KR102638867B1 - Apparatus and method for compaensating pressure of termination connection box - Google Patents

Abstract

The present invention is an end junction box pressure compensation device that can prevent the insulation breakdown of the cable by creating a cavity in the insulation layer of the cable due to the insulating oil in the cable flowing into the end junction box with low pressure when the cable is energized, and the end junction box pressure compensation using the same. It relates to a system and a junction box pressure compensation method.

Description

Termination box pressure compensation device, termination box pressure compensation system using the same, and termination connection box pressure compensation method {Apparatus and method for compaensating pressure of termination connection box}

The present invention relates to a junction box pressure compensation device, a junction box pressure compensation system using the same, and a junction box pressure compensation method.

In general, power cables are used to supply power to a desired location through the ground, ground, or seabed using a conductor that supplies power. For these power cables, it is very important to insulate the conductors, and for this purpose, the insulating layer that insulates the conductors is manufactured using XLPE (Cross-linked Polyethylene) as a raw material, or is made by wrapping insulating paper, etc. I am using it.

The power cables are connected by joint boxes at intervals of hundreds of meters or tens of kilometers, and the ends of the power cables are connected to overhead lines by termination connection boxes. The termination box can be classified into an air termination box, a gas termination box, and an oil termination box depending on the state in which the leaded conductor end of the cable is connected.

The air termination box is provided with a pipe into which the power cable is inserted at a predetermined length, and the inside of the pipe is filled with insulating oil.

In the case of a power cable whose insulating layer is formed with insulating paper impregnated with insulating oil, an insulating oil pressure tank can be used to maintain the pressure within the power cable.

Specifically, when the power cable is energized or the external temperature rises, the temperature of the power cable rises and the insulating oil in the power cable and the insulating oil in the termination box connected to the power cable expand, thereby causing the power cable and The pressure of the insulating oil in the terminal junction box increases. In addition, when the power cable is not energized or the external temperature decreases, the temperature of the power cable decreases and the insulating oil in the power cable and the insulating oil in the termination box connected to the power cable shrink, thereby causing the power cable and the termination connection. The pressure of the insulating oil inside the ship decreases.

The insulating oil pressure tank connected to the terminal junction box can maintain a pressure of approximately 3 bar. When the pressure of the termination box becomes greater than the pressure of the insulating oil pressure tank, the insulating oil moves from the insulating oil pressure tank to the terminal connection due to the pressure difference, and the pressure of the termination box is smaller than the pressure of the insulating oil pressure tank. Insulating oil moves from the insulating oil pressure tank on the ground to the terminal connection box, so that the pressure of the terminal connection box can be maintained within a certain range.

However, in the case of high-voltage cables, when electricity is applied, the temperature of the insulating oil in the cable rises very high, and the pressure of the insulating oil increases accordingly. As a result, the difference between the pressure of the high-voltage cable and the pressure of the insulating oil pressure tank becomes very large, and the cable and terminal connection box become very large. The amount of insulating oil flowing into the insulating oil pressure tank increases. Due to the continuous flow of insulating oil from the cable and termination box to the insulating oil pressure tank, the insulating oil impregnated in the cable insulating layer also flows, forming a cavity in the insulating layer, and there is a problem in that insulation breakdown occurs in the cavity.

The purpose of the present invention is to provide an end junction box pressure compensation device that can maintain the pressure within the end junction box within a certain range even when the cable is energized or the external temperature rises, an end junction box pressure compensation system using the same, and an end junction box pressure compensation method. It is provided.

The insulating oil pressure tank according to an embodiment of the present invention is an end connection box pressure compensation device disposed between an insulating oil pressure tank and an end connection box connected to the end of an insulating oil impregnated cable, wherein the pressure compensation device includes the insulating oil pressure tank. By flowing or blocking the insulating oil from the tank to the end connection box, or from the end connection box to the insulating oil pressure tank, the pressure of the insulating oil-impregnated cable or the end connection box, which fluctuates according to the temperature change of the insulating oil-impregnated cable, is adjusted to a predetermined level. It can be controlled to stay within the pressure range.

In the present invention, the pressure compensation device, when the pressure of the termination box increases and reaches the upper pressure value of the predetermined pressure range, opens the pipe between the termination box and the insulating oil pressure tank to terminate the termination. By allowing the insulating oil to flow from the junction box to the insulating oil pressure tank, the pressure of the terminal junction box can be prevented from exceeding the upper pressure value.

In the present invention, the pressure compensation device is configured to allow the insulating oil to flow from the end connection box to the insulating oil pressure tank after opening the pipe between the end connection box and the insulating oil pressure tank so that the pressure of the end connection box is set to the upper pressure value. If it becomes less than that, the pipe can be blocked.

In the present invention, the pressure compensation device opens the pipe between the termination box and the insulating oil pressure tank when the pressure of the termination box decreases and the pressure of the termination box becomes lower than the pressure in the insulating oil pressure tank. By allowing the insulating oil to flow from the insulating oil pressure tank to the terminal connection box, the pressure of the terminal connection box can be prevented from falling below the lower limit pressure value of the predetermined pressure range.

In the present invention, the pressure compensation device is configured to allow the insulating oil to flow from the insulating oil pressure tank to the end connection box after opening the pipe between the end connection box and the insulating oil pressure tank so that the pressure of the end connection box increases in the insulating oil pressure tank. If the pressure is equal to or greater than the pressure, the pipe can be blocked.

In the present invention, the pressure compensation device includes: a first valve that opens when the pressure of the termination box exceeds a preset pressure value to allow insulating oil to flow from the termination box to the insulating oil pressure tank; and when the pressure of the terminal connection box decreases and becomes lower than the pressure of the insulating oil pressure tank, a second valve that opens to allow the insulating oil to flow from the insulating oil pressure tank to the terminal connection box. can be provided.

In the present invention, when the insulating oil-impregnated cable is energized, the insulating oil expands due to a rise in temperature of the insulating oil, and the pressure in the termination box increases, and the pressure in the termination box increases to the preset pressure. When the value is exceeded, it is opened, and the insulating oil flows from the termination box to the insulating oil pressure tank that maintains a pressure lower than the preset pressure value, and after the flow of the insulating oil, the pressure of the termination box is lower than the preset pressure value. When the pressure value is lower than the pressure value, the first valve may be closed so that the insulating oil does not flow from the end connection 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 insulating oil cools and contracts, thereby lowering the pressure in the end connection box, so that the pressure in the end connection box becomes lower than the pressure in the insulating oil pressure tank, and maintains a constant pressure. When the insulating oil flows from the insulating oil pressure tank to the terminal connection box, and the pressure of the terminal connection box 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 and the insulating oil The insulating oil may not flow through the terminal connection in the pressure tank.

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

An end junction box pressure compensation system according to an embodiment of the present invention includes an insulating oil pressure tank that accommodates insulating oil; When the pressure of the termination box exceeds a preset pressure value, a first valve opens to allow insulating oil to flow from the termination box to the insulating oil pressure tank; and when the pressure of the terminal connection box decreases and becomes lower than the pressure of the insulating oil pressure tank, a second valve that opens to allow the insulating oil to flow from the insulating oil pressure tank to the terminal connection box. can be provided.

