KR20160133908A - Power cable having a semiconductive layer - Google Patents

Abstract

The present invention relates to a power cable having a semi-conductive layer. Specifically, the present invention relates to a compact power cable including a semi-conductive layer having a sufficient semi-conductive property and, at the same time, having a reduced total outer diameter as well as a longer lifetime as compared with conventional cables.

Description

Technical Field The present invention relates to a power cable having a semiconductive layer,

The present invention relates to a power cable having a semiconductive layer. Specifically, the present invention relates to a compact power cable including a semiconductive layer having a sufficient semi-conductive property and at the same time having a reduced overall outer diameter as well as a longer lifetime as compared with conventional cables.

A general power cable can be formed in the order of an inner semiconductive layer, an insulating layer, an outer semiconductive layer, a sheath layer, etc. in the order of a conductor. Particularly, the inner semiconductive layer improves the degree of interfacial surface between the conductor and the insulating layer during cable production, suppresses formation of an air layer therebetween, forms a gradient of insulation resistance, and alleviates local field concentration Function.

In addition, the outer semiconductive layer performs a function of shielding the cable, and performs an equal electric field on the insulating layer. That is, the inner semiconductive layer and the outer semiconductive layer (hereinafter, referred to as a semiconductive layer) perform a very important function in terms of reinforcing the electrical and mechanical properties of the cable and hence the service life.

As disclosed in related U.S. Patent Application Publication No. 2010-0206607, the semiconductive layer generally includes a conductive material such as metal particles, carbon black, etc. to perform local field concentration mitigation, shielding function and the like in the cable.

In addition, since the conductive materials are generally nano-sized fine particles and tend to entanglement with each other in the base resin constituting the semiconductive layer, they are connected to each other in the base resin to form a conductive network In order to exhibit the semi-conductive characteristics of the semiconductive layer by forming a relatively large amount, for example, in an amount of about 40 to 60% by weight based on the total weight of the semiconductive layer.

However, the conductive material contained in the above-mentioned substantial amount may cause protrusions on the surface of the semiconductive layer to be produced, thereby lowering the surface smoothness of the semiconductive layer, thereby causing problems such as electric field concentration, dielectric strength, .

The lowering of the surface properties of the semiconductive layer is caused by the fact that the base resin constituting the semiconductive layer can contain the filler such as a conductive material added thereto in a uniformly dispersed form, that is, the poorer the filler loading property In the case of using a base resin which is more prominent and which has excellent filling material loading property, there may be a problem that the bond strength between the base resin and the base resin is deteriorated due to the heterogeneity with the base resin constituting the insulating layer in contact with the semiconductive layer.

In this regard, conventionally, a conductive polymer composite material including a carbon nano tube is known as a conductive material. Since the carbon nanotubes have a large aspect ratio, they have an advantage in that a conductive network can be formed in a relatively small amount relative to a conventional plate or flake shape such as carbon black.

However, since the carbon nanotubes have a large aspect ratio as described above, they are entangled with each other in the base resin constituting the semiconductive layer and are difficult to disperse. As a result of such micro dispersion, projections are formed on the surface of the semiconductive layer, It is necessary to increase the thickness of the insulating layer in consideration of the decrease in the dielectric strength of the insulating layer or to increase the thickness of the insulating layer by increasing the thickness of the insulating layer There is a problem that the life of the cable is shortened.

Accordingly, there is a demand for a compact power cable because it includes a semiconductive layer having a sufficient semi-conductive property and at the same time has a longer overall life as compared with a conventional cable and has a reduced overall outer diameter.

It is an object of the present invention to provide a power cable including a semiconductive layer exhibiting sufficient semi-conductive properties.

It is another object of the present invention to provide a power cable having a longer life than a conventional power cable.

It is another object of the present invention to provide a compact power cable having a reduced overall outer diameter as compared with a conventional power cable.

