Buried object preventive maintenance system and buried object preventive maintenance method

Abstract

To detect an excavation position with high accuracy with a simple configuration to prevent damage to an underground buried structure.SOLUTION: A buried structure preventive maintenance system has: a long-sized buried structure that is buried in the ground; an optical fiber that is buried in the ground together with the buried structure and is disposed along an extension direction of the buried structure; a monitoring device that is connected with one end of the optical fiber and determines vibration of excavation on the basis of backscattered light emitted from one end of the optical fiber on which light is incident from the one end; and a notification unit that notifies of a portion of the buried structure corresponding to a place of occurrence of vibration of excavation as an excavation position.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a buried object preventive maintenance system and buried object preventive maintenance method capable of preventing external damage to buried objects. [Background technology]

[0002] Conventionally, in order to prevent erroneous excavation of power cables buried underground, methods using warning tape indicating the buried location and methods using optical fibers to measure vibrations have been known.

[0003] The method of using warning tape indicating the buried location only issues an alarm after the fact, whereas the method of measuring vibrations using optical fiber makes it possible to monitor the current buried location and therefore predict the on-site situation in advance, enabling an early warning to be issued.

[0004] For example, Patent Document 1 discloses an alarm device that prevents erroneous excavation of buried objects by using a single-mode optical fiber that propagates light in a fundamental mode and a multimode optical fiber that is connected to the single-mode optical fiber and propagates light in a higher-order mode.

[0005] In this device, when the multimode optical fiber is bent, the light that is propagated in higher modes and reflected at the reflecting section and returned to the single-mode optical fiber is measured, thereby detecting vibrations in the surrounding area in which the single-mode optical fiber and multimode optical fiber are placed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2020-510269 Summary of the Invention [Problem to be solved by the invention]

[0007] Meanwhile, in Patent Document 1, a single-mode optical fiber and a multimode optical fiber are used, and the light propagating through each is measured by a photoelectric emitter and a photoelectric receiver to generate an alarm for each of the single-mode and multimode optical fibers.

[0008] However, conventional methods detect all vibrations around the single-mode optical fiber and multimode optical fiber, so it is not possible to accurately determine where excavation is actually taking place in an underground buried object, and the detection accuracy is insufficient.

[0009] The present invention has been made in consideration of the above-mentioned points, and aims to provide a buried object preventive maintenance system and buried object preventive maintenance method that can detect and notify, with high accuracy, the excavation position corresponding to a buried object with a simple configuration, in order to prevent external damage to the buried object. [Means for solving the problem]

[0010] One aspect of the buried object preventive maintenance system according to the present invention is to Long-length cables buried underground Multiple Buried objects, Multiple The buried object Each of and is buried in the ground along the extending direction of the buried object. Adjacent to each buried object Arranged It is used for both preventive maintenance sensors and communications. R Multiple Fiber optics and A monitoring device that is connected to one end of the optical fiber and that discriminates vibrations caused by excavation based on backscattered light emitted from the one end of the optical fiber to which light is incident from the one end; a changeover switch that can freely switch the connection between the plurality of optical fibers and the monitoring device, and by this changeover, selects the optical fiber for use as the preventive maintenance sensor and connects it to the monitoring device; a notification unit that notifies a portion of the buried object corresponding to a location where vibrations are generated by the excavation as an excavation position; The configuration has the following.

[0011] One aspect of the buried object preventive maintenance method according to the present invention is to Buried in the ground Multiple A method for preventive maintenance of buried objects, which prevents trauma to buried objects caused by excavation, comprising the steps of: Multiple The underground buried object Each Throughout the entire length Adjacent to each buried object, it is used for both preventive maintenance sensors and communications. Optical fiber Each Arranged, Selecting and switching the plurality of optical fibers By inputting light into one end of the optical fiber, the vibrations of excavation are identified based on the backward scattered light emitted from the one end, and the part of the buried object corresponding to the location where the identified excavation vibrations are occurring is reported as the excavation position. Effect of the Invention

[0012] According to the present invention, it is possible to detect and notify an excavation position corresponding to a buried object with high accuracy and precision using a simple configuration. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing the overall configuration of a buried object preventive maintenance system according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a cross-sectional view of an underground cable. [Diagram 3] FIG. 1 illustrates a sound waveform having vibration characteristics related to excavation for trauma prevention. [Figure 4] FIG. 1 is a diagram showing an example of preventive maintenance performed in a buried object preventive maintenance system. [Diagram 5] FIG. 1 is a diagram showing an example of a waveform measured in a buried object preventive maintenance system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0015] <Overall configuration of buried object preventive maintenance system> FIG. 1 is a schematic diagram showing the overall configuration of a buried object preventive maintenance system according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the underground cable shown in FIG.

