KR20160063219A - Joint for High-Voltage Direct Current - Google Patents

Abstract

The present invention relates to an intermediate junction box for an ultra-high-voltage direct current power cable. According to the present invention, the intermediate junction box for an ultra-high-voltage direct current power cable connects one pair of ultra-high-voltage direct current cables, which successively comprise a conductor, an inner semi-conductive layer, an insulating layer and an outer semi-conductive layer in order from the center thereof to the outside thereof, to each other. The intermediate junction box comprises: a connection sleeve encompassing end portions of the conductors of the one pair of cables and electrically connected to the conductors; a first electrode electrically connected to the conductors of the one pair of cables; one pair of second electrodes spaced apart from each other at a predetermined distance so as to be provided to face each other, and connected to the outer semi-conductive layers of the one pair of cables; a junction box insulating layer provided to encompass the first electrode and the second electrodes; and a joint sleeve including a junction box shielding layer provided on the outer side of the junction box insulating layer, wherein the junction box insulating layer comprises liquid silicon rubber provided with a glycol-based additive, which includes ethylene glycol and/or propylene glycol, and provided with at least one of nano-sized inorganic particles including at least one of silica, silicon carbide, aluminum silicate, calcium silicate, magnesium oxide, zinc oxide, calcium carbonate and carbon black, and a volume resistivity of the junction box insulating layer has a range of 1012 Ω·cm to 1018 Ω·cm between the normal temperature and an operating temperature of the intermediate junction box.

Description

{Joint for High-Voltage Direct Current}

The present invention relates to an intermediate connection case for an ultra-high voltage direct current power cable, and more particularly, to an intermediate connection case for an ultra-high voltage direct current power cable. More particularly, the present invention relates to an intermediate connection case for an ultra- The present invention relates to an intermediate connection box for a super high voltage direct current power cable which is excellent in formability.

Generally, a power cable is a device that transmits electric power using an internal conductor, and can be classified into a DC (direct current) power cable and an AC (alternating current) power cable.

At this time, an intermediate connection box (Join) for connecting the ends of the power cable to each other or an end connection box for connecting the power cable and the processing cable can be used.

In the case of the intermediate connection case of the DC power cable, an insulating layer formed by EDPM has been conventionally used. However, when the insulating layer of the intermediate connection box is formed by the EPDM, the long-term reliability such as the tear strength and the permanent rate of change is inferior, and furthermore, the formability is poor when molding is performed for forming the insulating layer.

Prior Art Document 1 (JP2012-157124) discloses an insulating layer using a liquid insulating silicone rubber in a tubular protective covering to which a power cable is connected, and the liquid insulating silicone rubber is LSR2030J containing siloxane, silica and platinum compound Fig. On the other hand, the prior art document 2 (US8476526) discloses a junction box having an insulating layer composed of a silicone rubber containing a predetermined additive.

However, the prior art documents 1 and 2 do not disclose various physical properties of the insulating layer made of the insulating silicone rubber or silicone rubber, and in particular, the requirements of the insulating layer necessary for connecting the power cables for HVDC to each other . Further, the prior art document 2 discloses that EPDM and silicone rubber can be used as the material of the insulating layer, and thus it is understood that the problem of the present invention is not recognized at all.

On the other hand, the prior art document 3 (US8097807) discloses a connection box made of EPDM or silicone rubber in a connection box for connecting a high-voltage cable. In addition, the prior art document 4 (US2012-345314) discloses an insulating layer composed of a conductive polymer material including a conductive carbon filler in a connection box to which a high voltage cable is connected.

However, the prior art document 3 only discloses that the material of the insulating layer in the junction box connecting the high-voltage power cable is composed of EPDM or silicone rubber, and there is no disclosure of the components contained in the silicone rubber. In particular, the prior art 3 discloses that EPDM and silicone rubber can be used as the material of the insulating layer, so that it can be understood that the problem of the present invention is not recognized at all. Furthermore, the prior art 3 and the prior art 4 have no disclosure on various physical properties of the insulating layer, and in particular, there is no consideration of the requirements of the insulating layer necessary for connecting the power cables for HVDC to each other.

