JPH05325652A - Electric wire, cable - Google Patents

Abstract

PURPOSE:To suppress an occurrence of a water tree even when such defects exist in an insulator as voids, foreign matters, and irregularities on the boundary face between the insulator and a semiconducting layer. CONSTITUTION:An electric insulating layer of an electric wire or cable is made of a resin composition combined with a styrene maleic anhydride copolymer into polyethylene, an ethylene copolymer, or a mixture of them at the maleic acid content of 0.02-5wt.%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to electric wires and cables,
In particular, it relates to electric wires and cables with significantly improved water resistance.

[0002]

2. Description of the Related Art Polyolefin, in particular, cross-linked polyethylene, so-called cross-linked polyethylene, is widely used as an insulating material for electric wires and cables because of its excellent electric insulation and heat resistance.

However, the crosslinked polyethylene insulated wire / cable has a problem that when it is used in a wet or flooded atmosphere, a water tree is generated in the insulator, and the excellent electrical insulation performance of the material is significantly deteriorated.

That is, the general structure of a high-voltage insulated cable has a structure in which an inner semiconductive layer is provided on a conductor, an insulator is provided on the outer periphery of the conductor, and an outer semiconductive layer is provided on the outer periphery of the insulator. However, a bow-tie water tree is generated inside the insulator, and an interfacial water tree is generated from the inner semiconducting layer or the outer semiconducting layer. In the worst case, it penetrates the insulator layer and causes dielectric breakdown. There are even things.

A water tree is generated by agglomeration of water in a local high electric field portion such as a void in an insulator, a foreign substance, and an irregularity at the interface between the insulator and the semiconductive layer. Therefore, removing these defects in the insulator can prevent the generation of water trees.Currently, the quality control of the resin and the improvement of the electric wire / cable manufacturing technology prevent the generation of water trees. There is.

[0006]

[Problems to be Solved by the Invention]
According to the cable, it is difficult to completely remove the defects in the insulation even if the quality control of the resin and the manufacturing technology of the electric wire / cable are improved. There is an inconvenience that you cannot do it.

Therefore, an object of the present invention is to provide an electric wire / cable capable of suppressing the generation of a water tree even if there are defects such as voids, foreign matters, and irregularity of the interface between the insulator and the semiconductive layer in the insulator. Is to provide.

[0008]

In view of the above problems, the present invention suppresses the generation of a water tree even if there are defects such as voids, foreign matters, and irregularities at the interface between the insulator and the semiconductive layer in the insulator. In order to be able to do so, the polyethylene or ethylene copolymer, or a mixture of these with styrene / maleic anhydride copolymer with a maleic acid content of 0.02-5 w
It is intended to provide an electric wire / cable in which an electric insulating layer is composed of a resin composition blended so as to be t%.

Examples of the base resin include low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-propylene copolymer, and other polyolefins containing a majority of ethylene. Is applicable. Of these, one kind or a combination of two or more kinds may be used.

The content of maleic acid of 0.02 to 5% by weight means that when the content is less than 0.02% by weight, there is no effect of resistance to boutite resistance and precipitation of additives occurs.
This is because if t% is exceeded, the electrical characteristics deteriorate. A typical example of the styrene / maleic anhydride copolymer is represented by the following general formula.

[Chemical 1]

The above resin composition is coated on the outer circumference of the conductor directly or via an inner semiconductive layer to form a crosslinked or non-crosslinked electric insulating layer. In the case of cross-linking, it is general to heat-crosslink with a peroxide typified by dicumyl peroxide, 2,5-dimethyl-2,5- (t-butylperoxy) hexyne-3. Further, an organic silane such as vinyltriethoxysilane is grafted to a polymer and brought into contact with water to condense and crosslink the silane with a silanol condensation catalyst, so-called silane water crosslinking,
Alternatively, crosslinking by irradiation with ionizing radiation such as an electron beam may be used.

Further, if necessary, a lubricant, a coloring agent, a filler, a crosslinking accelerator, etc. may be added to the above resin composition.

The influence of water on the bow tie tree is extremely large, and the voltite tree has been found in a cable that is electrically charged in the air or a cable that is shielded by a metal sheath. These are not due to the infiltrated water from the outside, but to the trace amount of water contained in the cross-linked polyethylene at the time of manufacturing the cable. It goes without saying that the insulator of the present invention is also effective for such a bowtie tree.

[0014]

EXAMPLES The electric wires and cables of the present invention will be described in detail below.

The composition having the composition shown in Table 1 was kneaded with a hot roll at 120 ° C. to prepare a sheet, which was pelletized with a pelletizer. Next, the pellets were introduced into an extruder and the outer diameter was 3
A 0.5 mm thick inner semiconductive layer and an outer semiconductive layer, respectively, were extruded as a 2 mm thick insulating layer on a mm conductor. Immediately thereafter, crosslinking is performed in a dry crosslinking tube using nitrogen gas as a heat medium, and then pressure cooling is performed to complete the cable, and five types (Examples 1, 2, 3, and Comparative Examples 1, 2) are obtained. A sample of was obtained.

Next, these samples were evaluated with respect to the number of occurrence of boutrite, the presence or absence of bloom of additive, and the quality of dielectric loss tangent. Each evaluation was based on the following. (1) Number of Bow Tightly Occurrence The electric wire produced as described above was immersed in warm water of 90 ° C., and AC 3 kV was applied between the conductor and water for 500 days. This was sliced into thin pieces, dyed by boiling with an aqueous solution of methylene blue, and the presence or absence of votitley and the number (0.2 mm or more) were examined using an optical microscope. (2) Bloom of additive The surface of the electric wire after the completion of charging was visually observed and analyzed by the infrared absorption spectrum method to examine the precipitation of the additive. (3) Good or bad dielectric loss tangent After the completion of the above-mentioned voltage application, an alternating voltage of 3.8 kV, 50 Hz was applied at room temperature, and less than 0.1% was regarded as good.

[0017]

[Table 1]

As can be seen from Table 1, all of Examples 1 to 3 have good bowtight resistance, and
No bloom occurs. In contrast, Comparative Examples 1 and 2
Poor anti-bowtley resistance and precipitation of additives.

[0019]

As described above, according to the electric wire / cable of the present invention, the styrene / maleic anhydride copolymer is added to the polyethylene or ethylene copolymer, or a mixture thereof, with a maleic acid content of 0.02 to 0.02. Since the electrical insulating layer was composed of the resin composition blended so as to be 5 wt%, even if defects such as voids, foreign matters, and irregularities at the interface between the insulating material and the semiconductive layer exist in the insulating material, the generation of water trees is prevented. It can be suppressed and can provide excellent electrical insulation performance.

Front Page Continuation (72) Inventor Akifumi Katagai 5-1-1 Hidakacho, Hitachi City, Ibaraki Hitachi Power Systems Laboratory, Hitachi Cable, Ltd.

Claims (1)

[Claims] 1. An electric wire / cable in which an electric insulation layer is provided on the outer periphery of a conductor, wherein the electric insulation layer is a polyethylene or ethylene copolymer, or a mixture of styrene / maleic anhydride and maleic acid. An electric wire / cable comprising a resin composition blended so that the content is 0.02 to 5 wt%.