WO2018190497A1

WO2018190497A1 - Joint box for ultra-high voltage direct current power cable, and ultra-high voltage direct current power cable system comprising same

Info

Publication number: WO2018190497A1
Application number: PCT/KR2018/000943
Authority: WO
Inventors: 윤호중; 김성윤; 정의환; 홍성표
Original assignee: 엘에스전선 주식회사
Priority date: 2017-04-11
Filing date: 2018-01-22
Publication date: 2018-10-18
Also published as: WO2018190497A8

Abstract

The present invention relates to a joint box for an ultra-high voltage direct current power cable, and an ultra-high voltage direct current power cable system comprising the same. Specifically, the present invention relates to a joint box for an ultra-high voltage direct current power cable which can effectively prevent dielectric breakdown of the joint box of the cable due to local field concentration by alleviating an electric field at a portion on which the electric field structurally concentrates, and an ultra-high voltage direct current power cable system comprising the same.

Description

【Specification】

[Name of invention]

Extra junction box for ultra high voltage DC power cable and ultra high voltage DC power cable system including the same

Technical Field

The present invention relates to an intermediate junction box for an ultra high voltage direct current power cable and an ultra high voltage direct current power cable system including the same. Specifically, the present invention is to effectively mitigate the electric field of the portion where the electric field is structurally concentrated, the intermediate junction box of the cable by the local field accumulation effectively prevents, the intermediate junction box for ultra-high voltage DC power cable and the same An ultra high voltage DC power cable system.

Background Art

The ultra high voltage cable is a device that transmits power by using an internal conductor, and can be divided into a high voltage direct current (DC) power cable and an alternating current (AC) power cable.

Since the DC transmission method using the ultra high voltage DC power cable has a low power loss and has an advantage of long distance transmission, a long voltage transmission line is formed by forming an ultra high voltage DC power cable system connecting the power cables to each other using an intermediate junction box. do.

On the other hand, in general, a power cable is a conductor, inner semiconductive layer surrounding the conductor, an insulating layer surrounding the inner semiconductive layer made of a material such as cross-linked polyethylene (XLPE), the insulating layer is _i surround the outer semiconductive layer, wherein Metal car surrounding the outer semiconducting layer It is possible to have a structure in which a closed layer and an outer shell for protecting the internal structure of the power cable from the layer stratification, pressure, and the like of the closed layer are sequentially stacked.

The power cable may be connected to each other at its ends through an incremental connection box having a cross-sectional structure shown in FIG.

As shown in FIG. 1, the conventional ultra high voltage cable system uses an incremental junction box 300 ′ to form a conductor (not shown), an inner semiconducting layer (not shown), an insulating layer 214, and an outer semiconducting layer 216. And a pair of power cables provided so that the ends of the conductor, the inner semiconducting layer, the insulating layer, and the outer semiconducting layer are sequentially exposed to each other.

However, the power cable system for direct current transmission has a resistive electric field distribution characteristic in which the electric field distribution in the interior depends on the volume resistivity. Specifically, the conventional intermediate ¾ speed for the power cable or the DC power cable is the interface between the joint sleeve 320 ′ and the power cable, in which structures made of materials having different volume resistivity meet each other, and the second electrode ( 322 '). The portion where the insulating layer 214 of the power cable and the junction box insulating layer 323 ′ meet and is divided by a broken line in FIG. 1, or the first electrode 32 Γ, the insulating layer 214 of the power cable, and the connection The area where the different materials are in contact with each other, such as part B, which is divided by a broken line in FIG. 2 as the insulating layer 323 ′ meets each other, changes in volume resistivity of each material according to temperature changes, voids in junction box manufacturing, foreign matter intrusion, etc. There is a problem, which acts as an insulation weakness. In particular, the electric field is concentrated structurally, and the junction breakdown may occur.

therefore. Structural electric field structurally in the middle connection for high voltage DC power cable By mitigating the electric field of the concentrated part, it is possible to effectively prevent the breakdown of insulation by local electric field concentration and to alleviate the heat generation phenomenon at the connection part. Ultra high voltage DC power cable system is urgently needed.

[Detailed Description of the Invention]

[Technical problem]

The present invention provides an intermediate junction box for a cable and a cable system including the same, which can effectively prevent the junction breakdown caused by local electric field concentration by mitigating the electric field of a part where the electric field is structurally concentrated by the intermediate junction box for the cable. It aims to do it.

Technical Solution

In order to solve the above problems, the present invention connects a pair of ultra-high voltage DC power cable including a conductor, an inner semiconductive layer surrounding the conductor, an insulating layer surrounding the inner semiconductive layer, and an outer semiconductive layer surrounding the insulating layer. An intermittent junction box for an ultra-high voltage direct current power cable, comprising: a first electrode having rounded left and right ends in a longitudinal direction of the intermediate junction box; A pair of agents formed to face each other at a predetermined distance from the first electrode to the left and the right in the longitudinal direction of the auxiliary junction box;

2 electrodes; And a hollow sleeve formed to surround the first electrode and the second electrode, made of an elastic material that can be contracted at room temperature, and having a through hole therein in the longitudinal direction, so that current does not leak out of the intermediate junction box. And a joint sleeve including a junction box insulation portion, the junction box insulation portion comprising: a first insulation layer and a first insulation layer; And a second insulating layer having a lower volume resistivity than the first insulating layer, wherein the second insulating layer has an innermost surface of the joint sleeve, an interface between the first electrode and the ¾-containing insulating portion, and An additional junction box for an ultra-high voltage direct current power cable may be provided to surround at least a portion of the interface between the second electrode and the junction box insulation unit.

In addition, the thickness of the first insulating layer satisfies Equation 1 below.

[Equation 1]

1.85ί / ₀

BD ^ ^" ᅳ <BDV 層 In Equation 1, Uo is the rated voltage of the intermediate junction box for the ultra-high voltage DC power cable, 1.85U ₀ is the brain impulse test voltage (BIL; Bas ic impul s insulat ion level ) May be a thickness of the first insulating layer on the first electrode, and may be a breakdown voltage of the first insulation layer 340.

