JPH07272551A - Cable with arrester - Google Patents

Abstract

PURPOSE:To make a lightning arrester compact. CONSTITUTION:A varistor 4 is put between an insulating layer 3 of a CV cable 1 and a sheath 5 and at the same time the varistor 4 is connected with the ground 7 through a metal shielding layer 6. Consequently, it is no need to install a lightning arrestor unit separately and keep a space for installation of an arrestor. Since the function as an arrestor can be conducted only by connecting a metal shielding layer 6 with the ground 7, the lightning arrestor can be composed easily. Furthermore, the insulation between the conductor 2 and the sheath 5 can be kept surely by the varistor 4 even if the insulating layer 3 is deteriorated with the passage of time or the original insulating function is lost due to discharge destruction by foreign substance invasion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable with a lightning protection device for protecting the cable from lightning surge.

[0002]

2. Description of the Related Art Conventionally, as a device for protecting a cable from a lightning surge, there is a lightning arrester shown in FIG. In this lightning protection device, a lightning protection unit 31 having a varistor 32 built therein is attached to the outside of a cable 34. This lightning protection device is arranged at a predetermined distance from the installed cable 34. As shown in FIG. 6, the conductor 35 forming the cable 34 is covered with an insulating layer 36 made of polyethylene or the like. Further, the surface of the insulating layer 36 is covered with a sheath 37 made of an insulating material such as vinyl. Then, the varistor 32 of the lightning protection unit 31 is connected to the cable 34.
Of the conductor 35.

When a lightning surge enters the cable 34, the surge current flows through the conductor 35, passes through the varistor 32 from the charging side electrode, and is discharged to the ground 39. This allows
The voltage rise of the cable 34 due to the lightning surge is suppressed, and the follow current is cut off.

[0004]

However, in the lightning protection device, the lightning protection unit 3 is provided separately from the insulator body 31.
Since 1 is provided, the device becomes large and it is difficult to secure the installation space. Also, the lightning protection unit 3
Since 1 is a separate body from the insulator main body 31, there is a problem that mounting workability deteriorates.

Further, since the cable 34 has a long overall length, the cable 34 having a predetermined length is connected and extended on site. When the cable 34 is connected, foreign matter may enter the insulating layer 36, especially from the joint of the cable 34. When foreign matter is mixed into the insulating layer 36, void discharge occurs. The insulating layer 36 is gradually deteriorated by the discharge, and the insulating layer 36 is destroyed. And
When the insulating layer 36 is completely destroyed, the conductor 35 and the sheath 37
A short circuit will occur between and, causing a problem.

The present invention has been made to solve the above problems, and a first object of the present invention is to provide a cable with a lightning arrester capable of reducing the size of the lightning arrester and improving its mounting workability. .

A second object of the present invention is to provide a cable with a lightning arrester capable of surely insulating the conductor and the sheath.

[0008]

Means for Solving the Problems In order to achieve the above object, according to claim 1, a flexible sheet-shaped varistor is wound around a cable and the varistor is connected to a ground. To do.

The gist of the second aspect is that the varistor is wound around the outer circumference of the joint of the cable. In the third aspect, the gist of the varistor is to surround the conductor of the cable.

According to the present invention, in a cable in which the conductor is covered with an insulating layer and the insulating layer is covered with a sheath, the insulating layer is covered with a flexible sheet-shaped varistor. Is the gist.

The gist of the fifth aspect is that the varistor is connected to the ground.

[0012]

According to the first aspect, when a lightning surge enters the cable, the surge current flows from the cable to the ground through the varistor. As a result, the voltage rise of the cable due to the lightning surge is suppressed and the follow current is cut off. As described above, according to the first aspect, since the lightning protection device is configured by directly winding the flexible sheet-shaped varistor around the cable, the device can be downsized and the workability of attaching to the cable can be improved. In addition, since the lightning arrester has a small number of parts, it is easy to assemble and the cost is reduced.

According to the second aspect of the present invention, the varistor is wound around the outer circumference of the joint of the cable where foreign matter is easily mixed, so that the conductor and the sheath are reliably insulated even if the insulating layer is broken.

