JP2007273277A - Cable and cable deterioration prevention method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an underwater cable that can more easily suppress deterioration due to intruding water.
A cable in which a conductor in which metal strands are assembled is covered with a plastic insulating layer, and a drug injection passage is provided in the center of the conductor. Further, the cable in which the drug injection passage of the cable is configured by a hollow tube having a through hole in a side wall, and the conductor has a metal wire arranged around the hollow tube. Also, a cable in which a drug for preventing moisture deterioration of the insulating layer is injected through the drug injection passage of the cable.
[Selection] Figure 1

Description

  The present invention relates to a cable suitable for laying underwater, and more particularly to a cable suitable for underwater suspension laying and a method for preventing deterioration due to intrusion water.

  For submarine cables, such as submarine cables, which are always submerged, it is necessary to prevent the generation of water trees that cause insulation breakdown due to the small amount of water that penetrates into the insulator during long-term use. . For this reason, generally, a metal coating layer such as lead is provided outside the insulating layer (see Patent Document 1). For example, most of the submarine cables for electric power are provided with a lead sheath outside the insulating layer. Recently, a simple water shielding layer obtained by laminating a metal foil made of lead or aluminum with plastic may be used. In any case, the water shielding function of the cable is maintained by the metal coating.

  By the way, since renewable energy such as wind power and sunlight can be produced in large quantities on the water, especially on the ocean, recently, a power generation facility for natural energy was installed on a large floating body moored on the ocean. There are an increasing number of plans to transmit power to land using a power transmission cable (see, for example, Patent Document 2). However, the position of the floating body always changes due to the influence of wind, waves, and tidal currents, so the cable drawn from here is constantly deformed. That is, the curvature is constantly changing. For this reason, repeated fatigue occurs in the cable. In particular, cracks due to repeated fatigue occur in a short period of time in the water shielding metal coating in the section of the cable laid in the sea. When water enters from this crack, a water tree is generated in the cable insulation layer. For example, in a cross-linked polyethylene insulated cable having a water shielding function by metal coating, a water tree may be generated in the entire insulation layer in several years in an actual sea area.

  As described above, the cable used by being connected to the floating body is not satisfactory in the water shielding effect by the metal coating layer alone.

  It is known that the generation of water trees can be prevented if a moisture-fixing chemical that can react with and fix moisture that has penetrated into the plastic insulator and fix it to prevent deterioration of insulation performance is sent into the insulator. It has been. As such a chemical, a silicon-based hydrophilic coupling agent that reacts with water and easily undergoes a crosslinking reaction is known. It has been confirmed that when this agent is injected under pressure into a minute gap between the conductor strands of a cable in which a water tree is generated in the insulating layer, it reacts with moisture in the insulator to form a polymer with stable insulation performance. ing. It has also been verified that this restores the insulation performance of the cable with water trees.

However, it is practically difficult to pressure-inject a silicon-based hydrophilic coupling agent into a minute gap between the conductor strands of the cable.
JP 2002-281629 A JP 2004-192831 A

  An object of the present invention is to provide an underwater cable that can more easily suppress deterioration due to intrusion water, and in particular, to improve the life of a fatigue-advanced plastic insulated power cable that is suspended in the sea and constantly changes its curvature. . Furthermore, an object of the present invention is to provide a method for preventing deterioration of an underwater cable due to intrusion water.

The invention of the present application is as follows.
(1) A cable in which a conductor in which metal strands are gathered is covered with a plastic insulating layer, and a drug injection passage is provided in the center of the conductor.
(2) The medicine injection passage is constituted by a hollow tube having a through hole in a side wall, and the conductor is formed by arranging a metal wire around the hollow tube. cable.
(3) The cable according to (1), wherein a drug for countermeasure against moisture deterioration of the insulating layer is injected through the drug injection path.
(4) The cable according to (3), wherein the agent for preventing moisture degradation is a silane coupling agent.
(5) The cable according to (1), wherein the cable is a cable for underwater suspension that is laid in a suspended state in water from a floating body moored on water.
(6) A method for preventing deterioration of a cable due to intrusion water, comprising injecting a chemical for preventing moisture deterioration of an insulating layer after laying the cable according to any one of (1) to (5).

  The present invention provides a medicine injection passage in the central portion of the conductor, so that in the case of a new cable, a medicine, for example, a medicine for preventing moisture deterioration of the insulating layer, in particular a water tree, is previously provided in the conductor through this passage. Can be injected with medicines to prevent this. Thereby, it is possible to prevent the generation of the water tree of the insulator for a long time.

Further, even after the cable is installed in water, it is possible to easily inject additional medicine from the passage. By this additional injection, for example, deterioration due to intruding water of the plastic insulated power cable, in particular, generation of a water tree of the insulator can be prevented for a long period of time.
When a hollow tube having a through hole in the side wall is used, a drug injection passage can be appropriately formed. In addition, the injected drug can be distributed in a balanced manner over a long distance.

