Diagnostic method, diagnostic program, and diagnostic device

Abstract

A diagnosis method for diagnosing the state of a cable (40) includes: acquiring measured values of temperatures of a portion of the cable (40) to be diagnosed and portions other than the portion to be diagnosed; and a diagnosis condition that is applied to diagnosis based on the change over time of the temperature of the portion of the cable 40 to be diagnosed and the portion other than the portion of the cable 40 to be diagnosed when the amount of change of the temperature of the portion of the cable 40 to be diagnosed and the amount of change over time of the temperature of the portion other than the portion of the cable 40 to be diagnosed satisfy the diagnosis condition. If the temperature of the portion to be diagnosed satisfies a diagnosis condition applied to diagnosis based on the temperature of the portion to be diagnosed of the cable 40, it is determined that the state of the portion to be diagnosed of the cable 40 is abnormal.

Description

[0001] Cross-reference to Related Applications

[0002] This application claims priority to Japanese Patent Application No. 2022-203631 (filed on December 20, 2022), the entire disclosure of which is incorporated herein by reference for all purposes. Technical Field

[0003] The present invention relates to a method, program, and apparatus for diagnosing the state of a submarine cable. Background Art

[0004] Currently, a method is known in which the thermal resistance of the ground surrounding a submarine cable is calculated based on the temperature and current of the submarine cable over time, and the covering height of the submarine cable is estimated based on the thermal resistance of the ground, thereby monitoring the submarine cable (see, for example, Patent Document 1).

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2016-201989 Summary of the Invention

[0006] The state of the cable is determined not only based on the covering height of the sand or the like on the ground covering the cable when the cable is buried in the seabed, but also based on other various factors such as damage to the outer covering of the cable or disconnection of the cable. In the diagnosis of the state of the cable, it is required to consider various factors.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a diagnostic method, program, and apparatus capable of improving the diagnostic accuracy of the state of the cable.

[0008] (1) The diagnostic method according to several embodiments is a diagnostic method for diagnosing the state of a cable including a diagnostic target portion and a portion other than the diagnostic target portion. The diagnostic target portion corresponds to a part of the temperature measurement target portion of the cable.

[0009] The portion other than the diagnostic target portion corresponds to a measurement target portion different from the measurement target portion corresponding to the diagnostic target portion. The diagnostic method includes the following steps:

[0010] Obtain a measured value of the temperature of the measurement object part corresponding to the diagnostic object part of the cable as the temperature of the diagnostic object part of the cable; obtain a measured value of the temperature of the measurement object part corresponding to the diagnostic object part of the cable as the temperature of the part of the cable other than the diagnostic object part; and when the change amounts of the temperatures of the diagnostic object part of the cable and the part other than the diagnostic object part respectively satisfy the diagnostic conditions applicable to the diagnosis based on the changes in the temperatures of the diagnostic object part of the cable and the part other than the diagnostic object part over time, and the temperature of the diagnostic object part satisfies the diagnostic conditions applicable to the diagnosis based on the temperature of the diagnostic object part of the cable, determine that the state of the diagnostic object part is abnormal. Thus, the states of the respective parts of the cable can be continuously diagnosed. In addition, the influence of environmental changes is weakened in the diagnosis of the states of the respective parts of the cable. As a result, the diagnostic accuracy of the states of the respective parts of the cable is improved.

[0011] (2) Based on the above (1), the diagnostic method according to an embodiment may include the following steps: after determining that the change amounts of the temperatures of the diagnostic object part and the part other than the diagnostic object part respectively satisfy the diagnostic conditions applicable to the diagnosis based on the changes in the temperatures of the diagnostic object part of the cable and the part other than the diagnostic object part over time, determine whether the temperature of the diagnostic object part satisfies the diagnostic conditions applicable to the diagnosis based on the temperature of the diagnostic object part of the cable. Thus, the states of the respective parts of the cable can be continuously diagnosed. In addition, the influence of environmental changes is weakened in the diagnosis of the states of the respective parts of the cable. As a result, the diagnostic accuracy of the states of the respective parts of the cable is improved.

[0012] (3) Based on the above (2), the diagnostic method according to an embodiment may include the following steps: change the part other than the diagnostic object part to a different part of the cable in such a way that the change amounts of the temperatures of the diagnostic object part and the part other than the diagnostic object part respectively satisfy the diagnostic conditions applicable to the diagnosis based on the changes in the temperatures of the diagnostic object part of the cable and the part other than the diagnostic object part over time. Thus, even without geological data, it is possible to assume different geology and diagnose the state of the cable 40. As a result, the diagnostic accuracy of the state of the cable 40 is improved.

[0013] (4) As an implementation, based on any one of the above (1) to (3), the diagnostic conditions applied to the diagnosis of the temperature change of each of the diagnostic object part of the cable and the part other than the diagnostic object part over time may include conditions based on the value representing the state of the diagnostic object part considering the state of the part of the cable other than the diagnostic object part calculated based on the change amounts of the temperature of the diagnostic object part and the temperature of the part other than the diagnostic object part respectively. The diagnostic conditions applied to the diagnosis based on the temperature of the diagnostic object part of the cable may include conditions based only on the change of the temperature of the diagnostic object part over time. Thereby, the influence of environmental changes is weakened in the diagnosis of the state of each part of the cable. As a result, the diagnostic accuracy of the state of each part of the cable is improved.

[0014] (5) As an implementation, based on the above (4), the conditions based only on the change of the temperature of the diagnostic object part over time may include that the temperature of the diagnostic object part of the cable deviates from the determination range. The determination range may be set based on the magnitude of the current flowing through the cable and the environment around the diagnostic object part of the cable. Thereby, the influence of environmental changes is weakened in the diagnosis of the state of each part of the cable. As a result, the diagnostic accuracy of the state of each part of the cable is improved.

[0015] (6) As an implementation, based on the above (4) or (5), the value representing the state of the diagnostic object part considering the state of the part of the cable other than the diagnostic object part may be calculated as the absolute value of the difference between the value obtained by multiplying the change amount of the temperature of the diagnostic object part by the coefficient corresponding to the diagnostic object part of the cable and the value obtained by multiplying the change amount of the temperature of the part other than the diagnostic object part by the coefficient corresponding to the part of the cable other than the diagnostic object part. The coefficient corresponding to the diagnostic object part of the cable may be set based on the environment around the diagnostic object part of the cable. The coefficient corresponding to the part of the cable other than the diagnostic object part may be set based on the environment around the part of the cable other than the diagnostic object part. The conditions based on the value representing the state of the diagnostic object part considering the state of the part of the cable other than the diagnostic object part may include that the value representing the state of the diagnostic object part considering the state of the part of the cable other than the diagnostic object part is greater than or equal to the determination value. The determination value may be set based on the coefficient corresponding to the diagnostic object part of the cable and the coefficient corresponding to the part of the cable other than the diagnostic object part. Thereby, the influence of environmental changes is weakened in the diagnosis of the state of each part of the cable. As a result, the diagnostic accuracy of the state of each part of the cable is improved.

[0016] (7) As an embodiment, based on any one of the above (4) to (6), it can be configured to correct the value representing the state of the diagnosed object part in consideration of the state of the part of the cable other than the diagnosed object part based on the difference between the time when the temperature of the diagnosed object part of the cable starts to change and the time when the temperature of the part of the cable other than the diagnosed object part starts to change. Thus, the state of each part of the cable is diagnosed considering the heat generation of the cable 40. As a result, the diagnostic accuracy of the state of the cable is improved.

[0017] (8) The diagnostic programs according to several embodiments cause a computer to execute the diagnostic method according to any one of the above (1) to (7). Thus, the state of each part of the cable can be continuously diagnosed. In addition, the influence of environmental changes is reduced in the diagnosis of the state of each part of the cable. As a result, the diagnostic accuracy of the state of each part of the cable is improved.

[0018] (9) The diagnostic devices according to several embodiments include a control unit that executes the diagnostic method according to any one of the above (1) to (7). Thus, the state of each part of the cable can be continuously diagnosed. In addition, the influence of environmental changes is reduced in the diagnosis of the state of each part of the cable. As a result, the diagnostic accuracy of the state of each part of the cable is improved.

[0019] Effects of the Invention

[0020] According to the diagnostic method, diagnostic program, and diagnostic device according to the present invention, the diagnostic accuracy of the state of the cable is improved. Description of the Drawings

[0021] Figure 1 It is a schematic diagram showing a structural example of a diagnostic system according to an embodiment.

[0022] Figure 2 It is a block diagram showing a structural example of a diagnostic system according to an embodiment.

[0023] Figure 3 It is a schematic diagram showing a structural example of a cable.

[0024] Figure 4A It is a cross-sectional view showing an example of a cable buried underground.

[0025] Figure 4B It is a cross-sectional view showing an example of a cable substantially exposed on the seabed.

[0026] Figure 5 It is a flowchart showing a flow example of a diagnostic method according to an embodiment.

[0027] Figure 6 It is a schematic diagram showing a structural example of a cable passing through various different geological formations.

[0028] Figure 7 This is a diagram showing an example of the relationship between the buried state of a cable and the temperature distribution.

[0029] Figure 8A This is a graph showing an example of the change in the heating temperature of a cable over time.

[0030] Figure 8B This is a graph showing an example of the change in the temperature at location X of a cable over time.

[0031] Figure 8C This is a graph showing an example of the change in the temperature at location Y of a cable over time. Detailed implementation

[0032] One embodiment of the present invention relates to a diagnostic system 1 (refer to Figure 1 ) for diagnosing the state of a submarine cable connected to an offshore wind power generation device or the like. Hereinafter, an embodiment of the diagnostic system 1 will be described in comparison with a comparative example.

[0033] (Comparative example)

[0034] As a comparative example, consider a method for diagnosing a submarine cable by visual confirmation based on a diver or confirmation by a device such as sonar or ROV (Remotely Operated Vehicle). The diagnostic method involved in the comparative example is not a method that can be always executed. For example, it is executed at regular intervals such as once a year or once every few years. The state of the submarine cable sometimes suddenly changes due to natural phenomena including excavation caused by ocean currents or typhoons or accumulation caused by earthquakes, or human activities including contact with anchors or fishing gear. The diagnostic method involved in the comparative example cannot immediately detect a sudden change in the state of the submarine cable. It is difficult to determine the cause of the state change because the change in the state of the submarine cable cannot be immediately detected. In addition, when the submarine cable is in a state of heating due to buckling or the like, the amount of electric power that can be transmitted is limited or the submarine cable itself ages due to the failure to detect the state change. In addition, the power loss increases due to heating.

