KR20180131053A - Terminal joint for high voltage DC power cable - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an end connection case 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 DC power cable, which is capable of suppressing the accumulation of space charge by injecting a charge into a junction box insulating material applied to a termination junction for an ultra-high voltage direct current power cable, thereby distorting the electric field caused by the space charge, Voltage DC power cable connection system and an ultra high-voltage DC power cable connection system including the same.

Description

{Terminal joint for high voltage DC power cable}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a terminal box for an ultrahigh voltage direct current power cable. More particularly, the present invention relates to a method of manufacturing a high-voltage DC power cable, which is capable of suppressing the accumulation of space charge by injecting a charge into a junction box insulating material applied to a termination junction for an ultra-high voltage direct current power cable, thereby distorting the electric field caused by the space charge, And more particularly to an end connection box for an ultra high-voltage DC power cable.

An ultra high-voltage DC power cable is an apparatus for transmitting power using an internal conductor and can be divided into a direct current (DC) power cable and an alternating current (AC) power cable, A termination connection box is provided. The termination junction box can be classified into a gas termination junction box, a gas termination junction box and an oil termination junction box depending on a state in which the lead conductor of the cable is connected, The cable has an aptitude for insertion of a predetermined length, and the inside of the aisle is filled with insulating oil, and the power cable is connected to the working power transmission line by the termination termination box.

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 ultra high voltage direct current transmission system including a power cable and a junction box, if a direct current high voltage is applied to the power cable or the connection box, charges are injected from the conductor into the cable insulation layer and the connection insulation material, There is a problem that a space charge is formed in the insulating layer due to the influence. Particularly, the electric charge accumulated in the cable insulation layer or the connection insulation layer adjacent to the conductor injected from the conductor and to which a 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 junction-protecting insulating layer is formed as a field-controlling layer in order to solve the above-mentioned problem of deterioration of insulation performance due to space reduction accumulation. However, the field-controlling layer is merely for preventing the dielectric breakdown by controlling the electric field distribution when a space charge of a certain level or more is accumulated in the insulating layer for connection, and space charge is injected into the insulator It does not provide a fundamental solution to prevent it.

Therefore, it is possible to suppress the accumulation of space charge by injection of charges into the connection box insulating material applied to the terminal connection box for the ultra-high voltage DC power cable, thereby effectively preventing the electric field distortion caused by the space charge and the end connection of the cable, , And a terminal connection box for an ultra high-voltage DC power cable is desperately required.

The present invention relates to a cable termination box capable of effectively preventing accumulation of space charges due to injection of charges into a connection box insulating material, thereby effectively preventing electric field distortion caused by the space charges, do.

In order to solve the above problems,

A terminal for an ultra-high-voltage DC power cable including an insulator into which one end of an ultra-high voltage DC power cable, in which a conductor, an inner semiconductive layer, a cable insulation layer, an outer semiconductive layer and a metal sheath layer are sequentially exposed, Wherein the electric field control unit further comprises a main body having a hollow portion made of an insulating material and capable of inserting a cable, an electrode wrapped by the main body and electrically connected to the outer semiconductive layer, And a charge blocking layer formed at least partially on the inner wall surface, wherein the charge blocking layer is formed of an organohalogen-based composition.

Here, the charge blocking layer may be formed such that when a test piece having the charge blocking layer is formed on one surface of an insulating test piece formed of a composition constituting the main body, an electrode is brought into contact with the other surface of the charge blocking layer of the test piece and the corresponding test piece , And applying a voltage to the electrode at room temperature for 1 hour at an electric field of 20 kV / mm, the electric field coefficient of elevation (FEF) defined by the following Equation 1 is 1.5 or less. And provides a termination box.

[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 forming the charge blocking film is heated to 70 캜 and the oil composition is impregnated with the insulating specimen of the main body, the weight change rate of the specimen when the oil composition is saturated and contained in the specimen is less than 10% And a percentage 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 a termination junction for an ultra high voltage direct current 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 a termination box for power cables.

Furthermore, one end of the electrode may include a portion contacting the cable insulation layer and a portion spaced apart from the insulation layer, and a portion spaced apart from the insulation layer may have a shape such that the vertical distance from the insulation layer gradually increases And an end connection box for an ultrahigh voltage direct current power cable is provided.

