JPH08115621A - Power cable - Google Patents

Abstract

PURPOSE: To improve manufacturing wire speed and prevent errosion due to an acetic acid in a copper shielding layer by lowering acetic acid quantity produced in an outside semiconductor layer when crosslinking an insulator. CONSTITUTION: An power cable is constituted by cating an inside semiconductor layer 3, an insulator 4 composed of crosslink polyethylene, an outside semiconductor layer 13, a copper shielding layer composed of a copper tape, and a sheath composed of polyvinyl chloride etc. in this order on a cable conductor 2. Here, the outside semiconductor layer 13 is constituted of two layers of a first layer 11 contacting the insulator 4 and a second layer 12, an outer layer. The first layer 11 is to semiconductor resin, wherein ethylene acetic acid vinyl copolymer, having much acetic acid vinyl content, is adopted as base resin, to keep separation with the insulator 4 at the time of cable laying work. The second layer 12 is to a semiconductor resin, wherein polyethylene or polyethylene copolymer having no acetic acid vinyl at all is adopted as base resin, to lower the production quantity of acetic acid due to the decomposition at the crosslink temperature (at the vicinity of 300 deg.C) at the time of manufacturing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a peelable outer semiconductive layer of a power cable which is coated on an insulator of a power cable, and more particularly, to an outer semiconductive layer which is peeled off from the insulator without lowering peelability from the insulator. It relates to an outer semiconductive layer of a power cable capable of suppressing acetic acid.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 9, a power cable 1 using a cross-linked polyethylene or the like as an insulator has an inner semi-conductive layer 3 extruded and coated on a conductor 2 and an insulating material such as cross-linked polyethylene or the like. The body 4 is extrusion coated. further,
An outer semiconductive layer 5 is extruded and coated on the insulator 4, and a copper shielding layer 6 such as a copper tape is applied on the outer semiconductive layer 5, and the outer semiconductive layer 5 is coated on the copper shielding layer 6. Is covered with a sheath 7 made of polyvinyl chloride or the like, which is called a CV cable. As described above, the structure in which the semiconductive layers (3, 5) are provided on the inner surface side and the outer surface side of the insulator 4 of the power cable 1 by extrusion is to prevent partial discharge at the insulator interface and reduce electric field. It is intended. The volume resistivity of the semiconductive layer extruded and coated on the inner surface side and the outer surface side of the insulator 4 is empirically required to be about 10 ⁵ Ω-cm or less. The inner semiconductive layer 3 and the outer semiconductive layer 5 are obtained by using a synthetic resin as a matrix and adding conductive carbon black.

Since the outer semiconductive layer 5 coated on the insulator 4 made of this crosslinked polyethylene needs to be removed when the power cable 1 is installed, it is necessary to remove a general high voltage cable (extra high voltage cable, ultra high voltage cable). (Excluding the cable), a material having a good peeling property that can be easily peeled from the insulator 4 made of crosslinked polyethylene is used. The releasability of the outer semiconductive layer 5 from the insulator 4 is related to the magnitude of the SP value (solubility parameter) of the two resins to be joined, and generally the difference between the SP values of the resins is large. It has been found that peeling is easier. Therefore, in the conventional base resin material of the outer semiconductive layer 5, a comonomer is copolymerized with ethylene such as ethylene-vinyl acetate copolymer, which has a relatively large difference in SP value with respect to polyethylene which is the material of the insulator 4. It is known that this material is used and the difference in SP value with polyethylene increases as the comonomer content increases.

[0004]

In recent years, in the production of a power cable 1 such as a high voltage CV cable, it has been attempted to increase the linear speed of the production line to improve the production efficiency. Therefore, the insulator 4 in the manufacturing process of the power cable 1
The polyethylene is cross-linked at high temperature in order to shorten the cross-linking time. However, when an ethylene vinyl acetate copolymer having a high vinyl acetate content is used for the base resin of the outer semiconductive layer 5, the ethylene vinyl acetate is not produced at a high temperature (around 300 ° C.) during the cross-linking in the manufacturing process of the power cable 1. The problem is that the copolymer decomposes to generate acetic acid, and the acetic acid corrodes the cross-linking pipe or discolors (corrodes) the copper shielding layer 6 such as a copper tape wound around the outer semiconductive layer 5. Have Therefore, it is necessary to prevent the crosslinking temperature in the manufacturing process of the power cable 1 from rising above the temperature at which the ethylene-vinyl acetate copolymer is not decomposed to generate acetic acid.
The upper limit of the cross-linking temperature becomes a factor to limit the linear velocity in the production of the power cable 1, and there is a problem that the production efficiency in the cross-linking step cannot be improved any more. Further, when an ethylene vinyl acetate copolymer, which is the base resin of the outer semiconductive layer 5, having a high vinyl acetate content is used, the releasability is improved, but the mechanical strength and heat resistance of the outer semiconductive layer 5 are improved. It also has a problem that it decreases.

