KR102378680B1 - 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 junction box for an ultra-high voltage DC power cable and an ultra-high voltage DC power cable connection system including the same. Specifically, the present invention suppresses the accumulation of space charges by injecting electric charges into the junction box insulation material applied to the intermediate junction box for ultra-high voltage DC power cables, thereby preventing electric field distortion due to the space charge and insulation breakdown of the intermediate junction box of the cable. It relates to an intermediate junction box for an ultra-high voltage DC power cable, which can be effectively prevented, and an ultra-high voltage DC power cable connection system including the same.

Description

Intermediate junction box for ultra-high voltage DC power cable and ultra-high voltage DC power cable connection system including the same

The present invention relates to an intermediate junction box for an ultra-high voltage DC power cable and an ultra-high voltage DC power cable connection system including the same. Specifically, the present invention suppresses the accumulation of space charges by injecting electric charges into the junction box insulation material applied to the intermediate junction box for ultra-high voltage DC power cables, thereby preventing electric field distortion due to the space charge and insulation breakdown of the intermediate junction box of the cable. It relates to an intermediate junction box for an ultra-high voltage DC power cable, which can be effectively prevented, and an ultra-high voltage DC power cable connection system including the same.

A power cable is a device that transmits power using an internal conductor, and can be divided into a power cable for direct current (DC) and a power cable for alternating current (AC). The ends are interconnected to enable long-distance transmission.

In the case of DC transmission using the ultra-high voltage DC power cable, there is an advantage in that the power loss is small and thus advantageous for long-distance transmission. However, in the conventional ultra-high voltage DC power transmission system including a power cable and a junction box, when a DC high voltage is applied to the power cable or junction box, electric charges are injected from the conductor into the insulating layer of the cable or junction box, or a cross-linking by-product of the cable insulating layer There is a problem in that a space charge is formed under the influence of In particular, the electric charge injected from the conductor into the insulating layer of the cable or junction box and accumulated in the insulating layer adjacent to the conductor to which a high voltage is applied causes a local resistivity change and electric field distortion, thereby lowering the dielectric strength of the ultra-high voltage DC cable system.

In order to solve the above-described problem of insulation performance deterioration due to the accumulation of space deterioration, European Patent Registration No. 1188209 discloses that a part of the cable insulation layer is formed as a field-controlling layer. However, the field-controlling layer is merely to prevent dielectric breakdown by controlling the electric field distribution when 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. does not offer a fundamental solution.

Therefore, it is possible to effectively prevent the electric field distortion caused by the space charge and the insulation breakdown of the intermediate junction box of the cable by suppressing the space charge accumulation by the injection of electric charge into the junction box insulation material applied to the intermediate junction box for the ultra-high voltage DC power cable. , an intermediate junction box for ultra-high voltage DC power cables and an ultra-high voltage DC power cable connection system including the same are urgently required.

The present invention provides an intermediate junction box for cables capable of effectively preventing the electric field distortion caused by the space charge and the resulting insulation breakdown of the intermediate junction box of the cable by suppressing the space charge accumulation due to the injection of electric charges into the junction box insulation material and including the same An object of the present invention is to provide a cable connection system that

In order to solve the above problems, the present invention,

An intermediate junction box for ultra-high voltage DC power cables for connecting a pair of ultra-high voltage DC power cables in which a conductor, an inner semiconducting layer, a cable insulation layer, and an outer semiconducting layer are sequentially exposed, to prevent leakage of current to the outside of the intermediate junction box and a joint sleeve formed of a hollow sleeve having a through-hole in the longitudinal direction and made of an elastic material that can be contracted at room temperature, comprising: a charge blocking layer formed on the inner surface of the through hole of the joint sleeve; Including, wherein the charge blocking layer provides an intermediate junction box for ultra-high voltage DC power cables, characterized in that formed of an organic halogen-based composition.

Here, the charge blocking layer is, when the specimen having the charge blocking layer is formed on one surface of the junction box insulating part specimen formed of the composition constituting the junction box insulating part, the charge blocking layer of the specimen and the corresponding specimen When the electrode is in contact with the other surface and a voltage is applied to the electrode with an electric field of 20 kV/mm at room temperature for 1 hour, the FEF defined by Equation 1 below is characterized in that it consists of a composition of 1.5 or less, Provides an intermediate junction box for ultra-high voltage DC power cables.

[Equation 1]

FEF = maximum field value / applied field value

In Equation 1 above,

The applied electric field value is 20 kV/mm as the electric field applied to the electrodes respectively contacting the other surface of the charge blocking layer and the corresponding junction box insulating part specimen,

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

In addition, when the oil composition forming the charge blocking layer is heated to 70° C. and then impregnated with the oil composition, the weight change rate of the specimen is 10 when the oil composition is saturated and included in the specimen. % and the thickness change rate is 5% or less, the tensile residual ratio of the specimen is more than 80% and the elongation residual ratio is more than 95%, it provides an intermediate junction box for ultra-high voltage DC power cables.

