KR20180130161A - Joint for high voltage DC power cable and high voltage DC power cable joint system comprising the same - Google Patents

Abstract

The present invention relates to an intermediate joint for an ultra-high voltage direct current power cable and an ultra-high voltage direct current power cable connection system including the same. More particularly, the present invention relates to an intermediate joint for an ultra-high voltage direct current power cable and an ultra-high voltage direct current power cable connection system including the same, capable of preventing the accumulation of space charge by injecting a charge into a junction box insulation material applied to an intermediate joint for an ultra-high voltage direct current power cable to effectively prevent an electric field distortion due to the space charge and an insulation breakdown of the intermediate joint caused accordingly.

Description

Technical Field [0001] The present invention relates to an intermediate connection box for an ultra-high voltage direct current power cable, and an ultra high voltage direct current power cable connection system including the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate connection box for an ultra high voltage direct current power cable and an ultra high voltage direct current power cable connection system including the same. More particularly, the present invention relates to a method of manufacturing a high-voltage direct current power cable, which is capable of suppressing the accumulation of space charge by injecting a charge into a junction box insulator applied to an intermediate junction box for an ultra-high voltage direct current power cable, thereby distorting the electric field caused by the space charge, And more particularly to an intermediate connection box for an ultra high voltage direct current power cable and an ultra high voltage direct current power cable connection system including the same.

A power cable is a device that transmits electric power using an internal conductor and can be classified into a direct current (DC) power cable and an alternating current (AC) power cable. Terminals are connected to each other to enable long-distance transmission.

DC power transmission using the power cable for ultra-high voltage DC is advantageous for long-distance transmission because of low power loss. However, in a conventional high-voltage direct current transmission system including a power cable and a junction box, when a direct current high voltage is applied to the power cable or the connection box, charges are injected from the conductor into the insulation layer of the cable or the connection box, There is a problem that a space charge is formed due to the influence of the light. Particularly, there is a problem that the electric charge accumulated in the insulating layer adjacent to the conductor injected from the conductor into the insulation layer of the cable or the connection box to which the high voltage is applied causes local resistivity change and electric field distortion, thereby deteriorating the dielectric strength of the ultra high voltage DC cable system.

European Patent No. 1188209 discloses that a part of the cable insulation layer is formed as a field-controlling layer in order to solve the problem of deterioration in insulation performance due to the above-described space reduction accumulation. However, the field-controlling layer is merely to prevent dielectric breakdown by controlling the electric field distribution in the case where a space charge of a certain level or more is accumulated in the insulating layer, and prevents the space charge from being injected into the insulator It does not offer a fundamental solution.

Accordingly, it is possible to suppress the accumulation of space charge by injection of charges into the connection box insulating material applied to the intermediate connection box for the ultra-high voltage direct current power cable, thereby effectively preventing the electric field distortion caused by the space charge and the intermediate connection of the cable, , An intermediate connection box for an ultra high voltage direct current power cable, and an ultra high voltage direct current power cable connection system including the same.

The present invention relates to an intermediate connection box for cables capable of effectively preventing accumulation of space charges due to injection of charges into a connection box insulating material and effectively preventing electric field distortion caused by the space charges and intermediate breakdowns of cables due to the space charges, And to provide a cable connection system for connecting the cable.

In order to solve the above problems,

Voltage DC power cable for connecting a pair of ultra-high voltage direct current power cables in which a conductor, an inner semiconductive layer, a cable insulation layer and an outer semiconductive layer are sequentially exposed, so that current does not leak outside the intermediate connection box And a joint sleeve formed of a hollow sleeve having a through hole in the longitudinal direction inside thereof and having a charge blocking layer formed on the inner surface of the through hole of the joint sleeve, Wherein the charge blocking layer is formed of an organohalogen-based composition.

Here, the charge blocking layer may be formed of a material selected from the group consisting of a charge blocking layer of the specimen and a specimen corresponding to the charge blocking layer when the specimen including the charge blocking layer is formed on one side of the connection box insulator specimen, (FEF) defined by the following formula (1) is 1.5 or less when a voltage is applied to the electrode at an electric field of 20 kV / mm at room temperature for 1 hour. The present invention provides an intermediate connection box for an ultra high voltage direct current power cable.

[Equation 1]

FEF = maximum field value / applied field value

In the above equation (1)

The applied electric field value is 20 kV / mm as an electric field applied to the electrodes which are respectively in contact with the other surfaces of the charge blocking layer and the corresponding connection box insulating portion specimen,

The maximum electric field value is a maximum value of electric field values increased by electric field distortion due to the space charge accumulated in the specimen when an electric field of 20 kV / mm is applied to the specimen for 1 hour.

