120 is closed (S104).

As described above, after the second valve 1120 is opened, the insulating oil can flow from the insulating oil pressure tank 1200 having a higher pressure to the intermediate junction box 200, The pressure of the connection box 200 is increased. However, the insulating oil pressure tank 1200 maintains a constant pressure even when the insulating oil flows. The second valve 1120 is closed when the pressure of the intermediate connection box 200 increases due to the inflow of the insulating oil and becomes equal to or greater than the pressure of the insulating oil pressure tank 1200, The flow of the insulating oil between the box 200 and the insulating oil pressure tank 1200 may be interrupted.

According to an embodiment of the present invention, when the pressure of the intermediate connection box 200 exceeds the preset pressure value, the first valve 1110 is opened and the intermediate connection box 200 is opened It is possible to prevent the pressure of the intermediate connection box 200 from being increased by flowing the insulating oil into the insulation oil pressure tank 1200. When the pressure of the intermediate connection box 200 is lower than the pressure of the insulation oil pressure tank 1200 The second valve 1120 is opened and the insulating oil flows from the insulating oil pressure tank 1200 to the intermediate connection case 200 to prevent the pressure of the intermediate connection case 200 from being very low . The first valve 1110 and the second valve 1120 are connected to each other by a pressure of the intermediate connection box 200 between the predetermined pressure value of the first valve 1110 and the pressure of the insulation oil pressure tank 1200, The insulating oil impregnated in the insulating layer of the cable connected to the intermediate connection box 200 flows out to generate a cavity and thereby breakage of the insulation. .

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
100 .. Power cable
200 .. Middle connection
210. Insulation reinforcement layer
220 .. insulating oil
1100 .. Pressure compensation device
1200 .. insulation oil pressure tank

Claims (20)

