KR102230586B1 - Oil supply system of joint box for oil impregnated cable - Google Patents

Abstract

The present invention provides an oil supply system for lubricating a junction box to which an insulating oil-impregnated cable is connected with the insulating oil, the inlet pipe connected to the metal sheath forming the junction box to provide a passage for the insulating oil, and the inlet pipe. An insulating oil supply part receiving the insulating oil supplied to the inlet pipe and a pressurizing part applying a predetermined pressure to the inside of the junction box through the inlet pipe, wherein the inlet pipe has an inner diameter that varies according to the kinematic viscosity of the insulating oil. do.

Description

Oil supply system of joint box for oil impregnated cable}

The present invention relates to a junction box lubrication system for an insulating oil-impregnated cable, and specifically, in order to improve the insulation performance of the junction box for connecting the insulating oil-impregnated cable when the insulating oil-impregnated cables are connected to each other or the insulating oil-impregnated cable is connected to an overhead line. It relates to a junction box lubricating system capable of lubricating the junction box with low viscosity insulating oil or high viscosity insulating oil.

In general, a power cable is used to supply power to a desired place through the ground, the ground, or the seabed by using a conductor that supplies power. It is very important for such a power cable to insulate the conductor, and for this purpose, the insulating layer that insulates the conductor is made of XLPE (cross-linked polyethylene) or the like, or wrapped with insulating paper as an insulating layer. I'm using it.

Depending on the viscosity of the insulating oil to be used, the so-called'low-viscosity insulating oil-impregnated cables' (hereinafter referred to as OF (oil filled) cables) and'high-viscosity insulating oil-impregnated cables' (hereinafter, referred to as "Oil filled) cables" are based on the viscosity of the insulating oil. , MI (mass impregnated) cable).

OF cable is impregnated with insulating paper using relatively low viscosity insulating oil, and the length of extension is limited because it must be operated while maintaining the hydraulic pressure at a certain level by pressurizing the insulating oil. On the contrary, since the insulating paper is impregnated with insulating oil of relatively high viscosity, the MI cable has the advantage of having a long extension length since there is little flow of insulating oil in the insulating paper, so there is no need to maintain hydraulic pressure.

Meanwhile, the power cable is connected by a joint box at intervals of several hundred m or tens of kilometers, and the ends of the power cable are connected by a termination box. When connecting a power cable from the intermediate junction box or the terminal junction box, first connect a conductor while the insulation layer of the cable is exposed, and roll an insulating paper impregnated with high viscosity insulating oil on the surface of the insulating layer to form a reinforcing insulating layer. . In this case, the insulating paper is rolled while the insulating paper is being wound, that is, while insulating oil is applied between the insulating papers, and then the outer semiconducting layer, the metal sheath and/or the anticorrosive layer are restored.

In the case of connecting an insulating oil-impregnated cable as described above, the pressure inside the cable and junction box according to changes in the external environment such as seasonal changes is kept constant, and the insulation performance of the junction box is prevented from deteriorating, and further insulation performance. In order to improve the quality, insulating oil is lubricated into the junction box. For example, in the case of OF cables, a cable impregnated with low viscosity insulating oil is used, so when the OF cables are connected to each other, the junction box is lubricated using the same low viscosity insulating oil as the insulating oil of the OF cable. .

However, in the case of the MI cable, as described above, a high viscosity insulating oil having a relatively high viscosity is used to impregnate it. Since the high-viscosity insulating oil has a relatively high viscosity and low fluidity, it is difficult to lubricate the high-viscosity insulating oil when the insulating oil is lubricated in the junction box. Therefore, the junction box for the MI cable was lubricated using a low viscosity insulating oil, not the high viscosity insulating oil used for the cable. Eventually, the junction box for the MI cable is lubricated by using a low viscosity insulating oil different from the insulating oil used in the MI cable, so it must be lubricated with a low viscosity insulating oil compatible with the insulating oil used in the cable. There is a limitation in assembling the junction box, resulting in inconvenience.

Korean Patent Application No. KR 10-2010-0100098 (Registration No. 10-1108309 announced on January 25, 2012)

An object of the present invention is to provide a junction box lubricating system capable of lubricating the same low-viscosity insulating oil or high-viscosity insulating oil as the cable when lubricating a junction box connecting an insulating oil-impregnated cable to each other with insulating oil.