In order to solve the above problems,

One or more conductors; An inner semiconductive layer surrounding the conductor; An insulating layer surrounding the inner semiconductive layer; An outer semiconductive layer surrounding the insulating layer; And a sheath layer surrounding the outer semiconductive layer, wherein the inner semiconductive layer and the outer semiconductive layer are formed from a semiconductive composition comprising a base resin and a conductive filler, wherein the conductive filler has a length of 5 to 600 mu m Carbon nanotubes, wherein the inner semiconductive layer and the outer semiconductive layer crosslinks are each independently 55 to 85%.

Here, the length of the carbon nanotubes is more preferably 10 to 300 탆, and the cross-sections of the inner semiconductive layer and the outer semiconductive layer are independently 60 to 80%.

Also, the semiconductive composition preferably has a viscosity increased by addition of the conductive filler of 100 to 5,000 Pa · s, a volume resistivity of 1 to 1 × 10 ⁷ Ω · cm, a viscosity of the base resin, And a value measured at a speed of 1x10 < ^{2 >} s < ^-1 >.

Further, the content of the conductive filler is 0.5 to 20 wt% based on the total weight of the semiconductive composition.

On the other hand, the power cable is characterized in that the base resin of the semiconductive composition and the base resin constituting the insulating layer are the same resin.

Here, the power cable is characterized in that the base resin is low density polyethylene (LDPE).

On the other hand, the base resin of the semiconductive composition is ethylene ethyl acrylate (EEA), ethylene butyl acrylate (EBA), or a mixture thereof.

The conductive filler is bonded to the carbon nanotubes (CNTs) in a line contact manner, and the metal flake, the metal plate, the carbon nanoflake (CNF), and the carbon nanoplate and a carbon nano plate. The power cable may further include at least one conductive particle selected from the group consisting of carbon nano plates.

Further, the conductive particles and the carbon nanotubes (CNTs) may be coated on the surface of the conductive particles and the carbon nanotubes (CNTs) with one or _two or more kinds selected from the group consisting of hydroxyl group (-OH), amine group (-NH ₂ ), carboxyl group (-COOH) and epoxy group Wherein the functional group is a silane coupling agent of vinyltrimethoxysilane, methyltrimethoxysilane, aminopropyltrimethoxysilane, or derivatives thereof; Polyhydric alcohol binders of ethylene glycol, propylene glycol, glycerin, or derivatives thereof; And a polycarboxylic acid bonding agent of oxalic acid, propanedioic acid, butane diacid, or a derivative thereof. The present invention also provides a power cable.

Further, the present invention provides a power cable, characterized in that the conductive filler is introduced into the particle surface of the base resin.

The semi-conductive composition further comprises 0.5 to 2 parts by weight of a lubricant, 0.5 to 2 parts by weight of an antioxidant and 1 to 20 parts by weight of a surfactant based on 100 parts by weight of the base resin. Cable.

The power cable according to the present invention exhibits an excellent effect of realizing a sufficient semi-conductive property by adding carbon nanotubes (CNT) precisely adjusted as a conductive filler to the semiconductive layer included therein.

Further, the power cable according to the present invention can precisely control the length of the carbon nanotube (CNT) as a conductive filler and precisely control the degree of crosslinking of the semiconductive layer, thereby prolonging the lifetime compared with the conventional cable, And exhibits excellent effects that can be minimized.

1 is a cross-sectional view schematically showing a cross-sectional structure of a power cable according to the present invention.
2 is a longitudinal sectional view schematically showing a cross-sectional structure of a power cable according to the present invention.
3 is a graph showing the results of evaluation of dielectric strength against each of the example and the comparative example.

Hereinafter, preferred embodiments of the present invention will be described in detail. 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 this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Like reference numerals designate like elements throughout the specification.

1 and 2 show an embodiment of a power cable according to the present invention.