1. Prior Art 1: JP2012-157124 2. Prior Art 2: US8476526 3. Prior Art 3: US8097807 4. Prior Art 4: US2012-345314

The present invention provides an intermediate connection box for a DC power cable having an insulation layer formed of silicone rubber to improve long-term reliability such as tear strength and permanent change rate, .

It is an object of the present invention to provide an intermediate connection case for connecting a pair of cables sequentially including a conductor, an inner semiconductive layer, an insulation layer and an outer semiconductive layer from the center to the outer side, A first electrode electrically connected to the conductors of the pair of cables, and a pair of second electrodes electrically connected to the outer semiconductive layer of the pair of cables, the first electrodes being spaced apart from each other by a predetermined distance, And a joint sleeve including a second electrode, a connection port insulation layer surrounding the first electrode and the second electrode, and a connection port shielding layer provided outside the connection port insulation layer, The insulating layer may be selected from the group consisting of ethylene glycol, glycol based additives including at least one of propylene glycol and nano-sized silica, silicon carbide, Wherein at least one of the inorganic particles comprises at least one of aluminum, aluminum oxide, calcium silicate, magnesium oxide, zinc oxide, calcium carbonate, and carbon black, And the volume resistivity value of the layer has a range of 10 ¹² ? 占 내지 m to 10 ¹⁸ ? 占 ㎝ m.

Here, the Fourier transform coefficient (FEF) of the junction box insulation layer may be 5.0 or less, and the discharge efficiency of the junction box insulation layer may be determined so that the charge density after 5 minutes of discharge is 20 C / m 3 or less. The dielectric strength of the connection box insulating layer may be 60 kv / mm or more.

According to the intermediate connection box of the present invention having the above-described configuration, connection can be performed within a short time by a simple process even in the field connection.

Further, according to the present invention, the insulating layer inside the intermediate junction box can be formed of silicone rubber to improve long-term reliability such as tear strength and permanent change rate, and further improve moldability.

According to the present invention, it is also possible to use at least one of glycol-based additives including at least one of ethylene glycol and propylene glycol or nano-sized silica, silicon carbide, aluminum silicate, calcium silicate, magnesium oxide, zinc oxide, calcium carbonate, It is possible to prevent sudden increase in the electric field in the connection box while suppressing rapid heat generation inside the intermediate connection box by adjusting the value of the volume resistivity.

1 is a perspective view showing an internal configuration of a power cable for DC having an insulation layer composed of XLPE,
2 is a sectional view showing the structure of a connection box according to an embodiment of the present invention,
Figure 3 is a graph showing the temperature change with variation in volume resistivity in an intermediate junction box,
4 is a graph showing an electric field change in accordance with a change in volume resistivity in an intermediate junction box,
Figure 5 is a graph showing the change in FEF inside the intermediate junction,
FIG. 6 is a graph showing a change in charge density according to remaining space charge according to the prescription of additives,
7 is a graph showing a change in dielectric strength depending on whether or not an additive is prescribed.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals designate like elements throughout the specification.

In the present specification, first, a structure of a high-voltage direct current (HVDC) power cable (hereinafter referred to as a 'power cable') according to various embodiments will be described, and then an intermediate connection box for connecting the power cables Let's take a look.

1 is a perspective view showing the internal structure of a power cable 200 having an insulating layer composed of XLPE.

Referring to FIG. 1, the power cable 200 includes a conductor 210 along a center portion thereof. The conductor 210 serves as a passage through which the current flows. The conductor 210 may include a circular central strand 210A and a rectangular strand 210C composed of a square strand 210B twisted to surround the central strand 210A as shown in the figure. The square wire strand 210C is formed by forming a plurality of square wire strands 210B in a rectangular shape through a continuous extrusion process and twisting the plurality of square wire strands 210B on the center strand 210A. The conductor 210 is formed to have a circular shape as a whole. The conductor 210 may be formed by twisting a plurality of circular wire strands. However, the conductor made of the square wire element has a relatively higher spot rate than the conductor made of the circular element wire, so that it can be suitable for an ultra high-voltage DC power cable.

