JPH07192543A - Power cable - Google Patents

Abstract

PURPOSE:To provide a power cable simple in handling, good in separation workability, needing no additional work such as recovery after connection, and having the excellent structure of an outside semiconductor layer through manufacture, transport, laying, connection, and/or terminal treatment. CONSTITUTION:This power cable has a feature wherein an outside semiconductor layer 4, provided on the outer side surface of an insulation layer 3, has a thin wall layer 4a formed directly on the insulation layer 3 and a thick wall layer 4b formed on an upper layer than the thin wall layer 4a, and force needed for separating the thin wall layer 4a and the insulation layer 3 is stronger than force needed for separating the thin and thick wall layers 4a and 4b. A separation layer composed of material facilitating the separation of the thick wall layer 4b can be provided between the thin and thick wall layers 4a and 4b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power cable which can be easily connected and processed at a terminal, and more particularly to a power cable having an external semiconductive layer useful for work such as peeling and repair during the work. is there.

[0002]

2. Description of the Related Art A power cable is mainly used for transmitting high-voltage and large-current power to a long distance with a small loss, such as a power transmission line from a power plant. The main structure of the power cable is, as schematically shown in FIG. 3 as an example of a single-core cable, an inner semiconductive layer 2, an insulating layer 3, an outer semiconductive layer 4, and a cushion in order from a conductor 1 at the center to the outside. -It is composed of a coating layer 5 including a sheath and an anticorrosion layer.

The insulating layer 3 is required to be homogeneous in all respects such as shape, composition and physical properties so that its electric strength does not deteriorate with time. That is, partial discharge may occur mainly in any inhomogeneous part such as dents, scratches, internal voids, altered parts, and moisture on the surface of the insulating layer, and the deterioration of the insulating layer progresses from that part. . Also,
The semi-conducting layer relieves a strong electric field generated around the conductor 1, but also has an important meaning for deterioration of the insulating layer. For example, if the semiconductive layer is partially cut off and the insulating layer is exposed, the opening becomes an inhomogeneous portion of the electric field for the insulating layer, and various physical phenomena such as partial discharge occur intensively in this portion, The deterioration of the insulating layer progresses. Further, if a dent or the like applied to the outside of the outer semiconductive layer is transmitted to the insulating layer, the deterioration of the insulating layer also progresses from that portion. As described above, it is important that the semiconductive layer is provided so as not to be missing over the entire length of the insulating layer and not to give local unevenness.

Further, when connecting cables to each other or treating a terminal in actual use, it is necessary to take care not to leave the above-mentioned non-uniform portion in the insulating layer after construction. FIG. 4 is a partial cross-sectional view schematically showing one connection example of a conventional power cable. As shown in the figure, in the connection portion of the conventional power cable, the covering layers 5 to the conductors 1 of the cables A and B to be connected are exposed in a stepwise manner and abutted to each other, and the sleeve 10 for conductor connection and the insulation In many cases, the sleeve 11, the shield layer 12, the exterior tape / tube 13, and other special functional layers and a filler between layers are connected so as to bridge the ends of the layers of the cables A and B with a pipe.

[0005]

As described above, when connecting the power cable and treating the terminal, it is necessary to expose only the necessary portion of the insulating layer covered by the connecting device after the construction. In order to improve the peeling work of the outer semiconductive layer during the construction of such a power cable, a peelable semiconductive layer which is thick and can be easily peeled from the insulating layer has been put into practical use. However, although the peelable semiconductive layer can easily expose the insulating layer, for the convenience of work, a portion wider than a predetermined range has to be removed to perform the connection work. As shown in, it is necessary to return the exposed portion of the extra insulating layer generated after the connection to the original semiconductive layer. Therefore, additional work for repairing the outer semiconductive layer, such as applying semiconductive paint after the connection work, has been a burden. On the other hand, an adhesive semiconductive layer has been proposed in which the outer semiconductive layer is thin and is firmly adhered to the outer surface of the insulating layer. However, while such an external semiconducting layer can be easily and accurately shaved off only the necessary parts, it is thin, so that it can be struck during cable manufacturing, transportation, laying, connection / terminal construction. Traces and scratches easily reached the insulating layer and caused the above deterioration.

The object of the present invention is to solve the above problems,
Provides a power cable with an excellent external semiconductive layer structure that is easy to handle, has good peeling workability, and does not require additional work such as repair after connection through transportation, laying, connection / terminal construction, etc. It is to be.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has provided a thin semiconductive layer firmly adhered to the outer surface of the insulating layer. We have found that by providing a thick semiconductive layer that can be easily peeled off directly or indirectly on the outer surface, it can be peeled off easily while protecting the insulating layer well, and no additional work is required after construction. The present invention has been completed. That is, in the power cable of the present invention, the outer semiconductive layer provided on the outer surface of the insulating layer has a thin layer formed directly on the insulating layer and a thick layer formed above the thin layer. The force required for peeling the thin layer and the insulating layer is larger than the force required for peeling the thin layer and the thick layer. Further, a peeling layer may be interposed between the thin layer and the thick layer for peeling the thick layer more easily.