[0035] As other problems of the diagnostic method involved in the comparative example, it is costly or time-consuming to perform the diagnosis. In addition, the diagnostic method involved in the comparative example cannot be executed when the state of the ocean becomes bad due to bad weather or the like. In addition, in the diagnostic method of the first comparative example, the diagnostic accuracy based on visual confirmation is reduced due to the accumulation of deposits or the attachment of marine organisms in the part where the submarine cable is buried.

[0036] Therefore, the present invention provides the following diagnostic system 1 (refer to Figure 1) A description will be given, that is, as the state of the submarine cable, it is possible to continuously and simply or without visual inspection diagnose various states such as the covering height of the sand and soil on the ground covering the submarine cable when the submarine cable is buried under the sea floor, damage to the outer covering of the submarine cable, or breakage of the submarine cable.

[0037] (Embodiment of the present invention)

[0038] As Figure 1 shown, the diagnostic system 1 according to one embodiment includes a diagnostic device 10, a temperature measuring device 20, and a display device 30. The diagnostic system 1 diagnoses the state of the cable 40.

[0039] In the present embodiment, the cable 40 is a submarine cable buried underground 80 in such a way as to pass through the sea floor 81 for the purpose of transmitting the power generated by the ocean wind power generation device 70 to the land 82, for communication between the ocean wind power generation device 70 and devices such as the diagnostic device 10 on the land 82, or for other various purposes. The target for which the cable 40 transmits power or the target to which the cable 40 is connected by communication is not limited to the devices on the land 82, and may also be devices on the sea or in the middle of the sea.

[0040] Due to the unevenness of the sea floor 81, the cable 40 includes a part buried underground 80 and a part exposed from underground 80 to the sea 84 due to the excavation of the sea floor 81. The part buried underground 80 is exemplified as the buried part 51 and the buried part 53. The part exposed from underground 80 to the sea 84 is exemplified as the exposed part 52. The cable 40 includes a part that is not exposed in the sea 84 but has a shallower burial depth relative to the underground 80. The part with a shallower burial depth relative to the underground 80 is exemplified as the shallow burial part 54.

[0041] The exposed part 52 or the shallow burial part 54 may sometimes be generated due to a phenomenon such as excavation caused by the sea floor 81 being eroded by ocean currents, which makes the shape of the sea floor 81 become a concave part. The exposed part 52 or the shallow burial part 54 may also sometimes be generated due to the floating of the cable 40 caused by the movement of the sea floor 81 due to an earthquake or the like.

[0042] The cable 40 includes a part pulled out from underground 80 to the sea 84 for connection to the ocean wind power generation device 70. The part pulled out from underground 80 to the sea 84 is exemplified as the boundary part 55.

[0043] The submarine cable is liable to buckle or break due to the collision of fishing gear or an anchor or the like against the exposed part 52 or the shallow burial part 54. The diagnostic system 1 can diagnose whether the submarine cable has become a state of being exposed in the sea 84 or a state close to being exposed.

[0044] The temperature of the submarine cable is different when it is buried 80 underground, exposed 84 in the sea, or substantially exposed 84 in the sea. Therefore, for the diagnostic system 1 according to this embodiment, the diagnostic device 10 diagnoses whether the cable 40 is buried 80 underground or exposed 84 in the sea as the state of the cable 40 based on the temperature of at least a part of the cable 40. The diagnostic device 10 can not only diagnose the burial state of the cable 40, but also diagnose the heat generation state of the cable 40. The display device 30 displays the diagnostic result of the state of the cable 40.

[0045] (Structural example of diagnostic system 1)

[0046] Next, Figure 2 A structural example of the diagnostic system 1 shown by way of example will be described.

[0047] <Diagnostic device 10>

[0048] As described later, the diagnostic device 10 diagnoses the state of the cable 40 based on the temperature of each part of the cable 40 measured by the temperature measuring device 20, and displays the diagnostic result on the display device 30. As described later, for the measurement of the temperature of each part of the cable 40, it is premised on using the optical fiber connected to the cable 40 as a sensor. When measuring the temperature of each part of the cable 40 along the length direction of the cable 40, the optical fiber connected to the temperature measuring device 20 and along the cable 40 functions as a sensor. When the cable 40 is a submarine cable, the optical fiber that becomes an idle optical fiber among the optical fibers built in the cable 40 as described later can be used as a sensor.

[0049] The diagnostic device 10 includes a control unit 12, a storage unit 14, and an interface 16.

[0050] The control unit 12 controls each structural part of the diagnostic device 10. The control unit 12 can be configured to include a processor such as a CPU (Central Processing Unit). The control unit 12 can cause the processor to execute a prescribed program to implement a prescribed function.

[0051] The storage unit 14 can store various information for the operation of the control unit 12 or a program for implementing the function of the control unit 12, etc. The storage unit 14 can function as a working memory of the control unit 12. The storage unit 14 can be constituted by, for example, a semiconductor memory. The storage unit 14 can be configured to include a volatile memory or a non-volatile memory. The storage unit 14 can be configured as a non-temporary computer-readable storage medium. The storage unit 14 can be included in the control unit 12.

[0052] The storage unit 14 can store information during the burial of the cable 40. The information during the burial of the cable 40 may include the burial position or burial depth of the cable 40 when the cable 40 is normally buried. The information during the burial of the cable 40 may include the measured values of the temperatures of the respective parts of the cable 40 when no current flows through the cable 40 immediately after the cable 40 is normally buried or immediately after the cable 40 is normally maintained. The information during the burial of the cable 40 may include information related to the geology of the place where the cable 40 is buried. The information related to the geology may include the geological category or the underground thermal conductivity. The storage unit 14 can store information after the cable 40 is buried. The information after the cable 40 is buried may include the measured values of the temperatures of the respective parts of the cable 40 when current flows through the cable 40. The information after the cable 40 is buried may include data associating the magnitude of the current flowing through the cable 40, the magnitude of the voltage applied to the cable 40, and the temperatures of the respective parts of the cable 40. The storage unit 14 may include the characteristics of the temperature measurement of the cable 40.

[0053] The interface 16 is configured to include a communication device that connects the diagnostic device 10 to the temperature measurement device 20 or the display device 30 or the like in a communicable manner. The communication device can be configured to communicate, for example, based on mobile communication standards such as 4G (4th Generation) or LTE (Long Term Evolution) or 5G (5th Generation). The communication device can be configured to communicate, for example, based on the communication standard of LAN (Local Area Network). The communication device can be configured to communicate in a wired or wireless manner.

[0054] The interface 16 can be configured to include a display device. The display device can include various displays such as a liquid crystal display, for example. The interface 16 can be configured to include a voice output device such as a speaker. The interface 16 is not limited thereto and can also be configured to include various other output devices.

[0055] The interface 16 can be configured to include an input device that accepts input from a user. The input device can include a keyboard or physical keys, for example, and can also include a pointing device such as a touch panel or a touch sensor or a mouse. The interface 16 can be configured to include other computers or the diagnostic device 10. The input device is not limited to the above examples and can also be configured to include various other devices. The input device can be configured to be able to input parameters or the like for diagnosing the state of the cable 40 using the diagnostic device 10.

[0056] The diagnostic device 10 can be configured as a PC (Personal Computer) or can be configured as at least one server device. The diagnostic device 10 can be implemented by a cloud computing system.

[0057] <Temperature measurement device 20>

[0058] The temperature measuring device 20 measures the temperature of at least a part of the cable 40. The part of the cable 40 that is set as the object to be measured for temperature by the temperature measuring device 20 is also referred to as the measurement object part. In order to use the diagnostic system 1 to diagnose the overall buried condition or disconnection condition of a relatively long cable 40, etc., it is necessary to measure the temperatures of a plurality of parts of the cable 40 that are greater than or equal to several hundred points or several thousand points. The measurement object parts can be set at regular intervals such as 1 m intervals along the length direction of the cable 40, or can be set at irregular intervals. In the present embodiment, as Figure 3 illustrated by way of example, the cable 40 has an electric wire 41, an optical fiber 42, and a coating 43. The electric wire 41 and the optical fiber 42 are protected inside the coating 43. In the present embodiment, the temperature measuring device 20 measures the temperatures of the respective parts in the length direction of the cable 40 by using the optical fiber 42. The optical fiber 42 used for temperature measurement is also referred to as a DTS (Distributed Temperature Sensor).

[0059] Specifically, the temperature measuring device 20 sends pulsed light into the optical fiber 42. The pulsed light incident on the optical fiber 42 is scattered at various positions in the optical fiber 42 due to Raman scattering. The light scattered due to Raman scattering is also referred to as Raman scattered light. At least a part of the Raman scattered light returns to the incident side of the optical fiber 42. The temperature measuring device 20 acquires a signal based on the Raman scattered light that returns to the incident side of the optical fiber.

[0060] The Raman scattered light includes: Stokes light that is shifted to the longer wavelength side with respect to the wavelength of the incident pulsed light; and anti-Stokes light that is shifted to the shorter wavelength side with respect to the wavelength of the incident pulsed light. The intensity of each component of the Raman scattered light depends on the temperature of the optical fiber 42 at the position where the Raman scattering occurs. The temperature measuring device 20 can calculate the temperature of the optical fiber 42 at the position where the light signal is scattered by analyzing the Raman scattered light that returns due to reflection. In addition, the temperature measuring device 20 can calculate the position where the received light signal is reflected based on the time from when the optical signal is sent until the optical signal returns due to reflection. Therefore, the temperature measuring device 20 can calculate the temperature of the optical fiber 42 at each position of the optical fiber 42.

[0061] The temperature of each part of the optical fiber 42 is regarded as being substantially the same as the temperature of each part of the cable 40 corresponding to each part of the optical fiber 42. The temperature measuring device 20 can measure the temperature of each part of the cable 40 by measuring the temperature of each part of the optical fiber 42. In the present embodiment, the temperatures of the respective parts of the cable 40 are measured at 1 m intervals. The interval for measuring the temperature is not limited to 1 m, and can also be set to various lengths.