The base resin contained in the insulating composition forming the body may be selected from the group consisting of liquid silicone rubber (LSR), fluorine rubber (FR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), and chloroprene rubber And at least one kind of rubber selected from the group consisting of a rubber and a rubber.

On the other hand, the insulating oil includes an ester oil, and provides an end connection box for an ultra-high voltage direct current power cable.

The ester oil has a number average molecular weight (Mn) of about 400 to 1200, a weight average molecular weight (Mw) of about 420 to 1200, a kinematic viscosity (40 캜) of 20 mm 2 / And a dielectric breakdown voltage of greater than 75 kV when the moisture content is less than 400 ppm or the moisture content exceeds 600 ppm.

The termination junction box for cables according to the present invention suppresses the accumulation of space charge by injecting charge from the conductor to the insulating material to be connected by forming the insulating layer of the cable to be connected and the charge blocking layer on the surface in contact with the external semiconductive layer and the electric field control section Thereby exhibiting an excellent effect of suppressing the electric field distortion in the insulating material and the dielectric breakdown due to the 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 section of an end connection system to which a termination box for a cable according to an embodiment of the present invention is applied.
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 100 includes a conductor 11, an inner semiconductive layer 12, an insulating layer 14, and an outer semiconductive layer 16, and extends along the conductor 11 in the cable longitudinal direction And a cable core portion (10) for transmitting electric power and preventing current from leaking in the cable radial direction.

The conductor 11 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 11 may be a circular compressive conductor formed by twisting a plurality of circular strands and circularly compressing them. The conductor 11 may be a circular central strand 11A and a rectangular parallelepiped strand 11B stranded to surround the circular central strand 11A The rectangular conductor may have a relatively large dot ratio as compared with the circular compressed conductor, and thus the cable outer diameter can be reduced.

However, since the conductor 11 is formed by stranding a plurality of elemental wires, the surface of the conductor 11 may not be smooth, so that the electric field may be uneven and corona discharge is likely to occur partially. Further, when a gap is formed between the surface of the conductor 11 and the insulating layer 14 described later, the insulating performance may be deteriorated. In order to solve the above-described problems, an inner semiconductive layer 12 is formed outside the conductor 11.

Conductive particles such as carbon black, carbon nanotube, carbon nanoplate, graphite and the like are added to the insulating semiconductive layer 12 to have semiconducting properties, and between the conductor 11 and the insulating layer 14 Thereby preventing the occurrence of a sudden electric field change and stabilizing the insulation performance. In addition, by suppressing uneven distribution of electric charge on the conductor surface, the electric field is made uniform, and the formation of gaps between the conductor 11 and the insulating layer 14 is prevented to suppress corona discharge, dielectric breakdown, and the like.

An insulating layer 14 is provided on the outer side of the inner semiconductive layer 12 to electrically insulate the conductor 11 from the outside so that a current flowing along the conductor 11 does not leak to the outside. Generally, the insulating layer 14 should have a high breakdown voltage and be able to maintain its insulating performance for a long period of time. Furthermore, it should have low dielectric loss and resistance to heat such as heat resistance. Therefore, polyolefin resin such as polyethylene and polypropylene can be used for the insulating layer 14, and further, a polyethylene resin is preferable. Here, the polyethylene resin may be made of a crosslinked resin.

The outer semiconductive layer 16 is provided outside the insulating layer 14. The outer semiconductive layer 16 is formed of a semiconductive material such as an inner semiconductive layer 12 by adding conductive particles such as carbon black, carbon nanotube, carbon nanoplate, graphite or the like to an insulating material, The non-uniform charge distribution between the insulating layer 14 and the metal sheath 22 described later is suppressed to stabilize the insulating performance. In addition, the outer semiconductive layer 16 smoothes the surface of the insulating layer 14 in the cable to alleviate the concentration of the electric field, thereby preventing corona discharge, and physically protecting the insulating layer 14 .

The core portion 10 may further include a moisture absorbing layer 21 for preventing water from penetrating into the cable. The water absorbing layer 21 can be formed between the stranded strands and / or outside the conductor 11. The water absorbing layer 21 can be formed of a super absorbent resin (for example, tape, coating layer or film including super absorbent polymer (SAP) to prevent moisture from penetrating in the longitudinal direction of the cable. In addition, the moisture absorbing layer 21 may have a semiconductive property in order to prevent a sudden change in the electric field.