In the present invention, when the insulating oil-impregnated cable is energized, the insulating oil expands due to a rise in temperature of the insulating oil, and the pressure in the termination box increases, and the pressure in the termination box increases to the preset pressure. When the value is exceeded, it is opened, and the insulating oil flows from the termination box to the insulating oil pressure tank that maintains a pressure lower than the preset pressure value, and after the flow of the insulating oil, the pressure of the termination box is lower than the preset pressure value. When the pressure value is lower than the pressure value, the first valve may be closed so that the insulating oil does not flow from the end connection 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 insulating oil cools and contracts, thereby lowering the pressure in the end connection box, so that the pressure in the end connection box becomes lower than the pressure in the insulating oil pressure tank, and maintains a constant pressure. When the insulating oil flows from the insulating oil pressure tank to the terminal connection box, and the pressure of the terminal connection box 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 and the insulating oil The insulating oil may not flow through the terminal connection in the pressure tank.

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

The termination box pressure compensation method according to an embodiment of the present invention is a method of compensating the pressure of the termination box by filling insulating oil in a termination box connected to an insulating oil pressure tank and placed at the end of an insulating oil-impregnated cable, When the pressure of the termination box exceeds a preset pressure value, a first valve disposed between the termination box and the insulating oil pressure tank is opened to allow insulating oil to flow from the termination box to the insulating oil pressure tank; closing the first valve when the insulating oil flows from the end connection box to the insulating oil pressure tank and the pressure of the end connection box becomes less than the preset pressure value; When the pressure of the termination box decreases and becomes lower than the pressure of the insulating oil pressure tank, the second valve disposed between the termination box and the insulating oil pressure tank is opened and the insulating oil flows from the insulating oil pressure tank to the termination. flowing step; and closing the second valve when the insulating oil flows from the insulating oil pressure tank to the termination box and the pressure of the termination box becomes equal to or greater than the pressure of the insulating oil pressure tank. can be provided.

In the present invention, when the insulating oil-impregnated cable is energized, the insulating oil expands due to a rise in temperature of the insulating oil, and the pressure in the termination box increases, and the pressure in the termination box increases to the preset pressure. When the value is exceeded, it is opened, and the insulating oil flows from the termination box to the insulating oil pressure tank that maintains a pressure lower than the preset pressure value, and after the flow of the insulating oil, the pressure of the termination box is lower than the preset pressure value. When the pressure value is lower than the pressure value, the first valve may be closed so that the insulating oil does not flow from the end connection 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 insulating oil cools and contracts, thereby lowering the pressure in the end connection box, so that the pressure in the end connection box becomes lower than the pressure in the insulating oil pressure tank, and maintains a constant pressure. When the insulating oil flows from the insulating oil pressure tank to the terminal connection box, and the pressure of the terminal connection box 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 and the insulating oil The insulating oil may not flow through the terminal connection in the pressure tank.

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

According to the present invention, by maintaining the pressure in the cable within a certain range, the insulating oil in the cable flows into the insulating oil pressure tank due to the difference between the pressure in the cable and the pressure in the insulating oil pressure tank, creating a cavity in the insulating layer of the cable, thereby preventing insulation breakdown of the cable. It can be prevented.

Figure 1 is a partially cut away perspective view showing the configuration of an insulating oil-impregnated cable.
Figure 2 is a schematic diagram showing a junction box pressure compensation system including a junction box pressure compensation device and an end junction box according to an embodiment of the present invention.
Figure 3 is a diagram showing an embodiment of a terminal junction box pressure compensation device.
Figure 4 is a flowchart showing a method for compensating pressure in an end junction box according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached 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 so that the disclosure will be thorough and complete, and so that the spirit of the invention can be sufficiently conveyed to those skilled in the art. Like reference numerals refer to like elements throughout the specification.

In general, insulating oil-impregnated cables are connected by intermediate connections at intervals of hundreds of meters or several kilometers, and the ends of the insulating oil-impregnated cables are connected to overhead lines by terminal connections. Below, we will first look at the configuration of the insulating oil-impregnated power cable, and then look at the connection process of the junction box.

Figure 1 is a partially cut away perspective view showing the internal structure of an ultra-high voltage direct current power cable.

Referring to FIG. 1, the power cable 100 includes a conductor 11, an inner semiconducting layer 12, an insulating layer 14, and an outer semiconducting layer 16, and extends along the conductor 11 in the cable length direction. It is provided with a cable core portion 10 that transmits only power and prevents current from leaking in the radial direction of the cable.

The conductor 11 serves as a passage through which current flows to transmit power, and is made of a material that has excellent conductivity to minimize power loss and has appropriate strength and flexibility for cable manufacturing and use, such as copper or aluminum. It can be done.

As shown in FIG. 1, the conductor 11 includes a rectangular wire layer 11C consisting of a circular center wire 11A and a square wire 11B twisted to surround the circular center wire 11A. It may be a rectangular conductor with an overall circular cross-section, and as another example, it may be a circular compressed conductor made by twisting a plurality of circular wires and compressing them into a circular shape. The square conductor has a relatively high space factor compared to the circular compressed conductor, so it has the advantage of being able to reduce the outer diameter of the cable.

Since the conductor 11 is formed by stranding a plurality of wires, its surface is not smooth, so the electric field may be non-uniform, and corona discharge is likely to occur locally. Additionally, if a gap is created between the surface of the conductor 11 and the insulating layer 14, which will be described later, the insulating performance may deteriorate.

In order to solve the above problems, an internal semiconducting layer 12 may be formed outside the conductor 11. The internal 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 internal semiconducting layer 12 functions to stabilize insulation performance by preventing sudden changes in electric field between the conductor 11 and the insulating layer 14, which will be described later. In addition, by suppressing uneven charge distribution on the conductor surface, the electric field is made uniform and a gap is prevented from forming between the conductor 11 and the insulating layer 14, thereby suppressing corona discharge and insulation breakdown. .

The insulating layer 14 is provided outside the internal semiconducting layer 12 and electrically insulates the current flowing along the conductor 11 from the outside to prevent it from leaking 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 insulating paper in multiple layers to surround the internal semiconducting layer 12, and impregnating the cable core with insulating oil after forming. As the insulating oil is absorbed into the insulating paper, the insulating properties of the insulating layer 14 can be improved.

The insulating oil improves the insulating properties by filling the voids inside the insulating paper and the gaps between layers formed by winding the insulating paper, and improves the bending properties of the cable by reducing friction between the insulating paper when the cable is bent. The type of insulating oil is not particularly limited, but it must not be oxidized by heat in contact with copper or aluminum constituting the conductor 11, and must have an impregnation temperature of, for example, 100°C to easily impregnate the insulating paper. It is preferable to use a medium-viscosity insulating oil that has a sufficiently low viscosity and a kinematic viscosity of 10 to 500 centistoke at 60°C, or a high-viscosity insulating oil that has a kinematic viscosity of 500 centistoke or more at 60°C.

