KR20110138958A - Insulation material composition for dc power cable and the dc power cable using the same - Google Patents

Abstract

PURPOSE: An insulation composition for a direct current cable, and the cable using thereof are provided to offer the excellent direct current dielectric breakdown strength and the impulse strength to the cable. CONSTITUTION: An insulation composition for a direct current cable contains the following: 100 parts of low density polyethylene base resin by weight; 0.05-0.5 parts of nanocarbon particles by weight; 1-4 parts of dicumyl peroxide cross-linking agent; and 0.1-1 parts of antioxidant by weight. The nanocarbon particles contain a graphite layer with less than 6 layers, and have the average diameter less than 500nm.

Description

Insulation Material Composition For DC Power Cable And The DC Power Cable Using The Same}

The present invention relates to an insulating material composition for a direct current power cable and a cable manufactured using the same.

Currently, domestic power cables are used as shown in FIGS. 1A and 1B, with an inner semiconducting layer 2, an insulating layer 3, an outer semiconducting layer 4, and lead around a conductor 1. It consists of a sheath layer 5 and a polyethylene (PE) sheath layer 6.

Conventionally, low density polyethylene (LDPE) or the like has been widely used as the insulating layer 3 constituting the power cable. However, when a power cable including an insulator made of low density polyethylene or the like is used as a high voltage transmission line, some problems occur. The biggest problem among them is that, when DC high voltage is applied to the cable, space charge is easily formed due to the effect of charge injection and crosslinking by-products from the electrodes on the insulator. If such space charge is accumulated in the insulator by the DC voltage applied to the power cable, the electric field strength in the vicinity of the conductor of the power cable increases, which causes a problem that the breakdown voltage of the cable is lowered.

In order to solve the above problems, a method of manufacturing an insulator using a metal oxide such as magnesium oxide and titanium dioxide as a space charge reducing agent has been proposed. Since the metal oxide is usually hydrophilic, it is difficult to be dispersed in hydrophobic low density polyethylene.

Therefore, there is a need to develop a method capable of improving the dispersibility of space charge reducing agents in basic resins such as low density polyethylene and at the same time suppressing space charges that may occur in power cables including insulators manufactured using the same. .

The technical problem of the present invention is to develop a space charge reducing agent having excellent dispersibility with respect to the base resin, and by using the base resin and the space charge reducing agent, an insulation material composition for DC power cables having excellent space charge reducing effect is provided. To provide.

In order to achieve such an object, the insulation material composition for direct current power cables of this invention contains 0.05-0.5 weight part of nano carbon particles with respect to 100 weight part of low density polyethylene base resins.

The power cable for direct current provided with the insulator manufactured using the insulating material composition of this invention has the outstanding direct current breakdown strength and the impulse strength.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings attached to the present specification illustrate exemplary embodiments of the present invention, and together with the detailed description of the present invention, the present invention is intended to help understand the technical idea of the present invention. No.
1A shows a longitudinal cross-sectional view of a DC power cable.
1b shows a cross-sectional view of a direct current power cable.
Figure 2 shows the structure of the nano-carbon particles composed of one layer of graphite layer as an embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

The insulating material composition of the present invention is characterized by containing 0.05 to 0.5 parts by weight of nano carbon particles, based on 100 parts by weight of the low density polyethylene base resin.

In addition, according to the present invention, the insulating material composition may further include 1 to 4 parts by weight of dicumyl peroxide crosslinking agent and 0.1 to 1 part by weight of antioxidant.

Nano carbon particles of the present invention means a nano-sized carbon particles having a thickness of less than 10 nm and an average diameter of less than 500 nm, including six layers of graphite (graphite), reducing the space charge in the present invention Function as zero. Compared to the dielectric metal oxides such as magnesium oxide and titanium dioxide used in the prior art as space charge reducing agents, the metallic particles of the present invention have a larger potential well. As a result, an excellent space charge reduction effect is exhibited even when using a much smaller amount of nano carbon particles than in the case of using a conventional dielectric metal oxide. That is, when an electric field is applied, a larger potential well is formed at the boundary between the low density polyethylene base resin and the nano carbon particles of the present invention, thereby exhibiting the effect of suppressing charge transfer and accumulation. In particular, when the nano carbon particles of the present invention have a thickness of 2 nm or less and an average diameter of 100 nm or less, it is possible to more effectively suppress the generation of space charges.