An intermediate connection box pressure compensating device arranged between an intermediate connection box connecting two cutaway insulating oil impregnated cables to each other and an insulating oil pressure tank,
Wherein the pressure compensating device comprises:
The pressure of the insulating oil impregnated cable or the intermediate connection box fluctuating with the temperature change of the insulating oil impregnated cable by flowing or blocking the insulating oil from the insulating oil pressure tank to the intermediate connection case or from the intermediate connection case to the insulating oil pressure tank Is within a predetermined pressure range. The method according to claim 1,
Wherein the pressure compensating device comprises:
When the pressure of the intermediate connection box rises and reaches the upper limit pressure value of the predetermined pressure range, the pipe between the intermediate connection box and the insulation oil pressure tank is opened to transfer the insulating oil from the intermediate connection box to the insulation oil pressure tank Thereby preventing the pressure of the intermediate connection box from exceeding the upper limit pressure value. 3. The method of claim 2,
Wherein the pressure compensating device comprises:
When the pressure of the intermediate connection box becomes lower than the upper limit value by flowing the insulating oil from the intermediate connection case to the insulating oil pressure tank after opening the pipe between the intermediate connection case and the insulating oil pressure tank, Wherein the intermediate connection chamber pressure compensating device comprises: The method according to claim 1,
Wherein the pressure compensating device comprises:
When the pressure of the intermediate connection box is lowered and the pressure of the intermediate connection box becomes smaller than the pressure in the insulating oil pressure tank, the channel between the intermediate connection box and the insulation oil pressure tank is opened, So as to prevent the pressure of the intermediate connection box from becoming lower than the lower limit pressure value of the predetermined pressure range. 5. The method of claim 4,
Wherein the pressure compensating device comprises:
When the insulation oil flows from the insulation oil pressure tank to the intermediate connection box after opening the pipe between the intermediate connection box and the insulation oil pressure tank so that the pressure of the intermediate connection box is equal to or greater than the pressure in the insulation oil pressure tank, Wherein said intermediate connection box pressure compensating device comprises: The method according to claim 1,
Wherein the pressure compensating device comprises:
A first valve that is opened to allow the insulating oil to flow from the intermediate junction box to the insulating oil pressure tank when the pressure of the intermediate junction box exceeds a preset pressure value; And
A second valve that is opened to allow the insulating oil to flow from the insulating oil pressure tank to the intermediate connection box when the pressure of the intermediate connection box drops and becomes smaller than the pressure of the insulating oil pressure tank; And an intermediate connection box pressure compensating device for compressing the intermediate connection box. The method according to claim 6,
Wherein the first valve is configured such that when the insulating oil is inflated by the temperature rise of the insulating oil at the time of energization of the insulating oil impregnated cable, the pressure in the intermediate connection box rises and the pressure in the intermediate connection box exceeds the preset pressure value The insulating oil flows into the insulating oil pressure tank which maintains a pressure lower than the preset pressure value in the intermediate connection box,
Wherein when the pressure of the intermediate connection box is lower than the preset pressure value after the flow of the insulating oil, the first valve is closed so that the insulating oil does not flow from the intermediate connection box to the insulating oil pressure tank. Pressure compensation device. The method according to claim 6,
Wherein the first valve is a relief valve. The method according to claim 6,
Wherein the second valve is opened when the pressure in the intermediate connection box is lowered due to the cooling and contraction of the insulating oil so that the pressure of the intermediate connection box becomes smaller than the pressure of the insulating oil pressure tank, The insulating oil flows from the tank to the intermediate connection box,
Wherein when the pressure of the intermediate connection box after the flow of the insulating oil becomes equal to or greater than the pressure of the insulating oil pressure tank, the second valve is closed so that the insulating oil does not flow from the insulating oil pressure tank to the intermediate connection box. Intermediate connection box pressure compensation device. The method according to claim 6,
And the second valve is a check valve. A pressure compensation system for an intermediate junction box connecting two cutaway insulating oil impregnated cables,
An insulating oil pressure tank for containing the insulating oil;
A first valve that is opened to allow the insulating oil to flow from the intermediate junction box to the insulating oil pressure tank when the pressure of the intermediate junction box exceeds a preset pressure value; And
A second valve that is opened to allow the insulating oil to flow from the insulating oil pressure tank to the intermediate connection box when the pressure of the intermediate connection box drops and becomes smaller than the pressure of the insulating oil pressure tank; And an intermediate junction box pressure compensating system. 12. The method of claim 11,
Wherein the first valve is configured such that when the insulating oil is inflated by the temperature rise of the insulating oil at the time of energization of the insulating oil impregnated cable, the pressure in the intermediate connection box rises and the pressure in the intermediate connection box exceeds the preset pressure value The insulating oil flows into the insulating oil pressure tank which maintains a pressure lower than the preset pressure value in the intermediate connection box,
Wherein when the pressure of the intermediate connection box is lower than the preset pressure value after the flow of the insulating oil, the first valve is closed so that the insulating oil does not flow from the intermediate connection box to the insulating oil pressure tank. Pressure compensation system. 12. The method of claim 11,
Wherein the first valve is a relief valve. 12. The method of claim 11,
Wherein the second valve is opened when the pressure in the intermediate connection box is lowered due to the cooling and contraction of the insulating oil so that the pressure of the intermediate connection box becomes smaller than the pressure of the insulating oil pressure tank, The insulating oil flows from the tank to the intermediate connection box,
Wherein when the pressure of the intermediate connection box after the flow of the insulating oil becomes equal to or greater than the pressure of the insulating oil pressure tank, the second valve is closed so that the insulating oil does not flow from the insulating oil pressure tank to the intermediate connection box. Medium junction box pressure compensation system. 12. The method of claim 11,
And the second valve is a check valve. A method for compensating a pressure of an intermediate connection box connected to an insulation oil pressure tank and filling an intermediate connection box connecting two cutaway insulating oil impregnated cables with insulating oil,
A first valve disposed between the intermediate junction box and the insulation oil pressure tank is opened to flow the insulation oil from the intermediate junction box to the insulation oil pressure tank when the pressure of the intermediate connection box exceeds a preset pressure value;
Closing the first valve when the insulation oil flows from the intermediate junction box to the insulating oil pressure tank so that the pressure of the intermediate junction box becomes less than the predetermined pressure value;
The second valve disposed between the intermediate connection box and the oil pressure tank is opened so that the oil in the intermediate connection box is discharged from the oil pressure tank to the intermediate connection box when the pressure of the intermediate connection box is lowered to become smaller than the pressure of the oil pressure tank. Flowing; And
Closing the second valve when the insulating oil flows from the insulating oil pressure tank to the intermediate connection box so that the pressure of the intermediate connection box becomes equal to or greater than the pressure of the insulating oil pressure tank; Wherein the intermediate connection box pressure compensation method comprises the steps of: 17. The method of claim 16,
Wherein the first valve is configured such that when the insulating oil is inflated by the temperature rise of the insulating oil at the time of energization of the insulating oil impregnated cable, the pressure in the intermediate connection box rises and the pressure in the intermediate connection box exceeds the preset pressure value The insulating oil flows into the insulating oil pressure tank which maintains a pressure lower than the preset pressure value in the intermediate connection box,
Wherein when the pressure of the intermediate connection box is lower than the preset pressure value after the flow of the insulating oil, the first valve is closed so that the insulating oil does not flow from the intermediate connection box to the insulating oil pressure tank. Pressure compensation method. 17. The method of claim 16,
Wherein the first valve is a relief valve. 17. The method of claim 16,
Wherein the second valve is opened when the pressure in the intermediate connection box is lowered due to the cooling and contraction of the insulating oil so that the pressure of the intermediate connection box becomes smaller than the pressure of the insulating oil pressure tank, The insulating oil flows from the tank to the intermediate connection box,
Wherein when the pressure of the intermediate connection box after the flow of the insulating oil becomes equal to or greater than the pressure of the insulating oil pressure tank, the second valve is closed so that the insulating oil does not flow from the insulating oil pressure tank to the intermediate connection box. Intermediate connection box pressure compensation method. 17. The method of claim 16,
And the second valve is a check valve.

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