[0062] The temperature measurement device 20 can be configured to measure the temperature of the measurement target portion of the cable 40 using a temperature sensor different from the optical fiber 42 provided in the measurement target portion of the temperature of the cable 40. The temperature sensor can be installed outside the coating 43 of the cable 40 or buried inside the coating 43. The temperature sensor can be installed at the connection portion of the cable 40.

[0063] The temperature measurement device 20 is not limited to the measurement method using the optical fiber 42 or the measurement method using the temperature sensor, and can also be configured to measure the temperature of the measurement target portion of the cable 40 by various other methods.

[0064] <Display device 30>

[0065] The display device 30 displays the diagnostic result of the state of the cable 40 based on the diagnostic device 10. The display device 30 can display various data including the measurement result of the temperature of at least a part of the cable 40 or the change of the temperature measurement result over time. The display device 30 can include various displays such as a liquid crystal display, for example. The display device 30 can be included in the diagnostic device 10 as the display device of the interface 16 of the diagnostic device 10. The diagnostic device 10, the temperature measurement device 20, and the display device 30 can be integrally formed. A combination of a part of the diagnostic device 10, the temperature measurement device 20, and the display device 30 can be integrally formed. The diagnostic device 10, the temperature measurement device 20, and the display device 30 can be separately formed.

[0066] The diagnostic system 1 can have a speaker that outputs the diagnostic result of the state of the cable 40 in voice, or can have various other output devices. As a device for outputting the diagnostic result of the state of the cable 40, the diagnostic system 1 can have other output devices based on the display device 30, or can have other output devices instead of the display device 30.

[0067] (Operation example of the diagnostic system 1)

[0068] As described above, regarding the diagnostic system 1 according to the present embodiment, the diagnostic device 10 can diagnose the state of the diagnostic target portion of the cable 40 based on the measured value of the temperature of the measurement target portion of the cable 40.

[0069] For example Figure 4A and Figure 4B As shown, the heat transferred from the cable 40 to the sea 84 varies depending on the burial depth of the underground 80 of the cable 40. As Figure 4A illustrated by way of example, when the cable 40 is buried deep in the underground 80, the heat taken from the cable 40 is reduced due to the ocean current 85 in the sea 84. On the other hand, as Figure 4BFor example, when the cable 40 is about to emerge from underground 80 into the sea 84 or when the cable 40 emerges into the sea 84, the heat taken from the cable 40 increases due to a part of the ocean current 86 in the ocean current 85 in the sea 84 that is close to the cable 40. Since the sand and soil on the cable 40 decreases due to the abnormal burial of the cable 40, the cable 40 approaches or contacts the seawater. The cable 40 is deprived of heat by the seawater due to the cable 40 approaching or contacting the seawater. The cable 40 is deprived of heat by the seawater, resulting in a relatively lower temperature of the part of the cable 40 that is close to or in contact with the seawater compared to the temperature of the normally buried part of the cable 40. Therefore, the part of the diagnostic object part of the cable 40 where the temperature decreases is deprived of heat by the seawater, and it is determined that the cable 40 is in an abnormal burial state with a reduced amount of sand and soil on it. In Figure 4A and Figure 4B In the comparison, the closer the burial position of the diagnostic object part of the cable 40 is to the sea 84, the lower the temperature of the diagnostic object part of the cable 40. Therefore, the diagnostic device 10 can diagnose the burial position of each part of the cable 40 based on the temperature of each part of the cable 40.

[0070] In addition, when the cable 40 buckles or breaks, the resistance value of the electric wire 41 in the cable 40 may increase. The heat generation amount of the buckling part or the breaking part increases due to the increase in the resistance value of the electric wire 41. The temperature of the part in the cable 40 where the heat generation amount increases rises. The diagnostic device 10 can diagnose abnormalities such as buckling or breaking generated in each part of the cable 40 based on the temperature of each part of the cable 40.

[0071] Not limited to abnormalities such as the abnormal burial position of the cable 40 or the buckling or breaking of the cable 40, the diagnostic device 10 can also diagnose various other states of the cable 40. Next, an operation example of the diagnostic system 1 will be described.

[0072] <Diagnosis Based on the Temperature of the Diagnostic Object Part of the Cable 40>

[0073] The control unit 12 of the diagnostic device 10 obtains the measured value of the temperature of the diagnostic object part of the cable 40 from the temperature measuring device 20. The diagnostic object part is also referred to as the diagnostic object part.

[0074] When the temperature of the diagnostic target portion of the cable 40 is within a specified temperature range, the control unit 12 determines that the state of the diagnostic target portion of the cable 40 is normal. When the temperature of the diagnostic target portion of the cable 40 is not within the specified temperature range, the control unit 12 determines that the state of the diagnostic target portion of the cable 40 is abnormal. The specified temperature range for comparison with the temperature of the diagnostic target portion of the cable 40 is also referred to as the determination range. When the shallower the burial position of the cable 40, the lower the temperature of the cable 40, the control unit 12 may set only the lower limit of the determination range without setting the upper limit of the determination range. On the contrary, when the shallower the burial position of the cable 40, the higher the temperature of the cable 40, the control unit 12 may set only the upper limit of the determination range without setting the lower limit of the determination range.

[0075] The control unit 12 may set the determination range based on the magnitude of the current flowing through the cable 40. For example, the control unit 12 may set the determination range such that the higher the current flowing through the cable 40, the higher the central value of the determination range.

[0076] The control unit 12 may set the determination range based on the environmental state of the ground 80 where the diagnostic target portion of the cable 40 is buried or the environment of the sea 84 near the position where the diagnostic target portion of the cable 40 is buried. For example, the control unit 12 may set the determination range based on the geology of the position where the diagnostic target portion of the cable 40 is buried. The control unit 12 may set the determination range such that the higher the thermal conductivity of the geology where the diagnostic target portion of the cable 40 is buried, the lower the central value of the determination range. For example, the control unit 12 may set the determination range based on the seawater temperature near the position where the diagnostic target portion of the cable 40 is buried. The control unit 12 may set the determination range such that the lower the seawater temperature, the lower the central value of the determination range. For example, the control unit 12 may set the determination range based on the depth of the position where the diagnostic target portion of the cable 40 is buried. The control unit 12 may set the determination range such that the deeper the position where the diagnostic target portion of the cable 40 is buried, the more difficult it is considered for the temperature of the diagnostic target portion of the cable 40 to change, and the smaller the temperature range of the determination range. In other words, the control unit 12 may set the determination range based on the magnitude of the current flowing through the cable 40 and the environment around the diagnostic target portion of the cable 40.

[0077] The control unit 12 can set a determination range based on the measured value of the temperature of the diagnostic object portion of the buried cable 40 at that time. The control unit 12 can set a determination range based on the measured value of the temperature of the diagnostic object portion of the cable 40 when the state of the diagnostic object portion of the cable 40 was last confirmed to be normal. The control unit 12 can set a determination range based on the measured value of the temperature of the boundary portion 55 where the cable 40 is pulled out from the ground 80 into the sea 84. The control unit 12 can set a determination range based on statistical values such as the average value obtained by measuring the temperature of the diagnostic object portion of the cable 40 over a specified period. The determination range is not limited to the above examples and can also be set based on various other information.

[0078] The control unit 12 can calculate a value representing the state of the diagnostic object portion of the cable 40, such as an abnormality in the buried state of the cable 40 in the diagnostic object portion of the cable 40, based on the temperature of the diagnostic object portion of the cable 40. It may also cause an accident or dangerous phenomenon in the operation of equipment such as damage to a part of the cable 40 exposed from the seabed and caught on an anchor due to the occurrence of a burial abnormality or activities around the equipment. Therefore, the value representing the state of the diagnostic object portion of the cable 40 is also referred to as the risk level. The closer the state of the diagnostic object portion of the cable 40 is to being abnormal, the larger the value the control unit 12 calculates for the risk level. The closer the state of the diagnostic object portion of the cable 40 is to being normal, the smaller the value the control unit 12 calculates for the risk level. The control unit 12 can diagnose that the state of the diagnostic object portion of the cable 40 is abnormal when the risk level is greater than or equal to a specified threshold. The specified threshold for determining the risk level is also referred to as the risk level threshold.

[0079] The value of the risk level can be calculated as a value standardized in the range greater than or equal to 0 and less than or equal to 1. The control unit 12 can calculate the risk level in such a way that, in the normal state where the diagnostic object portion of the cable 40 is sufficiently buried at a deeper position in the ground 80, the value of the risk level representing the state of the diagnostic object portion of the cable 40 is set to 1 for calculation, and the shallower the position where the diagnostic object portion of the cable 40 is buried, the greater the value of the risk level becomes. The expression of the value of the risk level is not limited to the above example. If the degree of risk of the state of the cable 40 is grasped, the value of the risk level can be freely expressed including percentages, etc. In the following description, the value of the risk level is represented as a value standardized in the range greater than or equal to 0 and less than or equal to 1, and the closer the state of the diagnostic object portion of the cable 40 is to being normal, the closer it is to 0, and the closer the state of the diagnostic object portion of the cable 40 is to being abnormal, the closer it is to 1.

[0080] For example, when the risk level is greater than or equal to 0.5, the control unit 12 can output a warning indicating that the diagnostic target portion of the cable 40 is still buried but the burial position is shallow and close to the exposure to the sea 84. For example, when the risk level is greater than or equal to 0.95, the control unit 12 can determine that the diagnostic target portion of the cable 40 is exposed in the sea 84 and output information indicating an abnormal state of the diagnostic target portion of the cable 40. For example, when the burial depth of the diagnostic target portion of the cable 40 is about 50 cm, the control unit 12 can calculate the risk level in such a way that the risk level becomes 0.5. The control unit 12 can set risk level thresholds corresponding to multiple levels respectively in such a way that the state of the diagnostic target portion of the cable 40 can be diagnosed at multiple levels corresponding to the abnormal level. Numerical values such as 0.5 or 0.95 calculated by the control unit 12 as the risk level value corresponding to the abnormal state of the cable 40 and the like are not limited to the above numerical values. The control unit 12 can appropriately set the risk level value corresponding to the abnormal state of the cable 40 and the like.

[0081] The control unit 12 can set multiple diagnostic target portions of the cable 40 in order to diagnose the states of multiple portions of the cable 40, and diagnose the states of the respective multiple diagnostic target portions of the cable 40. The control unit 12 can set different determination ranges for at least some of the multiple diagnostic target portions of the cable 40. The control unit 12 can set the same determination range for at least some of the multiple diagnostic target portions of the cable 40.