And, the charge blocking layer provides an intermediate junction box for ultra-high voltage DC power cables, characterized in that the organic halogen-based oil or grease.

Here, the charge blocking layer provides an intermediate junction box for cables, characterized in that it contains fluorine-based oil.

In addition, the charge blocking layer provides an intermediate junction box for ultra-high voltage DC power cables, characterized in that it contains a mixture of a polyfluoropolyether (PFPE) oil component and a polytetrafluoroethylene (PTFE) solid component.

And, the charge blocking layer 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 kinematic viscosity (100° C.) of 40 mm 2 /s or more, characterized in that the ultra-high pressure An intermediate junction box for DC power cables is provided.

On the other hand, the joint sleeve is formed such that the left and right ends of the first electrode are rounded in the longitudinal direction of the intermediate junction box and are spaced apart from each other by a predetermined distance to the left and right in the longitudinal direction of the intermediate junction box from the first electrode to face each other. and a pair of second electrodes whose vertical distance from the innermost surface of the joint sleeve gradually increases in the direction of the first electrode, the innermost surface of the first electrode and the innermost surface of the second electrode and the connection box It provides an intermediate junction box for ultra-high voltage DC power cables, characterized in that the charge blocking layer is formed at least partially on one or more surfaces selected from the group consisting of the innermost surface of the insulating part.

In addition, the base resin included in the insulating composition forming the junction box insulation part is liquid silicone rubber (LSR), fluororubber (FR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), and chloroprene rubber (CR). ) provides an intermediate junction box for ultra-high voltage DC power cables, characterized in that it contains at least one rubber selected from the group consisting of.

A junction box shielding layer provided outside the joint sleeve to shield an electric field leaking to the outside of the intermediate junction box, a housing made of a metal casing surrounding the joint sleeve, and disposed in a space between the housing and the joint sleeve It provides an intermediate junction box for ultra-high voltage DC power cables, characterized in that it contains at least one selected from the group consisting of waterproofing materials.

On the other hand, a pair of ultra-high voltage DC power cables having a conductor, an inner semiconducting layer, a cable insulation layer and an outer semiconducting layer and an ultra high voltage including an intermediate junction box for an ultra high voltage DC power cable connecting the pair of ultra high voltage DC power cables to each other In the DC power cable intermediate connection system, the ends of the conductor, the inner semiconducting layer, the cable insulating layer and the outer semiconducting layer are sequentially exposed to face each other, and a pair of conductors exposed at the end of the power cable are electrically connected It includes a conductor connection part connected to each other and fixed to each other, a junction box insulation part that prevents current from leaking to the outside of the intermediate junction box, is made of an elastic material that can be contracted at room temperature, and has a through hole in it in the longitudinal direction. Provided is an ultra-high voltage DC power cable connection system comprising a joint sleeve formed of a mold sleeve, and comprising a charge blocking layer formed on an inner surface of the through hole of the joint sleeve, wherein the charge blocking layer is formed of an organic halogen-based composition. .

Here, the charge blocking layer is, when the specimen having the charge blocking layer is formed on one surface of the junction box insulating part specimen formed of the composition constituting the junction box insulating part, the charge blocking layer of the specimen and the corresponding specimen When the electrode is in contact with the other surface and a voltage is applied to the electrode with an electric field of 20 kV/mm at room temperature for 1 hour, the FEF defined by Equation 1 below is characterized in that it consists of a composition of 1.5 or less, Provides an ultra-high voltage DC power cable connection system.

[Equation 1]

FEF = maximum field value / applied field value

In Equation 1 above,

The applied electric field value is 20 kV/mm as the electric field applied to the electrodes respectively contacting the other surface of the charge blocking layer and the corresponding junction box insulating part specimen,

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

In addition, after heating the oil composition forming the charge blocking layer to 70° C., when the specimen of the insulation part of the junction box is impregnated with the oil composition, the weight change rate of the specimen when the oil composition is saturated and included in the specimen is 10 % and the thickness change rate is 5% or less, the tensile residual ratio of the specimen is more than 80%, and the elongation residual ratio is more than 95%, it provides an ultra-high voltage DC power cable connection system.

And, the charge blocking layer provides an ultra-high voltage DC power cable connection system, characterized in that the organic halogen-based oil or grease.

Here, the charge blocking layer provides an ultra-high voltage DC power cable connection system, characterized in that it contains fluorine-based oil.

In addition, the charge blocking layer provides an ultra-high voltage DC power cable connection system, characterized in that it contains a mixture of a polyfluoropolyether (PFPE) oil component and a polytetrafluoroethylene (PTFE) solid component.