  As the above-mentioned agent, an agent for preventing moisture deterioration of the insulating layer, for example, an agent for preventing a water tree or an agent for restoring the insulating performance of the insulating layer in which the water tree is generated can be injected. More specifically, it is possible to inject a drug that has the property of fixing moisture, such as a drug that adsorbs or reacts with water, and more specifically, a drug such as a silane coupling agent that reacts with water to polymerize.

  The cable of the present invention is particularly suitable for a cable for underwater suspension that is laid in a suspended state in water from a floating body moored on water. According to the cable of the present invention, the lead coating layer or the lead-bonded plastic tape fusion layer outside the insulating layer is omitted, and the weight of the cable, which is particularly important for underwater suspension cables, is reduced and the diameter is reduced. It is possible.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  FIG. 1 is a perspective view showing a three-phase power transmission cable as an example of the cable of the present invention. FIG. 2 is a schematic cross-sectional view of the cable of the present invention shown in FIG. This three-phase power transmission cable has three wire cores 6. The wire core 6 has a conductor 3 in which a large number of conductive metal strands 2 are combined around a thin hollow tube 1.

  The hollow tube 1 forms a drug injection passage. As shown in an enlarged perspective view in FIG. 3, the hollow tube 1 is made of plastic or metal having a large number of minute through holes 11 in the circumferential direction and axial direction of the tube. The tube. In the case of a metal tube, a bellows tube is desirable.

  When the hollow tube 1 is a metal or plastic tube and a plurality of through holes 11 are provided in the circumferential direction and the axial direction of the tube, it is easy to follow the deformation of the cable and the injected medicine Can be distributed in a balanced manner over a long distance.

  The hollow tube 1 used in the present invention is preferably a metal or plastic tube, and the inner diameter is preferably 5 mm or less, more preferably 2 to 3 mm. Moreover, an outer diameter becomes like this. Preferably it is 6 mm or less, More preferably, it is 3-6 mm. Examples of the metal forming the tube include stainless steel, copper, and aluminum, and a material that can easily process fine through holes on the side surface of the tube is preferable. Moreover, as a plastic which forms a pipe | tube, the material excellent in chemical resistance like nylon and a polyethylene is mentioned, for example, The material which is easy to form the pipe | tube excellent in mechanical strength, such as compression resistance, is preferable.

  The through-hole 11 is provided in the side wall of the hollow tube 1, and it is preferable that a plurality of minute through-holes 11 are provided in the circumferential direction and the axial direction. The size of the through hole 11 is preferably 0.01 to 0.1 mm in diameter. Moreover, the ratio of the through holes 11 occupying the outer peripheral surface of the side wall of the hollow tube 1 is preferably 5 to 10% in terms of area.

  Although not shown in the drawings, as a medicine injection passage instead of the hollow tube 1, a structure in which an elongated wire is wound in a spiral like a spring can be used. In such a spiral tube, since the drug can pass through the gap between the wires, there is no need to newly provide a through hole on the side surface of the tube. When manufacturing the cable, it is desirable that the winding direction of the wire rod of the spiral tube and the direction in which the metal strand 2 is wound are opposite to each other.

  As shown in FIG. 1, a conductor 3 is formed on the outside of the hollow tube 1 by winding a number of metal wires 2 having excellent conductivity. The metal strand 2 is wound so that the hollow tube 1 is not crushed, that is, the hollow portion of the hollow tube 1 is continuously maintained. The conductor 3 has an uncompressed stranded wire structure so that liquid can pass between the metal wires 2. Thereby, it becomes a structure where the chemical | medical agent which flows out from the through-hole 11 of the hollow tube 1 reaches | attains the insulating layer 4 easily.

  As shown in FIG. 1, a plastic insulating layer 4 made of cross-linked polyethylene is extruded outside the conductor 3 and a seating cloth tape layer 5 is provided on the outer surface thereof. The cloth tape layer 5 may be a cloth tape layer used in a conventional underwater cable.

  In the conventional submarine cable, it was necessary to provide a lead coating layer or a lead-laminated plastic tape fusion layer outside the insulating layer 4 for water shielding, but this is omitted in the cable structure of the present invention. In the underwater suspension cable, the weight of the cable, which is particularly important, is reduced and the diameter is reduced (however, a water shielding metal coating may be provided outside the insulating layer 4 if necessary).

  In the three-phase AC power transmission cable shown in FIG. 1, intervening cords 7 twisted with polypropylene yarn are arranged around three wire cores 6, and polyethylene is extruded around these to form an intermediate plastic layer 8. Provided. A sheathing wire 9 is wound around the intermediate plastic layer 8. For the exterior wire 9, a high-strength steel material is usually adopted so as to withstand the weight of the cable suspended in the sea, the floating rocking force, and the tidal force. Further, in order to reduce the weight of the cable in the sea, fiber reinforced plastic or aramid fiber having excellent strength can be used. The outermost part is the anticorrosion plastic layer 10, and usually a vinyl chloride coating is often used in the land portion, but it is preferable to use a polyethylene coating with low water permeability for underwater use.