When using low-viscosity insulating oil with a relatively low viscosity, it is necessary to pressurize the insulating oil using an oil supply facility to maintain the insulating paper impregnated with the insulating oil and to prevent voids from forming in the insulating layer due to the flow of insulating oil. There is. However, when using medium- or high-viscosity insulating oil, there is an advantage in that the flow of insulating oil is small, so there is no need for refueling equipment to pressurize the insulating oil, or the number of required refueling equipment can be reduced, and the cable extension length can be lengthened. For example, the insulating oil may be one or more types of insulating oil selected from the group consisting of naphthene-based insulating oil, polystyrene-based insulating oil, mineral oil, alkyl benzene or polybutene-based synthetic oil, heavy alkelate, etc.

The insulating paper may be Kraft paper made from Kraft pulp and the organic electrolyte in the pulp has been removed, or it may be a composite insulating paper obtained by adhering Kraft paper to one or both sides of a plastic film. The plastic film has a higher resistivity than the kraft paper bonded to one or both sides, so even if bubbles are generated in the kraft paper due to the flow of insulating oil during the impregnation process or cable operation, the voltage shared by the bubbles can be alleviated, and polyethylene (Polyethylene) ), polyolefin resins such as polypropylene and polybutylene, tetrafluoroethylene-hexafluoropropylene copolymer, and ethylene-tetrafluoroethylene copolymer. It may be made of a fluorine resin such as a polymer, and preferably may be made of a polypropylene homopolymer resin with excellent heat resistance.

Specifically, the insulating layer 14 can be formed by winding only Kraft and impregnating it with insulating oil. In this case, the insulating oil may flow in the direction of the cable load, resulting in voids. On the other hand, when the insulating layer 14 is formed by winding a composite insulating paper and impregnating it with insulating oil, thermoplastic resins such as polypropylene resin are not impregnated with insulating oil, and the impregnation temperature during cable manufacturing or operation during cable operation is not impregnated with insulating oil. Thermal expansion occurs depending on temperature. When the thermoplastic resin thermally expands, surface pressure is applied to the laminated kraft paper, which narrows the passage for the insulating oil to move, which has the effect of suppressing the flow of insulating oil due to gravity or the contraction/expansion of insulating oil according to temperature. In addition, the composite insulating paper has a higher dielectric strength than kraft paper, so it has the advantage of being able to reduce the outer diameter of the cable.

Meanwhile, when the power cable is energized, heat is generated in the conductor that serves as a path through which current flows, and the temperature gradually decreases from the inside to the outside in the radial direction of the cable, resulting in a temperature difference even in the insulating layer 14. do. Therefore, the insulating oil of the insulating layer belonging to the section directly above the conductor, that is, the insulating layer formed on the internal semiconducting layer 12, has a lower viscosity, undergoes thermal expansion and moves outward, and when the cable temperature drops, the moved insulating oil As the viscosity increases and does not return to its original state, voids may form in the insulating layer in the section directly above the conductor.

In addition, the electric field is gradually reversed according to the temperature difference, and a high electric field is applied to the insulating layer belonging to the section directly below the metal sheath where the electric field gradually increases, that is, the insulating layer formed in the direction of the outer semiconducting layer 16. The section directly above the conductor and the section directly below the metal sheath are highly likely to generate air gaps, and are areas where high electric fields act depending on temperature changes inside the cable, and can act as weak insulation areas that can be the starting point of partial discharge, insulation breakdown, etc.

In order to solve the above-described problem, only kraft paper can be used as insulating paper in the area of the insulating layer 14 that includes the insulating 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 from the inner semiconducting layer 12 to the outer semiconducting layer 16 to be described later, and the first insulating layer and/ Alternatively, only Kraft can be used for the third insulating layer, and the above composite insulating paper can be used for the second insulating layer.

In this case, a difference in resistivity occurs between the second insulating layer on which composite insulating paper is wound and the first and/or third insulating layers on which kraft paper is wound, and the first insulating layer 14 on which kraft paper with low resistivity is wound The first insulating layer and/or the third insulating layer have a relatively low resistivity and serve to alleviate the electric field distributed to the vulnerable insulating portion. Specifically, due to the resistive electric field distribution characteristics of a direct current cable in which the electric field is distributed according to the resistivity, a high electric field is applied to the second insulating layer wound with composite insulating paper with high resistivity, and to the first insulating layer and/or the third insulating layer. Since a relatively low electric field is applied to the section directly above the included conductor and/or the section directly below the metal sheath, the electric field acting on the vulnerable part of the insulation is alleviated, thereby stabilizing the insulation performance.

Additionally, the insulating layer 14 may have a third insulating layer thicker than the first insulating layer. When forming a metal sheath 22, which will be described later, on the outside of the insulating layer 14, or when restoring the metal sheath 22 after connecting two power cables with the cable core portion sequentially exposed from the inside, etc. Since heat may be applied to the second insulating layer of the insulating layer 14 and cause deformation of the plastic film, the second insulating layer is formed thicker than the first insulating layer to protect the plastic film of the second insulating layer from heat. It is desirable to protect. In this case, the thickness of the first insulating layer can be selected in consideration of the impulse surge voltage required for the power cable.

An external semiconducting layer 16 may be provided outside the insulating layer 14. The outer semiconducting layer 16, like the inner semiconducting layer, is formed of a semiconductive material by adding conductive particles, such as carbon black, carbon nanotubes, carbon nanoplates, and graphite, to an insulating material, and the insulating layer Insulating performance is stabilized by suppressing uneven charge distribution between (14) and the metal sheath 22, which will be described later. 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 performs the function of physically protecting the insulating layer 14. You can. Additionally, the outer semiconducting layer 16 may additionally include metalized paper. The metalized paper can be formed by laminating an aluminum thin film on kraft paper, and a plurality of perforations may be present to facilitate impregnation of the insulating layer 14 with insulating oil.

The cable core portion 10 may additionally be provided with a moisture absorbing portion 21 to prevent moisture from penetrating into the cable. The moisture absorbing portion may be formed between the stranded wires of the conductor 11 and/or outside the conductor 11, and has a high speed of absorbing moisture penetrating into the cable and an excellent ability to maintain the absorption state. It is composed of powder, tape, coating layer, or film containing super absorbent polymer (SAP) and serves to prevent moisture from penetrating along the length of the cable. Additionally, the moisture absorbing portion may have semiconductivity to prevent sudden changes in electric field.

A cable protection part 20 is provided outside the cable core part 10, and a power cable laid on the sea floor may be additionally provided with a cable sheath part 30. The cable protection part and the cable sheath protect the core part from various environmental factors such as moisture penetration, mechanical trauma, and corrosion that may affect the power transmission performance of the cable.

The cable protection unit 20 includes a metal sheath 22 and a polymer sheath 24, and protects the cable from fault current, external force, or other external environmental factors.