However, the surface of the conductor 210 is not smooth, the electric field may be uneven, and corona discharge tends to occur partially. In addition, if a gap is formed between the surface of the conductor 210 and the insulating layer 214 described later, the insulating performance may be deteriorated. In order to solve the above-described problems, the outer surface of the conductor 210 is covered with a semiconductive material such as semiconductive carbon paper, and a layer formed by semiconductive material is defined as an inner semiconductive layer 212.

The inner semiconductive layer 212 improves the dielectric strength of the insulating layer 214, which will be described later, by making the electric charge distribution on the conductive surface uniform to make the electric field uniform. Further, the gap between the conductor 210 and the insulating layer 214 is prevented to prevent corona discharge and ionization. The inner semiconductive layer 212 also prevents penetration of the insulating layer 214 into the conductor 210 when the power cable 200 is manufactured.

An insulating layer 214 is provided on the outer side of the inner semiconductive layer 212. The insulating layer 214 electrically insulates the conductor 210 from the outside. In general, the insulating layer 214 must have a high breakdown voltage and the insulation performance must be stable for a long period of time. Furthermore, it should have low dielectric loss and resistance to heat such as heat resistance. Therefore, polyolefin resin such as polyethylene and polypropylene is used as the insulating layer 214, and a polyethylene resin is preferable. The polyethylene resin may be a crosslinked resin, and may be produced by a silane or an organic peroxide such as, for example, dicumylperoxide (DCP) as a crosslinking agent.

However, when the direct current high voltage is applied to the power cable, the insulation layer 214 injects charges from the conductor 210 into the inner semiconductive layer 212, the insulation layer 214, and the like, A space charge can be formed. When the impulse voltage is applied to the cable or the polarity of the DC voltage applied to the cable is abruptly reversed, the space charge is accumulated in the insulating layer 214 according to the use time of the cable, And the electric field strength is rapidly increased to lower the dielectric breakdown voltage of the power cable.

The insulating layer 214 may include inorganic particles in addition to the crosslinked resin. The inorganic particles may be nano-sized aluminum silicate, calcium silicate, calcium carbonate, magnesium oxide, or the like. However, from the viewpoint of the impulse strength of the insulating layer, magnesium oxide is preferable as the inorganic particles. The magnesium oxide can be obtained from magnesium natural ore, but can also be prepared from artificial synthetic materials using magnesium salt in seawater, and it is also possible to supply the material with high purity and stable quality and physical properties.

Although the magnesium oxide has a crystal structure of a face-centered cubic structure, it may have various shapes, purity, crystallinity, physical properties and the like depending on the synthesis method. Specifically, the magnesium oxide is divided into a cubic shape, a terrace shape, a rod shape, a porous shape, and a spherical shape. The magnesium oxide may be variously used depending on its specific physical properties. Such inorganic particles including magnesium oxide exhibit an effect of suppressing the movement of charges and the accumulation of space charges by forming a potential well at the boundary between the base resin and the inorganic particles when an electric field is applied to the cable.

However, the inorganic particles added to the insulating layer 214 act as impurities when added in a large amount and have a problem of lowering the impulse strength, which is another important characteristic required in a power cable even when used in small amounts, Since the accumulated space charge can not be sufficiently reduced by the inorganic particles alone, it is preferable to add 0.2 to 5 parts by weight.

