JP7679284B2 - Underwater cable inspection device, method and program - Google Patents

Description

An embodiment of the present invention relates to a technology for inspecting underwater cables using an unmanned underwater vehicle.

Wind power is a type of renewable energy that can be found anywhere, does not emit carbon dioxide, does not run out, and can be used permanently. The winds are stronger on the sea than on land, there are no obstacles and the wind is stable, and because they are far from residential areas and noise problems are less likely to occur, large wind turbines can be installed and high power generation efficiency can be expected. For this reason, offshore wind power generation is seen as promising as a major power source in the future. In addition, when the waters of coastal waters are deep, it is difficult to use bottom-fixed wind turbines that are fixed to the seabed, so floating wind turbines that float on the sea surface are used.

In floating offshore wind power generation facilities like this, it is necessary to lay cables underwater or on the seabed to transmit the generated electricity over long distances. However, the cables used in floating offshore installations follow the up and down movement of the wind turbines on the sea, so repeated tension acts on each part, making them prone to damage. For this reason, in order to reduce the fluctuation range of the tension that acts repeatedly on the cables, a layout is adopted in which a subsea floating section is provided midway through the cable to give it flexibility.

JP 2020-080581 A

To promote this type of offshore wind power generation equipment, it is important to establish a method for inspecting and maintaining underwater cables. One possible way to streamline the inspection and maintenance work that was previously done by divers is to use unmanned underwater vehicles (ROVs). However, when an ROV works underwater, it is necessary to establish a method to ensure that it does not get carried away by the tide and lose sight of the inspection location. Furthermore, it is also necessary to establish a method for identifying the inspection location of cables with flexures that cannot be fully identified by the underwater position information of an ROV.

The embodiment of the present invention has been made in consideration of these circumstances, and aims to provide an underwater cable inspection technique that will not lose sight of the inspection point due to the device being swept away by the tide, and that can further identify the inspection location.

In the underwater cable inspection device of the embodiment, the device comprises a clamp meter provided in an unmanned submersible vehicle that performs visual inspection of the underwater cable, which clamps to the underwater cable and detects the magnetic field formed around it to obtain the current flowing in the underwater cable as a detected waveform, a calculation unit that calculates the phase difference between the detected waveform and a reference waveform, and a position identification unit that identifies an inspection position on the underwater cable based on the phase difference , and a data processing unit in which the calculation unit and the position identification unit are provided is disposed in the unmanned submersible vehicle .

Embodiments of the present invention provide an underwater cable inspection technique that prevents the device from being swept away by tidal currents and losing sight of the inspection point, and also makes it possible to pinpoint the inspection location.

1 is an overall view of a floating offshore wind power generation facility to which an underwater cable inspection device according to an embodiment of the present invention is applied. 1A and 1B are conceptual diagrams illustrating the operation of bringing the inspection device according to the embodiment close to the underwater cable and clamping it. FIG. 2 is a block diagram of a data processing unit in the underwater cable inspection device according to the embodiment. FIG. 4 is an explanatory diagram of the principle of derivation of a position signal indicating an inspection position of an underwater cable. 4 is a flowchart for explaining the steps of an underwater cable inspection method according to the embodiment and an algorithm of an underwater cable inspection program.

Embodiments of the present invention will now be described with reference to the accompanying drawings. Figure 1 is an overall view of an offshore wind power generation facility 20 to which an underwater cable inspection device 10 according to an embodiment of the present invention is applied. The offshore wind power generation facility 20 shown in Figure 1 is of a floating type, but the embodiment can also be applied to bottom-mounted offshore wind power generation facilities. Thus, the offshore wind power generation facility 20 includes blades 25, a tower 26, a nacelle 30, a hub 21, and a floating body 22.

The blades 25 are connected to a hub 21 at the tip of the rotor shaft (not shown) and are arranged radially. The pitch angle of these blades 25 is adjusted with respect to the inflowing wind direction so that the fluid energy of the wind can be efficiently converted into rotational energy. The nacelle 30 houses various components that convert the rotational energy into electrical energy. The nacelle 30 is mounted on the top of the tower 26 via a yaw drive unit (not shown) that automatically makes the blades 25 follow the wind direction.

The float 22 to which the base end of the tower 26 is fixed is connected to a mooring line 23 extending from a foundation 24 built on the seabed 27 and is configured to be exposed above the sea surface. The mooring line 23 is a huge metal chain that anchors the float 22 to the seabed 27, and multiple mooring lines are provided for each float 22.