The metal sheath 22 may be formed to surround the core portion 10. In particular, when the power cable is installed in an environment such as the seabed, the cable core portion 10 may be formed to be sealed to prevent foreign substances such as moisture from entering the cable core portion 10. By extruding molten metal to the outside of the cable core portion 10 to form a continuous outer surface without seams, excellent water protection performance can be achieved. Lead or aluminum is used as the metal. In the case of power cables laid on the seabed, it is preferable to use lead, which has excellent corrosion resistance to seawater, and alloy lead with added metal elements to supplement mechanical properties. It is more desirable 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 fault current flows in the event of an accident such as a ground fault or short circuit, protects the cable from external shock, and prevents the electric field from being discharged outside the cable. You can.

In addition, the metal sheath 22 may be coated with an anti-corrosion compound, such as blown asphalt, on the surface to further improve the corrosion resistance and water resistance of the cable and improve adhesion with the polymer sheath 24. You can.

In addition, a copper wire straight-through tape or a moisture absorption layer 21 may be additionally provided between the metal sheath 22 and the cable core portion 10. The copper wire direct-injection tape is composed of copper wire and non-woven tape and serves to facilitate electrical contact between the outer semiconducting layer 16 and the metal sheath 22, and the moisture absorption layer absorbs moisture penetrating into the cable. It is composed of a powder, tape, coating layer, or film containing super absorbent polymer (SAP), which has a high absorption speed and has excellent ability to maintain an absorbent state, and prevents moisture from penetrating along the length of the cable. It plays a role. In addition, the copper wire direct-injection tape and the moisture absorption layer preferably have semiconductivity to prevent sudden changes in the electric field, and the moisture absorption layer may be configured to include copper wire so that it can perform both current conduction and moisture absorption functions.

The polymer sheath 24 is formed on the outside of the metal sheath 22 to improve the corrosion resistance and water resistance of the cable, and to protect the cable from mechanical trauma and other external environmental factors such as heat and ultraviolet rays. You can. The polymer sheath 24 may be formed of a resin such as polyvinyl chloride (PVC), polyethylene, etc. In the case of a power cable laid on the seabed, it is preferable to use a polyethylene resin with excellent water resistance, and flame retardancy is required. In environmental environments, it is preferable to use polyvinyl chloride resin.

The power cable 100 is provided with a metal reinforcing layer 26 made of a galvanized steel cape, etc., on the inside or outside of the polymer sheath to prevent the metal sheath 22 from expanding due to expansion of the insulating oil. It can be prevented. In addition, the metal reinforcement layer 26 may be provided with a bedding layer (not shown) on the top and/or bottom of the metal reinforcement layer 26 that is made of semiconducting non-woven tape, etc. to buffer external force applied to the power cable, and may be made of polyvinyl chloride, polyethylene, etc. By further providing an external sheath 28 made of resin, the corrosion resistance and water resistance of the power cable can be further improved, and the cable can be additionally protected from mechanical trauma and other external environmental factors such as heat and ultraviolet rays.

In addition, power cables laid on the seabed are susceptible to trauma from ship anchors, etc., and can also be damaged by bending force due to ocean currents or waves, or friction with the seafloor. To prevent this, a cable sheath is installed on the outside of the cable protection unit. (30) may be additionally provided.

The cable sheath may include an armor layer 34 and a serving layer 38. The armor layer 34 is made of steel, galvanized steel, copper, brass, bronze, etc., and can be composed of at least one layer by horizontally winding a wire with a circular or square cross-sectional shape, etc., and the mechanical properties of the power cable Not only does it perform the function of enhancing performance, but it also additionally protects the cable from external forces.

The serving layer 38 made of polypropylene yarn, etc. is formed in one or more layers on the upper and/or lower part of the armor layer 34 to protect the cable, and the serving layer 34 formed on the outermost layer has a color. It is composed of two or more different materials and can ensure the visibility of cables laid on the seabed.

Figure 2 is a schematic diagram showing a junction box pressure compensation system 1000 including a junction box pressure compensation device 1100 and an end junction box 200 according to an embodiment of the present invention. In Figure 2, a portion of the terminal junction box 200 is cut away to illustrate the internal structure.

Referring to Figure 2, the terminal connection box 200 is provided with a tube 210. The air pipe 210 has a predetermined space inside, and the power cable 100 is inserted and penetrated at a predetermined length, as will be described later. The tube 210 serves to insulate and support the power cable. Therefore, the tube 210 is provided with a plurality of wrinkles or protrusions 212 along its surface in order to have sufficient electrical insulation strength. The insulation distance can be increased by the wrinkles or protrusions to prevent the insulation strength from being reduced. The tube 210 may be manufactured using hard porcelain or polymer resin in order to have dielectric strength and at the same time maintain an appropriate level of strength.

The power cable 100 passes through the tube 210, and a conductor lead-out rod 41 electrically connected to the conductor 10 of the power cable 100 protrudes by a predetermined length through the upper end of the tube 210. A corona shield 42 may be provided at the upper end of the tube 41. Each corner of the corona shield 42 is rounded to prevent corona discharge, and the conductor withdrawal rod 41 penetrates the corona shield 42 and protrudes to the outside of the tube 210.

The power cable 100 is connected to the conductor pull-out rod 41 by removing the components surrounding the conductor 10 inside the tube 210 and exposing only the conductor 10 at the end of the tube 210, The conductor withdrawal rod 41 protrudes through the corona shield 42 and is connected to an overhead line (not shown). That is, when the power cable 100 is inserted into the inner tube 210 of the termination box 200, the power cable 100 is in a state in which the cable exterior portion 30 has been removed, and the conductor 10 and internal The semiconducting layer 12, the insulating layer 14, the outer semiconducting layer 16, and the metal sheath 22 are sequentially inserted into the inner tube 210 in an exposed state. In this case, the outer semiconducting layer 16 that has not been removed is inserted into the inner tube 210 by a predetermined length. That is, the power cable 100 is inserted into the inner tube 210 with the insulating layer 14 exposed, and the outer semiconducting layer 16 is inserted into the inner tube 210 with a predetermined length.

Meanwhile, the interior of the tube 210 may be filled with insulating oil 220. The insulating oil 220 flows between the power cable 100 and the inner wall of the insulating pipe 210 inside the insulating pipe 210 to serve as electrical insulation. The method of filling the insulating oil will be discussed in detail later.

If the power cable 100 is inserted with a portion of the outer semiconducting layer 16 removed so that the insulating layer 14 is exposed, when a voltage is applied between the inner semiconducting layer and the outer semiconducting layer 16 The electric field may be concentrated at the end of . This may cause damage to the outer semiconducting layer 16 and the insulating layer 14. Therefore, as shown in the drawing, the inside of the tube 210 may be provided with an electric field relaxation cone 260 and a shielding layer 230 that alleviate the electric field concentration of the cable 100.

The shielding layer 230 is provided on the outside of the electric field mitigation cone 260 and is electrically connected to the outer semiconducting layer 16 of the cable 100 inserted into the inner tube 210. That is, even when the cable 100 is inserted into the inner tube 210 with the insulating layer 14 of the cable 100 exposed, the outer semiconducting layer 16 is inserted into the inner tube 210 by a predetermined length. . In this case, the shielding layer 230 is electrically connected to the external semiconducting layer 16 inserted into the inner tube 210. This is because the shielding layer 230 must be electrically connected to the outer semiconducting layer 16 to prevent the electric field from concentrating on the ends of the outer semiconducting layer 16. The shielding layer 230 is formed to extend a predetermined length while gently spreading in approximately the longitudinal direction within the inner tube 210. Therefore, the equipotential line is prevented from being sharply bent between the internal semiconducting layer 12 and the shielding layer 230, and the equipotential line runs between the internal semiconducting layer 12 and the shielding layer 230.

