JP6790014B2 - Submarine cable, how to use submarine cable and laying structure of submarine cable - Google Patents

Description

The present invention relates to, for example, a marine cable or the like for supplying electric power or the like to an unmanned exploration system in the deep sea.

When exploring the deep sea using an unmanned exploration system in the ocean, an unmanned exploration system connected by a submarine cable is delivered from the mother ship into the sea. By using a submarine cable, it is possible to send electric power, signals, etc. from the mother ship to the unmanned exploration system.

Since such a marine cable requires a predetermined axial force, an exterior made of a tensile strength body is provided. The exterior is provided on the outer peripheral portion of the power core wire, for example, in two layers. The tensile strength bodies of each layer are arranged in opposite directions with a predetermined twist pitch (for example, Patent Document 1).

JP-A-2009-199847

Although the marine cable is flexible, it is in a straight state at the time of manufacture, so that even if it is extended into the sea, it does not bend periodically. However, the inventors have discovered a phenomenon in which the marine cable causes periodic swells when the marine cable is repeatedly used via a sheave under certain conditions. If such a swell occurs, there is a risk of damage due to local deformation after being fed into the sea, or falling out of the groove of the sheave when rewinding through the sheave.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a marine cable or the like capable of suppressing the occurrence of swell.

In order to achieve the above-mentioned object, the first invention includes a cable core, an exterior portion arranged on the outer periphery of the cable core, and an outer covering portion arranged on the outer periphery of the exterior portion. In the exterior portion, a plurality of wires are arranged at a predetermined twist pitch in the circumferential direction of the outer circumference of the cable core, the twist pitch of the wire is P, the layer core radius of the wire is r, and the bending range of the marine cable is both. The placement angles of the wires on the cut end face from the respective reference lines are set to θ ₁ and θ ₂ , respectively (except when θ ₁ = θ ₂ ) .
k = (r ² + (P / 2π) ² ) ^1/2
And,
When the marine cable is bent along a sheave with a bend radius of R ,
Of the wires located in the outermost layer,
In the wire rod in which k (θ _2- θ ₁ ) + (1 / k), (P / 2π) ² , ( r / R ), and (sinθ _2- sinθ ₁ ) are maximized,
[{(1 / k) · (P / 2π) ² · ( r / R ) · (sinθ _{2 −} sinθ ₁ )} / {k · (θ ₂ −θ ₁ )}] × 100 ≦ 0.06
It is a marine cable characterized by satisfying.

It is desirable that the wire rod is a wire rod in which a coating portion is formed on the outer surface of a fiber reinforced tensile strength body in which fibers are added to a resin.

It is desirable that the outer coating is made of a braided tube.

According to the first invention, since the pitch of the wire rod of the outermost layer outer layer satisfies a predetermined condition with respect to the bending radius of the sheave , the swell of the marine cable caused by the wire rod when the marine cable is bent. Can be suppressed.

Further, if the wire rod is a fiber reinforced tensile strength body, it is lightweight and a sufficient axial force can be secured. Further, since the tensile strength body is covered with the covering portion, it is possible to prevent the tensile strength body from being damaged. In addition, when the marine cable is used in water, it is possible to prevent water from penetrating into the tensile strength body.

Further, if the outer coating portion is composed of a braided tube, the bending of the marine cable can be easily followed, and water can permeate into the outer coating portion and the water can enter the exterior portion. Therefore, since water pressure is applied to the wire rod in the exterior portion from the entire outer circumference, it is possible to prevent the force from being applied only from the outer peripheral portion of the exterior portion.

The second invention is a method of using a marine cable that is bent along a sheave and is used. The marine cable includes a cable core, an exterior portion arranged on the outer periphery of the cable core, and an outer circumference of the exterior portion. In the exterior portion, a plurality of wires are arranged at a predetermined twist pitch in the circumferential direction of the outer circumference of the cable core, and the twist pitch of the wire is P, and the wire is arranged. The radius of the layer center of the cable is r, the radius of bending by the sheave is R, and the placement angles of the wires from the reference lines on both cut end faces of the bending range of the marine cable are θ ₁ and θ ₂ , respectively (however, θ _1). ( Except when = θ ₂ ) ,
k = (r ² + (P / 2π) ² ) ^1/2
When
Of the wires located in the outermost layer,
In the wire rod in which k (θ _2- θ ₁ ) + (1 / k) · (P / 2π) ² · (r / R) · (sinθ _2- sinθ ₁ ) is maximized,
[{(1 / k) · (P / 2π) ² · (r / R) · (sinθ _{2 −} sinθ ₁ )} / {k · (θ ₂ −θ ₁ )}] × 100 ≦ 0.06
It is a method of using a marine cable characterized by satisfying.

