JPS6035934Y2 - Rubber/plastic insulated power cable - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a rubber/plastic insulated cable with significantly improved dielectric breakdown strength.

Conventional rubber/plastic insulation type capacitors have semiconducting layers formed inside or on the inside and outside of the insulating layer for the purpose of relaxing the electric field on the conductor.

Among these semiconducting layers, if the internal semiconducting layer has a particularly high electric field, and there is a protrusion on its surface, the electric field strength at the tip of the protrusion will be significantly larger than on the surface of other semiconducting layers, and an electric tree will be generated from this tip. This can easily lead to insulation breakdown of the cable.

However, in practice, protrusions caused by impurities in the conductive carbon black or extrusion work were often observed on the surface of the internal semiconductive layer of actual rubber/plastic insulated capacitors.

The present invention was developed as a result of intensive studies to improve the above-mentioned drawbacks of rubber/plastic insulated capacles.The present invention was developed by adding dibenzylidene-D-sorbitol (hereinafter referred to as D
By forming a plastic resin layer containing BS (abbreviated as BS), even if there are protrusions on the semiconducting layer, it is possible to prevent the generation of electrical trees from the tips, and the cable insulation breakdown characteristics are significantly improved. This is what I discovered.

That is, the present invention, for example, as shown in the cross-sectional view of an embodiment of FIG.
This is a rubber/plastic, insulating capeple with a structure in which an outer semiconductive layer 5 and a protective sheath layer 6 are extruded and coated in order, and by adding DBS to the semiconductive layer, crystals in the plastic resin grow and the density is increased. , is characterized by forming a plastic resin layer with high voltage resistance characteristics.

The reason why we limited the base resin to which DBS is added in this invention to plastic resin is that even if DBS of a resin other than plastic is added, the crystalline substance in the resin cannot be grown and the treeing resistance property is improved. This is because it cannot be done.

In this invention, the rubber/plastic resin used for the insulating layer includes elastomers such as butyl rubber, ethylene propylene rubber, and chloroprene rubber, and low-density and high-density polyethylene.
Refers to thermoplastic plastics such as polypropylene, polyisobutylene, ethylene vinyl acetate copolymer, chlorinated polyethylene, and polyvinyl chloride.

Further, a crosslinking agent such as dicumyl peroxide, an anti-aging agent, etc. may be added to these insulating layers as necessary.

Note that the plastic resin layer to which DBS is added may also be used as it is as an insulator layer.

Experimental Example An experiment on the treeing resistance of a plastic resin containing DBS of the present invention was carried out as follows.

As shown in FIG. 2, a tongue piece 7 (hereinafter referred to as a semiconductive tongue piece) molded from a semiconductive composition having protrusions with a radius of curvature of 10 μm is made of polyethylene having a width of 2 and a height of 4 as shown in Table 1. The molded body was embedded in a molded body 8, and a conductive paint was applied to the bottom surface of the molded body.

Thereafter, A and C voltages of 4QKV were applied between the semiconductive tongue and the conductive paint, and the state of tree generation after 100 Ctf was investigated.

The results are shown in Table 1.

In the table, polyethylene has Ml=1.0. Low density polyethylene with density=0.92 was used.

The density of Assemble Example 3 without DBS added is the density directly above the semiconductive tongue.

Example 1 After providing an internal semiconductive layer by extrusion coating of semiconductive polyethylene with a thickness of 1 rrrIn on the outer periphery of a conductor with a conductor size of 250-, ITI was coated on the outer periphery with the composition of Composition Example 1 in Table 1.
I! 66KV cross-linked polyethylene insulating shell with n-thick tree-resistant 477 layer, 1-thick cross-linked polyethylene insulation layer, 1771771-thick outer semiconductive layer of semiconductive polyethylene composition, copper tape shielding layer, and PVC sheath. - Made a pull.

For comparison, a cross-linked polyethylene insulated capeple having the same structure was made except that the tree-resistant 477 layer was not provided and the cross-linked polyethylene insulator layer was 1177Ell+.

Two samples of each of the cables thus obtained were tested for electrical characteristics.

The results are shown in Table 2.

As is clear from the results in Table 2, DBS is applied to the outside of the semiconducting layer.
The fracture characteristics of the cross-linked polyethylene insulated capeple of the present invention, which is provided with a plastic layer containing , have been significantly improved compared to conventional products.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a cable according to an embodiment of the present invention. FIG. 2 is a perspective view showing a method for evaluating treeing resistance. 1... Conductor, 2... Internal semiconducting layer 3
...Plastic resin layer added with DBS, 4
...Rubber or plastic insulator layer, 5...
...Outer semiconducting layer, 6...Protective sheath layer, 7
・・・・・・Semi-conductive tongue piece, butt ・・・Polyethylene shape body, 9・・・・・・Conductive paint layer, 10...
...High voltage power supply.

Claims (1)

[Scope of utility model registration request] A rubber/plastic insulating capeple characterized in that a plastic resin layer containing dibenzylidene-D-sorbitol is formed directly above a semiconductive layer provided on the outside of a conductor.