[0082] As described above, the state of the diagnostic target portion of the cable 40 is diagnosed based on the measured value of the temperature of the diagnostic target portion of the cable 40. Thus, the states of the respective portions of the cable 40 are continuously diagnosed.

[0083] The control unit 12 can separately set a determination range or a risk level threshold for diagnosing the state of the cable 40 exposed in the sea 84 and a determination range or a risk level threshold for diagnosing the state of the cable 40 buckled or damaged. Thus, the control unit 12 can distinguishably diagnose whether the state of the cable 40 is an abnormality of being exposed in the sea 84 or an abnormality such as buckling or damage.

[0084] <Diagnosis Based on the Change in Temperature of Multiple Portions of the Cable 40 over Time>

[0085] Regarding the diagnostic system 1 according to the present embodiment, the diagnostic device 10 can perform diagnosis based on the change in temperature of multiple portions of the cable 40 over time. After the cable 40 is just laid, etc., the cable 40 is considered to be buried throughout the area. Even when a temperature determined to be an abnormal value is measured in this state, the state of the cable 40 can be diagnosed as the correct value of the temperature.

[0086] The control unit 12 of the diagnostic device 10 acquires the measured values of the temperatures of multiple parts of the cable 40 from the temperature measurement device 20. As the temperatures of the multiple parts of the cable 40, the control unit 12 acquires the measured values of the temperatures of the diagnostic target parts that are the objects to be diagnosed in the diagnostic state and the measured values of the temperatures of the parts other than the diagnostic target parts. The diagnostic target parts of the cable 40 correspond to a part of the temperature measurement target parts of the cable 40. The parts of the cable 40 other than the diagnostic target parts correspond to the temperature measurement target parts different from the temperature measurement target parts corresponding to the diagnostic target parts of the cable 40. The control unit 12 acquires the measured value of the temperature of the temperature measurement target part corresponding to the diagnostic target part of the cable 40 as the temperature of the diagnostic target part of the cable 40. The control unit 12 acquires the measured value of the temperature of the temperature measurement target part corresponding to the part of the cable 40 other than the diagnostic target part as the temperature of the part of the cable 40 other than the diagnostic target part. The part of the cable 40 other than the diagnostic target part may be a part that is separated from the diagnostic target part of the cable 40 by a specified distance along the cable 40. The part of the cable 40 other than the diagnostic target part in a certain period may be the diagnostic target part of the cable 40 in other periods. The part of the diagnostic target part of the cable 40 in a certain period may be the part of the cable 40 other than the diagnostic target part in other periods. In the case where the entire environment in which the cable 40 is buried changes, it is assumed that the temperatures of the multiple parts of the cable 40 change due to the influence of the environmental change. The control unit 12 can diagnose the state of the diagnostic target part of the cable 40 by comparing the change amount of the temperature of the diagnostic target part of the cable 40 with the change amount of the temperature of the part of the cable 40 other than the diagnostic target part.

[0087] For example, when the temperature of the part of the cable 40 other than the diagnostic target part does not change while the temperature of the diagnostic target part of the cable 40 changes, the control unit 12 can diagnose that the state of the diagnostic target part of the cable 40 has changed. For example, when the change amount of the temperature of the diagnostic target part of the cable 40 is greater than the change amount of the temperature of the part of the cable 40 other than the diagnostic target part before and after a specified time, the control unit 12 can diagnose that the state of the diagnostic target part of the cable 40 has changed. When the change amount of the temperature of the diagnostic target part of the cable 40 is greater than or equal to a specified threshold value, the control unit 12 can diagnose that the state of the diagnostic target part of the cable 40 is abnormal. The specified threshold value compared with the change amount of the temperature of the diagnostic target part of the cable 40 is also called the change amount threshold value.

[0088] The control unit 12 can, for example, calculate a value representing the state of the diagnostic object portion of the cable 40 by considering the respective change amounts of the temperature of the diagnostic object portion of the cable 40 and the temperature of the portion other than the diagnostic object portion, and taking into account the state of the portion other than the diagnostic object portion of the cable 40. The value representing the state of the diagnostic object portion that takes into account the state of the portion other than the diagnostic object portion of the cable 40 is a value that takes into account the relationship between the measured value and the reference value of the temperature of the portion other than the diagnostic object portion when determining the risk level based on the relationship between the measured value and the reference value of the temperature of the diagnostic object portion. The control unit 12 can diagnose whether the state of the diagnostic object portion of the cable 40 is abnormal based on the value representing the state of the diagnostic object portion of the cable 40 that takes into account the state of the portion other than the diagnostic object portion of the cable 40. For example, when the value representing the state of the diagnostic object portion of the cable 40 that takes into account the state of the portion other than the diagnostic object portion of the cable 40 is greater than or equal to the determination value, the control unit 12 can diagnose that the state of the diagnostic object portion of the cable 40 is abnormal.

[0089] The control unit 12 can calculate a value representing the state of the diagnostic object portion of the cable 40 that takes into account the state of the portion other than the diagnostic object portion of the cable 40 based on, for example, values obtained by weighting the change amount of the temperature of the diagnostic object portion and the change amount of the temperature of the portion other than the diagnostic object portion, respectively. The control unit 12 can weight by multiplying the change amount of the temperature of the diagnostic object portion by a coefficient corresponding to the diagnostic object portion. The control unit 12 can set a coefficient corresponding to the diagnostic object portion based on the environment around the location where the diagnostic object portion of the cable 40 is buried. The control unit 12 can weight by multiplying the change amount of the temperature of the portion other than the diagnostic object portion by a coefficient corresponding to the portion other than the diagnostic object portion. The control unit 12 can set a coefficient corresponding to the portion other than the diagnostic object portion based on the environment around the location where the portion other than the diagnostic object portion of the cable 40 is buried. That is, the control unit 12 can calculate the value representing the state of the diagnostic object portion of the cable 40 that takes into account the state of the portion other than the diagnostic object portion of the cable 40 as the absolute value of the difference between the value obtained by multiplying the change amount of the temperature of the diagnostic object portion by the coefficient corresponding to the diagnostic object portion and the value obtained by multiplying the change amount of the temperature of the portion other than the diagnostic object portion by the coefficient corresponding to the portion other than the diagnostic object portion. The control unit 12 can set a determination value for the value representing the state of the diagnostic object portion of the cable 40 that takes into account the state of the portion other than the diagnostic object portion of the cable 40 based on the coefficient corresponding to the diagnostic object portion and the coefficient corresponding to the portion other than the diagnostic object portion.

[0090] As described above, the control unit 12 can diagnose the state of the diagnostic object portion of the cable 40 based on the change over time of the temperature of each of the diagnostic object portion of the cable 40 and the portion other than the diagnostic object portion. Thereby, the influence of environmental changes is reduced in the diagnosis of the state of each part of the cable 40.

[0091] The control unit 12 can separately implement the following settings, that is, the setting of the change amount threshold for diagnosing the change in the exposed state of the cable 40 in the sea 84 or the determination value of the value representing the state of the diagnostic object portion of the cable 40 considering the state of the portion of the cable 40 other than the diagnostic object portion, and the setting of the change amount threshold for diagnosing the state of buckling or breakage of the cable 40 or the determination value of the value representing the state of the diagnostic object portion of the cable 40 considering the state of the portion of the cable 40 other than the diagnostic object portion. Thereby, the control unit 12 can distinguish between diagnosing that the state of the cable 40 is an abnormality of being exposed in the sea 84 or an abnormality such as buckling or breakage.

[0092] The number of portions other than the diagnostic object portion, which the control unit 12 sets as the object to be compared with the change over time of the temperature of the diagnostic object portion, is not limited to 1. The control unit 12 can compare the change over time of the temperature of two or more portions other than the diagnostic object portion with the change over time of the temperature of one diagnostic object portion to diagnose the state of the diagnostic object portion of the cable 40.

[0093] <Combination of diagnostic methods>

[0094] The control unit 12 can diagnose the possibility that there is an abnormality in the state of the diagnostic object portion of the cable 40 through diagnosis based on the change over time of the temperature of each of the diagnostic object portion of the cable 40 and the portion other than the diagnostic object portion. After diagnosing the possibility that there is an abnormality in the state of the diagnostic object portion of the cable 40, the control unit 12 can diagnose whether the state of the diagnostic object portion of the cable 40 is abnormal only based on the change over time of the temperature of the diagnostic object portion of the cable 40.

[0095] The control unit 12 can diagnose the possibility that there is an abnormality in the state of the diagnostic object portion of the cable 40 only based on the change over time of the temperature of the diagnostic object portion of the cable 40. After diagnosing the possibility that there is an abnormality in the state of the diagnostic object portion of the cable 40, the control unit 12 can diagnose whether the state of the diagnostic object portion of the cable 40 is abnormal through diagnosis based on the change over time of the temperature of each of the diagnostic object portion of the cable 40 and the portion other than the diagnostic object portion.

[0096] As a comparative example, the control unit 12 monitors only the change over time of the measured value of the temperature of a certain one diagnostic target portion of the cable 40, and it is assumed that if the temperature of the diagnostic target portion rises, it is diagnosed that an abnormality may exist in the diagnostic target portion. However, sometimes it is impossible to determine that an abnormality exists in a certain one diagnostic target portion of the cable 40 only based on the rise in the temperature of that diagnostic target portion. For example, when the temperature of the entire cable 40 rises due to power supply through the cable 40 or the like, even if the temperature of a certain one diagnostic target portion of the cable 40 rises, the temperature of the adjacent diagnostic target portion or other diagnostic target portions also rises. If the temperature of the entire cable 40 rises, the control unit 12 does not determine that an abnormality exists in that diagnostic target portion based on the rise in the temperature of a certain one diagnostic target portion of the cable 40.