It is desirable that the wire rod is a wire rod in which a coating portion is formed on the outer surface of a fiber reinforced tensile strength body in which fibers are added to a resin.

It is desirable that the outer coating is made of a braided tube.

According to the second invention, the same effect as that of the first invention can be obtained.

A third invention is a structure for laying a marine cable in which a marine cable is laid in the sea via a sheave. The marine cable includes a cable core, an exterior portion arranged on the outer periphery of the cable core, and the above. An outer covering portion arranged on the outer periphery of the outer peripheral portion is provided, and the outer peripheral portion is provided with a plurality of wires arranged at a predetermined twist pitch in the circumferential direction of the outer circumference of the cable core, and the twist pitch of the wire rod is adjusted. P, the radius of the layer core of the wire is r, the radius of bending by the sheave is R, and the arrangement angles of the wire from the reference lines at both cut end faces of the bending range of the marine cable are θ ₁ and θ ₂ , respectively ( However, except when θ ₁ = θ ₂ ) ,
k = (r ² + (P / 2π) ² ) ^1/2
When
Of the wires located in the outermost layer,
In the wire rod in which k (θ _2- θ ₁ ) + (1 / k), (P / 2π) ² , (r / R), and (sinθ _2- sinθ ₁ ) are maximized,
[{(1 / k) · (P / 2π) ² · (r / R) · (sinθ _{2 −} sinθ ₁ )} / {k · (θ ₂ −θ ₁ )}] × 100 ≦ 0.06
It is a submarine cable laying structure characterized by satisfying.

According to the third invention, the same effect as that of the first invention can be obtained.

According to the present invention, it is possible to provide a marine cable or the like capable of suppressing the occurrence of swell.

The figure which shows the marine cable laying structure 1. Sectional drawing which shows the marine cable 3. The figure which shows the state which the marine cable 3 was bent along the sheave 4. (A) is a schematic cross-sectional view showing the submarine cable 3 in the part A of FIG. 3, and (b) is a schematic cross-sectional view showing the submarine cable 3 in the part B of FIG. The figure which shows the relationship between the maximum change rate of the outer wire track length and the swell height of a submarine cable 3. The figure which shows the relationship between the pitch of an exterior wire and the maximum rate of change of a track length of an exterior wire.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing a submarine cable laying structure 1. A sheave 4 is arranged on the hull 2 at sea. The marine cable 3 is extended from the hull 2 into the sea via the sheave 4. That is, in the marine cable laying structure 1, the marine cable 3 is laid in the sea from the hull 2 via the sheave 4. For example, the tip of the submarine cable 3 is connected to an unmanned exploration system and can send power and signals to the unmanned exploration system.

As described above, when the marine cable 3 is sent out into the sea, the marine cable 3 is bent and deformed with a bending radius corresponding to the diameter of the sheave 4. When the marine cable 3 passes through the sheave 4, the marine cable 3 is in a substantially straight state (a state in which bending deformation is not mechanically applied) in the sea. The details of the state of the marine cable 3 at the time of bending will be described later.

Next, the marine cable 3 will be described. FIG. 2 is a cross-sectional view of the submarine cable 3. The marine cable 3 is mainly composed of a power core 5, an exterior portion 9, an outer coating portion 11, and the like. The configuration of the submarine cable 3 is not limited to the illustrated example.

The electric power core 5 includes a conductor portion 15, a covering portion 17, and the like. The covering portion 17 is further composed of an insulating layer, a semi-conductive layer, a shield layer, a water-impervious layer and the like. The conductor portion 15 is formed by, for example, twisting copper strands.

The electric power core 5 configured in this way is collectively twisted for three-phase AC power transmission. Further, an optical cable 7 is provided as a communication cable in the valley portion of the three power lines 5. Further, an intervening layer 21 such as a resin string is formed in the gaps between the three power cores 5 and the outer periphery of the optical cable 7 to form a substantially circular cable core 20.