[0008]

The outer semiconductive layer has a multi-layer structure, and a thick layer that can be easily peeled off is provided on the thin layer that strongly adheres to the insulating layer. Advantages, that is, high-precision peeling processability of thin layers,
Not only is the easy peelability and high protection of the thick layer added, but the advantages of each are the new effects of canceling out the defects of the mating layer.

[0009]

EXAMPLES The present invention will be specifically described below with reference to the drawings based on examples. Needless to say, the present invention is not limited to this. [Embodiment 1] FIG. 1 is a schematic view showing a cross section of a power cable according to an embodiment of the present invention. Similar to FIG. 3, this figure shows a single-core power cable composed of an inner semiconductive layer 2, an insulating layer 3, an outer semiconductive layer 4, and a coating layer 5 in order from the center conductor 1 to the outside. is there. As shown in FIG. 1, in the power cable of the present invention, the outer semiconductive layer 4 provided on the outer surface of the insulating layer 3 is a thin layer 4a formed directly on the insulating layer 3 and a layer above the thin layer 4a. Characterized in that the force required for peeling the thin layer 4a and the insulating layer 3 is stronger than the force required for peeling the thin layer 4a and the thick layer 4b. It is what

As the material of the conductor 1, known good conductors such as copper and aluminum are used. The conductor 1 may be of any known type, and a solid (solid) wire, a stranded wire, and a circular shape, a divided circular shape, a compressed shape, or the like is used for each of these. Further, the inner semiconductive layer 2 and the coating layer 5 are not particularly limited and may be conventionally known ones.

Any material may be used as the material of the insulating layer 3 as long as it can insulate and coat the conductor, but oil-impregnated paper type, oil-impregnated semi-synthetic paper type, rubber and plastic type materials are used. Is mainly used. Examples of rubber and plastic insulating materials include ethylene propylene rubber, butyl rubber, polypropylene, thermoplastic elastomer, polyethylene, crosslinked polyethylene, and the like. In particular, polyethylene and crosslinked polyethylene are the mainstream rubber / plastic insulated cables, The present invention is one of the most effective insulating materials.

The thin layer 4a is preferably a layer that relieves a strong electric field generated around the conductor 1 and does not cause cracking or chipping due to an impact to the extent that is applied during normal handling and construction of a power cable. Further, the force required for peeling the thin layer from the insulating layer 3 is preferably larger than the force required for peeling the thick layer 4b described later from the thin layer 4a. The force required to separate the thin layer and the insulating layer is about 10 kg / half inch or more, and 20 kg / half i
Above nch, it can be easily removed by cutting. The thickness of the thin layer is preferably about 0.03 to 0.3 mm, and particularly preferably about 0.05 to 0.2 mm from the viewpoint of peeling workability. The electrical properties of the thin layer have a volume resistivity of 1 × 10 ⁴ Ω.
· It is preferably cm or less, particularly 1 × 10 to 1 × 10
^It is preferably ³ Ω · cm or less.

The material used for the thin layer is a styrene-butadiene-based or polyester-based thermoplastic elastomer, soft polyolefin such as EVA or EMA, or E.
A semiconductive polymer composition prepared by blending 20 to 70% by weight of conductive carbon black with P rubber or butyl rubber, or a crosslinked product thereof, an adhesive such as an alkyd resin or a phenol resin as a binder, and conductive carbon from 20 to 70
Examples are conductive paints added by weight%, graphite coatings and the like.

As a method of forming the thin layer on the surface of the insulating layer, a method such as continuous extrusion, dipping, spraying or coating can be appropriately adopted depending on the kind of the thin conductive layer material.

The thick layer 4b is similar to the thin layer 4a in the conductor 1
It is only necessary that the strong electric field generated around the periphery of the inner wall is relaxed, the outer layer is absorbed to protect the inner layer, and the inner layer is easily peeled off from the thin layer 4a in connection and the like. However, the thick layer does not have to be directly formed on the thin layer, and may be a layer for interposing other layers such as a layer for further improving the peeling work as described later in Example 2. It may be. The force required to peel off the thick layer 4b and the thin layer 4a is preferably smaller than the force required to peel off the thin layer 4a and the insulating layer 3. The force required to separate the thick layer 4b and the thin layer 4a is 0.05 to 10 kg / half
inch is good, especially 0.2-2.0 kg / half inch
Gives good peeling workability when exposing the thin layer during construction. The thickness of the thick layer is preferably about 0.5 to 2.0 mm from the viewpoint of internal protection and insulation, and 0.8 to
About 1.3 mm is particularly preferable. Regarding the electrical properties of the thick layer, the volume resistivity is preferably 1 × 10 ⁴ Ω · cm or less, as in the case of the thin layer, and particularly 1 × 10 to 1 × 10 ³ Ω · c.
m or less is preferable. Further, in order to easily peel off the thick layer, the tensile strength of 0.2 to 3.0 kg / mm ² and 20
Those having an elongation at break of 0% to 500% are preferable.