On the other hand, if not only the inside but also the outside of the insulating layer 214 is not shielded, a part of the electric field is absorbed by the insulating layer 214, but most of the electric field is discharged to the outside. In this case, if the electric field becomes larger than a predetermined value, the insulating layer 214 and the outer shell of the power cable 200 may be damaged by an electric field. Therefore, a semiconductive layer is further provided on the outer side of the insulating layer 214 and is defined as an outer semiconductive layer 216 to distinguish it from the inner semiconductive layer 212 described above. As a result, the outer semiconductive layer 216 is grounded to make the distribution of the lines of electric force between the inner semiconductive layer 212 and the inner semiconductive layer 212 equal to each other, thereby improving the dielectric strength of the insulating layer 214. In addition, the outer semiconductive layer 216 can smooth the surface of the insulating layer 214 in the cable, thereby alleviating the electric field concentration and preventing the corona discharge.

A shielding layer 218 made of a metal sheath and / or a neutral wire is provided outside the outer semiconductive layer 216 according to the type of the power cable. The shielding layer 218 is provided for electrical shielding and return of short-circuit current.

A jacket 220 is provided on the outer periphery of the power cable 200. The enclosure 220 is provided at an outer portion of the power cable 200 to protect the internal structure of the power cable 200. Accordingly, the outer cover 220 has excellent chemical resistance and mechanical strength to withstand chemicals such as weatherability, chemical substances, and the like, which can withstand various environments such as light, weather, moisture, air and various climatic conditions. Generally, it is made of PVC (Polyvinyl Chloride) or PE (Polyethylene).

Hereinafter, an intermediate connection box for connecting the power cables as described above will be described with reference to the drawings.

2 is a cross-sectional view illustrating the structure of an intermediate connection box 300 according to an embodiment of the present invention.

Referring to FIG. 2, the intermediate connection box 300 includes a conductor connection part 312 surrounding the ends of the conductors 210 of the pair of power cables and connecting the conductors 210, And a joint sleeve 360 made of an elastic material capable of shrinking at room temperature to surround the outer side of the cable. Furthermore, the intermediate connection case 300 may further include a housing (not shown) formed of a 'metal casing' that surrounds the joint sleeve 360. At this time, a space between the housing and the joint sleeve 360 may be filled with a waterproof material (not shown).

The conductor connection part 312 has a connection sleeve connected to the insulation layer 214 of the pair of power cables and a compression sleeve (not shown) for pressing and connecting the conductor 210 inside the connection sleeve, As shown in FIG.

The conductor connection portion 312 is configured to surround the ends of the conductors 210 extending from the end portions of the pair of power cables and electrically connected to the conductors 210 through braided wires or the like do. The conductor 210 may be connected to the inside of the conductor connection part 312 by welding or the like, or may be firmly connected by the compression sleeve described above.

The joint sleeve 360 includes a first electrode 310 electrically connected to the conductor 210 of the pair of power cables and a second electrode 310 disposed to face the first electrode 310 in the intermediate connection box 300 And a connection insulating layer 340 covering the first electrode 310 and the second electrode 320. The insulating layer 340 may be formed of a conductive material. The connection port insulating layer 340 may further include a connection port shielding layer 350 disposed outside the connection port insulating layer 340.

The joint sleeve 360 is connected to the insulating layer 214 of the pair of power cables and the outer semiconductive layer as an elastic material. The joint sleeve 360 has a hollow shape and has a shrinkage at room temperature.

Meanwhile, the first electrode 310 and the second electrode 320 serve to spread the electric field uniformly without being concentrated locally.

Specifically, the first electrode 310 is made of a semi-conductive material and is provided outside the conductor connection part 312 and is electrically connected to the conductor 210 of the power cable to function as a so-called high voltage electrode. do. The second electrode 320 is also made of a semi-conductive material and connected to the outer semiconductive layer 216 of the power cable to serve as a so-called shielding electrode. Therefore, the electric field distribution in the intermediate connection box 300 is distributed between the first electrode 310 and the second electrode 320. In this case, the shapes, sizes, and materials of the first electrode 310 and the second electrode 320 are appropriately adjusted so that the electric field distribution between the first electrode 310 and the second electrode 320 is not concentrated can do.