An object of the present invention is to reduce the amount of acetic acid generated at the time of cross-linking in the production of a power cable without lowering the peeling property from an insulator, to improve the linear velocity in the production of a power cable, copper tape, etc. The purpose is to prevent discoloration of the copper shielding layer due to acetic acid.

[0006]

According to a first aspect of the present invention, there is provided a power cable in which a conductor is coated with an inner semiconductive layer, an insulator is coated thereon, and an outer semiconductive layer is coated on the insulator. And a copper shielding layer is applied on the outer semiconductive layer to coat a sheath. In the power cable, the outer semiconductive layer is made of ethylene-vinyl acetate copolymer having a high vinyl acetate content and polyethylene or acetic acid. It is composed of two layers of an ethylene copolymer containing no vinyl. In the power cable according to the invention as set forth in claim 2, the conductor is coated with the inner semiconductive layer, then the insulator is coated, the insulator is coated with the outer semiconductive layer, and the outer semiconductive layer is coated. In a power cable constituted by applying a copper shielding layer on and covering a sheath, the outer semiconductive layer comprises an ethylene-vinyl acetate copolymer having a high vinyl acetate content and an ethylene-vinyl acetate copolymer having a low vinyl acetate content. And an ethylene copolymer containing no polyethylene or vinyl acetate.

[0007]

According to the first aspect of the present invention, the outer semiconductive layer extruded and coated on the insulator is composed of two layers, and the outer layer of the outer semiconductive layer does not contain polyethylene or vinyl acetate. Since it is formed of a semi-conductive resin based on, the amount of acetic acid generated during cross-linking during power cable production is suppressed while maintaining the same peelability from the insulator as before. The production speed can be improved by increasing the linear velocity and the discoloration of the copper shielding layer on the outer semiconductive layer can be prevented. According to the second aspect of the present invention, three layers of an ethylene vinyl acetate copolymer having a high vinyl acetate content, an ethylene vinyl acetate copolymer having a low vinyl acetate content and an ethylene copolymer not containing polyethylene or vinyl acetate are used as insulators. Since the outer semiconductive layer of the power cable is formed by extrusion coating on top of it, the amount of acetic acid generated during crosslinking during power cable production is maintained while maintaining the same level of peelability from the insulator as before. It is possible to suppress the discoloration of the copper shielding layer due to acetic acid by increasing the linear velocity at the time of manufacturing the power cable to improve the manufacturing efficiency.

[0008]

Embodiments of the present invention will be described below. 1 to 4 show one embodiment of an outer semiconductive layer of a power cable according to the invention described in claim 1 of the present application. In the figure, the same symbols as those used in the conventional power cable 1 of FIG. 9 indicate the same members. The present example is different from the conventional example shown in FIG. 1 in that the conventional example is formed by extruding an ethylene vinyl acetate copolymer having a high VA content in the outer semiconductive layer of a power cable by one layer. Is that the outer semiconductive layer of the power cable has a two-layer structure.

Reference numeral 10 is a power cable, 2 is a conductor, 3 is an inner semiconductive layer, 4 is an insulator, and 13 is an outer semiconductive layer.
Although not shown in FIGS. 1 to 4, like the conventional power cable 1 shown in FIG. 9, a copper shielding layer 6 such as a copper tape is provided on the outer semiconductive layer 13, and the copper shielding layer 6 is provided. Is covered with a sheath 7 made of polyvinyl chloride or the like. External semiconductive layer 1
As shown in FIG. 1, when the outer semiconductive layer 13 is extruded on the insulator 4, the outer semiconductive layer 13 is formed.
Is divided into two layers, and a semiconductive material having an ethylene vinyl acetate copolymer having a high vinyl acetate content as a base resin is extruded on the surface of the insulator 4 to form a first layer 11.
The second layer 12 is formed by extrusion-coating on 1 a semiconductive material whose base resin is an ethylene copolymer containing no polyethylene or vinyl acetate.

FIG. 2 is a longitudinal sectional view of FIG. 1, and FIG.
The external semiconductive layer 13 is formed in a state in which the first layer 11 and the second layer 12 are overlapped with each other. Power cable 1 configured in this way
At 0, since the second layer 12 contains no acetic acid,
Even in a high temperature state (about 300 ° C.) at the time of crosslinking in the manufacturing process of the power cable 10, acetic acid is not generated due to the decomposition of the ethylene-vinyl acetate copolymer. Therefore, the amount of deacetic acid in the entire outer semiconductive layer 13 can be reduced, and the discoloration of the copper shielding layer 6 can be prevented.