When the oil composition for forming the charge blocking film is heated to 70 캜 and the oil composition is impregnated with the specimen of the connecting portion, the weight change ratio of the specimen when the oil composition is saturated and contained in the specimen is 10% And a rate of change in thickness of 5% or less, a tensile residual rate of the specimen being more than 80%, and an elongation percentage being more than 95%.

And the charge blocking layer is an organic halogen-based oil to a grease.

Wherein the charge blocking layer comprises a fluorine-based oil.

Also provided is an intermediate junction for an ultra-high voltage DC power cable, characterized in that the charge blocking layer comprises a mixture of a polyfluoropolyether (PFPE) oil component and a polytetrafluoroethylene (PTFE) solid component.

The charge blocking film has a density (20 ° C) of 1.9 g / cm 3 or more, a kinematic viscosity (40 ° C) of 420 mm 2 / s or more and a dynamic viscosity (100 ° C) of 40 mm 2 / Provides an intermediate connection box for power cables.

The joint sleeves are formed so that the left and right ends of the intermediate connection case in the longitudinal direction are spaced from each other by a predetermined distance from the first electrode and the first electrode in the lengthwise direction of the intermediate connection case, And a pair of second electrodes that gradually increase in the vertical distance from the innermost surface of the joint sleeve toward the first electrode, wherein the innermost surface of the first electrode, the innermost surface of the second electrode, And the charge blocking film is formed at least partially on at least one surface selected from the group consisting of the innermost surface of the insulating portion.

The base resin included in the insulating composition forming the connection box insulating portion may be at least one selected from the group consisting of a liquid silicone rubber (LSR), a fluorine rubber (FR), a styrene-butadiene rubber (SBR), a nitrile-butadiene rubber (NBR), and a chloroprene rubber ). ≪ / RTI > The present invention provides an intermediate junction box for an ultra-high voltage direct current power cable, characterized in that it comprises at least one rubber selected from the group consisting of

And a joint housing disposed outside the joint sleeve, the joint housing including a joint box shielding layer shielding an electric field leaking to the outside of the joint housing, a metal casing enclosing the joint sleeve, and a housing disposed in a space between the housing and the joint sleeve And a waterproofing material. The intermediate connection box for an ultra-high voltage direct current power cable is characterized in that it comprises at least one member selected from the group consisting of waterproof materials.

An ultra high voltage direct current power cable including a conductor, an inner semiconductive layer, a cable insulation layer and an outer semiconductive layer, and an intermediate connection box for an ultra high voltage direct current power cable connecting the pair of ultra high voltage direct current power cables to each other. And a pair of conductors exposed at the end of the power cable are electrically connected to each other so that the ends of the conductor, the inner semiconductive layer, the cable insulating layer and the outer semiconductive layer are sequentially exposed, And a connection box insulation part for preventing a current from leaking out of the intermediate connection box, wherein the connection connection part is made of an elastic material which is shrinkable at room temperature and has a through hole in the longitudinal direction, And a joint sleeve formed of a sleeve, And a charge blocking layer formed on an inner surface of the charge blocking layer, wherein the charge blocking layer is formed of an organohalogen-based composition.

Here, the charge blocking layer may be formed of a material selected from the group consisting of a charge blocking layer of the specimen and a specimen corresponding to the charge blocking layer when the specimen including the charge blocking layer is formed on one side of the connection box insulator specimen, (FEF) defined by the following formula (1) is 1.5 or less when a voltage is applied to the electrode at an electric field of 20 kV / mm at room temperature for 1 hour. An ultra high voltage direct current power cable connection system is provided.

[Equation 1]

FEF = maximum field value / applied field value

In the above equation (1)

The applied electric field value is 20 kV / mm as an electric field applied to the electrodes which are respectively in contact with the other surfaces of the charge blocking layer and the corresponding connection box insulating portion specimen,

The maximum electric field value is a maximum value of electric field values increased by electric field distortion due to the space charge accumulated in the specimen when an electric field of 20 kV / mm is applied to the specimen for 1 hour.

When the oil composition for forming the charge blocking film is heated to 70 캜 and the oil composition is impregnated with the specimen of the connecting portion, the weight change ratio of the specimen when the oil composition is saturated and contained in the specimen is 10% And the rate of change in thickness is 5% or less, the tensile residual rate of the specimen exceeds 80%, and the elongation percentage exceeds 95%.

Further, the present invention provides an ultra-high voltage direct current power cable connection system, wherein the charge blocking layer is an organic halogen oil or grease.

Here, the charge blocking layer includes a fluorine-based oil.

Further, the charge blocking layer comprises a mixture of a polyfluoropolyether (PFPE) oil component and a polytetrafluoroethylene (PTFE) solid component.

Further, the charge blocking film preferably has a density (20 ° C) of 1.9 g / cm 3 or more, a kinematic viscosity (40 ° C) of 420 mm 2 / s or more and a dynamic viscosity (100 ° C) of 40 mm 2 / Power cable connection system.