In this case, the second insulating layer may be formed to cover both the first electrode and the crab electrode so that the first electrode and the second electrode do not contact the first insulation layer.

In addition, the low] 2 electrode may gradually increase as the vertical distance from the innermost surface of the joint sleeve toward the first electrode. Here, the junction box shielding layer provided on the outside of the joint sleeve, shielding the electric field leaked to the outside of the intermediate junction box; And a third thickening point in which the first insulating layer, the second insulating layer, and the junction box shielding layer are in contact with each other, and a distance between the first electrode and the three thickening points is a distance between the first electrode and the second electrode. Can be greater than In addition, the first insulating layer and the low 12 insulating layer have a volume resistivity of IX 10 "to IX.

18

10 Ω αη, and the volume resistivity of the second insulation layer may be 10 times lower than the volume resistivity of the first insulation layer. Also. The second insulating layer may be formed of a second insulating composition including a base resin and an additive for adjusting resistivity. In this case, the base resin is at least one selected from the group consisting of liquid silicone rubber (LSR), fluororubber (FR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR) and chloroprene rubber (CR). It may include rubber. In addition, the additive for regulating resistivity may be a glycol-based organic conductive filler. . Herein, the glycol-based organic conductive filler may include polyglycol ether. In addition, based on the total amount of the insulation composition, the content of the organic conductive filler may be 0.1 to 5 weight. In this case, the additive for regulating resistivity may further include an inorganic conductive filler. Also. In order to solve the above problems, the present invention is an ultra-high voltage DC power cable system including a dual junction box for electrically connecting a pair of ultra-high voltage DC power cable and the pair of DC power cable, the ultra-high voltage DC power cable And a cable core portion including a silver conductor, an inner semiconducting layer surrounding the conductor, a cable insulation layer surrounding the inner semiconducting layer, and an outer semiconducting layer surrounding the insulation layer, and including a conductor connection part electrically connecting the conductors to each other. The intermediate junction box comprises: a first electrode having rounded left and right ends in the longitudinal direction of the intermediate junction box; A pair of crab 2 electrodes formed to face each other at a predetermined distance from the first electrode to the left and right in the longitudinal direction of the intermediate junction box; And formed to surround the first electrode and the second electrode, the image being made of an elastic material which is contractible in the upper portion, and formed of an enlarged sleeve having a through hole therein in the longitudinal direction therein, and leakage of current to the outside of the intermediate junction box. with a joint sleeve comprising junction box insulating portion to prevent, and the junction box ^section, edge of the first insulating layer and the second comprises an insulating layer, the second insulating layer has a volume resistivity than the first insulating layer And the second insulating layer surrounds at least a portion of the innermost surface of the joint sleeve, the interface between the first electrode and the junction box insulation, and the interface between the second electrode and the junction box insulation. A cable system can be provided.

In this case, the thickness of the first insulating layer satisfies Equation 1 below. [Equation 1]

-ᅳ <BDV _m

^U PMJ In Equation 1, U ₀ is the rated voltage of the intermediate junction box for the ultra-high voltage DC power cable, 1.85U ₀ is the basic impuls insulation level (BIL: Basic impuls insulation level). Dp _MJ may be a thickness of the first insulating layer on the first electrode, and BDV _PMJ may be an insulation breakdown voltage of the first insulation layer 340.

The second insulating layer may be formed to cover both the first electrode and the second electrode such that the first electrode and the second electrode do not contact the first insulating layer.

Here, the second electrode may gradually increase as the vertical distance from the innermost surface of the joint sleeve toward the first electrode.

In addition, a junction box shielding layer provided outside the joint sleeve and shielding an electric field leaking out of the intermediate junction box; And

The first insulating layer, the second insulating layer and the junction box shielding layer is provided with a three-point contact with each other.

The distance between the first electrode and the triode may be greater than the distance between the first electrode and the second electrode. Here, the first insulating layer and the second insulating layer has a volume resistivity of 1 × ^{10 14} to 1 X 10 Q cm, the volume resistivity of the second insulation layer is 10 times lower than the volume resistivity of the first insulation layer and the volume resistivity of the cable insulation layer, and the volume resistivity of the first insulation layer is the cable. It may be 10 times higher than the volume resistivity of the insulating layer. In addition, the volume resistivity ratio of the cable insulating layer and the second insulating layer may be 20 or more.

In this case, the second insulating layer includes a base resin and an additive for adjusting resistivity,

The base resin comprises at least one rubber selected from the group consisting of liquid silicone rubber (LSR), fluororubber (FR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR) and chloroprene rubber (CR). Including

The resistivity adjusting additive may be a glycol-based organic conductive filler. In addition, the glycol-based organic conductive filler may include polyglycol ether.

Herein, the content of the organic conductive filler may be 0.1 to 5% by weight, based on the total amount of the insulation composition.

Also. The resistivity adjusting additive may further include an inorganic conductive filler.

【Effects of the Invention】

The intermediate junction box for the ultra-high voltage direct current power cable according to the present invention prevents breakdown of the junction box by effectively mitigating an electric field in a region where the electric field can be structurally concentrated. It shows an excellent effect that can be done.

[Brief Description of Drawings]

1 is a schematic cross-sectional view of a conventional power cable system. Figure 2 schematically shows a longitudinal cross-sectional view of the DC power cable of the ultra-high voltage DC power cable system according to the present invention.

Figure 3 schematically shows the cross-sectional structure of the ultra-high voltage DC power cable system according to the present invention.

4 is a graph showing the electric field analysis and the line loss at the triple point.

FIG. 5 is a graph showing an equipotential line distribution between a first electrode and a second electrode in an embodiment. FIG.