An object of the present invention as described above is in a lubrication system for lubricating a junction box to which an insulating oil-impregnated cable is connected with the insulating oil, an inlet pipe connected to a metal sheath forming the junction box to provide a passage for the insulating oil to move, the An insulating oil supply unit connected to an inlet pipe and receiving the insulating oil supplied to the inlet pipe, and a pressurizing unit applying a predetermined pressure to the inside of the junction box through the inlet pipe, the inlet pipe has an inner diameter according to the kinematic viscosity of the insulating oil. This is achieved by a junction box lubrication system for an insulating oil-impregnated cable, characterized in that it varies.

Here, the inner diameter of the inlet pipe is determined as the first inner diameter when the kinematic viscosity of the insulating oil is from 40 to 4 to 5 cSt and represents a value of from 1 to 2 cSt from 100, and the kinematic viscosity of the insulating oil is from 40 to 4000 to 6000 cSt, and is determined as a second inner diameter in the case of representing a value of from 100 to 180 to 220 cSt, and the second inner diameter may be 4 times or more than the first inner diameter. In addition, the inlet pipe has an inner diameter of 10 mm when the kinematic viscosity of the insulating oil is from 40 to 4 to 5 cSt and the value of from 100 to 1 to 2 cSt, and the kinematic viscosity of the insulating oil is from 40 to 4000 to 6000 cSt, In the case of representing a value of 100 to 180 to 220 cSt, it may have an inner diameter of 40 mm.

Further, the oil supply system is provided in the opposite direction of the inlet pipe along the metal sheath, and is connected to the discharge pipe through which the insulating oil is discharged, the discharge pipe to maintain the interior of the junction box in a vacuum state, and the discharge pipe. It may be further provided with a vacuum measuring unit for sensing the degree of vacuum of the junction box.

According to the present invention described above, in the connection between the insulating oil-impregnated cables connected to each other or to the overhead line, in order to improve the insulation performance of the junction box, the junction box is made of the same high-viscosity insulating oil or low-viscosity insulating oil as the cable. Can be fueled. Therefore, according to the present invention, in the case of installing the junction box, it is possible to install it relatively easily and within a short time, and furthermore, since the same type of insulating oil as the insulating oil-impregnated cable is used, the overall insulation performance of the cable and junction box is improved. Can be expected.

In addition, according to the present invention, the oil supply system used in the junction box connecting the OF cables can be utilized as the oil supply system of the junction box for MI cables, so that the junction box for the MI cable can be quickly and easily oiled with high viscosity insulating oil without additional equipment investment. I can.

1 is a partially cut-away perspective view showing the configuration of an insulating oil-impregnated cable according to an embodiment,
2 is a partially cut-away perspective view showing the configuration of an insulating oil-impregnated cable according to another embodiment,
3 is a schematic diagram showing the configuration of a lubrication system for lubricating a junction box when insulating oil-impregnated cables are connected to each other;
4 is a graph showing a movement amount of insulating oil lubricated to the connection box through the inlet pipe according to a change in the inner diameter of the inlet pipe;
5 is a graph showing the internal pressure of the pressure tank over time when pressure tanks having different internal pressures are connected to the inlet pipe.

Hereinafter, exemplary 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 so that the disclosed content may be thorough and complete, and the spirit of the present invention may be sufficiently conveyed to those skilled in the art. The same reference numbers throughout the specification indicate the same elements.

In general, the insulating oil-impregnated cable is connected by intermediate connection at intervals of several hundred m to several kilometers, and the end of the insulating oil-impregnated cable is connected to the overhead line by terminating. In the following, first, a configuration of an insulating oil-impregnated power cable will be described, followed by a connection process of a junction box.

1 is a partially cut-away perspective view showing the internal configuration of an insulating oil-impregnated cable 100 according to an embodiment.

Referring to FIG. 1, the insulating oil-impregnated cable 100 includes a conductor 10 along a central portion. The conductor 10 serves as a path through which current flows. As shown in the drawing, the conductor 10 may include a circular center element line 10A and a flat angle element line layer 10C made of a flat element line 10B stranded to surround the center element line 10A. The flat angle element wire layer 10C is formed by forming a cross section of a plurality of flat angle element wires 10B in a rectangular shape through a continuous extrusion process, and twisting the plurality of square element wires 10B on the center element line 10A. The conductor 10 is manufactured to have a circular shape as a whole. Although not shown in the drawings, the conductor 10 may be provided by twisting a plurality of circular wires. However, the conductor made of the square element wire has a relatively higher dot ratio compared to the conductor made of the circular element wire, and thus may be suitable for a high voltage power cable.