An exterior portion 9 for supporting the load of the marine cable 3 is provided on the outer periphery of the cable core 20. In the illustrated example, the exterior portion 9 is composed of two layers of wire rods 19a and 19b, which are exterior wires. The wire rods 19a and 19b are made of, for example, a fiber reinforced tensile strength body 10 in which fibers are added to a resin. A coating portion 12 made of a resin such as polyolefin is formed on the outer surface of the fiber reinforced tensile strength body 10.

In the exterior portion 9, a plurality of wire rods 19a and 19b arranged in the circumferential direction are wound around the outer periphery of the cable core at a predetermined pitch without a gap. The wire rods 19a and 19b are formed so that the winding pitch is sufficiently longer than the outer diameter of the wire rods 19a and 19b. The wire rod 19a on the inner peripheral side and the wire rod 19b on the outer peripheral side are spirally wound around the outer circumference of the cable core in opposite directions. By spirally winding the wires 19a and 19b in opposite directions in this way, it is possible to prevent the marine cable 3 from being twisted when it is bent or swayed.

An outer covering portion 11 is provided on the outer periphery of the exterior portion 9. The outer coating portion 11 may be made of resin that is extruded and coated on the outer circumferences of the wires 19a and 19b, but it is desirable that the outer coating portion 11 is a braided tube in which a plurality of fibers are woven. That is, the outer covering portion 11 is not a covering portion having a completely water-shielding property, and seawater can easily permeate into the exterior portion 9.

The exterior portion 9 does not necessarily have to have two layers, but it is desirable that the exterior portion 9 is composed of a plurality of layers. Further, the outer diameters of the wire rod 19a in the inner layer and the wire rod 19b in the outer layer do not have to be the same.

Next, a state in which the marine cable 3 is bent will be described. FIG. 3 is a conceptual diagram when the marine cable 3 is bent along the sheave 4. As described above, when the submarine cable 3 is bent, the exterior wire constituting the submarine cable 3 is also bent and deformed in the same manner. Here, the inventors have found that the cause of the above-mentioned swell is caused by repeated squeezing by the sheave.

As described above, in the exterior portion 9, a plurality of wire rods 19a and 19b are arranged at a predetermined twist pitch in the circumferential direction of the outer circumference of the cable core.

Here, as shown in FIG. 1, when the marine cable 3 is used, the marine cable 3 is fed into the sea via the sheave 4 provided on the hull 2. At this time, since the marine cable 3 moves along the sheave 4, it bends and deforms according to the diameter of the sheave 4. When the marine cable 3 is bent, a tensile force or a compressive force is applied to the wire rods 19a and 19b constituting the exterior portion 9 depending on their positions in the circumferential direction. Therefore, a part of the wire rods 19a and 19b is stretched and the other part is shrunk. That is, depending on the position of the exterior wire in the circumferential direction, there are an exterior wire that is stretched and an exterior wire that is contracted.

In this way, even if the lengths of the wires 19a and 19b change depending on the position in the circumferential direction of the submarine cable 3, if the wires 19a and 19b return to their original states after the marine cable 3 passes through the sheave 4, The marine cable 3 that has been unwound into the sea is in a substantially straight state. However, if this length change remains partially, the marine cable 3 will swell according to the difference in length between the wire rods 19a and 19b.

The inventors investigated the wavy marine cable 3, and found that the wire rod 19b of the outermost layer in the exterior portion 9 had a difference in length depending on the position in the circumferential direction. That is, after being repeatedly squeezed by the sheave 4, the difference between the amount of elongation and the amount of contraction generated in each wire 19b gradually becomes difficult to restore, and as a result, the difference in orbital length accumulates. I found it to be the cause.

Therefore, the amount of change in the orbital length when the wire rod 19b located in the outermost layer is bent will be examined below. As shown in FIG. 3, the twist pitch of the wire rod 19b (the winding pitch of the wire rod 19b in the state where the marine cable 3 is extended) is P. Further, let R be the bending radius of the sheave 4 (the long distance from the center of the sheave 4 to the center line of the marine cable 3). Further, let a be the bending length of the marine cable 3 (the length of the range in which the marine cable 3 is bent by the contact with the sheave 4).