[0097] Therefore, regarding the diagnostic system 1 according to the present invention, even if the temperature of a certain one diagnostic target portion of the cable 40 rises, the control unit 12 does not immediately determine that the diagnostic target portion is abnormal, but confirms the temperature of the portion other than the diagnostic target portion. For example, the control unit 12 can confirm, as the temperature of the portion other than the diagnostic target portion, the temperature of the measurement target portion adjacent to the measurement target portion corresponding to the diagnostic target portion or the temperature of other measurement target portions located within a specified distance from the diagnostic target portion. The control unit 12 can be configured such that when the temperature of the diagnostic target portion rises, if the temperature of the portion other than the diagnostic target portion does not rise, it is determined that only the temperature of the diagnostic target portion has changed and an abnormality exists in the diagnostic target portion. When the temperature of the diagnostic target portion rises, if the temperature of the portion other than the diagnostic target portion rises, the control unit 12 confirms the range of the temperature rise in the same manner as the diagnostic target portion. The control unit 12 can determine that an abnormality exists in the cable 40 within that range when it is possible to determine the range of the temperature rise in the same manner as the diagnostic target portion.

[0098] As described above, the control unit 12 not only confirms the temperature of the diagnostic target portion of the cable 40, but also confirms the temperature of the portion other than the diagnostic target portion, so that compared with the case of only confirming the temperature of the diagnostic target portion of the cable 40, it is less likely to misdiagnose an abnormality in the diagnostic target portion of the cable 40. In other words, the diagnostic accuracy of the abnormality in the diagnostic target portion of the cable 40 can be improved.

[0099] After performing a diagnosis based on the temperature change over time of each of the diagnostic target portion of the cable 40 and the portion other than the diagnostic target portion, the control unit 12 can diagnose whether the state of the diagnostic target portion of the cable 40 is abnormal by performing a diagnosis based only on the temperature change over time of the diagnostic target portion of the cable 40. After performing a diagnosis based only on the temperature change over time of the diagnostic target portion of the cable 40, the control unit 12 can diagnose whether the state of the diagnostic target portion of the cable 40 is abnormal by performing a diagnosis based on the temperature change over time of the diagnostic target portion of the cable 40 and the portion other than the diagnostic target portion. That is, the control unit 12 can diagnose whether the state of the diagnostic target portion of the cable 40 is abnormal by performing a diagnosis that combines a diagnosis based on the temperature change over time of each of the diagnostic target portion of the cable 40 and the portion other than the diagnostic target portion and a diagnosis based only on the temperature change over time of the diagnostic target portion of the cable 40. Thereby, the diagnostic accuracy of the state of each part of the cable 40 is improved.

[0100] The control unit 12 can determine whether the temperature change over time of each of the diagnostic target part based on the cable 40 and the part other than the diagnostic target part satisfies the diagnostic conditions in the diagnosis based on the temperature change over time of each of the diagnostic target part based on the cable 40 and the part other than the diagnostic target part, where the diagnostic conditions are the conditions applied to the diagnosis based on the temperature change over time of each of the diagnostic target part based on the cable 40 and the part other than the diagnostic target part. The diagnostic conditions applied to the diagnosis based on the temperature change over time of each of the diagnostic target part based on the cable 40 and the part other than the diagnostic target part may include the condition of the value representing the state of the diagnostic target part based on the state of the part other than the diagnostic target part of the cable 40 calculated by considering the change amounts of the temperature of the diagnostic target part based on the cable 40 and the temperature of the part other than the diagnostic target part of the cable 40. The diagnostic conditions applied to the diagnosis based on the temperature change over time of each of the diagnostic target part based on the cable 40 and the part other than the diagnostic target part may include changing the temperature of the diagnostic target part of the cable 40 without changing the temperature of the part other than the diagnostic target part of the cable 40. The diagnostic conditions applied to the diagnosis based on the temperature change over time of each of the diagnostic target part based on the cable 40 and the part other than the diagnostic target part may include that the change amount of the temperature of the diagnostic target part of the cable 40 is greater than the change amount of the temperature of the part other than the diagnostic target part of the cable 40 before and after a specified time. The diagnostic conditions applied to the diagnosis based on the temperature change over time of each of the diagnostic target part based on the cable 40 and the part other than the diagnostic target part may include that the change amount of the temperature of the diagnostic target part of the cable 40 is greater than or equal to the change amount threshold. The diagnostic conditions applied to the diagnosis based on the temperature change over time of each of the diagnostic target part based on the cable 40 and the part other than the diagnostic target part may include that the value representing the state of the diagnostic target part of the cable 40 based on considering the state of the part other than the diagnostic target part of the cable 40 is greater than or equal to the determination value.

[0101] The control unit 12 can determine whether the temperature of the diagnostic target part satisfies the diagnostic conditions applied to the diagnosis based on only the temperature change over time of the diagnostic target part based on the cable 40 in the diagnosis based on only the temperature change over time of the diagnostic target part based on the cable 40. The diagnostic conditions applied to the diagnosis based on only the temperature change over time of the diagnostic target part based on the cable 40 may include the condition based on the temperature of the diagnostic target part of the cable 40. The diagnostic conditions applied to the diagnosis based on only the temperature change over time of the diagnostic target part based on the cable 40 may include that the temperature of the diagnostic target part of the cable 40 deviates from the determination range. The diagnostic conditions applied to the diagnosis based on only the temperature change over time of the diagnostic target part based on the cable 40 may include that the risk degree calculated based on the temperature of the diagnostic target part of the cable 40 is greater than or equal to the risk degree threshold.

[0102] <Output of Diagnostic Results>

[0103] The control unit 12 can display the diagnostic results on the display device 30. The control unit 12 can output the diagnostic results in other ways such as voice. When the control unit 12 diagnoses that the state of a part of the cable 40 is abnormal, it can output the diagnostic results in a way that notifies the abnormality. The control unit 12 can also output the diagnostic results when it diagnoses that the state of the cable 40 is normal.

[0104] The control unit 12 can display the measured values of the temperatures of the respective parts of the cable 40 used for diagnosis on the display device 30. The control unit 12 can display the change in the temperature of each part of the cable 40 over time on the display device 30. The control unit 12 can display values indicating the state of the diagnostic target part of the cable 40 in consideration of the risk level calculated during the diagnosis or the state of parts of the cable 40 other than the diagnostic target part, etc. on the display device 30. The control unit 12 can display the measured values of the temperatures of the respective parts of the cable 40, etc. in association with the diagnostic results. Personnel such as the operator who manages the cable 40, the monitor, or the operator of the diagnostic device 10 can confirm the measured values of the temperatures of the respective parts of the cable 40 and the diagnostic results together, thereby improving the diagnostic skills or insights of the personnel.

[0105] <Example of the Flow of the Diagnostic Method>

[0106] The control unit 12 of the diagnostic device 10 can execute a diagnostic method that includes the flow of the flowchart shown as an example for diagnosing the state of the cable 40. The diagnostic method can be implemented as a diagnostic program that causes a processor or computer constituting the control unit 12 to execute. The diagnostic program can be stored in a non-temporary computer-readable medium. Figure 5 The control unit 12 obtains the measured values of the temperatures of the diagnostic target part of the cable 40 and the parts other than the diagnostic target part from the temperature measurement device 20 (step S1).

[0107] The control unit 12 determines whether the change in the temperature of the diagnostic target part of the cable 40 and the parts other than the diagnostic target part over time satisfies the diagnostic conditions, which are the conditions applied to the diagnosis based on the change in the temperature of the diagnostic target part of the cable 40 and the parts other than the diagnostic target part over time (step S2). When the change in the temperature of the diagnostic target part of the cable 40 and the parts other than the diagnostic target part over time does not satisfy the diagnostic conditions (step S2: NO), the control unit 12 diagnoses that the state of the diagnostic target part of the cable 40 is not abnormal and ends the execution of the flowchart process.

[0108] Figure 5 the execution of the flowchart process.

[0109] When the temperature change over time of each of the diagnostic target portion of the cable 40 and the portion other than the diagnostic target portion satisfies the diagnostic conditions for the diagnosis applied to the temperature change over time of each of the diagnostic target portion of the cable 40 and the portion other than the diagnostic target portion (step S2: YES), the control unit 12 determines whether the temperature of the diagnostic target portion of the cable 40 satisfies the diagnostic conditions for the diagnosis in which the temperature of the diagnostic target portion is applied to the diagnosis based on the temperature of the diagnostic target portion of the cable 40 (step S3). When the temperature of the diagnostic target portion of the cable 40 does not satisfy the diagnostic conditions (step S3: NO), the control unit 12 diagnoses that the state of the diagnostic target portion of the cable 40 is not abnormal and ends Figure 5 the execution of the process of the flowchart.

[0110] When the temperature of the diagnostic target portion of the cable 40 satisfies the diagnostic conditions (step S3: YES), the control unit 12 determines that the state of the diagnostic target portion of the cable 40 is abnormal and notifies the abnormality of the diagnostic target portion of the cable 40 (step S4). After the control unit 12 executes the process of step S4, it ends Figure 5 the execution of the process of the flowchart.

[0111] In Figure 5 the process of the flowchart shown as an example, compared with the diagnosis based on the temperature of the diagnostic target portion of the cable 40, the control unit 12 first executes the diagnosis of the temperature change over time of each of the diagnostic target portion of the cable 40 and the portion other than the diagnostic target portion. Compared with the diagnosis of the temperature change over time of each of the diagnostic target portion of the cable 40 and the portion other than the diagnostic target portion, the control unit 12 may first execute the diagnosis based on the temperature of the diagnostic target portion of the cable 40. The control unit 12 may also execute only one of the diagnosis of the temperature change over time of each of the diagnostic target portion of the cable 40 and the portion other than the diagnostic target portion or the diagnosis based on the temperature of the diagnostic target portion of the cable 40.

[0112] <Subsection>

[0113] As described above, regarding the diagnostic system 1 according to the present embodiment, the diagnostic device 10 can diagnose the state of each part of the cable 40 based on the temperature of each part of the cable 40. Thus, the state of each part of the cable 40 is continuously diagnosed. In addition, the diagnostic device 10 can diagnose the state of each part of the cable 40 based on the temperature change over time of a plurality of parts of the cable 40. Thus, the influence of environmental changes is weakened in the diagnosis of the state of each part of the cable 40. As a result, the diagnostic accuracy of the state of each part of the cable 40 is improved.

[0114] In addition, the diagnostic device 10 can distinguish between diagnosing whether the state of the cable 40 is an abnormality exposed in the sea 84 or an abnormality such as buckling or breakage. Thus, various states are diagnosed separately from each other. As a result, the diagnostic accuracy of various states of the cable 40 is improved.

