JPH0261206B2 - - Google Patents

Description

BACKGROUND AND OBJECTIVES OF THE INVENTION The present invention relates to a method for connecting power cables, and more specifically, the present invention relates to a method for connecting power cables, and more specifically, the present invention relates to a method for connecting power cables. Concerning how to connect power cables.

2. Description of the Related Art Conventionally, it is well known that semiconductive heat-shrinkable tubes are used for connecting portions of high-voltage power cables. This heat-shrinkable tube is widely used because it alleviates the electric field generated on the surface of the connection portion of the conductor, improves the finish of the surface, and has excellent connection workability.

The use of the heat-shrinkable tube will be explained below with reference to the drawings. In FIG. The conductor coating layer 4 such as the cable insulation layer 3 is peeled off, and the exposed conductors 5 are brought into contact with each other, and the connection points are compressed and connected by the conductor connection sleeve 6. The connection point is further covered by the heat-shrinkable tube 7 and the molded insulator 8.

The heat-shrinkable tube 7 arranged as described above
is inserted in advance on at least the cable insulation layer 3, preferably on the outermost layer of the cable (not shown), away from the conductor connection location so as not to interfere with the conductor connection work. Once the conductor 5 is connected, the heat-shrinkable tube 7 is moved to the conductor connection point and its ends are connected to the cable inner semiconducting layer 2.
The conductor connection portion is covered by heat shrinking while overlapping the conductor connection portion until it comes into close contact with the exposed conductor portion. The heat-shrinkable tube 7 used in this manner must have an inner diameter at least larger than the cable insulation layer 3 before heat-shrinking.

On the other hand, as the voltage of the power cable increases, the thickness of the insulating layer 3 increases and the outer diameter of the cable increases, so the heat-shrinkable tube 7 also needs to have a larger shrinkage amount. However, because the heat-shrinkable tube 7 has a limited shrinkage rate due to its characteristics, especially in the case of the above-mentioned ultra-high voltage cable,
It ended up being placed over the conductor connection part without being able to shrink sufficiently.

If the heat-shrinkable tube 7 is not sufficiently shrunk, a gap may be formed between the end of the tube 7 and the cable inner semiconducting layer 2 in contact with the tube, or even if there is no gap initially, the tube 7 may be exposed to high temperature. When the conductor connection sleeve 6 was touched, it softened and thermally expanded, producing local protrusions 9.

The gap or local protrusion 9 has become a fatal defect in the dielectric strength of the conductor connection.

One way to prevent the occurrence of such gaps or local protrusions 9 is to use a heat-shrinkable tube 7 whose inner diameter upon final contraction is sufficiently smaller than that of the cable internal semiconductive layer 2.

That is, the heat-shrinkable tube 7 that has finished shrinking while leaving a sufficient shrinkage amount retains a shrinkage force corresponding to the unshrinkable amount, and can be brought into close contact with the cable internal semiconducting layer 2 with this shrinkage force, so that the gap can be reduced. And the occurrence of local protrusions 9 could be prevented.

However, the heat-shrinkable tube 7 provided as described above is required to have a larger shrinkage rate in addition to having a larger inner diameter before shrinking in the case of the above-mentioned ultra-high voltage cable.

However, manufacturing a heat-shrinkable tube with a high shrinkage rate requires high-grade materials and advanced processing techniques, resulting in high manufacturing costs.

The object of the present invention is to eliminate the above-mentioned drawbacks, use a heat-shrinkable tube having a commonly used shrinkage ratio, and prevent the above-mentioned gaps or local protrusions from occurring in the internal semiconducting layer of the connecting portion of a power cable. An object of the present invention is to provide a method for connecting the power cable.

SUMMARY OF THE INVENTION That is, the object of the present invention is to further convert the end portion of the semiconductive heat-shrinkable tube that covers the entire conductor exposed at the connection portion to another heat-shrinkable tube having a different heat shrinkage ratio or outer diameter. This is achieved by a method for connecting a power cable, characterized in that an internal semiconducting layer is formed at the connecting portion by covering the connecting portion with a tube and thermally shrinking the heat-shrinkable tubes.

Embodiment Hereinafter, an embodiment of the present invention will be described based on a connection work process with reference to the drawings.

In FIG. 2, as in FIG. 1, two power cables 10a and 10b to be connected have conductors 11 exposed at their ends facing each other, and the conductors 11 are compressed and connected by a conductor connection sleeve 12. has been done. A semiconductive heat-shrinkable tube (hereinafter referred to as the main tube) 13 that covers the entire conductor exposed at this connection portion is inserted in advance onto the insulating layer 14 of the one power cable 10b.

In addition, there are two semiconductive heat-shrinkable tubes (hereinafter referred to as auxiliary tubes) that have a smaller inner diameter before contraction and are shorter than the main tube 13.
15 are inserted over the cable internal semiconductive layer 16 and the insulating layer pencil ring portion 17 of the power cables 10a and 10b, respectively.

Next, as shown in FIG. 3, after the conductor 11 is connected, the main tube 13 is moved to the conductor connection location, and both ends thereof are connected to the cable inner semiconducting layer 13.
6 and is heat-shrinked. As a result, the main tube 13 is brought into close contact with the conductor connection location, and its end portion is brought into close contact with the semiconductive layer 16 within the cable. Further, the two auxiliary tubes 15, 15 are respectively moved to positions straddling the main tube 13 and the cable inner semiconductive layer 16, and are heat-shrinked and brought into close contact with the main tube 13 and the cable inner semiconductive layer 16. .

