JPH0317562Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to the structure of the terminal end of a power cable.

[Prior Art] Generally, the terminal end of a power cable is separated by stripping off the outer shielding layer in stages as shown in Fig.
However, in this case, the electric field at the tip of the external shielding layer becomes extremely high, often causing dielectric breakdown at that part. In order to alleviate such electric field concentration, a method has conventionally been adopted in which a stress cone is formed at the tip of the external shielding layer. Figure 3 shows an example of using a rubber molded stress cone, but such a stress cone is expensive due to its complicated shape, and the adhesion of the interface between the inner surface of the stress cone and the insulator is difficult. Because of the need to ensure that the cable core has a negative tolerance between the outer diameter of the cable core and the inner diameter of the stress cone, this has the disadvantage of making it difficult to insert the stress cone.

In order to improve the drawbacks of the mold stress cone, a method using a ring made of elastic semiconductive rubber or plastic has also been proposed. (Jikko 47-23919, 47-34715,
(Refer to Utility Model Publication No. 52-86691, Japanese Patent Application Publication No. 56-29410, etc.). FIG. 4 shows a conventional example in which an electrically conductive and elastic O-ring 4 is disposed at the tip 21 of the external shielding layer 2 that has been peeled off. The electric field concentration at the tip 21 of the layer 2 is alleviated to some extent, and its elasticity also has the effect of being able to follow the thermal expansion and contraction of the cable core 1.

However, if the O-ring 4 is only provided at the tip 21 of the external shielding layer 2, the tip 2
The electric field relaxation of No. 1 was not yet complete. That is, although the electric field is relaxed by the O-ring 4 in the very vicinity of the tip 21 of the external shielding layer 2, the electric field cannot be effectively relaxed in a wider range.

Therefore, the purpose of this invention is to eliminate the drawbacks of the prior art described above, greatly improve assembly workability, and effectively alleviate the electric field not only in the very vicinity of the tip of the external shielding layer but also in a wider range. The object of the present invention is to provide a structure for the termination of a power cable that can be used to terminate a power cable.

[Means and effects for solving the problem] The gist of this invention is to provide an O-ring 4 having conductivity and elasticity at the tip 21 of the stepped external shielding layer 2, and further to provide an O-ring 4 on the outer periphery thereof. This is because an external stress cone 5 having a dimension that does not come into contact with the cable core 1 is provided.

[Embodiment] FIG. 1 is a partially sectional explanatory view of the terminal end of a power cable showing an embodiment of this invention. As shown in the figure, an O-ring 4 made of conductive and elastic rubber or plastic is provided at the tip 21 of the external shielding layer 2 which has been peeled off. The electric field concentration at the portion 21 is alleviated, and its elasticity allows it to follow the thermal expansion and contraction of the cable core 1. Also,
An external stress cone 5 having a dimension that does not contact the cable core 1 is disposed around the outer circumference of the O-ring 4 .

Here, the conductive portion 51 of the external stress cone 5 is kept at the same electrical potential as the external shielding layer 2.
By combining the O-ring 4 and the external stress cone 5 in this way, the electric field at the tip 21 of the external shielding layer 2 is reduced by the O-ring 4 in the very vicinity of the tip.
and, in a wider range, by the external stress cone 5, respectively. Moreover, since the external stress cone 5 does not come into contact with the cable core 1, there is no need to take into account thermal expansion and contraction of the cable core 1. Incidentally, 6 is a conductive paint for electrically connecting between the O-ring 4 and the external shielding layer 2, thereby ensuring a more effective electric field relaxation effect.

[Effects of the invention] As explained above, this invention provides a power cable that is very inexpensive, has good assembly workability, and can effectively alleviate electric field concentration at the tip of the external shielding layer over a wide range. It is extremely effective as a method for alleviating the electric field at the tip of the outer shielding layer, especially when a water termination method is adopted in a lightning impulse voltage test.

[Brief explanation of the drawing]

FIG. 1 is a partially cross-sectional explanatory diagram showing one embodiment of the termination part of a power cable according to the present invention, FIG. 2 is a front view showing a step-stripped part of the external shielding layer at the termination part of the power cable, and FIG. 3 4 is a partial cross-sectional front view showing a conventional example in which a rubber molded stress cone is inserted into the tip of the external shielding layer, and FIG. FIG. 2 is a partially sectional front view showing a conventional example. 1...Cable core, 11...Conductor, 12...
Insulator, 2... External shielding layer, 21... Tip, 3
...Mold stress cone, 31...Conductive part,
4...O-ring, 5...External stress cone, 5
1... Conductive part, 6... Conductive paint.

Claims (1)

[Scope of utility model registration request] A conductive and elastic O-ring is provided at the tip of the stepped external shielding layer, and an external stress cone having a dimension that does not make contact with the cable core is provided around the outer circumference of the O-ring. The structure of the termination part of the power cable.