The material used for the thick layer is EV
At least one selected from the group consisting of soft polyolefins such as A, EEA, and EMA, rubber-based materials such as EP rubber and butyl rubber, and thermoplastic elastomers such as styrene-butadiene-based or polyester-based, or styrene grafted to these. An example is a crosslinkable or non-crosslinkable composition in which a blended body with the polymer obtained as described above is used as a base polymer, and 30 to 100 parts by weight of conductive carbon black is mixed with 100 parts by weight of the base polymer. Further, if necessary, graphite, a lubricant, a filler, a fine metal powder, a stabilizer, an antioxidant, a cross-linking agent, a cross-linking aid, a processing aid and the like may be appropriately contained.

The method for forming the thick layer on the thin layer is preferably extrusion molding.

[Embodiment 2] In this embodiment, in the power cable shown in Embodiment 1, in order to further improve the workability of peeling the thick layer, a peeling layer is provided between the thin layer and the thick layer. The structure is provided. FIG. 2 is a partially enlarged view schematically showing the cross section of the power cable according to the present embodiment. This figure has the same structure as that of FIG. 1 except that a peeling layer 4c is provided between the thin layer 4a and the thick layer 4b of the outer semiconductive layer 4. With such a structure, the releasability of the thick layer 4b is further improved, and a power cable with high workability and workability during construction can be obtained.

The peeling layer 4c may be a single layer or a multilayer. As the material of the release layer, one or more kinds of higher fatty acid, higher fatty acid metal salt, talc, powdered talc, silica, clay, silicone compound (monomer, oligomer, polymer) and the like are used. Examples of higher fatty acids include saturated / unsaturated fatty acids having 10 or more carbon atoms such as stearic acid, oleic acid, palmitic acid, lauric acid, and lauric acid. Examples of the higher fatty acid metal salt include alkali / alkaline earth metal salts of the above higher fatty acids such as Na, K, Ca, Zn and Mg. As talc, powdered talc, silica, clay, etc., ordinary commercial products may be used.
As the silicone compound, usual silicone oil,
Grease, rubber, etc. are used. The release layer is formed in various modes by using the above materials alone, as a solution / suspension, or as a mixture with a binder. The method for providing the release layer on the outer surface of the thin layer is not particularly limited, and examples thereof include brush coating, spray coating, dipping, and one layer for multilayer extrusion molding. The thickness of the release layer is preferably in the range of 0.01 to 0.2 mm.

The power cable of the present invention can be constructed with a single core or multiple cores as long as the outer semiconductive layer is provided on the outer surface of the insulating layer around the conductor.

[Evaluation Test] The power cable shown in Example 1 was used for actual connection work, and the workability and quality of the work after construction were examined. Table 1 shows the materials, dimensions, and characteristics of the insulating layer, thin layer, and thick layer.

[0022]

[Table 1]

When the above-mentioned power cables were connected to each other with a connection structure similar to that of ordinary construction, the thick layer has an easy peeling property in the thickness direction and the thin layer has an easy and precise property in the longitudinal direction. Due to the excellent peeling property, extremely good workability was obtained, and since additional work such as repair was not required after the construction, the connection was easily completed. The quality of the connection part after construction was good with no exposure of the insulating layer.Moreover, many dents and scratches were added to the entire length of the test piece during the work on other parts as well. It was confirmed that there was no effect at all.

[0024]

The power cable of the present invention has a structure in which the outer semiconductive layer is sufficiently thick as a whole and can protect the insulating layer from external force. The workability of peeling and the quality of the connecting portion are good. Moreover, it is possible to carry out precise processing after construction without requiring additional work such as repair. Therefore, it is easy to handle through the manufacturing, transportation, and laying of electric power cables, has good peeling workability when connecting and connecting terminals, and does not require additional work such as repairing after connection. A power cable can be provided.

[Brief description of drawings]

FIG. 1 is a schematic view showing a partially enlarged cross section of a power cable according to an embodiment of the present invention.

FIG. 2 is a partially enlarged schematic view showing a cross section of a power cable according to another embodiment of the present invention.

FIG. 3 is a diagram schematically showing an example of a structure of a conventional power cable.

FIG. 4 is a partial cross-sectional view schematically showing a connection example of a conventional power cable.

[Explanation of symbols]

 1 conductor 2 inner semiconductive layer 3 insulating layer 4 outer semiconductive layer 4a thin layer 4b thick layer 5 coating layer

Claims (3)

[Claims] 1. An outer semiconductive layer provided on an outer surface of an insulating layer has a thin layer formed directly on the insulating layer and a thick layer formed above the thin layer, the thin layer being a thin layer. A power cable, wherein the force required for peeling off the insulating layer is larger than the force required for peeling off the thin layer and the thick layer. 2. A peeling layer made of a material capable of facilitating peeling of the thick layer between the thin layer and the thick layer.
The power cable shown. 3. The thin layer has a thickness of 0.05 to 0.5 mm,
The power cable according to claim 1, wherein the thick layer has a thickness of 0.5 to 2.0 mm.