JP2000152453A - Power cable end processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To alleviate procedures and time of smoothing work for the surface of cable insulator to shorten the field working time by covering a thermal compression tube to the external circumference of an exposed cable insulator, and then heating it for compression and thereafter extending the thermal compression tube into a cloth condition while the tube is in the high temperature condition. SOLUTION: After an external half-conductive layer 3 is cut to the flat condition, a cable of which cable insulator 2 is exposed is inserted into a thermal compression tube 4 and it is thermally compressed using a dryer. After the thermal compression tube 4 is compressed sufficiently, the thermal compression tube 4 is extended with a cloth tape 5 while the surface temperature of cable insulator 2 set in the higher temperature by the heat treatment is not yet lowered. Accordingly, the surface of cable insulator 2 in the high temperature condition is smoothed by pressing it with the smooth internal surface of the thermal compression tube 4. As a result, while the working time can be shortened remarkably, the smoothed surface and insulation performance similar to that of the related art can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable insulator in which a sheath or an outer semiconductive layer at a cable end is exposed when a prefabricated connection portion is provided in a plastic insulated power cable such as a crosslinked polyethylene cable. The present invention relates to a method for processing a terminal of a power cable for smoothing a surface of a power cable.

[0002]

2. Description of the Related Art At an intermediate connection portion and a terminal connection portion of a crosslinked polyethylene cable, a sheath at an end portion of a cable and an outer semiconductive layer are peeled off to expose a cable insulator, and a prefabricated connection portion is inserted thereon. Many methods have been adopted. At that time, in order to exhibit good electrical characteristics, it is necessary to smooth the exposed surface of the cable insulator as much as possible.

FIG. 4 is a diagram showing a conventional power cable terminal processing method. In FIG. 4, 1 is a cable conductor,
2 is a cable insulator, 3 is an outer semiconductive layer, 4 is a heat-shrinkable tube, 8 is a holding tape, 9 is a temperature sensor, 10 is a heater, and 11 is a heat insulating layer.

After removing the sheath (not shown) at the end of the cable, the outer semiconductive layer 3 is peeled off to expose the cable insulator 2 made of cross-linked polyethylene. Then, in order to smooth the exposed surface of the cable insulator 2, a heat shrinkable tube 4 is put on the cable insulator 2 and is heated and shrunk using a drier or the like. Further, a holding tape 8, a temperature sensor 9 such as a thermocouple, a heater 10, and a heat insulating layer 11 are sequentially formed thereon.

In this state, heating by the heater 10 is performed for a predetermined time while controlling the temperature to be constant using the temperature sensor 9. As a result, the cable insulator 2, the heat-shrinkable tube 4 and the like are heated and expand. However, since the cable insulator 2 and the heat-shrinkable tube 4 are tightened by the pressing tape 8, the smooth inner surface of the heat-shrinkable tube 4 is The surface of the insulator 2 is strongly pressed against the cable insulator 2, and the surface of the cable insulator 2 is smoothed.

After that, the heater 10 is turned off, and after a cooling time, the heat insulating layer 11, the heater 10, the temperature sensor 9, the holding tape 8 and the heat shrink tube 4 are removed.
A cable insulator 2 having a smooth surface appears. When the stress cone of the prefabricated connection portion is inserted and provided thereon, the interface between the stress cone and the cable insulator 2 can be brought into close contact without voids, and good insulation characteristics can be obtained.

[0007]

However, the above-mentioned conventional power cable terminal processing method has a problem that the operation takes too much time and labor. That is, in the above-mentioned conventional method, after the heat-shrinkable tube 4 is heated and contracted, it is necessary to provide the pressing tape 8, the temperature sensor 9, the heater 10, and the heat-retaining layer 11 from above, and the work is troublesome and time-consuming. It takes. Further, in the heat treatment performed thereafter, a long time is required until the temperature reaches a predetermined temperature, a heating time after the temperature reaches the predetermined temperature, and a cooling time after the heat treatment.

SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem and to reduce the labor and time for smoothing the surface of a cable insulator, thereby shortening the on-site construction time.

[0009]

In order to solve the above-mentioned problems, a terminal treatment method for a power cable according to the present invention is characterized in that an outer semiconductive layer of a power cable is stepped off and exposed to an outer periphery of a cable insulator. The method is characterized in that after the tube is covered and heated and shrunk, the cable insulator is squeezed with a cloth from above the heat shrinkable tube while the cable insulator is in a high temperature state. By doing so, the labor and time required for smoothing the surface of the cable insulator can be reduced, and the on-site construction time can be shortened.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory diagram of the processing of the present invention. In FIG. 1, reference numerals 1 to 4 correspond to those in FIG. 4, and 5 is a cloth tape.

After removing the sheath at the end of the cable and stripping off the outer semiconductive layer 3, the heat-shrinkable tube 4 is inserted into the cable where the cable insulator 2 is exposed, and the heat-shrinkable tube 4 is heated and shrunk using a drier or the like. Let it. After the heat-shrinkable tube 4 has sufficiently shrunk, the surface of the cable insulator 2 that has been heated by the heat treatment is not cooled, and is squeezed with the cloth tape 5 from above the heat-shrinkable tube 4.

That is, the central portion of the cloth tape 5 is hung on the heat-shrinkable tube 4 and reciprocated in the direction of arrow A while pulling both ends. Perform while moving in the direction of B.
As a result, the surface of the cable insulator 2 in the high temperature state is smoothed by pressing the smooth inner surface of the heat-shrinkable tube 4.