Furthermore, the charge blocking layer 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 kinematic viscosity (100° C.) of 40 mm 2 /s or more, characterized in that the ultra-high pressure A DC power cable connection system is provided.

On the other hand, the joint sleeve is formed such that the left and right ends of the first electrode are rounded in the longitudinal direction of the intermediate junction box and are spaced apart from each other by a predetermined distance to the left and right in the longitudinal direction of the intermediate junction box from the first electrode to face each other. and a pair of second electrodes whose vertical distance from the innermost surface of the joint sleeve gradually increases in the direction of the first electrode, the interface between the first electrode and the conductor connection part, the second electrode and the cable There is provided an ultra-high voltage DC power cable connection system, characterized in that a charge blocking layer at least partially covered is formed on one or more surfaces selected from the group consisting of an interface between an insulating layer and an interface between an insulating layer and an outer semiconducting layer of the cable.

In addition, the base resin included in the insulating composition forming the junction box insulation part is liquid silicone rubber (LSR), fluororubber (FR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), and chloroprene rubber (CR). ) It provides an ultra-high voltage DC power cable connection system, characterized in that it contains one or more rubbers selected from the group consisting of.

Further, a junction box shielding layer provided outside the joint sleeve to shield an electric field leaking to the outside of the intermediate junction box, a housing made of a metal casing surrounding the joint sleeve, and disposed in a space between the housing and the joint sleeve It provides an ultra-high voltage DC power cable connection system, characterized in that it includes at least one selected from the group consisting of waterproofing materials.

The intermediate junction box for cables according to the present invention forms a charge blocking layer on the surface into which the junction box insulation material is inserted, thereby suppressing the accumulation of space charges due to charge injection from the conductor to the junction box insulation material, thereby reducing the electric field distortion in the insulation material. This shows an excellent effect of suppressing dielectric breakdown caused by local electric field concentration.

1 schematically shows a longitudinal cross-sectional view of an ultra-high voltage DC power cable.
2 schematically shows a cross-sectional structure of a cable connection system according to an embodiment of the present invention.
3 shows the results of performing space charge behavior evaluation for Example 1 and Comparative Example 1 using the PEA method.
4 shows the results of field distortion evaluation for 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 and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed subject matter may be thorough and complete, and the spirit of the present invention may be sufficiently conveyed to those skilled in the art. Like reference numerals refer to like elements throughout.

1 schematically shows a longitudinal cross-sectional view of an ultra-high voltage DC power cable.

Referring to FIG. 1 , the power cable 200 includes a conductor 210 , an inner semiconducting layer 212 , an insulating layer 214 , and an outer semiconducting layer 216 in the cable length direction along the conductor 210 . It has a cable core that transmits only electric power and prevents current from leaking in the radial direction of the cable.

The conductor 210 serves as a path through which current flows to transmit power, and has excellent conductivity to minimize power loss, and a material having strength and flexibility suitable for cable manufacturing and use, for example, copper or aluminum, etc. can be composed of The conductor 210 may be a circular compressed conductor obtained by twisting a plurality of circular element wires to form a circular compression conductor, and a circular central element wire 210A and a flat element wire 210B twisted to surround the circular central element wire 210A. It may be a flat conductor having a flat element wire layer 210C formed therein and having an overall circular cross-section, and the flat conductor has a relatively high space factor compared to a circular compressed conductor, so that the outer diameter of the cable can be reduced.

However, since the conductor 210 is formed by twisting a plurality of strands, the surface thereof is not smooth, so that the electric field may be non-uniform, and corona discharge is likely to occur partially. In addition, when a void is formed between the surface of the conductor 210 and the insulating layer 214 to be described later, insulating performance may be deteriorated. In order to solve the above problems, an inner semiconducting layer 212 is formed outside the conductor 210 .

The inner semiconducting layer 212 has semiconductivity by adding conductive particles such as carbon black, carbon nanotubes, carbon nanoplates, and graphite to an insulating material, and is formed between the conductor 210 and an insulating layer 214 to be described later. It functions to stabilize the insulation performance by preventing a sudden electric field change from occurring. In addition, the electric field is made uniform by suppressing the non-uniform charge distribution on the conductor surface, and the formation of voids between the conductor 210 and the insulating layer 214 is prevented, thereby suppressing corona discharge, insulation breakdown, and the like.

An insulating layer 214 is provided on the outside of the inner semiconducting layer 212 to electrically insulate it from the outside so that the current flowing along the conductor 210 does not leak to the outside. In general, the insulating layer 320 has a high breakdown voltage, and insulating performance must be stably maintained for a long period of time. Furthermore, it must have low dielectric loss and resistance to heat such as heat resistance. Accordingly, the insulating layer 214 may be formed of a polyolefin resin such as polyethylene or polypropylene, and further preferably a polyethylene resin. Here, the polyethylene resin may be made of a crosslinking resin.