[Best form for implementation of the invention]

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosure may be made thorough and complete, and the spirit of the present invention may be fully conveyed to those skilled in the art. Like numbers refer to like elements throughout.

Figure 2 schematically shows a longitudinal cross-sectional view of the ultra-high voltage DC power cable in the ultra-high voltage DC power cable system according to an embodiment of the present invention.

Referring to FIG. 2, the ultra-high voltage DC power cable 200 includes a conductor 210, an inner semiconducting layer 212, an insulating layer 214, and an outer semiconducting layer 216, along the conductor 210. It is provided with a cable core portion that transmits power only in the longitudinal direction and prevents leakage of current in the radial direction of the cable.

The conductor 210 serves as a passage through which current flows to transmit power, and has a high conductivity and a strength and flexibility suitable for cable manufacture and use, such as copper or aluminum, to minimize power loss. And the like. The conductor 210 may be a circular compressive body compressed into a circular shape by twisting a plurality of circular small wires, and the flat rectangular wire 210B is wrapped around the central center wire 210A and the circular core core wire 210A. It may be a flat conductor having a flat wire layer (210C) consisting of a circular cross section as a whole, the flat conductor has the advantage of reducing the outer diameter of the cable is relatively high spot ratio compared to the circular compressed conductor.

However, since the conductor 210 is formed by twisting a plurality of element wires, its surface may not be smooth, and thus an electric field may be uneven, and corona discharge is likely to occur partially. In addition, when a gap is formed between the surface of the conductor 210 and the insulating layer 214 described later, the insulating performance may be reduced. In order to solve the above problems, the inner semiconducting layer 212 is formed outside the conductor 210.

The inner semiconducting layer 212 may have semiconductivity by adding conductive particles such as carbon black, carbon nanotubes, carbon or no plate, and graphite to an insulating material. It prevents abrupt electric field change between and stabilizes ¾ performance. In addition, by suppressing the uneven charge distribution on the conductor surface, the electric field is made uniform, and the gap between the conductor 210 and the insulating layer 214 is prevented to prevent corona discharge, insulation breakdown, and the like. The outer side of the inner semiconducting layer 212 is provided with an insulating layer 214 to electrically insulate the outside so that the current flowing along the conductor 210 does not leak to the outside. In general, the insulation layer 320 has a high breakdown voltage and should be able to be stably maintained for a long time. Furthermore, the dielectric loss is low and must have heat resistance such as heat resistance. Accordingly, the insulating layer 214 may be a polyolefin resin of polyethylene and polypropylene, more preferably a polyethylene resin. Here, the polyethylene resin may be made of a crosslinked resin.

The outer semiconducting layer 216 is provided outside the insulating layer 214. The outer semiconducting layer 216 is formed of a material having semiconductivity by adding conductive particles, such as carbon black, carbon nanotubes, carbon nanoplates, graphite, etc., to an insulating material like the inner semiconducting layer. The nonuniform charge distribution between the insulating layer 214 and the metal sheath 218 described later is suppressed to stabilize the insulating performance. In addition, the outer semiconducting layer 216 smoothes the surface of the insulating layer 214 in the cable to mitigate electric field concentration, thereby preventing corona discharge, and also physically protects the insulating layer 214. .

The core part may further include a moisture absorbing part (not shown) to prevent moisture from penetrating the cable. The moisture absorbing portion may be formed between stranded wires and / or outside the conductor 210, and has a high speed of absorbing moisture penetrating into the cable and has excellent ability to maintain the absorbed state (super absorbent po). It is composed of a powder, a tape, a coating layer or a film including a lymer (SAP), and serves to prevent moisture from penetrating in the cable length direction. In addition, the moisture absorbing portion may have a semiconductivity to prevent a sudden electric field change. A protective sheath part is provided on the outside of the core part, and a power cable installed in an environment exposed to moisture such as the sea bottom additionally includes an exterior part (not shown). The protective sheath and the sheath protect the cable core from various environmental factors such as moisture penetration, mechanical trauma, and corrosion, which can affect the power transmission performance of the cable.

The protective sheath portion includes the metal sheath 218 and the inner sheath 220 to protect the cable from accidental currents, external forces or other external environmental factors.

The metal sheath layer ₂₁₈ is grounded at the end of the power cable to serve as a passage through which an accident current flows in the event of a ground fault or short circuit, to protect the cable from external shocks, and to prevent the electric field from being discharged to the outside of the cable. Can be. In addition, in the case of a cable installed in an environment such as a seabed, the metal sheath may be formed to seal the core part, thereby preventing foreign substances such as moisture from invading and deteriorating insulation performance. For example, by extruding the molten metal to the outside of the core portion to form a seamless continuous outer surface having a superior ordering performance can be made. As the metal, lead or aluminum is used. In particular, in the case of submarine cables, it is preferable to use lead having excellent corrosion resistance to seawater, and alloy lead containing metal element to supplement mechanical properties. more preferably, all oy).

Also. The metal sheath 218 is coated with an anti-corrosion compound, such as blown asphalt, to the surface to further improve the corrosion resistance, water resistance, etc. of the cable and to improve adhesion to the inner sheath 220. Can be. In addition, between the metal sheath 218 and the core portion, a copper direct tape (not shown) to a moisture absorbing layer (not shown) May be additionally provided. The copper wire direct tape is composed of copper wire and nonwoven tape to facilitate electrical contact between the outer semiconducting layer and the metal sheath layer, and the moisture absorbing layer (not shown) absorbs moisture that has penetrated the cable. It is composed of powder, tape, coating layer or film containing super absorbent resin (SAP) which has high absorption rate and excellent ability to maintain the absorption phase Efl. Serves to prevent this from happening. In addition, in order to prevent a sudden electric field change in the moisture absorbing layer may be configured to include a copper wire in the moisture hop layer.