1 and 2, a power cable according to the present invention includes a conductor 1 made of a conductive material such as copper or aluminum, an insulating layer 3 made of an insulating polymer, (3), thereby suppressing partial discharge at the interface with the conductor (1), eliminating the air layer between the conductor (1) and the insulating layer (3) An outer semiconductive layer 4 serving as a shielding function of a cable and a function of applying an electric field uniform to the insulating layer 3, a sheath layer 5 for protecting the cable, And the like.

The insulating layer 3 may be manufactured from an insulating composition containing a polymer as a base resin. The polymer constituting the base resin is mostly an electrically insulating material, so there is no particular limitation. For electricity to pass, there must be free electrons, such as ions or metals, that can move positive electrons and electrons, because polymers are substances that are made up of covalent bonds between carbons and thus have little ability.

In general, the base resin forming the insulating layer 3 of the high-voltage or ultra-high-pressure cable is a polyolefin such as polyethylene (PE), polypropylene (PP), or ethylene propylene rubber (EPR) Can be used.

The polyethylene (PE) may comprise, for example, an ethylene homopolymer and / or a copolymer of ethylene and an alpha -olefin such as propylene, 1-butene, 1-pentene, 1-hexene or 1-octene. Here, the ethylene copolymer may be a random copolymer or a block copolymer. The polyethylene may also comprise ultra low density polyethylene, low density polyethylene, linear low density polyethylene, high density polyethylene, or mixtures thereof.

The polypropylene (PP) may include, for example, a propylene homopolymer and / or a copolymer of propylene and an? -Olefin such as ethylene, 1-butene, 1-pentene, 1-hexene or 1-octene. Here, the propylene copolymer may be a random copolymer or a block copolymer.

In the present invention, the semiconductive layer (2, 4) can be produced from a semiconductive composition comprising a base resin and a conductive filler.

The base resin may be appropriately selected from among conventionally used base resin for semiconductive layer, and examples thereof include polyolefins such as low density polyethylene, medium density polyethylene, high density polyethylene and polypropylene, and polyolefins such as ethylene vinyl acrylate, ethylene ethyl acrylate EEA) and ethylene butyl acrylate (EBA), polyacrylates, polyesters, polycarbonates, polyurethanes, polyimides, polystyrenes, and mixtures thereof, and fillers such as conductive fillers ethylene ethyl acrylate (EEA), ethylene butyl acrylate (EBA) and the like are preferable, but not limited thereto.

On the other hand, since the semiconductive composition according to the present invention uses carbon nanotubes (CNTs) as a conductive filler, even when a small amount of conductive filler is contained, sufficient conductivity network and anti-conduction characteristics can be realized, A low density polyethylene (LDPE) which is lower than the copolymer but superior in compatibility with the base resin for the insulating layer 3 and in bonding strength, preferably low density polyethylene (LDPE) can be used.

The conductive filler may include carbon nanotubes (CNTs) as described above. The carbon nanotubes (CNTs) are hexagons having six carbon atoms connected to each other to serve as tubes, and may have a single wall or a multiwall structure. The carbon nanotube (CNT) may have a diameter of 1 to 200 nm, preferably 5 to 100 nm, and the length may be 5 to 600 μm, preferably 10 to 300 μm. In this specification, the length of a carbon nanotube (CNT) means a distance between both ends of one unvulcanized carbon nanotube (CNT) particle.

If the length of the carbon nanotube (CNT) is too short to be less than 5 μm, a sufficient electric network can not be formed. Therefore, the dielectric strength of the insulating layer 3 may be lowered due to local field concentration, When the length of the carbon nanotubes (CNTs) is longer than 600 탆, projections are formed on the surface of the semiconductive layer (2, 4) formed by micro-dispersion due to entanglement in the base resin, 3) and the semiconductive layer (2, 4), and consequently, electric field concentration and deterioration of the dielectric strength may be caused.

Also, the content of the conductive filler may be 0.5 to 20 wt%, preferably 2 to 10 wt%, based on the total weight of the semiconductive composition. If the content of the conductive filler is less than 0.5% by weight, sufficient semiconducting properties can not be exhibited. If it exceeds 20% by weight, a high content of the conductive filler may increase the production cost, Can be degraded.