An 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, for example, carbon black, carbon nanotubes, carbon nanoplates, graphite, etc., to an insulating material like the inner semiconducting layer, and the insulating layer Insulation performance is stabilized by suppressing non-uniform charge distribution between the 214 and the metal sheath 218 to be described later. In addition, the outer semiconducting layer 216 smoothes the surface of the insulating layer 214 in the cable to relieve electric field concentration to prevent corona discharge, and also functions to physically protect the insulating layer 214 . .

The core part may additionally include a moisture absorption part (not shown) for preventing moisture from penetrating into the cable. The moisture absorbing part may be formed between the stranded wires and/or on the outside of the conductor 210, and has a high rate of absorbing moisture penetrating into the cable and has excellent ability to maintain an absorption state (super absorbent polymer). ; SAP) in the form of powder, tape, coating layer, or film to prevent moisture from penetrating in the longitudinal direction of the cable. In addition, the moisture absorbing part may have semi-conductivity in order to prevent an abrupt electric field change.

A protective sheath is provided on the outside of the core, and the power cable to be installed in an environment exposed to a lot of moisture, such as the seabed, additionally includes an external part (not shown). The protective sheath part and the external part protect the cable core part from various environmental factors, such as moisture penetration, mechanical trauma, 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 fault current, external force, 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 when an accident such as a ground fault or short circuit occurs, protects the cable from external impact, and prevents an electric field from being discharged to the outside of the cable. there is. In addition, in the case of a cable to be laid in an environment such as the seabed, the metal sheath is formed to seal the core portion, so that foreign substances such as moisture are intruded and insulation performance is prevented from being deteriorated. For example, by extruding molten metal to the outside of the core part to have a seamless and continuous outer surface, excellent water-repellent performance can be achieved. Lead or aluminum is used as the metal. In particular, in the case of a submarine cable, it is preferable to use lead with excellent corrosion resistance to seawater, and lead alloy with metal elements added to complement mechanical properties. ) is more preferably used.

In addition, the metal sheath 218 may be coated with an anti-corrosion compound, for example, blown asphalt, etc. on the surface of the metal sheath 218 to further improve corrosion resistance, water resistance, etc. of the cable and to improve adhesion with the inner sheath 220 . can In addition, a copper wire straight-through tape (not shown) or a moisture absorption layer (not shown) may be additionally provided between the metal sheath 218 and the core part. The copper wire straight-through tape is composed of a copper wire and a non-woven tape, etc., and functions to facilitate electrical contact between the outer semiconducting layer and the metal sheath layer, and the moisture absorption layer (not shown) absorbs moisture penetrating into the cable. It is composed of powder, tape, coating layer or film containing super absorbent polymer (SAP) with high speed and excellent ability to maintain absorption, and prevents moisture from penetrating in the longitudinal direction of the cable. do In addition, in order to prevent an abrupt electric field change in the water absorption layer, a copper wire may be included in the water absorption layer.

An inner sheath 220 made of a resin such as polyvinyl chloride (PVC), polyethylene, etc. is formed on the outside of the metal sheath 218 to improve corrosion resistance, water resistance, etc. of the cable, mechanical trauma and heat, ultraviolet rays It can perform the function of protecting the cable from other external environmental factors such as In particular, in the case of a power cable to be installed on the seabed, it is preferable to use a polyethylene resin having excellent water resistance, and it is preferable to use a polyvinyl chloride resin in an environment where flame retardancy is required.

The protective sheath portion further includes a bedding layer (not shown) made of a semi-conductive non-woven tape, etc. to buffer external force applied to the power cable, and an outer sheath (not shown) made of a resin such as polyvinyl chloride or polyethylene. It can further improve the corrosion resistance and water resistance of the cable, and additionally protect the cable from mechanical trauma and other external environmental factors such as heat and UV rays.

In addition, the power cable laid on the seabed is easily injured by the anchor of the ship, and may be damaged by the bending force caused by ocean currents or waves, frictional force with the sea floor, etc. In order to prevent this, an external part ( not shown) may be formed.

The exterior part may include an armor layer (not shown) and a serving layer (not shown). The armor layer is made of steel, galvanized steel, copper, brass, bronze, and the like and may be composed of at least one layer or more by transversely winding a wire having a cross-sectional shape such as a circular shape or a flat shape. The armor layer (not shown) not only serves to strengthen the mechanical properties and performance of the cable, but also additionally protects the cable from external forces. The serving layer composed of polypropylene yarn, etc. is formed in one or more layers above and/or below the armor layer to protect the cable, and the serving layer formed at the outermost layer is composed of two or more materials with different colors. Visibility of cables laid on the seabed can be secured.