The joint sleeves are formed so that the left and right ends of the intermediate connection case in the longitudinal direction are spaced from each other by a predetermined distance from the first electrode and the first electrode in the lengthwise direction of the intermediate connection case, And a pair of second electrodes whose vertical distance from the innermost surface of the joint sleeve gradually increases toward the first electrode direction, wherein the interface between the first electrode and the conductor connection portion, the second electrode, And a charge blocking layer formed at least partially on at least one surface selected from the group consisting of an interface between the insulating layer and the outer semiconductive layer of the cable.

The base resin included in the insulating composition forming the connection box insulating portion may be at least one selected from the group consisting of a liquid silicone rubber (LSR), a fluorine rubber (FR), a styrene-butadiene rubber (SBR), a nitrile-butadiene rubber (NBR), and a chloroprene rubber The present invention provides an ultra-high voltage direct current power cable connection system, comprising at least one rubber selected from the group consisting of:

A joint housing disposed outside the joint sleeve for shielding an electric field leaking to the outside of the joint housing; a housing made of a metal casing surrounding the joint sleeve; and a housing disposed in a space between the housing and the joint sleeve And a waterproofing material. The present invention also provides an ultra-high voltage direct current power cable connection system.

The intermediate connection case for cables according to the present invention can suppress the accumulation of space charge due to the charge injection from the conductor to the connecting insulating material by forming the charge blocking film on the surface where the connecting terminal insulating material is inserted, And exhibits an excellent effect of suppressing dielectric breakdown due to local electric field concentration.

1 schematically shows a vertical cross-sectional view of an ultra-high voltage direct current power cable.
2 schematically shows a cross-sectional structure of a cable connection system according to an embodiment of the present invention.
FIG. 3 shows the result of performing the evaluation of the space charge behavior using the PEA method for Example 1 and Comparative Example 1. FIG.
Fig. 4 shows the results of evaluating the electric field distortion in Example 1 and Comparative Example 1. Fig.

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.

1 schematically shows a vertical cross-sectional view of an ultra-high voltage direct current power cable.

1, the power cable 200 includes a conductor 210, an inner semiconductive layer 212, an insulating layer 214, and an outer semiconductive layer 216, which extend along the conductor 210 in the cable longitudinal direction And a cable core portion for preventing electric current from leaking in the cable radial direction.

The conductor 210 serves as a passage through which a current flows to transmit electric power and is made of a material having excellent conductivity and strength and flexibility suitable for cable manufacturing and use such as copper or aluminum . The conductor 210 may be a circular compression conductor obtained by twisting a plurality of circular wire strands and pressing the wire into a circular shape. The conductor 210 may be a circular central wire strand 210A and a rectangular wire strand 210B stranded to surround the circular center wire element 210A And may have a circular cross section with a circular cross section. The rectangular conductor may have a relatively high drop ratio as compared with the circular compressed conductor, and thus the cable outer diameter can be reduced.

However, since the conductor 210 is formed by stranding a plurality of elemental wires, the surface of the conductor 210 is not smooth and 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 such a problem, an inner semiconductive layer 212 is formed outside the conductor 210.

The inner semiconductive layer 212 is formed by adding conductive particles such as carbon black, carbon nanotubes, carbon nanoplate, and graphite to the insulating material to have a semiconducting property. The inner semiconductive layer 212 is formed between the conductor 210 and an insulating layer 214 Thereby preventing the occurrence of a sudden electric field change and stabilizing the insulation performance. In addition, by suppressing uneven charge distribution on the conductor surface, the electric field is made uniform, and the formation of gaps between the conductors 210 and the insulating layer 214 is prevented, thereby suppressing corona discharge, dielectric breakdown, and the like.

An insulating layer 214 is provided on the outer side of the inner semiconductive layer 212 to electrically insulate the current flowing along the conductor 210 from the outside. Generally, the insulating layer 320 should have a high breakdown voltage and be able to maintain the insulating performance for a long period of time. Furthermore, it should have low dielectric loss and resistance to heat such as heat resistance. Therefore, a polyolefin resin such as polyethylene and polypropylene may be used for the insulating layer 214, and further, a polyethylene resin is preferable. Here, the polyethylene resin may be made of a crosslinked resin.

The external semiconductive layer 216 is provided outside the insulating layer 214. The outer semiconductive layer 216 is formed of a semiconductive material such as an inner semiconductive layer by adding conductive particles such as carbon black, carbon nanotube, carbon nanoplate, or graphite to an insulating material, The distribution of uneven charge between the metal sheath 214 and a metal sheath 218 described later is suppressed to stabilize the insulation performance. In addition, the outer semiconductive layer 216 smoothes the surface of the insulating layer 214 in the cable to alleviate electric field concentration, thereby preventing corona discharge and also physically protecting the insulating layer 214 .

