JPH0425645B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing a resin power cable, and in particular, to a cable in which continuous crosslinking of the resin portion (plastic or rubber) and subsequent heating drying are smoothly performed. The present invention relates to a manufacturing method.

<Conventional technology> Conventionally, the electrical and mechanical properties of resin power cables, especially cross-linked polyethylene insulated power cables, have been
After crosslinking, cables manufactured using continuous crosslinking equipment are generally heated and dried again, as this is greatly affected by the crosslinking agent decomposition gas remaining in the insulator.
Removal of residual decomposition gases is being carried out.

<Problems to be solved by the invention> However, although the above method is relatively simple for low-voltage cables with thin insulators, it takes a long time to dry for high-voltage cables with thick insulators. In the case of time-consuming and simple heating drying without pressure,
It turned out that there was a problem with the electrical characteristics. That is, according to research conducted by the present inventors, it has been confirmed that in insulators that have been heat-dried without pressure, minute deterioration occurs in the insulators due to long-term applied voltage.

On the other hand, normally, cables are dried by winding them around a drum and drying them in a drying room. ), the degree of heat transfer is different between the outer surface and the center. However, there was a problem in that the cables ended up with different degrees of drying.

<Means for Solving the Problems> The present invention solves the above problems, namely, prolonged drying time, deterioration of cable properties under no pressure, and non-uniformity of drying in the cable length direction. It was designed to achieve this goal, and its characteristic configuration is that in the production of resin power cables, a continuous crosslinking device and a heating drying device are connected in tandem to continuously crosslink and dry the coating resin of the cable, and to At this time, the drying temperature range is above room temperature and below the crosslinking temperature of the continuous crosslinking apparatus, and the pressure range is above atmospheric pressure and below the pressure applied at the continuous crosslinking position.

<Function> According to this configuration, the cable that comes out of the continuous crosslinking device (at this time, the temperature near the center of the cable is about 40 to 100 degrees Celsius, and the outer layer part is about 10 to 30 degrees Celsius) is continuously heated. Drying is carried out by leading to a heating drying device that is heated and pressurized. For this reason, unlike the conventional method of wrapping the drum around a drum and drying the whole drum in a drying room, it takes time to raise the temperature, whereas with the present invention, the drying process begins while the center is still warm. Therefore, the temperature rises quickly and the drying time can be significantly shortened. In addition, the structure does not require a drum, which naturally ensures uniform drying. Furthermore, the crosslinking decomposition gas is smoothly removed by the drying process under heating and pressure. Here, the reason why the drying temperature range was set to be above room temperature and below the crosslinking temperature of the continuous crosslinking device is because below room temperature, the effect of shortening the drying time is poor.
This is because there is a concern that further decomposition gas will be generated if the temperature exceeds the crosslinking temperature, and gas removal will not proceed smoothly.The reason why the pressure range was set to be above atmospheric pressure and below the pressurizing pressure of the continuous crosslinking device mentioned above is because it is below atmospheric pressure. This is because if the temperature is raised at this temperature, the insulator foams and the electrical properties deteriorate, and the reason why the bridge pressure is lower than that is to prevent the cable insulator from deforming and falling into the stranded conductor voids.

<Example> FIG. 1 shows an example of an apparatus for carrying out the method of the present invention. In the figure, 1 is an extruder, 2 is a continuous crosslinking device continuously connected to this extruder 1, and 3
is a heating drying device installed in tandem with this continuous crosslinking device 2. Here, tandem refers to a state in which skewers are arranged in series, and in addition to the direct connection type shown in the diagram above, tandem refers to the state in which skewers are arranged in series.
(preferably less than 10%) is also broadly included. Further, the arrangement method may be not only horizontal but also vertical. The heating medium used in this heating drying device 3 is not particularly limited, and may be a gas such as air or nitrogen gas, or a liquid such as ethylene glycol or silicone oil. In addition,
The insulator coating resin used includes plastic resins such as polyethylene and ethylene vinyl acetate copolymer, as well as ethylene propylene rubber,
Rubbers such as Elalene copolymer rubbers are also included.

In this device, a conductor 4 is guided to an extruder 1, coated with resin by the extruder 1, and immediately crosslinked by a continuous crosslinking device 2 to produce, for example, a 66Kv.325mm ² crosslinked polyethylene insulated cable. Pressure 6 kg/cm, 1 hour at 70°C or 48°C
Each cable according to the invention was obtained by drying for a period of time. In addition, the crosslinking temperature in crosslinking device 2 is approximately 200℃,
The pressing force of the cross-linking device 2 is about 9 kg/cm, but the cable leaving the cross-linking device 2 is cooled to about 40 to 100 degrees Celsius near the center and about 10 to 30 degrees Celsius in the outer layer. , enters the heating drying device 3.

For reference, a similar cable was obtained using the conventional method (normal pressure, dry room temperature 70°C).

Therefore, first, we measured the amount of residual gas (crosslinking decomposition gas) between the cable of the present invention that was dried for 1 hour and the conventional cable that was also dried for 1 hour. It was 1/4 warm. Next, between the cable of the present invention that was dried for 48 hours and the conventional cable that was also dried for 48 hours, the presence or absence of pressurization does not appear to be a significant difference immediately after the cable is manufactured, but the three After months of long-term energization (38 Kv, 50 Hz), no abnormality was observed in the insulator of the pressurized cable of the present invention, whereas considerable deterioration was observed in the conventional non-pressurized cable. It was done.

<Effects of the Invention> As described in the above description, the present invention can provide a highly productive manufacturing method in which the drying time is shortened in a crosslinked resin power cable. In addition, by heating in a specific range and drying under pressure, cross-linking decomposition gas is smoothly removed, which improves the electrical properties and mechanical properties of not only low-voltage cables with thin insulation, but also high-voltage cables with thick insulation. A cable with excellent physical properties can be obtained. Furthermore, since drum winding is not required, drying is uniform in the length direction of the cable, and a cable of excellent quality can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of an apparatus for carrying out the method of the present invention. In the figure, 1...extruder, 2...continuous crosslinking device, 3
...heating drying device.

Claims (1)

[Claims] 1. In the production of resin power cables, a continuous crosslinking device and a heating drying device are connected in tandem to continuously crosslink and dry the coating resin of the cable, and during the drying, the drying temperature range is set at room temperature or higher to the above-mentioned continuous A method for producing a power cable, characterized in that the crosslinking temperature of the crosslinking device is lower than the crosslinking temperature, and the pressure range is higher than atmospheric pressure and lower than the pressing force of the continuous crosslinking device.