JP2015220155A - Watertight power cable and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve watertightness and flexibility at a low cost.SOLUTION: In a watertight power cable 100 comprising a conductor part 20 and a coating layer 30 coating the conductor part 20, a synthetic resin powder 22 is interposed between the conductor part 20 and the coating layer 30 at a plurality of positions in the longitudinal direction of the watertight power cable 100, whereby, even if water enters inside the conductor part 20 of the watertight power cable 100, the synthetic resin powder 22 is swept away and enters into a gap to close the entry path and effectively suppress progression of the water entry. In addition, watertight compound filled along the entire length of the cable becomes unnecessary to enable cost reduction.

Description

  The present invention relates to a watertight power cable and a manufacturing method thereof.

In power cables used as submarine power cables, prevention of moisture intrusion into conductors has been an important issue.
Also, in the case of power cables or electric wires (hereinafter referred to as “cables”) laid in the ground, when laying in soil where groundwater exists or in soil containing a lot of moisture, It was necessary to prevent intrusion.

  For this reason, conventionally, as a watertight structure for electric wires and power cables, an ethylene-vinyl chloride copolymer, an ethylene-acrylate copolymer, a vinyl chloride-between a central conductor and an insulating layer formed on the outer periphery thereof are used. A starch-polyacrylate polymer and a maleic anhydride modified ethylene oligomer or a maleic anhydride modified propylene oligomer are kneaded with a synthetic resin plastic obtained by mixing one or more of vinyl acetate-maleic acid copolymer. Accordingly, filling with a watertight compound containing a plasticizer, a stabilizer, a filler, and a rust inhibitor has been performed (for example, see Patent Document 1).

  Also, as another watertight structure of electric wires and power cables, in a conductor portion in which a plurality of stranded wire layers are formed around a core wire, a string made of a water-absorbing swollen body spirally wound between each layer of the conductor portion A string-like member and a string-like member extending in parallel with the core wire are disposed, and when the moisture enters, each string-like member expands to exhibit water-stopping performance (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 06-325626 JP-A-11-162264

  In the watertight structure of Patent Document 1, it is necessary to fill a watertight compound over the entire length of a cable or the like between the conductor and the insulating layer in order to more effectively prevent moisture from entering into the deep part. However, when the watertight compound is filled over the entire length of the cable or the like, the amount of use becomes excessive, and there is a problem that an increase in the manufacturing cost of the cable cannot be avoided.

  On the other hand, since the watertight structure of Patent Document 2 interposes a string-like member made of a water-absorbing swelling body in the conductor portion, the amount of raw material used for the string-like member can be reduced. Since the member is inserted over the entire length in the longitudinal direction of the cable or the like, there has been a problem that the flexibility of the cable or the like is deteriorated and the bending diameter is increased.

  An object of the present invention is to provide a watertight power cable that is low in cost and excellent in watertightness and flexibility, and a method for manufacturing the same.

  The present invention provides a watertight power cable comprising a conductor portion and a coating layer covering the conductor portion, and a synthetic resin powder is provided between the conductor portion and the coating layer at a plurality of locations in the longitudinal direction of the watertight power cable. It is characterized by being interposed.

  Further, the present invention provides a watertight power cable comprising a conductor portion and a coating layer covering the conductor portion, the conductor portion is composed of a plurality of strands, and at a plurality of locations in the longitudinal direction of the watertight power cable, A synthetic resin powder is interposed between a plurality of strands of the conductor portion.

In the present invention, since the synthetic resin powder is interposed between the conductor portion and the coating layer or between the plurality of strands of the conductor portion, when moisture enters the conductor portion, the synthetic resin powder is swept away into the gap. Entering, blocking the intrusion route, can suppress the progress of moisture intrusion.
In addition, since the synthetic resin powder is present at a plurality of locations in the longitudinal direction of the watertight power cable, it is easier to bend the watertight power cable than when the synthetic resin powder is present over the entire length, and the flexibility is improved. Can be achieved.
Furthermore, since the synthetic resin powder is filled in a plurality of locations in the longitudinal direction of the watertight power cable, the amount of the synthetic resin powder used can be reduced and the manufacturing cost of the watertight power cable can be reduced.
Therefore, when laying on the seabed or underground, a long watertight power cable is required, but the laying cost can be reduced sufficiently.