[0115] According to the diagnostic system 1, even if the main body managing the cable 40 is not at the site, the state of the cable 40 can be diagnosed. The main body managing the cable 40 is, for example, a person such as an operator, a monitor, or an operator of the diagnostic device 10. As a result, the frequency and cost of personnel accessing the site where the cable 40 is buried are reduced. In addition, the reliability of the cable 40 is improved by always achieving diagnosis.

[0116] According to the diagnostic system 1, the diagnostic criteria for the state of each part of the cable 40 become clear. As a result, the reliability of the cable 40 is improved.

[0117] The diagnostic system 1 sets the temperature measurement target parts at, for example, 1-meter intervals in such a way as to reduce monitoring omissions in a long cable 40 extending over several hundred or several thousand meters, and monitors the state of each part of the cable 40. In this way, in order to measure the temperature throughout the entire cable 40, a sensor of the same length as the cable 40 is required, but it is easily achieved by using the optical fiber 42 as a sensor and arranging it along the cable 40. And, multiple optical fibers 42 are originally built into the submarine cable. The idle optical fibers among the multiple optical fibers 42 that are not used for other functions are directly used as temperature sensors. The diagnostic system 1 monitors whether there is a part with a temperature rise among several hundred, several thousand, or tens of thousands of measurement target parts existing along the cable 40. When the diagnostic system 1 finds a measurement target part with a temperature rise, it can confirm the temperature of the measurement target part adjacent to or near the measurement target part and improve the diagnostic accuracy.

[0118] In the diagnostic system 1 according to the above-mentioned embodiment, the control unit 12 of the diagnostic device 10 diagnoses whether the diagnostic target portion of the cable 40 is abnormal based on the change in the temperature of the diagnostic target portion of the cable 40 over time. If the diagnostic target portion of the cable 40 is normal, the measured value of the temperature of the diagnostic target portion of the cable 40 should not change relative to the reference value, assuming that there is no change in the overall environment such as the change in seawater temperature. The reference value is the measured value of the temperature when the diagnostic target portion of the cable 40 is normally buried and the cable 40 itself is normal. The change in the temperature of the diagnostic target portion of the cable 40 over time indicates the degree to which the measured value of the current temperature deviates from the reference value of the temperature measured when it is normal. The change in the temperature of the diagnostic target portion of the cable 40 over time is the difference between the temperature at a certain time and the temperature at a time traced back to the past at a predetermined time relative to the time. Therefore, the control unit 12 can diagnose whether the diagnostic target portion of the cable 40 is abnormal by comparing the temperature of the diagnostic target portion of the cable 40 with the reference value.

[0119] (Other embodiments)

[0120] Next, other embodiments will be described.

[0121] <Considering geological diagnosis>

[0122] The geology of the seabed 81 where the cable 40 is buried is sometimes different. For example, the geology of the part to be diagnosed where the cable 40 is buried is sometimes different from the geology of the part other than the part to be diagnosed where the cable 40 is buried. The control unit 12 of the diagnostic device 10 can diagnose the states of the parts of the cable 40 by assuming that the geology of a certain part where the cable 40 is buried is different from the geology of other parts where the cable 40 is buried. For example, a certain part of the cable 40 is the part to be diagnosed. For example, other parts of the cable 40 are parts other than the part to be diagnosed.

[0123] The temperature of the entire cable 40 may rise due to the current flowing through the cable 40. On the other hand, the temperature rise may vary for each portion of the cable 40. The temperature rise of the diagnosis target portion of the cable 40 may be determined by the environment of the diagnosis target portion in which the cable 40 is buried or the material of the sand and soil constituting the underground 80 where the diagnosis target portion of the cable 40 is buried. For example, the measured value of the temperature of the diagnosis target portion of the cable 40 may vary for each type of the sand and soil constituting the underground 80 where the diagnosis target portion of the cable 40 is buried.

[0124] Regarding the change in temperature over time, when the measured value of the temperature at a certain time is 27°C and the measured value of the temperature one minute before that is 25°C, the temperature change per minute can be expressed as a 2°C increase per minute. When the measured value of the temperature of the temperature measurement object part (N) corresponding to a certain diagnostic object part increases by 2°C per minute, the control unit 12 does not determine that the diagnostic object part is abnormal, but instead confirms the temperature of, for example, the adjacent measurement object part (N + 1) or the further adjacent measurement object part (N + 2) of the temperature measurement object part (N) corresponding to the diagnostic object part, which is a part other than the diagnostic object part. When the temperatures of the measurement object parts (N), (N + 1), and (N + 2) all increase, and the temperatures of the further adjacent measurement object part (N + 3) and the adjacent measurement object part (N - 1) in the opposite direction do not increase, the control unit 12 can determine that the cable 40 is abnormal regarding the measurement object parts (N), (N + 1), and (N + 2) of the temperature of the cable 40.

[0125] Here, depending on the environment in which the cable 40 is buried or the material of the sand and soil of the underground 80 that constitutes the diagnostic object part where the cable 40 is buried, the criteria for determining whether the change in temperature over time indicates an abnormality of the cable 40 are different. That is, the control unit 12 can assume that the environment in which the cable 40 is buried or the material of the sand and soil of the underground 80 that constitutes the diagnostic object part where the cable 40 is buried is different when determining whether the temperature of each measurement object part increases.

[0126] The control unit 12 can infer a geological change by comparing the change in temperature over time between two adjacent points in the temperature measurement object part of the cable 40. For example, when the change in temperature at a certain location is different from the change in temperature at its adjacent location, the control unit 12 can infer that these two points are included in different geological formations.

[0127] For example, assume that the measured value of the temperature of the temperature measurement object part (N) of the normally buried cable 40 is 25°C, the measured values of the temperatures of the adjacent measurement object parts (N + 1) to (N + 5) are 25°C, and the measured value of the temperature of the further adjacent measurement object part (N + 6) is 27°C. In this case, the control unit 12 can infer that a geological change has occurred in the geology where the cable 40 is buried between the measurement object parts (N + 5) and (N + 6). Not limited to geological changes, the control unit 12 can also infer that other environments have changed.

[0128] For example, the reference value of the temperature of the measurement object parts (N) to (N+5) is set to 25°C. The measured value of the temperature of the measurement object parts (N) to (N+5) is set to 27°C. In this case, the temperature of the measurement object parts (N) to (N+5) rises by 2°C. On the other hand, the reference value and measured value of the temperature of the measurement object parts (N+6) to (N+100) are set to 27°C. In this case, the temperature of the measurement object parts (N+6) to (N+100) does not rise. The control unit 12 can determine that an abnormality has occurred in the measurement object parts (N) to (N+5) based on the above-mentioned temperature measurement results.

[0129] Geological data is located in a vast and deep water surface and is difficult to obtain. As described above, the control unit 12 does not use the geological data itself, and can determine the state of the diagnostic object part of the cable 40 by assuming the geology without being clearly aware of the geology. In addition, the control unit 12 can determine whether the change in temperature of each diagnostic object part of the cable 40 over time is abnormal based on the geological data when the geological data can be obtained. The control unit 12 can measure the temperature of each measurement object part of the cable 40 via the optical fiber, and when a certain measurement object part is set as the diagnostic object part, the temperature of the diagnostic object part is compared with the temperature of the surrounding measurement object parts, that is, the parts other than the diagnostic object part, and the change point of the environment or a part of the environment, that is, the geology, is estimated based on the relationship, and the judgment is made based on the temperature difference conditions of each area.

[0130] In the case where geological data is only partially acquired, even if there are concerns about the accuracy of the geological data or the geological data cannot be fully acquired, the control unit 12 sets the reference temperature when each measurement object part is set as the diagnosis object part based on the temperature of each measurement object part of the cable 40 when the cable 40 is normally buried. When the cable 40 is normally buried, it should be before the start of operation or just after renovation. The control unit 12 can estimate the range including the measurement object part whose measured value of temperature is the same as that when the cable 40 is normally buried as a range with consistent environmental conditions or a range with the same geology. In the above example, the range including the measurement object parts (N) to (N+5) is estimated to be a certain geology with a reference value of temperature set to 25°C. The range including the measurement object parts (N+6) to (N+100) is another geology with a reference value of temperature set to 27°C. The control unit 12 starts the operation of the cable 40, and when time has passed since the cable 40 was normally buried and the state of the buried cable 40 or the state of the cable 40 itself may have changed, each measurement object part is set as a diagnosis object part based on a reference value of the temperature set for each measurement object part to determine whether the diagnosis object part is abnormal.

[0131] In a range including a measurement target part with a reference value of temperature being 25°C, when there is a measurement target part with a measured temperature value of 27°C, the control unit 12 determines that the temperature of the measurement target part has risen when setting this measurement target part as the diagnosis target part, and determines that the diagnosis target part is abnormal. On the other hand, in a range including a measurement target part with a reference value of temperature being 27°C, when there is a measurement target part with a measured temperature value of 27°C, the control unit 12 determines that the temperature of the measurement target part has not changed when setting this measurement target part as the diagnosis target part, and determines that the diagnosis target part is not abnormal.

[0132] When comparing the measured temperature values of multiple measurement target parts, the control unit 12 can compare the measured temperature values of adjacent measurement target parts considering that the possibility of the geology and environment of adjacent measurement target parts being the same is relatively high. The comparison ratio of the measured temperature values of multiple measurement target parts can include, for example, the comparison between the temperature of the diagnosis target part and the temperature of parts other than the diagnosis target part. On the other hand, it is not necessary to be adjacent. The control unit 12 can also pre-record the address (N + x) of the measurement target part with a normal measured temperature value of 25°C, and compare the measured temperature values between measurement target parts with the same normal measured temperature value. That is, the control unit 12 can find a measurement target part with a deviated measured temperature value as an abnormal part among the measurement target parts where the measured temperature value should be 25°C if the state is normal.

[0133] As Figure 6 For example, it is assumed that the cable 40 is buried in such a way as to pass through a part of geology α, a part of geology β, and a part of geology γ. The control unit 12 may not be able to obtain data on the differences in the geology where the cable 40 is buried. The normal temperature of the cable 40 buried in geology α is set to 25°C. The normal temperature of the cable 40 buried in geology β is set to 27°C. The normal temperature of the cable 40 buried in geology γ is set to 23°C. The control unit 12 can obtain the normal temperature of each part of the cable 40 as the measured temperature value at the time of burying the cable 40. The control unit 12 can regard the difference in the normal temperature of each part of the cable 40 as the difference in the geology where the cable 40 is buried, or as the difference in the environment other than geology, or it may not be related to any factor.