The core portion may further include a moisture absorbing portion (not shown) for preventing moisture from penetrating into the cable. The water absorbing part may be formed between the stranded strands and / or the outer surface of the conductor 210. The superabsorbent resin (super absorbent polymer) having a high rate of absorbing the moisture permeated into the cable and excellent in the ability to maintain the absorbed state , SAP), and serves to prevent water from penetrating in the longitudinal direction of the cable. In addition, the water absorbing part may have a semiconductive property to prevent a sudden change in the electric field.

A protective sheath is provided outside the core, and a power cable installed in an environment such as a seabed which is exposed to moisture is additionally provided with an external unit (not shown). The protective sheath part and the sheath part protect the cable core part from various environmental factors such as moisture penetration, mechanical trauma, and corrosion which may affect the power transmission performance of the cable.

The protective sheath includes a metal sheath 218 and an inner sheath 220 to protect the cable from an accident current, an external force, or other external environmental factors.

The metal sheath layer 218 serves as a passage through which a fault current flows when a ground fault or a short circuit occurs in the ground at the end of the power cable and protects the cable from external impact and prevents the electric field from being discharged to the outside of the cable have. Also, in the case of a cable attached to an environment such as a seabed, the metal sheath is formed to seal the core portion, so that foreign matter such as moisture invades, thereby preventing degradation of insulation performance. For example, molten metal may be extruded outside the core portion to form a continuous outer surface having no seams to improve the order performance. In the case of a submarine cable, it is preferable to use lead which is excellent in corrosion resistance against seawater, and in order to complement mechanical properties, a lead alloy ) Is more preferably used.

The metal sheath 218 may be coated with a corrosion inhibiting compound such as a blown asphalt or the like on the surface of the metal sheath 218 in order to further improve the corrosion resistance, water repellency and the like of the cable and improve the adhesion to the inner sheath 220 . In addition, a copper wire tape (not shown) or a moisture absorbing layer (not shown) may be additionally provided between the metal sheath 218 and the core portion. The copper wire drawing tape is composed of a copper wire and a nonwoven tape to facilitate electrical contact between the outer semiconductive layer and the metal sheath layer. The moisture absorbing layer (not shown) absorbs water penetrating the cable It is composed of powder, tape, coating layer or film including super absorbent polymer (SAP) which has a high speed and excellent ability to maintain the absorption state, and prevents water from penetrating in the longitudinal direction of the cable . In order to prevent a sudden change in electric field in the water absorbing layer, a copper wire may be included in the water absorbing layer.

An inner sheath 220 made of a resin such as polyvinyl chloride (PVC) or polyethylene is formed on the outer surface of the metal sheath 218 to improve the corrosion resistance and water repellency of the cable, And other external environmental factors, such as the cable can be protected. Particularly, in the case of a power cable installed in the seabed, it is preferable to use a polyethylene resin having excellent water-repellency, and in an environment where flame resistance is required, polyvinyl chloride resin is preferably used.

The protective sheath portion may include a bed layer (not shown) made of a semiconductive nonwoven tape or the like to buffer an external force applied to the power cable, and an external sheath (not shown) made of a resin such as polyvinyl chloride or polyethylene, Corrosion resistance, water repellency, and the like, and further protects the cable from mechanical external injury and other external environmental factors such as heat and ultraviolet rays.

In addition, the power cable installed on the seabed is likely to be damaged by an anchor of a ship, and may be damaged by bending force due to currents or waves, frictional force with the seabed surface, etc. Therefore, Not shown) may be formed.

The enclosure may include an armor layer (not shown) and a storage layer (not shown). The armor layer may be composed of at least one layer made of steel, zinc-plated steel, copper, brass, bronze or the like, and having a circular cross-section, a flat cross-section, and the like. The armor layer (not shown) serves to enhance the mechanical properties and performance of the cable as well as to further protect the cable from external forces. Polypropylene yarn or the like is formed in one or more layers on the upper and / or lower portions of the armor layer to protect the cable, and the serving layer formed on the outermost layer is composed of two or more kinds of materials having different colors It is possible to secure the visibility of the cable installed in the sea floor.

2 schematically illustrates a cross-sectional structure of an intermediate junction box according to an embodiment of the present invention and a DC power cable connection system connecting a pair of DC power cables using the same. 1 is a partial cut-away view schematically showing a state in which DC power cables having a configuration as shown in Fig. 1 are connected to each other by an intermediate connection box 300. Fig.

An ultra high voltage direct current power cable connection system according to the present invention is characterized in that the ends of the pair of direct current power cables in which a conductor, an inner semiconductive layer, a cable insulation layer and an outer semiconductive layer are sequentially exposed are provided so as to face each other, And a joint connecting portion 310 connecting ends of the power cable 310 and the joint connecting portion 310. The joint connecting portion 310 and the joint sleeve 320 made of an elastic material that surrounds the outside of the pair of power cable ends and is shrinkable at room temperature, And an intermediate junction box for a DC power cable.