A protective sheath portion 20 is provided outside the core portion 10 and a power cable installed in an environment exposed to moisture such as a seabed is further provided with an external portion 30. The protective sheath 20 and the sheath 30 protect the cable core 10 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 portion 20 includes a metal sheath layer 22 and an inner sheath 24 to protect the cable from an accident current, an external force or other external environmental factors.

The metal sheath layer 22 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. The metal sheath layer 22 protects the cable from external impacts and prevents the electric field from being discharged to the outside of the cable have. In addition, in the case of a cable attached to an environment such as a seabed, the metal sheath layer 21 is formed to seal the core portion 10 to prevent foreign matter such as moisture from entering the insulation layer. For example, molten metal may be extruded outside the core portion 10 to have a continuous outer surface with 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 layer 22 is coated with a corrosion inhibiting compound such as a blown asphalt or the like on the surface to further improve the corrosion resistance and water repellency of the cable and to improve the adhesion with the inner sheath 24 . In addition, a copper line tape (not shown) or a water absorbing layer 21 may be additionally provided between the metal sheath layer 22 and the core portion 10. The copper wire drawing tape is composed of a copper wire and a nonwoven tape to facilitate electrical contact between the outer semiconductive layer 16 and the metal sheath layer 22. The moisture absorbing layer 21 penetrates the cable Tape, a coating layer or a film including a super absorbent polymer (SAP) excellent in the ability to absorb a moisture and having an excellent ability to maintain an absorption state, It is important to prevent the In order to prevent a sudden change in the electric field in the water absorbing layer 21, a copper wire may be included in the water absorbing layer 21.

An inner sheath 24 made of a resin such as polyvinyl chloride (PVC), polyethylene or the like is formed on the outer side of the metal sheath layer 22 to improve the corrosion resistance and water repellency of the cable, It is possible to perform a function of protecting the cable from other external environmental factors such as ultraviolet rays. 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 20 further includes a metal reinforcing layer 26 made of a semiconductive nonwoven tape or the like to buffer an external force applied to the power cable and an outer sheath 28 made of a resin such as polyvinyl chloride or polyethylene It is possible to further improve the corrosion resistance and water repellency of the power cable, and further protect 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 may be easily damaged by an anchor or the like of a ship, and may be damaged by bending force due to currents or waves, friction with the sea floor, etc. Therefore, The external portion 30 may be formed.

The enclosure may include an armor layer 34 and a throat layer 38. The armor layer 34 may be formed of at least one layer made of steel, zinc-plated steel, copper, brass, bronze or the like, and having a circular cross section, a square cross section, and the like. The armor layer 34 not only functions to enhance the mechanical properties and performance of the cable, but also protects 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 34 to protect the cable, and the serving layer 38 formed at the outermost portion is formed in a color Can be made of two or more different materials to ensure the visibility of the cable installed at the seabed.

2 schematically shows a cross section of an end connection system to which a termination box for a cable according to an embodiment of the present invention is applied.

As shown in FIG. 2, the termination receptacle 200 has an eyelet 210. The air pipe 210 has a predetermined space therein, and the power cable 100 is inserted into the electric cable 100 with a predetermined length as will be described later. The cap 210 insulates and supports the power cable. Thus, the eye 210 has a plurality of wrinkles or protrusions 212 along its surface to provide sufficient electrical insulation strength. It is possible to increase the insulation distance by the wrinkles or protrusions and to prevent the dielectric strength from deteriorating. The cap 210 may be fabricated using rigid magnetic or polymeric resins to maintain an appropriate level of strength while having dielectric strength.

The power cable 100 penetrates through the auxiliary pipe 210 and a conductor lead bar 41 electrically connected to the conductor 10 of the power cable 100 is protruded by a predetermined length through the upper end of the auxiliary pipe 210. A corona shield 42 may be provided on the upper end of the aerator 41. The corona shield 42 is formed with rounded corners to prevent corona discharge and the conductor lead rod 41 penetrates the corona shield 42 and protrudes outside the aerator 210.