On the outside of the metal sheath 218 is formed an inner sheath 220 made of a resin such as polyvinyl chloride (PVC), polyethylene (po lyethy lene), etc. to improve the corrosion resistance, orderability, etc. of the cable, mechanical It can function to protect cables from trauma and other external environmental factors such as heat and ultraviolet rays. In particular, in the case of power cables laid on the sea floor, it is preferable to use polyethylene resin having excellent degree of orderability, and polyvinyl chloride resin is preferably used in an environment where flame retardancy is required.

The protective sheath portion is formed on a metal reinforcement layer (not shown) made of a galvanized steel cape or the like, and is formed on the upper and / or lower portion of the metal reinforcement layer and is made of a semiconductive nonwoven tape to complete an external force applied to a power cable. It further includes an external sheath (not shown) composed of a bedding layer (not shown) and resins such as polyvinyl chloride to polyethylene to further improve corrosion resistance and abrasion resistance of the power cable. The cable can be further protected against external environmental factors. In addition, power cables laid on the sea floor may be injured by anchors of ships. Since it may be easily damaged by bending current due to currents or waves, friction with sea bottoms, etc., an exterior portion (not shown) may be formed outside the protective sheath portion to prevent this.

The exterior part may include an armor layer (not shown) and a serving layer (not shown). The armor layer may be made of steel, galvanized steel, copper, brass, bronze, etc., and may be configured as at least one layer by cross winding a wire having a circular cross section or a flat shape. The armor layer 34 not only serves to enhance the mechanical properties and performance of the cable, but also additionally protects the cable from external forces. The serving layer composed of polypropylene yarn or the like is formed in one or more layers on the upper and / or lower portion of the armor layer to protect the cable, and the outermost serving layer is formed of two or more materials having different colors. 3 is a schematic cross-sectional view of an intermediate junction box for an ultra high voltage direct current power cable according to an embodiment of the present invention, and an ultra high voltage direct current power cable system including the same. It is.

As shown in Figure 3, the ultra-high voltage power cable system according to the present invention and a pair of power cable. A conductor connecting portion 310 surrounding the ends of the conductor 210 and the insulating layer 214 of the pair of power cables and electrically connecting the conductor 210, wherein the conductor connecting portion 310 and the han It may comprise an intermediate junction having a joint sleeve 320 made of an elastic material shrinkable at an upper end of the pair of power cable ends. In addition, the outer side of the joint sleeve 320 is electrically connected to the outer semiconducting layer 216 to the metal sheath 218 of the pair of power cables to the power cable A junction box shielding layer 324 serving as an outer semiconducting layer of a cable, a housing (not shown) consisting of a metal casing (met al cas ing) surrounding the joint sleeve 320, and the housing and the joint It may further include a waterproof material (not shown) disposed in the space between the sleeve 320 and the like.

As shown in FIG. 2, the pair of power cables includes a conductor 210, an inner semiconducting layer 212 surrounding the conductor 210, and a cable 껄 soft layer 214 surrounding the inner semiconducting layer 212. And a cable core including an outer semiconducting layer (216) surrounding the insulating layer (214). At each end, the conductor 210, the inner semiconducting layer 212, the cable insulation layer 214, and the outer semiconducting layer 216 are sequentially exposed to face each other. The conductor connection part 310 includes a conductor fixing part for electrically connecting and fixing a pair of conductors 210 exposed at each end of the pair of power cables, and the conductor fixing part and the pair of power cables. It may include a connecting sleeve surrounding the end of the insulating layer 214 exposed at the end. The conductor fixing part may be formed by inserting a sleeve into the pair of conductors and compressing the outer circumferential surface of the sleeve, fixing the pair of conductors inserted into the sleeve with bolts through the sleeve, or welding the conductor ends to each other. The conductor 210 or the conductor fixing part may be configured to be electrically connected to the connection sleeve through a braided wire.

The joint sleeve 320 is made of an elastic material that can be contracted at room temperature, and is formed of a thickening sleeve having a through hole therein in the longitudinal direction, and a pair of cables electrically connected to each other by the conductor connecting portion 310, Specifically, each of the insulating layer 214, the outer semiconducting layer 216, and the conductor exposed at the ends of the pair of cables The contact portion 310 is in close contact with the elastic restoring force. In addition, the junction box including a junction box to prevent the leakage of current outside the junction box, at least a portion of the innermost surface of the joint sleeve 320 may be made of the junction box insulation. Specifically, the junction insulation may be in close contact with the conductor connecting portion by the elastic restoring force.

In addition, the joint sleeve 320 is provided in a pair to face each other in the first electrode 321 to the intermediate junction box 300 that is electrically connected to the conductor connection portion 310 of the pair of power cables. And a second electrode 322 electrically connected to the outer semiconducting layer 216 to the metal sheath 218 of the pair of power cables, wherein the first electrode 321 and the second electrode ( 322 may be surrounded by the junction box insulation.

The first electrode 321 and the second electrode 322 serve to spread the electric field evenly without being locally concentrated therebetween.

In detail, the first electrode 321 has a shape in which the left and right ends are rounded in the longitudinal direction of the power cable to the intermediate junction box, and are made of a semiconductive material and are provided outside the conductor connection part 310. And electrically connected to the conductor connecting portion 310 and the conductor 210 to serve as a so-called high voltage electrode (el ect rode).

The second electrode 322 is made of a semiconductive material, preferably the same material as the first electrode 321, the left side of the power cable to the expansion junction from the first electrode 321 in the longitudinal direction And a pair provided to face each other at a predetermined distance to the right, and are electrically connected in contact with the outer semiconducting layer 216 of the power cable to serve as a so-called shield electrode. Also, the pair of first The second electrode 322 increases as the vertical distance from the innermost surface of the joint sleeve 320 or the cable insulation layer 214 toward the first electrode 321 increases, and the increase rate of the vertical distance increases. FIG. 1 is provided in an enlarged shape toward the first electrode 321, and a surface facing the first electrode 321 is formed as a curved surface.

therefore. The first electrode 321 and the second electrode 322 are formed in a rounded shape or rounded end, and between the first electrode 321 and the second electrode 322 according to the shape of each electrode. Equipotential lines are distributed to control the electric field distribution.

