KR20210139068A - Composition for eco-friendly insulator, and cable using the same for dc power cable - Google Patents

Abstract

The present invention relates to an eco-friendly insulating composition for a direct current power cable, and a direct current power cable manufactured using same. Provided are the eco-friendly insulating composition for the direct current power cable, and the direct current power cable manufactured using the same, wherein the composition is effectively mixed with polypropylene and elastomer so as to exhibit high insulation and be useable under the condition of a maximum use temperature of 110℃ or higher.

Description

Eco-friendly insulation composition for DC power cables and cables manufactured using them

The present invention relates to an eco-friendly insulating composition for a DC power cable and a cable manufactured using the same. More particularly, it relates to an eco-friendly insulating composition for a DC power cable and a cable manufactured using the same.

The existing power grid is centered on the AC power transmission system that can flexibly transform the voltage level from the transmission stage to the end user stage and apply the optimal voltage for each use.

However, the AC power transmission system basically has a frequency component, and energy loss occurs under the influence of impedance including the resistance and capacitance of the transmission line.

In addition, since direct connection between two power systems having different frequencies is impossible, it acts as an obstacle to the efficient operation of power facilities.

High Voltage Direct Current Transmission System (HVDC), which has recently emerged for the purpose of long-distance transmission and linking with new and renewable energy, is a mutual conversion between the transmission distance limitation and linkage of systems with different frequencies, which are the disadvantages of the existing AC power transmission system described above. It can be solved through

Another advantage of such ultra-high voltage direct current transmission is that it provides power transmission capacity that is more than twice that of an AC power transmission system while using the same power line.

Recently, as a material constituting the insulating layer of a power cable, cross-linked polyethylene obtained by polymerizing polyethylene through a cross-linking reaction using organic peroxide is mainly used.

However, cross-linked polyethylene may cause environmental problems by generating cross-linking by-products such as methane gas, alpha methyl styrene, acetphenone, and carbon dioxide during the cross-linking process. There are problems that can cause it.

In addition, when used in a DC power cable, due to the problem of accumulating space charges by cross-linking by-products generated during the cross-linking process, a local or regional electric field distortion effect may occur, resulting in insulation breakdown.

On the other hand, in the case of cross-linked polyethylene for DC power cables that have been commercialized and used recently, although the problem of space charge accumulation has been solved, the maximum operating temperature for cable operation is limited to about 70 degrees due to the limitations of the thermal and mechanical properties of the material. .

In order to solve this problem, Korean Patent Application Laid-Open No. 10-2020-0004061 discloses a material using polypropylene as a base resin, which has excellent heat resistance and is environmentally friendly even without crosslinking, but insufficient cold resistance caused by high rigidity. Due to problems such as , flexibility, flexibility, etc., there is a problem in that workability is deteriorated during installation of an insulated cable and its use is limited.

Therefore, there is a demand for a new insulating composition capable of stably operating at a high temperature under a DC system.

Korea Patent Publication No. 10-2020-0004061 (2020.01.13)

The present invention provides an eco-friendly insulation composition for a DC power cable that can be used stably at high temperature due to a low degree of increase in conductivity at high temperature and high dielectric breakdown strength under DC voltage conditions, and manufactured using the same in order to improve the conventional problems as described above. The purpose is to provide a cable.

In order to achieve the above object, the eco-friendly insulation composition for a DC power cable according to the present invention contains an elastomer and an additive in polypropylene to improve dielectric strength and mechanical properties.

The polypropylene may be included in an amount of 30% by mass or more and 70% by mass or less, and the elastomer may be included in an amount of 30% by mass or more and 70% by mass or less.

The DC insulation breaking strength of the eco-friendly insulating composition may be 200 kV/mm or more and 250 kV/mm or less in a room temperature range of 15 degrees or more and 30 degrees or less, and the conductivity may be 10 ^-17 S/m or more and 10 ^-16 S/m or less.

The dielectric breakdown strength of the eco-friendly insulating composition may be 150 kV/mm or more and 200 kV/mm or less in the high temperature range that is the maximum use temperature of the conductor, and the conductivity may be 10 ^-14 S/m or more and 4 X 10 ^-13 S/m or less.

