KR20200090378A - Pressure compensating device for joint box of power cable and jointing system of power cable having the same - Google Patents

Abstract

The present invention relates to an intermediate joint box pressure compensating device of a ground-insulated power cable impregnated with insulating oil, whose pipes and equipment are simplified, size becomes small, separate maintenance is minimized, and enables damage to an insulation layer of an intermediate joint box to be prevented; and a power cable intermediate joint system having the same. The intermediate joint box pressure compensating device of a power cable comprises a pressure compensating unit and a pressure controlling unit.

Description

PRESSURE COMPENSATING DEVICE FOR JOINT BOX OF POWER CABLE AND JOINTING SYSTEM OF POWER CABLE HAVING THE SAME

The present invention relates to an intermediate junction box pressure compensator for a power cable and a power cable intermediate junction system having the same. In more detail, the present invention simplifies piping and equipment, miniaturizes the size, minimizes separate maintenance, and compensates the pressure of the intermediate junction box of the insulating oil impregnated paper insulation power cable that can prevent damage to the insulating layer of the intermediate junction box. It relates to an apparatus and a power cable intermediate connection system having the same.

Power cable means a cable for supplying electric power through a conductive conductor. It is very important to insulate the conductor of the power cable, and for this purpose, to insulate the conductor, wrap an insulating layer or insulating paper made of XLPE (Cross-linked Polyethylene) material, and insulate the impregnated insulating oil to reinforce the dielectric strength. A layer or the like is applied to the conductor side.

Among these, insulation oil-impregnated ground insulation cables can be classified into OF power cables and MI power cables. OF power cables, which have been widely used in the past, have a structure in which insulating oil flows continuously between the cable and the intermediate junction box, but the use of OF power cables is decreasing due to the use of insulating oil and the problems of fire or recent environmental pollution.

On the other hand, MI power cables use high-viscosity insulating oil, but since the oil usage can be reduced by adopting a structure in which the insulating oil does not flow in the system, research and distribution of MI power cables have recently been expanded.

In the MI power cable, the pressure inside the intermediate junction box may be increased due to the expansion of the volume of insulating oil contained in the junction box when the system is driven.

Therefore, the MI power cable may also be provided with an insulating oil buffer or a pressure compensator for buffering the internal pressure, such as an intermediate junction box, and the insulating oil buffer or pressure compensator is configured to include an insulating oil container and the like. It may be configured in such a way as to absorb insulating oil from the junction box or supply insulating oil to the junction box according to the internal pressure of the junction box or the like. The MI oil power cable also has an insulated oil shock absorber added to the intermediate junction box, which can be made smaller in size than the OF oil cable's insulation oil shock absorber.

In addition, in relation to the pressure compensation device for the intermediate junction box of an insulating oil impregnated power insulating cable previously introduced, a technique of adjusting the internal pressure of the insulating oil accommodated in the insulating oil container or the like by applying a gas injection method from the outside was introduced, but the internal pressure of the insulating oil container In order to increase the pressure, the injected gas was dissolved in insulating oil and introduced into the intermediate junction box, thereby damaging, deforming or destroying the insulating layer, thereby impairing the insulating performance.

The present invention simplifies piping and equipment, miniaturizes the size, minimizes separate maintenance, and prevents damage to the insulating layer of the intermediate junction box. It is an object to solve the problem of providing an intermediate power cable connection system.

In order to solve the above problems, the present invention provides a pressure compensation device for an intermediate junction box of a power cable that is connected to an intermediate junction box for intermediate connection of an insulating oil-impregnated power cable to regulate the pressure inside the intermediate junction box. It is provided with at least one volume variable chamber and the housing for receiving the variable volume chamber, and the insulating oil is filled in the state in which the variable volume chamber is accommodated, and the insulating oil is interposed between the intermediate junction boxes according to the pressure inside the intermediate junction box. A pressure compensation unit that flows and is mounted around the intermediate junction box; And a pressure control unit provided between the intermediate junction box and the pressure compensating unit to flow insulating oil or block the flow of insulating oil to control the internal pressure of the intermediate junction box to be within a predetermined range. It is possible to provide an intermediate junction box pressure compensation device.

In addition, the volume-variable chamber may have a corrugated tube structure capable of expansion or contraction depending on the pressure in the pressure compensation unit.

In addition, the housing constituting the pressure compensation unit may be mounted to wrap the outer peripheral surface of the protective copper tube constituting the intermediate junction box in a ring shape.

Here, the volume variable chamber provided in the pressure compensation unit may be configured to contract or expand in the longitudinal direction of the intermediate junction box.

In this case, the volume variable chamber may be provided in a ring shape in the housing of the pressure compensation unit.

And, the pressure control unit is provided in the vicinity of the side of the pressure compensation unit, the pressure control unit is provided with an insulating oil channel for communicating the pressure compensation unit and the inside of the protective copper tube of the intermediate junction box,

The pressure control unit may be connected to the pressure compensation unit and an insulating oil conduit in the longitudinal direction of the cable, and the pressure control unit may be connected to an insulating oil conduit in the radial direction of the intermediate junction box and the intermediate junction box.

In addition, when the internal pressure of the intermediate junction box exceeds a predetermined upper pressure limit, the pressure control unit opens an insulating oil passage between the intermediate junction box and the pressure compensation unit to the pressure compensation unit in the intermediate junction box. The insulating oil can flow.

And, the pressure control unit, the internal pressure of the intermediate junction box exceeds a predetermined upper pressure limit, after opening the insulating oil pipe between the intermediate junction box and the pressure compensation unit, the internal pressure of the intermediate junction box is less than the upper pressure limit value When reduced, the insulating oil pipeline may be blocked.

Here, the pressure control unit is provided with an insulating oil pipeline connecting and connecting the pressure compensation unit and the intermediate junction box,

The insulating oil conduit in the pressure control unit is branched from the pressure control unit to the first conduit and the second conduit,

When the internal pressure of the intermediate junction box exceeds a predetermined upper pressure limit, the pressure control unit is opened and a first control unit installed in the first conduit to allow insulating oil to flow from the intermediate junction box to the pressure compensation unit. ; And a second control unit installed in the second conduit to allow the flow of insulating oil in one direction from the pressure compensation unit to the intermediate junction box.

