JP2008017569A - Intermediate joint for power cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive and reliable intermediate joint for power cable which prevents the deterioration of electric properties caused by discharging, by arranging a constitution so that an air gap may be not formed between the outer face of a cable joint and the inner face of a rubber block insulating tube as much as possible. <P>SOLUTION: This intermediate joint is so provided with an insulating layer 7 as to flatten an unevenness part which has been formed among a joint 8 for conductors which are exposed by stripping ends of power cables 1 in tiers, the exposed conductors 2, and ends of cable insulators 3. A rubber block insulating tube 20 composed of a plurality of layers excluding an internal semiconductor layer is tightly stuck to the top of them, and mounted. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an intermediate connection portion of a power cable.

Conventionally, as a joint member for connecting a plastic insulated power cable or the like, a three-layer structure pre-molded rubber insulating cylinder composed of an inner semiconductive layer, an insulating layer, and an outer semiconductive layer is known.
This three-layered pre-molded rubber insulation cylinder has an internal semiconductive layer, an insulating layer, and an external semiconductive layer that are integrally molded, so that it is easy to handle during installation and has good workability. Although it has been widely used because of its excellent performance, in the production of a rubber insulating cylinder, a mold for molding is required for each layer, which has a problem that it takes too many manufacturing steps and costs.

  For this reason, a pre-mode rubber insulation cylinder has been proposed in which the inner semiconductive layer in the three-layer structure is omitted, and the cost is reduced as a two-layer structure of an insulating layer and an outer semiconductive layer. (Patent Document 1).

However, this pre-mode rubber insulation cylinder having a two-layer structure is appropriately mounted on a cable connecting portion (a portion including a portion where a cable insulating layer is subjected to a penciling process from a portion where cable conductors are connected to each other. The same applies hereinafter). Otherwise, a void is likely to occur between the outer surface of the cable connection part and the inner surface of the insulating cylinder, and if the gap is generated, a discharge occurs during power application and the electrical characteristics of the rubber insulating cylinder deteriorate. There was a problem. For this reason, the connection work of the power cable requires technical skill and the work is complicated.
JP 2003-125527 A

  The present invention has been made in view of such problems, and is inexpensive, in which a gap is not generated as much as possible between the outer surface of the cable connection portion and the inner surface of the rubber block insulating cylinder, thereby preventing deterioration of electrical characteristics due to discharge. The purpose is to provide an intermediate connection part of a highly reliable power cable.

  That is, according to the first aspect of the present invention, the projecting recesses formed between the exposed portions of the conductors, the exposed conductors, and the ends of the cable insulators are filled in by stripping the ends of the power cable. An insulating material layer is provided as described above, and a rubber block insulating cylinder composed of a plurality of layers excluding the internal semiconductor layer is mounted thereon.

  According to a second aspect of the present invention, in the intermediate connection portion of the electric power cable according to the first aspect, the rubber block insulating cylinder has a two-layer structure of an inner insulating layer and an outer outer semiconductive layer. It is characterized by comprising.

  According to a third aspect of the present invention, in the intermediate connection portion of the power cable according to the second aspect, a high dielectric constant layer having a dielectric constant larger than that of the insulating layer is provided inside the insulating layer. It is said.

  According to a fourth aspect of the present invention, in the intermediate connection portion of the power cable according to any one of the first to third aspects, a self-bonding material is used as the insulating material layer. It is said.

  According to invention of Claim 1, 2, an insulating material layer is provided so that the unevenness between the conductor connection part of an electric power cable, an exposed conductor, and the cable insulation edge part of the both sides may be provided, and rubber | gum may be provided on it. Since the block insulating cylinder is mounted, the rubber block insulating cylinder can be mounted so as not to cause a large gap between the outer surface of the cable connecting portion and the inner surface of the insulating cylinder without technical skill. Therefore, even if a rubber block insulating cylinder having no internal semiconductive layer is used, it is possible to prevent a decrease in electrical characteristics due to discharge caused by the gap. Thereby, an inexpensive and highly reliable intermediate connection part can be realized.