[0134] The control unit 12 presumes that A1, A2, and A3 are included in the geological stratum β. The control unit 12 can obtain the temperatures of the respective parts of A1, A2, and A3 that are presumed to be included in the geological stratum β. The temperature of A2 is set to 25°C, which is lower than the normal temperature of 27°C of the geological stratum β. The temperatures of A1 and A3 are set to the normal temperature of 27°C. In this case, the control unit 12 can diagnose that the state of the part corresponding to A2 of the cable 40 is abnormal. When the temperature of A1 is 26°C, which is lower than the normal temperature, the control unit 12 can compare the temperature of the part farther from A1 observed from A2 with the normal temperature, so as to diagnose whether the abnormality of the state of the part corresponding to A2 of the cable 40 spreads to the part corresponding to A1 and whether it spreads to a part farther from A2.

[0135] The control unit 12 presumes that C, C-1, and C-2 are included in the geological stratum γ. The control unit 12 presumes that C+1 and C+2 are included in the geological stratum α. The control unit 12 can obtain the temperatures of the respective parts of C, C-1, and C-2 that are presumed to be included in the geological stratum γ. In addition, the control unit 12 can obtain the temperatures of the respective parts of C+1 and C+2 that are presumed to be included in the geological stratum α adjacent to the geological stratum γ. The normal temperature of the geological stratum γ is set to 23°C. The temperature of C is set to 20°C, which is lower than the normal temperature (23°C) of the geological stratum γ. The temperatures of C-1 and C-2 are set to the normal temperature (23°C) of the geological stratum γ. In addition, the normal temperature of the geological stratum α is set to 25°C. The temperatures of C+1 and C+2 are set to the normal temperature (25°C) of the geological stratum α. In this case, the control unit 12 can diagnose that the state of the part corresponding to C of the cable 40 is abnormal. The control unit 12 can diagnose that the state of the part corresponding to C-1 of the cable 40 is normal based on the same temperatures of C-1 and C-2. In addition, the control unit 12 can diagnose that the state of the part corresponding to C+1 of the cable 40 is normal based on the same temperatures of C+1 and C+2. Regarding the diagnosis related to C, in other words, the control unit 12 can change the part other than the diagnosis target part to a different part of the cable 40 in such a way that the change amounts of the temperatures of the diagnosis target part and the part other than the diagnosis target part respectively satisfy the diagnosis conditions applied to the diagnosis based on the temperature change over time of the diagnosis target part and the part other than the diagnosis target part of the cable 40. Thus, the state of the cable 40 is diagnosed assuming the geological stratum. As a result, the diagnosis accuracy of the state of the cable 40 is improved.

[0136] The control unit 12 can obtain the temperature of the portion of D presumed to be included in the geological formation α. The temperature of the portion of D is set to the normal temperature (25 °C) of the geological formation α. In this case, the control unit 12 can diagnose that the state of the portion of the cable 40 corresponding to D is normal. The control unit 12 can obtain the temperature of the portion of B included in the geological formation γ. The temperature of the portion of B is set to the normal temperature (23 °C) of the geological formation γ. In this case, the control unit 12 can diagnose that the state of the portion of the cable 40 corresponding to B is normal.

[0137] The control unit 12 can presume the temperature of each of the portions E1, E2, and E3 that are included in the geological formation α and are close to the portion where the cable 40 rises toward the land 82. The temperature of E1, which is the starting point of the burial, is a temperature close to the temperature of the seawater. The temperatures of E2 and E3 are each set to the normal temperature (25 °C) of the geological formation α. In this case, the control unit 12 can diagnose that the states of the portions of the cable 40 corresponding to E2 and E3 are normal. In addition, the portion where the cable 40 rises toward the land 82 is not easily affected by fishing gear or anchors. The control unit 12 can diagnose a change in the environment of the area where the cable 40 is buried based on the change over time in the temperature of at least one of the portions E2 or E3. The control unit 12 can diagnose a change in the current flowing through the cable 40 based on the change over time in the temperature of at least one of E1, E2, or E3.

[0138] <Diagnosis Considering Heat Generation of Cable 40>

[0139] As Figure 7 shown by way of example, in the case where the temperature of the entire cable 40 rises due to the flow of current through the cable 40, the surface temperature of the cable 40 is determined according to the magnitude of the heat loss of each portion of the cable 40. In Figure 7 the graph, the horizontal axis represents the position in the longitudinal direction of the cable 40. The vertical axis represents the temperature. The graph of the cable heating temperature represents the temperature of the portion of the cable 40 to be diagnosed in the case of no heat loss. The graph of the cable surface temperature represents the temperature reduced due to heat loss and changes with the exposed starting portion 45 where the cable 40 starts to be exposed in the sea 84 as the boundary. In the portion buried underground 80 to the left of the exposed starting portion 45 of the graph, the cable surface temperature decreases corresponding to the amount of heat conduction loss determined according to the depth at which the cable 40 is buried. In the portion exposed in the sea 84 to the right of the exposed starting portion 45 of the graph, the cable surface temperature decreases corresponding to the amount of convective heat loss determined according to the area of the surface of the cable 40 exposed in the sea 84.

[0140] The control unit 12 can determine the exposed start portion 45 of the cable 40 based on the temperature change in the longitudinal direction of the cable 40. The control unit 12 can calculate the depth of the buried cable 40 based on the temperature change in the longitudinal direction of the cable 40. The control unit 12 can calculate the ratio of the area where the surface of the cable 40 is exposed in the sea 84 based on the temperature change in the longitudinal direction of the cable 40.

[0141] The cable 40 can be laid in a state where it is not buried underground 80 but is exposed to the sea 84 on the seabed 81, and is protected by wave blocks or gravel placed on the cable 40. In this case, the cable 40 may be cooled due to convective heat loss of seawater entering through the gaps between the wave blocks or gravel. The control unit 12 can diagnose the state of the cable 40 by considering the change in heat generation caused by the change in the current flowing through the cable 40.

[0142] As Figure 8A an example shows, the control unit 12 calculates the heat generation temperature of the cable 40 without heat loss based on the change in the current of the cable 40 over time. In Figure 8A the curve graph, the horizontal axis represents time. The vertical axis represents temperature. Since the current flowing through the cable 40 starts to decrease from time T11, the heat generation temperature starts to drop. Since the current flowing through the cable 40 starts to increase from time T12, the heat generation temperature starts to rise.

[0143] As Figure 8B an example shows, the control unit 12 obtains the change in the measured value of the temperature at location X of the cable 40 over time. Additionally, as Figure 8C an example shows, the control unit 12 obtains the change in the measured value of the temperature at location Y of the cable 40 over time. In Figure 8B and Figure 8C the curve graphs, the horizontal axis represents time. The vertical axis represents temperature. The temperature at location X of the cable 40 starts to drop from time T21 and starts to rise from time T22. The temperature at location Y of the cable 40 starts to drop from time T31 and starts to rise from time T32. The times T31 and T32 are set to be lagged behind the times T21 and T22.

[0144] The difference in the timing of temperature change at location X and the timing of temperature change at location Y is caused by differences in heat dissipation characteristics such as the heat dissipation amount at each location or the heat capacity of the geology. The control unit 12 can calculate the underground heat conductivity of each location based on the differences in the heat dissipation characteristics of each location. The underground heat conductivity is determined based on the properties of the substances constituting the geology, the structure of the geology, the density, etc. The control unit 12 can correct values equivalent to the value indicating the state of the diagnostic target portion of the cable 40 based on the underground heat conductivity and considering the risk level of each portion of the cable 40 or the state of the portion of the cable 40 other than the diagnostic target portion. The control unit 12 can obtain the time when the temperature change starts as the timing of the temperature change, or can also obtain the time when the temperature change rate is at its maximum value. The time when the temperature change rate is at its maximum value is the time when the slope of the temperature change curve is the steepest. For example, the control unit 12 can set location X as the diagnostic target portion. In the case where location Y is set as the portion other than the diagnostic target portion, based on the difference between the timing of temperature change at location X as the diagnostic target portion and the timing of temperature change at location Y as the portion other than the diagnostic target portion, and considering the state of the portion of the cable 40 other than the diagnostic target portion, the value indicating the state of the diagnostic target portion of the cable 40 is corrected.

[0145] As described above, by considering the heat generation of the cable 40, the diagnostic accuracy of the state of the cable 40 is improved.

[0146] <Diagnosis when current does not flow through the cable 40>

[0147] As described above, the control unit 12 can correct values equivalent to the value indicating the state of the diagnostic target portion of the cable 40 by considering the heat generation of the cable 40 and considering the risk level or the state of the portion of the cable 40 other than the diagnostic target portion. When current does not flow through the cable 40, the cable 40 does not generate heat. Even when the cable 40 does not generate heat, the control unit 12 can correct values equivalent to the value indicating the state of the diagnostic target portion of the cable 40 by considering other information and considering the risk level or the state of the portion of the cable 40 other than the diagnostic target portion.

[0148] The temperature of seawater changes in a one-day cycle. The control unit 12 can correct values equivalent to the value indicating the state of the diagnostic target portion of the cable 40 by considering the risk level of each portion of the cable 40 or the state of the portion of the cable 40 other than the diagnostic target portion based on the difference between the change in the temperature of seawater and the change in the temperature of each portion of the cable 40. It can be configured such that when current has not flowed for a long time such as during construction, etc., the control unit 12 corrects values equivalent to the value indicating the state of the diagnostic target portion of the cable 40 based not only on one-day data but also on long-term data by considering the risk level of each portion of the cable 40 or the state of the portion of the cable 40 other than the diagnostic target portion.

[0149] When the cable 40 is buried deep underground 80, the temperature of each part of the cable 40 is not easily affected by the change in the temperature of seawater with a one-day cycle. On the other hand, the temperature of seawater sometimes changes with a one-year cycle due to, for example, seasonal changes or meandering of ocean currents. The control unit 12 can correct values such as the state value of the diagnostic target part of the cable 40 in consideration of the risk level of each part of the cable 40 or the state of parts of the cable 40 other than the diagnostic target part based on the difference between the moving average of the seawater temperature and the moving average of the temperature of each part of the cable 40. Specifically, the control unit 12 can calculate the difference in the timing of the slope inversion of the moving average of the temperature of each part of the cable 40 with respect to the timing of the slope inversion of the moving average of the seawater temperature with the timing of the slope inversion of the moving average of the seawater temperature as a reference. The control unit 12 can use the difference in the timing of the slope inversion of the moving average of the temperature of each part of the cable 40 as a parameter inversely proportional to the underground thermal conductivity to correct values such as the state value of the diagnostic target part of the cable 40 in consideration of the risk level of each part of the cable 40 or the state of parts of the cable 40 other than the diagnostic target part.