The conductive filler may include other conductive particles, preferably flake or plate conductive particles, such as metal flakes, which are bonded in a line contact with the carbon nanotubes (CNTs) flake, a metal plate, carbon nano flake (CNF), carbon nano plate (CNP), and the like.

Here, the weight ratio of the carbon nanotube (CNT) to the other conductive particles is, for example, 90:10 to 10:90, preferably 80:20 to 50:50, and more preferably 80:20 to 70:30 But is not limited thereto. As a result, the conductive filler maximizes the contact area between the carbon nanotube (CNT) and the other conductive particles to minimize the contact resistance at the contact surface, thereby further improving the semiconducting properties of the semiconductive layer (2, 4) Can be improved.

In addition, since the filler loading property of the semiconductive layer (2, 4) base resin is not greatly taken into account by the use of a small amount of the conductive filler, the filler can be easily loaded and used as a base resin for a conventional semiconductive layer (EEA), ethylene butyl acrylate (EBA), and the like, and the filling property is somewhat lower than these, but the compatibility with the base resin for the insulating layer 3, for example, polyethylene (PE) And a base resin having excellent bonding strength can be used.

The other conductive particles, such as metal flakes, metal plates, carbon nanoflake (CNF), and carbon nanoplate (CNP), each have a size of 0.5 to 25 탆, preferably 1 to 10 탆, more preferably 2 to 5 탆 And a thickness of 10 to 100 nm, preferably 10 to 50 nm, more preferably 20 to 30 nm, but is not limited thereto.

The carbon nanotube (CNT) and the other conductive particles may have a functional group such as a hydroxyl group (-OH), an amine group (-NH ₂ ), a carboxyl group (-COOH), and an epoxy group (-O-). These functional groups may be produced in the synthesis of carbon nanotubes (CNTs) or the like, and may be introduced by an additional process after synthesis. These functional groups include silanes such as vinyltrimethoxysilane, methyltrimethoxysilane, aminopropyltrimethoxysilane, or derivatives thereof; Polyhydric alcohols such as ethylene glycol, propylene glycol, glycerin, or derivatives thereof; And a polycarboxylic acid such as oxalic acid, propanedioic acid, butane diacid, or a derivative thereof, to thereby bond the carbon nanotube (CNT) with the other carbon filler .

Here, the content of the binder may be 1 to 20 parts by weight, preferably 5 to 15 parts by weight, based on 100 parts by weight of the conductive filler comprising the carbon nanotube (CNT) and the other conductive particles. When the content of the binder is less than 1 part by weight, the chemical bond between the carbon nanotube (CNT) and the other conductive particles may be insufficient. When the content of the binder is more than 20 parts by weight, the carbon nanotube (CNT) The electrical characteristics of the semiconductive layer (2, 4) may be lowered due to excessive chemical bonding between the carbon nanotubes (CNTs).

The method for producing the semiconductive composition comprising the base resin and the conductive filler to form the semiconductive layer (2, 4) is not particularly limited. Preferably, the conductive filler is introduced into the surface of the base resin particles by using a device such as a Hybridizer (manufacturer: Nara Machinery), Nobilta (manufacturer: Hosokawa Micron) or Q-mix (Mitsui Mining) And in this case, the dispersibility of the conductive filler in the base resin can be further improved.

The semiconductive composition comprises a crosslinking agent for crosslinking the base resin, a surfactant for improving the dispersibility of the conductive filler in the base resin, a lubricant for improving processability for forming a semiconductive layer, a cable And other additives such as antioxidants for prolonging life.

The type of the crosslinking agent is not particularly limited and may be appropriately selected according to the crosslinking method to be used. For example, in the case of chemical crosslinking, dicumyl peroxide (DCP), di (t-butylperoxy) Of organic peroxides may be used, and silane crosslinking agents may be used in the case of water spraying.