An underwater cable 31 is connected to the offshore wind power generation facility 20, which transmits electrical energy generated at sea to a substation facility (not shown) on land. The underwater cable 31 is partially buoyed by a number of buoys 32 on the underwater path from the offshore wind power generation facility 20 to the installation point on the seabed 27, and is installed in a slack state. This allows the underwater cable 31 to follow the up and down movement of the floating body 22 on the sea, reducing the fluctuation range of the tension repeatedly acting on each part.

In addition to fatigue and deterioration over time due to the effects of tension, etc., the underwater cable 31 can be damaged by the attachment of sessile organisms such as barnacles, contact with ships such as fishing boats or floating objects, or by being bitten by marine organisms such as sharks. For this reason, an inspection device 10, which is an unmanned underwater vehicle (ROV) with additional functions, is used to periodically inspect the appearance of the underwater cable 31 to confirm its soundness. Then, as necessary, attachments are removed and simple repair work is carried out.

Figures 2 (A) and (B) are conceptual diagrams of the operation of bringing the inspection device 10 according to the embodiment close to the underwater cable 31 and clamping it. Figure 3 is a block diagram of the data processing unit 40 in the underwater cable inspection device 10 according to the embodiment. The configuration of the inspection device 10 is broadly classified into a mechanical unit (unmanned underwater vehicle 15, clamp meter 11, work robot 12) and a data processing unit 40.

The inspection device 10 thus comprises, in its mechanical section (Fig. 2), an unmanned submersible 15 and a clamp meter 11 that is clamped to the underwater cable 31 and detects the magnetic field 55 formed around it to obtain the current flowing through the underwater cable 31 as a detected waveform 56. Furthermore, in its data processing section 40 (Fig. 3), the inspection device 10 comprises a calculation section 47 that calculates the phase difference 58 between the detected waveform 56 and a reference waveform 57, and a position identification section 48 that identifies the inspection position on the underwater cable 31 based on the phase difference 58.

The unmanned submersible 15 moves underwater unmanned by autonomous control or remote control. As shown in FIG. 3, the data processing unit 40 of the unmanned submersible 15 has a receiving unit 41a (41) that receives an operation signal 51a (51) from the unmanned submersible 15, and a drive control unit 42a (42) that outputs a drive signal 52a (52) that drives various motors that provide propulsion force to the unmanned submersible 15 underwater based on this operation signal 51a.

Such a data processing unit 40 may be placed in the unmanned submersible 15, or in a mother ship 35 that accompanies the unmanned submersible 15 and navigates freely on the ocean. When the unmanned submersible 15 accompanies the mother ship 35, the two are connected by a line 36 that transmits an operation signal 51 or a drive signal 52 and supplies power to the motors.

The unmanned underwater vehicle 15 is moved freely underwater, and the inspection device 10 performs inspection work on the underwater cable 31. Inspection of the underwater cable 31 includes observing and removing/cleaning any foreign objects attached thereto, discovering any damage that has occurred, and performing simple repairs. The inspection device 10 may be dispatched directly from land to the underwater cable 31 of the offshore wind power generation facility 20, or it may be transported from land to a mother ship 35 and dispatched to the underwater cable 31. The inspection device 10 may be dispatched directly from the offshore wind power generation facility 20, or, if an offshore substation is installed, may be dispatched from the substation.

In addition, when a large number of offshore wind power generation facilities 20 are lined up in the ocean, the mother ship 35 patrols these offshore wind power generation facilities 20 and inspects the underwater cables 31 of each. Alternatively, multiple mother ships 35 may be dispatched and multiple unmanned submersibles 15 may be associated with each mother ship 35 to inspect the offshore wind power generation facilities 20 in coordination with each other.

As shown in Figure 2 (A), the inspection device 10 approaches the underwater cable 31 with the clamp meter 11 in the open state. Then, as shown in Figure 2 (B), the inspection device 10 closes the clamp meter 11 when it comes close enough to touch the underwater cable 31. This means that the inspection device 10 is tied to the underwater cable 31, and even if the unmanned submersible 15 is stopped, it will not be swept away by ocean currents and the inspection point will not be lost. Furthermore, the clamp meter 11 can withstand the reaction force when the work robot 12 presses the underwater cable 31.

Furthermore, as shown in FIG. 2(B), the clamp meter 11 in the closed state detects the magnetic flux formed in the magnetic circuit around the underwater cable 31 by the clamp with a coil (not shown) wound around this magnetic circuit. In this way, the clamp meter 11 in the closed state detects the magnetic field 55 formed by the current (AC current) flowing through the underwater cable 31, and obtains the current (AC current) flowing through the underwater cable 31 as a detected waveform 56 based on this detected magnetic field 55.