According to the third aspect, the varistor normally acts as an insulating layer for insulating between the conductor of the cable and the sheath. In addition, it acts as a lightning protection device in the event of an abnormality (when a lightning strike).

According to the fourth aspect, the conductor is double-coated with the insulating layer and the varistor, so that the varistor insulates the conductor and the sheath even if the insulating layer deteriorates. According to the fifth aspect, when lightning strikes the cable, the lightning surge current flows through the insulating layer to the varistor and is discharged to the ground.

[0016]

【Example】

First Embodiment Hereinafter, a first embodiment embodying the present invention will be described with reference to FIGS.

As shown in FIG. 1, the conductor 2 of the CV cable 1 is covered with an insulating layer 3 made of polyethylene. A flexible sheet-shaped varistor 4 is wound around the insulating layer 3 over the entire length of the CV cable 1 to cover the insulating layer 3. The varistor 4 is covered with a metal shielding layer 6, which is connected to the ground 7 at the end of the cable 1 via electrode fittings (not shown). Further, the metal shielding layer 6 is covered with the sheath 5 made of an insulating material such as vinyl.

The varistor 4 used in this embodiment is a ready-made Levarton Polyvar (registered trademark). This Polyvar is composed of a conductor material, a semiconductor material, an insulating material, and a bonding material that bonds them. As the conductor material, titanium carbide, tantalum carbide, tungsten carbide, columbium carbide, zirconium carbide, etc. are used. Further, as the semiconductor material, silicon carbide, beryllium carbide, zinc oxide or the like is used. Further, fumigated silicon dioxide, kaolin, calcium sulfide, etc. are used as the insulating material. A thermosetting polymer containing epoxy, rubber, or the like is used as a bonding material for bonding these conductor material, semiconductor material, and insulating material. Polyvar is formed as a flexible sheet-shaped varistor 4 by composing each material in a predetermined weight ratio. The specific gravity of the varistor 4 is significantly lower than the specific gravity of the normal varistor used in the above-mentioned conventional technology (specific gravity of the conventional varistor is 5.0 or more, specific gravity of the varistor 4 of this embodiment is 2 to 3). .

The varistor 4 of this embodiment has a strip shape and is spirally wound around the outer periphery of the insulating layer 3 with no space as shown in FIG. Lightning surge current flows from conductor 2 to insulation layer 3
To break through part of and flash over to the varistor 4. Then, the current flows through the varistor 4 and is discharged from the metal shielding layer 6 to the ground, and the subsequent current thereafter is blocked by the varistor 4. Although a part of the insulating layer 3 is pierced as described above, the subsequent insulation is secured by the varistor 4.

As described above, in this embodiment, the varistor 4 is interposed between the insulating layer 3 of the CV cable 1 and the sheath 5, and the varistor 4 is connected to the ground 7 via the metal shielding layer 6. . That is, in this embodiment, the CV cable 1 itself has a lightning protection function. As a result, unlike the prior art, in this embodiment, it is not necessary to separately provide a lightning protection unit, and it is not necessary to secure a space for installing a lightning protection device. Further, since the function as the lightning protection device is exhibited only by connecting the metal shielding layer 6 to the ground 7, the lightning protection device can be easily constructed.

Further, in this embodiment, even if the insulating layer 3 is deteriorated over time, or the original insulating ability is lost due to discharge breakdown due to the inclusion of foreign matter, the insulation between the conductor 2 and the sheath 5 will be varistor. It can be securely held by No. 4. That is, the varistor 4 acts as a backup function of the insulating layer 3.

Further, in this embodiment, the conductor 2 and the sheath 5 are used.
By interposing the varistor 4 between and, it is possible to reduce the electric field strength between the conductor 2 and the sheath 5.
That is, as is clear from FIG. 3, when the varistor 4 does not exist and the conductor is covered only with the insulating layer 3, the electric field strength on the surface of the conductor 2 is high. On the other hand, in this embodiment, since the dielectric constants of the insulating layer 3 and the varistor 4 are different, the conductor 2
The electric field strength on the surface of the is reduced.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, the same members as those of the first embodiment will be omitted from description and will be described with the same member numbers.