In the power cable 100, the components surrounding the conductor 11 are peeled off from the inside of the aerator 210 and only the conductor 11 is exposed at the end of the aerator 210 to be connected to the conductor draw- The conductor draw-out bar 41 protrudes through the corona shield 42 and is connected to a machining line (not shown). That is, when the power cable 100 is inserted into the aisle 210 of the termination box 200, the power cable 100 is in a state in which the cable sheath 30 is removed, The semiconductive layer 12, the insulating layer 14, the outer semiconductive layer 16, and the metal sheath 22 are sequentially exposed. In this case, the unremoved outer semiconductive layer 16 is inserted into the eyelet 210 by a predetermined length. That is, the power cable 100 is inserted into the eyelet 210 by exposing the insulating layer 14, and the outer semiconductive layer 16 is inserted into the predetermined length eyelet 210.

Meanwhile, the insulating pipe 220 may be filled in the inner pipe 210. The insulating oil 220 flows between the power cable 100 and the inner wall of the pipe 210 inside the pipe 210 to electrically isolate the oil.

The stator oil may have a number average molecular weight (Mn) of about 400 to 1200, a weight average molecular weight (Mw) of about 420 to 1200, a kinematic viscosity (40 DEG C) Is at least 20 mm 2 / s and the kinematic viscosity (100 ° C) may be at least 4. Particularly, the moisture content of the ester oil is preferably 400 ppm or less, but the dielectric breakdown voltage can be maintained to exceed 75 kV even when the moisture content exceeds 600 ppm.

When a high voltage is applied in a state where the power cable 100 in which the part of the outer semiconductive layer 16 is removed so as to expose the insulation layer 14 is inserted into the termination connection compartment, An electric field may be concentrated at the end portion, which may cause dielectric breakdown. Therefore, as shown in FIG. 2, the electric field controller 230 for reducing the concentration of the electric field of the cable 100 may be provided in the inner pipe 210.

The electric field controller 230 includes a main body 231 having a hollow portion into which the power cable can be inserted and formed of an insulating material so as to surround an electrode 232 to be described later, an electrode 231 electrically connected to the outer semiconductive layer 16, (232) and a charge blocking layer (233) formed at least partially on the inner wall surface of the hollow portion.

The main body 231 prevents the current flowing in the cable connection system from leaking to the outside, thereby ensuring insulation performance. The main body 231 is made of a liquid silicone rubber (LSR), a fluororubber (FR), a styrene-butadiene rubber (SBR), a nitrile-butadiene rubber (NBR), a chloroprene rubber (CR), or a combination thereof. Preferably, the composition has a long-term reliability such as a tear strength and a permanent change ratio, and has a merit that productivity is improved by a quick production process. . ≪ / RTI > 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.

In addition, the electrode 232 functions to spread the electric field inside the body 231 and the dielectric oil 220 evenly without being concentrated locally. Specifically, the electrode 232 is made of a semiconductive material and is electrically connected to the outer semiconductive layer 16 of the cable to serve as a so-called shielding electrode.

One end of the electrode 232 may include a portion contacting the cable insulation layer 14 and a portion spaced apart from the insulation layer 14, The end of the electrode 232 may be formed in a rounded shape or a curved shape and an equipotential line may be formed around the electrode in accordance with the shape of the electrode. So that the electric field distribution can be controlled.

The charge blocking layer 233 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-based oil to trap charges injected from the conductor 11 and the insulating layer 14 due to the polarity property to be realized, Accumulation of space charge in the main body 231 and the insulating oil 220 can be suppressed.

Specifically, if the charge blocking layer 233 is formed with a charge blocking layer on one surface of an insulating test piece formed of the insulating composition forming the main body 231, the charge blocking layer 233 (FEF) of 1.5 or less, which is defined by the following Equation (1), when a voltage is applied to the electrode at room temperature for 1 hour under an electric field of 20 kV / mm. It is possible to effectively suppress the distortion of the electric field due to the accumulation and the dielectric breakdown caused thereby.

[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 an electrode which is in contact with the other surface of the charge blocking layer and the corresponding insulating 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 layer 233 may have a weight change rate of less than 10% when the oil composition (70 ° C) forming the charge blocking layer 233 is impregnated with the specimen of the main body 231, , The thickness change rate 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.