As shown in FIG. 3, the data processing unit 40 of the clamp meter 11 is composed of an acquisition unit 46 that acquires a reference waveform 57 of the current flowing at the reference position 38 (FIG. 1) of the underwater cable 31, a calculation unit 47 that compares the detected waveform 56 of the clamp meter 11 with the acquired reference waveform 57 to calculate a phase difference 58 between them, and a position identification unit 48 that outputs a position signal 59 that identifies the distance from the reference position 38 of the underwater cable 31 to the inspection position of the inspection device 10 based on this phase difference 58. When the unmanned submersible 15 is accompanied by a mother ship 35, the reference position 38 and the mother ship 35 are connected by a line 37 that transmits the reference waveform 57 of the current flowing at the reference position 38 of the underwater cable 31.

Figure 4 is an explanatory diagram of the derivation principle of the position signal 59 indicating the inspection position of the underwater cable 31. The propagation speed of the current flowing through the underwater cable 31 is finite. For this reason, a phase difference 58 proportional to the distance separating the AC reference waveform 57 acquired at the reference position 38 and the AC detection waveform 56 detected at the inspection position of the inspection device 10 is observed. Since the propagation speed of this current can be considered to be the speed of light, the position signal 59 of the inspection device 10 is the distance obtained by multiplying the phase difference 58 by the speed of light, plus the reference position 38.

The reference position 38 can be set at any position on the underwater cable 31. The reference waveform 57 is the current waveform at this reference position 38, so it is possible to use the actual measurement at the reference position 38 using a current sensor such as a clamp meter.

The current (AC) passed through the underwater cable 31 is either the current generated by the offshore wind power generation facility 20 or a high-frequency current dedicated to inspection. Alternatively, this high-frequency current can be superimposed on the current generated by the offshore wind power generation facility 20.

Returning to FIG. 2, the explanation will continue. The inspection device 10 further includes, as a mechanical part, a work robot 12 that works on the underwater cable 31. A specific example of work performed by such a work robot 12 is cleaning. As illustrated in FIG. 2(B), the work robot 12 includes a multi-joint arm 16 and a rotating brush 17 provided at the tip of the multi-joint arm 16. Note that instead of the rotating brush 17, a water jet or the like may be provided at the tip of the multi-joint arm 16 for cleaning.

In addition to barnacles, other examples of attachments that can be removed during cleaning using such a rotating brush 17 include seaweed such as moss, aquatic organism eggs, man-made objects such as garbage, limescale, oil, sludge, and dust. The data processing unit 40 (Fig. 3) of the working robot 12 has a receiving unit 41b (41) that receives an operation signal 51b (51) from the working robot 12, and a drive control unit 42b (42) that outputs a drive signal 52b (52) that drives various motors to operate the working robot 12 based on this operation signal 51b. This operation signal 51b changes the position and posture of the tip tool (rotating brush 17) of the working robot 12, and imparts an operation to the tip tool (rotating brush 17).

The rotating brush 17 for cleaning purposes has been given as an example of the tip tool of the work robot 12, but this is not limited thereto, and a camera for observing and detecting foreign objects and damage, tools for easily repairing damage, etc. may also be used. Furthermore, a surveillance camera (not shown) for monitoring the work of such a work robot 12 is provided on the inspection device 10. Furthermore, the work robot 12 is not limited to being a single unit, and multiple work robots 12 may be provided.

The steps of the underwater cable inspection method according to the embodiment and the algorithm of the underwater cable inspection program will be described based on the flowchart in Figure 5 (see Figures 2 and 3 as appropriate). First, as shown in Figure 2 (A), the unmanned submersible 15 is operated to approach the underwater cable 31 (S11). Then, as shown in Figure 2 (B), the clamp meter 11 provided on the unmanned submersible 15 is clamped to the underwater cable 31 (S12). Then, the work robot 12 is operated to perform work on the underwater cable 31 (S13).

Next, the magnetic field 55 formed around the underwater cable 31 is detected by the clamp meter 11 (S14), and the current flowing through the underwater cable 31 is obtained as a detected waveform 56 (S15). At the same time, a reference waveform 57 of the current flowing through the reference position 38 of the underwater cable 31 is obtained (S16).

Next, the detected waveform 56 is compared with the reference waveform 57 to calculate the phase difference 58 between them (S17). Then, based on this phase difference 58, the inspection position of the inspection device 10 on the underwater cable 31 is identified (S18). Then, steps (S13) to (S18) are repeated while maneuvering the unmanned submersible 15 until the series of inspection tasks is completed (S19 No, Yes, END).

The above-described embodiments of the underwater cable inspection device, the underwater cable inspection method, and the underwater cable inspection program are shown as being applied to offshore wind power generation facilities, but the applications to which the present invention can be applied are not particularly limited, and the present invention can be applied to underwater cables for various purposes.