Further, FIG. 4A is a schematic cross-sectional view showing the submarine cable 3 at the portion A (end face of the bent portion) of FIG. 3, and FIG. 4 (b) is the ocean at the portion B (end face of the bent portion) of FIG. It is sectional drawing which shows the cable 3. As shown in FIGS. 4 (a) and 4 (b), let r be the radius of the layer center of the wire rod 19b (the radius of the circle connecting the centers of the wire rod 19b provided in the circumferential direction). The outer diameter of the marine cable 3 is d.

Further, the arrangement angles θ ₁ and θ ₂ of the wire rod 19b from the reference lines at both cut end faces (position A and position B) of the wire rod 19b in the range where the marine cable 3 contacts the sheave 4 (bending range) are set. That is, θ ₁ and θ ₂ indicate the circumferential positions of the respective wire rods 19b. For example, when there are 36 wire rods 19b, θ ₁ of each wire rod 19b is displaced by 10 degrees.

Here, the reference line is the radial outer side of the sheave 4 in the radial cross section. Therefore, for θ ₁ and θ ₂ , the side farthest from the center of the sheave 4 is 0 degrees, and the side closest to the center is 180 degrees. Further, θ ₂ can be calculated by θ ₁ and P and a.

In this case, the orbital length l _S of each wire rod 19b in the state where the marine cable 3 is not bent and deformed is the same, and if k = (r ² + (P / 2π) ² ) ^1/2 is defined,
l _S = {k · (θ _2- θ ₁ )}
It is represented by.

Further, the orbital length l _R of each wire rod 19b in a state where the marine cable 3 is bent by the sheave 4 is
l _R = k (θ _2- θ ₁ ) + (1 / k) · (P / 2π) ² · (r / R) · (sinθ _2- sinθ ₁ ).

In this case, the rate of change in the track length of the exterior line is {(l _R- l _S ) / l _S } x 100 (%), so the rate of change in the track length of the exterior line is
[{(1 / k) · (P / 2π) ² · (r / R) · (sinθ _2- sinθ ₁ )} / {k · (θ _2- θ ₁ )}] × 100 (%) ... It can be expressed as equation (1).

Here, as the rate of change of the exterior wire increases, the swell height that can occur increases accordingly. In particular, if the swell height exceeds 5% of the outer diameter of the marine cable 3, for example, the marine cable 3 may come off from the sheave 4. Therefore, it is necessary to suppress the swell height of the marine cable 3 to 5% or less.

In order to reduce the swell height of the marine cable 3 to 5% or less, the maximum rate of change of the outer wire track length may be 0.06% or less. That is, among the wire rods 19b located in the outermost layer, l _R = k (θ _2- θ ₁ ) + (1 / k) · (P / 2π) ² · (r / R) · (sin θ _{2 −} sin θ ₁ ) In the exterior wire that maximizes, that is, the exterior wire that maximizes the amount of change (l _R- l _S ) in the exterior wire, the condition that Eq. (1) is 0.06% or less may be satisfied.

As described above, when the marine cable 3 is bent along the sheave 4, the swell can be set to a predetermined value or less as long as the marine cable 3 is used so as to satisfy the above relationship. Therefore, it is possible to prevent a problem due to the swell of the marine cable 3 from occurring.

As described above, according to the present embodiment, the twist pitch P of the outermost wire rod 19b in the exterior portion 9 of the marine cable 3 is designed so as to satisfy a predetermined condition, so that the ocean via the sheave 4 is provided. Even when the cable 3 is used repeatedly, it is possible to prevent the marine cable 3 from waviness.

Further, since the wire rods 19a and 19b are composed of the fiber reinforced tensile strength body 10 and the fiber reinforced tensile strength body 10 is covered with the covering portion 12 as a protective layer and a water-impervious layer, damage to the wire rods 19a and 19b is suppressed. At the same time, it is possible to suppress the permeation of water into the fiber reinforced tensile strength body 10.

Further, since the outer coating portion 11 is composed of a braided tube, moisture easily permeates to the outer periphery of the cable core. Therefore, the exterior portion 9 does not receive water pressure only from the outer circumference, and the respective wire rods 19a and 19b receive water pressure from the entire circumference. That is, the exterior portion 9 does not receive the compressive force only from the outer circumference.

