JPH0475602B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a power cable in which an insulating layer and a semiconducting layer have different colors to facilitate their identification. [Conventional technology] CV cable (cross-linked polyethylene power cable)
Power cables, such as the . [Problems to be Solved by the Invention] Incidentally, since the semiconductive layer of the above-mentioned conventional power cable is a mixture of rubber, plastic, and carbon black, it naturally appears black. Therefore, when the insulating layer is also black, it becomes difficult to distinguish between the insulating layer and the semiconducting layer, making it difficult to perform cable terminal processing and connection processing. Here, examples of the insulating layer exhibiting black color include crosslinked polyethylene mixed with carbon black. As previously proposed by the applicant, an insulator made by mixing 0.2 to 5.0% by weight of carbon black into cross-linked polyethylene is effective as an insulator for DC cables (Japanese Patent Application No.
091520, Japanese Patent Application No. 59-150299), if a black semiconductive layer is used in such a case, the above-mentioned problem will occur. This invention was made against this background, and by making the insulating layer and the semiconducting layer different colors, they can be easily distinguished, thereby improving workability. The purpose is to provide cables. [Means for Solving the Problems] In order to solve the above problems, the present invention provides that the insulating layer is made of cross-linked polyethylene mixed with carbon black, and the semiconductive layer is made of rubber and polyethylene mixed with conductive zinc white. /or plastic. Further, the amount of carbon black in the insulating layer is 0.2 to 5.0% by weight, and the amount of conductive zinc white in the semiconductive layer is 100 to 400 parts by weight. [Function] According to the above structure, while the insulating layer is black, the semiconducting layer is non-black, so they can be easily distinguished, and workability can be improved. [Examples] Examples of the present invention will be described below. First, the semiconducting mixture forming the inner semiconducting layer and/or the outer semiconducting layer, ie, rubber or plastic mixed with conductive zinc white, will be described. Conductive zinc white is made by doping zinc oxide with 0.01 to 5.0% aluminum oxide, mixing it in powder form, and firing it at high temperature in a reducing atmosphere. Then, 100 to 400 parts by weight of this conductive zinc white is mixed with a base polymer such as polyethylene, ethylene propylene rubber, or ethylene vinyl acetate copolymer to form a semiconductive mixture. In this case, if the amount of conductive zinc white added to the base polymer is less than 100 parts by weight, semiconductivity cannot be obtained.
If it exceeds 400 parts by weight, it becomes mechanically extremely brittle (see Japanese Patent Application No. 60-015124). Processing aids such as a crosslinking agent, anti-aging agent, and lubricant may be added to the semiconductive mixture as necessary. Further, although the original color of the semiconductive mixture containing conductive zinc white is grayish white, it can be colored into a desired color by adding an appropriate pigment. Next, use carbon black as the insulating layer.
It has already been mentioned that cross-linked polyethylene mixed with 0.2 to 5.0% by weight is used and that this exhibits a black color. The power cable according to this embodiment is effective for both AC and DC, but when used as a DC cable, the insulation layer is is composed of cross-linked polyethylene containing carbon black and general cross-linked polyethylene, and has a structure of conductor / inner semi-conductive layer / cross-linked polyethylene insulation layer containing carbon black (black) / cross-linked polyethylene insulation layer (white) / outer semi-conductive layer. Alternatively, it is also effective to configure the conductor/inner semiconducting layer/crosslinked polyethylene insulation layer (white)/crosslinked polyethylene insulation layer with carbon black (black)/outer semiconducting layer. Only the semiconductive layer in contact with the other layers may be a non-black semiconductive layer. [Experiment example] Cross-linked polyethylene mixed with 0.8% by weight of carbon black (SAF carbon) was used as the insulating layer, and ethylene-vinyl acetate copolymer (manufactured by Mitsui Polychemical Co., Ltd., Evaflex #260) 100 parts by weight, 200 parts by weight of conductive zinc white (manufactured by Hakusui Chemical Co., Ltd., conductive zinc white 23K), 1.2 parts by weight of dicumyl peroxide, and 0.2 parts by weight of anti-aging agent (manufactured by Monsanto Co., Ltd., Santonox R). A three-layer power cable with a conductor cross-sectional area of 200 mm ² and an insulating layer of 13 mm was created using a semiconducting mixture containing each of the following. For comparison, a power cable having the same structure as above and having a conventional semiconductive layer made of a semiconductive mixture containing carbon black was prepared.

[Table] Table 1 shows the results of DC breakdown voltage, polarity reversal breakdown voltage, and cable terminal processing workability for these power cables. As can be seen from this table, the product of the present invention greatly improves the workability of terminal processing without impairing the electrical properties (DC cable properties) due to the inclusion of carbon black in the insulator. [Effects of the Invention] As explained above, in this invention, the semiconductive layer is made of rubber or plastic mixed with conductive zinc white, and the semiconductive layer is made non-black. The layers can be easily identified. As a result, it is possible to improve the workability of voltage cable terminal processing and connection processing.

Claims (1)

[Scope of Claims] 1. A power cable in which an inner semiconducting layer, an insulating layer, and an outer semiconducting layer are sequentially provided around a conductor, wherein the insulating layer is made of crosslinked polyethylene mixed with carbon black; A power cable characterized in that the conductive layer is made of rubber and/or plastic mixed with conductive zinc white. 2 The amount of carbon black in the insulating layer is 0.2~
5.0% by weight, and the amount of conductive zinc white in the semiconductive layer is 100 to 400 parts by weight.