The junction box insulation part is provided to surround the first electrode 321 and the second electrode 322 to prevent the leakage of current flowing in the ultra-high voltage cable system to the outside to ensure insulation performance.

On the other hand, in the case of an AC power cable system, the electric field in the cable insulation layer and the junction box insulation is dependent on the dielectric constant of the cable insulation layer and the junction box ¾ edge, and the dielectric constant does not change greatly with temperature, so Predictive and junction box design is easy. On the other hand, in the DC power cable system, the electric field distribution in the cable insulation layer and the junction box insulator has a resistive electric field distribution characteristic depending on the volume resistivity of the cable insulation layer and the junction box insulator. Because of the high electric field, and the volume resistivity is temperature dependent, it is extremely difficult to design the junction box considering the electric field distribution.

In particular, the first electrode 321 ′ to the second electrode 322 ′ are connected to the junction insulator 323 ′ and / or the cable insulation layer 214, as in the conventional junction box for the power cable of FIG. 1. In the parts in contact with each other, different materials having different volume resistivity are in contact with each other. If the DC current flows through the cable and the temperature change occurs, not only the volume resistivity changes but also the change rate varies depending on the material, which makes it difficult to predict the electric field distribution and may cause a problem that the electric field is locally concentrated. Also, when the power cable system is manufactured, the low U electrode 321 ^′ to the second electrode 322 ′ are connected to a portion where air gaps or foreign substances are formed in contact with the insulation portion 323 ᅳ and / or the cable insulation layer 214. There is a possibility of this intrusion, and there is a fear of occurrence of dielectric breakdown when a high field is applied to a portion where the voids or foreign matter occurred.

In order to solve this problem, the junction box insulating part of the present invention is surrounded by the first insulating layer 323 and the first insulating layer 323 and forms a second at least part of the innermost surface of the joint sleeve 320. An insulating layer 325 is provided.

The first insulating layer 323 is a liquid silicone rubber (LSR), fluorine rubber (FR), styrene-butadiene rubber (SBR) excellent in insulation performance to ensure the insulating performance of the intermediate junction box. A first insulating composition comprising nitrile-butadiene rubber (NBR), chloroprene rubber (CR), ethylene propylene diene monomer (EPDM) rubber or combinations thereof, preferably the composition has a tear strength and permanent Long-term reliability, such as change rate is excellent, and may include a liquid silicone rubber having the advantage of improving productivity in a rapid production process. In addition, the silicone rubber can be molded in a variety of design products is improved moldability. Secondary vulcanization is unnecessary and has various advantages that can be molded by double injection. .

The second insulation layer 325 is formed between the first insulation layer 323 and the cable insulation layer 214 in various forms, such as a tube, coating, film, and the like, in particular the joint sleeve 320 At least one surface selected from the group consisting of an interface between the first electrode 321 and the junction box insulation and an interface between the second electrode 322 and the junction box insulation. At least partially wrapped, preferably formed to surround a portion where the first electrode 321 or the second electrode 322, the junction box insulation, and / or the cable insulation layer 214 meet. As the volume resistivity changes, the electric field may be concentrated or there may be gaps or foreign matter intrusion. Therefore, the electric field of the part where the insulation performance is unstable is alleviated.

The second insulating layer 325 is formed of a second insulating composition having a lower volume resistivity than the cable insulating layer 214, and the portion of which the insulation performance is relatively stable is applied to an electric field applied to a portion that may cause breakdown. Can be dispersed.

The second insulating composition may include a base resin and an additive for adjusting resistivity. The base resin may have a volume resistivity of 10 ¹⁵ Q cm or less, an insulation strength of 10 kV / mni or more, preferably a break strength of 10 N / 隱 or more, and an elongation of 200% or more. The base resin is, for example, liquid silicone rubber (LSR), fluorine rubber (FR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), chloroprene rubber (CR), ethylene propylene diene monomer (EPDM) It is preferable to include a liquid silicone rubber that can be made, including rubber or a combination thereof, excellent long-term reliability, such as tear strength and permanent change rate, and has the advantage of improving productivity in a rapid production process More preferably for close contact with the first insulating layer 323. It may be made of the same series of resins as.

The resistivity adjusting additive may include an organic conductive filler alone or a combination of an organic conductive filler and an inorganic conductive filler. The organic conductive filler is a glycol-based filler such as ethylene glycol, propylene glycol, preferably polyglycol ether in consideration of compatibility with the base resin and electrical and mechanical properties of the second insulating layer 325. (po lyg lyco l ether; PGE), and the organic conductive filler may further improve the electrical and mechanical properties of the second insulating layer 325 by forming a chemical crosslink with the base resin. Can be. In addition, there is an advantage that can be easily dispersed in the base resin compared to the inorganic conductive filler to facilitate the volume resistivity adjustment.

The second insulating composition and the second insulating layer 325 formed therefrom are in accordance with the volume resistivity of each of the insulating layer 214 and the first insulating layer 323 of the cable in contact with the second insulating layer 325. By maintaining a precisely controlled volume resistivity, it is possible to effectively distribute the electric field in the region where the electric field can be concentrated inside the intermediate junction box (300).

Specifically, the second insulating composition may have a volume resistivity of less than or equal to the maximum volume resistivity (^) defined by Equation 1 below at 70 ° C. Thus, when the cable to be connected is a DC power cable, the second insulating layer 325 formed from the second insulating composition has a temperature change due to a cable conduction state, and thus the cable insulating layer, the first insulating layer, and the second insulating layer. By having the optimum volume resistivity according to the change of electric field distribution in the back, it is possible to maximize the field relaxation effect in the area where the electric field can be structurally concentrated.