The outer surface of the joint sleeve 320 is electrically connected to the outer semiconductive layer 216 to the metal sheath 218 of the pair of power cables, (Not shown) formed of a metal casing surrounding the joint sleeve 320 and a waterproofing material (not shown) disposed in a space between the housing and the joint sleeve 320 As shown in FIG.

The conductor connection part 310 includes a conductor fixing part in which a pair of conductors 210 exposed at the end of the power cable are electrically connected and fixed to each other and a conductor fixing part which is exposed at the ends of the pair of power cables And a connection sleeve surrounding the end of layer 214. [ The conductor fixing portion may be formed by fitting a sleeve to the pair of conductors and pressing the outer circumferential surface of the sleeve, fixing a pair of conductors inserted in the sleeve with bolts passing through the sleeve, or welding the conductor ends to each other, The conductor 210 or the conductor fixing part may be electrically connected to the connection sleeve through a braided wire or the like.

The joint sleeve 320 includes a first electrode 321 electrically connected to the conductor connection part 310 of the pair of power cables and a pair of second electrodes 321 and 322 facing each other in the intermediate connection case 300, A second electrode 322 electrically connected to the outer semiconductive layer 216 to the metallic sheath 218 of the power cable of the power cable, And a connection box insulation portion 323 for preventing a current flowing through the conductor 210 of the system or the conductor connection portion 310 from leaking to the outside.

The joint sleeve 320 is made of a resilient material which can be shrunk at room temperature and is formed as a hollow sleeve having a through hole in its longitudinal direction and is electrically connected to a pair of cables Specifically, the insulating layer 214 of the pair of cables to the outer semiconductive layer 216 by elastic restoring force.

The first electrode 321 and the second electrode 322 serve to spread the electric field uniformly without being concentrated locally. Specifically, the first electrode 321 has a rounded shape at the left and right ends in the longitudinal direction of the power cable to the intermediate connection box, is formed of a semiconductive material, and is provided outside the conductor connection part 310 And is electrically connected to the conductor connection part 310 and the conductor 210 to function as a so-called high voltage electrode.

The second electrode 322 is formed of a semiconductive material, preferably the same material as that of the first electrode 321, and extends from the first electrode 321 to the left side in the longitudinal direction of the power cable, And are electrically connected to the outer semiconductive layer 216 of the power cable to function as a so-called shielding electrode.

In addition, the pair of second electrodes 322 increases in the direction toward the first electrode 321 in the vertical direction from the innermost surface of the joint sleeve 320 or the cable insulating layer 214, The increase rate of the vertical distance also increases in a direction toward the first electrode 321, and the surface facing the first electrode 321 is formed as a curved surface.

Accordingly, the first electrode 321 and the second electrode 322 are formed in rounded or curved shapes at their ends, and the first electrode 321 and the second electrode 322 are formed between the first electrode 321 and the second electrode 322 The equipotential lines are distributed, and the electric field distribution can be controlled.

The connection box insulation portion 323 is provided to surround the first electrode 321 and the second electrode 322 to prevent the current flowing in the cable connection system from leaking to the outside, thereby securing insulation performance.

The connection box insulating portion 323 may be made of a liquid silicone rubber (LSR), a fluorine rubber (FR), a styrene-butadiene rubber (SBR), a nitrile-butadiene rubber ), A chloroprene rubber (CR), or a combination thereof. Preferably, the composition has excellent long-term reliability such as a tear strength and a permanent change rate, And a liquid silicone rubber. 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.

The intermediate connection box and connection system for the ultra-high voltage direct current power cable according to the present invention may further include a charge blocking layer 325 on the inner surface of the through hole of the joint sleeve 320. That is, the intermediate connection box includes one or more surfaces selected from the group consisting of the innermost surface of the first electrode 321, the innermost surface of the second electrode 322 and the innermost surface of the connection- Lt; RTI ID = 0.0 > at least < / RTI > The intermediate connection system may further include an interface between the connection port insulation portion 323 and the insulation layer 214 of the cable, an interface between the first electrode 321 and the conductor connection portion 310, And an interface between the cable insulating layer 214 and the cable outer semiconductive layer 216. The charge blocking layer 325 may be formed of a metal such as copper,

The charge blocking layer 325 may be formed of an organic halogen-based oil or a grease including atoms having electronegativity higher than that of carbon. The atom having a high electronegativity covalently bonds with the carbon atom of the organic oil to trap the charge injected into the joint sleeve by the polarity property to prevent the charge from moving, It is possible to suppress accumulation of space charges in the memory cells.