Here, the degree of crosslinking of the semiconductive layer (2, 4) formed by the semiconductive composition may be 55 to 85%, preferably 60 to 80%. When the degree of crosslinking of the semiconductive layer (2, 4) is too low to be less than 55%, due to insufficient cross-linking, the power cable is continuously used at 90 ° C, which is its operating condition, When the degree of crosslinking of the semiconductive layer (2, 4) is excessively high, for example, more than 85%, the surface of the semiconductive layer (2, 4) is scorched by the scorch during the extrusion of the semiconductive layer So that the dielectric strength of the insulating layer 3 due to the electric field concentration is lowered and consequently the insulating layer 3 must be formed thickly in view of the dielectric strength, The life span can be shortened.

Further, by controlling the degree of crosslinking of the semiconductive layer (2, 4) precisely, a crosslinking agent is added in an appropriate amount to inhibit the formation of crosslinked byproducts such as acetophenone, alphamethylstyrene, It is possible to further suppress the degradation of the electrical characteristics of the semiconductor device.

The kind of the surfactant is not particularly limited and examples thereof include sodium dodecyl sulfate (SDS), glycolic acid ethoxylate 4-nonylphenyl ether (GAENPE), n- A cationic surfactant such as dodecyltrimethylammonium bromide (DTAB), a nonionic surfactant such as Triton X-45, Triton X-114, and Triton X-100 , Or a combination thereof. The content of the surfactant may be 1 to 10 parts by weight, preferably 2 to 5 parts by weight based on 100 parts by weight of the conductive filler.

The kind of the lubricant is not particularly limited, and for example, fatty acid such as stearyl stearate, erucamide, stearic acid, or the like can be used. Here, the content of the lubricant is based on 100 parts by weight of the base resin 0.1 to 2 parts by weight.

The antioxidant is not particularly limited and includes, for example, amine-based antioxidants; Thioester-based antioxidants such as dialkyl esters, distearyl thiodipropionate, and dilauryl thiodipropionate; Tetrakis (2,4-di-t-butylphenyl) 4,4'-biphenylene diphosphite, 2,2'-thiodiethylbis- [3- (3,5- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis- [3- Methyl-6-t-butylphenol), 2,2'-thiobis (6-t-butyl-4-methylphenol), triethylene glycol-bis- [3- (3- 4-hydroxy-5-methylphenyl) propionate]), and mixtures thereof, wherein the antioxidant is a mixture of 100 parts by weight of the base resin May be 0.1 to 2 parts by weight.

The semiconductive composition may have a different viscosity depending on the type and content of the base resin and the conductive filler contained therein, and the dispersibility of the conductive filler in the base resin. In the present invention, it is preferable that the semiconductive composition has an increased viscosity of 100 to 5,000 Pa · s, preferably 2,000 to 3,000 Pa · s, by the addition of the conductive filler. Here, the viscosity is a value measured at a fixing shear rate of ¹ x 10 ² s ^-1 at the melting temperature of the base resin. Also, the volume resistivity of the semiconductive composition may be 1 to 1x10 < ⁷ >

Wherein the semiconductive composition has an increased viscosity of 100 to 5,000 Pa · s and a volume resistivity of 1 to 1 × 10 ⁷ Ω · cm by the addition of the conductive filler, The amount of the conductive filler is small enough not to lower the surface smoothness of the semiconductive layer formed from the semiconductive composition and the conductive filler is uniformly dispersed in the base resin to form a conductive network to exhibit sufficient semiconducting properties.

On the other hand, the sheath layer 5 is preferably made of the same resin as the base resin of the semiconductive layer 4 for compatibility with the external semiconductive layer 4 and bonding strength.

The outer diameter, the thickness, etc. of the conductor 1, the inner semiconductive layer 2, the insulating layer 3, the outer semiconductive layer 4, the sheath layer 5, etc. constituting the power cable according to the present invention May be suitably selected by a person skilled in the art depending on the use of the cable, the operating voltage, and the like.