The power cable terminal processing method according to the present invention can be applied to the cases shown in FIGS. FIG. 2 is a view showing a state in which a rubber stress cone is provided after the mold semiconductive layer is reformed. Reference numerals 1 to 3 correspond to those in FIG. 1, 6 is a mold semiconductive layer, and 7 is a rubber stress cone.

The semiconductive layer 6 is obtained by winding a semiconductive tape or a heat shrinkable tube around the end of the external semiconductive layer 3 that has been peeled off, and then heating and molding the semiconductive layer 3 to form the semiconductive layer again. Thus, even when the end slope of the external semiconductive layer 3 is steep, the rubber stress cone 7
Is prevented from generating a void due to air, so that the insulating properties are improved.

The rubber stress cone 7 is composed of an insulating portion 7a and a conductive portion 7b, and serves to reduce the electric field at the end of the cable. In the prefabricated connection part, such a rubber stress cone 7 is molded in advance at a factory, and in the site, it is only necessary to insert it into the cable core part. In addition, reliability is high.

In this application example, before the mold semiconductive layer 6 is reformed, the surface of the cable insulator 2 is smoothed by the power cable terminal treatment method of the present invention.
As a result, the protrusion of the mold semiconductive layer 6 into the surface of the cable insulator 2 is prevented, and the adhesion between the cable insulator 2 and the mold semiconductive layer 6 is improved, so that the insulation characteristics are improved.

FIG. 3 is a view showing a state in which a rubber stress cone is provided without re-forming the mold semiconductive layer. In this application example, without re-forming the mold semiconductive layer 6,
The rubber stress cone 7 is attached. Even if the mold semiconductive layer 6 is not re-formed as in this application example, when the external semiconductive layer 3 is peeled off stepwise, if the slope of the end of the external semiconductive layer 3 is gently finished, it can be further formed thereon. A void due to air can be prevented from being generated between the rubber stress cone 7 and the inserted rubber stress cone 7, and the insulation characteristics can be improved.

Even in this case, the surface of the cable insulator 2 is smoothed by the power cable terminal treatment method of the present invention, so that the surface of the cable insulator 2 and the mold semiconductive layer 6
And the insulation properties are improved.

[0019]

EXAMPLE A 154 kV, 2000 mm ² CV cable was subjected to a smoothing treatment for each of the five cables according to the method of the present invention and the conventional method, and the working time, surface smoothness and insulation performance were measured.

Table 1 shows the operation time from the state in which the outer semiconductive layer 3 is peeled off to the time when the surface of the cable insulator 2 is smoothed, by comparing the method of the present invention with the conventional method. . In Table 1, “heating” includes the time required for raising the temperature and the time for maintaining the state for a predetermined time after reaching the predetermined temperature. "Cooling" refers to cable insulator 2
Shows the time required for the surface to reach 50 °. From these results, it can be seen that the required working time is significantly shorter in the method of the present invention than in the conventional method.

[0021]

[Table 1]

The surface roughness of the thus smoothed cable insulator 2 was measured one by one using a surface roughness meter. As a result, in the case of the present invention, the maximum was 2.8 μm, whereas in the case of the conventional method, the maximum was 2.6 μm.
And the degree of smoothing was almost at the same level.

Further, after a molded semiconductive layer 6 as shown in FIG. 2 was reformed on the cable manufactured by both methods, a 154 kV-class prefabricated intermediate connecting portion was attached, and the insulation performance was confirmed. Table 2 shows the results. The numerical values in Table 2 are the results of evaluating the electric field at the end of the external semiconductive layer at the time of dielectric breakdown.

[0024]

[Table 2]

As is evident from Table 2, there is no significant difference in dielectric breakdown strength between the present invention and the conventional example. From the above results, according to the power cable terminal processing method of the present invention, the working time is significantly reduced compared to the conventional smoothing processing, and the smoothing surface and insulation performance equivalent to those of the conventional method are obtained. It can be seen that it can be obtained.

[0026]

As described above, the present invention smoothes the surface of the cable insulator by squeezing the heat-shrinkable tube immediately after heat-shrinking the heat-shrinkable tube with a cloth-like body. As a result, it is possible to reduce the labor and time required for the work of smoothing the surface of the cable insulator, and to shorten the on-site construction time.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a process according to the present invention.

FIG. 2 is a view showing a state in which a rubber stress cone is provided after a mold semiconductive layer is reformed.

FIG. 3 is a diagram showing a state in which a rubber stress cone is provided without re-forming a mold semiconductive layer.

FIG. 4 is a diagram illustrating a conventional power cable terminal processing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cable conductor 2 ... Cable insulator 3 ... External semiconductive layer 4 ... Heat shrinkable tube 5 ... Clot tape 6 ... Mold semiconductive layer 7 ... Rubber stress cone 8 ... Pressing tape 9 ... Temperature sensor 10 ... Heater 11 ... Heat insulating layer

Claims (1)

[Claims] 1. An outer semiconductive layer of a power cable is stepped off, and a heat-shrinkable tube is put on an outer periphery of the exposed cable insulator and heat-shrinked, and then heat-shrinked while the cable insulator is in a high temperature state. A method of treating a power cable terminal, wherein the terminal is squeezed with a cloth from above the tube.