Specifically, when the charge blocking layer is formed of a test piece having the charge blocking layer on one side of a connection box insulating portion test piece formed of a composition forming the connection port insulating portion, the charge blocking layer of the test piece and the corresponding test piece (FEF) of not more than 1.5, which is defined by the following formula (1), is applied to the electrode at room temperature under an electric field of 20 kV / mm for 1 hour at room temperature, It is possible to effectively suppress the electric field distortion and the dielectric breakdown caused by the electric field distortion.

[Equation 1]

FEF = maximum field value / applied field value

In the above equation (1)

The applied electric field value is 20 kV / mm as an electric field applied to the electrodes which are respectively in contact with the other surfaces of the charge blocking layer and the corresponding connection box insulating portion specimen,

The maximum electric field value means a maximum value of electric field values increased by electric field distortion due to the space charge accumulated in the specimen when an electric field of 20 kV / mm is applied to the specimen for 1 hour.

The charge blocking film 325 is formed such that when the specimen of the connection insulating portion 323 is impregnated into the oil composition (70 ° C) forming the charge blocking film 325, the weight change ratio of the specimen when the oil composition is saturated and contained in the specimen is 10 %, The rate of change in thickness is 5% or less, the tensile residual rate of the specimen is more than 80%, preferably 110% or more, and the elongation percentage is more than 95%, preferably 110% or more.

Here, the weight change rate, thickness change rate, tensile residual rate, elongation percentage refers to the ratio of the weight, thickness, tensile strength, elongation percentage, etc., increased from the weight, thickness, tensile strength, elongation percentage and the like of the specimen before impregnation.

Furthermore, the charge blocking film 325 is preferably made of a fluorine-based oil, for example, a polyfluoro polyether (PFPE), a polytetrafluoroethylene (PTFE ), Perfluoroalkoxy (PFA), fluoroethylene propylene (FEP), ethylene tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene (ECTFE), ethylene fluoroethylene propylene (EFEP), chlorotrifluoro (PFPE) oils such as ethylene (CTFE), polyvinylidene fluoride (PVdF), chloroprene tetrafluoride (CPT), polychlorotrifluoroethylene Component and a polytetrafluoroethylene (PTFE) solid component. Here, the weight ratio of the polyfluoropolyether (PFPE) oil component to the polytetrafluoroethylene (PTFE) solid component may be about 1: 9 to 9: 1.

The oil composition has a density (20 캜) of about 1.9 g / cm 3 or more and a kinematic viscosity (40 캜) of about 420 ㎟ / s (50 캜) for realizing the FEF, the weight change rate, the thickness change rate, the tensile residual rate, And the kinematic viscosity (100 DEG C) may be about 40 mm < 2 > / s or more.

Therefore, the intermediate junction box for cables according to one embodiment of the present invention exhibits an excellent effect of avoiding or minimizing shape deformation and mechanical property deterioration of the insulating material because the material forming the charge blocking film is not absorbed by the insulating material.

The charge blocking layer 325 may be in the form of a thin film. Oil, grease or the like may be applied to form a thin film-like charge blocking layer. Since the thin film-type charge blocking layer is formed of a thin film on the inner surface of the joint sleeve as compared with the conventional intermediate junction box in which a part of the connection box insulator is formed of the electric field control layer, There is an effect that can be.

The joint sleeve 320 of the intermediate connection box for cables according to the present invention may be manufactured by, for example, inserting a mold into a molding mold and injecting a semiconductive material into the mold to form the first electrode 321 and the second electrode 322 And then the composition for controlling electrical conductivity and the insulating composition are injected into the molding mold and then cured to form the connection box insulating portion 323. [ The intermediate connection box for cables can be manufactured by inserting the connection box insulation portion 323 after forming or applying a charge blocking layer on the inner wall surface of the joint sleeve 320 or the surface of the cable insulation layer 214 contacting the inner wall surface of the joint sleeve 320 have.

[Example]

1. Manufacturing Example

On each side of the insulating specimen as shown in Table 1 below, an insulating material specimen with or without a charge blocking layer was prepared.

Example 1 Comparative Example 1 Piece of insulation Liquid silicone rubber Charge blocking film Fluoric oil Silicone oil

2. Property evaluation

1) Space charge evaluation

The space charge behavior in the insulating material specimen was evaluated by applying an electric field of 20 kV / mm for one hour to the insulating material specimens of Examples and Comparative Examples in which the charge blocking film was formed on one side of the insulating material by using the PEA (Pulsed Electro-Acoustic) method. The evaluation result is as shown in Fig. Further, the FEF of the formula (1) indicating the degree of electric field distortion due to the accumulation of space charge was measured. The measurement results are shown in FIG. 4 and Table 2 below.