  According to the third aspect of the present invention, since the high dielectric constant layer is provided inside the insulating layer, the electric field in the length direction at the intermediate connection portion (interface between the cable insulator and the insulating layer) is relaxed. Since it can be in a substantially uniform state, the electrical insulation performance of the insulating layer can be improved.

  Further, according to the present invention, since the self-bonding material having high affinity with the rubber block insulating cylinder is used as the insulating material layer, the adhesion between the insulating material layer and the rubber block insulating cylinder. And the generation of voids can be more reliably prevented, and the electrical insulation characteristics are improved.

  Hereinafter, based on FIGS. 1-4, embodiment of the intermediate connection part of the power cable which concerns on this invention is described.

  FIG. 1 shows an intermediate connection part of a power cable according to a first embodiment of the present invention. According to the present embodiment, as shown in FIG. 1, the ends of the two power cables 1 and 1 to be connected are stepped, and the conductor 2, the cable insulator 3, the cable outer conductive layer 4 and the like are stepped. The exposed end portions of the conductor 2 are brought into contact with each other, and the butted portion is connected by pressure bonding or compression using a conductor connecting tube 9 (metal sleeve), whereby the conductor connecting portion 8 is connected. Is formed. In the present embodiment, the end portion of the cable insulator 3 is tapered to form the penciling portion 3a.

An insulating material layer 7 is provided around a portion (cable connecting portion) extending from the conductor connecting portion 8 to the penciling portion 3a of the cable insulator 3 on both sides thereof, and the insulating material layer 7 and the cables on both sides thereof. A rubber block insulating cylinder 20 having a two-layer structure composed of an inner insulating layer 11 and an outer outer semiconductive layer 12 is formed on the outer periphery of the outer insulating layer 11 so as to cover the insulator 3 and straddle the cable outer conductive layer 4. The intermediate connection portion 10 is configured in a close contact state.
The rubber block insulating cylinder 20 is excellent in insulation and workability. For example, the insulating layer 11 and the outer semiconductive layer 12 made of, for example, silicone rubber, ethylene propylene rubber or the like are integrally formed by molding. In order to alleviate the electric field (electric field gradient) in the length direction, both side portions of the insulating layer 11 and the outer semiconductive layer 12 are tapered.

Here, as the material of the insulating material layer 7, polyethylene, butyl rubber, ethylene propylene rubber, chloroprene rubber, silicone rubber or the like can be used. Specifically, the above-mentioned insulating material is taped and wound around a necessary portion, or putty is filled into the necessary portion.
Further, by using a self-bonding material as the insulating material layer 7, the generation of voids can be prevented more reliably, and the electrical insulation characteristics can be further improved.

The insulating material layer 7 is formed on the conductor connecting tube 9, the exposed portion of the conductor 2, and the cable insulator 3, and in the cable insulator 3, the entire penciling portion 3a or its It may be formed so as to reach a part of the connecting pipe 9 side or the cable insulator 3 including the penciling portion 3a.
In any case, it is important that the insulating material layer 7 is provided so as to fill the convex and concave portions caused by the differences in the outer diameters of the conductor connecting tube 9, the conductor 2, and the cable insulator 3.
The outer diameter of the surface of the insulating material layer 7 is the same as or larger than the outer diameter of the cable insulator 3 at the time of construction.

After the insulating material layer 7 is thus provided, the rubber block insulating cylinder 20 is attached.
The rubber block insulating cylinder 20 may be a room temperature shrinkable rubber block insulating cylinder 20 shown in FIG.
This is supplied in a state in which the diameter is expanded by the removable diameter-expanding core member 30, and the process of forming the insulating material layer 7 as described above by passing the cable 1 through the core member 30 before connection. After that, the insulating cylinder 20 is moved to the location of the insulating material layer 7 and then the diameter-expanded core member 30 is removed to reduce the diameter of the insulating cylinder 20 and attach it to the connection location of the cable.
Thereby, without requiring technical skill, the insulating layer 11 of the rubber block insulating cylinder 20 and the cable connecting portion (in particular, the insulating material layer 7 on the conductor connecting portion 8) can be brought into close contact with each other. Generation of large voids can be prevented.

