Underwater cable inspection device, method and program

Abstract

To provide an inspection technique for an underwater cable with which no inspection portion is lost when a device is swept away by a tidal wave and an inspection position can be specified.SOLUTION: An inspection device 10 includes: an unmanned submarine vehicle 15; a clamp meter 11 that clamps to an underwater cable 31 to acquire a current flowing in the underwater cable 31 as a detection waveform; an arithmetic unit for calculating a phase difference between the detected waveform of the clamp meter 11 and a reference waveform; and a position specifying unit 48 for specifying an inspection position in the underwater cable 31 based on the phase difference.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] An embodiment of the present invention relates to a technique for inspecting an underwater cable using an unmanned underwater vehicle. [Background technology]

[0002] 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 perpetually. The winds are stronger on the sea than on land, there are no obstacles and the wind is stable, and because it is far from residential areas and noise problems are less likely to occur, it is possible to install large wind turbines 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 a fixed-bottom type that fixes the wind turbine to the seabed, so a floating type that floats the wind turbine on the sea surface is used.

[0003] In such floating offshore wind power generation facilities, 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 movements 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-080581 A Summary of the Invention [Problem to be solved by the invention]

[0005] To promote such offshore wind power generation facilities, it is important to establish a method for inspecting and maintaining underwater cables. The use of remotely operated vehicles (ROVs) is one way of streamlining the conventional inspection and maintenance work performed by divers. However, when an ROV works underwater, it is necessary to establish a method to prevent it from being swept away by the tide and losing sight of the inspection point. Furthermore, it is also necessary to establish a method to identify the inspection position of a cable with flexure that cannot be fully recognized by the underwater position information of the ROV.

[0006] An embodiment of the present invention has been made taking these circumstances into consideration, and aims to provide an underwater cable inspection technique that prevents the inspection point from being lost due to the device being swept away by the tidal current, and that makes it possible to identify the inspection position. [Means for solving the problem]

[0007] In the underwater cable inspection device according to the embodiment, Conduct visual inspection of underwater cables Installed on an unmanned underwater vehicle The above The present invention comprises a clamp meter that is clamped to an underwater cable and detects a magnetic field formed around the underwater cable to obtain a current flowing through the underwater cable as a detection waveform, a calculation unit that calculates a phase difference between the detection waveform and a reference waveform, and a position identification unit that identifies an inspection position on the underwater cable based on the phase difference. A data processing unit in which the calculation unit and the position identification unit are provided is disposed in the unmanned submersible. do. Effect of the Invention

[0008] According to an embodiment of the present invention, there is provided an underwater cable inspection technique that prevents the inspection point from being lost due to the device being swept away by the tidal current, and further enables the inspection position to be identified. [Brief description of the drawings]

[0009] [Figure 1] 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. [Diagram 2] 1A and 1B are conceptual diagrams illustrating the operation of bringing an inspection device according to an embodiment close to an underwater cable and clamping it. [Diagram 3] FIG. 2 is a block diagram of a data processing unit in the underwater cable inspection device according to the embodiment. [Figure 4] FIG. 4 is an explanatory diagram of the principle of derivation of a position signal indicating an inspection position of an underwater cable. [Diagram 5] 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 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. Although the offshore wind power generation facility 20 shown in Fig. 1 is a floating type, the embodiment can also be applied to a bottom-fixed type offshore wind power generation facility. 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.

[0011] The blades 25 are connected to a hub 21 at the tip of a rotor shaft (not shown) and arranged radially. The pitch angle of these blades 25 is adjusted with respect to the inflow direction of the wind 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.

[0012] The floating body 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 floating body 22 to the seabed 27, and multiple mooring lines 23 are provided for each floating body 22.

[0013] An underwater cable 31 that transmits electrical energy generated at sea to a substation (not shown) on land is connected to the offshore wind power generation facility 20. The underwater cable 31 is partially given buoyancy by a number of buoys 32 in the underwater path from the offshore wind power generation facility 20 to the installation point on the seabed 27, and is laid 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.

[0014] In addition to fatigue and deterioration over time due to the action of tension, 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 bites 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 check its soundness. Then, as necessary, attachments are removed and simple repair work is performed.

[0015] 2(A) and (B) are conceptual diagrams showing the operation of bringing the inspection device 10 according to the embodiment close to the underwater cable 31 and clamping it. Fig. 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 roughly classified into a mechanical unit (unmanned submersible 15, clamp meter 11, work robot 12) and the data processing unit 40.

[0016] Thus, the inspection device 10 includes, 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 a 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 includes a calculation section 47 that calculates a phase difference 58 between the detected waveform 56 and a reference waveform 57, and a position identification section 48 that identifies an inspection position on the underwater cable 31 based on the phase difference 58.

[0017] 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) of the unmanned submersible 15, and a drive control unit 42a (42) that outputs a drive signal 52a (52) that drives various motors that provide propulsive force to the unmanned submersible 15 underwater, based on this operation signal 51a.