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

The ultra-high voltage DC power cable connection system according to the present invention is provided such that the ends of the pair of DC power cables in which the conductors, the inner semiconducting layer, the cable insulating layer and the outer semiconducting layer are sequentially exposed are opposite to each other, and the pair of conductors Super high pressure having a conductive connection part 310 connecting the ends of the It may include an intermediate junction box for DC power cables.

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, so as to serve as an outer semiconducting layer of the power cable. A layer 324 , a housing (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 are added. can be included as

The conductor connection part 310 includes a conductor fixing part to which a pair of conductors 210 exposed at the end of the power cable are electrically connected and fixed to each other, and an insulation exposed at the ends of the conductor fixing part and the pair of power cables. It may include a connecting sleeve surrounding the end of the layer 214 . The conductor fixing part may be formed by inserting a sleeve into the pair of conductors and pressing the outer circumferential surface of the sleeve, fixing the pair of conductors inserted into the sleeve with a bolt penetrating 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 or the like.

The joint sleeve 320 is provided as a pair to face each other in the first electrode 321 electrically connected to the conductor connection part 310 of the pair of power cables, and the intermediate junction box 300, and the pair The second electrode 322 electrically connected to the outer semiconducting layer 216 to the metal sheath 218 of the power cable of and a junction box insulation 323 that prevents current flowing through the conductors 210 and 310 of the system from leaking to the outside.

In addition, the joint sleeve 320 is made of an elastic material that can be contracted at room temperature, is formed as a hollow sleeve having a through-hole in the longitudinal direction therein, and is a pair of cables electrically connected to each other by the conductor connection part 310 . , specifically, the respective insulating layers 214 to the outer semiconducting layers 216 of the pair of cables are in close contact with each other by an elastic restoring force.

The first electrode 321 and the second electrode 322 serve to spread the electric field evenly between them without being locally concentrated. Specifically, the first electrode 321 has a shape in which left and right ends are rounded in the longitudinal direction of the power cable to the intermediate junction box, is made of a semi-conductive material, and is provided on the outside of the conductor connection part 310 . It is electrically connected to the conductor connection part 310 and the conductor 210, and serves as a so-called high-voltage electrode.

The second electrode 322 is made of a semi-conductive material, preferably the same material as that of the first electrode 321, and from the first electrode 321 to the left side of the power cable to the intermediate junction box in the longitudinal direction and A pair is provided so as to face each other by being spaced a predetermined distance to the right, and is electrically connected to the outer semiconducting layer 216 of the power cable, thereby serving as a so-called shielding electrode (Deflector).

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

Accordingly, the first electrode 321 and the second electrode 322 have rounded or curved ends, and are formed between the first electrode 321 and the second electrode 322 according to the shape of each electrode. Equipotential lines are distributed at , and the electric field distribution can be controlled.

The junction box insulating part 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 ensuring insulation performance.

The junction box insulating part 323 is a liquid silicone rubber (LSR), fluororubber (FR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR) having excellent insulation performance to ensure the insulation performance of the intermediate junction box. ), chloroprene rubber (CR) or a combination thereof may be made of the first insulating composition, and preferably, the composition has excellent long-term reliability such as tear strength and permanent change rate, and productivity is improved through a fast production process It may include a liquid silicone rubber having In addition, the silicone rubber can be molded into various design products, so that moldability is improved, secondary vulcanization is unnecessary, and molding by double injection is possible.

The intermediate junction box and connection system for ultra-high voltage DC power cables 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 junction box has at least one surface 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 junction box insulating part 323 . It may include a charge blocking layer at least partially covered. In addition, the intermediate connection system includes an interface between the junction box insulating part 323 and the insulating layer 214 of the cable, an interface between the first electrode 321 and the conductor connection part 310 , and the second electrode 322 . ) and the cable insulating layer 214 to the cable outer semiconducting layer 216 may further include a charge blocking layer 325 at least partially coated on one or more surfaces selected from the group consisting of an interface, and the like.

The charge blocking layer 325 may be formed of an organic halogen-based oil or grease including an atom having a higher electronegativity than carbon. The inside of the joint sleeve 300 by trapping the electric charge injected into the joint sleeve by the polarity realized by the high electronegativity atom covalently bonding with the carbon atom of the organic oil and blocking the movement of the electric charge. It is possible to suppress the accumulation of space charges in the

Specifically, when the charge blocking layer is formed with the charge blocking layer on one surface of the junction box insulation specimen formed of the composition constituting the junction box insulation portion, the charge blocking layer of the specimen and the corresponding specimen When the electrode is in contact with the other surface and a voltage is applied to the electrode with an electric field of 20 kV/mm at room temperature for 1 hour, the composition having a field increase coefficient (FEF) defined by Equation 1 below is 1.5 or less. It is possible to effectively suppress electric field distortion and the resulting dielectric breakdown.