In the above invention, the synthetic resin powder may be thermally deformed.
The synthetic resin powder may be polyvinyl chloride.
The synthetic resin powder may be applied by an electrostatic dry spray method.

  Further, the present invention provides a method for manufacturing a watertight power cable in which a conductor portion is composed of a plurality of strands, wherein the plurality of strands of the conductor portion are both static before and after being twisted. The synthetic resin powder is coated by an electrodrying spraying method.

  In this case, since the synthetic resin powder is applied before and after the twisting of a plurality of strands, the synthetic resin powder can be effectively interposed between the strands and is also synthesized on the outer peripheral surface of the conductor portion. It is possible to apply resin powder.

  As described above, the present invention makes it possible to provide a watertight power cable that is low in cost and excellent in watertightness and flexibility, and a method for manufacturing the same.

It is sectional drawing of the watertight power cable which is 1st embodiment. It is a figure which shows a part of cross section of a circular pressure conductor. It is a figure which shows the one part cross section of the conventional circular pressure conductor. It is sectional drawing along the longitudinal direction of a watertight power cable. It is a schematic block diagram of the implementation equipment which forms the circular pressure conductor of a watertight power cable. It is sectional drawing of the watertight power cable which is 2nd embodiment. It is sectional drawing of the watertight power cable which is 3rd embodiment.

[First embodiment]
An embodiment showing a watertight power cable of the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view of a watertight power cable 100.
The watertight power cable 100 includes a circular conductor 20 as a conductor portion at the center, and the pressing tape 30 for powder, the inner semiconductive layer 40, the insulating layer 50, and the outer half in order from the circular conductor 20 to the outside. A conductive layer 60, a metal coating 70, and an anticorrosion layer 80 are formed.

[Round pressure conductor]
As shown in FIG. 2, the circular conductor 20 has a structure in which a plurality of copper wires 21 are twisted together and pressed into a circular shape. In FIG. 2, the twisted state of a part of the strands 21 of the cross section of the circular conductor 20 is extracted and illustrated (the same applies to FIG. 3 described later). And the synthetic resin powder 22 is sprayed to the outer peripheral surface of each strand 21 by the electrostatic dry spraying method before twisting together, and the synthetic resin powder has adhered.
The synthetic resin powder 22 is preferably PVC (polyvinyl chloride), but may be a resin such as PS (polystyrene), PE (polyethylene), PP (polypropylene).
Moreover, when using the synthetic resin powder 22 of PVC, although it does not specifically limit, For example, a thing with a particle size of about 2 micrometers is preferable. In this case, the “fluidity index” representing the fluidity of the powder is 38, which is lower than that of other particle sizes and resin types, resulting in clogging and a watertight effect.

Fluidity index = (tap density-bulk density) / tap density x 100
Bulk density: Density including gaps when powder is statically packed in container Tap density: Density after gaps are filled as much as possible by tapping after statically filling powder in container

Moreover, it is preferable that the particle diameters of the powders have the same particle diameter. This is because when a Gaussian-type particle size distribution (average particle size μ and dispersion σ ² follows a well-known Gaussian function) is given, the larger the particle size distribution width, the smaller the volume fraction (more difficult to clog). It is known and derived from this fact.