Meanwhile, the connection port insulating layer 340 provided at the outer side of the intermediate connection port 300 is provided at the outer side of the intermediate connection port 300 to ensure the insulation performance of the intermediate connection port 300.

The connection-layer insulating layer of the intermediate junction box 300 is conventionally made of EPDM (Ethylene Propylene Diene Monomer). EPDM is widely used as an insulating layer of an intermediate junction box because of its excellent weatherability and electrical insulation. However, the EPDM has poor long-term reliability such as tear strength and permanent change rate, and is somewhat difficult to form. Accordingly, a material to replace the EPDM is required. In this embodiment, an insulating layer is formed of silicone rubber (SR) instead of EPDM when forming the connection port insulating layer 340.

Unlike EPDM, the silicone rubber has excellent long-term reliability such as tear strength and permanent change rate, and has an advantage of improving productivity by a quick production process. In addition, the silicone rubber has various advantages in that it can be molded into various design products to improve moldability, does not require secondary vulcanization, and can be molded by double injection molding.

On the other hand, in the case of forming the intermediate connection box 300 connecting the power cables with the silicone rubber, it is necessary to appropriately adjust the volume resistivity in order to prevent heat generation and electric field concentration in the connection box, It is necessary to maintain DC insulation properties such as DC insulation strength.

To this end, in the present embodiment, when the connection port insulating layer 340 is formed of silicone rubber, an additive is added to the silicone rubber. Wherein the additive comprises at least one of a glycol-based additive comprising at least one of ethylene glycol, propylene glycol, and nano-sized silica, silicon carbide, aluminum silicate, calcium silicate, magnesium oxide, zinc oxide, calcium carbonate, And at least one of inorganic particles.

The volume resistivity can be adjusted in an appropriate range so as to suppress the heat generation of the connection box and to prevent the electric field concentration by forming the connection-connection insulation layer 340 by the silicone rubber to which the additive is added. Further, : Field Enhancement Factor) to reduce space charge residuals and further improve DC isolation.

For example, when the joint sleeve 360 is molded, a mold is inserted into a molding mold, and a semiconductive material is injected into the mold to mold the first electrode 310 and the second electrode 320. Subsequently, a liquid silicone rubber (LSR) and the above-mentioned additives are put into the molding die to cure the liquid silicone rubber to form a connection container insulating layer 340 formed of silicone rubber.

The present inventors have conducted various experiments to confirm the performance of the connection-connection insulating layer 340 formed by the silicone rubber to which the additive is added, and will be described with reference to the drawings.

3 is a graph showing a change in temperature due to a change in the volume resistivity of the insulating layer 340 connected to the inside of the intermediate junction box 300. In FIG. 3, the abscissa indicates the volume resistivity value (? Cm), and the ordinate indicates the temperature (占 폚). Generally, according to the Ohm's law, the current I and the resistance value R are inversely proportional to each other when the voltage V is constant.

However, in the case of the power W related to the heat generation, it is proportional to the square of the current I and the resistance value R as shown in the following equation (2).

Therefore, when the volume resistivity becomes small, the current value rises inversely, and the power becomes proportional to the square of the current value and the resistance value. Therefore, from a predetermined point of time when the current value rises, The power value is increased. The rise of the power value causes the temperature to rise. As a result, it is important to know the range of volume resistivity that does not cause a temperature rise.

Referring to FIG. 3, when the volume resistivity falls below about 10 ¹¹ Ω · cm when the electric field lift coefficient (FEF) is approximately 1.0, when the temperature is lower than the operating temperature (approximately 70 to 80 (FEF) is about 2.0, and when the volume resistivity falls below about 10 < ¹² > OMEGA .cm, the temperature is higher than the operating temperature of the intermediate junction box 300 . Therefore, in this embodiment, the minimum value of the volume resistivity of the silicone rubber to which the additive is added can be set to approximately 10 ¹² Ω · cm.

