JPH07192542A - Water tree resistant cable - Google Patents

Abstract

PURPOSE:To manufacture a cable wherein water tree resistance is sharply improved by blending oxide or the derivative of the oxide with insulator layers when an inside semiconductive layer, an insulator layer, an outside semiconductive layer, and an outer sheath are formed in order onto a conductor to manufacture the cable. CONSTITUTION:A semiconductive polyethylene composition, wherein conductive carbon is blended with polyethylene, is extrusion-coated onto a copper stranded wire conductor 1 to provide an inside semiconductive layer 2. An insulative polyethylene composition, wherein agents, dicumi-peroxide, 4,4'-tio-bis(3- methyl-6-1-butyl phenol) and oxanilide, are blended with polyethylene, is exprusion-coated thereon to be heated and crosslinked to provide an insulator layer 3. Then a semiconductor polyethlene composition, same as a composition used in the inside semiconductor layer 2, is extrusion-coated thereon to form an outside semiconductor layer 4, and then a metal shield layer 5 composed of a soft copper wire braid and a sheath 6 by the extrusion of soft vinyl chloride resin are provided in order on the outside semiconductor layer 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable having improved water tree resistance.

[0002]

2. Description of the Related Art Conventionally, a crosslinked polyethylene insulated cable has been widely used as a high voltage power cable. This crosslinked polyethylene insulation cable is generally constructed by forming an inner semiconductive layer, a crosslinked polyethylene insulation layer, and an outer semiconductive layer on a conductor by three-layer coextrusion, and covering the outer circumference with a jacket. , High dielectric strength and high volume resistivity,
It has features such as low dielectric constant and low dielectric loss tangent.

However, in this type of cable, there is a problem that the electrical characteristics are greatly deteriorated when a water tree is generated, and improvement thereof is strongly demanded.

As a means for improving such water tree resistance, there is known a method of suppressing the mixing or influence of ionic impurities into the insulating layer, which is considered to be greatly involved in the generation and development of water trees, by using an additive. Has been.

[0005]

However, with the conventionally known additives, it is not possible to sufficiently prevent the mixing of ionic impurities into the insulating layer, or the effect thereof, so that the water tree resistance is greatly improved. I couldn't.

By the way, recently, there are various reasons that an electrolyte containing a metal such as copper or iron contained as an impurity in an insulating layer or a semiconductive layer or an electrolyte containing these metal cations is harmful to the generation and progress of a water tree. It has been revealed from the experiment. That is, metals such as copper and iron or their cations have a strong oxidation catalytic activity, and 4,4'-thio-bis (3-methyl-6-t-
It is considered that since the effect of an antioxidant such as butylphenol) is substantially reduced, oxidation of the insulator progresses, and this oxidation progresses to cause and progress a water tree. Therefore, if such a metal or metal cation can be prevented from being mixed into the insulator, or if its action can be suppressed even when mixed, the oxidation of the insulator can be reduced and the water tree resistance can be improved. It is thought to be possible.

The present invention has been made on the basis of the above findings, and the metal or metal cation is mixed into the insulating layer, or the oxidation catalyst ability thereof is reduced, and the water tree resistance is greatly improved. The purpose is to provide a cable.

[0008]

A water resistant tree cable according to the present invention is a cable in which an inner semiconductive layer, an insulator layer, an outer semiconductive layer, and an outer cover are sequentially formed on a conductor. It is characterized in that the body layer is blended with oxamide or a derivative thereof.

Examples of the oxamide derivative include oxanilide.

In the present invention, other known metal deactivators may be used in combination with oxamide or a derivative thereof,
As such a metal deactivator, it is desirable to use a metal deactivator that forms a stable complex with a metal having a strong oxidation catalytic activity in the insulator with which it is blended. For example, the insulator
In the case of polyethylene or polypropylene blended with an antioxidant, or a polyolefin such as a cross-linked product thereof, amine-based ones such as triazole, substituted hydrazides such as oxalyl dihydrazide and m-nitrobenzhydrazide are preferably used. It That is, metals such as iron and copper have a strong oxidation catalytic activity for polyolefins, but oxamide and its derivatives form stable complexes with these metals. And the metal such as iron and copper complexed in this way has a large decrease in its oxidation catalytic ability, and as a result, the oxidation of the insulator is suppressed,
The generation and development of water trees due to this oxidation are prevented,
It is thought that the water resistance of the cable can be improved. Then, such an effect can be further enhanced by the combined use of oxamide or a derivative thereof and a metal deactivator such as triazole. The amount of oxamide or its derivative, or the metal deactivator used in combination with the oxamide, depends on the base insulating material.
About 0.01 to 0.5% by weight is suitable.