The polypropylene may include at least one of homopropylene, random propylene, block propylene, and reactive polyolefin produced in a polymerization facility.

The elastomer may include at least one of polystyrene-based, PVC-based, polyolefin-based, polyester-based, polyamide-based, and polyurethane-based materials.

The additive may include at least one or more from the group consisting of an antioxidant, a nucleating agent, a slip agent, a lubricant, and an antifreeze agent.

In addition, the eco-friendly insulating cable for a DC power cable according to the present invention is manufactured by mixing the eco-friendly insulating composition.

The eco-friendly insulating composition may be disposed between the first semiconducting layer and the second semiconducting layer in the insulating cable to form an insulating layer.

The eco-friendly insulated cable is characterized in that the maximum use temperature is 110 degrees or more.

As described above, according to the eco-friendly insulation composition for a DC power cable according to the present invention and a cable manufactured using the same, there is no cross-linking reaction, so cross-linking by-products do not occur, and problems such as insulation performance degradation do not occur. Efficient mixing of propylene and elastomer shows high insulation and can be used under the condition that the maximum operating temperature is 110 degrees or higher.

1 is a cross-sectional view showing an eco-friendly insulated cable for a DC power cable according to an embodiment of the present invention.
2 is a graph showing the measurement of the dielectric breakdown strength at which insulation is broken in the eco-friendly insulation composition for a DC power cable according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and will be described in detail in the detailed description. This is not intended to limit the present invention to specific embodiments, and should be construed to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

In describing the present invention, terms such as first, second, etc. may be used to describe various components, but the components may not be limited by the terms. The above terms are only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component.

The term “and/or” may include a combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being “connected” or “connected” to another component, it may be directly connected or connected to the other component, but other components may exist in between. can be understood On the other hand, when it is mentioned that a certain element is "directly connected" or "directly connected" to another element, it may be understood that the other element does not exist in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression may include the plural expression unless the context clearly dictates otherwise.

In the present application, terms such as "comprise" or "have" are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, and one or more other features It may be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded in advance.

Unless defined otherwise, all terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in a commonly used dictionary may be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, it is interpreted in an ideal or excessively formal meaning. it may not be

In addition, the following embodiments are provided to more completely explain to those with average knowledge in the art, and the shapes and sizes of elements in the drawings may be exaggerated for clearer description.

1, the eco-friendly insulated cable for a DC power cable according to an embodiment of the present invention is disposed between the first semiconducting layer 20 and the second semiconducting layer 40, so that the insulation of the insulated cable under high temperature conditions is improved. It includes an insulating layer 30 made of an eco-friendly insulating composition for a DC power cable to prevent it from being destroyed.

In detail, an eco-friendly insulated cable for a DC power cable includes a conductor 10 through which power is transmitted, a first semiconducting layer 20 surrounding the conductor 10, a sheath layer 50 protecting the cable, and a sheath layer 50. It consists of a second semiconducting layer 40 formed therein, a first semiconducting layer 20 , and an insulating layer 30 positioned between the second semiconducting layer 40 .

The eco-friendly insulated cable can be used at a higher temperature than general crosslinked polyethylene that can be used up to about 70 degrees because the maximum use temperature is 110 degrees or more, and the allowable current value can increase according to the increase in the use temperature.

An eco-friendly insulating composition for a DC power cable according to another embodiment of the present invention is formed by including at least one of an elastomer and an additive in polypropylene to improve dielectric strength and mechanical properties.

Specifically, polypropylene contains 30% by mass or more and 70% by mass or less, and the elastomer contains 30% by mass or more and 70% by mass or less. It provides an insulating composition that can have.

When polypropylene is less than 30% by mass or elastomer is more than 70% by mass, it is mainly composed of elastomer, so it is difficult to obtain insulation properties required for insulated cables despite high elasticity.

In addition, when polypropylene exceeds 70 mass % or elastomer is less than 30 mass %, there is a problem in that the flexural characteristics of the cable may be increased and installation may be difficult.

The DC insulation breaking strength of the eco-friendly insulating composition may be 200 kV/mm or more and 250 kV/mm or less in a room temperature range of 15 degrees or more and 30 degrees or less, and the conductivity may be 10 ^-17 S/m or more and 10 ^-16 S/m or less.

The DC dielectric breakdown strength of the eco-friendly insulation composition may be 150 kV/mm or more and 200 kV/mm or less in the high temperature range that is the maximum conductor temperature, and the conductivity may be 10 ^-14 S/m or more and 4 X 10 ^-13 S/m or less.

Characteristics of the eco-friendly insulation composition for DC power cables show higher dielectric breakdown strength and lower conductivity than the comparative group, cross-linked polyethylene.

Polypropylene and elastomer are manufactured into an insulating material in the form of particles or pellets through extrusion and cutting processes after mixing.

When an insulating composition is manufactured using polypropylene as a basic raw material, no crosslinking process is required, so the manufacturing process is simple, toxic substances such as methane gas and various by-products are not generated _{, greenhouse gases such as CO 2} are reduced, and even after disposal It can be recycled into various plastic products. When the crosslinking process is eliminated, the manufacturing speed and efficiency of the insulating composition are increased.

In addition, the insulation composition prepared by blending polypropylene and elastomer can be used at a maximum operating temperature (permissible temperature) of a power cable of 110 degrees or more and below the melting point of the composition due to the excellent heat resistance of polypropylene, thereby increasing the power transmission capacity. there are advantages to

The polypropylene may include homopropylene, random propylene, block propylene, and reactive polyolefin prepared in a polymerization facility according to processing or manufacturing methods.

Polypropylene is a random polypropylene that is randomly arranged according to the arrangement of the propylene. It includes at least one of homo polypropylene arranged in the same direction, block polypropylene in which a propylene monomer and heterogeneous monomers such as styrene are bonded, and reactive polyolefin produced in a polymerization facility.

Impact strength and flexibility can be improved through random polypropylene with many irregularities, and high rigidity and heat resistance can be obtained through homo polypropylene with high crystallinity.

In addition, through block polypropylene polymerized by adding ethylene to propylene during the production process, impact resistance can be greatly improved without significantly lowering rigidity.

The elastomer may include at least one of polystyrene-based, PVC-based, polyolefin-based, polyester-based, polyamide-based, and polyurethane-based materials.

Preferably, since the polystyrene-based elastomer closest to vulcanized rubber is applied because it has high flexibility and little permanent deformation, it has thermoplasticity, so that it is easy to process or reuse and excellent elasticity can be obtained.

In addition, when a PVC-based or polyolefin-based elastomer is used, it has the advantage of being inexpensive and easy to process.

In addition, the eco-friendly insulation composition for a DC power cable according to the present invention may include at least one or more from the group consisting of an antioxidant, a nucleating agent, a slip agent, a lubricant, and an antifreeze agent as an additive.

Additives may include more than 0 mass % and 1 mass % or less, and may be used for functional enhancement such as improvement of processability in addition to oxidation prevention.

When the additive exceeds 1% by mass, electrical properties may be deteriorated because electric charges may be accumulated in molecules to cause dielectric breakdown despite the improvement of thermal and mechanical properties of the insulating composition.

Antioxidants may be added to prevent oxidization by oxygen in the air and cause deterioration in quality during manufacture or use of the eco-friendly insulation composition. As the antioxidant, any antioxidant commonly used in the art may be used, but preferably one or more of phenolic and phosphorus antioxidants may be used.

The nucleating agent makes polypropylene crystals dense, preventing the accumulation of space charges in the eco-friendly insulation composition, improving the withstand voltage characteristics of power cables, and removing organic substances such as sorbitol, inositol, and glucose. Can be used.

Slip agents and lubricants improve the flowability of the eco-friendly insulating composition during extrusion, and may be added to improve the appearance of the extrusion.

A metal deactivator may be used to prevent decomposition by a small amount of ionic impurities contained in the insulator.

Hereinafter, the effects of the present invention will be described through experiments,

An eco-friendly insulating composition was prepared as an example in comparison with the commercial cross-linked polyethylene insulation composition for DC power cables that could be used in DC power cables according to the present invention, and the conductivity and DC breakdown field values according to temperature were measured and compared.

(Example 1-2 / Comparative Example)

In the Examples and Comparative Examples, eco-friendly insulating compositions were prepared as reported in Table 1.