A marine cable under predetermined conditions was hung on a circular roller corresponding to a sheave, and a U-shaped ironing test was performed with a tension of 40 kN. The swell height of the swell of the marine cable when the marine cable after the U-shaped ironing test was straightened was evaluated as the swell height.

The outer diameter d of the marine cable 3 is 43.9 mm, and the radius of the core of the outermost wire 19b in the exterior portion 9 (radius of the circle connecting the centers of the wires 19b provided in the circumferential direction) r = 18.725 mm. The bending radius R of the sheave 4 was 696.95 mm, and the number of wires 19b was 36.

The swell height under each condition was evaluated by changing the twist pitch P of the outermost wire rod 19b. Further, under each condition, θ ₁ = 0 degree to 350 degree (10 degree pitch), and the rate of change at this time was calculated by the above-mentioned equation (1). Note that θ ₂ was calculated from θ ₁ .

FIG. 5 shows the relationship between the maximum rate of change of the track length of the exterior wire calculated under each condition and the swell height of the submarine cable 3 (ratio of the swell height to the outer diameter of the submarine cable 3) under each condition. It is a figure which shows.

As shown in FIG. 5, in order to reduce the swell height of the marine cable 3 to 5% (C in the figure) or less, the maximum rate of change of the outer line track length is set to 0.06% or less (D in the figure). I know I need to. That is, as described above, among the wire rods 19b located in the outermost layer, l _R = k (θ _2- θ ₁ ) + (1 / k) · (P / 2π) ² · (r / R) · (sin θ _{In the} exterior wire having the maximum _2- sinθ ₁ ), the equation (1) may satisfy 0.06% or less.

Next, the twist pitch P of the outermost wire rod 19b was changed in the range of 200 to 500 mm, and the maximum rate of change of the outer wire track length was calculated by the above-mentioned equation (1). FIG. 6 is a diagram showing the relationship between the above-mentioned maximum rate of change of the outer wire track length with respect to the twist pitch P of the outer wire. That is, the vertical axis is l _R = k (θ _2- θ ₁ ) + (1 / k) · (P / 2π) ² · (r / R) · (sin θ ₂ ) in the wire rod 19b located in the outermost layer. In the wire rod 19b in which −sinθ ₁ ) is maximized, [{(1 / k) · (P / 2π) ² · (r / R) · (sinθ ₂ −sinθ ₁ )} / {k · (θ ₂ −θ) It is a value of ₁ )}] × 100 (%).

In FIG. 6, the twist pitch P of the wire rod 19b may be set so that the maximum rate of change of the track length of the exterior wire satisfies 0.06% or less. That is, as shown in FIG. 6, the twist pitch P of the wire rod 19b may be set within a range in which the maximum rate of change of the outer wire track length is 0.06% (E in the figure) or less.

Here, each specification of the marine cable 3 is designed in consideration of the usage state. For example, the outer diameter of the marine cable 3 is set in consideration of the size of the sheave 4 used (bending radius R by the sheave 4). Therefore, in general, the outer diameter d of the marine cable 3 is set to be about 1/16 of the bending radius R of the sheave 4 (the outer diameter d of the marine cable 3 is the outer diameter of the sheave 4 (= 2R). ) Is set to about 1/32.).

That is, as described above, among the wire rods 19b located in the outermost layer, l _R = k (θ _2- θ ₁ ) + (1 / k) · (P / 2π) ² · (r / 16d) · (sin θ _{In the} wire rod 19b where _2- sinθ ₁ ) is maximized, the submarine cable 3 is
[{(1 / k) · (P / 2π) ² · (r / 16d) · (sinθ _2- sinθ ₁ )} / {k · (θ _2- θ ₁ )}] × 100 (%) ≦ 0. 06 (%)
If the above conditions are satisfied, the occurrence of swelling of the marine cable 3 can be suppressed.