However, since the surface of the conductor 10 is not smooth, the electric field may be uneven, electric field concentration may occur, and corona discharge may occur partially. In addition, when a void is formed between the surface of the conductor 10 and the insulating layer 14 to be described later, the insulating performance is deteriorated. In order to solve the above problems, the outside of the conductor 10 is wrapped with a semiconductive material such as semiconductive carbon paper, and a layer formed of the semiconductive material is defined as the inner semiconducting layer 12.

As a result, the inner semiconductor layer 12 prevents partial discharge caused by electric field relaxation on the surface of the conductor 10 and voids between the conductor 10 and the insulating layer 14. In addition, the inner semiconducting layer 12 maintains the ideal concentric cylindrical electrode shape in the cable, smoothes the surface of the conductor 10 to relieve the electric field concentration, and makes the conductor 10 and the insulating layer 14 in close contact with each other. Corona discharge that may occur on the surface of the conductor 10 can be prevented. Furthermore, impurities may be adsorbed by preventing electron injection and electron flow between the conductor 10 and the inner semiconductor layer 12 and between the inner semiconductor layer 12 and the insulating layer 14.

Meanwhile, an insulating layer 14 is provided outside the inner semiconductor layer 12. The insulating layer 14 electrically insulates the conductor 10 from the outside. In general, the insulating layer 14 has a high breakdown voltage, and the insulating performance must be stably maintained for a long period of time. Furthermore, it should have low dielectric loss and have resistance to heat such as heat resistance. In this embodiment, the insulating layer 14 is formed through a ground insulating process in which insulating paper is wound around the surface of the inner semiconducting layer 12. In addition, in order to improve the insulating properties, the insulating paper is impregnated with insulating oil while the insulating paper is wound around the surface of the conductor 10. Insulating oil is absorbed into the insulating paper through the impregnation process, and when high-viscosity insulating oil is used as in this embodiment, it is defined as a'mass impregnated (MI) cable', and when relatively low-viscosity insulating oil is used,'OF (oil) is used. filled) cable.

In this embodiment, the insulating layer 14 is formed by wrapping a plurality of insulating papers, and may be formed by repeatedly wrapping a thermoplastic resin such as kraft paper and polypropylene resin.

Specifically, an insulating layer may be formed by winding an insulating paper having a structure in which kraft paper is stacked on the upper and lower surfaces of a composite insulating paper, for example, a polypropylene resin.

In the case of a MI cable that is wound with only kraft and impregnated with insulating oil, when the cable is operated (when energized), the current flowing through the cable conductor causes the inner side in the radial direction, that is, the outer side in the radial direction from the part of the insulating layer in the direction of the inner semiconducting layer. That is, a temperature difference occurs in the portion of the insulating layer in the direction of the outer semiconducting layer, which will be described later. Therefore, the insulating oil of the insulating layer on the side of the inner semiconducting layer, which is higher temperature, has a lower viscosity and thermally expands to move to the insulating layer on the side of the outer semiconductor layer. As it does not return, bubbles are generated in the radial direction inward, that is, in the insulating layer portion toward the inner semiconducting layer, resulting in a decrease in insulating performance.

However, when the insulating layer is formed with a composite insulating paper as described above, a thermoplastic resin such as polypropylene resin, which is not impregnated with oil during cable operation, thermally expands to suppress the flow of insulating oil, and the polypropylene resin is Since the insulation resistance is greater than that of kraft paper, even if bubbles are generated, the voltage shared by the bubbles can be reduced.

In addition, since the polypropylene resin is not impregnated with the insulating oil, it is possible to suppress the flow of the insulating oil in the diameter direction of the cable due to gravity. Since the surface pressure is applied to the kraft paper by thermal expansion, the flow of insulating oil can be further suppressed.

Composite insulating paper is laminated of kraft paper on one side of a thermoplastic resin such as polypropylene resin, a thermoplastic resin such as polypropylene resin is laminated on the top and bottom of kraft paper, or four layers of thermoplastic resin such as kraft paper and polypropylene resin are alternately stacked The above laminated ones can be used, and the effects and effects in this case are the same as in the case of the insulating paper having a structure in which kraft paper is laminated on the upper and lower surfaces of the polypropylene resin.

In addition, the insulating layer 14 is formed by winding the composite insulating paper, but any one or both surfaces of the surface in contact with the inner semiconducting layer 12 and the surface in contact with the outer semiconducting layer 16 may be formed of kraft paper. , Preferably, both the surface in contact with the inner semiconducting layer 12 and the surface in contact with the outer semiconducting layer 16 may be formed by winding kraft paper.