FIG. 3 shows a filling state of water-tight rubber 22S conventionally used for comparison. In the case of this water-tight rubber 22S, it is filled so that no gap is generated between the strands 21. On the other hand, in the case of the synthetic resin powder 22 of FIG. 2, it does not adhere so that the clearance gap between each strand 21 is filled.
Further, as shown in FIG. 4, the synthetic resin powder 22 is formed such that a fixed range of adhesion ranges 221 and a fixed width of non-adhesion ranges 222 are alternately arranged with respect to each strand 21. Moreover, each strand 21 is formed so that the adhesion range 221 of the synthetic resin powder 22 may match in the longitudinal direction in a twisted state.
4 illustrates the case where the length L1 of the adhesion range 221 is equal to the length L2 of the non-adhesion range 222. However, the present invention is not limited to this, for example, the length of the non-adhesion range 222. The adhesion range 221 may be formed at regular intervals by making L2 longer than the adhesion range L1.

The circular pressure conductor 20 is sprayed with the synthetic resin powder 22 on its outer peripheral surface even after the strands 21 are twisted together. Then, on the outer peripheral surface of the circular conductor 20, the entire outer periphery including the non-adhesion range 222 is covered with the powder pressing tape 30 to prevent the synthetic resin powder from peeling off and flowing out.
The powder pressing tape 30 functions as a “coating layer covering the conductor portion”.
The powder pressing tape 30 is not limited as long as it can hold the inner synthetic resin powder 22, but allows the synthetic resin powder 22 to move together with moisture when moisture enters. It is desirable. Therefore, what can maintain a covering state by adhesion | attachment of tapes rather than the adhesive tape with which the adhesive was apply | coated is desirable. Specifically, as the pressing tape 30 for powder, a single-side water-absorbing conductive Tetron tape or the like generally used as a divided conductor pressing tape is suitable, and a woven fabric is preferable instead of a nonwoven fabric from the viewpoint of preventing powder leakage.

[Each layer on the outer circumference of the circular conductor]
The inner semiconductive layer 40 and the outer semiconductive layer 60 are formed from a semiconductive resin composition. This semiconductive resin composition is obtained by appropriately mixing carbon black for imparting conductivity and other compounds with a base resin made of a polyolefin resin such as an ethylene-vinyl acetate copolymer.
The insulating layer 50 is made of a crosslinked polyolefin (based) resin.
As the metal cover 70 and the anticorrosion layer 80, well-known ones usually used for watertight power cables are used. For example, an aluminum corrugated tube is used for the metal cover 70, and a vinyl sheath or the like covering the outer periphery of the metal cover is used for the anticorrosion layer 80.

[Method of forming circular conductor]
FIG. 5 shows an implementation facility for forming the circular conductor 20 of the watertight power cable 100 described above. Reference numeral 201 in the drawing is a drum of the twisting machine 200 and is supported so as to be rotatable around a center line along the longitudinal direction of the watertight power cable 100. The drum 201 is provided with a plurality of bobbins around which the strands 21 are wound along the circumference, and the strands 21 are drawn out one by one from each bobbin. And each strand 21 is twisted in the twist position of the code | symbol 203, is compressed by the cross-sectional circle shape, and becomes the one circular pressure conductor 20. FIG.

  And between the drum 201 and the twisting position 203 of the said twisting machine 200, the powder coating apparatus 300 which implements an electrostatic dry-type spraying method is arrange | positioned. The powder coating apparatus 300 includes an electrostatic coating gun 301 that charges and discharges the synthetic resin powder 22 with a predetermined polarity, and each strand 21 that passes through the chamber 302 is unstrained on the side of the synthetic resin powder 22. Is charged with a reverse polarity and sprayed with the synthetic resin powder 22 on the outer peripheral surface of each strand 21.

  An arrow Y in FIG. 5 indicates a direction in which the twisted circular conductor 20 is sent. Further, another powder coating apparatus 310 is disposed downstream of the twisting position 203 in the feed direction Y, and the synthetic resin powder 22 is attached to the outer peripheral surface of the twisted circular pressure conductor 20. The powder coating apparatus 310 has the same configuration as the powder coating apparatus 300 described above.