[Equation 1]

In Equation 1,

f _min (aX, bY) means the minimum of aX and bY,

X is the volume resistivity at 7 (C of the cable insulation layer,

Y is the volume resistivity at 70 ^° C. of the first insulating layer,

b is at least 2a.

b is 0.05 to 0.15,

a is 0.025 to 0.075.

The electric field by the second insulating layer 325 formed from the second insulating composition when the second insulating composition has a volume resistivity exceeding the maximum volume resistivity („) defined by Equation 1 at 70 ^° C. Dispersion effect is not good enough, and the electric field concentration can cause junction breakdown.

The second insulating composition has a maximum volume resistivity defined by Equation 1 at 70 ^° C. For example, based on the total increase of the second insulating composition, the content of the resistivity adjusting additive is 0.1 to 5% by weight. Preferably it may be 0.5 to 3% by weight.

In addition, the first insulation layer 323, the second insulation layer 325, and the cable insulation layer 214 have a volume resistivity of 1 × ^{10 12} to 1X10 ¹⁸ Ωαιι, and the volume of the second insulation layer 325. Resistivity is the volume resistivity of the first insulating layer 323 and the volume of the cable insulation 214 The resistivity may be 10 times lower than each, and the volume resistivity of the first insulating layer 323 may not be higher than 10 times higher than the volume resistivity of the cable insulation layer 214. In particular, the volume resistivity of the cable insulation layer 214 may be 10 ¹⁴ to 10 ¹⁸ Ω αιι, and the volume resistivity of the first insulation layer 323 may be 10 ¹⁴ to 10 ¹⁸ Ω ιι. The volume resistivity ratio of the cable insulation layer 214 and the second insulation layer 325 preferably satisfies Equation 2 below, and the lower limit of the volume specific resistance of the second insulation layer 325 is 10 ¹² Ω. may be αΐΓ.

Equation 2

(Volume resistivity of cable insulation layer / Volume resistivity of second insulation layer) ≥20

When the volume resistivity of the second insulation layer 325 is not more than 10 times lower than the volume resistivity of the first insulation layer 323 and the volume resistivity of the cable insulation layer 214, respectively, the electric field of the second insulation layer When the dispersing effect may be significantly lowered and the volume resistivity of the first insulation layer 323 is 10 times higher than the volume resistivity of the cable insulation layer 214, an excessively large electric field is formed in the first insulation layer. If the volume resistivity of the cable insulation layer 214 and the first insulating layer 323 is out of the above range, it may not satisfy the insulation characteristics required for the transmission of ultra-high voltage DC power.

In addition, when the volume resistivity ratio (volume resistivity of the cable insulation layer / volume resistivity of the second insulation layer) of the cable insulation layer 214 and the second insulation layer 325 is less than 20, as shown in FIG. As described above, the electric field at the triple point (Tr iple Po i nt) where the second electrode 322, the second insulating layer 325, and the cable insulating layer 214 contact each other rises rapidly, and the second insulating layer (325) When the volume intrinsic resistance is less than the lower limit, excessive heat is generated in the second insulating layer 325 due to Joule loss as shown in FIG. 4 (b).

As described above, an intermediate junction box for an ultra-high voltage DC power cable according to an embodiment of the present invention having a junction box insulator including a first insulation layer 323 and a second insulation layer 325, and an ultra-high voltage including the same. In the DC power cable system, the interface between the first insulating layer 323 and the second insulating layer 325 is preferably not in contact with the first electrode 321 and the second electrode 322.

Specifically, the first electrode 321 and the second electrode 322 are surrounded by the second insulating layer 325 without contacting the first insulating layer 323, the joint sleeve 320 ) Is a first triple point (P1), the second electrode 322, the second insulating layer (1) where the first electrode 321, the second insulating layer 325 and the cable insulating layer 214 abut each other. The second triple point P2 in which the 325 and the cable insulation layer 214 contact each other, the junction box shielding layer 324, the first insulation layer 323, and the second insulation layer 325 contact each other. It may be provided with a third tritium (P3).

in this case. The electric field acting on the first triple point and the second triple point according to the resistive electric field distribution characteristic during direct current transmission is determined by the difference in volume resistivity between the low 2 insulating layer 325 and the first insulating layer 323. Shifted to the insulating layer 323, the spacing of the equipotential lines generated in the second insulating layer 325 1 evenly distributed in the second insulating layer 325 when the power cable system is placed under a direct current electric field. As the inorganic conductive filler becomes wider and becomes relatively constant, the electric field is concentrated in the local field concentration in the second insulation layer 325, in particular, the first triple point P1 and the second triple point P2. To be It can be suppressed.

However, due to the difference in volume resistivity between the second insulating layer 325 and the first insulating layer 323, the electric field of the second insulation layer 325 is shifted to the low 1 1 insulating layer 323 (sh ift). Therefore, the electric field is concentrated on the third tri-dot (P3) in which the elements consisting of three kinds of materials having different volume resistivity, including the first insulating layer 323 is in contact with each other to act as a weak insulation.

In order to solve the above-described problem, the third triple point P3 is spaced apart from the curved surface of the second electrode 322 facing the first electrode 321 by a predetermined distance in a direction opposite to the first electrode 321. It is preferably formed so as to be farther from the first electrode 321 than the second electrode 321. When the electric field is shifted from the second insulating layer 325 to the first insulating layer 323, the shifted electric field is shaped like the first electrode 321 and the second electrode 322, and the first and second electrodes 322. Corresponding to the region of the second insulating layer 325 between the pair of second electrodes 322 of the first insulating layer due to the volume resistivity between the electrodes 321, 322 and the second ¾ lead layer 325, etc. A high field is applied relative to the part.

Thus, the third triple point can be formed farther from the first electrode 321 than the second electrode 322. Preferably, the distance tl between the third triple point P3 and the first electrode 321 is formed to be greater than the distance t2 between the first electrode and the second electrode, so that By eliminating the high electric field, natural performance can be improved.