In this case, since kraft paper, which has a lower resistivity than composite insulating paper, is formed on one or both sides of the surface in contact with the inner semiconducting layer 12 or the outer semiconducting layer 16 of the insulating layer, Even if bubbles are generated in a portion where the inner semiconducting layer contacts or the portion where the insulating layer and the outer semiconducting layer come in contact, the impulse fracture characteristics can be prevented from deteriorating by the electric field relaxation effect of the kraft paper layer. Further, since kraft paper has little polarity effect on impulse destruction, the impulse polarity effect generated by using plastic laminate paper can be reduced.

By the way, if the outside as well as the inside of the insulation layer 14 is not shielded, a part of the electric field is absorbed by the insulation layer 14, but most of the electric field is discharged to the outside. In this case, when the electric field becomes larger than a predetermined value, the insulating layer 14 and the outer shell of the cable 100 may be damaged by the electric field. Accordingly, a semiconducting layer is provided outside the insulating layer 14 again, and is defined as an outer semiconducting layer 16 to distinguish it from the above-described inner semiconducting layer 12. The outer semiconducting layer 16 serves to protect the insulating layer 14 by suppressing electric field inequality due to variations in insulation thickness, and the distribution of electric line of force between the inner semiconducting layer 12 and the above-described inner semiconducting layer 12 is made to be an insulating layer. It plays a role of improving the dielectric strength of (14). In addition, the outer semiconducting layer 16 smoothes the surface of the insulating layer 14 in the cable to alleviate electric field concentration, thereby preventing corona discharge.

On the other hand, the outer semiconducting layer 16 is provided with a copper wire straight tape 18, and further, the insulating oil or the insulating compound impregnated in the insulating layer decreases the insulating performance when foreign substances such as external water enters. Therefore, in order to prevent this, a metal sheath made of lead, a so-called'soft sheath' 20, is provided on the outside of the copper wire direct-attached tape 18.

Further, a bedding layer 22 is provided on the outside of the metal sheath 20 to prevent direct contact with water. A nonwoven tape 24 and a reinforcing tape 26 are wrapped on the bedding layer 22, and a jacket 32 is provided on the outer periphery of the cable 100 as an exterior of the cable. The jacket 32 is provided outside the cable 100 and serves to protect the internal structure of the cable 100. The jacket 32 may be made of, for example, polyethylene (PE) so as to have excellent properties in weather resistance and mechanical strength capable of withstanding various environments.

2 is a partially cut-away perspective view showing the internal configuration of an insulating oil-impregnated cable 100 according to another embodiment. The cable according to FIG. 2 shows a configuration of a power cable that can be used as a so-called submarine cable for connecting land via sea, for example. Compared with the embodiment of FIG. 1 described above, the differences will be mainly looked at.

Referring to FIG. 2, an insulating oil-impregnated cable 100 used as a submarine cable includes a wire sheath 30 surrounding a wire for increasing mechanical strength so as to report the cable from the external environment of the seabed at the outer edge of the cable 100. Will be equipped. Specifically, the outer wire 30 is provided on the outer periphery of the reinforcing tape 26 in the embodiment of FIG. 1 described above, or a non-woven tape (not shown) is re-wound on the outer periphery of the reinforcing tape 26 and the wire An exterior 30 may be provided.

The outer periphery of the wire outer 30, that is, the outer periphery of the cable 100, is provided with a jacket 32 as an outer outer of the cable. The jacket 32 is provided on the outer periphery of the insulating oil-impregnated cable 100 and serves to protect the internal structure of the cable 100. In particular, in the case of a submarine cable, the jacket 32 has excellent weather resistance and mechanical strength capable of withstanding a submarine environment such as seawater. For example, the jacket 32 may be made of polypropylene yarn or the like.

3 shows a junction box 200 for connecting the insulating oil-impregnated cables 100A and 100B having the above configuration and a junction box lubrication system 300 for lubricating the junction box 200 with insulating oil. It is a schematic diagram.

Referring to FIG. 3, first, the conductor 10A of the insulating oil-impregnated cables 100A and 100B in a state in which the insulating layers 14A and 14B and the conductors 10A and 10B are exposed in a pair of insulating oil-impregnated cables 100A and 100B. , 10B) are electrically connected to each other (11). After connecting the respective conductors of the insulating oil-impregnated cables 100A and 100B, a reinforcing insulating layer 240 is formed to surround at least a part of the insulating layers 14A and 14B including the connecting portion of the conductor 10.

