JP2000195350A - Manufacture of long plastic insulation power cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable rapid heating or cooling of a cable core wound in a sealed large vessel by performing the winding-up of cable core in the vessel in a dividing manner in a plurality of blocks, and forming a space between the respective blocks. SOLUTION: Winding-up of a cable core 1 is performed under a stacked state, in a concentric dividing manner in four donut-shaped blocks 3, 3, 3, 3. Between the respective blocks 3, 3, 3, 3, ring-shaped spaces 4, 4, 4 with a width of 0.2-5 m are formed. In each space 4, one cable core 1 which is connected to between the blocks 3 exists. In the winding-up of this cable core 1, the stacking is started from a portion being an innermost block 3, then after the completion of specified stacking operation is moved to a portion being an outer circumferential block 3, and hereat a method of restarting the stacking is repeated. In this case, a vessel 2 rotate to take into the cable core 1 from the outside in order.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a long plastic insulated power cable, and more particularly to a method for shortening the time required for heating and cooling a plastic insulating layer.

[0002]

2. Description of the Related Art Electric power cables can be broadly classified into two types, oil immersion insulated cables and plastic insulated cables, depending on the material used to form the insulating layer. In the production of oil-immersed insulated cables, there are problems such as the risk of environmental pollution due to oil leakage and the high production cost due to the need for oil supply equipment. Is used as an insulating layer, and for direct current, a cross-linked polyethylene, modified polyethylene, or the like to which carbon, magnesium oxide, or the like is added as a filler is used. In such a plastic insulated power cable, a particularly long cable is manufactured as follows.

[0003] First, an inner semiconductive layer on a long stranded conductor,
An insulating layer and an outer semiconductive layer are sequentially formed to form a cable core. When forming a crosslinked polyethylene as the insulating layer, a crosslinking step is performed under a high temperature condition in order to react the polyethylene with a crosslinking agent such as dicumyl peroxide. The length of the cable core thus obtained is very long, usually ranging from several km to several tens km.

[0004] This long cable core 1 is shown in FIG.
As shown in the figure, in a sealed large container 2 called "cauldron",
It is wound in a stacked state in 20 to 100 stages. The sealed large container 2 has a double structure at its peripheral wall and bottom, and a heating or cooling medium flows through the inside thereof, whereby the wound cable core 1 inside is heated or cooled. It has become so. Further, the sealed large container 2 has a lid (not shown) and has an airtight structure, and the inside thereof can be brought into a depressurized state or a pressurized state by a vacuum pump or a pressure pump (not shown). I have. Further, the container 2 is rotatable around its central axis, and the container 2 can be rotated and wound up and sent out of the cable core 1.

[0005] Then, by heating the stacked cable cores 1 while keeping the inside of the sealed large container 2 at normal pressure or reduced pressure, it is contained in the inner semiconductive layer, the insulating layer, the outer semiconductive layer and the like. Heat and remove moisture and crosslinker residue. For example, when dicumyl peroxide is used as a cross-linking agent, methane, cumyl alcohol, acetophenone, which are decomposition products thereof, and α-methylstyrene and water generated by decomposition of cumyl alcohol are removed. This is because moisture slightly lowers the insulation resistance of the insulating layer, and the residue of the cross-linking agent causes space charge to be formed when DC is applied, causing electric field distortion and lowering the breakdown voltage. At the same time, the conductor may be energized to increase the heating efficiency. This heating is performed at a temperature of 60 to 90 ° C. for about 5 to 20 days. Then, the heating was stopped to cool the container 2, and after 5 to 10 days, the temperature of the cable core 1 was lowered to room temperature
When cooled to 60 ° C., the cable core 1 is sent out of the container 2 and subjected to post-processes such as tape winding, formation of a shielding layer, and lead coating, to obtain a product.

In such a manufacturing method, since the cable core 1 is extremely long, the cable core 1 wound in the sealed large container 2 is formed into a single large donut-shaped block. For example, in the case of a length of 50 km, the outer diameter is 17 m, the inner diameter is 7 m, and the height is 3.4 m. Therefore, the heat capacity and the heat resistance of this block become extremely large, and the heating and cooling of the cable core 1 require such a long time as described above. As a result, the productivity of the long insulated plastic power cable becomes low. ing.
In addition, the temperature of the block at the time of drying is low near the outer periphery where the heat radiation is large, and is high in the central portion where the heat radiation is small, so that a temperature distribution can be achieved.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to enable rapid heating or cooling of a cable core wound in a sealed large container.

[0008]

This problem is solved by dividing a cable core into a plurality of blocks when stacking and winding the cable core in a container, and forming a gap between the blocks. You.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
FIG. 1 shows a state of winding a cable core in a sealed large container in the production method of the present invention. In FIG. 1, reference numeral 1 denotes a cable core, which is the same as a conventional cable core, and has an inner semiconductive layer, an insulating layer, and an outer semiconductive layer on a long stranded wire conductor. Are sequentially formed. These layers are formed by a method of extruding each layer in a separate step, or a three-layer simultaneous extrusion method in which three extruders are simultaneously extruded by installing them in tandem. When cross-linked polyethylene is provided as the insulating layer, a cross-linking step is performed under a high temperature condition in which a cross-linking agent made of an organic peroxide such as dicumyl peroxide is reacted with polyethylene.