In this case, when the first control unit is opened, when insulating oil flows from the intermediate junction box to the pressure compensation unit, and after the insulating oil flows, the internal pressure of the intermediate junction box becomes lower than the upper limit of the pressure. The first control unit is cut off and the insulating oil may not flow from the intermediate junction box to the pressure compensation unit.

In addition, the first control unit may be a relief valve.

In addition, when the internal pressure of the intermediate junction box is less than the pressure of the pressure compensation unit, the second control from the pressure compensation unit to the intermediate junction box until the point where the internal pressure balance between the intermediate junction box and the pressure compensation unit is formed The insulating oil can flow through the unit.

In addition, the second control unit may be a check connector.

Here, the intermediate junction box is 50 liter (l) to 90 liter (l) of insulating oil is initially accommodated, the upper pressure limit may be a value in the range of 15bar to 25bar.

In this case, the pressure compensating unit may initially receive insulating oil of 60% or less of the maximum insulating oil capacity.

In addition, the upper limit of the pressure, which is the initial setting pressure of the first control unit, may be greater than the initial setting pressure of the pressure compensation unit.

In addition, in order to solve the above problems, the present invention is an electric power cable intermediate connection system for intermediately connecting an insulating oil-impregnated power cable, the pair of power cables being intermediately connected and the intermediate junction box filled with insulating oil; It is possible to provide a power cable intermediate connection system including the above-described intermediate junction box pressure compensator.

According to the intermediate junction box pressure compensator of the insulating oil impregnated ground insulating power cable according to the present invention and the power cable intermediate junction system having the same, the piping and equipment of the intermediate junction box pressure compensator can be simplified and reduced in size.

In addition, according to the intermediate oil junction box pressure compensator of the insulating oil impregnated ground insulating power cable according to the present invention and the power cable intermediate connecting system having the same, the gas is not used in the insulating oil because the method of injecting gas is not used to form the pressure of the insulating oil. Damage to the insulating layer of the intermediate junction box that may occur due to melting can be prevented.

In addition, according to the intermediate junction box pressure compensator of the insulating oil impregnated ground insulating power cable according to the present invention and the power cable intermediate connection system having the same, the volume compensation chamber sealed inside the pressure compensating unit is provided for separate maintenance and management. Minimize and operate the pressure compensation device for the intermediate junction box of the insulation cable impregnated with insulating oil.

1 is a multi-stage stripped perspective view showing the configuration of a MI insulating oil impregnated power cable.
2 is a schematic diagram showing an intermediate junction box pressure compensator and a power cable intermediate junction system of the MI insulating oil impregnated ground insulating power cable according to an embodiment of the present invention.
FIG. 3 shows a detailed configuration diagram of a pressure control unit constituting the intermediate junction box pressure compensation device shown in FIG. 2.

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 and may be embodied in other forms. Rather, the embodiments introduced herein are provided to enable the disclosed contents to be thorough and complete, and to fully convey the spirit of the present invention to those skilled in the art. Throughout the specification, the same reference numbers refer to the same components.

In general, the insulating oil-impregnated power cable is connected by the intermediate junction box 200 at intervals of several hundred m to several km, and the ends of the insulating oil-impregnated power cable are connected to overhead lines by terminating them. Hereinafter, the configuration of the insulating oil-impregnated power cable will be described first, and then the connection process of the junction box will be described.

1 is a multi-stage stripped perspective view showing the configuration of a MI insulating oil impregnated power cable.

Referring to FIG. 1, the MI insulating oil impregnated power cable 100 includes a conductor 11, an inner semiconducting layer 12, an insulating layer 14, and an outer semiconducting layer 16, and cables along the conductor 11 The cable core portion 10 is configured to transmit electric power in the longitudinal direction and prevent leakage of current in the radial direction of the cable.

The conductor 11 serves as a passage through which current flows to transmit power, and has a high conductivity and strength and flexibility suitable for cable manufacturing and use, such as copper or aluminum, to minimize power loss. It can be made.

The conductor 11, as shown in Fig. 1, is provided with a flat core element layer 11C consisting of a circular center element element 11A and a flat element element element 11B twisted around the circular element element 11A. It may be a flat-angle conductor having a circular cross-section as a whole, and as another example, it may be a circular compression conductor compressed in a circular shape by twisting a plurality of circular elements. The flat-angled conductor has an advantage of being able to reduce the outer diameter of the cable, since the area of occupancy is relatively high compared to a circular compressed conductor.

Since the conductor 11 is formed by twisting a plurality of strands, the surface of the conductor 11 may be non-uniform, and corona discharge is likely to occur partially. In addition, when voids are formed between the surface of the conductor 11 and the insulating layer 14 to be described later, insulation performance may be deteriorated.

In order to solve the above problems, an inner semiconducting layer 12 may be formed outside the conductor 11. The inner semiconducting layer 12 may have semiconductivity by adding conductive particles such as carbon black, carbon nanotubes, carbon nanoplates, and graphite to an insulating material.

The inner semiconducting layer 12 prevents a sudden electric field change between the conductor 11 and the insulating layer 14 to be described later and functions to stabilize the insulating performance. In addition, by suppressing the uneven charge distribution on the conductor surface, the electric field is made uniform, and a gap between the conductor 11 and the insulating layer 14 is prevented from forming, thereby suppressing corona discharge, insulation breakdown, and the like. .

The insulating layer 14 is provided on the outside of the inner semiconducting layer 12 to electrically insulate the outside so that current flowing along the conductor 11 does not leak to the outside.

The insulating layer 14 may be formed of insulating paper impregnated with MI insulating oil. That is, the insulating layer 14 may be formed by winding a plurality of insulating papers so as to surround the inner semiconducting layer 12 and impregnating the MI insulating oil after the cable core portion is formed. As such, since the insulating oil is absorbed by the insulating paper, the insulating properties of the insulating layer 14 can be improved.

The insulating oil is filled in the gap between the layers formed by winding the insulating paper and the voids in the insulating paper to improve the insulating properties, and to reduce the friction between the insulating papers when bending the cable to improve the bending characteristics of the cable. The type of the insulating oil is not particularly limited, but should not be oxidized by heat in contact with copper or aluminum constituting the conductor 11, and an impregnation temperature, for example, 100° C. to easily impregnate the insulating paper. It is preferable to use a medium viscosity insulating oil having a sufficiently low viscosity and having a kinematic viscosity at 60°C of 10 to 500 centistokes or a high viscosity insulating oil having a kinematic viscosity at 60°C of 500 centistokes or more.