In this embodiment, the reinforcing insulating layer 240 is formed by rolling an insulating paper impregnated with insulating oil on the insulating layer 14 including the connecting portion of the conductor 10. In this case, the insulating paper may be rolled in a state already impregnated with the insulating oil, or may be rolled after draining the insulating paper impregnated with the insulating oil.

Subsequently, the outer semiconducting layer 16 and the metal sheath 20 are restored on the reinforcing insulating layer 240.

In the structure of the junction box having the above configuration, the reinforcing insulating layer 240 is impregnated with insulating oil, but when air bubbles or impurities enter between the insulating oil, the overall insulation performance of the junction box is reduced. Can result. Therefore, hereinafter, a junction box lubrication system for preventing the above-described deterioration of the insulation performance and further improving the overall insulation performance will be described.

The junction box lubrication system 300 is provided in the metal sheath 20 forming the junction box 200 and is connected to the inlet pipe 310 and the inlet pipe 310 to provide a passage through which the insulating oil moves. The insulating oil supply unit 340 in which the insulating oil supplied to the inlet pipe 310 is accommodated, a pressurizing unit 350 for applying a predetermined pressure to the inside of the junction box 200 through the inlet pipe 310, and the metal sheath 20 A vacuum pump provided in the opposite direction of the inlet pipe 310 and connected to the discharge pipe 330 through which the insulating oil is discharged and the discharge pipe 330 to maintain the interior of the junction box 200 in a vacuum state ( 360) and a vacuum measuring unit 370 connected to the discharge pipe 330 to detect the degree of vacuum of the junction box 200.

The metal sheath 20 may be provided with an inlet pipe 310 and an outlet pipe 330. The inlet pipe 310 and the discharge pipe 330 provide a passage through which insulating oil, which will be described later, moves. The inlet pipe 310 and the discharge pipe 330 are formed in opposite directions along the outer periphery of the metal sheath 20. That is, a pair of pipes are formed in opposite directions along the outer periphery of the metal sheath 20, and then a pipe (or a pipe in the direction of gravity) from the metal sheath 20 toward the ground is introduced into the inlet pipe 310. In the metal sheath 20, a pipe located in a direction opposite to the inlet pipe 310 (a pipe facing the direction opposite to the gravity direction) may be defined as the discharge pipe 330.

The inlet pipe 310 and the discharge pipe 330 may be configured to pass through the metal sheath 20 and communicate with the outer semiconducting layer 16 and the reinforcing insulating layer 240. Therefore, as described later, when the insulating oil is injected through the inlet pipe 310, the injected insulating oil impregnates the reinforcing insulating layer 240 through the outer semiconducting layer 16 and through the discharge pipe 330 at the top. It is discharged to the outside. This will be described in detail later.

The inlet pipe 310 may be connected to an insulating oil supply unit 340 containing an insulating oil or an insulating compound for re-impregnating the reinforcing insulating layer 240. The insulating oil supply unit 340 may be formed of, for example, a pressure tank accommodating insulating oil. The inlet pipe 310 may be provided with a first valve 312 that selectively blocks the supply of the insulating oil supplied from the insulating oil supply unit 340. The insulating oil supplied into the metal sheath 20 may be selectively blocked by the operation of the first valve 312.

On the other hand, the inlet pipe 310 may be further provided with a pressing portion 350 for applying a predetermined pressure toward the inside of the metal sheath 20 through the inlet pipe 310. The pressurizing unit 350 may be configured with, for example, a pump. Whether or not the pressurizing part 350 is pressurized through the second valve 314 is determined. That is, as the second valve 314 is opened or closed, the pressure applied by the pressing unit 350 can be adjusted.

However, as described above, in the junction box lubricating system using low-viscosity insulating oil, the inner diameter of the inlet pipe is provided relatively small, for example, the inner diameter is determined to be approximately 10 mm. However, the inlet pipe having the inner diameter as described above can be sufficiently used for the flow of low-viscosity insulating oil, but is not suitable for the flow of high-viscosity insulating oil. In particular, in the case of connecting MI cables to each other and using high viscosity insulating oil instead of low viscosity insulating oil in the junction box, the high viscosity insulating oil has a relatively high viscosity, so its fluidity is very low. It is difficult to lubricate high-viscosity insulating oil into the junction box.