Meanwhile, FIG. 4 is a graph showing an electric field change in accordance with a change in the volume resistivity of the insulating layer 340 connected in the intermediate junction box 300. In FIG. 4, the abscissa indicates the volume resistivity value (? 占 ㎝ m), and the ordinate indicates the electric field (kv / mm). In FIG. 4, the temperature conditions were experimented at ambient temperature between the operating temperatures of the intermediate junctions 300, i.e., between about 15 and 20 degrees Celsius and in the temperature range of about 70 to 80 degrees Celsius.

4, 'HV' represents an electric field applied to the first electrode 310 corresponding to a high voltage electrode, and 'Shield' represents an electric field applied to the second electrode 320 serving as a shielding electrode .

Referring to FIG. 4, as the value of the volume resistivity of the connection port insulating layer 340 changes, the electric field applied to the first electrode 310 is kept relatively constant while the voltage applied to the second electrode 320 It can be seen that the electric field value rises sharply when the volume resistivity rises to about 10 ¹⁸ ? Cm or more. Therefore, in this embodiment, the maximum value of the volume resistivity of the silicone rubber to which the additive is added can be set to approximately 10 ¹⁸ Ω · cm.

As a result, in order to prevent a sudden heat generation inside the intermediate connection box 300 and further to prevent the electric field from concentrating inside the intermediate connection box 300, the silicone rubber (or the connection insulation layer) The range of the volume resistivity value may be set in the range of 10 ¹² Ω · cm to 10 ¹⁸ Ω · cm. In addition, the above-mentioned additives may be added so that the range of the volume resistivity of the silicone rubber (or the connecting-insulating layer) satisfies the range of 10 ¹² Ω · cm to 10 ¹⁸ Ω · cm. In this case, it can be said that the range of the volume resistivity value is satisfied in a temperature range having a range between the temperature range described above, that is, the operating temperature of the intermediate junction box 300 at room temperature.

On the other hand, in the case of an intermediate connection box connecting the HVDC power cables to each other, space charges can be accumulated inside the connection box, which acts as a weak point that deteriorates the insulation performance of the connection box. Therefore, it is necessary to prevent accumulation of the space charge.

FIG. 5 is a graph showing changes in the electric field lift coefficient (FEF) according to the prescription of the additive in the intermediate junction box. FIG. In FIG. 5, the horizontal axis indicates time (min), and the vertical axis indicates electric field corresponding to accumulation of space charge.

On the other hand, the electric field lift coefficient FEF can be calculated by the following equation.

In Equation (3), E _applied denotes an electric field supplied to the connection-coupling insulating layer 340, and E _max denotes an electric field in which electric fields corresponding to the accumulation of the supplied electric field and space electric charge are all summed.

Referring to Fig. 5, Group A shows a silicone rubber without additives, and Group B shows a silicone rubber with additives according to the present embodiment.

As shown in FIG. 5, in the group A of the silicone rubber in which the additive is not prescribed, electric field by space charge due to the accumulation of space charge is remarkably increased along with the supplied electric field (Applied Electric Field) The coefficient FEF shows a value of approximately 5.0 or more.

On the other hand, the B group of the silicone rubber in which the additive is formulated has a relatively low electric field by space charge due to the accumulation of space charge relative to the applied electric field (FEF) 0.0 > 5.0 < / RTI > The additive may be added to the junction box insulating layer according to the present embodiment so that the electric field lift factor (FEF) shows a value of approximately 5.0 or less.

On the other hand, it is important not only to prevent the above-mentioned space charge from accumulating inside the intermediate connection box, but also to disappear within a short time after the discharge without remaining in the intermediate connection box.

6 is a graph showing the remaining amount of space charge depending on whether or not the additive is prescribed inside the intermediate connection box after discharge. 6 to 6 (A) show the silicone rubber in which the additives are not prescribed, and Fig. 6 (B) shows the silicone rubber in which the additives are prescribed according to the present embodiment. The abscissa represents the time (min), and the ordinate represents the charge density (C / cm < 3 >) according to the accumulation of the space charge.