In the case of the OF power cable among the insulating oil impregnated power cables, the structure allowing active flow of insulating oil in conductors and insulating layers, etc., but the MI power cable according to the present invention impregnates insulating paper with insulating oil to increase the dielectric strength, but increases the flow of insulating oil. Since the structure is not premised, the amount of insulating oil is relatively small and the viscosity is high.

For example, the insulating oil may be one or more insulating oils selected from the group consisting of naphthenic insulating oil, polystyrene insulating oil, mineral oil, alkyl benzene or polybutene-based synthetic oil, and heavy acrylate.

The insulating paper may be a kraft paper obtained by removing the organic electrolyte from the pulp using kraft pulp as a raw material, or a composite insulating paper in which kraft paper is adhered to one or both sides of a plastic film. The plastic film has a greater resistivity than kraft paper adhered to one or both sides of the plastic film, and even if bubbles are generated in the kraft paper according to the flow of insulating oil during the impregnation process or cable operation, the voltage distributed to the bubbles can be relaxed, and polyethylene (Polyethylen) ), polypropylene, polybutylene, and other polyolefin-based resins or tetrafluoroethylene-hexafluoropropylene copolymers, ethylene-tetrafluoroethylene copolymers It may be made of a fluorine resin such as a coalescence, and preferably made of a polypropylene homopolymer resin having excellent heat resistance.

The insulating layer 14 may be formed by winding only kraft and impregnating it with insulating oil. In this case, the insulating oil flows in the direction of the cable load and voids may occur. On the other hand, when winding the composite insulating paper and impregnating 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 at the time of cable manufacturing or the operation at the time of cable operation Thermal expansion occurs depending on the temperature. When the thermoplastic resin undergoes thermal expansion, surface pressure is applied to the kraft paper laminated thereon, thereby narrowing the passage of the insulating oil, and thus it is possible to suppress the flow in the insulating oil flow due to gravity or the shrinkage/expansion of the insulating oil according to temperature. In addition, the composite insulating paper has an advantage of being able to reduce the outer diameter of the cable because it has a higher dielectric strength than kraft paper. In addition, as shown in FIG. 2, insulating paper may be wound in multiple stages so that the inner end of the insulating layer 14 forms a layer.

An external semiconducting layer 16 may be provided outside the insulating layer 14. The outer semiconducting layer 16 is formed of a material having semiconductivity by adding conductive particles, such as carbon black, carbon nanotubes, carbon nanoplates, graphite, etc., to the insulating material, such as the inner semiconducting layer, and the insulating layer The uneven charge distribution between (14) and the metal sheath 22 described later is suppressed to stabilize the insulation performance. In addition, the outer semiconducting layer 16 smoothes the surface of the insulating layer 14 in the cable to alleviate electric field concentration to prevent corona discharge, and also functions to physically protect the insulating layer 14 Can. In addition, the outer semiconducting layer 16 may further include a metallization paper. The metallization paper may be formed by laminating aluminum thin films on kraft paper, and a plurality of perforations (not shown) may be present to facilitate impregnation of the insulating oil of the insulating layer 14.

The cable core portion 10 may additionally include a moisture absorbing layer to prevent moisture from penetrating the cable. The moisture absorbing layer may be formed between the stranded wires of the conductor 11 and/or outside the conductor 11, the speed of absorbing moisture that has penetrated the cable is fast, and the ability to maintain the absorption state is excellent. It is composed of powder, tape, coating layer or film containing super absorbent polymer (SAP), and serves to prevent moisture from penetrating in the length of the cable. In addition, the moisture absorbing layer may have semiconductivity to prevent sudden electric field changes.

A cable protection part 20 is provided outside the cable core part 10, and the power cable laid on the seabed may additionally include a cable outer part (not shown). The cable protection part 20 and the cable outer part protect the core part 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 part 20 includes a metal sheath 22 and a polymer sheath 24 to protect the cable from accidental current, external force or other external environmental factors.

The metal sheath 22 may be formed to surround the cable core portion 10. In particular, when the power cable is laid in an environment such as the seabed, it may be formed to seal the cable core part 10 to prevent foreign matter such as moisture from entering the cable core part 10. The molten metal may be extruded to the outside of the cable core portion 10 to form a continuous outer surface without a seam, thereby making the water repellency excellent. As the metal, lead or aluminum is used, and in the case of a power cable laid on the seabed, it is preferable to use lead having excellent corrosion resistance to sea water, and an alloy lead in which a metal element is added to supplement mechanical properties It is more preferable to use (Lead alloy). In addition, the metal sheath 22 is grounded at the end of the power cable and serves as a passage through which an accident current flows when an accident such as a ground fault or short circuit occurs, protects the cable from external shock, and prevents an electric field from being discharged outside the cable. Can.

In addition, the metal sheath 22 is a corrosion-resistant compound, for example, blown asphalt is applied to the surface to further improve the corrosion resistance, water resistance, etc. of the cable and to improve the adhesion with the polymer sheath 24 Can.

In addition, between the metal sheath 22 and the cable core portion 10, a copper wire straight tape or a moisture absorbing layer 21 may be additionally provided. The copper wire straight tape is made of copper wire and non-woven tape, and functions to facilitate electrical contact between the outer semiconducting layer 16 and the metal sheath 22, and the moisture absorbing layer absorbs moisture that has penetrated the cable. It is composed of powder, tape, coating layer or film containing super absorbent polymer (SAP), which has a high speed to absorb and has excellent ability to maintain absorption, and prevents moisture from penetrating in the length of the cable. Plays a role. In addition, the copper wire direct tape and the moisture absorbing layer are preferably semiconducting in order to prevent a sudden electric field change, and can be configured by including a copper wire in the moisture absorbing layer so as to perform both energization and water absorption.