Although the embodiment of the present invention has been described above with reference to the attached drawings, the technical scope of the present invention does not depend on the above-described embodiment. Although the present invention has been described as an example of an embodiment in which a marine cable is fed into the sea via a sheave provided on a hull, the marine cable may be fed into the sea from a coastal facility or a marine facility. It is clear that a person skilled in the art can come up with various modifications or modifications within the scope of the technical idea described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

1 ………… Marine cable laying structure 2 ………… Hull 3 ………… Marine cable 4 ………… Sheave 5 ………… Power line core 7 ………… Optical cable 9 ………… Exterior part 10 ………… Fiber reinforced tensile strength 11 ……… External coating 12 ……… Coating 15 ……… Conductor 17 ……… Coating 19a, 19b ……… Wire 20 ……… Cable core 21 ……… Intervening layer

Claims (7)

With the cable core
An exterior portion arranged on the outer circumference of the cable core and
An external covering portion arranged on the outer periphery of the exterior portion and
Equipped with
In the exterior portion, a plurality of wires are arranged at a predetermined twist pitch in the circumferential direction of the outer circumference of the cable core.
The twist pitch of the wire is P, the radius of the layer of the wire is r, and the placement angles of the wire from the reference lines on both cut end faces of the bending range of the marine cable are θ ₁ and θ ₂ , respectively (however, θ). ₁ = θ ₂ ) ,
k = (r ² + (P / 2π) ² ) ^1/2
And,
When the marine cable is bent along a sheave with a bend radius of R ,
Of the wires located in the outermost layer,
In the wire rod in which k (θ _2- θ ₁ ) + (1 / k), (P / 2π) ² , ( r / R ), and (sinθ _2- sinθ ₁ ) are maximized,
[{(1 / k) · (P / 2π) ² · ( r / R ) · (sinθ _{2 −} sinθ ₁ )} / {k · (θ ₂ −θ ₁ )}] × 100 ≦ 0.06
A marine cable characterized by meeting. The marine cable according to claim 1, wherein the wire rod is a wire rod having a coating portion formed on an outer surface of a fiber reinforced tensile strength body in which fibers are added to a resin. The marine cable according to claim 1 or 2, wherein the outer coating portion is composed of a braided tube. A method of using a submarine cable that is bent along a sheave.
Submarine cable
With the cable core
An exterior portion arranged on the outer circumference of the cable core and
An external covering portion arranged on the outer periphery of the exterior portion and
Equipped with
In the exterior portion, a plurality of wires are arranged at a predetermined twist pitch in the circumferential direction of the outer circumference of the cable core.
The twist pitch of the wire is P, the layer core radius of the wire is r, the bending radius of the sheave is R, and the placement angle of the wire from each reference line on both cut end faces of the bending range of the marine cable is θ. ₁ and θ ₂ (except when θ ₁ = θ ₂ ) ,
k = (r ² + (P / 2π) ² ) ^1/2
When
Of the wires located in the outermost layer,
In the wire rod in which k (θ _2- θ ₁ ) + (1 / k), (P / 2π) ² , (r / R), and (sinθ _2- sinθ ₁ ) are maximized,
[{(1 / k) · (P / 2π) ² · (r / R) · (sinθ _{2 −} sinθ ₁ )} / {k · (θ ₂ −θ ₁ )}] × 100 ≦ 0.06
How to use submarine cables, characterized by meeting. The method for using a marine cable according to claim 4, wherein the wire rod is a wire rod having a coating portion formed on the outer surface of a fiber reinforced tensile strength body in which fibers are added to a resin. The method of using a submarine cable according to claim 4 or 5 , wherein the outer coating portion is composed of a braided tube. A submarine cable laying structure in which a submarine cable is laid under the sea via a sheave.
The marine cable
With the cable core
An exterior portion arranged on the outer circumference of the cable core and
An external covering portion arranged on the outer periphery of the exterior portion and
Equipped with
In the exterior portion, a plurality of wires are arranged at a predetermined twist pitch in the circumferential direction of the outer circumference of the cable core.
The twist pitch of the wire is P, the layer core radius of the wire is r, the bending radius of the sheave is R, and the placement angle of the wire from each reference line on both cut end faces of the bending range of the marine cable is θ. ₁ and θ ₂ (except when θ ₁ = θ ₂ ) ,
k = (r ² + (P / 2π) ² ) ^1/2
When
Of the wires located in the outermost layer,
In the wire rod in which k (θ _2- θ ₁ ) + (1 / k), (P / 2π) ² , (r / R), and (sinθ _2- sinθ ₁ ) are maximized,
[{(1 / k) · (P / 2π) ² · (r / R) · (sinθ _{2 −} sinθ ₁ )} / {k · (θ ₂ −θ ₁ )}] × 100 ≦ 0.06
Submarine cable laying structure characterized by satisfying.

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