Meanwhile, the electric field relaxation cone 260 can be manufactured by wrapping insulating paper 261 and metal sheet 262 on the surface of the core 280. A plurality of metal sheets 262 are formed between the insulating paper 261 to serve as electrodes, and the electric field applied to the insulating paper 261 can be distributed at regular intervals. The inner diameter of the core 280 is formed to approximately match the core of the cable 100, that is, the outer circumference of the cable 100 where the insulating layer 14 remains. Therefore, the cable 100 is passed through the inside of the core 280 to install the core 280 and the electric field relaxation cone 260. Specifically, after wrapping the insulating paper 261 on the surface of the core 280, an electric field relaxation cone is produced through an insulating oil re-impregnation process. The weight of the electric field relaxation cone 260 manufactured through the above process is increased by the re-impregnation process of insulating oil. However, the terminal junction box 200 is generally installed in a vertical direction. Therefore, a configuration to support the electric field relaxation cone 260 and the core 280 may be required. For this purpose, the conventional termination box was equipped with a separate support means to support the electric field mitigation cone 260, but this not only complicates the configuration of the termination box, but also requires a shielding process connecting the cable and the lower part of the termination box. This served as a factor in increasing time and cost by hindering the securing of sufficient work space. Therefore, in this embodiment, a separate support means is not provided to support the electric field mitigation cone 260, and a reinforcing insulating layer 240 is provided on the outside of the cable 100 to support the electric field mitigation cone 260. I do it.

The reinforcing insulating layer 240 is provided on the outside of the insulating layer 14 of the cable 100 from which the outer semiconducting layer 16 has been removed, and serves as an insulator and supports the electric field relaxation cone 260 described above. That is, rather than simply supporting the electric field mitigation cone, insulation performance is improved by wrapping insulating paper, etc. around the outside of the insulating layer 14 of the cable 100 to form a reinforcing insulating layer 240. Accordingly, the electric field in the area where the reinforcing insulating layer 240 is formed is reduced compared to other areas.

In this case, as shown in the drawing, the reinforcing insulating layer 240 may be formed to have a predetermined inclination toward the upper part of the termination box 200, that is, the end from which the conductor 10 is drawn out, and may be formed to alleviate the electric field. The cone 260, and more specifically the core 280, may also be formed to correspond to the inclination. When manufacturing a core in response to the inclination of the reinforcing insulating layer 240, the core must also be formed to have a predetermined inclination, so it will be provided in the form of a so-called 'two-stage core' as shown in the drawing. You can.

That is, a first base portion 282 provided parallel to the insulating layer 14 of the cable 100, a second base portion 286 in close contact with the outer periphery of the reinforcing insulating layer 240, and the first base portion. An inclined portion 284 connecting the portion 282 and the second base portion 286 may be provided. The slope portion 284 is formed to correspond to the slope of the reinforcing insulating layer 240, so that when the core of the cable 100 is inserted into the electric field relaxation cone 260 and the core 280, as shown in the drawing, The electric field relaxation cone 260 and the core 280 are hung and supported on the inclined upper part of the reinforcing insulating layer 240. In this case, the thickness of the reinforcing insulating layer 240 is determined so as to improve the overall insulating performance and at the same time support the weight of the electric field relaxation cone 260. For example, the cable 100 with the insulating layer 14 exposed ) can be determined to have an outer diameter of approximately 1.5 to 2.5 times, preferably 2 times the outer diameter of the. In this case, the electric field in the area where the reinforcing insulating layer 240 is formed is reduced by approximately half compared to other areas.

The electric field mitigation cone produced by the above two-stage winding core can be applied not only to MI cables, but also to OF cables and terminal connection boxes of cables whose insulating layer is made of XLPE (Cross-linked Polyethylene).

The terminal junction box pressure compensation system 1000 according to an embodiment of the present invention includes an insulating oil pressure tank 1200 containing the insulating oil in order to fill the terminal junction box 200 having the above structure with the insulating oil, and the insulating oil. An end junction box pressure compensating device 1100 disposed between the pressure tank 1200 and the end junction box 200, and a passage for insulating oil by connecting the insulating oil pressure tank 1200 and the end junction box pressure compensating device 1100. First and second pipes (1310, 1320) providing, and a third pipe (1330) connecting the end connection box pressure compensation device (1100) and the end connection box (200) to provide a passage for insulating oil. You can.

The insulating oil pressure tank 1200 can accommodate the insulating oil. The insulating oil may be the same as the insulating oil filled in the cable and termination box 200, and the first, second, and third pipes 1310, which connect the insulating oil pressure tank 1200 and the termination box 200 to each other. It can flow between the insulating oil pressure tank 1200 and the termination box 200 through 1320 and 1330.

The insulating oil may flow into the insulating oil pressure tank 1200 or the end connection box 200 due to a difference between the pressure within the insulating oil pressure tank 1200 and the pressure within the end connection box 200. Specifically, the insulating oil pressure tank 1200 can maintain a constant pressure. As an example, the insulating oil pressure tank 1200 can maintain its internal pressure at approximately 3 bar. As the temperature of the cable connected to the termination box 200 increases, the insulating oil in the cable expands, so the pressure within the termination box 200 also increases. When the pressure within the terminal junction box 200 becomes greater than the pressure within the insulating oil pressure tank 1200, the pressure difference causes insulating oil to move from the terminal junction box 200 to the insulating oil pressure tank 1200, and the end connection When the pressure in the box 200 becomes lower than the pressure in the insulating oil pressure tank 1200, the insulating oil moves from the insulating oil pressure tank 1200 to the terminal connection box 200 due to the pressure difference.

The insulating oil contained in the insulating oil pressure tank 1200 flows into the insulating oil pressure tank 1200 or the end connection box 200 due to the difference between the pressure in the insulating oil pressure tank 1200 and the pressure in the terminal connection box 200. It can be. For example, when the power cable 100 is energized, as the temperature of the cable connected to the termination box 200 increases, the insulating oil filled in the termination box 200 expands and the insulating oil in the cable expands. As it flows into the terminal junction box, the pressure within the terminal junction box 200 also increases. If the pressure increases excessively, problems such as destruction of the cable or deformation of the cable insulation layer may occur. In addition, when the pressure in the termination box 200 becomes greater than the pressure in the insulating oil pressure tank 1200, the insulating oil moves from the termination box 200 to the insulating oil pressure tank 1200 due to the pressure difference. , when the pressure in the terminal connection box 200 becomes lower than the pressure in the insulating oil pressure tank 1200, the insulating oil moves from the insulating oil pressure tank 1200 to the terminal connection box 200 due to the pressure difference.