The polymer sheath 24 is formed on the outside of the metal sheath 22 to improve the corrosion resistance and water repellency of the cable, and to perform a function of protecting the cable from mechanical trauma and other external environmental factors such as heat and ultraviolet rays. Can. The polymer sheath 24 may be formed of a resin such as polyvinyl chloride (PVC), polyethylene, and the like, and in the case of a power cable laid on the seabed, it is preferable to use a polyethylene resin having excellent water resistance, and flame retardancy is required. In the environment, it is preferable to use polyvinyl chloride resin.

The power cable 100 is provided with a metal reinforcement layer 26 made of a galvanized steel strip or the like inside or outside the polymer sheath, so that the metal sheath 22 is expanded by the expansion of the insulating oil. Can be prevented.

In addition, a cable jacket 28 forming a cable sheath may be further provided outside the metal reinforcement layer 26.

In addition, when the power cable 100 is a submarine power cable or the like, a cable sheath (not shown) may be additionally provided outside the cable protection part.

2 is a schematic view showing an intermediate junction box pressure compensator 1000 having an intermediate junction box pressure compensator 1000 and an intermediate junction box 200 according to an embodiment of the present invention. In FIG. 2, an internal configuration is illustrated by cutting a portion of the intermediate junction box 200 to illustrate the internal configuration.

Referring to FIG. 2, first, the conductors of the insulating oil impregnating power cables 100A and 100B while the insulating layer 14 and the conductors 11A and 11B are exposed from the pair of MI insulating oil impregnating power cables 100A and 100B. Each end of 11A, 11B) is electrically connected to each other by crimping or welding with a crimping sleeve 1P.

After connecting each conductor of the insulating oil impregnated power cables 100A and 100B, a reinforced insulating layer 210 surrounding at least a portion of the insulating layer 14 including the connecting portions of the conductors 11A and 11B is formed. . The reinforcing insulating layer 210 may be made of an insulating paper and/or a composite insulating paper.

Subsequently, the semiconducting layer that is in communication with the outer semiconducting layer 16 of the cable and the metal layer that is in communication with the metal sheath 22 of the cable are restored on the reinforcing insulating layer 210, and a protective copper tube 240 is mounted. . The protective copper tube 240 protects the inside of the junction box from the outside, and can be connected to the metal sheath 22 of the cable 100 to serve as a passage for an accident current.

An end portion of the protective copper tube 240 is disposed on the metal sheath 22, and an end portion of the protective copper tube 240 is welded on the metal sheath 22 to form a softened portion 241. At least one spacer 280 for preventing contact between the protective copper tube 240 and the reinforcing insulating layer 240 may be further provided.

The intermediate junction box 200 is filled with high-viscosity insulating oil to strengthen the dielectric strength.

In the case of the MI insulating oil-insulated power cable and the intermediate junction box 200, the MI insulating oil is not in a flow structure, but the pressure inside the junction box may also increase significantly due to thermal expansion of the insulating oil due to the heating of the conductor when the power system is driven. .

The internal junction box 200 of the MI power cable has an internal temperature range when the power system is inactive, but the internal temperature may rise in the range of tens of degrees depending on weather or power transmission.

In the case of the intermediate junction box 200, when the predetermined maximum allowable pressure is exceeded due to an increase in the temperature inside, the damage to the power cables 100a, 100b, the protective copper tube 240, or the softened portion 241 is prevented. Therefore, the pressure inside the intermediate junction box 200 should be controlled when the system is driven.

Accordingly, the power cable intermediate connection system 1 according to the present invention includes the intermediate junction box 200 for connecting the MI power cable and the intermediate junction box pressure compensator 1000 of the power cable.

The intermediate junction box pressure compensator 1000 is mounted between the intermediate junction box 200, the pressure compensation unit 1200 and the intermediate junction box 200, and the pressure compensation unit 1200, the intermediate junction box 200 ) It may be configured to include a pressure control unit 1100 for controlling the internal pressure.

Specifically, the intermediate junction box pressure compensator 1000 of the present invention accommodates at least one volume variable chamber 1230 and the volume variable chamber 1230 filled with a compressive fluid therein, and the volume variable chamber 1230 ) Is accommodated, the housing 1250 is filled with insulating oil, and the insulating oil flows between the intermediate junction boxes 200 according to the pressure inside the intermediate junction box 200, and the intermediate junction boxes 200 A pressure compensation unit 1200 mounted around the periphery; And, is provided between the intermediate junction box 200 and the pressure compensation unit 1200 to flow the insulating oil or block the flow of insulating oil to control the internal pressure of the intermediate junction box 200 to be within a predetermined range It may be configured to include a pressure control unit 1100.

The pressure compensation unit 1200 constituting the intermediate junction box pressure compensator 1000 of the present invention is mounted around the protective copper tube 240 of the intermediate junction box 200 to the internal pressure of the intermediate junction box 200 Accordingly, the pressure inside the intermediate junction box 200 is controlled by receiving insulating oil from the intermediate junction box 200 or supplying insulating oil to the intermediate junction box 200. The pressure compensation unit 1200 may include at least one volume variable chamber 1230 whose volume can be reversibly changed according to the internal pressure.

The pressure compensation unit 1200 may be mounted around the intermediate junction box 200.

The pressure compensation unit 1200 illustrated in FIG. 2 illustrates an example provided in a ring shape on the outer circumferential surface of the protective copper tube 240 constituting the intermediate junction box 200.

In the embodiment shown in Figure 2, the housing 1250 is mounted to surround the outer circumferential surface of the protective copper tube 240 constituting the intermediate junction box 200 in the form of a ring may have a structure that does not protrude largely in appearance. . The housing 1250 may have at least one volume variable chamber 1230. In addition, the volume-variable chamber 1230 may have a corrugated tube structure capable of expansion or contraction depending on the pressure in the housing 1250.

The pressure compensation unit 1200 of the present invention is connected to the inside of the protective copper tube 240 of the intermediate junction box 200 and the insulating oil pipeline 1300 via the pressure control unit 1100, which will be described later, and the intermediate junction box 200 The internal pressure of the intermediate junction box 200 is adjusted by receiving insulating oil from the intermediate junction box 200 or supplying insulating oil to the intermediate junction box 200 according to the internal pressure.

The pressure compensation unit 1200 is connected to the pressure control unit 1100, which will be described later, and the protective copper pipe to constitute an insulating oil pipeline 1300 and may be used as an insulating oil supply or recovery path.

