JP3192033B2 - Cable termination - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
For cable termination of high voltage cable with tres cone
Related.

[0002]

2. Description of the Related Art At the end of a high-voltage cable, various types of electrical protection are provided to prevent dielectric breakdown or the like due to disturbance of an electric field. The stress cone is fitted around the outer periphery of the cable insulator as one of such electrical protection means .
FIG. 2 is a longitudinal sectional view of a main part showing an example of a conventional cable terminal. In the figure, a cable 1 has a sheath 2, a shielding layer 3, a semiconductive layer 4, and an insulator 5 that are sequentially peeled off, and a cable conductor (not shown) is terminated inside the bushing 6. An epoxy seat 7 is arranged below the bushing 6, and a stress cone 10 fitted to the insulator 5 of the cable 1 is arranged here. The stress cone 10 is pressurized by a press fitting 8 and a spring unit 9 shown below, and is pressed against the epoxy seat 7 with a constant pressure. With the above-described configuration, electrical protection is provided at the terminal portion of the shielding layer 3 of the cable 1.

[0003]

However, the conventional cable termination as described above has the following problems to be solved. FIG. 3 shows a longitudinal section of a stress cone portion at a conventional cable termination. As shown in this figure, the stress cone 10 has an insulator portion 11 on the high voltage side, and has a semiconductive portion 12 in the shape of a leaf on the low voltage side.
Thus, when viewed from the cross section passing through the cable axis,
An equipotential line is drawn as shown by a dashed line in the figure. As can be seen from this figure, in the conventional stress cone 10, the distribution of equipotential lines generally becomes denser and the electric field tends to concentrate as it approaches the semiconductive portion 12. Therefore, the dielectric breakdown is most likely to occur at the boundary between the insulator 11 and the semiconductor 12. Therefore, as shown in FIG.
The pressure cone 10 is pressed with a predetermined pressure or more to prevent dielectric breakdown. The above-described configuration is mainly adopted at a 66 kV class cable terminal.

However, according to the above configuration, a relatively large spring unit must always be arranged near the stress cone. In addition, for example, 33 kV
At cable terminations below the class, dielectric breakdown can be prevented only by the stress cone without a complicated pressurizing device. As a result, it is possible to reduce the cost of the cable end, simplify the assembly work, and the like. The present invention has been made in view of the above points, and it is an object of the present invention to provide a cable terminal having a stress cone having good electric characteristics, which does not require a pressurizing device such as a large spring unit even at a 66 kV high voltage terminal. It is the purpose.

[0005]

SUMMARY OF THE INVENTION The cable termination of the present invention
The cable is terminated in the bushing and the bushing
The cable is fixed to the support seat, and the cable
The case where the stress cone is placed so as to surround the edge
At the end of the bull, the stress cone is located on the high pressure side
And the semi-conductor part arranged on the low voltage side
The insulator portion is defined by a cross section passing through the axis of the cable.
Spindle type surrounded by a plane almost perpendicular to the equipotential lines seen
In is, the boundaries of the absolute Entai portion and trumpet-shaped semi-conductive portions
A part of the insulator part surrounds a part of the semiconductive part;
A part connected to the semiconductor part from the boundary between the semiconductor part and the insulator part
Is characterized by having a cylindrical shape with almost the same radius.
Things.

[0006]

In the stress cone at the end of the cable , since the insulator portion on the high voltage side is surrounded by a surface substantially perpendicular to the equipotential lines, the density of the equipotential lines is substantially uniform, and electric field concentration is unlikely to occur. Further, the electric field is particularly likely to concentrate at the boundary between the insulator portion and the semiconductor portion. However, the insulator portion surrounds a part of the semiconductor portion, so that high insulation strength is maintained. Furthermore, since the shape from the boundary to the outer periphery of the semiconductive portion is straight, the interface pressure at the rising portion of the stress cone is equalized, and the electrical characteristics are improved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. Figure 1 is a principal part longitudinal cross sectional view of the cable termination embodiment of the present invention. In the cable 1 shown in the figure, a sheath 2, a shielding layer 3, a semiconductive layer 4, and an insulator 5 are sequentially peeled off, and a conductor (not shown) is terminated inside the bushing 6. The bushing 6 is fixed on a pedestal (not shown) by a support fitting 14 at a lower portion thereof.

Here, in the present invention, as shown in the figure, a stress cone 20 having a substantially spindle-shaped insulator portion 21 as viewed from the cross section is put on the insulator 5 of the cable 1. A support seat 16 is arranged to support the semiconductive portion 22, and the support seat 16 is fixedly fastened to the support fitting 14 by a bolt 15. The support seat 16 is made of a metal plate or the like. Between the support seat 16 and the cable 1, as shown in the figure, an insulating tape winding portion 17 is provided.
And are integrated and fixed.