The eco-friendly insulating composition was manufactured by using a twin extruder having a diameter of 30 mm and an L/D of 40, and the processing temperature was set at 170 to 190°C of the cylinder, and the head and die parts were set at 200°C to proceed with the process.

The proportion of each polymer in the eco-friendly insulating composition is expressed in mass% with respect to the total weight of the composition.

comparative example Example 1 Example 2 crosslinked polyethylene 100 polypropylene 30 70 elastomer 70 30

As the cross-linked polyethylene used as a comparative example, commercially available cross-linked polyethylene for DC power cables was used. (Borealis, LS 4258 DCE)

As the polypropylene used in Examples, block polypropylene prepared by copolymerizing propylene and ethylene to improve impact strength and reactive polyolefin prepared in a propylene polymerization facility were used, and MI (melt index) was 0.5 and 0.8, respectively.

As the elastomer, a reactive polyolefin-based elastomer prepared in a polymerization facility and a styrene-ethylene-butadiene copolymer having a polystyrene content of 12% by mass were used.

To the composition of Table 1, 0.2 mass % of antioxidants (phenolic and phosphorus) were added, blended, and extruded to prepare pellets, and then physical properties were measured.

The measured physical properties are shown in Table 2, Table 3 and Figure 2 below,

item unit comparative example Example 1 Example 2 tensile strength MPa 23.0 23.8 25.9 elongation % 606 607 766 residual rate after aging
(Comparative example:
135°C/168hr
Example:
135°C/240hr) Seal
burglar % -4.5 -4.5 -4.0 elongation % -6.8 -12.0 -9.8 density g/cm ³ 0.92 0.89 0.88 MI g/10 min 2.0 1.1 1.2 Cold-resistant hitting test
(-40 degrees) number of fractured specimens 0 0 0 flexural modulus MPa 180 158 172

Referring to Table 2, Example 1 containing 30% by mass of polypropylene and 70% by mass of elastomer and Example 2 containing 70% by mass of polypropylene and 30% by mass of elastomer have elongation by the elastomer compared to Comparative Example. To provide an insulating composition with excellent tensile strength while improving.

In addition, since Examples 1 and 2 show very low values in Melt Index (MI) than Comparative Examples, it can be confirmed that excellent extrudability provides a composition suitable for manufacturing an insulated cable.

In addition, in the flexural modulus, Examples 1 and 2 show a lower flexural modulus than the comparative example, and thus it can be confirmed that the processability is improved compared to the comparative example using cross-linked polyethylene.

conductivity
(S/m) Measured temperature comparative example Example 1 Example 2 room temperature
(15-30 degrees) 5x10 ^-16 to 3x10 ^-15 3x10 ^-17 to 7x10 ^-17 1x10 ^-17 to 2x10 ^-17 medium temperature
(less than 70 degrees) 8x10 ^-14 to 2x10 ^-13 1x10 ^-14 to 4x10 ^-14 8x10 ^-16 to 2x10 ^-15 High temperature
(70 degrees to 110 degrees or more) 4x10 ^-13 to 6x10 ^-13 2x10 ^-13 to 4x10 ^-13 1x10 ^-14 to 2x10 ^-14

Referring to Table 3, Example 1 containing 30% by mass of polypropylene and 70% by mass of elastomer ^{shows a conductivity of 3x10 -17} S/m or more and 7x10 ^-17 S/m or less in the room temperature range (15 to 30 degrees) ^{, It shows conductivity of 1x10 -14} S/m or more in the mid-temperature range (less than 70 degrees) and ^{4x10 -14 S/m or more, and 2x10 -13} S/m or more in the high-temperature range (70-110 degrees or more) ^{4x10 -13} S/m or more The following conductivity is shown.

Example 2 containing 70% by mass of polypropylene and 30% by mass of elastomer ^{shows a conductivity of 1x10 -17} S/m or more and 2x10 ^-17 S/m or less in the room temperature range, and 8x10 ^-16 S/m or more 2x10 in the intermediate temperature range ^It shows the conductivity of -15 S/m or more, and it shows the conductivity of 1x10 ^-14 S/m or more and 2x10 ^-14 S/m or less in the high temperature range.