In addition, the pressure control unit 1100 may be arranged side by side in the side region of the pressure compensation unit 1200 to minimize the length of the insulating oil pipeline 1300 and the like.

The housing 1250 constituting the pressure compensation unit 1200 may be mounted in a ring shape on the outer peripheral surface of the protective copper tube 240.

In addition, as illustrated in FIG. 2, the housing 1250 constituting the pressure compensation unit 1200 may include at least one volume variable chamber 1230 whose volume can be reversibly changed according to pressure.

The volume variable chamber 1230 may be formed in a corrugated pipe structure or a bellows shape, and if the thickness of the stainless metal constituting the volume variable chamber 1230 is less than 0.2 mm (mm), the volume variable chamber 1230 If the minimum number of expansion contractions required, for example, about 30,000 times, cannot be sustained, and the thickness of the stainless metal constituting the volume variable chamber 1230 is greater than 0.4 mm (mm), contraction or restoration may be performed at the required maximum contraction ratio. It was confirmed that it was difficult to provide a pressure control function elastically. Here, the maximum contraction ratio of the volume variable chamber 1230 may be 40% to 60%.

The variable-volume chamber 1230 provided in the housing 1250 may be configured to contract or expand in the longitudinal direction of the intermediate junction box 200 inside the housing 1250 mounted in a ring shape.

That is, the volume variable chamber 1230 may be mounted such that the volume is variable in the width or thickness direction of the housing 1250.

A compressive fluid may be filled in the volume variable chamber 1230. For example, the compressive fluid may be in the form of a compressible gas, a compressible liquid or a mixture of a gas and a liquid, and a volume change (compression or expansion) is possible according to a change in the external pressure of the volume variable chamber and a material having low reactivity. Ramen is applicable.

This embodiment describes an example in which nitrogen gas is used as an example of the compressive fluid, but is not limited thereto.

In addition, one end of the volume variable chamber 1230 is supported by the housing 1250, the other end is displaced from the insulating oil receiving space 1251 in the housing 1250, and can be installed on a support plate 1252 that generates pressure. have.

Therefore, when there is a pressure difference between the intermediate junction box 200 and the pressure compensation unit 1200, the volume of the volume variable chamber 1230 in the housing of the pressure compensation unit 1200 changes and the insulating oil flows to the pressure. Deviation can be compensated.

Compared to the method of injecting gas into the insulating oil in this way and adjusting the internal pressure of the container, the present invention adopts the volume variable chamber 1230 so that there is no risk of dissolving the external supply gas in the insulating oil, so the insulation reliability in the intermediate junction box Can be further improved, and the initial setting of the system does not require additional maintenance and management. That is, the method of mounting the elastic member rather than the method of injecting gas for the pressure control function in the housing 1250 of the volume variable chamber 1230 can increase the reliability of the pressure buffer function of the volume variable chamber.

In the intermediate junction box 200, 50 liter (l) to 90 liter (l) of insulating oil is initially accommodated, and the upper pressure limit may be configured in a range of 15 bar to 25 bar.

In addition, the amount of initial insulating oil in the housing in which the volume variable chamber 1230 of the pressure compensation unit 1200 of the present invention is accommodated is 60% of the maximum amount of insulating oil that is acceptable when the volume variable chamber is contracted to the maximum. It is desirable to set the degree. Specifically, the housing 1250 buffers the insulating oil from the intermediate junction box 200, prevents damage to the volume variable chamber 1230, and is acceptable in the housing 1250 to provide a pressure balancing function as needed It has been experimentally confirmed that less than 60 percent of the maximum insulating oil capacity is preferred for the initial acceptance of insulating oil.

The variable-volume chamber 1230 may be configured in a ring-like manner in the housing 1250 configured in a ring shape, and may contract or expand in the longitudinal direction of the intermediate junction box according to a pressure change in the housing and adjust the pressure in the housing.

Of course, the volume variable chamber 1230 may be provided by being divided into a plurality in the housing, and in this case, a method in which nitrogen gas is filled in each volume variable chamber may be used.

In addition, the housing 1250 may be provided with a fluid injection port 1303 capable of injecting a compressive fluid or the like into the volume variable chamber 1230.

When the gas accommodated in the gas accommodation space 1231 in the volume variable chamber 1230 is lost, insufficient, or over-injected, gas is injected or discharged through the fluid injection port 1303 to insulate the oil receiving space 1251 in the housing 1250. ) Can control the volume of the volume variable chamber 1230 as a pressure control variable applied to the insulating oil accommodated.

The pressure control unit 1100 may be mounted on one side of the pressure compensation unit 1200 mounted on the outer circumferential surface of the intermediate junction box 200 in the form of a ring.

The pressure control unit 1100 has a structure in which a pipeline is branched inside, and various valves are installed on the separated pipeline. Hereinafter, a pressure control unit 1100 constituting the pressure compensation device 1000 of the present invention together with the pressure compensation unit 1200 will be described.

FIG. 3 shows a detailed configuration diagram of a pressure control unit constituting the intermediate junction box pressure compensation device shown in FIG. 2.

The flow direction of the insulating oil through the insulating oil conduit 1300 is determined according to the pressure difference between the intermediate junction box 200 and the pressure compensating unit 1200, and when the amount of insulating oil in the pressure compensating unit 1200 is increased, the As the pressure inside the pressure compensation unit 1200 increases, the volume variable chamber 1230 may contract.

Conversely, when the internal pressure of the intermediate junction box 200 is lowered and the insulating oil accommodated in the pressure compensation unit 1200 is recovered to the intermediate junction box 200, the volume is reduced as the pressure inside the pressure compensation unit 1200 decreases. The variable chamber 1230 may be expanded.

As described above, the volume variable chamber 1230 provided in the pressure compensation unit 1200 expands or contracts according to the amount of insulating oil flowing into the insulating oil container 1250 according to the internal pressure of the intermediate junction box 200, and automatically It is possible to form a flow of insulating oil.

The pressure control unit 1100 is installed on an insulating oil conduit 1300 connecting the intermediate junction box 200 and the pressure compensation unit 1200 to control the flow of insulating oil.