The insulating oil contained in the insulating oil pressure tank 1200 may flow into the insulating oil pressure tank 1200 or into the terminal connection box 200 due to the difference between the pressure within the insulating oil pressure tank 1200 and the pressure within the terminal connection box 200. You can. However, the insulating oil pressure tank 1200 may maintain a constant pressure by having a pressure buffering member therein. As an example, the insulating oil pressure tank 1200 can maintain its internal pressure at approximately 3 bar. As the temperature of the cable connected to the termination box 200 increases, the insulating oil in the cable expands, so the pressure within the termination box 200 also increases. When the pressure within the terminal junction box 200 becomes greater than the pressure within the insulating oil pressure tank 1200, the pressure difference causes insulating oil to move from the terminal junction box 200 to the insulating oil pressure tank 1200, and the end connection When the pressure in the box 200 becomes lower than the pressure in the insulating oil pressure tank 1200, the insulating oil moves from the insulating oil pressure tank 1200 to the terminal connection box 200 due to the pressure difference.

However, when the cable is energized, especially when high voltage is applied, the temperature of the cable rises to a very high temperature, and the pressure within the terminal junction box 200 may rise to tens to hundreds of bars or more. As the temperature of the cable connected to the termination box 200 increases, the insulating oil filled in the termination box 200 expands, and the insulating oil in the cable expands and flows into the termination box, thereby increasing the pressure in the termination box 200. also increases, and if the pressure increases excessively, problems such as destruction of the cable or deformation of the cable insulation layer may occur.

On the other hand, when the temperature of the cable decreases due to external environmental factors or interruption of electricity supply, the pressure in the terminal junction box 200 may be 3 bar or less or negative pressure may be partially generated. In high-voltage cables, the temperature rise of the cable is much larger than the temperature drop of the cable, so when the cable temperature rises, the amount of insulating oil moving from the terminal junction box (200) to the insulating oil pressure tank (1200) increases in the insulating oil pressure tank (1200) when the cable temperature falls. The amount of insulating oil moving from 1200) to the termination box 200 may be larger. That is, the outflow of insulating oil in the cable becomes greater than the inflow, and the insulating oil impregnated in the insulating layer of the cable leaks into the insulating oil pressure tank 1200, but does not flow into the termination box 200 as much as the outflowed insulating oil, so the insulating oil impregnated in the insulating layer of the cable A cavity may occur in the cavity, and insulation breakdown may occur in the cavity.

In the present invention, an end connection box pressure compensating device 1100 is disposed between an end connection box 200 and an insulating oil pressure tank 1200, and the end connection box pressure compensation device 1100 is connected to the end connection box 200 and the insulating oil pressure tank 1200. By controlling the flow of insulating oil between the pressure tanks 1200, excessive flow of insulating oil can be prevented, thereby preventing cavities from occurring in the insulating layer of the cable.

In more detail, the pressure compensation device 1100 blocks or allows the flow of insulating oil between the insulating oil pressure tank 1200 and the termination box 200, thereby changing the temperature of the insulating oil-impregnated cable. The pressure of the insulating oil-impregnated cable or the termination box 200 can be controlled to be within a predetermined pressure range. That is, in the pressure compensation device 1100, the temperature of the cable rises due to cable energization or the external environment, the insulating oil in the cable expands, the pressure of the termination box 200 increases, and the pressure of the termination box 200 increases. When the upper pressure value of the predetermined pressure range is reached, the first pipe 1310 between the termination box 200 and the insulating oil pressure tank 1200 may be opened. Insulating oil may flow from the terminal connection box 200, which has a relatively higher pressure, to the insulating oil pressure tank 1200 along the open first pipe 1310, and the pressure of the terminal connection box 200 is It can be lowered.

The pressure compensation device 1100 is connected from the termination box 200 to the insulating oil pressure tank 1200 after opening the first pipe 1310 between the termination box 200 and the insulating oil pressure tank 1200. When the insulating oil flows and the pressure of the terminal connection box 200 becomes less than the upper pressure value, the first pipe 1310 may be blocked.

Therefore, the present invention can prevent the pressure of the termination box 200 from increasing beyond the upper pressure value. In addition, when the pressure of the terminal connection box 200 is less than the upper pressure value, the first pipe 1310 is closed and the flow of insulating oil is blocked, and the insulating oil pressure tank 1200 is in the terminal connection box 200. ) can prevent insulating oil from leaking. That is, in the present invention, when the pressure of the termination box 200 is less than the upper pressure value, the first pipe 1310 is closed to prevent the leakage of insulating oil from the termination box 200 to the insulating oil pressure tank 1200, When the pressure of the termination box 200 exceeds the upper pressure value, the first pipe 1310 is opened to prevent the pressure in the termination box 200 from rising beyond the upper pressure value. You can.

In addition, the pressure compensation device 1100 lowers the temperature of the cable due to a power outage of the cable or the external environment, so that the insulating oil in the cable shrinks and the pressure of the terminal connection box 200 decreases. When the pressure within the insulating oil pressure tank 1200 becomes smaller, the second pipe 1320 between the terminal connection box 200 and the insulating oil pressure tank 1200 can be opened. Along the open second pipe 1320, insulating oil may flow from the insulating oil pressure tank 1200, which has a relatively higher pressure, to the termination box 200, and the pressure of the termination box 200 increases. You can. Therefore, the present invention can prevent the pressure of the termination box 200 from falling below the pressure of the insulating oil pressure tank 1200.

The pressure compensation device 1100 is connected from the insulating oil pressure tank 1200 to the terminal connection box 200 after opening the second pipe 1320 between the terminal connection box 200 and the insulating oil pressure tank 1200. When the insulating oil flows and the pressure in the termination box 200 becomes equal to or greater than the pressure in the insulating oil pressure tank 1200, the second pipe 1320 may be blocked.

Therefore, the present invention can prevent the pressure of the termination box 200 from falling below the pressure of the insulating oil pressure tank 1200. In addition, when the pressure of the terminal connection box 200 becomes greater than the pressure value of the insulating oil pressure tank 1200, the second pipe 1320 is closed and the flow of insulating oil is blocked, and the terminal connection box 200 ) can prevent insulating oil from leaking into the insulating oil pressure tank 1200. That is, in the present invention, when the pressure of the termination box 200 is greater than the pressure of the insulating oil pressure tank 1200, the second pipe 1320 is closed to allow the connection from the termination box 200 to the insulating oil pressure tank 1200. It is possible to prevent insulating oil from leaking, and when the pressure of the termination box 200 falls below the pressure of the insulating oil pressure tank 1200, the second pipe 1320 is opened to reduce the pressure in the termination box 200. It is possible to prevent the pressure from falling below the pressure of the insulating oil pressure tank 1200.

Figure 3 is a diagram showing a terminal junction box pressure compensation device 1100 according to an embodiment of the present invention.

Referring to FIG. 3, the end connection box pressure compensation device 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 termination box 200 exceeds a preset pressure value to allow insulating oil to flow from the termination box 200 to the insulating oil pressure tank 1200. can do. When the pressure of the terminal connection box 200 decreases and becomes lower than the pressure of the insulating oil pressure tank 1200, the second valve 1120 is opened and moves from the insulating oil pressure tank 1200 to the terminal connection box 200. ) can allow the insulating oil to flow.