  On the downstream side in the feed direction of the powder coating apparatus 310, a covering portion 400 of the powder pressing tape 30 is provided. In the vicinity of the covering portion 400, the powder pressing tape 30 is fed out from the reel, and the covering portion 400 has two powder pressing tapes so as to be sandwiched from both sides along the circular conductor 20 to be conveyed. The outer circumferential surface of the circular conductor 20 is covered by attaching 30 vertically and applying pressure to bring them into close contact with each other.

  With the configuration of FIG. 5, the synthetic resin powder 22 is sprayed by the powder coating apparatus 300 on the plurality of strands 21 fed from the drum 201 of the twisting machine 200 before the twisting position 203. Then, after stopping the spraying of the synthetic resin powder 22, each strand 21 is sent by a fixed distance, and the synthetic resin powder 22 is sprayed again. By repeating this spraying and stopping, an adhesion range 221 having a constant width and a non-attachment range 222 having a constant width are formed alternately with respect to each strand 21.

  Then, the synthetic resin powder 22 is again attached to the circular conductor 20 formed by twisting at the twisting position 203 by the powder coating device 310. Also in this case, by repeating this spraying and stopping, an adhesion range 221 with a constant width and a non-adhesion range 222 with a constant width are formed alternately with respect to each strand 21. Further, it is desirable to control the spraying of the synthetic resin powder 22 by the powder coating apparatus 310 so that the powder coating apparatus 300 sprays the same position as the adhesion range 221 formed on each strand 21.

In the covering portion 400, the circular conductor 20 is covered with the powder pressing tape 30.
The formation of the internal semiconductive layer 40, the insulating layer 50, the external semiconductive layer 60, the metal coating 70, and the anticorrosion layer 80 following the formation of the circular conductor 20 is performed by a conventionally known method, and will be described here. Is omitted.

[Technical effects of watertight power cable]
As described above, the watertight power cable 100 has the synthetic resin powder 22 interposed between the strands 21 constituting the circular conductor 20 and between the circular conductor 20 and the powder pressing tape 30. Therefore, even when moisture enters the inside of the circular conductor 20 of the watertight power cable 100, the synthetic resin powder 22 is swept away and enters the gap, thereby blocking the penetration path and effectively suppressing the progress of moisture penetration. Can do.
Further, the synthetic resin powder 22 is preferably PVC (polyvinyl chloride), but is formed from a resin such as PS (polystyrene), PE (polyethylene: polyethylene), PP (polypropylene), and the like. Since the synthetic resin powder 22 is attached to the circular conductor 20 and the strands 21 by the spraying method, the synthetic resin powder 22 is likely to move from the spraying position when moisture penetrates, and the moisture movement route is effective. Can be blocked.
On the other hand, since the synthetic resin powder 22 sprayed on the outer peripheral surface of the circular conductor 20 is covered with the powder pressing tape 30, it is prevented from peeling off and disappearing when moisture does not enter. .

Further, the synthetic resin powder 22 is formed so that the adhesion range 221 having a constant width and the non-adhesion range 222 having a constant width are alternately arranged, and adheres to a plurality of locations dispersed in the longitudinal direction of the watertight power cable 100. Since the gap between the strands 21 is not filled, the watertight power cable 100 can be easily bent and the flexibility can be improved as compared with the case where the synthetic resin powder 22 is filled over the entire length. This makes it possible to reduce drum costs and coiling costs.
Furthermore, since the synthetic resin powder 22 is attached to a plurality of locations dispersed for each attachment range 221 in the longitudinal direction of the watertight power cable 100, the usage amount of the synthetic resin powder 22 is reduced, and the manufacturing cost of the watertight power cable 100 is reduced. Can be reduced.
In particular, the synthetic resin powder 22 is preferably made of a resin such as PS (polystyrene), PE (polyethylene: polyethylene), PP (polypropylene: polypropylene) although PVC (polyvinyl chloride), which is easily available, is preferable. In this case, it is possible to further reduce the manufacturing cost.