For example, the kinematic viscosity of the low-viscosity insulating oil for OF cables is approximately 4 to 5 cSt at 40, and represents a value of approximately 1 to 2 cSt at 100. On the other hand, the kinematic viscosity of the high-viscosity insulating oil for the MI cable is approximately 4000 to 6000 cSt at 40, and represents a value of approximately 180 to 220 cSt at 100. As a result, it can be seen that the kinematic viscosity of the high viscosity insulating oil is relatively high at the same temperature compared to the low viscosity insulating oil, which means that the flow resistance of the high viscosity insulating oil is much higher. Accordingly, in the junction box lubrication system 300 according to the present embodiment, the inner diameter of the inlet pipe 310 may be set differently according to the kinematic viscosity of the insulating oil.

That is, in the case of a cable impregnated with low-viscosity insulating oil such as an OF cable, the size of the inlet pipe 310 is relatively small, and conversely, in the case of a cable impregnated with high-viscosity insulating oil such as an MI cable, the inlet pipe 310 The size of can be made relatively large.

4 is a graph showing the amount of movement of high viscosity insulating oil lubricated to the connection box through the inlet pipe 310 when the size of the inner diameter of the inlet pipe 310 is changed. In FIG. 4, the horizontal axis shows the rate of change in the inner diameter of the inlet pipe 310 with respect to the inner diameter of the inlet pipe using the low viscosity insulating oil. The number on the horizontal axis means the drainage of the inner diameter of the inlet pipe using low viscosity insulating oil (for example, the first inner diameter or 10 mm), for example, 3 is the first inner diameter of the inlet pipe using the low viscosity insulating oil. It means the case with 3 times the inner diameter. Meanwhile, the vertical axis shows the amount of movement of the insulating oil that is moved from the insulating oil supply unit 340 to the junction box. For example, 40% means that only 40% of the insulating oil of the insulating oil supply unit is supplied to the junction box.

Referring to FIG. 4, when the inner diameter of the inlet pipe 310 is the same as the first inner diameter corresponding to 1, which is the same as when using the low viscosity insulating oil, only high viscosity insulating oil of less than about 20% of the insulating oil supply unit 340 is used. This is moved to the junction box. In this case, it is difficult to impregnate the reinforcing insulating layer 240 inside the junction box 200 with high-viscosity insulating oil, which leads to a decrease in insulating performance.

As shown in FIG. 4, as the inner diameter of the inlet pipe 310 increases, the amount of high viscosity insulating oil moved from the insulating oil supply unit 340 to the junction box 200 gradually increases, for example, Most of the high-viscosity insulating oil of the insulating oil supply unit 340 when the inner diameter of the inlet pipe 310 is approximately four times the size of the first inner diameter (for example, the inner diameter of 40 mm for the inner diameter of 10 mm) That is, it can be seen that approximately 100% of the high-viscosity insulating oil is transferred to the junction box. In the end, when the second inner diameter of the inlet pipe 310 is increased to 4 times or more than the first inner diameter, for example, 40 mm or more, a lubrication system for lubricating low-viscosity insulating oil can also be used in the connection box of the MI cable. There is this.

5 shows another experimental result for confirming the movement of the high-viscosity insulating oil through the inlet pipe 310. In the graph of FIG. 5, two pressure tanks of the insulating oil supply unit 340 filled with high-viscosity insulating oil are installed, and the internal pressures of the pressure tank are set to 1 bar and 2 bar, respectively, and the inlet pipe 310 according to the present embodiment, That is, compared to the case of using low-viscosity insulating oil, they are connected to each other with inlet pipes grown four times or more, for example, 40 mm or more, and the pressure change inside each pressure tank over time is shown.

Referring to FIG. 5, when the two pressure tanks are connected to each other by the inlet pipe 310 and approximately 3600 seconds, that is, 60 minutes elapse, it can be seen that the pressures in both pressure tanks change similarly to each other. This means that the high-viscosity insulating oil flows through the inlet pipe 310 from a pressure tank having a relatively high pressure of 2 bar to a pressure tank having a relatively low pressure of 1 bar. In particular, it can be seen that the high-viscosity insulating oil sufficiently flows through the inlet pipe 310 so that the internal pressures of both pressure tanks reach a level similar to each other.