Further, when the power cable 10 is constructed, as shown in FIG. 4, a spiral cut 15 is made on the surface of the outer semiconductive layer 13 with a tool or the like so that the layers of the outer semiconductive layer 13 are not separated from each other. When peeling from the insulator 4 in a batch, the first layer 1 of the outer semiconductive layer 13 on the surface in contact with the insulator 4
Since 1 is composed of a semi-conductive material whose base resin is an ethylene vinyl acetate copolymer containing a large amount of vinyl acetate, the SP value difference with the insulator 4 can be adjusted to a large extent, and easily peeled from the insulator 4. be able to.

FIG. 5 to FIG. 8 show an embodiment of the outer semiconductive layer of the power cable according to the invention described in claim 2 of the present application. In the figure, the same reference numerals used in FIG. 5 indicate the same members. This example is different from the conventional example shown in FIG. 5 in that the conventional example is formed by extruding an ethylene vinyl acetate copolymer having a high vinyl acetate content in the outer semiconductive layer of a power cable in a single layer. An example is a power cable with a three-layer outer semiconductive layer.

Reference numeral 20 is a power cable, 2 is a conductor, 3 is an inner semiconductive layer, 4 is an insulator, and 24 is an outer semiconductive layer.
Although not shown in FIGS. 5 to 8, like the conventional power cable 1 shown in FIG. 9, a copper shield layer 6 is provided on the outer semiconductive layer 24, and polychlorinated on the copper shield layer 6. A sheath 7 made of vinyl or the like is covered. As shown in FIG. 5, the outer semiconductive layer 24 is divided into three layers when the outer semiconductive layer 24 is extruded and molded on the insulator 4, and the outer semiconductive layer 24 is divided into three surfaces. A semiconductive material having an ethylene vinyl acetate copolymer having a high vinyl acetate content as a base resin is extruded to form a first layer 21, and an ethylene vinyl acetate copolymer having a low vinyl acetate content is formed on the first layer 21. The second layer 22 is formed by extruding and covering a semiconductive material using the coalesce as a base resin, and a semiconductive material using a polyethylene or a vinyl acetate-free ethylene copolymer as a base resin on the second layer 22. Is extrusion coated to form the third layer 23.

FIG. 6 is a vertical sectional view of FIG. 5, and FIG.
FIG. 3 is an enlarged view of a part of FIG. 1, in which the outer semiconductive layer 24 is formed in a state in which the first layer 21, the second layer 22, and the third layer 23 overlap each other. In the power cable 20 configured in this manner, the second layer 22 has a low acetic acid content, and the third layer 23 does not contain acetic acid at all, so that the high temperature state at the time of crosslinking in the manufacturing process of the power cable 20 ( 300 ° C
However, the generation of acetic acid due to the decomposition of the ethylene vinyl acetate copolymer is small. Therefore, the amount of deacetic acid in the entire outer semiconductive layer 24 can be reduced, and the discoloration of the copper shielding layer 6 can be prevented.

When constructing the power cable 20, the outer semiconductive layer 24 is cut from the insulator 4 to the surface of the outer semiconductive layer 24 by making a spiral cut 25 with a tool as shown in FIG. When the peeling strength between the layers of the semiconductive layer 24 is adjusted and the layers of the external semiconductive layer 24 are peeled together so as not to be peeled off, the external semiconductive layer 2 on the surface in contact with the insulator 4
Since the first layer 21 of No. 4 is made of a semiconductive material whose base resin is an ethylene vinyl acetate copolymer containing a large amount of vinyl acetate, the difference in SP value with the insulator 4 can be adjusted to a large extent, and external semiconductive The layer 24 can be easily peeled off from the insulator 4. As the copper shielding layer, a so-called wire shield in which a copper tape or a copper wire is tightly wound is used.

[0016]

According to the first aspect of the present invention, the conductor is coated with the inner semiconductive layer, then the insulator is coated, and the insulator is coated with the outer semiconductive layer. In a power cable constituted by applying a copper shielding layer on a semi-conductive layer and covering a sheath, the outer semi-conductive layer comprises an ethylene-vinyl acetate copolymer having a high vinyl acetate content and polyethylene or an ethylene copolymer not containing vinyl acetate. Since it is composed of two layers of polymer, it reduces the amount of acetic acid generated during cross-linking when manufacturing a power cable without lowering the peeling property from the insulator, and improves the linear velocity during power cable manufacturing. It is possible to prevent discoloration of the copper shielding layer due to acetic acid. According to the second aspect of the present invention, the conductor is coated with the inner semiconductive layer, then the insulator is coated, the insulator is coated with the outer semiconductive layer, and the outer semiconductive layer is coated. In a power cable constituted by applying a copper shielding layer to a sheath and covering a sheath, the outer semiconductive layer comprises an ethylene-vinyl acetate copolymer having a high vinyl acetate content, an ethylene-vinyl acetate copolymer having a low vinyl acetate content, and polyethylene. Or, since it is composed of three layers of ethylene copolymer that does not contain vinyl acetate, it reduces the amount of acetic acid generated during cross-linking when manufacturing a power cable without lowering the peeling property from the insulator, and the power cable It is possible to improve the linear velocity during manufacturing and prevent discoloration of the copper shielding layer due to acetic acid.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a power cable according to the invention of claim 1 of the present invention in a state in which a tape and a sheath of the power cable are removed.