In addition, since general graphite has an average diameter of 1 mm to 2.5 cm and has a very hard and fragile structure, impurity strength and degradation of extrudability are increased when included in an insulating material composition. In addition, the carbon nanotubes may be partially energized due to a very high aspect ratio, have a high possibility of dielectric breakdown, and may be difficult to be dispersed in a low density polyethylene base resin because of its needle shape. However, since the nano carbon particles of the present invention have a thickness of 10 nm or less and an average diameter of 500 nm or less, they exhibit more excellent DC dielectric breakdown strength and impulse strength than general graphite or carbon nanotubes.

In addition, since the nano-carbon particles of the present invention are 10 times lower in price than conventional metal oxides such as magnesium oxide and titanium dioxide, cost reduction effects can be expected.

In addition, generally, the more the inorganic particles are added to the insulating material composition, the more the amount of continuous extrusion tends to decrease. In the present invention, the content of the nano carbon particles may be reduced, and as a result, the extrudability may be improved. In addition, since the nano-carbon particles of the present invention have a tensile strength of 10 to 20 GPa, physical property improvement effects such as increasing the thermal stability by increasing the glass transition temperature (Tg) of the insulating material composition to be produced can be expected. have.

In addition, the nano-carbon particles of the present invention preferably has a density of 1.8 to 2.2 g / cm ³ , this high density improves the mechanical strength and thermal properties of the insulating material. In addition, the nano-carbon particles of the present invention preferably has an electrical conductivity of 1 × 10 ^-5 to 8 × 10 ^-5 Ω · cm, and has a relatively large potential well due to this high electrical conductivity. Excellent space charge reduction effect is exhibited.

Regarding the content of the nano-carbon particles of the present invention, it is preferable to include 0.05 to 0.5 parts by weight based on 100 parts by weight of the low density polyethylene base resin. When the amount is less than 0.05 parts by weight, the effect of reducing the space charge is small, and when it is included by the amount exceeding 0.5 parts by weight, the effect of reducing the space charge is excellent, but the DC insulation breakdown strength is reduced due to the decrease in the resistivity. Therefore, the nano carbon particles of the present invention is preferably included in the above content.

As an example of the nano carbon particles of the present invention, a case composed of one layer of graphite layers is shown in FIG. 2. When the nano carbon particles of the present invention are composed of two or more ply graphite layers, the spacing between the laminated graphite layers is about 0.34 nm.

As the antioxidant of the present invention, any one or more selected from the group consisting of amine, phenol, sulfur and phosphorus antioxidants may be used. As the sulfur-based antioxidant, distearyl disulfide, dilauryl 3,3'-thiodipropionate, lauryl stearyl 3,3'-thio dipropionate, distearyl 3,3'-thiodiprop Cypionate and the like can be used. As the phosphorus antioxidant, tris (2,4-di-t-butylphenyl) phosphite, di- (2,4-di-t-butylphenyl) pentaerythritol diphosphite, tetrakis (2,4-di -t-butylphenyl) 4,4'-diphenylene diphosphite and the like can be used.

The insulator manufactured using the insulating material composition of the power cable according to the present invention can be used in the manufacture of a power cable for direct current.

[Example]

The present invention will be described in more detail with reference to the following Examples. The average person skilled in the art to which the present invention pertains may change the present invention in various other forms in addition to the embodiments described in the following examples, and the following examples merely illustrate the present invention, and the scope of the technical spirit of the present invention is given below. It is not to be construed as limiting the scope of the examples.

In order to examine the performance of the insulation material composition for DC power cables of the present invention, the insulation material compositions of Examples and Comparative Examples were prepared with the compositions shown in Table 1 below.

ingredient
Example Comparative example One 2 One 2 3 4 Low density polyethylene
Base resin content 100 parts by weight

space
Majesty
Reducer
ingredient Nano carbon particles Nano carbon particles Nano carbon particles


No additives Oxidation
magnesium Titanium dioxide content 0.1
Parts by weight 0.5
Parts by weight One
Parts by weight 0.1
Parts by weight 0.1
Parts by weight D50 (nm) 100 100 100 70 100 D99 (nm) 200 200 200 110 150 water(%) 99.95 99.95 99.95 99.95 99.95 Thickness (nm) 10 10 10 - - Crosslinker content 2 parts by weight Antioxidant content 0.5 parts by weight

[Description of Components Used in Table]

* Magnesium Oxide: Crushed cube-type magnesium oxide surface-modified with vinylsilane, in order to improve dispersibility, D99 (where D99 represents the maximum size of this particle) is D50 (where D50 is the average of these particles). Kneaded to not more than three times the size).