Meanwhile, referring to FIG. 3 again, the discharge pipe 330 provided in the opposite direction of the inlet pipe 310 is a vacuum pump 360 capable of maintaining the inside of the metal sheath 20 in a vacuum state having a predetermined degree of vacuum. ) Can be connected. Specifically, the discharge pipe 330 may be provided with a third valve 332 that selectively blocks the discharge pipe 330, and further, the discharge pipe 330 is capable of detecting the vacuum pump 360 and the degree of vacuum. It is connected to the vacuum measuring unit 370. The vacuum pump 360 discharges the air inside the metal sheath 20 through the discharge pipe 330 to form the inside of the metal sheath 20 in a vacuum state having a predetermined degree of vacuum, and the metal sheath Bubbles, etc. remaining in the reinforcing insulating layer 240 in the inner part 20 are removed.

Hereinafter, a process of preventing deterioration of insulation performance by impregnating the reinforcing insulating layer 240 with insulating oil in the case of having the above configuration will be described.

The impregnation process includes a degassing step of removing air bubbles from the reinforcing insulating layer 240 in the metal sheath 20, an oiling step of injecting insulating oil into the metal sheath 20, and a predetermined inside of the metal sheath 20. It may include a pressing step of applying a pressure of.

The defoaming step is a step of discharging and removing air bubbles remaining in the reinforcing insulating layer 240 in the metal sheath 20 to the outside of the metal sheath 20.

Specifically, the first valve 312 and the second valve 314 of the inlet pipe 310 are blocked to open the third valve 332 in a state in which there is no inflow of insulating oil through the inlet pipe 310 do. With the third valve 332 open, the vacuum pump 360 is driven to discharge the air inside the metal sheath 20 to the outside to maintain the inside of the metal sheath 20 in a predetermined vacuum state. . In this case, when the air inside the metal sheath 20 is discharged, it is preferable to properly maintain the vacuum level so that bubbles remaining in the reinforcing insulating layer 240 can be discharged. The degree of vacuum is maintained by controlling the driving of the vacuum pump 360 to maintain a predetermined degree of vacuum through the vacuum measuring unit 370.

Air inside the metal sheath 20 is discharged by the driving of the vacuum pump 360, whereby air bubbles remaining in the reinforced insulating layer 240 are also discharged to the outside through the discharge pipe 330. Subsequently, a fueling step of injecting insulating oil into the metal sheath 20 is started.

The refueling step is performed by opening the first valve 312 while the third valve 332 is open. The first valve 312 is opened and insulating oil is supplied into the metal sheath 20 through the insulating oil supply unit 340. At this time, since the inflow pipe 310 is provided toward the ground as described above, it may be difficult to inflow the insulating oil due to gravity. Accordingly, the pressure tank or the like forming the insulating oil supply unit 340 may have an internal pressure greater than the internal pressure of the junction box 200 in advance. Due to this pressure difference, the insulating oil can easily move from the insulating oil supply unit 340 to the junction box 200.

Further, in the case of the present embodiment, the inlet pipe 310 may be configured such that the inner diameter thereof is changed according to the kinematic viscosity of the insulating oil. For example, in the case of low-viscosity insulating oil, an inlet pipe having a first inner diameter of about 10 mm is used, and in the case of high-viscosity insulating oil, about 4 times, that is, about 40 mm 2 Inlet pipes with inner diameter can be used. Therefore, in the case of using the high-viscosity insulating oil, the insulating oil can more smoothly move from the relatively high-pressure insulating oil supply unit 340 to the low-pressure junction box 200 as in the experiment of FIG. 5. In addition, a predetermined temperature may be applied to facilitate the inflow of the insulating oil. As described above, the flow of the high-viscosity insulating oil is promoted by the inlet pipe having a predetermined pressure, temperature, and a relatively large inner diameter, so that the inflow of the high-viscosity insulating oil can be performed more easily.

The insulating oil flowing into the metal sheath 20 through the inlet pipe 310 is filled from the lower portion of the metal sheath 20 and is impregnated with the insulating paper constituting the reinforcing insulating layer 240. In this case, the outer semiconducting layer 16 provided outside the reinforcing insulating layer 240 is formed by winding carbon paper, etc., so that the insulating oil impregnates the reinforcing insulating layer 240 through the outer semiconducting layer 16. do.

Meanwhile, while the insulating oil is injected into the interior of the metal sheath 20, the vacuum pump 360 connected to the inlet pipe 310 is still running, so that the insulating oil flowing into the metal sheath 20 is bubbled. Even in the case of including, the air bubbles are discharged to the outside through the discharge pipe 330. After filling the inside of the metal sheath 20 with insulating oil, the first valve 312 and the third valve 332 are closed. Here, when the insulating oil is discharged to the outside through the discharge pipe 330, it may be determined that the inside of the metal sheath 20 is filled with the insulating oil. In this case, the inner diameter of the discharge pipe 330 may be determined to be changed according to the kinematic viscosity of the insulating oil in the same manner as the inner diameter of the inlet pipe 310.