More specifically, when the insulating oil-impregnated cable is energized or a change in the external environment causes the temperature of the insulating oil in the cable to rise, the first valve 1110 expands the insulating oil, thereby connecting the ends (200). When the pressure inside the terminal connection box 200 increases and the pressure inside the termination box 200 exceeds the preset pressure value, it is opened, and the insulating oil pressure is maintained at a pressure lower than the preset pressure value in the termination box 200. The insulating oil may flow into the tank 1200.

When the pressure of the terminal connection box 200 becomes lower than the preset pressure value after the insulating oil flows into the insulating oil pressure tank 1200, the first valve 1110 is closed and the terminal 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 terminal connection box 200 exceeds the pressure already set in the first valve 1110. The first valve 1110 may be a relief valve, for example.

The second valve 1120 is operated by cooling and shrinking the insulating oil in the cable due to a power outage of the cable or a change in the external environment, thereby lowering the pressure in the termination box 200, thereby increasing the pressure in the termination box 200. It opens when the pressure of the insulating oil pressure tank 1200 becomes smaller than the pressure of the insulating oil pressure tank 1200, and the insulating oil flows from the insulating oil pressure tank 1200, which maintains a constant pressure, to the terminal connection box 200. After the insulating oil flows, When the pressure of the terminal connection box 200 is equal to or becomes greater than the pressure of the insulating oil pressure tank 1200, the second valve 1120 is closed and the terminal connection box 200 is closed in the insulating oil pressure tank 1200. ), the insulating oil may not flow.

That is, the second valve 1120 is disposed between the end connection box 200 and the insulating oil pressure tank 1200 and is generally closed, but the pressure within the end connection box 200 is generally constant. It may be opened when the pressure of the insulating oil pressure tank 1200 is lower than that maintained. When the second valve 1120 is opened, insulating oil may flow from the insulating oil pressure tank 1200, which has a higher pressure than the pressure of the second valve 1120, to the terminal connection box 200. The insulating oil flows from the terminal connection box 200 to the insulating oil pressure tank 1200 through the second valve 1120 opened by the pressure difference between the terminal connection box 200 and the insulating oil pressure tank 1200. The pressure of the terminal connection box 200 and the insulating oil pressure tank 1200 becomes the same, or the temperature of the cable 100 rises due to energization of the cable 100 or external factors, and the terminal connection is connected. When the temperature and pressure of the insulating oil in the box 200 or the cable 100 rises, the second valve 1120 is closed, and the connection between the termination box 200 and the insulating oil pressure tank 1200 is closed. Insulating oil does not flow. The second valve may be a check valve, for example.

Figure 4 is a flowchart showing a method for compensating pressure in an end junction box according to an embodiment of the present invention.

Referring to FIG. 4, the end connection box pressure compensation method according to an embodiment of the present invention first, when the pressure of the end connection box 200 exceeds the preset pressure value of the first valve 1110, The first valve 1110 disposed between the connection box 200 and the insulating oil pressure tank 1200 is opened so that insulating oil can flow from the terminal connection box 200 to the insulating oil pressure tank 1200 ( S101).

When the insulating oil-impregnated cable is energized or due to a change in the external environment, the temperature of the insulating oil in the cable rises, causing the insulating oil to expand, and accordingly, the pressure in the termination box 200 increases, thereby increasing the pressure in the termination box 200. When the pressure exceeds the preset pressure value of the first valve 1110, the first valve 1110 is opened, and the pressure difference between the terminal connection box 200 and the insulating oil pressure tank 1200 causes the first valve 1110 to open. Insulating oil may flow from the terminal junction box 200 to the insulating oil pressure tank 1200.

After the first valve 1110 is opened and the insulating oil flows from the termination box 200 to the insulating oil pressure tank 1200, the pressure of the termination box 200 becomes less than the preset pressure value. In this case, the first valve 1110 is closed (S102).

As described above, after the first valve 1110 is opened, insulating oil may flow from the terminal junction box 200, which has a higher pressure, to the insulating oil pressure tank 1200, which has a lower pressure.

After the first valve 1110 is opened, the pressure of the terminal junction box 200 through which insulating oil flows out continues to decrease. However, due to its nature, the insulating oil pressure tank 1200 maintains a constant pressure even when insulating oil flows into it. The pressure of the terminal connection box 200 decreases due to the outflow of insulating oil, and when the pressure reaches the pressure that opens the first valve 1110, that is, the preset pressure value, the first valve 1110 It is closed, and the flow of insulating oil between the termination box 200 and the insulating oil pressure tank 1200 may be stopped.

When the pressure of the termination box 200 decreases and becomes lower than the pressure of the insulating oil pressure tank 1200, a second valve 1120 is disposed between the termination box 200 and the insulating oil pressure tank 1200. ) is opened so that the insulating oil can flow from the insulating oil pressure tank 1200 to the terminal connection box 200 (S103).

In detail, when the temperature of the insulating oil in the cable decreases due to a power outage of the cable or a change in the external environment, the insulating oil shrinks and the pressure of the cable and the terminal junction box 200 decreases. When the pressure within the terminal junction box 200 decreases and the pressure of the terminal junction box 200 becomes lower than the pressure of the insulating oil pressure tank 1200, the second valve 1120 may be opened. Insulating oil may flow from the insulating oil pressure tank 1200 to the terminal connection box 200 due to the pressure difference.

After the second valve 1120 is opened and the insulating oil flows from the insulating oil pressure tank 1200 to the termination box 200, the pressure of the termination box 200 increases with the insulating oil pressure tank 1200. When the pressure is equal to or increases, the second valve 1120 is closed (S104).

As described above, after the second valve 1120 is opened, insulating oil may flow from the insulating oil pressure tank 1200, which has a higher pressure, to the termination box 200, and the termination into which the insulating oil flows The pressure of the junction box 200 increases. However, due to its nature, the insulating oil pressure tank 1200 maintains a constant pressure even when insulating oil flows into it. The pressure of the terminal connection box 200 increases due to the inflow of insulating oil, and when the pressure becomes equal to or greater than the pressure of the insulating oil pressure tank 1200, the second valve 1120 is closed, and the terminal connection box 200 is closed. The flow of insulating oil between the box 200 and the insulating oil pressure tank 1200 may be stopped.

According to an embodiment of the present invention, when the pressure of the terminal connection box 200 exceeds the preset pressure value, the first valve 1110 is opened and the terminal connection box 200 By flowing insulating oil into the insulating oil pressure tank 1200, the pressure of the termination box 200 can be prevented from increasing, and the pressure of the termination box 200 is lower than the pressure of the insulating oil pressure tank 1200. In this case, the second valve 1120 is opened and insulating oil flows from the insulating oil pressure tank 1200 to the terminal connection box 200, thereby preventing the pressure of the terminal connection box 200 from becoming very low. . In addition, when the pressure of the terminal connection box 200 is between the preset pressure value of the first valve 1110 and the pressure of the insulating oil pressure tank 1200, the first valve 1110 and the second valve 1120 is closed to prevent leakage of insulating oil in the terminal junction box 200, preventing the insulating oil impregnated in the insulating layer of the cable connected to the terminal junction box 200 from leaking out, creating a cavity, and resulting in insulation breakdown. It can be prevented.