According to at least one of the embodiments of the underwater cable inspection device described above, by combining an unmanned underwater vehicle with a clamp meter, an underwater cable inspection technique is provided that prevents the device from being swept away by the tide and losing sight of the inspection point, and further enables the inspection position to be identified.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments and their modifications are within the scope of the invention and its equivalents as set forth in the claims, as well as the scope and spirit of the invention.

The underwater cable inspection device described above is equipped with a control device that is a highly integrated processor such as a dedicated chip, FPGA (Field Programmable Gate Array), GPU (Graphics Processing Unit), or CPU (Central Processing Unit), a storage device such as ROM (Read Only Memory) or RAM (Random Access Memory), an external storage device such as HDD (Hard Disk Drive) or SSD (Solid State Drive), a display device such as a display, and a communication I/F, and can be realized with a hardware configuration using a normal computer. Therefore, the components of the underwater cable inspection device can also be realized by a computer processor and can be operated by an underwater cable inspection program.

The underwater cable inspection program is provided by being pre-installed in a ROM or the like. Alternatively, the program may be provided by being stored in a computer-readable storage medium such as a CD-ROM, CD-R, memory card, DVD, or flexible disk (FD) in the form of an installable or executable file.

The underwater cable inspection program according to this embodiment may be stored on a computer connected to a network such as the Internet and provided by downloading it via the network. The underwater cable inspection device may also be configured by combining separate modules that independently perform the functions of the components and are interconnected via a network or dedicated lines.

10...Inspection device for underwater cables, 11...Clamp meter, 12...Work robot, 15...Unmanned underwater vehicle, 16...Articulated arm, 17...Rotating brush, 20...Offshore wind power generation equipment, 21...Hub, 22...Float, 23...Mooring line, 24...Foundation, 25...Blade, 26...Tower, 27...Seabed, 30...Nacelle, 31...Underwater cable, 32...Buoy, 35...Mother ship, 36...La In, 37...line, 38...reference position, 40...data processing unit, 41 (41a, 41b)...receiving unit, 42 (42a, 42b)...drive control unit, 46...acquisition unit, 47...calculation unit, 48...position identification unit, 51 (51a, 51b)...operation signal, 52 (52a, 52b)...drive signal, 55...magnetic field, 56...detection waveform, 57...reference waveform, 58...phase difference, 59...position signal.

Claims (7)

a clamp meter that is provided in an unmanned submersible that performs visual inspection of an underwater cable , the clamp meter being clamped to the underwater cable and detecting a magnetic field formed around the underwater cable to obtain a detected waveform of a current flowing through the underwater cable;
a calculation unit that calculates a phase difference between the detection waveform and a reference waveform;
a position identification unit that identifies an inspection position on the underwater cable based on the phase difference ,
The data processing unit in which the calculation unit and the position identification unit are provided is an underwater cable inspection device that is installed on the unmanned submersible vehicle or a mother ship that navigates freely on the ocean . 2. The underwater cable inspection device according to claim 1,
An underwater cable inspection device provided on an unmanned submersible vehicle and equipped with a work robot that performs work on the underwater cable. The underwater cable inspection device according to claim 1 or 2,
An underwater cable inspection device, wherein the reference waveform is obtained by actually measuring an arbitrary reference position on the underwater cable, which is different from the position of the clamp meter of the unmanned submersible , using another clamp meter. The underwater cable inspection device according to any one of claims 1 to 3,
An underwater cable inspection device, in which the current flowing from an offshore wind power generation facility to the underwater cable is a wind-generated current, a high-frequency current dedicated to inspection and having a higher frequency than the wind-generated current, or the high-frequency current is superimposed on the wind-generated current. The underwater cable inspection device according to any one of claims 1 to 4,
The unmanned underwater vehicle is an underwater cable inspection device that moves while being tethered by a line to a mother ship that navigates freely on the ocean. a clamp meter provided on an unmanned underwater vehicle for performing visual inspection of an underwater cable clamping the underwater cable;
a step in which the clamp meter detects a magnetic field formed around the underwater cable and outputs a detection waveform of a current flowing through the underwater cable;
A calculation unit calculates a phase difference between the detected waveform and a reference waveform;
a position identifying unit identifying an inspection position on the underwater cable based on the phase difference. A computer installed on an unmanned underwater vehicle or a mother ship that navigates freely on the ocean, which performs visual inspection of underwater cables ,
A clamp meter provided on the unmanned submersible is clamped to an underwater cable,
a clamp meter is used to detect a magnetic field formed around the underwater cable, thereby obtaining a current flowing through the underwater cable as a detection waveform;
A phase difference between the detected waveform and a reference waveform is calculated;
An underwater cable inspection program that identifies an inspection position on the underwater cable based on the phase difference.

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