[Example]

1. Manufacturing Example

8% by weight of a conductive filler containing multi-walled carbon nanotubes having various lengths as shown in the following Table 1, ethylene dichloride and ethylene ethyl acrylate as a base resin, and various concentrations of dicumyl peroxide as a cross- (A wire diameter of 0.8 mm, seven stranded strands of seven strands, 3.5 SQ, a half-thickness layer thickness of 1 mm, and an insulating layer thickness of 0.2 mm) having the inner semiconductive layer and the outer semiconductive layer.

CNT length (탆) Cross-linkability (%) Example 1 10 60 Example 2 10 75 Example 3 10 85 Example 4 300 60 Example 5 300 75 Example 6 300 85 Example 7 600 60 Example 8 600 75 Example 9 600 85 Comparative Example 1 10 40 Comparative Example 2 10 90 Comparative Example 3 300 40 Comparative Example 4 300 90 Comparative Example 5 600 40 Comparative Example 6 600 90 Comparative Example 7 One 40 Comparative Example 8 One 60 Comparative Example 9 One 75 Comparative Example 10 One 85 Comparative Example 11 One 90 Comparative Example 12 900 40 Comparative Example 13 900 60 Comparative Example 14 900 75 Comparative Example 15 900 85 Comparative Example 16 900 90

3. Property evaluation

1) Cable life evaluation

The half-thickness specimen was continuously kept at any three temperatures higher than the cable operating temperature of 90 ° C, and the change in elongation was continuously monitored to determine the elongation percentage to be 50% of the initial value. The elongation percentage (K = Ae- ^{Ea / RT,} A: frequency constant, Ea: activation energy, R: gas constant, T: constant) with an Arrhenius plot The activation energy Ea and the frequency constant A of the semi-conductor layer were measured at 90 ° C (T) by calculating the reaction constant (k) from the activation energy (Ea) (T) until the battery voltage (P / Po * 100) became 50% was evaluated and evaluated as cable life.

[Mathematical Expression]

In (P / Po) = -k (T) t

In the above equation,

P: Modified elongation of the semiconductive layer

Po: initial elongation of the semiconductive layer

k: reaction constant

T: temperature

t: time

3) Evaluation of dielectric strength

IEC 60243-1, the voltage applied to each of the cable specimens of the examples and comparative examples was raised to 500 V / s to measure the voltage at which the insulation breakdown occurred.

The results of the physical property evaluation are shown in Table 2 and FIG. 3 below.

90 ℃ Standard life (years) Dielectric strength (kV / mm) Example 1 26 74.98 Example 2 37 73.94 Example 3 43 72.49 Example 4 28 74.12 Example 5 39 70.28 Example 6 45 71.2 Example 7 31 72.22 Example 8 41 67.34 Example 9 46 69.32 Comparative Example 1 13 75.32 Comparative Example 2 44 45.67 Comparative Example 3 12 73.28 Comparative Example 4 44 47.91 Comparative Example 5 14 73.21 Comparative Example 6 47 39.46 Comparative Example 7 16 33.29 Comparative Example 8 27 32.57 Comparative Example 9 40 39.43 Comparative Example 10 43 32.32 Comparative Example 11 45 27.58 Comparative Example 12 13 49.23 Comparative Example 13 30 52.93 Comparative Example 14 39 48.23 Comparative Example 15 44 48.23 Comparative Example 16 43 30.91

As shown in Table 2 above, the cables of Examples 1 to 9 according to the present invention are characterized in that the length of the carbon nanotube (CNT) and the degree of crosslinking of the semiconductive layer are precisely controlled as conductive fillers added to the semiconductive layer, It was confirmed that the semi-conductive property was sufficiently realized and both the dielectric strength and the life were improved.