In the present invention, the metal deactivator is
Not only the insulator layer but also the inner semiconductive layer or the outer semiconductive layer may be blended. The water tree resistance of the cable can be further improved by suppressing the mixture or influence of the metal or metal cation contained in each of these layers on the insulator layer.

[0012]

In the water resistant tree cable of the present invention, the oxamide or its derivative compounded in the insulator layer forms a complex with the metal or metal cation mixed as an impurity in the insulator layer to oxidize itself. Since the catalytic activity is substantially reduced, oxidative deterioration of the insulating layer is suppressed, and the water tree resistance is significantly improved.

[0013]

Embodiments of the present invention shown in the drawings will be described below.

EXAMPLE 1 As shown in FIG. 1, a copper stranded wire conductor 1 having a cross-sectional area of 150 mm ² was extrusion-coated with a semiconductive polyethylene composition prepared by mixing polyethylene with 37% by weight of conductive carbon. An internal semiconductive layer 2 with a thickness of 1 mm is provided, and polyethylene
1.6% by weight of the cross-linking agent dicumyl peroxide (DC
P), 0.18% by weight of 4,4'-thio-bis (3-methyl-6-t
-Butylphenol) and 0.18% by weight of oxanilide were mixed by extrusion coating and heat-crosslinked to provide a 6 mm thick insulator layer 3. Then
The same semiconductive polyethylene composition as that used in the inner semiconductive layer 2 was extrusion coated thereon to form an outer semiconductive layer 4 having a thickness of 0.5 mm, and then an annealed copper wire braid was formed thereon. Metal shielding layer 5, 3mm by extrusion of soft vinyl chloride resin
The thick sheath 6 was provided in order.

The water resistance of the obtained crosslinked polyethylene cable was evaluated. That is, the outer cover 7 is partly removed and immersed in a water tank, and the inundation electricity is applied under the conditions of 13 kV and 1 kHz for one month, and the occurrence rate of each of the inner conducting tree, the outer conducting tree, and the bow-tie tree is increased. I checked. The results are shown in Table 1.

Example 2 Polyethylene was used as a semiconductive polyethylene composition.
A mixture of conductive carbon of 0.5% by weight and oxamide of 0.5% by weight is used, and as an insulating polyethylene composition, 1.6% by weight of polyethylene and 0.18% by weight of DCP are used.
A crosslinked polyethylene cable was obtained in the same manner as in Example 1 except that 4,4'-thio-bis (3-methyl-6-t-butylphenol) and 0.17% by weight of oxamide were used. The water tree resistance was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 3 As an insulating polyethylene composition, 1.6 parts of polyethylene were used.
Wt% DCP, 0.18 wt% 4,4'-thio-bis (3-
Methyl-6-t-butylphenol), 0.1 wt% oxamide and 0.08 wt% 1,2,4-triazole oxamide were used in the same manner as in Example 1, except that a crosslinked polyethylene cable was used. Then, the water tree resistance was evaluated in the same manner as in Example 1. The results are shown in Table 1.

For comparison, a cross-linked polyethylene cable having a conventional structure manufactured in the same manner as in the above-mentioned example except that oxanilide was not blended was subjected to the same flooding voltage application test as in the example. Also shown in Table 1.

[0019]

[Table 1]

[0020]

As is clear from the above examples, according to the water resistant tree cable of the present invention, oxamide or a derivative thereof is mixed in the insulating layer, so that it is mixed as an impurity in the insulating layer. It is possible to suppress the contact oxidation due to the existing metal or metal cation, to suppress the generation and progress of the water tree due to the progress of oxidation, and to improve the water tree resistance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a water resistant tree cable according to an embodiment of the present invention.

[Explanation of symbols]

 1 ... Copper stranded conductor 2 ... Inner semiconductive layer 3 ... Insulator layer containing metal deactivator 4 ... Outer semiconductive layer 5 ... Metal shielding layer 6 ... …sheath

Claims (1)

[Claims] 1. A cable in which an inner semiconductive layer, an insulator layer, an outer semiconductive layer, and a jacket are sequentially formed on a conductor, wherein the insulator layer contains oxamide or a derivative thereof. A water resistant tree cable that features.