[Equation 1]

FEF = maximum field value / applied field value

In Equation 1 above,

The applied electric field value is 20 kV/mm as the electric field applied to the electrodes respectively contacting the other surface of the charge blocking layer and the corresponding junction box insulating part specimen,

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

In addition, the charge blocking layer 325 has a weight change rate of the specimen when the oil composition is saturated and included in the specimen when the specimen of the junction box insulating part 323 is impregnated with the oil composition (70° C.) forming it. It may be less than 10% and the thickness change rate is 5% or less, the tensile residual ratio of the specimen is more than 80%, preferably 110% or more, and the elongation residual ratio is more than 95%, preferably 110% or more.

Here, the weight change rate, thickness change rate, tensile residual rate, elongation residual rate, etc. mean the ratio of weight, thickness, tensile strength, elongation, etc. increased from the weight, thickness, tensile strength, elongation, etc. of the specimen before impregnation.

Further, from the viewpoint of suppressing oil absorption into the junction box insulating portion 323, the charge blocking layer 325 is preferably a fluorine-based oil, for example, polyfluoropolyether (PFPE), polytetrafluoroethylene ( PTFE), perfluoroalkoxy (PFA), fluoroethylene propylene (FEP), ethylene tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene (ECTFE), ethylene fluoroethylene propylene (EFEP), chlorotrifluoro may include roethylene (CTFE), polyvinylidene fluoride (PVdF), chloroprenetetrafluoride (CPT), polychlorotrifluoroethylene (PCTFE), etc., preferably polyfluoropolyether (PFPE) a mixture of an oil component and a polytetrafluoroethylene (PTFE) solid component. Here, the weight mixing ratio of the polyfluoropolyether (PFPE) oil component and the polytetrafluoroethylene (PTFE) solid component may be about 1:9 to 9:1.

The oil composition has a density (20° C.) of about 1.9 g/cm 3 or more, and a kinematic viscosity (40° C.) of about 420 mm 2 /s to implement the above-described FEF, weight change rate, thickness change rate, tensile residual ratio, elongation residual ratio, etc. or more, and the kinematic viscosity (100° C.) may be about 40 mm 2 /s or more.

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

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

In the intermediate junction box for cables according to the present invention, the joint sleeve 320 includes, for example, inserting a mold into a molding mold and injecting a semi-conductive material into the mold to connect the first electrode 321 and the second electrode 322 to each other. After molding, a composition for controlling electrical conductivity and an insulating composition are injected into the molding mold and then cured to form the junction box insulating part 323 . In addition, the intermediate junction box for the cable is manufactured by 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 in contact with it, and then inserting the junction box insulation part 323. can

[Example]

1. Preparation example

As shown in Table 1 below, insulating material specimens with or without a charge blocking layer formed on one surface of the insulating part specimen were prepared, respectively.

Example 1 Comparative Example 1 Insulation specimen liquid silicone rubber charge blocking layer Fluorine oil silicone oil

2. Physical property evaluation

1) Space charge evaluation

The space charge behavior in the insulating material specimen was evaluated while applying an electric field of 20 kV/mm for 1 hour using the pulsed electro-acoustic (PEA) method to the insulating material specimens of Examples and Comparative Examples in which the charge blocking film was formed on one surface of the insulating material. The evaluation results are as shown in FIG. 3 . In addition, the FEF of Equation 1 indicating the degree of electric field distortion due to space charge accumulation 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

After impregnating an insulating material specimen without a charge blocking layer in fluorine-based oil, ester oil, polybutene oil and silicone oil at 70° C., when the specimen is saturated with oil, the weight change rate, thickness change rate, tensile residual rate and elongation of the specimen The residual rate was measured. Here, the tensile strength and elongation for measuring the tensile residual ratio and the elongation residual ratio were performed four or more times at a tensile speed of 500 mm/min in accordance with the standard KS M 6518, and the average value was calculated. The measurement results are shown in Table 3 below.

Weight change rate (%) Thickness change rate (%) Tensile residual rate (%) Kidney Residual Rate (%) Fluorine oil 0 0 110~115 110~115 silicon
oil 50 cst 50 to 60
-
75-80
90-95 1,000 cst 20-25 10,000 cst 10-15 ester oil 10 5 80-85 95-100 polybutene oil 5 5 85-90 95-100

As shown in Table 2 and FIG. 3, the fluorine-based oil of Example 1 as a charge blocking layer blocks the transfer of electric charges from the conductor to the insulating material, effectively suppressing the accumulation of space charges (blue region) inside the insulating material, whereas It was confirmed that the silicone oil of Comparative Example 1 had little or no charge blocking effect, and space charges were accumulated inside the insulating material (blue region).

In addition, as shown in Table 3, as the material of the charge blocking layer, fluorine-based oil has low absorption properties by liquid silicone rubber, which is an insulating material, so it does not cause shape deformation such as increasing the weight or thickness of the insulating material, and the tensile strength and elongation of the insulating material. It was confirmed that it does not deteriorate mechanical properties, such as. On the other hand, silicone-based oil, ester oil, and polybutene oil have high absorption properties into the insulating material, which greatly increases the weight or thickness of the insulating material, causing shape deformation, and significantly lowering mechanical properties such as tensile strength and elongation.