The above description is merely an illustrative explanation of the technical idea of the present invention, and various modifications and variations will be possible to those skilled in the art without departing from the essential characteristics of the present invention.

Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but are for illustrative purposes, 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 interpreted in accordance with the claims below, and all technical ideas within the equivalent scope should be construed as being included in the scope of rights of the present invention.

10..Conductor
100..power cable
200..End connection box
210..Aegwan
220..Insulating oil
260..Electric field relaxation cone
1100..Pressure compensation device
1200..Insulating oil pressure tank

Claims (20)

In the terminal junction box pressure compensation device disposed between the terminal junction box connected to the end of the insulating oil impregnated cable and the insulating oil pressure tank,
The pressure compensation device is,
The pressure of the insulating oil-impregnated cable or the termination box varies depending on the temperature change of the insulating oil-impregnated cable by flowing or blocking insulating oil from the insulating oil pressure tank to the termination box, or from the termination box to the insulating oil pressure tank. Control it to be within this predetermined pressure range,
When the pressure of the termination box increases and reaches the upper pressure value of a predetermined pressure range, the pipe between the termination box and the insulating oil pressure tank is opened to allow the insulating oil to flow from the termination box to the insulating oil pressure tank. thereby preventing the pressure of the terminal connection box from exceeding the upper pressure value,
After opening the pipe between the termination box and the insulating oil pressure tank, if the insulating oil flows from the termination box to the insulating oil pressure tank and the pressure of the termination box becomes less than the upper pressure value, blocking the pipe Features a termination box pressure compensation device. delete delete According to paragraph 1,
The pressure compensation device is,
When the pressure of the termination box decreases and the pressure of the termination box becomes lower than the pressure in the insulating oil pressure tank, the pipe between the termination box and the insulating oil pressure tank is opened and the termination is connected in the insulating oil pressure tank. An end junction box pressure compensation device, characterized in that it prevents the pressure of the end junction box from falling below the lower limit pressure value of the predetermined pressure range by allowing insulating oil to flow. According to paragraph 4,
The pressure compensation device is,
After opening the pipe between the end connection box and the insulating oil pressure tank, if the insulating oil flows from the insulating oil pressure tank to the end connection box and the pressure of the end connection box becomes equal to or greater than the pressure in the insulating oil pressure tank, the pipe is blocked. An end junction box pressure compensation device, characterized in that. According to paragraph 1,
The pressure compensation device is,
When the pressure of the termination box reaches the upper pressure value, a first valve opens to allow insulating oil to flow from the termination box to the insulating oil pressure tank; and
When the pressure of the terminal connection box decreases and becomes lower than the pressure of the insulating oil pressure tank, a second valve opens to allow the insulating oil to flow from the insulating oil pressure tank to the terminal connection box; An end junction box pressure compensation device comprising a. According to clause 6,
The first valve opens when the insulating oil-impregnated cable is energized, the insulating oil expands due to a rise in temperature of the insulating oil, and the pressure in the termination box increases, and the pressure in the termination box reaches the upper pressure value. And, the insulating oil flows from the terminal connection box to the insulating oil pressure tank that maintains a pressure lower than the preset pressure value,
When the pressure of the termination box becomes lower than the upper pressure value after the flow of the insulating oil, the first valve is closed so that the insulating oil does not flow from the termination box to the insulating oil pressure tank. Compensation device. According to clause 6,
An end connection box pressure compensation device, wherein the first valve is a relief valve. According to clause 6,
The second valve is opened when the pressure in the terminal connection box decreases as the insulating oil cools and contracts, and the pressure in the terminal connection box becomes lower than the pressure of the insulating oil pressure tank, and the insulating oil pressure is maintained at a constant pressure. The insulating oil flows from the tank to the terminal connection,
When the pressure of the termination box 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 so that the insulating oil does not flow from the insulating oil pressure tank to the termination box. Termination box pressure compensation device. According to clause 6,
The end connection box pressure compensation device, characterized in that the second valve is a check valve. In the pressure compensation system of the termination box connected to the end of the insulating oil-impregnated cable,
an insulating oil pressure tank containing insulating oil;
When the pressure of the termination box reaches the upper pressure value of a predetermined pressure range, it is opened to allow insulating oil to flow from the termination box to the insulating oil pressure tank and the pressure of the termination box becomes lower than the upper pressure value. a first valve that is closed to prevent the insulating oil from flowing from the end connection box to the insulating oil pressure tank; and
When the pressure of the terminal connection box decreases and becomes lower than the pressure of the insulating oil pressure tank, a second valve opens to allow the insulating oil to flow from the insulating oil pressure tank to the terminal connection box; An end junction box pressure compensation system comprising: delete According to clause 11,
An end connection box pressure compensation system, wherein the first valve is a relief valve. According to clause 11,
The second valve is opened when the pressure in the terminal connection box decreases as the insulating oil cools and contracts, and the pressure in the terminal connection box becomes lower than the pressure of the insulating oil pressure tank, and the insulating oil pressure is maintained at a constant pressure. The insulating oil flows from the tank to the terminal connection,
When the pressure of the termination box 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 so that the insulating oil does not flow from the insulating oil pressure tank to the termination box. Junction box pressure compensation system. According to clause 11,
The end junction box pressure compensation system, characterized in that the second valve is a check valve. In a method of compensating the pressure of the terminal junction box, which is connected to an insulating oil pressure tank and placed at the end of an insulating oil-impregnated cable, by filling the terminal junction box with insulating oil,
When the pressure of the termination box reaches the upper pressure value of a predetermined pressure range, the first valve disposed between the termination box and the insulating oil pressure tank is opened to allow insulating oil to flow from the termination box to the insulating oil pressure tank. flowing step;
When the insulating oil flows from the termination box to the insulating oil pressure tank and the pressure of the termination box becomes less than the upper pressure value, closing the first valve;
When the pressure of the termination box decreases and becomes lower than the pressure of the insulating oil pressure tank, the second valve disposed between the termination box and the insulating oil pressure tank is opened and the insulating oil flows from the insulating oil pressure tank to the termination. flowing step; and
When the insulating oil flows from the insulating oil pressure tank to the termination box and the pressure of the termination box becomes equal to or greater than the pressure of the insulating oil pressure tank, closing the second valve; An end junction box pressure compensation method comprising: delete According to clause 16,
An end connection box pressure compensation method, wherein the first valve is a relief valve. According to clause 16,
The second valve is opened when the pressure in the terminal connection box decreases as the insulating oil cools and contracts, and the pressure in the terminal connection box becomes lower than the pressure of the insulating oil pressure tank, and the insulating oil pressure is maintained at a constant pressure. The insulating oil flows from the tank to the terminal connection,
When the pressure of the termination box 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 so that the insulating oil does not flow from the insulating oil pressure tank to the termination box. Termination box pressure compensation method. According to clause 16,
An end connection box pressure compensation method, wherein the second valve is a check valve.

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