And, the pressure control unit 1100 constituting the intermediate junction box pressure compensation device 1000, when the internal pressure of the intermediate junction box 200 exceeds a predetermined pressure upper limit value (Pmax), the intermediate junction box 200 ) And the pressure compensation unit 1200 to open the pipeline between the intermediate junction box 200 to the pressure compensation unit 1200 to flow the insulating oil, the intermediate junction box 200 and the pressure compensation unit ( 1200) when the internal pressure of the intermediate junction box 200 decreases below the upper pressure limit (Pmax) after the pipeline is opened, the insulating oil pipeline may be blocked.

The intermediate junction box 200 may be set to be driven between a predetermined upper limit pressure value and a predetermined lower limit pressure value to prevent damage, such as a protective copper tube or a soft portion.

Therefore, the intermediate junction box pressure compensator 1000 of the present invention actively opens the conduit when the pressure of the intermediate junction box 200 exceeds the pressure upper limit value Pmax, which is the upper limit of the predetermined pressure range, and the insulating oil pressure compensation unit A method of reducing the pressure inside the intermediate junction box 200 by flowing toward the 1200 is used, and the pressure inside the intermediate junction box 200 is greater than the internal pressure of the pressure compensation unit 1200 within a predetermined range. When it is lowered, the insulating oil can be recovered from the pressure compensation unit 1200 to the intermediate junction box 200.

And this flow of insulating oil can be continuously generated. That is, the internal pressure of the intermediate junction box 200 exceeds a predetermined upper pressure limit (Pmax), opening the insulating oil pipeline between the intermediate junction box 200 and the pressure compensation unit 1200, the intermediate connection If the internal pressure of the box 200 decreases below the upper pressure limit (Pmax) and further, the pressure of the intermediate junction box 200 is lower than the pressure of the pressure compensation unit 1200, the pressure compensation unit 1200 In order to recover the insulating oil.

In order to actively control the flow of insulating oil according to the pressure inside the intermediate junction box 200, as shown in FIG. 3, the insulating oil conduit 1300 comprises a first conduit 1310 in the pressure control unit 1100 and Branched to the second conduit 1320, the pressure control unit 1100, when the internal pressure of the intermediate junction box 200 exceeds a predetermined pressure upper limit value (Pmax), is opened to the intermediate junction box 200 ), the first control unit 1110 installed in the first conduit 1310 and the intermediate connection in the pressure compensation unit 1200 so that insulating oil flows in the direction (A direction) of the pressure compensation unit 1200 A second control unit 1120 installed in the second conduit 1320 may be provided so that insulating oil flows in one direction (B direction) to the bin 200.

Here, when the first control unit 1110 is opened, insulating oil flows from the intermediate junction box 200 to a pressure compensation unit 1200 having a pressure lower than the upper pressure limit value Pmax, and after the insulating oil flows. When the internal pressure of the intermediate junction box 200 becomes lower than the upper pressure limit (Pmax), the first control unit 1110 is cut off from the intermediate junction box 200 to the pressure compensation unit 1200 The insulating oil may not flow. The first control unit 1110 may be configured as a relief valve.

For example, the intermediate junction box 200 is set at an internal pressure of 3 bar at the time of initial installation, and the upper pressure limit (Pmax) of a predetermined pressure range for operating the intermediate junction box according to a rise in temperature or a change in season is set to 20 bar. Can be set.

In addition, when the initial setting of the pressure control unit 1100, the set pressure of the first control unit 1110 in the form of a relief valve, that is, the pressure upper limit value Pmax of a predetermined pressure range that is a flow path opening pressure, is the pressure compensation unit 1200 In order to sufficiently exert the insulating oil buffer function of ), it is preferable that the pressure compensation unit 1200 is set larger than the initial setting internal pressure of the pressure compensation unit 1200 generated by the injection amount of insulating oil.

In this case, when the internal pressure of the intermediate junction box 200 rises to 25 bar due to the heat generation of the conductor and the outside temperature of the summer season, there is a possibility of damage to the protective copper tube or the soft section constituting the intermediate junction box 200. Since it is high, it is necessary to quickly lower the pressure inside the intermediate junction box.

In this case, the relief valve, which is the first control unit 1110, is opened and the insulating oil is supplied from the intermediate junction box 200 to the pressure compensation unit 1200.

The intermediate junction box 200 has an insulating oil capacity of several tens of liters (l), and the pressure compensation unit 1200 has an insulating oil capacity of several liters (l). Specifically, the intermediate junction box for the intermediate connection of the MI insulating oil impregnated ground insulation power cable accommodates approximately 50 liters (l) to 90 liters (l) of insulating oil, and the upper pressure limit (Pmax) of the predetermined pressure during operation is 15 bar. It may be a pressure within the range of 25 bar.

And, since the pressure compensation unit 1200 is provided with a volume variable chamber 1230 capable of contraction and expansion according to the inflow of insulating oil, when the insulating oil flows from the intermediate junction box 200, the volume variable chamber 1230 contracts. At the same time, the rebound pressure according to the compression of the volume variable chamber 1230 is applied to the insulating oil accommodated in the insulating oil container 1250 and increases the pressure in the pressure compensation unit 1200.

That is, when the pressure inside the intermediate junction box 200 exceeds the predetermined upper pressure limit value Pmax, the pressure compensation unit 1200 accommodates the insulating oil supplied by the first control unit 1110 and supplies its own pressure. In addition, it has an increased structure, and conversely, when the pressure inside the pressure compensation unit 1200 becomes larger, the insulating oil may be supplied to the intermediate junction box 200.

By providing a volume variable chamber 1230 in the pressure compensation unit 1200, the insulating oil in a liquid state can be self-flowing according to a pressure difference like a good compressible gas so that pressure balance can be achieved.

Compared to the method of injecting gas into the insulating oil in this way and adjusting the internal pressure of the container, the present invention further improves the insulation reliability in the intermediate junction box because there is no risk that the external supply gas is dissolved in the insulating oil by adopting the volume variable chamber. System, and does not require additional maintenance and maintenance with the initial setup of the system.

The pressure compensation unit 1200 buffers the insulating oil from the intermediate junction box 200, prevents damage to the volume variable chamber 1230, and accommodates it in the pressure compensation unit 1200 to provide a pressure balancing function as necessary. It is as described above that it has been experimentally confirmed that it is desirable that the insulating oil of 60% or less of the maximum possible insulating oil capacity is initially accommodated.