200: power cable 300: intermediate connection system for power cable

Claims (20)

An intermediate junction box for ultra-high voltage DC power cables for connecting a pair of ultra-high voltage DC power cables in which a conductor, an inner semiconducting layer, a cable insulation layer, and an outer semiconducting layer are sequentially exposed,
A joint sleeve comprising a junction box insulating part that prevents current from leaking to the outside of the intermediate junction box, made of an elastic material that can be contracted at room temperature, and formed of a hollow sleeve having a through hole in the longitudinal direction therein;
and a charge blocking layer formed on the inner surface of the through hole of the joint sleeve;
The charge blocking layer,
When the specimen having the charge blocking layer is formed on one surface of the junction box insulation specimen formed of the composition constituting the junction box insulation portion, the electrode is brought into contact with the charge blocking layer of the specimen and the other surface of the corresponding specimen at room temperature When a voltage is applied to the electrode in an electric field of 20 kV/mm for 1 hour, the field rise factor (FEF) defined by Equation 1 below is made of an organic halogen-based composition of 1.5 or less, for an ultra-high voltage DC power cable Intermediate connection.
[Equation 1]
FEF = maximum field value / applied field value
In Equation 1 above,
The applied electric field value is 20 kV/mm as the electric field applied to the electrodes respectively contacting the other surface of the charge blocking layer and the corresponding junction box insulating part specimen,
The maximum electric field value is a maximum value among electric field values increased by electric field distortion due to space charges accumulated inside the specimen when an electric field of 20 kV/mm is applied to the specimen for 1 hour. delete An intermediate junction box for ultra-high voltage DC power cables for connecting a pair of ultra-high voltage DC power cables in which a conductor, an inner semiconducting layer, a cable insulation layer, and an outer semiconducting layer are sequentially exposed,
A joint sleeve comprising a junction box insulating part that prevents current from leaking to the outside of the intermediate junction box, made of an elastic material that can be contracted at room temperature, and formed of a hollow sleeve having a through hole in the longitudinal direction therein;
and a charge blocking layer formed on the inner surface of the through hole of the joint sleeve;
The charge blocking layer is formed of an organic halogen-based composition,
After heating the oil composition forming the charge blocking layer to 70° C., when the specimen of the junction box insulating part is impregnated with the oil composition, the weight change rate of the specimen when the oil composition is saturated and included in the specimen is less than 10% and the thickness change rate is 5% or less, the tensile residual ratio of the specimen is more than 80%, and the elongation residual ratio is more than 95%, the intermediate junction box for ultra-high voltage DC power cables. 4. The method of claim 1 or 3,
The charge blocking layer is an intermediate junction box for ultra-high voltage DC power cables, characterized in that organic halogen-based oil or grease. 5. The method of claim 4,
The charge blocking layer is characterized in that it contains fluorine-based oil, the intermediate junction box for cables. 6. The method of claim 5,
The charge blocking layer comprises a polyfluoropolyether (PFPE) oil component and a polytetrafluoroethylene (PTFE) solid component mixture. 7. The method of claim 6,
The charge blocking layer 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 kinematic viscosity (100° C.) of 40 mm 2 /s or more. Intermediate junction box for cables. 4. The method of claim 1 or 3,
The joint sleeve is formed such that the left and right ends of the first electrode are rounded in the longitudinal direction of the intermediate junction box and are spaced apart from each other by a predetermined distance to the left and right in the longitudinal direction of the intermediate junction box from the first electrode to face each other, A pair of second electrodes having a vertical distance from the innermost surface of the joint sleeve gradually increasing in the direction of the first electrode,
Ultra-high voltage direct current, characterized in that the charge blocking layer is formed at least partially on one or more surfaces 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 junction box insulating part. Intermediate junction box for power cables. 4. The method of claim 1 or 3,
The base resin included in the insulating composition forming the junction box insulation part is liquid silicone rubber (LSR), fluororubber (FR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR) and chloroprene rubber (CR). Intermediate junction box for ultra-high voltage DC power cables, characterized in that it contains at least one rubber selected from the group consisting of. 4. The method of claim 1 or 3,
A junction box shielding layer provided outside the joint sleeve to shield an electric field leaking to the outside of the intermediate junction box, 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. Intermediate junction box for ultra-high voltage DC power cables, characterized in that it contains at least one selected from the group consisting of. A pair of ultra-high voltage DC power cables having a conductor, an inner semiconducting layer, a cable insulation layer, and an outer semiconducting layer, and an ultra-high voltage DC power comprising an intermediate junction box for an ultra-high voltage DC power cable connecting the pair of ultra-high voltage DC power cables to each other In the cable intermediate connection system,
Each end of the conductor, the inner semiconducting layer, the cable insulating layer and the outer semiconducting layer is sequentially exposed so as to face each other,