  In addition, when the watertight power cable 100 is used as a submarine cable or laid on a soil containing a lot of moisture, the ingress of seawater or soil moisture can be effectively reduced. Since the use of the long watertight power cable 100 is expected, the cable laying cost is particularly reduced due to the reduction of the manufacturing cost. Therefore, the watertight power cable 100 is particularly suitable for laying under the sea or in the soil.

[Second Embodiment]
A watertight power cable 100A according to a second embodiment of the present invention will be described with reference to FIG. About this watertight power cable 100A, about the same structure as the watertight power cable 100 mentioned above, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.
As shown in FIG. 6, the watertight power cable 100A includes a conductor portion 20A at the center, and the binder tape 30A, the inner semiconductive layer 40, the insulating layer 50, and the outer semiconductive layer in order from the conductor portion 20A to the outside. 60, a metal cover 70, and an anticorrosion layer 80 are formed.

The conductor portion 20A is formed by twisting a plurality (for example, five) of divided conductor segments 23A. Each divided conductor segment 23 </ b> A is formed in a sector shape by twisting a plurality of strands 21.
When the five divided conductor segments 23A are twisted together, they become circular in cross section, and the outer peripheral surface thereof is covered with the binder tape 30A, and the twisted state is maintained.

A method for forming the conductor portion 20A from the plurality of divided conductor segments 23A will be described.
The split conductor segment 23A is formed by twisting the strands 21 (see FIG. 2) and the synthetic resin powder 22 (see FIG. 2) by removing the covering portion 400 from the implementation facility for forming the circular conductor 20 shown in FIG. 2) and is compressed into a sector fan shape. Further, the same is true in that a fixed width attached range 221 and a fixed width non-attached range 222 are formed alternately with respect to each strand 21 and the divided conductor segment 23A.

  The implementation facility for forming the conductor portion 20A includes a twisting machine including a drum for feeding a plurality of divided conductor segments 23A, and a powder coating apparatus disposed on the downstream side in the feeding direction of the twisting position of the twisting machine. And a covering portion for covering the conductor portion 20A with a binder tape.

The drum of the stranded wire machine is sent downstream with a watertight tape vertically attached to each divided conductor segment 23A.
Then, at the twisting position, the divided conductor segments 23A are twisted together and a watertight tape is inserted between the divided conductor segments 23A to form the conductor portion 20A.
Further, a water stop yarn supplying means is provided at the twisting position, and the water stop yarn is supplied to the center position of the plurality of divided conductor segments 23A. Thereby, the water stop yarn is inserted into the center of the conductor portion 20A when the divided conductor segments 23A are twisted together.

The powder coating apparatus has the same configuration as the powder coating apparatus 300 in FIG. 5, and the synthetic resin powder is sprayed and attached to the outer peripheral surface of the conductor portion 20A.
The covering portion has the same structure as the covering portion 400 of FIG. 5, and is formed by attaching two binder tapes vertically so as to be sandwiched from both sides along the conductor portion 20A to be conveyed, and applying pressure to bring them into close contact with each other. The outer peripheral surface of 20A is covered.

With the above configuration, the plurality of divided conductor segments 23A fed from the drum of the twisting machine are twisted together at the twisting position to form the conductor portion 20A. The conductor portion 20A is sprayed with synthetic resin powder by a powder coating apparatus on the downstream side of the twisting position. The powder coating apparatus stops the spraying of the synthetic resin powder 22 and then sends each strand 21 for a predetermined distance, and sprays the synthetic resin powder 22 again. By repeating this spraying and stopping, it is formed so that a fixed range of adhesion and a non-adhesion range of constant width are alternately arranged on the conductor portion 20A.
The conductor portion 20A is covered with a binder tape at the covering portion, and the synthetic resin powder 22 on the outer peripheral surface of the conductor portion 20A is held and the divided conductor segments 23A are integrally held.