On the other hand, the comparative example containing cross-linked polyethylene ^{shows a conductivity of 5x10 -16} S/m or more and 3x10 ^-15 S/m or less in the room temperature range, and 8x10 ^-14 S/m or more and 2x10 ^-13 S/m or more in the medium temperature range. ^{and shows the conductivity of 4x10 -13} S/m or more and 6x10 ^-13 S/m or less in the high temperature range.

Through this, it is confirmed that the eco-friendly insulating composition is more preferably contained in an amount of 40% by mass or more and 50% by mass or less of polypropylene, and 50% by mass or more and 60% by mass or less of elastomer.

2, in order to measure the dielectric breakdown strength at which insulation is broken in the insulated cable manufactured by the eco-friendly insulating composition of Examples 1 and 2, a sample was prepared in a size of 50x50 mm, and the upper and lower identical electrodes were placed on both sides of the sample. By increasing the voltage step by step, the voltage at which destruction occurs was measured and divided by the thickness.

Comparative Example Measurement was also carried out in the same manner.

In the room temperature range (15 to 30 degrees), Example 1 shows a dielectric breakdown strength close to about 250 kV/mm, and Example 2 shows a dielectric breakdown strength slightly exceeding 200 kV/mm, whereas Comparative Example is more than 200 kV/mm It shows low dielectric breakdown strength.

From this, it can be confirmed that Example 1 is the most preferable eco-friendly insulating composition in the room temperature range.

In the high temperature range (70 to 110 degrees or more), Example 1 shows a dielectric breakdown strength of about 165 kV/mm, Example 2 shows an improved dielectric breakdown strength of about 180 kV/mm compared to Example 1, whereas Comparative Example is about It has a dielectric breakdown strength of 155 kV/mm.

From this, it can be confirmed that Example 2 is the most preferable eco-friendly insulating composition in the high temperature range.

As described above, since the optimum value is shown in different compositions according to the temperature range, the practitioner can selectively implement the composition and utilize it.

Although the present invention has been described in detail through specific examples, it is intended to describe the present invention in detail, and the present invention is not limited thereto. It is clear that the transformation or improvement is possible by the person.

All simple modifications and variations of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be made clear by the appended claims.

Figure 1

Claims (10)

An eco-friendly insulation composition for DC power cables that contains elastomer and additives in polypropylene to improve insulation and mechanical properties.
The method according to claim 1,
The polypropylene is
30% by mass or more and 70% by mass or less,
The elastomer is
An eco-friendly insulation composition for DC power cables containing 30% by mass or more and 70% by mass or less.
The method according to claim 1,
Eco-friendly insulation for DC power cables, characterized in that at a temperature of 15 degrees or more and 30 degrees or less, the breaking strength of DC insulation is 200 kV/mm or more and 250 kV/mm or less, and the conductivity is 10 ^-17 S/m or more and 10 ^{-16 S/m or less.} composition.
The method according to claim 1,
Eco-friendly insulation for DC power cables, characterized in that the dielectric breakdown strength is 150kV/mm or more and 200kV/mm or less, and the conductivity is 10 ^-14 S/m or more and 4 X 10 ^{-13 S/m or less in the high temperature range, which is the maximum operating temperature of the conductor} composition.
The method according to claim 1,
The polypropylene is
An eco-friendly insulation composition for DC power cables containing homopropylene, random propylene, block propylene, and reactive polyolefin manufactured in a polymerization facility.
The method according to claim 1,
The elastomer is
An eco-friendly insulation composition for a DC power cable, comprising at least one of polystyrene-based, PVC-based, polyolefin-based, polyester-based, polyamide-based, and polyurethane-based.
The method according to claim 1,
The additive is
An eco-friendly insulating composition for a DC power cable comprising at least one from the group consisting of antioxidants, nucleating agents, slip agents, lubricants and anti-freeze agents.
A DC power cable manufactured by blending the eco-friendly insulation composition according to any one of claims 1 to 7.
9. The method of claim 8,
The eco-friendly insulating composition,
DC power cable, characterized in that it is disposed between the first semiconducting layer and the second semiconducting layer to form an insulating layer.
9. The method of claim 8,
DC power cable, characterized in that the maximum operating temperature is 110 degrees or more.

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