JPH02179216A - How to form cable connections - 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 [Field of Industrial Application] The present invention relates to a method for forming a connection part of an electric cable, particularly an electric cable coated with a rubber layer or a plastic layer.

[Prior Art] Conventionally, crosslinked polyethylene insulated cables (hereinafter referred to as "Cv cables") and the like have generally been manufactured by a dry crosslinking method in order to improve their performance.

[Problem to be solved by the invention] In the case of two legs, the surface of each layer covering the cable (for example, an insulating layer) is extremely smooth, so it is necessary to cover the connection part of the cable with a heat-shrinkable tube. In this case, the contact surface between the insulating layer and the tube may not be completely in contact with each other, or even if it is in close contact with each other, it is likely to peel off over time, resulting in dielectric breakdown at the interface. There was such a problem.

In particular, the interface between the cable and the heat-shrinkable tube is prone to breakage due to high voltages such as lightning impulses, and countermeasures are required.

The purpose of the present invention is to solve the above problems, significantly increase the lightning impulse resistance performance by increasing the adhesion between the cable body and the heat-shrinkable tube at the table connection part, and provide a more durable cable connection part. The object of the present invention is to provide a method that allows the formation of

[Means for Solving the Problems] The gist of the present invention is to sequentially strip off the shielding layer, external semiconducting layer, and insulating layer of a cable, connect the exposed conductor with a conductor connecting tube, and then heat the outer periphery of the cable. Consisting of shrinkable tubing,
When sequentially coating with an electric field relaxation layer, an insulating layer, and an external semiconducting layer, at least the surface of the insulating layer of each step-stripped layer is
The method involves rubbing with 400-mesh sandpaper, and then applying an insulating liquid (for example, silicone oil, bolybdenum oil, etc.) to the surface rubbed with the sandpaper.

Note that the same effect as described above can be obtained by rubbing not only the coating layer of the cable body but also the inner surface of the heat-shrinkable tube.

Furthermore, in addition to rubbing either one of them, rubbing both the surface of the cable coating layer and the inner surface of the heat-shrinkable tube also improves the effect.

[Operation] When a lightning impulse is applied to a cable, a discharge phenomenon (called a streamer or tree) occurs along the cable insulation layer, eventually leading to dielectric breakdown. One of the causes of this is considered to be a minute gap existing between the surface of the cable insulation layer and the connection portion insulation layer. As a solution to this problem, the dielectric breakdown voltage caused by lightning impulses is generally improved by applying oil to the surface of the cable insulation layer and filling the gap with oil.

On the other hand, the present invention focuses on trees that grow along the interface of the cable insulation layer, and by providing unevenness on the surface with sandpaper, the growth of the trees is suppressed and the dielectric breakdown voltage is improved.

In other words, if the interface is smooth, trees will develop in a straight line along the interface, resulting in faster growth and faster dielectric breakdown. However, by forming the interface into an uneven shape, trees will develop in a straight line. This causes interference and increases dielectric breakdown voltage.

Note that when the distance between the concave and convex portions formed on the surface of the cable insulation layer by sandpaper treatment is extremely narrow (specifically, when rubbed with sandpaper of 400 mesh or more), the interface becomes almost a straight line. This also takes into consideration the possibility that the

In addition, the present invention applies an insulating liquid having a higher dielectric breakdown voltage than air to the uneven surface, thereby filling the interface with the insulating liquid, and as a result, the dielectric breakdown voltage is further increased. It is about improving.

This is due to the synergistic effect produced by the combination of the sandpaper treatment and the application of the insulating liquid, and is a remarkable effect unique to the present application.

It is difficult to predict the side sole from the effects of either sandpaper treatment or insulating liquid coating treatment.

In addition, the present inventors conducted tests for the purpose of confirming the effects of the present invention, and the results are shown in Table 1 below.

Table [fii consideration] 1) 2 samples (7) 33 KV -I X 60-<7) CVI
- each end of the pull (insulation thickness 81 m) with an insulating layer length of 15 m
Samples (Nα1 to Nα14) were prepared by stripping off the fins so that there were no fins, connecting the exposed conductor with a conductor connecting tube, and covering the circumference with a heat-shrinkable tube.

2) Charging method (according to IEC method) Charging starts from 95 KV and increases by 10 KV/+10 times. At room temperature, in the atmosphere.

[Example] Next, an example of the present invention will be described based on the drawings. The shielding layer 1, the outer semiconducting layer 2, and the insulating layer 3 of both cables are sequentially stripped off, and the conductor 4 is connected to the conductor connecting pipe 5. After connecting, cover the conductor connection tube 5 with a shield layer 7 made of a heat-shrinkable tube, and remove the step using a 300-mesh sand vapor (each coating layer 1.2.3 of the conductor 4 in the figure). By rubbing the shield layer 7, an uneven surface is formed, and silicone oil is applied to the area. Then, an electric field relaxation layer 8 made of a heat-shrinkable tube, an insulating layer 9, and an external semiconducting layer 10 are provided on the circumference, and a metal shielding layer 11 is further provided thereon. Note that 6 in the figure is a conductive thin layer provided on the surface of the insulating layer 3 near the end of the external semiconducting layer 2 as necessary.

The heat-shrinkable tube constituting the electric field relaxation layer 8 is attached to each coating layer 1.
．． 2. It can be placed over the uneven surface of 3. Note that, if necessary, the inner surface of the heat-shrinkable tube constituting the electric field relaxation layer 8 may also be rubbed with a sand vapor of 180 to 400 mesh.

[Effects of the Invention] As described above, according to the present invention, one or both of the inner surface of the heat-shrinkable tube and the surface of the cable coating layer is
By rubbing with a 400-mesh sand vapor and then applying an insulating liquid, the interface between the two becomes extremely strong and stable, and as a result, the dielectric breakdown properties are improved without increasing the size of the connection part. Also, it is possible to form a connecting portion of a power cable with extremely excellent lightning impulse characteristics.

In addition, the cable connections can be tightly bonded using extremely simple means without using any special machinery.
As a result, it is possible to provide a power cable connection portion with excellent workability and economical efficiency.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view for explaining a method of forming a cable connection portion according to the present invention. 1.11: Shielding layer, 2.10: External semiconductive layer, 3.9: Insulating layer, 4: Conductor, 5: Conductor connection tube, 6: Conductive thin layer, 7: Shield layer, 8: Electric field relaxation layer. Brother 1tEI

Claims (1)

[Claims] 1. The conductors at the ends of the stripped cables are connected with a conductor connecting tube, and then the outer periphery is sequentially covered with an electric field relaxation layer, an insulating layer, and an external semiconductive layer made of a heat-shrinkable tube. In the method for forming a cable connection part, before coating with the electric field relaxation layer, at least the surface of the insulating layer of the cable coating layer in contact with the inner surface of the electric field relaxation layer is rubbed with 180 to 400 mesh sandpaper, and further rubbed with the above sandpaper. 1. A method for forming a cable connection, comprising applying an insulating liquid to a surface of the cable. 2. The method of forming a cable connection part according to claim 1, using a heat-shrinkable tube whose inner surface is rubbed with 180-400 mesh sandpaper.