The internal pressure of the intermediate junction box 200 is generated by the expansion of the volume of the insulating oil in a liquid state for reasons such as heat generation of the conductor, and even though a small amount of insulating oil inside the intermediate junction box 200 is through the first control unit 1110. Even when the pressure compensation unit 1200 flows out, the pressure inside the intermediate junction box 200 may be quickly lowered.

Further, the first control unit 1110 is a valve for selectively blocking the flow of insulating oil from the intermediate junction box 200 toward the pressure compensation unit 1200 according to the internal pressure condition of the intermediate junction box 200 Can be configured.

However, the second control unit 1120 installed on the second conduit 1320 may be a connector for restricting the flow of insulating oil in one direction. Specifically, the second control unit 1120 may be configured as a check connector for allowing only the direction of the intermediate junction box 200 in the pressure compensation unit 1200.

Therefore, since the first control unit 1110 is blocked when the pressure inside the intermediate junction box 200 is less than or equal to the pressure upper limit value Pmax, insulating oil cannot flow into the first conduit 1310. Conversely, when the internal pressure of the pressure compensation unit 1200 is greater than the pressure inside the intermediate junction box 200, until the pressure equilibrium of the pressure compensation unit 1200 and the intermediate junction box 200 is formed The intermediate junction box 200 may be configured to supply insulating oil in one direction through a second conduit 1320 and a second control unit 1120 installed on the second conduit 1320.

That is, when the pressure inside the intermediate junction box 200 decreases the amount of power transmitted through the power cable or greatly decreases due to reasons such as winter, when the volume of insulating oil decreases and vacuuming or cavity occurs, the insulating oil is reversed. To solve the problem.

In summary, when the pressure in the intermediate junction box 200 decreases and the internal pressure of the intermediate junction box 200 becomes smaller than the pressure of the pressure compensation unit 1200, the intermediate junction box 200 and the pressure Insulation oil may flow through the second control unit 1120 from the pressure compensation unit 1200 to the intermediate junction box 200 until the internal pressure balance of the compensation unit 1200 is formed, and the pressure When the insulating oil is supplied from the compensation unit 1200 to the intermediate junction box 200 through the second conduit 1320, the internal pressure of the pressure compensation unit 1200 is also reduced, so that the pressure can be balanced with the intermediate junction box 200. have.

In addition, since the second control unit 1120 is composed of a one-way check connector in the direction of the intermediate junction box 200, even if the internal pressure of the intermediate junction box 200 becomes greater than the pressure of the pressure compensation unit 1200 It can block the flow of insulating oil.

That is, when the pressure inside the intermediate junction box 200 is maintained within a predetermined range between the upper pressure limit value Pmax and the lower pressure limit value Pmin, the internal pressure of the intermediate junction box 200 is the pressure compensation unit 1200 ) Even if it is greater than the internal pressure, it is not necessary to lower the internal pressure of the intermediate junction box 200 equal to the internal pressure of the pressure compensation unit 1200. This is because when the insulating oil suddenly flows out of the insulating layer or the insulating reinforcing layer of the intermediate junction box 200, a cavity or the like is generated, which may damage the insulating layer or degrade the insulating performance.

Therefore, the second control unit 1120 blocks the flow of insulating oil from the intermediate junction box 200 to the pressure compensation unit 1200 through the second conduit 1320, and the first control unit is opened. When the internal pressure of the pressure compensation unit 1200 is greater than the internal pressure of the intermediate junction box 200 in a pressure range that is not set, the pressure compensation unit 1200 is set to supplement the insulating oil with the intermediate junction box 200 It can be understood as.

In this way, the intermediate junction box 200 and the pressure compensation unit 1200 are respectively connected to one insulating oil pipeline 1300, and the pressure control unit 1100 connects the insulating oil pipeline 1300 with the first pipeline 1310. After branching from the first branch part (x) to the second conduit (1320), each of the valves of different types are mounted, and only when the pressure inside the intermediate junction box (200) becomes greater than the predetermined upper pressure limit (Pmax). Insulating oil flows to the pressure compensating unit 1200 and in a predetermined range, the pressure compensating unit 1200 allows the flow of insulating oil only in the direction of the intermediate junction box 200 to reach pressure equilibrium. The pressure control unit 1100 can be configured to be mounted inside the outermost housing of the intermediate junction box because it can be modularized when the length of each conduit is compact, and the maintenance process of gas injection from the outside is possible. Since this is unnecessary, there is no need for additional equipment, and there is no need to be connected to the outside, so the power cable intermediate connection system having the intermediate junction box pressure compensation device of the MI insulating oil impregnated ground insulating power cable of the present invention has a structure and method suitable for underground installation.

Specifically, as shown in FIGS. 2 and 3, the pressure control unit 1100 is provided with a compact housing 1150 and a pipeline is branched in the housing 1150, and each control unit is accommodated. , Minimize the length of the insulating oil conduit 1300 connecting the pressure compensation unit 1200 and the intermediate junction box 200, respectively, may be mounted on the outer peripheral surface of the intermediate junction box. A through hole is formed in the protective copper pipe of the intermediate junction box 200, and an insulating oil pipeline 1300 connecting the pressure control unit 1100 and the intermediate junction box 200 is connected to expose a pipe-type pipeline to the outside. Not, the insulating oil can flow in both directions.

And, referring to the configuration shown in Figure 3, when the pressure inside the intermediate junction box 200 exceeds the pressure upper limit value (Pmax) of a predetermined range, the first control unit 1110 as a relief valve is opened The insulating oil supplied through the first conduit 1310 in the process of supplying the insulating oil of the intermediate junction box 200 to the pressure compensation unit 1200 via the insulating oil conduit 1300 and the first conduit 1310 A flows in the direction of the second control unit 1120, which is a check connector having a structure opened in the direction of the intermediate junction 200 at the second branch part y, which is the branch point of the first pipe 1310 and the second pipe 1320. There is a possibility of concern, but since the pressure inside the intermediate junction box 200 exceeds the upper pressure limit, the pressure at the outlet side of the second control unit 1120 will be the size corresponding to the pressure inside the intermediate junction box. The flow of insulating oil in the direction of the second control unit 1120 does not occur at the intersection of the first conduit 1310 and the second conduit 1320.