In the watertight power cable 100A, since the conductor portion 20A is composed of a plurality of sector-shaped segmented conductor segments 23A, a gap is likely to be formed at both ends of the arc portion in the section of the segmented conductor segment 23A, and moisture enters the deeper portion from here It is a structure that is easy to do. However, since the synthetic resin powder 22 is interposed between the conductor portion 20A and the binder tape 30A as the coating layer and between the strands 21 constituting the divided conductor segment 23A, it is possible to block the passage of moisture. In addition, it is possible to effectively suppress the progress of moisture penetration.
Further, the watertight power cable 100A is excellent in flexibility, and the manufacturing cost can be reduced as in the case of the watertight power cable 100.

[Third embodiment]
A watertight power cable 100B according to a third embodiment of the present invention will be described with reference to FIG. About this watertight power cable 100B, about the same structure as the watertight power cable 100 mentioned above, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.
This watertight power cable 100B is generally improved in strength and can be suitably applied particularly as a submarine power cable.
As shown in FIG. 7, the watertight power cable 100B includes a circular conductor 20 at the center, and the semiconductive tape 30B, the internal semiconductive layer 40, the insulating layer 50, and the outside in order from the circular conductor 20 to the outside. A semiconductive layer 60, a semiconductive tape 65B, a metal sheath 70, a floor layer 75B, an iron wire armor 90B, a pressing tape 95B, and an anticorrosion layer 80 are formed.

The floor layer 75B and the iron wire armor 90B reinforce the watertight power cable 100B, and in particular, the iron wire armor 90B can protect the circular conductor 20 from the tension when the watertight power cable 100B is laid. .
Thus, the watertight power cable 100B is excellent in application as a submarine power cable and can effectively suppress the intrusion of seawater into the circular conductor 20. That is, it is possible to provide a watertight power cable excellent in application to a submarine power cable.

In the watertight power cable 100B, the conductor portion 20A including the plurality of divided conductor segments 23A described above may be provided instead of the circular conductor 20.
Further, a three-core twisted conductor portion may be provided instead of the circular conductor 20. In that case, it is desirable to spray the synthetic resin powder 22 for each of the strands constituting each of the three cores, and to spray the synthetic resin powder 22 to the respective outer peripheral surfaces of the three cores.

[Others]
In each of the above embodiments, the case where the configuration in which the synthetic resin powder is interposed between the conductor portion and the covering layer or between the strands constituting the conductor portion is applied to the power cable is exemplified. In addition, the above configuration may be applied to an electric wire composed of a covering layer as an insulating covering that covers the conductor portion.

20 circular conductor (conductor part)
20A Conductor portion 21 Strand 22 Synthetic resin powder 23A Split conductor segment 30 Powder pressing tape (coating layer)
30A Binder tape (coating layer)
30B Semiconductive tape (coating layer)
100, 100A, 100B Watertight power cable

Claims (6)

In a watertight power cable comprising a conductor part and a covering layer covering the conductor part,
A watertight power cable comprising synthetic resin powder interposed between the conductor portion and the covering layer at a plurality of locations in the longitudinal direction of the watertight power cable. In a watertight power cable comprising a conductor part and a covering layer covering the conductor part,
The conductor portion is composed of a plurality of strands,
A watertight power cable comprising synthetic resin powder interposed between a plurality of strands of the conductor at a plurality of locations in the longitudinal direction of the watertight power cable.   The watertight power cable according to claim 1, wherein the synthetic resin powder is thermally deformed.   The watertight power cable according to any one of claims 1 to 3, wherein the synthetic resin powder is polyvinyl chloride.   The watertight power cable according to any one of claims 1 to 4, wherein the synthetic resin powder is coated by an electrostatic dry spraying method. In the manufacturing method of the watertight power cable of Claim 2,
A method for producing a watertight power cable, wherein the synthetic resin powder is coated by electrostatic dry spraying on both the strands of the conductor portion before being twisted and after being twisted.

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