The lower part of the bushing 6 is provided with a protective fitting 18.
The space between the sheath 2 of the cable 1 and the protective fitting 18 is sealed by a seal 19. As shown in this figure, the stress cone 20 of the present invention is arranged so as to surround the cable insulator 5 at the cable end, and the insulator portion 21 arranged on the high voltage side is formed into a spindle shape and arranged on the low voltage side. The semi-conductor portion 22 in the shape of a leaf has a cylindrical shape with substantially the same radius. Then, as shown in the figure, it is positioned inside the bushing 6 while being supported by the support seat 16.

FIG. 4 is an explanatory view for explaining a cross-sectional shape of a stress cone at a cable terminal according to the present invention. As shown in the figure, the insulator portion 21 disposed on the high voltage side
Is a spindle shape surrounded by a surface substantially perpendicular to the equipotential line group indicated by a dashed line shown in the figure when viewed from a cross section passing through the cable axis. Accordingly, the electric field is directed tangentially to any point on the outer surface of the insulator portion 21. With such a configuration, the electric field is almost uniformly distributed from the high voltage side to the low voltage side on the surface portion of the insulator portion 21.

On the other hand, at the boundary between the insulator portion 21 and the semi-conductor portion 22, an electric field tends to concentrate when a structure like a conventional stress cone is used. Therefore, as shown in FIG. 4, a part of the semiconductive part 22 is configured to be surrounded by a part of the insulator part 21. As a result, the electric field concentration is reduced at the boundary. Further, as shown in the figure, a portion from this boundary toward the semiconductive portion 22 is formed into a cylindrical shape having substantially the same radius centered on the cable.

Therefore, when the stress cone 20 is fitted into the cable insulator, the rising portion 22A of the semiconductive portion 22 shown in the figure has a substantially uniform clamping force by the semiconductive portion 22 and the insulating portion 21. Is added. In general,
Such a rising portion 22A tends to be an electrical weak point. Therefore, it is preferable to apply a relatively sufficient pressure to this portion, and the shape as shown in the figure enables electrical reinforcement without using a pressing device such as a spring unit. With the above-described configuration, the terminal portion can be electrically reinforced for a relatively high voltage without using a spring unit or the like as compared with the conventional stress cone of FIG. According to experiments by the present inventors, this stress cone could be stably used at the end of the air of 66 kV class.

The present invention is not limited to the above embodiment. As the material of the stress cone, the insulating portion uses insulating EP rubber, the semiconductive portion uses semiconductive EP rubber, or the like, but other similar insulating or semiconductive materials may be used. Also, the cable termination adopting this is described taking the termination of a CV cable as an example, but can be employed for other similar high-voltage cables. Of course, if a material having high oil resistance is used, it can be used for the terminal in oil.

[0014]

The cable termination of the present invention described above is
The stress cone is a spindle with the insulator part surrounded by a surface almost perpendicular to the equipotential lines viewed from the cross section passing through the cable axis. A part of the part surrounds a part of the semi-conductor part, and the part connected to the semi-conductor part from the boundary is made cylindrical with almost the same radius, so that the electric field distribution on the outer surface of the stress cone becomes uniform Further, the electrical characteristics at the boundary between the insulator portion and the semiconductor portion are improved, and a safe termination of the high-voltage cable can be formed without using a particularly large pressurizing device.

[Brief description of the drawings]

1 is a main part longitudinal sectional view showing an embodiment of a cable termination of the present invention.

2 is a main part longitudinal sectional view showing an example of a conventional cable termination.

FIG. 3 is an explanatory diagram of electric characteristics of a stress cone at a conventional cable termination .

FIG. 4 is an explanatory diagram of electrical characteristics of a stress cone at a cable end according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cable 5 Insulator 20 Stress cone 21 Insulator part 22 Semi-conductor part

Claims (1)

(57) [Claims] A cable is terminated in a bushing and
The bushing is fixed to a support seat, and the support seat is
Stress cones are placed around the cable insulation
At the terminated cable end, the stress cone has an insulator portion disposed on the high voltage side,
A semi-conductor portion disposed on the low voltage side, wherein the insulator portion has a spindle shape surrounded by a surface substantially perpendicular to a group of equipotential lines viewed from a cross section passing through the cable axis, and has a flaky half-shape. At the boundary between the conductor portion and the insulator portion, a portion of the insulator portion surrounds a portion of the semiconductor portion, and a portion connected to the semiconductor portion from the boundary between the semiconductor portion and the insulator portion is A cable end having a cylindrical shape having substantially the same radius .