* Titanium dioxide: Titanium dioxide surface-modified with vinyl silane, pulverized to improve dispersibility, D99 (where D99 represents the maximum size of this particle) is D50 (where D50 is the average size of this particle). Kneaded less than three times).

* Crosslinking agent: Dicumyl peroxide

* Antioxidant: Tetrakis (2,4-di-t-butylphenyl) 4,4'-biphenylene diphosphite

Measurement and evaluation of physical properties

A master batch compound was prepared using the insulating material composition according to Examples 1 to 2 and Comparative Examples 1 to 4, and a twin screw extruder having a screw diameter of 25 mm (L / D = 60). Was extruded using. The insulator thus prepared was hot pressed to prepare 0.1 mm thick specimens for measuring DC dielectric breakdown strength and 1 mm thick sheet specimens for measuring impulse strength, and to determine DC dielectric breakdown strength (ASTM D149) and impulse strength. The test results are summarized in Table 2 below. Brief experimental conditions are as follows.

㉠ DC dielectric breakdown strength

The DC breaking strength (kV) is measured at 90 ° C.

㉡ impulse strength

Impulse strength is measured by connecting electrodes to a sheet-shaped specimen of 1 mm thickness and increasing the pressure by 5 kPa at 50 kPa until it is broken.

ingredient
Example Comparative example One 2 One 2 3 4 DC dielectric breakdown strength
(kV / mm) 120 115 50 55 80 65 Impulse Strength (kV / mm) 115 105 80 120 110 100

As a result of measuring the physical properties as summarized in Table 2, the specimens of Examples 1 to 2 of the present invention are Comparative Example 1 (using an excess of nano carbon particles), Comparative Example 2 (without using a space charge reducing agent), and Comparative Examples. Compared with the specimens of 3 (using magnesium oxide) and Comparative Example 4 (using titanium dioxide), the DC dielectric breakdown strength was somewhat higher. That is, it can be seen that the specimens of Examples 1 to 2 of the present invention using an appropriate amount of nano carbon particles exhibit excellent electrical insulation properties.

On the other hand, the impulse strength generally tends to be excellent as the content of the inorganic particles used as the space charge reducing agent decreases. Thus, the impulse strength of Example 1 using 0.1 parts by weight of nano carbon particles was better than Example 2 using 0.5 parts by weight of nano carbon particles. On the other hand, Example 1, Comparative Example 3 and Comparative Example 4 used the same amount of the space charge reducing agent, but in Example 1 of the present invention showed the most excellent impulse strength.

From these results, the insulator manufactured by the insulating material composition of the direct current power cable of the present invention was able to exert excellent effects in the DC insulation breakdown strength and the impulse strength for the following reason. That is, i) nano carbon particles were used as a space charge reducing agent, ii) the nano carbon particles were used in an appropriate amount.

As described above, optimal embodiments of the present invention have been disclosed. Although specific terms have been used in the specification including the present embodiment, it is only used for the purpose of describing the present invention to those skilled in the art in detail and used to limit the meaning or limit the scope of the present invention described in the claims. Make it clear.

Reference numerals shown in Figs. 1A and 1B mean the following.
One … Conductor
2 … Inner semiconducting layer
3…. Insulating layer
4 … Outer semiconducting layer
5 ... Lead sheath layer
6 ... Polyethylene (PE) sheath layer

Claims (6)

Per 100 parts by weight of the low density polyethylene base resin,
An insulation material composition of a power cable for direct current, comprising 0.05 to 0.5 parts by weight of nano carbon particles. The method of claim 1,
Per 100 parts by weight of the low density polyethylene base resin,
1 to 4 parts by weight of dicumyl peroxide crosslinking agent; And
Insulation material composition of a direct-current power cable, characterized in that it further comprises 0.1 to 1 parts by weight of antioxidant. 3. The method according to claim 1 or 2,
The nano-carbon particles are insulated material composition of the power cable for direct current, characterized in that it comprises a graphite layer of six layers or less. 3. The method according to claim 1 or 2,
The nano-carbon particles have a thickness of less than 10 nm and an average diameter of less than 500 nm, the insulating material composition of the power cable for direct current. 3. The method according to claim 1 or 2,
The nano carbon particles have a density of 1.8 to 2.2 g / cm ³ and an electrical conductivity of 1 × 10 ^-5 to 8 × 10 ^-5 Ω · cm insulated material composition of the power cable for direct current. A direct current power cable comprising an insulator manufactured using the insulating material composition of the direct current power cable according to claim 1.

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