Further, the charge blocking layer 233 is preferably made of a fluorine-based oil, for example, a polyfluoro polyether (PFPE), a polytetrafluoroethylene (PTFE), a polytetrafluoroethylene (PFA), fluoroethylene propylene (FEP), ethylene tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene (ECTFE), ethylene fluoroethylene propylene (EFEP), chlorotrifluoroethylene (PFPE) oil component, preferably polyfluoroether polyol (CTFE), polyvinylidene fluoride (PVdF), chloroprene tetrafluoride (CPT), polychlorotrifluoroethylene And a mixture of polytetrafluoroethylene (PTFE) solid components. 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, in the cable termination box according to the embodiment of the present invention, the material forming the charge blocking layer 233 is not absorbed by the main body 231, thereby avoiding the shape deformation and the mechanical property deterioration of the main body 231 Or minimizing the effect of the present invention. The charge blocking layer 233 may be in the form of a thin film. Oil, grease or the like may be applied to form a charge blocking layer 233 in the form of a thin film.

[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 layer 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 1 hour to the insulating material specimens of the examples and comparative examples having a charge blocking layer on one side of the insulating material by using a 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 sample to which the charge blocking layer is not applied in a fluorine-based oil, an ester oil, a polybutene oil and a silicone oil at 70 ° C and the oil is saturated in the specimen, the weight change rate, the thickness change rate, the tensile residual rate, The residual rate was measured. 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 layer effectively inhibited the accumulation of space charge (blue region) in the insulating material by blocking the movement of charge from the conductor to the insulating material, It was confirmed that the silicone oil of Comparative 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 layer is low in the property of being absorbed by the liquid silicone rubber as the insulating material, so that the tensile strength and elongation It was confirmed that the mechanical properties such as mechanical strength and the like 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.

100: High-voltage power cable 200: Cable termination box

Claims (11)

A terminal for an ultra-high-voltage DC power cable including an insulator into which one end of an ultra-high voltage DC power cable, in which a conductor, an inner semiconductive layer, a cable insulation layer, an outer semiconductive layer and a metal sheath layer are sequentially exposed, By connecting,
Further comprising an electric field control section,
Wherein the electric field control unit comprises a main body having a hollow portion into which a cable can be inserted, an electrode wrapped by the main body and electrically connected to the outer semiconductive layer, and a charge blocking layer formed at least partially on the inner wall surface of the hollow portion, ≪ / RTI &
Wherein the charge blocking layer is formed of an organohalogen-based composition. The method according to claim 1,
Wherein the charge blocking layer
In the case where the test piece having the charge blocking layer is formed on one surface of the insulating test piece formed of the composition constituting the main body, the electrode is brought into contact with the other surface of the charge blocking layer of the test piece and the corresponding test piece, / mm when the voltage is applied for 1 hour, the electric field enhancement factor (FEF) defined by the following formula (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. 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 insulating specimen of the main body, when the oil composition is saturated and contained in the specimen, the weight change rate of the specimen is less than 10% Wherein the rate of change 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 organic halogen-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,
Wherein 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 / Terminated connection. The method according to claim 2 or 3,
One end of the electrode may include a portion contacting the cable insulation layer and a portion spaced apart from the insulation layer, and a portion of the electrode spaced apart from the insulation layer may have a shape such that the vertical distance from the insulation layer gradually increases Wherein the terminal is connected to a terminal of the high voltage direct current power cable. The method according to claim 2 or 3,
The base resin included in the insulating composition forming the main body may be a group consisting of a liquid silicone rubber (LSR), a fluororubber (FR), a styrene-butadiene rubber (SBR), a nitrile-butadiene rubber (NBR), and a chloroprene rubber Wherein the rubber comprises at least one rubber selected from the group consisting of polypropylene and polypropylene. The method according to claim 2 or 3,
Characterized in that the insulating oil comprises an ester oil. 11. The method of claim 10,
The ester oil has a number average molecular weight (Mn) of about 400 to 1200, a weight average molecular weight (Mw) of about 420 to 1200, a kinematic viscosity (40 캜) of 20 mm 2 / s or more, a kinematic viscosity (100 캜) , Wherein the dielectric breakdown voltage is greater than 75 kV when the moisture content is less than 400 ppm or the moisture content exceeds 600 ppm.

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