JPH02297807A - Plastic-insulated power cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a plastic insulated cable, and more particularly to a plastic insulated cable with excellent water resistance.

(Prior technology) Rubber/plastic insulated cables are
It has a structure in which an inner semiconducting layer, an insulator, and an outer semiconducting layer are sequentially formed, a metal shielding layer is applied on top of this, and a sheath layer for corrosion prevention and protection is formed on top of that.

In this structure, the inner semiconducting layer and the outer semiconducting layer are provided to realize electric field relaxation during operation of the power cable and to improve or stabilize the insulation performance of the insulator.

These semiconductive layers are generally made of a semiconductive resin composition in which a predetermined amount of carbon black is uniformly dispersed in a base resin such as ethylene acrylic acid copolymer or ethylene acetate beer copolymer. It is formed by extrusion coating on a conductor or insulator.

(Plot 1!l) By the way, when an electric cable with the above structure is operated under water, water trees are generated from the inner semiconducting layer and the outer semiconducting layer, which impairs the electrical performance of the cable. significantly decreases.

It is known that this water tree originates from protrusions generated on the surface of the semiconductive layer when the semiconductive layer is formed by extrusion coating. Therefore, with the aim of preventing the occurrence of these protrusions, research has been carried out on measures such as improving the resin composition of the semiconductive layer and improving the extrusion coating method of the semiconductive layer.

However, water tree is not only caused by the presence of the above-mentioned protrusions on the surface of the semiconducting layer, but also metal ions from various metal impurities contained in the resin composition of the semiconducting layer. This is also caused by seepage on the surface of the oxide, that is, the contact interface between the inner and outer semiconducting layers and the insulator. However, to date, no measures have been taken to solve the above causes.

An object of the present invention is to provide a plastic insulated capacitor that has excellent water tree resistance by preventing water trees from occurring due to metal ions exuding from a semiconductive layer.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, the inner semiconducting layer and/or the outer semiconducting layer contain 100 parts by weight of ethylene copolymer and 10 to 80 parts by weight of carbon black. A plastic insulating capeple is provided, characterized in that it is made of a semiconducting resin composition containing 0.05 to 10 parts by weight of a metal deactivator as a main component.

The electrical cable of the present invention is characterized by the semiconductive resin composition that constitutes the inner and outer semiconductive layers, and other elements are the same as in the conventional case.

Examples of the ethylene copolymer that is the base of this resin composition include ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, ethylene propylene copolymer rubber, low density polyethylene, and linear low density polyethylene. Each of them can be used alone or in a mixture of two or more kinds.

Carbon black is a component for imparting semiconductivity to the resin composition, and includes, for example, acetylene black, furnace black, Ketjen black, and the like.

The blending amount of carbon black is set to 10 to 80 parts by weight based on 100 parts by weight of the above-mentioned ethylene copolymer.

If it is less than 10 parts by weight, it will not be possible to impart proper semiconductivity to the resin composition, and if it exceeds 80 parts by weight, the viscosity of the composition will increase, making it unsuitable for extrusion molding. . The preferred blending amount is ethylene copolymer 100
The amount is 20 to 60 parts by weight.

A metal deactivator is a component that diffuses from a semiconducting layer into an insulator and forms a chelate bond with the metal ions in the insulator, thereby inactivating the metal ions and suppressing the occurrence of water trees. , for example, N, N'-bis(3
Compounds such as -(3,5-di-L-butyl-4-hydroxyphenyl)propionyl]hydrazine, 8-hydroxyquinoline, benzotriazole, and tolyltriazole can be mentioned.

The amount of this metal deactivator is 100% of the ethylene copolymer.
It is set at 0.05 to 10 parts by weight.
If the amount is less than 0.05 parts by weight, the amount of diffusion from the semiconducting resin composition will be reduced, making it impossible to effectively suppress the occurrence of water trees, and if it exceeds 10 parts by weight, the insulator This is because the amount of dielectric particles diffused into the cable becomes too large, leading to a deterioration of the dielectric properties of the cable. The preferred amount is 0.1 to 5 parts by weight per 100 parts by weight of the ethylene copolymer.

The resin composition constituting the inner and outer semiconductive layers mainly contains the above three components, but in order to improve processability during extrusion coating, a known lubricant is further added.

There is no problem in adding appropriate amounts of antioxidants, plasticizers, etc.

In addition, when extrusion coating is performed and then crosslinked, an appropriate amount of peroxide or the like may be further mixed in addition to the above components and heated or irradiated with electron beams.

(Function) In the electric caple of the present invention, the blended metal deactivator diffuses from the semiconducting layer to the insulator, and at the interface between the two, metal ions that have also exuded from the semiconducting layer are captured by a chelate reaction. .

As a result, the occurrence of water trees due to the presence of metal ions is suppressed.

(Embodiments of the invention) Examples 1 to 4. Comparative Examples 1 to 3 Semiconductive resin compositions having the compositions shown in Table 1 were prepared. This is extruded and coated to form an internal semiconductive layer with a thickness of 0.6 wa on the conductor, and a cross-linked polyethylene layer on top of the internal semiconductive layer with a thickness of 1 wa.
An electric cable was manufactured by sequentially forming an insulator having a thickness of m and an outer semiconductor layer having a thickness of 0.5II11 thereon.

These cables are placed in water at 70°C and have a voltage of 6kV.

After applying electricity for one year under the condition of 1 kHz, the loss of water trees generated in the internal semiconductive layer and the external semiconductive layer was measured to calculate the number of generated water trees per 1 m of length, and also to calculate the tan
The results of measuring δ of 0 or more are collectively shown in Table 1.

(The following is a blank space) (Effects of the Invention) As is clear from the above explanation, the electric cable of the present invention has significantly superior water resistance compared to the conventional one (Comparative Example 1). This effect is due to the fact that the metal deactivator is contained in the inner and outer semiconductive layers.

Claims (1)

[Claims] A semiconducting resin composition in which the inner semiconducting layer and/or the outer semiconducting layer mainly contains 100 parts by weight of an ethylene copolymer, 10 to 80 parts by weight of carbon black, and 0.05 to 10 parts by weight of a metal deactivator. A plastic insulated power cable comprising: