JPS60165004A - 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 (Technical Field of the Invention) The present invention relates to improvements in electric power cables, and particularly to electric power cables that prevent increases in dielectric loss tangent after long-term heat cycles.

(Technical background of the invention and its problems) Conventionally, electric power cables using cross-linked polyethylene or cross-linked ethylene propylene rubber for the insulating layer have been used. 102 to 103 Ω- directly above the insulating layer.
A semiconducting layer is provided which has a volume resistivity of cm.

In such a cable structure, due to the heat cycle history during long-term actual use, the insulating core shrinks and a small gap is created between the outer semiconducting layer and the shielding copper tape, causing dielectric loss due to increased leakage current. It had the disadvantage that an increase in tangent was observed.

(Object of the Invention) The present invention was made in view of the above circumstances, and its purpose is to suppress the increase in dielectric loss tangent due to thermal contraction after a long heat cycle, and to improve its durability. The purpose is to provide electric power cables.

(Summary of the Invention) The present invention is characterized in that a semiconducting layer and a conductive layer having a volume resistivity of 10 Ω or less and a contact resistance of 10 Ω or less are provided in close contact with each other on a cable insulating layer.

The present invention will be explained below based on the drawings.

In FIG. 1, an electric power cable 1 has an internal semiconductive layer 3 and an insulating layer 4 made of, for example, a conductivity imparting agent, a polymer such as polyethylene ethylene vinyl acetate copolymer, and chlorinated polyethylene, which are sequentially provided on the outer periphery of a conductor 2. It has a unique structure. The insulating layer 4 is made of cross-linked polyethylene or cross-linked ethylene,
It is formed of a propylene copolymer or the like, and an outer semiconducting layer 5 is provided directly above the insulating layer 4, and is often formed of the same composition as the inner semiconducting layer 3, but has a different semiconducting composition. It may be a thing.

Furthermore, a conductive layer 5 is provided outside the external semiconductive layer 5, and this conductive layer 6 has a volume resistivity of 10Ω or less and a value of 10Ω.
It has the following contact resistance. The reason why the upper limits of the volume resistivity and contact resistance of the conductive layer are defined here is that if these limits are exceeded, there is no effect in preventing an increase in the dielectric loss tangent after a long heat cycle.

Further, the conductive layer is made of a conductivity imparting agent and a polymer, and examples of the conductivity imparting agent include metal powder and carbon black. Here, if the conductivity imparting agent is contained in an amount of 80% by weight or more, 1
A specific resistance of 0Ω or less can be maintained, and if the number of folds is less than 80, the polymer tends to swell and deteriorate due to heat during use of the cable, resulting in an increase in contact resistance and an increase in dielectric loss tangent.

As a method for manufacturing the power cable 1 of the present invention, for example, after coating the conductor 2 with an internal semiconductive layer 3, an insulating layer 4, and an external semiconductive layer 5 by extrusion in sequence or simultaneously, a conductive paint is applied, and the conductive material is coated with a conductive paint. Layer 6 can be formed.

(Example of the invention) Examples will be described below.

[Examples 1 and 2] Electric power cables were manufactured with the configuration shown in the table on a conductor having a nominal cross-sectional area of 250 mm.

Cable heat cycle test obtained in this way (conditions: conductor current 90°C 8 hours switch 0N - 16 hours 0FF)
) The value of the dielectric loss tangent after the test is shown in Fig. 2.

[Conventional Examples 1 to 3] Of the structures of the examples, power cables having no conductive layer were tested in the same manner as in the examples, and the results are shown in FIG.

(*Product name manufactured by Aheson Colloid, Inc., USA. Conductive carbon black is kneaded with ammonia water to form a paste (effects of the invention) As is clear from the examples of the present invention, the power cable of the present invention has the following properties: No increase in dielectric loss tangent is observed after a long heat cycle.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the electric power cable of the present invention, and FIG. 2 is a graph showing the values of dielectric loss tangents after heat cycles for the present invention and the conventional example. 2----------Conductor 4--Insulating layer 5--Outer semiconducting layer 6--
---One conductive layer

Claims (1)

[Claims] 1. A power table comprising a semi-conductive layer and a conductive layer having a volume resistivity of 10 Ω or less and a contact resistance of 10 Ω or less, each closely spaced on a cable insulating layer □. 2. The power cable according to claim 1, wherein the conductive layer comprises a conductivity imparting agent weighing 80% by weight or more and a polymer.