and a conductor connecting portion for electrically connecting a pair of conductors exposed at the end of the power cable and fixing them to each other,
A joint sleeve comprising a junction box insulating part that prevents current from leaking to the outside of the intermediate junction box, made of an elastic material that can be contracted at room temperature, and formed of a hollow sleeve having a through hole in the longitudinal direction therein;
and a charge blocking layer formed on the inner surface of the through hole of the joint sleeve;
The charge blocking layer is, when the specimen having the charge blocking layer is formed on one surface of the junction box insulation specimen formed of the composition constituting the junction box insulation portion, the charge blocking layer of the specimen and the other surface of the corresponding specimen When an electrode is contacted and a voltage is applied to the electrode with an electric field of 20 kV/mm at room temperature for 1 hour, the field elevation coefficient (FEF) defined by Equation 1 below is 1.5 or less, characterized in that it consists of an organic halogen-based composition , extra-high voltage DC power cable connection system.
[Equation 1]
FEF = maximum field value / applied field value
In Equation 1 above,
The applied electric field value is 20 kV/mm as the electric field applied to the electrodes respectively contacting the other surface of the charge blocking layer and the corresponding junction box insulating part specimen,
The maximum electric field value is a maximum value among electric field values increased by electric field distortion due to space charges accumulated inside the specimen when an electric field of 20 kV/mm is applied to the specimen for 1 hour. delete A pair of ultra-high voltage DC power cables having a conductor, an inner semiconducting layer, a cable insulation layer, and an outer semiconducting layer, and an ultra-high voltage DC power comprising an intermediate junction box for an ultra-high voltage DC power cable connecting the pair of ultra-high voltage DC power cables to each other In the cable intermediate connection system,
Each end of the conductor, the inner semiconducting layer, the cable insulating layer and the outer semiconducting layer is sequentially exposed so as to face each other,
and a conductor connecting portion for electrically connecting a pair of conductors exposed at the end of the power cable and fixing them to each other,
A joint sleeve comprising a junction box insulating part that prevents current from leaking to the outside of the intermediate junction box, made of an elastic material that can be contracted at room temperature, and formed of a hollow sleeve having a through hole in the longitudinal direction therein;
and a charge blocking layer formed on the inner surface of the through hole of the joint sleeve;
The charge blocking layer is formed of an organic halogen-based composition,
When the oil composition forming the charge blocking layer is heated to 70° C. and then impregnated with the oil composition, the weight change rate of the specimen is less than 10% when the oil composition is saturated and included in the specimen. and the thickness change rate is 5% or less, the tensile residual ratio of the specimen is more than 80%, and the elongation residual ratio is more than 95%, the ultra-high voltage DC power cable connection system. 14. The method of claim 11 or 13,
The charge blocking layer is an ultra-high voltage DC power cable connection system, characterized in that the organic halogen-based oil or grease. 15. The method of claim 14,
The charge blocking layer is characterized in that it contains a fluorine-based oil, ultra-high voltage DC power cable connection system 16. The method of claim 15,
The charge blocking layer comprises a mixture of a polyfluoropolyether (PFPE) oil component and a polytetrafluoroethylene (PTFE) solid component, the ultra-high voltage DC power cable connection system. 17. The method of claim 16,
The charge blocking layer 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 kinematic viscosity (100° C.) of 40 mm 2 /s or more. cable connection system. 14. The method of claim 11 or 13,
The joint sleeve is formed such that the left and right ends of the first electrode are rounded in the longitudinal direction of the intermediate junction box and are spaced apart from each other by a predetermined distance to the left and right in the longitudinal direction of the intermediate junction box from the first electrode to face each other, A pair of second electrodes having a vertical distance from the innermost surface of the joint sleeve gradually increasing in the direction of the first electrode,
A charge blocking layer at least partially covered is formed on one or more surfaces selected from the group consisting of an interface between the first electrode and the conductor connecting portion and an interface between the second electrode and the cable insulating layer to the cable outer semiconducting layer. Characterized in, ultra-high voltage DC power cable connection system. 14. The method of claim 11 or 13,
The base resin included in the insulating composition forming the junction box insulation part is liquid silicone rubber (LSR), fluororubber (FR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR) and chloroprene rubber (CR). An ultra-high voltage DC power cable connection system comprising at least one rubber selected from the group consisting of. 14. The method of claim 11 or 13,
A junction box shielding layer provided outside the joint sleeve to shield an electric field leaking to the outside of the intermediate junction box, 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. Ultra-high voltage DC power cable connection system, characterized in that it comprises at least one selected from the group consisting of.

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