JP2002298673A - Manufacturing method of crosslinked polyethylene insulation power cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten time needed for gas draining in manufacturing a crosslinked polyethylene insulation power cable through an extrusion coating process 14 of an insulation body, a crosslinking process 16 of the insulation body, a cooling process 18 of a cable after crosslink, and a process 24 for draining methane gas remaining in the insulation body by winding the cooled cable 20 around a drum 22 and heating it. SOLUTION: A cable conductor is heated by high frequency induction heating method, before it is put under a gas draining process 24, after a cooling process 18 is finished. With this, the cable is heated from the inside, so that diffusion velocity of methane gas inside the inner layer of the insulation body is increased and gas draining time is cut down.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a crosslinked polyethylene insulated power cable capable of shortening the degassing time of a crosslinked polyethylene insulator.

[0002]

2. Description of the Related Art To manufacture a cross-linked polyethylene insulated power cable, a cable conductor is extrusion-coated with a polyethylene containing a cross-linking agent (peroxide) to form an insulator.
A step of heating the formed insulator to crosslink, a step of cooling the crosslinked cable, a step of degassing methane gas remaining in the insulator by winding the cooled cable around a drum and heating, Need to go through.

When the insulator is chemically cross-linked with peroxide, methane gas remains in the insulator in a dissolved state as a by-product of the cross-linking reaction. It is provided in. Since the rate at which methane gas diffuses through the crosslinked polyethylene is very slow at room temperature, in the degassing step, heating is performed to accelerate the methane gas diffusion rate, thereby shortening the degassing time.

[0004]

In recent years, power cables have been required to increase in power transmission capacity, and in response to demands for higher voltages, the thickness of insulators has tended to increase. In addition, there is an increasing demand for making one cable longer in order to improve the reliability of the power cable line by reducing the number of connection parts or to reduce the cost of the entire line.

However, when the thickness of the cable insulator is increased, it takes a long time to release the gas, as a matter of course. In addition, when the length of the cable is increased, the amount of the cable wound on one drum increases, and the winding layer increases. Therefore, when this is heated by hot air or the like, heat is not easily transmitted to the inner layer, and sufficient degassing is performed. This will take time. When the diameter and length of the cable are increased, the time required for degassing is increased, and the energy required for heating is also increased. Therefore, there is a problem that the manufacturing cost increases.

[0006] In view of the above problems, an object of the present invention is to provide a method for manufacturing a crosslinked polyethylene insulated power cable that can reduce the time required for degassing.

[0007]

Means for Solving the Problems In order to achieve this object, the present invention comprises a step of extrusion-coating a cable conductor with polyethylene containing a crosslinking agent to form an insulator; a step of crosslinking the formed insulator; The process of cooling the cable after,
In a method for manufacturing a crosslinked polyethylene insulated power cable, which comprises a step of winding a cooled cable around a drum and heating it to degas methane gas remaining in the insulator, after the cooling step is completed and before the degassing step is started. In addition, the cable conductor is heated by a high-frequency induction heating method.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, 10 is a cable conductor sent out from the drum 12,
14 is an extruder for extruding the cable conductor 10 with polyethylene containing a cross-linking agent (peroxide), 16 is a cross-linking section for heating and cross-linking the extruded insulation, and 18 is a cooling unit for cooling the cross-linked cable. Section, 20 is a cross-linked polyethylene insulated power cable coming out of the end seal of the cooling section 18, 22 is a drum for winding the cable 20, 24 is heating the wound cable 20 together with the drum 22 and remains in the insulator. This is a heating chamber for degassing methane gas. In the heating chamber 24, heating is usually performed by blowing hot air.

[0010] This embodiment is suitable for manufacturing a crosslinked polyethylene insulated power cable in a line as described above.
A high frequency induction heating device is provided between the cooling section 18 and the winding drum 22.
The high-frequency induction heating device 26 reheats the cooled cable 20 before winding it around the drum 22 by installing the cable 26. In the case of high-frequency induction heating, the conductor of the cable 20 is heated, and the insulator is heated by the heat of the conductor, so that the cable 20 is wound around the drum 22 while being heated from the inside, and the heating chamber is heated. Combined with the external heating in 24, the whole insulator is efficiently heated. As a result, discharge of methane gas remaining as a by-product in the insulator is accelerated. In particular, in this method, heat is applied from the conductor to the inner layer of the insulator, which promotes the diffusion of methane gas in the inner layer of the insulator, which is likely to be a bottleneck in gas release, resulting in a significant reduction in gas release time. can do.

The heating temperature of the cable conductor by the high-frequency induction heating 26 is preferably set slightly higher than the heating temperature in the degassing heating chamber 24 in order to enhance the degassing effect.

In the embodiment shown in FIG. 1, the cable insulator covering line is a horizontal type, but the cable insulator covering line may be a catenary type or a vertical type.

Further, the present invention is particularly effective when a crosslinked and cooled cable is directly wound around a drum installed in a degassing heating chamber in a manufacturing process of a long cable as in the illustrated embodiment. In addition to this, substantially the same effect can be obtained by a method in which high-frequency induction heating is performed, for example, when rewinding a cable once wound to send it to a degassing step.

[0014]

[Example] In the production line of FIG. 1, 175 kv 2500 mm ² cross-linked polyethylene insulated power cable (total thickness 30.5 mm of coating including insulator) and 66 kv 1000 mm ² cross-linked polyethylene insulated power cable (total thickness 12 mm) Manufactured. The heating condition of the high-frequency induction heating device 26 is adjusted to 80 ° C. according to the conductor size of the cable and the traveling speed of the cable.
It was adjusted to become. The heating temperature in the heating chamber 24 was set to 70 ° C. Under these heating conditions, a gas release time until the methane gas concentration in the insulator became 0.01 cc or less per 1 g of crosslinked polyethylene was determined. The results are shown in Table 1 in comparison with the conventional example.

[0015]

[Table 1]

From the results of this experiment, the high-frequency induction heating device
According to 26, it can be seen that when conductor heating is performed, the heating time required to reduce the methane gas concentration to the target amount can be reduced by about 10 to 15% as compared with the case where conductor heating is not performed.

[0017]

According to the present invention as described above,
When a crosslinked polyethylene insulated power cable is manufactured, the cable before the degassing step is subjected to high-frequency induction heating, so that the time required for degassing the insulator can be significantly reduced. Therefore, the productivity of the crosslinked polyethylene insulated power cable is improved, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a manufacturing method of the present invention.

[Explanation of symbols]

 10: Cable conductor 12: Discharge drum 14: Extruder 16: Bridge section 18: Cooling section 20: Cross-linked polyethylene insulated power cable 22: Winding drum 24: Heating chamber for degassing 26: High frequency induction heating device

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 5G325 GA01 GB29 GC04

Claims (2)

[Claims] 1. A step of extrusion-coating a cable conductor with polyethylene containing a crosslinking agent to form an insulator, a step of crosslinking the formed insulator, a step of cooling the crosslinked cable, and a step of drumming the cooled cable into a drum. In a method for producing a crosslinked polyethylene insulated power cable, which includes a step of winding and heating to degas methane gas remaining in the insulator, after the cooling step, before entering the degassing step,
A method for producing a crosslinked polyethylene insulated power cable, comprising heating a cable conductor by a high-frequency induction heating method. 2. The method for producing a crosslinked polyethylene insulated power cable according to claim 1, wherein the heating temperature of the cable conductor by high-frequency induction heating is set higher than the heating temperature in the degassing step.