On the other hand, in the power cables of Comparative Examples 1, 3, 5, 7 and 12, the lifetime was shortened because the degree of crosslinking of the semiconductive layer was too low, while the power cables of Comparative Examples 2, 4, 6, 11, It is confirmed that protrusions are formed on the surface of the semiconductive layer due to too high a scorch during extrusion, thereby forming a void space between the insulating layer and the semiconductive layer to cause problems such as field concentration and deterioration of dielectric strength.

In addition, the power cables of Comparative Examples 7 to 11 showed that the length of the carbon nanotubes added to the semiconductive layer was too short to realize a sufficient semiconducting property, and as a result, the dielectric strength was lowered due to local electric field concentration. The length of carbon nanotubes added to the semiconductive layer of 12 to 16 power cables is too long to form projections on the surface of the semi-conductive layer due to micro dispersion in the base resin, thereby forming a void space between the insulating layer and the semiconductive layer, Concentration, and lowering of dielectric strength.

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

1: conductor 2: inner semiconductive layer
3: insulating layer 4: outer semiconductive layer
5: Sheath layer

Claims (11)

One or more conductors;
An inner semiconductive layer surrounding the conductor;
An insulating layer surrounding the inner semiconductive layer;
An outer semiconductive layer surrounding the insulating layer; And
And a sheath layer surrounding the outer semiconductive layer,
Wherein the inner semiconductive layer and the outer semiconductive layer are formed by a semiconductive composition comprising a base resin and a conductive filler,
Wherein the conductive filler comprises carbon nanotubes having a length of 5 to 600 mu m,
Wherein the inner semiconductive layer and the outer semiconductive layer crosslinking degree are each independently 55 to 85%. The method according to claim 1,
The length of the carbon nanotubes is 10 to 300 탆,
Wherein the inner semiconductive layer and the outer semiconductive layer crosslinking degree are each independently 60 to 80%. 3. The method according to claim 1 or 2,
Wherein the semiconductive composition has a viscosity increased by addition of the conductive filler of 100 to 5,000 Pa · s, a volume resistivity of 1 to 1 × 10 ⁷ Ω · cm, a viscosity of the base resin and a fixed shear rate of 1 × 10 ^{2 < / RTI >} s < ^{-1 &} gt ;. The method of claim 3,
Wherein the content of the conductive filler is 0.5 to 20 wt% based on the total weight of the semiconductive composition. 3. The method according to claim 1 or 2,
Wherein the base resin of the semiconductive composition and the base resin constituting the insulating layer are the same resin. 6. The method of claim 5,
Wherein the base resin is low density polyethylene (LDPE). 3. The method according to claim 1 or 2,
Wherein the base resin of the semiconductive composition is ethylene ethyl acrylate (EEA), ethylene butyl acrylate (EBA), or a mixture thereof. 3. The method according to claim 1 or 2,
The conductive filler is bonded to the carbon nanotubes (CNTs) in a line contact, and the conductive fillers are mixed with metal flakes, metal plates, carbon nano flakes (CNFs) nano plate). < RTI ID = 0.0 > 11. < / RTI > 9. The method of claim 8,
The conductive particles and the carbon nanotubes (CNTs) may have at least one or more selected from the group consisting of a hydroxyl group (-OH), an amine group (-NH ₂ ), a carboxyl group (-COOH) and an epoxy group Having a functional group,
Wherein the functional group is a silane coupling agent of vinyltrimethoxysilane, methyltrimethoxysilane, aminopropyltrimethoxysilane, or derivatives thereof; Polyhydric alcohol binders of ethylene glycol, propylene glycol, glycerin, or derivatives thereof; And a polycarboxylic acid coupling agent of oxalic acid, propane diacid, butane diacid, or a derivative thereof. 3. The method according to claim 1 or 2,
Characterized in that the conductive filler is introduced into the particle surface of the base resin. 3. The method according to claim 1 or 2,
Wherein the semiconductive composition further comprises 0.5 to 2 parts by weight of a lubricant, 0.5 to 2 parts by weight of an antioxidant, and 1 to 20 parts by weight of a surfactant based on 100 parts by weight of the base resin.

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