As shown in FIG. 4, in this embodiment, the varistor 4 is not provided over the entire length of the CV cable 1.
Further, in this embodiment, the outer periphery of the conductor 2 in the vicinity of the joint P of the CV cable 1 is not covered with the insulating layer 3, but is covered with only the varistor 4 wound. The outer circumference of the varistor 4 is covered with the metal shielding layer 6, and the outer circumference thereof is covered with the insulating tape 10. The metal shield layer 6 is connected to the ground 7 at the end of the cable 1.

That is, in this embodiment, unlike the first embodiment, the varistor 4 is directly wound around the conductor 2 of the CV cable 1. Even with such a configuration, when lightning strikes the CV cable 1, the lightning surge current flows from the conductor 2 to the varistor 4 and is connected to the metal shielding layer 6 through an electrode fitting (not shown) as in the first embodiment. Discharged to the ground,
The subsequent flow thereafter is blocked by the varistor 4.

Particularly, in this embodiment, the varistor 4 is used.
Since the joint covers the joint, it is possible to secure the insulation of the portion where foreign matter is easily mixed and the discharge is easily deteriorated. That is, the first
In the embodiment, the gap type lightning arrester is used, whereas in the present embodiment, the gapless type lightning arrester is used. Therefore, also in this embodiment, the same effect as that of the first embodiment can be obtained.

The present invention is not limited to the above embodiments, but may be configured as follows, for example, without departing from the spirit of the invention. (1) The present invention is embodied in a cable other than the CV cable 1 (for example, OF cable, BV cable).

[0028]

As described in detail above, according to claim 1, since the flexible sheet-shaped varistor is directly wound around the cable, the device can be downsized and attached to the cable. Workability can be improved. Also,
Since the lightning arrester has a small number of parts, it is easy to assemble the lightning arrestor and the cost can be reduced.

According to the second aspect, since the varistor is wound around the outer circumference of the joint of the cable where foreign matter is easily mixed, the conductor and the sheath can be reliably insulated. According to the third aspect, it is possible to exert two functions as an insulating layer for insulating between the conductor and the sheath by one varistor and as a lightning protection device at the time of abnormality (at the time of lightning strike).

According to the fourth aspect, since the conductor is double-coated with the insulating layer and the varistor, the conductor and the sheath can be insulated by the varistor even if the insulating layer deteriorates. According to the fifth aspect, when lightning strikes the cable, the lightning surge current can be discharged from the varistor to the ground through the insulating layer.

[Brief description of drawings]

FIG. 1A is a side sectional view of a CV cable according to a first embodiment of the present invention. (B) is a front sectional view of the CV cable.

FIG. 2 is a front view of a state in which a varistor is wound around an insulating layer.

FIG. 3 is a graph showing the electric field strength of a CV cable.

FIG. 4 is a CV in a second embodiment embodying the present invention.
It is a sectional side view of a cable.

FIG. 5 is a schematic view of a conventional lightning arrester.

FIG. 6 is a side sectional view of a conventional cable.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... CV cable as a cable, 2 ... conductor, 3 ... insulating layer, 4 ... varistor, 6 ... metal shielding layer, 7 ... ground, P ...
Cable joint

Claims (5)

[Claims] 1. A flexible sheet-shaped varistor,
A cable with a lightning arrester that winds around the cable and connects the varistor to the ground. 2. The cable with a lightning arrester according to claim 1, wherein the varistor is wound around an outer circumference of a joint of the cable. 3. The cable with a lightning arrester according to claim 1, wherein the varistor surrounds a conductor of the cable. 4. A lightning arrester in which a conductor is covered with an insulating layer and the insulating layer is covered with a sheath, and the insulating layer is covered with a flexible sheet-shaped varistor. With cable. 5. A cable with a lightning arrester according to claim 4, wherein the varistor is connected to the ground.