On the other hand, on the interface between the second insulating layer 325 and the first insulating layer 323 surrounding the first tri-dot and the first electrode 321, the first insulating worm 323 is next It may have a thickness that satisfies the equation (3).

[Equation 3]

Here, U ₀ is the rated voltage of the intermediate junction box having the joint sleeve 320,

1.851)。 is the brain impulse test voltage (BIL; Bas ic impul s insul at ion level). 0 ^ is the thickness of the first insulating layer 323 formed on the interface between the second insulating layer 325 and the first insulating layer 323 surrounding the first triple point and the first electrode 321. And BDV _f is the breakdown voltage of the first insulating layer 323. That is, the first insulation layer 323 is formed so that the value obtained by dividing the crimp spread test voltage of the intermediate junction by the thickness of the first insulation layer 323 is smaller than the insulation breakdown voltage value of the first insulation layer 323. Can be formed. In other words, the thickness of the insulation 11 layer 323 is greater than the brain impulse test voltage (1 .85 U ₀ ) of the intermediate junction divided by the dielectric breakdown voltage value (BDW) of the first insulation layer 323. The first insulating layer 323 has a higher volume resistivity than the second insulating layer 325, and in particular, has a higher electric field on the first electrode 321 than the second insulating layer 325. As described above, the thickness of the first insulating layer ₃₂₃ having a high electric field sharing is as described above, and the brain breakdown test voltage (1.851U) of the intermediate junction box is equal to the dielectric breakdown voltage of the first insulating layer 323. If smaller than the value divided by the value (BDV _PMJ ), the electric force in the first insulating layer 323 As the line density increases, insulation breakdown may occur in the first insulating layer 323. Therefore, in one embodiment of the present invention, the thickness of the first insulating layer 323 is equal to or greater than that of the brain impilation test voltage (1 .85 U ₀ ) of the first insulation layer 323. _It is possible to prevent the occurrence of dielectric breakdown in the first insulating layer 323 by being larger than the value divided by _PMJ ). As an example, the first insulating layer 323 may be formed on the first electrode 321 so that its thickness is three times or more than the thickness of the second insulating layer 325.

The intermediate junction box joint joint 320 for a cable according to the present invention may include, for example, inserting a mold into a molding mold and injecting a semiconductive material into the mold, thereby forming the first electrode 321 and the second electrode 322. ), And then injecting the composition and the insulating composition for controlling the electrical conductivity into the molding mold and then cured to form a crab 2 insulating layer and a first insulating layer. In addition, the second insulation layer surrounds at least a portion of an interface to a point where the first electrode 321 to the second electrode 322 are formed in contact with the junction box insulation portion and / or the cable insulation layer. 2 may be prepared by applying and curing the insulating composition.

EXAMPLE

1. Manufacturing Example

It has a volume resistivity as shown in Table 1 below. Ratio with junction box insulator having the same structure except that the intermediate junction box of the embodiment with junction box insulation having the second insulation layer 325 shown in FIG. The middle three of each of the lessons were prepared.

Table 1

2. Equipotential line distribution and electric field value evaluation

Example and Comparative Example The equipotential line distribution in the space between the first electrode and the second electrode measured at 70 ^° C. with a voltage of 592 kV applied to each intermediate junction box is as shown in FIG. The electric field values are shown in Table 2 below.

[Table 2]

-Interface 1: Cable insulation layer-1st insulation layer interface

-Triplet: cable insulation layer-1st insulation layer-2nd electrode

Interface 2: First insulating layer First electrode

As shown in FIG. 5, the indirect flux of the embodiment according to the present invention having the second insulating layer has a small distance between the equipotential lines between the first electrode and the second electrode, so that the electric field is not concentrated locally. 2 The intermediate junction box of the comparative example without the insulation layer had a region where the electric field was concentrated due to the narrow gap between the equipotential lines, and as shown in Table 2, the intermediate junction box of the example was structurally concentrated. Whereas the electric field in the possible area is considerably relaxed, the incremental junction of the comparative example is structurally It was confirmed that the electric field was concentrated in the area where it can be collected.

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

Claims

[Range of request]

[Claim 1]

In the intermediate connection for the ultra-high voltage DC power cable for connecting a pair of ultra-high voltage DC power cable including a conductor, an inner semiconducting layer surrounding the conductor, an insulating layer surrounding the inner semiconducting layer, and an outer semiconducting layer surrounding the insulating layer. .

First electrodes having rounded left and right ends in the longitudinal direction of the intermediate junction box;

A pair of second electrodes spaced apart from each other by a predetermined distance in the longitudinal direction of the intermediate junction box from the first electrode to face each other; And

It is formed to surround the first electrode and the second electrode, the image is made of a resilient material that is contractible in, is formed of a hollow sleeve having a through hole in the longitudinal direction therein, the current leakage to the outside of the intermediate junction box And a joint sleeve including junction box insulation to prevent damage.

The junction box insulating portion includes a first insulating layer and a second insulating layer,

The 12 insulating layer has a lower volume resistivity than the 1 insulating layer,

The second insulation layer covers at least a portion of an interface of the innermost surface of the joint sleeve and the interface between the first electrode and the junction box insulation, and an interface between the second electrode and the junction box insulation. box.

[Claim 2]

According to claim 1,

The thickness of the first insulating layer is characterized by satisfying the following equation Intermediate junction box for high voltage DC power cables.

Equation 1 DV ^ ᅳ ᅳ <DV _PM3

PMJ In Equation 1,

Uo is the rated voltage of the intermediate junction box for the ultra-high voltage DC power cable,

1.85U ₀ is the basic impuls insulation level (BIL),

DBU is the thickness of the first insulating layer on the first electrode, BDV _PMJ is the breakdown voltage of the first insulating layer 340,

[Claim 3]

The method of claim 1,

The second insulating layer is formed to cover both the first electrode and the second electrode so that the first electrode and the second electrode does not contact the first insulating layer, characterized in that for the ultra-high voltage DC power cable Extra connection.