Specifically, FIG. 6 (A) is a graph showing the relationship between the amount of space charge accumulated after 1 minute, 2 minutes, 3 minutes, 4 minutes, and 5 minutes after discharging (0 minutes) ≪ / RTI > As shown in Fig. 6 (A), in the case of the silicone rubber in which the additive is not prescribed, it shows a high level of charge density of about 120 C / cm 3 immediately after the discharge (0 minute). In addition, although the charge density decreases with passage of time from 1 minute to 5 minutes after discharge, the charge density tends to decrease gradually, and the charge density is about 30 C / cm 3 even after 5 minutes after discharge .

On the other hand, as shown in Fig. 6 (B), in the case of the silicone rubber in which the additives are formulated according to the present embodiment, the charge density is very low, about 10 C / cm 3 immediately after the discharge . Also, it can be seen that as the time elapses after the discharge, the charge density sharply decreases.

On the other hand, in the case of an intermediate connection box for HVDC, a higher level of dielectric strength is required compared with AC (Alternavie current).

7 is a graph showing a change in dielectric strength depending on whether or not an additive is prescribed. In Fig. 7, the vertical axis shows Dielectric Strength (kv / mm).

Referring to Fig. 7, Group A shows a silicone rubber in which additives are not prescribed, and Group B (Group B) shows a silicone rubber in which additives are prescribed according to the present embodiment.

As shown in Fig. 7, the A group of the silicone rubber in which the additives are not prescribed exhibits an insulation strength value of about 35 kv / mm to 45 kv / mm at an AC strength (AC strength) (DC strength) of about 50 kv / mm to 60 kv / mm. On the other hand, group B of the silicone rubber prescribed additives exhibits an electric strength value similar to that of the case where the additive is not prescribed in the AC strength. On the other hand, the DC strength exhibits a dielectric strength value of approximately 85 kv / mm to 100 kv / mm, which is relatively high compared to the case where an AC voltage is applied.

Therefore, the additive can be added to the junction box insulating layer according to the present embodiment so that the DC dielectric strength has a value of about 60 kv / mm or more.

While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. . It is therefore to be understood that the modified embodiments are included in the technical scope of the present invention if they basically include elements of the claims of the present invention.

210 ... conductor
212 ... inner semiconductive layer
214 ... insulating layer
216 ... outer semiconductive layer
300 ... medium connection
310 ... first electrode
312 ... connection sleeve
320 ... second electrode
340 ... connection box insulation layer
350 ... connection box shielding layer

Claims (4)

An intermediate connection box for an ultra-high voltage direct current power cable connecting a pair of super high voltage direct current power cables having a conductor, an inner semiconductive layer, an insulation layer and an outer semiconductive layer sequentially from the center to the outer side,
A conductor connecting portion for electrically connecting the conductors of the pair of cables to each other; And
A first electrode electrically connected to the conductor of the pair of cables, a pair of second electrodes facing each other at a predetermined distance from each other and connected to the outer semiconductive layer of the pair of cables, And a joint sleeve including a connection port insulating layer provided to surround the electrode and the second electrode and a connection port shielding layer provided outside the connection port insulating layer,
Wherein the junction box insulating layer is formed of at least one of glycol based additives including at least one of ethylene glycol and propylene glycol and at least one of nano-sized silica, silicon carbide, aluminum silicate, calcium silicate, magnesium oxide, zinc oxide, calcium carbonate, Wherein at least one of the inorganic particles is formed from a silicone rubber prescribed,
And the volume resistivity of the connection-insulating layer is in the range of 10 ¹² Ω · cm to 10 ¹⁸ Ω · cm between the operating temperature of the intermediate connection box at room temperature. . The method according to claim 1,
And an electric field lift coefficient (FEF) of the junction box insulating layer is 5.0 or less. The method according to claim 1,
Wherein the discharge efficiency of the connection box insulating layer is a charge density of 20 C / m < 3 > or less after 5 minutes of discharge. The method according to claim 1,
And the dielectric strength of the connection box insulating layer is 60 kv / mm or more.

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