[0018] Such a data processing unit 40 may be disposed in the unmanned submersible 15, or in a mother ship 35 that navigates freely on the ocean accompanying the unmanned submersible 15. When the unmanned submersible 15 accompanies the mother ship 35, the two are connected by a line 36 for transmitting operation signals 51 or drive signals 52 and for supplying power to the motors.

[0019] The unmanned submersible 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 observation, removal, and cleaning of attached foreign matter, discovery of damage and simple repair, etc. The inspection device 10 may be dispatched directly from land to the underwater cable 31 of the offshore wind power generation facility 20, or 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 may be dispatched from an offshore substation if one is installed.

[0020] Furthermore, 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 each of the underwater cables 31. Alternatively, multiple mother ships 35 may be dispatched and multiple unmanned submersibles 15 accompanying each may be coordinated to inspect the offshore wind power generation facilities 20.

[0021] As shown in Fig. 2(A), the inspection device 10 approaches the underwater cable 31 with the clamp meter 11 in the open state. Then, as shown in Fig. 2(B), the inspection device 10 closes the clamp meter 11 when it comes close enough to come into contact with the underwater cable 31. This ties the inspection device 10 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.

[0022] 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.

[0023] 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 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. Note that 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.

[0024] 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 regarded as 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.

[0025] The reference position 38 can be set at any position on the underwater cable 31. Since the reference waveform 57 is a current waveform at this reference position 38, it is possible to use a waveform actually measured at the reference position 38 using a current sensor such as a clamp meter.

[0026] The current (AC) flowing through the underwater cable 31 may be a current generated by the offshore wind power generation facility 20 or a high-frequency current dedicated for inspection. Alternatively, this high-frequency current may be superimposed on the current generated by the offshore wind power generation facility 20.

[0027] Returning to Fig. 2, the explanation will continue. The inspection device 10 further comprises, as a mechanical section, a working robot 12 that works on the underwater cable 31. A specific example of work performed by such a working robot 12 is cleaning. As illustrated in Fig. 2(B), the working robot 12 comprises 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.

[0028] In addition to barnacles, other examples of adhesions that can be removed during cleaning using the rotating brush 17 include seaweed such as moss, eggs of aquatic organisms, 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. The position and posture of the tip tool (rotating brush 17) of the working robot 12 are changed by this operation signal 51b, and the tip tool (rotating brush 17) is caused to operate.

[0029] Although a rotating brush 17 for cleaning purposes has been given as an example of the tip tool of the working robot 12, the present invention is not limited to this, and a camera for observing and finding foreign objects and damage, a tool for easily repairing damage, etc. may also be used. Furthermore, a surveillance camera (not shown) for monitoring the work of such a working robot 12 is provided on the inspection device 10. Furthermore, the working robot 12 is not limited to being a single machine, and multiple working robots may be provided.

[0030] The steps of the underwater cable inspection method according to the embodiment and the algorithm of the underwater cable inspection program will be described with reference to the flowchart in Fig. 5 (see Figs. 2 and 3 as appropriate). First, as shown in Fig. 2(A), unmanned submersible 15 is operated to approach underwater cable 31 (S11). Then, as shown in Fig. 2(B), clamp meter 11 provided on unmanned submersible 15 is clamped to underwater cable 31 (S12). Then, work robot 12 is operated to perform work on underwater cable 31 (S13).

[0031] 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).

[0032] 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, (S13) to (S18) are repeated while maneuvering the unmanned submersible 15 until a series of inspection tasks is completed (S19 No, Yes, END).

[0033] The embodiments of the underwater cable inspection device, the underwater cable inspection method, and the underwater cable inspection program described above show their application 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.

[0034] According to at least one of the embodiments of the underwater cable inspection device described above, by combining an unmanned submersible with a clamp meter, an underwater cable inspection technology is provided that prevents the device from being swept away by currents and losing sight of the inspection point, and further makes it possible to identify the inspection position.

[0035] Although some 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 included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention.

[0036] The underwater cable inspection device described above includes a control device with 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 be realized by a computer processor and can be operated by an underwater cable inspection program.

[0037] 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.

[0038] 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 connected to each other via a network or dedicated lines. [Explanation of symbols]

[0039] 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

1. A clamp meter that is provided in an unmanned submersible that performs visual inspection of an underwater cable, the clamp meter clamping to the underwater cable and detecting the magnetic field formed around the cable to obtain a detected waveform of the 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. 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.

3. 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.

4. 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.

5. 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.

6. A step of clamping a clamp meter provided on an unmanned underwater vehicle that performs a visual inspection of an underwater cable to 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.

7. A computer installed in an unmanned underwater vehicle or a mother ship that freely navigates on the ocean, which performs visual inspection of an underwater cable, 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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