2 is a vertical cross-sectional view of the power cable illustrated in FIG.

3 is a partial enlarged cross-sectional view of the power cable illustrated in FIG. 1. FIG.

FIG. 4 is a diagram showing a state in which the external semiconductive layer shown in FIG. 1 is peeled off.

FIG. 5 is a cross-sectional view showing an embodiment of a power cable according to the invention of claim 2 of the present invention in a state where a copper shielding tape and a sheath are removed.

FIG. 6 is a vertical cross-sectional view of the power cable illustrated in FIG.

7 is a partial enlarged cross-sectional view of a portion of the power cable shown in FIG.

FIG. 8 is a diagram showing a state in which the external semiconductive layer shown in FIG. 5 is peeled off.

FIG. 9 is a cross-sectional view of a conventional power cable.

[Explanation of symbols]

10, 20, 30 ………………………………………… Power cable 2 ………………………………………………………… Conductor 3… ………………………………………………………… Internal semiconductive layer 4 ……………………………………………………………… Insulators 11 and 21 …………………………………………………… 1st layer 12, 22 ………………………………………………… 2nd layer 23 ……………………………………………………………… 3rd layer 13,24 …………………………………………………… External semi-conductive layer 15,25 …………………………………………………… Notch 6 ………………………………………………………… …… Copper shielding layer 7 ……………………………………………………………… Sheath

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[Procedure amendment]

[Submission date] February 2, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008]

Embodiments of the present invention will be described below. 1 to 4 show one embodiment of an outer semiconductive layer of a power cable according to the invention described in claim 1 of the present application. In the figure, the same symbols as those used in the conventional power cable 1 of FIG. 9 indicate the same members. This example is different from the conventional example shown in FIG. 9 in that the conventional example was formed by extruding an ethylene vinyl acetate copolymer having a high VA content in the outer semiconductive layer of a power cable in a single layer. Is that the outer semiconductive layer of the power cable has a two-layer structure.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

FIG. 5 to FIG. 8 show an embodiment of the outer semiconductive layer of the power cable according to the invention described in claim 2 of the present application. In the figure, the same symbols as those used in FIG. 9 indicate the same members. This example is different from the conventional example shown in FIG. 9 in that the conventional example is formed by extruding an ethylene vinyl acetate copolymer having a high vinyl acetate content in the outer semiconductive layer of a power cable by one layer. An example is a power cable with a three-layer outer semiconductive layer.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

FIG. 6 is a vertical sectional view of FIG. 5, and FIG.
FIG. 3 is an enlarged view of a part of FIG. 1, in which the outer semiconductive layer 24 is formed in a state in which the first layer 21, the second layer 22, and the third layer 23 overlap each other. In the power cable 20 configured in this manner, the second layer 22 has a low acetic acid content, and the third layer 23 does not contain acetic acid at all, so that the high temperature state at the time of crosslinking in the manufacturing process of the power cable 20 ( 300 ° C
Near) But have Gana generation of acetic acid by the decomposition of ethylene-vinyl acetate copolymer. Therefore, the amount of deacetic acid in the entire outer semiconductive layer 24 can be reduced, and the discoloration of the copper shielding layer 6 can be prevented.

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Correction target item name] Figure 8

[Correction method] Change

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[Figure 8]

Claims (2)

[Claims] 1. After coating an inner semiconductive layer on the conductor,
A power cable comprising an insulator, an outer semiconductive layer on the insulator, a copper shielding layer on the outer semiconductive layer, and a sheath to cover the outer semiconductive layer. A power cable composed of two layers of an ethylene-vinyl acetate copolymer having a high vinyl acetate content and polyethylene or an ethylene copolymer containing no vinyl acetate. 2. After coating an inner semiconductive layer on the conductor,
A power cable comprising an insulator, an outer semiconductive layer on the insulator, a copper shielding layer on the outer semiconductive layer, and a sheath to cover the outer semiconductive layer. A power cable comprising three layers of an ethylene-vinyl acetate copolymer having a high vinyl acetate content, an ethylene-vinyl acetate copolymer having a low vinyl acetate content, and an ethylene copolymer containing no polyethylene or vinyl acetate.