[Claim 4]

The method according to any one of claims 1 to 3,

The second electrode is an ultra-high voltage DC power cable, characterized in that the vertical distance from the innermost surface of the joint sleeve gradually increases toward the first electrode Intermediate junction box.

[Claim 5]

The method of claim 4, wherein

A junction box shielding layer provided outside the joint sleeve to shield an electric field leaking outside the intermediate junction box; And

And the first insulating layer, the second insulating layer, and the junction box shielding layer are in contact with each other.

An incremental junction box for an ultra high voltage direct current power cable, wherein a distance between the first electrode and the triple point is greater than a distance between the first electrode and the second electrode.

[Claim 6]

The volume resistivity of the first insulation layer and the second insulation layer is IX 10 ¹⁴ to IX 10 ¹⁸ Ω cm, and the volume resistivity of the second insulation layer is equal to the volume resistivity of the first insulation layer. Intermediate junction box for ultra high voltage DC power cables, characterized by more than 10 times lower.

[Claim 7]

The method of claim 1,

The second insulating layer is an intermediate junction box for an ultra-high voltage DC power cable, characterized in that formed of a second insulation composition comprising a base resin and a resistivity control additive.

[Claim 8]

The method of claim 7, wherein The base resin may include at least one rubber selected from the group consisting of liquid silicone rubber (LSR), fluorine rubber (FR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR) and chloroprene rubber (CR). Extra junction box for ultra-high voltage DC power cable, characterized in that it comprises a.

[Claim 9]

The method of claim 7, wherein

The resistivity control additive is an intermediate junction box for ultra-high voltage direct current power cable, characterized in that the glycol-based organic conductive filler.

[Claim 10]

The method of claim 9,

The glycol-based organic conductive filler is an extra junction for an ultra high voltage DC power cable, characterized in that it comprises a polyglycol ether.

[Claim 11]

The method of claim 10,

Based on the total weight of the insulating composition, the content of the organic conductive filler is an intermediate junction box for ultra-high voltage DC power cable, characterized in that 0.1 to 5% by weight.

[Claim 12]

The method of claim 9,

The resistivity control additive is an intermediate junction box for ultra-high voltage DC power cable, characterized in that it further comprises an inorganic conductive filler.

[Claim 13] An ultra high voltage DC power cable system including an intermediate junction box electrically connecting a pair of ultra high voltage DC power cables and the pair of DC power cables to each other, wherein the ultra high voltage DC power cables include a conductor and an inner semiconducting layer surrounding the conductor. . And a cable core portion including a cable insulation layer surrounding the inner semiconducting layer and an outer semiconducting layer surrounding the ¾ edge layer.

A conductor connection for electrically connecting the conductors to each other;

The intermediate junction is.

And surround the first electrode and the second electrode. ^'' Made of elastic material that can shrink at room temperature. It is formed as a hollow sleeve with a through hole in the longitudinal direction therein. And a joint sleeve including a junction box insulator to prevent current from leaking out of the intermediate junction box,

The second insulating layer has a lower volume resistivity than the first insulating layer,

And the second insulating layer surrounds at least a portion of an innermost surface of the joint sleeve, an interface between the first electrode and the junction box insulation portion, and an interface between the second electrode and the junction box insulation portion.

[Claim 14] The method of claim 13,

Ultra-high voltage DC power cable system, characterized in that the thickness of the first insulating layer satisfies the following equation (1).

[Equation 1]

1.85 [/ ₀

^ ^~ <BDV _P

In Equation 1,

1.85U ₀ is the basic impuls insulation level (BIL),

DPW is the thickness of the first insulating layer on the first electrode. BDV _PMJ is the breakdown voltage of the first insulating layer 340.

[Claim 15]

The method of claim 13.

The second insulating layer is the _. An ultra-high voltage DC power cable system, characterized in that the first electrode and the second electrode is formed so as to cover both the first electrode and the second electrode so as not to contact the first insulating layer.

[Claim 16]

The method according to any one of claims 13 to 15, The second electrode is a very high voltage DC power cable system, characterized in that the vertical distance from the innermost surface of the joint sleeve gradually increases toward the first electrode

[Claim 17]

The method of claim 16,

The first insulating layer, the second insulating layer, and the junction box shielding layer having three midpoints in contact with each other _, wherein a distance between the first electrode and the triple point is greater than a distance between the first electrode and the second electrode. Ultra high voltage DC power cable system.

[Claim 18]

The method of claim 13,

14 i8 The first insulating layer and the second insulating layer have a volume resistivity of 1 X 10 to 1 X 10 Ω cm, and the volume resistivity of the second insulating layer is the volume resistivity of the first insulating layer and the cable insulation. And a volume resistivity of the first insulation layer is 10 times higher than that of each of the layers, and the volume resistivity of the first insulation layer is 10 times higher than the volume resistivity of the cable insulation layer.

[Claim 19]

The method of claim 18, The ultra-high voltage DC power cable system, characterized in that the volume resistivity ratio of the cable insulation layer and the second insulation layer is 20 or more.

[Claim 20]

The method of claim 13,

The second insulating layer includes a base resin and an additive for adjusting resistivity, wherein the base resin is liquid silicone rubber (LSR), fluororubber (FR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR) and chloroprene At least one rubber selected from the group consisting of rubber (CR),

The resistivity control additive is an ultra-high voltage DC power cable system, characterized in that the glycol-based organic conductive filler.

[Claim 21]

The method of claim 20,

The glycol-based organic conductive filler is ultra-high voltage DC power cable system characterized in that it comprises a polyglycol ether.

[Claim 22]

The method of claim 21,

Ultra high voltage DC power cable system, characterized in that the content of the organic conductive filler is 0.1 to 5% by weight based on the total weight of the insulating composition.

[Claim 23]

The method of claim 20,

The resistivity adjusting additive may further include an inorganic conductive filler. Ultra high voltage DC power cable system.