Example 1 Comparative Example 1 FEF 1.03 1.58

2) Evaluation of oil absorption characteristics

When impregnating an insulating material specimen not coated with a charge blocking film with fluorine-based oil, ester oil, polybutene oil and silicone oil at 70 ° C and oil saturated in the specimen, the weight change rate, the thickness change rate, the tensile residual rate, . Here, the tensile strength and elongation percentage for measuring the tensile residual rate and the elongation percentage were carried out at a tensile speed of 500 mm / min in accordance with the standard KS M 6518 four times or more, and the average value was calculated. The measurement results are shown in Table 3 below.

Weight change rate (%) Thickness change ratio (%) Tensile Residue (%) Renal survival rate (%) Fluoric oil 0 0 110 ~ 115 110 ~ 115 silicon
oil 50 cst 50 to 60
-
75 to 80
90 ~ 95 1,000 cst 20-25 10,000 cst 10 to 15 Ester oil 10 5 80 ~ 85 95-100 Polybutene 5 5 85 to 90 95-100

As shown in Table 2 and FIG. 3, the fluorine-based oil of Example 1 as the charge blocking film effectively blocks the accumulation of space charge (blue region) inside the insulating material by blocking the transfer of charge from the conductor to the insulating material, It was confirmed that the silicone oil of Example 1 had little charge blocking effect and space charge was accumulated (blue region) inside the insulating material.

Further, as shown in Table 3, the fluorine-based oil as the material of the charge blocking film is low in the property of being absorbed by the liquid silicone rubber as the insulating material, thereby increasing the weight and thickness of the insulating material and causing the tensile strength, It was confirmed that the mechanical properties of the polymer were not deteriorated. On the other hand, it was confirmed that silicon oil, ester oil and polybutene oil are highly absorbed in the insulating material, which greatly increases the weight and thickness of the insulating material, causing shape deformation and greatly degrading the mechanical properties such as tensile strength and elongation.

200: Power cable 300: Medium connection system for power cable

Claims (20)