[0150] <Specific Example of Correction Using Underground Thermal Conductivity>

[0151] The control unit 12 can correct parameters such as the state value of the diagnostic target part of the cable 40 in consideration of the risk level used in the diagnosis of each part of the buried cable 40 or the state of parts of the cable 40 other than the diagnostic target part based on the underground thermal conductivity of each part of the buried cable 40. The control unit 12 can set parameters of the underground thermal conductivity for each unit that divides the cable 40 in detail for each area. The parameter group is also called a profile. The control unit 12 can associate the burial information such as the burial depth of the cable 40 and time with the position information of the cable 40 as characteristic data. The position information of the cable 40 can include, for example, the distance from the temperature measurement device 20. The control unit 12 can associate time, the temperature at that position of the cable 40, the voltage applied to the cable 40, and the current flowing through the cable 40 with the position information of the cable 40 as historical data. The control unit 12 can associate the underground type and the underground thermal conductivity with the position information of the cable 40 as historical data. The control unit 12 can associate the assumed burial depth, the long-term change rate, the short-term change rate, and the abnormality level with the position information of the cable 40 as historical data.

[0152] The temperature measurement device 20 outputs the measured value of the temperature and the distance from the location where the measured value is obtained. Here, if the voltage drop is considered as an error, the voltage, current, and heat generation amount of the cable 40 are the same in each unit of the cable 40. Therefore, the heat dissipation amount and the measured value of the temperature of each unit of the cable 40 with the same or similar profiles are the same. The same or similar profiles are determined by the same or similar depths and the same or similar heat conductivities. Even when the power supply power based on the cable 40 changes, the heat generation amount and the heat dissipation amount of the cable 40 follow, so the units with the same or similar profiles are formed into the same or similar heat generation patterns with each other.

[0153] On the other hand, in the initial state of cable laying where the laying depth of the cable 40 hardly changes, sometimes a difference in temperature change occurs due to following the current. When buried at a certain depth, the temperature change difference is caused by the underground heat conductivity. Then, the underground heat conductivity of each unit is corrected by performing reverse calculation based on the temperature change difference. When the laying depth is deep enough, the amount of heat convection can be ignored. The correction value of the underground heat conductivity can be calculated as ratio data or as a deviation. The correction value of the underground heat conductivity can be stored according to the underground type.

[0154] <Determination of the exposed part>

[0155] The submarine cable has a part that is planned to be exposed from the underground 80 to the seabed 81. Inside the underground 80, the heat dissipation amount is mainly determined by the heat conductivity of the underground 80. On the other hand, until approaching the part exposed to the seabed 81, there is a point where the heat dissipation amount increases sharply. This point is near the exposed part 52. As one of the methods to know the exposed part of the cable 40, there is a method of comparing the location and position information exposed to the seabed 81 based on the information of the laying project, etc., and comparing the temperature change at this position.

[0156] In addition, the exposed part can be determined by calculation. In a place buried at a shallow position, heat radiation caused by heat conduction, radiation, and convection dominates. On the other hand, at the exposed place, the heat conduction part with a small heat dissipation amount disappears, resulting in a sharp increase in the heat dissipation amount. If this is utilized, the temperature of the unit buried shallower than a certain constant depth gradually decreases compared to the temperature of the unit buried deeper and having the same or similar profile. And when convection replaces heat conduction and dominates due to being exposed to the seabed 81, etc., the temperature further decreases. Therefore, the part where the temperature decreases can be determined as the exposed part.

[0157] <Other examples of the diagnosis object>

[0158] The diagnostic system 1 is not limited to the submarine cable of the above-mentioned offshore wind power generation device 70, and can also be applied to the diagnosis of the states of various other cables 40. For example, the diagnostic system 1 can be applied to the diagnosis of the state of a submarine cable for supplying power or communication to an outlying island or the like. The diagnostic system 1 can be applied to the diagnosis of the state of a cable 40 laid on land. For example, even on land, it can be applied to the diagnosis of the state of a cable 40 buried in the ground or a cable 40 laid in an area where it is difficult for people to enter, such as in a mountainous area. The diagnostic system 1 can be applied to the diagnosis of the aging state of the cable 40. The diagnostic system 1 can be applied to the diagnosis of the water immersion state of the cable 40.

[0159] The embodiments of the present invention have been described based on the respective drawings and embodiments. However, it should be noted that those skilled in the art can make various deformations or changes based on the present invention. Therefore, it should be noted that the scope of the present invention includes the above-mentioned deformations or changes. For example, the functions and the like included in each structural part can be reconfigured in a logically non-contradictory manner, and multiple structural parts can be combined into one or divided.

[0160] Description of reference numerals

[0161] 1 Diagnostic system

[0162] 10 Diagnostic device (12: Control unit, 14: Storage unit, 16: Interface)

[0163] 20 Temperature measuring device

[0164] 30 Display device

[0165] 40 Cable (41: Electric wire, 42: Optical fiber, 43: Coating, 45: Starting part of exposure, 51: Buried part, 52: Exposed part, 53: Buried part, 54: Shallow buried part, 55: Boundary part)

[0166] 70 Offshore wind power generation device

[0167] 80 Underground

[0168] 81 Seabed

[0169] 82 Land

[0170] 84 Sea

[0171] 85, 86 Ocean currents

Claims

1. A diagnostic method for diagnosing the state of a cable including a diagnostic object portion and a portion other than the diagnostic object portion, wherein the diagnostic object portion corresponds to a part of the temperature measurement object portion of the cable, the portion other than the diagnostic object portion corresponds to a temperature measurement object portion different from the temperature measurement object portion corresponding to the diagnostic object portion, the diagnostic method includes the following steps: Obtaining a measured value of the temperature of the temperature measurement object portion corresponding to the diagnostic object portion of the cable as the temperature of the diagnostic object portion of the cable; Obtaining a measured value of the temperature of the temperature measurement object portion corresponding to the portion other than the diagnostic object portion of the cable as the temperature of the portion other than the diagnostic object portion of the cable; And When the change amount of the temperature of each of the diagnostic object portion and the portion other than the diagnostic object portion of the cable satisfies the diagnostic conditions applicable to the diagnosis based on the change of the temperature of each of the diagnostic object portion and the portion other than the diagnostic object portion of the cable over time, and the temperature of the diagnostic object portion of the cable satisfies the diagnostic conditions applicable to the diagnosis based on the temperature of the diagnostic object portion of the cable, it is determined that the state of the diagnostic object portion is abnormal.

2. The diagnostic method according to claim 1, wherein the diagnostic method includes the following steps: after determining that the change amount of the temperature of each of the diagnostic object portion and the portion other than the diagnostic object portion of the cable satisfies the diagnostic conditions applicable to the diagnosis based on the change of the temperature of each of the diagnostic object portion and the portion other than the diagnostic object portion of the cable over time, determining whether the temperature of the diagnostic object portion of the cable satisfies the diagnostic conditions applicable to the diagnosis based on the temperature of the diagnostic object portion of the cable.

3. The diagnostic method according to claim 2, wherein the diagnostic method includes the following steps: changing the portion other than the diagnostic object portion to a different portion of the cable in such a way that the change amount of the temperature of each of the diagnostic object portion and the portion other than the diagnostic object portion of the cable satisfies the diagnostic conditions applicable to the diagnosis based on the change of the temperature of each of the diagnostic object portion and the portion other than the diagnostic object portion of the cable over time.

4. The diagnostic method according to claim 1, wherein the diagnostic conditions applicable to the diagnosis based on the change of the temperature of each of the diagnostic object portion and the portion other than the diagnostic object portion of the cable over time include conditions representing the state of the diagnostic object portion based on the state of the portion other than the diagnostic object portion of the cable calculated by considering the change amount of the temperature of the diagnostic object portion of the cable and the temperature of the portion other than the diagnostic object portion of the cable, the diagnostic conditions applicable to the diagnosis based on the temperature of the diagnostic object portion of the cable include conditions based only on the change of the temperature of the diagnostic object portion over time.

5. The diagnostic method according to claim 4, wherein Based on the condition of only the change in temperature of the diagnostic object part over time, the temperature of the diagnostic object part including the cable deviates from the determination range. The determination range is set based on the magnitude of the current flowing through the cable and the environment around the diagnostic object part of the cable.

6. The diagnostic method according to claim 4, wherein The value representing the state of the diagnostic object part considering the state of the part of the cable other than the diagnostic object part is calculated as the absolute value of the difference between the value obtained by multiplying the change amount of the temperature of the diagnostic object part of the cable by the coefficient corresponding to the diagnostic object part of the cable and the value obtained by multiplying the change amount of the temperature of the part of the cable other than the diagnostic object part by the coefficient corresponding to the part of the cable other than the diagnostic object part. The coefficient corresponding to the diagnostic object part of the cable is set based on the environment around the diagnostic object part of the cable. The coefficient corresponding to the part of the cable other than the diagnostic object part is set based on the environment around the part of the cable other than the diagnostic object part. Based on the condition of the value representing the state of the diagnostic object part considering the state of the part of the cable other than the diagnostic object part, it includes that the value representing the state of the diagnostic object part considering the state of the part of the cable other than the diagnostic object part is greater than or equal to the determination value. The determination value is set based on the coefficient corresponding to the diagnostic object part of the cable and the coefficient corresponding to the part of the cable other than the diagnostic object part.

7. The diagnostic method according to claim 4, wherein Based on the difference between the time when the temperature of the diagnostic object part of the cable starts to change and the time when the temperature of the part of the cable other than the diagnostic object part starts to change, the value representing the state of the diagnostic object part considering the state of the part of the cable other than the diagnostic object part is corrected.

8. A diagnostic program, wherein The diagnostic program causes a computer to execute the diagnostic method according to any one of claims 1 to 7.

9. A diagnostic device, wherein The diagnostic device has a control unit that executes the diagnostic method according to any one of claims 1 to 7.

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