  In a preferred mode of use of the cable of the present invention, the drug is injected into the drug injection passage formed by the hollow tube 1 in the final stage of cable manufacture. The injected drug is sent through the hollow tube 1 to the entire length of the cable, passes through the gap between the metal wires 2 and reaches the insulating layer.

Next, drugs that can be injected in the present invention will be described.
Examples of the agent to be injected include agents for preventing moisture deterioration of the insulating layer, for example, agents for preventing water trees and agents for recovering the insulating performance of insulating layers in which water trees are generated. More specifically, agents that adsorb moisture or react with moisture, more specifically, agents that fix moisture, such as hydrophilic coupling agents, for example, silane coupling agents that react with moisture. Is mentioned.

  As the hydrophilic coupling agent, a silane coupling agent is preferable. A silane coupling agent is an organosilicon compound having a functional group that can chemically bond to both inorganic materials and organic materials that are not familiar to each other, and is represented, for example, by the following general formula.

In the formula, Y represents a reactive organic functional group, X represents a hydrolyzable group, R represents an alkylene group, and n represents an integer of 1 to 3. Y is a site having a role of reacting with or compatibilizing with an organic resin, and representative examples include an amino group, an epoxy group, a vinyl group, a methacryl group, and a mercapto group. Y is chemically and thermally stable because Y is bonded to the silicon atom by an alkylene group R through a Si—C bond.
On the other hand, the hydrolyzable group X is hydrolyzed by invading water to become silanol (SiOH), which is a site where they mutually react with each other or react with an inorganic material. X includes an alkoxy group, an acetoxy group, an isopropenoxy group, a chloro group, an amino group, and the like. An alkoxy group is preferable from the viewpoint of safety and ease of handling, and an ethoxy group and a methoxy group are particularly preferable.

In the present invention, the silane coupling agent having an alkoxy group is considered to act as follows.
When an initial water tree is generated on the surface of the insulating layer and moisture penetrates into the insulating layer, the alkoxy group of the silane of the silane coupling agent undergoes a hydrolysis reaction in the presence of the intruding water to form a silanol group. Produced and subsequently partially condensed into an insoluble oligomer in water. Since this oligomer also binds to the resin of the insulating layer, it fills the water tree. As a result, it blocks water intrusion, stops further water tree growth, and prevents cable insulation degradation.

  Examples of the hydrophilic coupling agent that can be preferably used in the present invention include the following. γ-aminopropyltriethoxysilane, aminosilane coupling agent, vinyltrimethoxysilane (VTMS), vinyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane. Of these, vinyltrimethoxysilane (VTMS), which is widely used in the production of water-crosslinking polyethylene, is preferred.

  In the present invention, when the hydrophilic coupling agent solution is injected into the drug injection passage, it may be pressurized or not. The concentration of the solution to be injected, the solvent and the like can be appropriately selected from the solutions used in the conventional general silane coupling agent treatment.

  Another embodiment of the present invention is a method for preventing deterioration of a cable due to intrusion water in which a chemical for preventing moisture deterioration of an insulating layer is injected after the cable is laid. In the present invention, since the medicine can be injected through the medicine injection passage, the medicine can be easily injected even after the cable is laid.

  Next, a preferred application of the cable of the present invention will be described. The cable of the present invention can be suitably used as a cable for underwater suspension that is laid in a suspended state in water from a floating body moored on water. In particular, the cable of the present invention is light in weight and can easily prevent water trees from being generated in the cable insulation layer even when repeated fatigue occurs. It can be preferably used as a plastic insulated cable laid in the sea in a suspended state.

It is explanatory drawing which shows an example of the cable of this invention with a perspective view. It is a schematic sectional drawing of an example of the cable of this invention. It is a perspective view of an example of the hollow tube used for the cable of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hollow tube 2 Metal element wire 3 Conductor 4 Insulation layer 5 Cloth tape layer 6 Wire core 7 Interposition string 8 Intermediate plastic layer 9 Exterior wire 10 Anticorrosion plastic layer 11 Through-hole

Claims (6)

  A cable in which a conductor in which metal strands are gathered is covered with a plastic insulating layer, and a drug injection passage is provided in the center of the conductor.   The cable according to claim 1, wherein the drug injection passage is constituted by a hollow tube having a through hole in a side wall, and the conductor is formed by arranging a metal element wire around the hollow tube.   The cable according to claim 1, wherein a chemical for preventing moisture deterioration of the insulating layer is injected through the chemical injection passage.   The cable according to claim 3, wherein the agent for preventing moisture deterioration is a silane coupling agent.   The cable according to claim 1, wherein the cable is an underwater suspension cable laid in a suspended state in water from a floating body moored on water. A method for preventing deterioration of a cable due to intrusion water, wherein a chemical for preventing moisture deterioration of an insulating layer is injected after laying the cable according to any one of claims 1 to 5.

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