Subsequently, a pressing step of applying a predetermined pressure into the metal sheath 20 is performed. The pressing step 500C is performed in a state in which the first valve 312 and the third valve 332 are closed and the second valve 314 is opened. That is, it is performed in a state in which the inside of the metal sheath 20 is in communication with the pressing part 350. The pressing part 350 applies a predetermined pressure to the inside of the metal sheath 20 through the inlet pipe 310. In this way, when the inside of the metal sheath 20 is pressed through the pressing part 350, the insulating oil filled in the metal sheath 20 can uniformly impregnate the reinforcing insulating layer 240, and further After the air bubbles are removed, the remaining voids can be filled with insulating oil to prevent deterioration of the insulation performance. In addition, a predetermined temperature may be applied to facilitate re-impregnation by the insulating oil. When the temperature is applied in this way, the flow of the insulating oil is promoted, so that re-impregnation of the reinforcing insulating layer by the insulating oil can be performed more easily.

On the other hand, the above-described intermediate connection method can of course be applied not only to connection between cables, but also to a terminal connection box connecting cables and overhead lines.

10..conductor
12..Internal semiconducting layer
14..insulation layer
16..External semiconducting layer
20..Metal sheath
100...cable
200... access box
300...gas system
310..Inflow pipe
312..first valve
314..second valve
330..discharge pipe
332..3rd valve
340..Insulating oil supply
350..Pressure part
360..vacuum pump
370..Vacuum measuring unit

Claims (4)

In an oil supply system for lubricating a junction box to which an insulating oil-impregnated cable is connected with the insulating oil,
An inlet pipe connected to the metal sheath forming the junction box to provide a passage through which the insulating oil moves;
An insulating oil supply unit connected to the inlet pipe and receiving the insulating oil supplied to the inlet pipe;
A pressurizing part applying a predetermined pressure to the inside of the junction box through the inlet pipe;
A discharge pipe provided in a direction opposite to the inlet pipe along the metal sheath through which the insulating oil is discharged;
A vacuum pump connected to the discharge pipe to maintain the interior of the junction box in a vacuum state; And
A junction box lubricating system for a cable impregnated with high viscosity insulating oil having a; a vacuum measuring unit connected to the discharge pipe to detect a vacuum level of the junction box. In an oil supply system for lubricating a junction box to which an insulating oil-impregnated cable is connected with the insulating oil,
An inlet pipe connected to the metal sheath forming the junction box to provide a passage through which the insulating oil moves;
An insulating oil supply unit connected to the inlet pipe and receiving the insulating oil supplied to the inlet pipe; And
And a pressurizing part for applying a predetermined pressure to the inside of the junction box through the inlet pipe,
The inner diameter of the inlet pipe is determined as the first inner diameter when the kinematic viscosity of the insulating oil is 40 to 4 to 5 cSt and represents a value of 1 to 2 cSt in 100 so that the inner diameter of the inlet pipe is proportional to the kinematic viscosity of the insulating oil. , It is determined as a second inner diameter when the kinematic viscosity of the insulating oil is 40 to 4000 to 6000 cSt and represents a value of 100 to 180 to 220 cSt, and the second inner diameter is 4 times or more than the first inner diameter. Junction box lubrication system for cables impregnated with insulating oil. In an oil supply system for lubricating a junction box to which an insulating oil-impregnated cable is connected with the insulating oil,
An inlet pipe connected to the metal sheath forming the junction box to provide a passage through which the insulating oil moves;
An insulating oil supply unit connected to the inlet pipe and receiving the insulating oil supplied to the inlet pipe; And
And a pressurizing part for applying a predetermined pressure to the inside of the junction box through the inlet pipe,
The inlet pipe has an inner diameter of 10 mm when the kinematic viscosity of the insulating oil is 40 to 4 to 5 cSt, and 1 to 2 cSt in 100 so that the inner diameter is proportional to the kinematic viscosity of the insulating oil, and the insulating oil Insulated oil-impregnated cable junction box lubrication system, characterized in that when the kinematic viscosity of 40 to 4000 to 6000 cSt, and 100 to 180 to 220 cSt value represents the inner diameter of 40mm. delete

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