  As a result, even when the rubber block insulating cylinder 20 without the internal semiconductive layer is used, it is possible to prevent the occurrence of discharge due to the air gap, to prevent the electrical characteristics from being deteriorated by the discharge, and to be inexpensive and reliable. A high intermediate connection 10 can be realized.

Next, FIGS. 3 to 5 show an intermediate connection portion of a power cable according to a second embodiment of the present invention.
As in FIG. 1, the intermediate connection portion 10 of the present embodiment uses a rubber block insulating cylinder 20 having a two-layer structure composed of an inner insulating layer 11 and an outer outer semiconductive layer 12, and this insulating layer. 11 has a structure in which a high dielectric constant layer 13 is provided inside. The high dielectric constant layer 13 can be made of, for example, a rubber-based insulator or a material having electrical insulation obtained by adding carbon to a plastic resin, and has a higher dielectric constant than that of the insulating layer 11.

  In this embodiment, FIG. 3 shows a configuration example in which the high dielectric constant layer 13 is provided on both side portions of the insulating layer 11 (portions other than the portion where the insulating material layer 7 is formed), and FIG. 4 shows the length direction of the insulating layer 11. FIG. 5 shows a configuration example in which the high dielectric constant layer 13 is provided with a substantially constant thickness on the entire surface, and FIG. 5 shows a configuration in which the high dielectric constant layer 13 is provided on the entire length of the insulating layer 11. This is a configuration example in which the thickness of the (formed part) is formed thinner than both side parts.

  Thus, by providing the high dielectric constant layer 13 inside the insulating layer 11, the electric field strength in the cable length direction at the interface between the cable insulator 3 and the insulating layer 11 is particularly relaxed, and the electric field is lengthened. It is possible to obtain a substantially uniform state in the direction, and the electrical insulation performance of the insulating layer 11 can be improved. The electrical insulation performance at the center in the length direction of the insulating layer 11 is guaranteed by the formation of the insulating material layer 7.

  With such a structure, the thickness of the insulating layer 11 can be reduced compared to the rubber block insulating cylinder 20 shown in FIG. 1, and the shapes on both sides thereof do not have to be complicated tapered shapes. Thus, the required electrical insulation performance can be obtained even with a simple cylindrical shape. In addition, the structure of the manufacturing mold can be simplified, and the cost can be reduced.

The front sectional view showing the middle connection part of the electric power cable by a 1st embodiment of the present invention. Sectional drawing which shows the normal temperature shrinkable rubber block insulation cylinder used for the intermediate connection part of FIG. The front sectional view which shows the intermediate connection part of the electric power cable by 2nd Embodiment of this invention. The front sectional view which shows the intermediate | middle connection part different from FIG. 3 of the power cable by 2nd Embodiment of this invention. Sectional drawing which shows the intermediate | middle connection part different from FIG. 4 of the power cable by 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power cable 2 Conductor 3 Cable insulator 7 Insulation material layer 8 Conductor connection part 10 Intermediate connection part 11 Insulation layer 12 External semiconductive layer 13 High dielectric constant layer 20 Rubber block insulation cylinder

Claims (4)

An insulating material layer is provided so as to fill in the concave and convex portions formed between the exposed conductors and the ends of the cable insulators by stripping the ends of the power cable, and on top of these. An intermediate connection portion of a power cable, characterized in that a rubber block insulating cylinder consisting of a plurality of layers excluding the internal semiconductor layer is attached. The intermediate connection portion of the power cable according to claim 1, wherein the rubber block insulating cylinder has a two-layer structure of an inner insulating layer and an outer outer semiconductive layer. The intermediate connection part of the power cable according to claim 2, wherein a high dielectric constant layer having a dielectric constant larger than that of the insulating layer is provided inside the insulating layer. The intermediate connection part of the power cable according to any one of claims 1 to 3, wherein a self-bonding material is used as the insulating material layer.

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