In this way, since the piping and equipment of the intermediate junction box pressure compensator of the present invention can be simplified and the size can be reduced, and the method of injecting gas into the insulating oil is not used to form the pressure of the insulating oil, the gas is dissolved in the insulating oil. It is possible to prevent damage to the insulating layer of the intermediate junction box, which can be generated, and the volume compensation chamber sealed inside the pressure compensation unit is provided to minimize separate maintenance and management, and to insulate the insulating cable from the impregnated power cable. Compensation device can be operated.

Although this specification has been described with reference to preferred embodiments of the present invention, those skilled in the art variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You can do it. Therefore, if the modified implementation basically includes the components of the claims of the present invention, it should be considered that all are included in the technical scope of the present invention.

1: Power cable intermediate connection system
100: power cable
200: intermediate junction box
1000: Medium junction box pressure compensation device
1100: Pressure control unit
1200: pressure compensation unit
1400: cover member

Claims (17)

In the intermediate junction box pressure compensator of the power cable to adjust the pressure inside the intermediate junction box is connected to the intermediate junction box for the intermediate connection of insulating oil impregnated power cable,
And at least one volume-variable chamber filled with a compressive fluid therein, and a housing accommodating the volume-variable chamber and filled with insulating oil in a state in which the volume-variable chamber is accommodated, and insulating oil according to the pressure inside the intermediate junction box. A pressure compensation unit that flows between intermediate junction boxes and is mounted around the intermediate junction boxes; And,
Intermediate connection of the power cable comprising; a pressure control unit provided between the intermediate junction box and the pressure compensating unit to control the internal pressure of the intermediate junction box to flow the insulating oil or block the flow of insulating oil so that the internal pressure of the intermediate junction box is within a predetermined range. Pressure compensation device. According to claim 1,
The volume variable chamber is an intermediate junction box pressure compensation device, characterized in that it has a corrugated tube structure that can be expanded or contracted according to the pressure in the pressure compensation unit. According to claim 2,
The pressure compensating device of the intermediate junction box, characterized in that the housing constituting the pressure compensation unit is mounted to surround the outer peripheral surface of the protective copper tube constituting the intermediate junction box in the form of a ring. According to claim 3,
The pressure compensation device of the intermediate junction box, characterized in that the volume variable chamber provided in the pressure compensation unit is configured to contract or expand in the longitudinal direction of the intermediate junction box. According to claim 4,
The volume variable chamber is an intermediate junction box pressure compensation device, characterized in that provided in the ring shape in the housing of the pressure compensation unit. According to claim 3,
The pressure control unit is provided in the vicinity of the side of the pressure compensation unit, and the pressure control unit is provided with an insulating oil passage connecting the pressure compensation unit and the inside of the protective copper tube of the intermediate junction box,
The pressure control unit is connected to the pressure compensation unit and the insulating oil conduit in the longitudinal direction of the cable, and the pressure control unit is the intermediate junction box pressure characterized in that the insulating oil conduit is connected in the radial direction of the intermediate junction box and the intermediate junction box. Compensation device. According to claim 1,
The pressure control unit, when the internal pressure of the intermediate junction box exceeds a predetermined upper pressure limit, opens the insulating oil channel between the intermediate junction box and the pressure compensation unit, and the insulating oil flows from the intermediate junction box to the pressure compensation unit. Medium junction pressure compensation device characterized in that to flow. The method of claim 7,
In the pressure control unit, the internal pressure of the intermediate junction box exceeds a predetermined upper pressure limit, and after opening the insulating oil pipe between the intermediate junction box and the pressure compensation unit, the internal pressure of the intermediate junction box decreases below the upper pressure limit value. In case, the intermediate junction box pressure compensation device, characterized in that to block the insulating oil pipeline. According to claim 1,
The pressure control unit is provided with an insulating oil pipeline connecting and connecting the pressure compensation unit and the intermediate junction box,
The insulating oil conduit in the pressure control unit is branched from the pressure control unit to the first conduit and the second conduit,
When the internal pressure of the intermediate junction box exceeds a predetermined upper pressure limit, the pressure control unit is opened and a first control unit installed in the first conduit to allow insulating oil to flow from the intermediate junction box to the pressure compensation unit. ; And a second control unit installed in the second conduit to allow the flow of insulating oil in one direction from the pressure compensation unit to the intermediate junction box. The method of claim 9,
When the first control unit is opened, when the insulating oil flows from the intermediate junction box to the pressure compensation unit, and after the insulating oil flows, the internal pressure of the intermediate junction box becomes lower than the upper pressure limit, the first control Intermediate junction box pressure compensation device, characterized in that the unit is blocked and the insulating oil does not flow from the intermediate junction box to the pressure compensation unit. The method of claim 10,
The first control unit is an intermediate junction box pressure compensation device, characterized in that the relief valve. The method of claim 9,
If the internal pressure of the intermediate junction box is less than the pressure of the pressure compensation unit, the pressure control unit from the pressure compensation unit to the intermediate junction box until the internal pressure balance between the intermediate junction box and the pressure compensation unit is formed. Intermediate junction box pressure compensation device characterized in that the insulating oil flows through. The method of claim 12,
The second control unit is an intermediate junction box pressure compensation device, characterized in that the check connector. The method of claim 9,
The intermediate junction box is 50 liters (l) to 90 liters (l) of the insulating oil is initially accommodated, the pressure upper limit value of the intermediate junction box pressure compensation device, characterized in that a value in the range of 15bar to 25bar. The method of claim 14,
The pressure compensation unit is an intermediate junction box pressure compensation device characterized in that the insulating oil of less than 60% of the maximum insulating oil capacity is initially received. The method of claim 9,
The intermediate junction box pressure compensation device, characterized in that the pressure upper limit value, which is the initial setting pressure of the first control unit, is greater than the initial setting pressure of the pressure compensation unit. A power cable intermediate connection system for intermediately connecting an insulating oil impregnated power cable,
An intermediate junction box in which a pair of power cables are intermediately connected and filled with insulating oil;
A power cable intermediate connection system comprising the intermediate junction box pressure compensator according to any one of claims 1 to 16.

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