Voltage DC power cable for interconnecting a pair of ultra-high voltage DC power cables in which a conductor, an inner semiconductive layer, a cable insulation layer and an outer semiconductive layer are sequentially exposed,
And a joint sleeve formed of a resilient material contractible at room temperature and having a through hole in the longitudinal direction, the joint sleeve having a connection box insulation portion for preventing current from leaking out of the intermediate connection box,
And a charge blocking layer formed on the inner surface of the through hole of the joint sleeve,
Wherein the charge blocking layer is formed of an organohalogen-based composition. The method according to claim 1,
Wherein the charge blocking layer
When the specimen having the charge blocking layer is formed on one side of the connection box insulating portion specimen formed by the composition of the connection box insulator portion, the electrode is brought into contact with the other side of the charge blocking layer of the specimen and the specimen corresponding thereto, Wherein the electrode has an electric field enhancement coefficient (FEF) of 1.5 or less as defined by Equation (1) below, when a voltage is applied to the electrode under an electric field of 20 kV / mm for 1 hour. .
[Equation 1]
FEF = maximum field value / applied field value
In the above equation (1)
The applied electric field value is 20 kV / mm as an electric field applied to the electrodes which are respectively in contact with the other surfaces of the charge blocking layer and the corresponding connection box insulating portion specimen,
The maximum electric field value is a maximum value of electric field values increased by electric field distortion due to the space charge accumulated in the specimen when an electric field of 20 kV / mm is applied to the specimen for 1 hour. The method according to claim 1,
When the oil composition forming the charge blocking film is heated to 70 캜 and the oil composition is impregnated with the specimen of the connecting portion, the weight change ratio of the specimen when the oil composition is saturated and contained in the specimen is less than 10% Wherein the thickness change ratio is 5% or less, the tensile residual rate of the specimen is more than 80%, and the elongation percentage is more than 95%. The method according to claim 2 or 3,
Wherein the charge blocking layer is an organohalogen-based oil or grease. 5. The method of claim 4,
Wherein the charge blocking layer comprises a fluorine-based oil. 6. The method of claim 5,
Characterized in that the charge blocking layer comprises a mixture of a polyfluoropolyether (PFPE) oil component and a polytetrafluoroethylene (PTFE) solid component. The method according to claim 6,
Characterized in that the charge blocking film has a density (20 ° C) of 1.9 g / cm 3 or more, a kinematic viscosity (40 ° C) of 420 mm 2 / s or more and a dynamic viscosity (100 ° C) of 40 mm 2 / Medium connection box. The method according to claim 2 or 3,
Wherein the joint sleeve is formed such that left and right ends of the intermediate connection case in the longitudinal direction are rounded and opposite to each other by a predetermined distance from the first electrode in the longitudinal direction of the intermediate connection case to left and right sides thereof, And a pair of second electrodes whose vertical distance from the innermost surface of the joint sleeve gradually increases toward the first electrode,
Characterized in that the charge blocking film is formed at least partially on at least one surface selected from the group consisting of the innermost surface of the first electrode, the innermost surface of the second electrode, and the innermost surface of the connection- Medium connection box for cables. The method according to claim 2 or 3,
The base resin included in the insulating composition forming the connection box insulating portion may be selected from the group consisting of a liquid silicone rubber (LSR), a fluorine rubber (FR), a styrene-butadiene rubber (SBR), a nitrile-butadiene rubber (NBR), and a chloroprene rubber ≪ RTI ID = 0.0 > 1, < / RTI > The method according to claim 2 or 3,
A connection housing shielding layer provided outside the joint sleeve for shielding an electric field leaking to the outside of the intermediate connection housing, a housing made of a metal casing surrounding the joint sleeve, and a waterproofing material disposed in a space between the housing and the joint sleeve And an intermediate connection box for an ultra-high voltage direct current power cable. Voltage direct current power cable including a conductor, an inner semiconductive layer, a cable insulation layer, and an outer semiconductive layer, and an intermediate connection box for an ultra high-voltage direct-current power cable connecting the pair of ultra- In a cable intermediate access system,
Wherein each end of the conductor, the inner semiconductive layer, the cable insulating layer and the outer semiconductive layer, which are sequentially exposed,
And a conductor connecting portion for electrically connecting and fixing the pair of conductors exposed at the end of the power cable,
And a joint sleeve formed of a resilient material contractible at room temperature and having a through hole in the longitudinal direction, the joint sleeve having a connection box insulation portion for preventing current from leaking out of the intermediate connection box,
And a charge blocking layer formed on the inner surface of the through hole of the joint sleeve,
Wherein the charge blocking layer is formed of an organohalogen-based composition. 12. The method of claim 11,
Wherein the charge blocking layer
When the specimen having the charge blocking layer is formed on one side of the connection box insulating portion specimen formed by the composition of the connection box insulator portion, the electrode is brought into contact with the other side of the charge blocking layer of the specimen and the specimen corresponding thereto, Wherein the voltage is applied to the electrode at an electric field of 20 kV / mm for 1 hour, the electric field enhancement factor (FEF) defined by Equation (1) is 1.5 or less.
[Equation 1]
FEF = maximum field value / applied field value
In the above equation (1)
The applied electric field value is 20 kV / mm as an electric field applied to the electrodes which are respectively in contact with the other surfaces of the charge blocking layer and the corresponding connection box insulating portion specimen,
The maximum electric field value is a maximum value of electric field values increased by electric field distortion due to the space charge accumulated in the specimen when an electric field of 20 kV / mm is applied to the specimen for 1 hour. 12. The method of claim 11,
When the oil composition forming the charge blocking film is heated to 70 캜 and the oil composition is impregnated with the specimen of the connecting portion, the weight change ratio of the specimen when the oil composition is saturated and contained in the specimen is less than 10% Wherein the thickness change ratio is 5% or less, the tensile residual rate of the specimen is more than 80%, and the elongation percentage is more than 95%. The method according to claim 12 or 13,
Wherein the charge blocking layer is an organohalogen-based oil or grease. 15. The method of claim 14,
Characterized in that the charge blocking layer comprises a fluorinated oil. ≪ RTI ID = 0.0 > 16. The method of claim 15,
Characterized in that the charge blocking layer comprises a mixture of a polyfluoropolyether (PFPE) oil component and a polytetrafluoroethylene (PTFE) solid component. 17. The method of claim 16,
Characterized in that the charge blocking film has a density (20 ° C) of 1.9 g / cm 3 or more, a kinematic viscosity (40 ° C) of 420 mm 2 / s or more and a dynamic viscosity (100 ° C) of 40 mm 2 / Connection system. The method according to claim 12 or 13,
Wherein the joint sleeve is formed such that left and right ends of the intermediate connection case in the longitudinal direction are rounded and opposite to each other by a predetermined distance from the first electrode in the longitudinal direction of the intermediate connection case to left and right sides thereof, And a pair of second electrodes whose vertical distance from the innermost surface of the joint sleeve gradually increases toward the first electrode,
An interface between the first electrode and the conductor connection portion, and an interface between the second electrode and the cable insulating layer to the cable outer semiconductive layer, Features an ultra-high voltage DC power cable connection system. The method according to claim 12 or 13,
The base resin included in the insulating composition forming the connection box insulating portion may be selected from the group consisting of a liquid silicone rubber (LSR), a fluorine rubber (FR), a styrene-butadiene rubber (SBR), a nitrile-butadiene rubber (NBR), and a chloroprene rubber ≪ RTI ID = 0.0 > 1, < / RTI > The method according to claim 12 or 13,
A connection housing shielding layer provided outside the joint sleeve for shielding an electric field leaking to the outside of the intermediate connection housing, a housing made of a metal casing surrounding the joint sleeve, and a waterproofing material disposed in a space between the housing and the joint sleeve , And at least one member selected from the group consisting of:

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