The connection portion is further covered with a molded insulator (not shown) in the conventional manner to complete the connection process.

As mentioned above, the main tube 13 and the auxiliary tube 1
5 are respectively heat-shrinked to form an internal semiconducting layer at the connection portion.

Note that the power cables 10a and 10b have an outer diameter of 100 mm, and a cable internal semiconductive layer 16 of 40 mm.
Therefore, the inner diameters of the main tube 13 and the auxiliary tube 15 before contraction are 120 mm for the main tube 13 and 120 mm for the auxiliary tube 1.
5 each have a diameter of 60 mm, and the tubes 13,
15, which has a shrinkage ratio of three times the commonly used one, is used.

Therefore, when the main tube 13 stops contracting with its end in contact with the cable internal semiconductive layer 16, its final contracted diameter is set to 40 mm. on the other hand,
Since this value of the final contraction diameter is also the contraction limit value of the main tube 13, the main tube 13 is in close contact with the cable inner semiconductive layer 16 with almost no contraction force remaining. Further, the auxiliary tube 15 can be contracted to a final contraction diameter of 20 mm, but since it is in close contact with the cable internal semiconductive layer 16 via the main tube 13,
The contraction is stopped at a diameter of 40 mm, and the remaining 20 mm of contraction is maintained. That is, the auxiliary tube 15 maintains the same contraction force as if it were given twice the elongation, and the main tube 13
It is closely attached to.

In addition, in the above example, the same shrinkage force can be obtained using only a heat-shrinkable tube whose inner diameter before shrinkage is 60 mm, but the connection using such a heat-shrinkable tube As shown in FIG. 4, this method involves making the pencil ring part 17 unduly long because it is necessary to set the tube 18 aside from the cable insulation layer pencil ring part 17 in order to secure a connection point when connecting the conductors. Especially undesirable.

Further, the auxiliary tube 15 may be made of a material with a higher shrinkage rate, for example, a material with a higher melt viscosity, or
By being made of a material with a high heat distortion temperature,
Adhesion with the end portion of the main tube 13 is further ensured, and the occurrence of the local protrusion 9, etc. is reliably prevented.

Further, the main tube 13 may be provided to a length that overlaps the cable semi-conductive layer 16, or the tip of the tube 13 may overlap the cable semi-conductive layer 16.
Although the auxiliary tube 15 may be provided with a length sufficient to contact the exposed conductor and cover the exposed conductor, for example, in the case of the former case, the auxiliary tube 15 does not necessarily have to be semiconductive. However, in the latter case, since the auxiliary tube 15 has semiconductivity,
The auxiliary tube 15 and the main tube 13 ensure a semiconducting layer at the connection portion.

Effects of the Invention As described above, according to the connection method of the present invention,
We use multiple types of heat-shrinkable tubes with different heat-shrinkage ratios or outer diameter dimensions for power cable connections.
By providing a main tube that covers the entire exposed conductor part and an auxiliary tube that further covers the ends of the main tube as in the conventional case, the local protrusion that occurs on the internal semiconducting layer, which was the biggest defect in the connection part, is eliminated. It has the effect of completely preventing such problems.

Furthermore, since the present invention uses a heat-shrinkable tube with a normal heat-shrinkage rate that is formed using inexpensive materials and easy processing techniques, the connection of the power cable itself does not incur any particular increase in costs.

In addition, since two types of heat-shrinkable tubes with different inner diameters before shrinkage are used, there are various advantages such as being able to easily accommodate power cables with large outer diameters depending on the combination of the tubes.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a connecting part for explaining a conventional power cable connecting method, FIGS. 2 and 3 are partial sectional views of a connecting part for explaining a power cable connecting method according to the present invention, and FIG. The figure is a partial cross-sectional view of a connecting portion illustrating an unfavorable arrangement of a heat-shrinkable tube before heat-shrinking. 9... Local protrusion, 10a, 10b... Power cable, 11... Conductor, 13... Heat shrinkable tube (main tube), 14... Insulating layer, 15... Heat shrinkable tube (auxiliary tube), 16 ... Cable internal semiconductive layer, 17 ... Insulating layer pencil ring part.

Claims (1)

[Claims] 1. The cable insulation layer at each end and the internal semiconducting layer of the cable are stripped in stages to expose the conductor end. Insert the heat-shrinkable main tube having semiconductivity that covers the entire conductor connection part, and also insert the semiconductive main tube around the internal semiconductive layer of each power cable or the cable internal semiconductive layer and the tip of the pencil ring part of the cable insulating layer. A process of inserting a heat-shrinkable auxiliary tube that spans the circumference and has a smaller and shorter inner diameter before shrinkage than the heat-shrinkable main tube, and electrically and mechanically connects the conductors of the two power cables. After connecting the cable conductors, the heat-shrinkable main tube is moved onto the circumference of the exposed conductor connection part, and the heat-shrinkable main tube is further heat-shrinked to tightly fit it onto the exposed circumference of the conductor connection part. After heat-shrinking the tubes, move each heat-shrinkable auxiliary tube to a position where it straddles the heat-shrinkable main tube and the cable's internal semiconducting layer, and heat-shrink them to separate them from the heat-shrinkable main tube and the cable's internal semiconducting layer. It is characterized by comprising a step of bringing the heat-shrinkable main tube and the heat-shrinkable auxiliary tube into close contact with the periphery of the semiconducting layer, and a step of forming a predetermined insulator on the periphery of the heat-shrinkable main tube and the heat-shrinkable auxiliary tube after the heat-shrinkable tube is heat-shrinked. How to connect the power cable.