This cable core is wound up in a large sealed container 2. The size of the large sealed container 2 varies depending on the length of the cable core 1 and the like.
In the case of about km, the inner diameter is 15 to 20 m and the depth is 3 to 5
m. This large sealed container 2 is rotatable in the same manner as the conventional one, and its peripheral wall and bottom have a double structure, inside which a heating or cooling medium flows, and a cable. The core 1 can be heated or cooled. Further, it has a lid (not shown).

As shown in FIG. 1, the winding of the cable core 1 is carried out from the inner peripheral side to the outer peripheral side in a stacked state and concentrically with four donut-shaped blocks 3, 3, 3,.
It is divided into three. Then, each block 3, 3,
3, a ring-shaped space 4, 0.2 to 5 m wide,
4 and 4 are formed, and one cable core 1 connected between the blocks 3, 3, 3 and 3 is present in each of the gaps 4, 4 and 4.

The winding of the cable core 1 is as follows.
The stacking is started from the innermost block 3 and, when the predetermined stacking is completed, the process moves to the outer block 3 and the stacking is restarted. Will be At this time, the container 2 rotates and takes in the cable core 1 sequentially from the outside. Also,
A method of starting stacking from the portion that becomes the outermost block 3 and sequentially shifting to the inner blocks 3 and 3 may be used. Further, when stacking the blocks 3, 3, 3, it is possible to appropriately use a cylindrical slab to prevent collapse.

[0013] Heating and cooling steps are sequentially performed on the cable core 1 in the wound state of the cable core 1 as in the conventional case. The heating removes the cross-linking agent residue and moisture. For example, when dicumyl peroxide is used as a cross-linking agent, methane, cumyl alcohol, acetophenone, which are decomposition products thereof, and α-methylstyrene and water generated by decomposition of cumyl alcohol are removed. Drying is performed at a temperature within a range where the insulating layer and the semiconductive layer are not deformed, and usually 75 to 90 ° C. is the upper limit temperature.

In such a manufacturing method, the winding of the cable core 1 in the container 2 is performed by being divided into four relatively small blocks 3, 3, 3, 3. Since the gaps 4, 4, and 4 are formed between 3, 3, and 3, the heat capacity and the heat resistance of each block 3 are reduced, and the heating efficiency and the cooling efficiency are increased.
Can be heated and cooled in a short time. Further, in the present invention, the number of blocks is not limited to four, but may be an arbitrary plural number depending on the shape such as the diameter and length of the cable.

In general, it is known that the time constant of cooling or heating of a plate having a certain thickness R is proportional to the square of the thickness R. That is, when the thickness is reduced to one half, the heating time or the cooling time is reduced to one fourth. The donut-shaped block wound in the container 2 is considered to be a cylindrical body having a certain thickness, and if this cylindrical body is regarded as a deformation of a plate-like body, if the thickness of the block is reduced to half, heating is performed. The time or cooling time is reduced by a factor of four.

[0016] Therefore, the time required for the above-mentioned drying and cooling can be greatly reduced. For example, 50 km from the start of heating and drying of the conventional cable core 1 to the end of natural cooling.
About 60 days was required for about 2 days
Since it takes only 0 days, the number of production days can be significantly reduced, and the product delivery time can be shortened accordingly.

Further, in the manufacturing method of the present invention, it is possible to flow dry nitrogen for cooling into the conductor of the cable core 1 wound around the large sealed container 2. Here, an unsealed large container may be used instead of the sealed large container 2. Since the conductor is usually formed of a stranded wire, a gap exists between the strands, and the block-shaped cable can be efficiently cooled by forcibly flowing dry nitrogen into the gap. In addition to shortening the cooling time, it is also effective in further removing moisture and cross-linking agent residue.
Such a manufacturing method can be applied to manufacture of both AC and DC power cables.

[0018]

As described above, according to the method for manufacturing a long plastic insulated power cable of the present invention, the time required for each of the steps of drying and cooling the cable core can be greatly reduced, and the number of manufacturing days can be greatly reduced. And a significant reduction in costs is achieved.

[Brief description of the drawings]

FIG. 1 is a partially sectional perspective view illustrating an example of a manufacturing method of the present invention.

FIG. 2 is a partially sectional perspective view illustrating a conventional manufacturing method.

[Explanation of symbols]

1. Cable core, 2. Sealed large container, 3. Block,
4 ... void

Claims (2)

[Claims] 1. A long plastic insulation for providing a cable core by providing an insulating layer made of plastic on a long conductor, winding the cable core into a container, and then heating and cooling the cable core in the container. In the power cable manufacturing method, the winding of the cable core in the container is performed by dividing the cable core into a plurality of blocks, and a gap is formed between the blocks. Production method. 2. The method for manufacturing a long plastic insulated power cable according to claim 1, wherein cooling nitrogen is flowed through the conductor during cooling.