[0016] The buried object preventive maintenance system 1 shown in Fig. 1 installs an optical fiber 3 together with a power cable 2 as an object buried underground, and monitors vibrations (especially sounds) related to excavation work (digging work) by using the optical fiber 3 itself as a sensor. This makes it possible to accurately detect the location of any possible damage to the underground buried object (power cable 2) from the outside due to excavation work for water, gas, etc., and issues a notice and warning to protect the buried object (power cable 2) and ensure its safety.

[0017] The buried object preventive maintenance system 1, as an example, includes a power cable 2 laid underground 12, an optical fiber 3 arranged along the power cable 2, a monitoring device 70, a changeover switch (changeover SW) 72, and an alarm unit 74.

[0018] The power cable 2 as an underground buried object is, for example, a power cable (power transmission line) such as an OF cable buried underground. The power cable 2 is, for example, a part of a power cable laid between a substation and a power supply destination, and FIG. 1 shows the part of the power cable 2 laid between manholes 6 and 7.

[0019] The power cables 2 (2-1 to 2-6) are arranged in a cylindrical pipe 5 together with the optical fibers 3 (3-1 to 3-6). 1 and 2, a plurality of power cables 2-1 to 2-6 are laid out, and each of the power cables 2-1 to 2-6 is laid out in a pipe 5 together with an optical fiber 3. In FIG.

[0020] The optical fiber 3 is used as a sensor for preventing damage in the buried object preventive maintenance system 1, and is arranged along the power cable 2 laid underground. The optical fiber 3 is preferably arranged corresponding to the number of the power cables 2. For example, if a plurality of power cables 2 are arranged, the optical fiber 3 is arranged adjacent to each of the power cables 2 along each of the power cables 2. As shown in FIG. 3, in the cable section of the buried object preventive maintenance system 1, the optical fibers 3-1 to 3-6 are inserted into each of the pipes 5, and among these optical fibers 3-1 to 3-6, the optical fibers 3-3 and 3-4 may be used as sensors as appropriate. The rest may be used for communication. The optical fiber 3 may be used both as a sensor for preventive maintenance and for communication, and may be used selectively as appropriate for either one.

[0021] The optical fiber 3 is laid together with the existing power cable, and the existing optical fiber for transmitting and receiving communication signals, etc. can be used as appropriate. By using the existing optical fiber 3, it is possible to eliminate the effort of laying new optical fiber to construct the buried object preventive maintenance system 1.

[0022] A monitoring device 70 is connected to one end of the optical fiber 3 via a change-over switch 72, and the monitoring device 70 inputs light thereto and monitors the propagation state of the light.

[0023] The conduit 5 protects the power cable 2 and the optical fiber 3 when they are laid, and is laid underground to form an arrangement space for the power cable 2 and the optical fiber 3. The conduit 5 is, for example, a reinforced concrete pipe. Alternatively, the conduit 5 may be formed as a single unit from a concrete block. The conduit 5 may be formed by integrating a plurality of cylindrical conduits into a concrete block, and the power cables 2-1 to 2-6 and the optical fibers 3-1 to 3-6 may be arranged as pairs in a plurality of hollow portions extending in the longitudinal direction.

[0024] As shown in FIG. 2, the power cables 2 (2-1 to 2-6) are laid in a plurality of ducts 5, respectively, and the optical fibers 3 are laid along the power cables 2.

[0025] The optical fibers 3 (3-1 to 3-6) are arranged in a duct 5 together with the power cable 2 over the entire length of the power cable 2.

[0026] The changeover switch 72 can freely switch the connection between the monitoring device 70 and the optical fiber 3, and by switching this changeover switch 72, the optical fiber 3 corresponding to which power cable 2 (2-1 to 2-6) is selected and connected to the monitoring device 70. The monitoring device 70 selects which power cable 2-1 to 2-6 to monitor.

[0027] The monitoring device 70 monitors the propagation state of light in the optical fiber 3. Specifically, the monitoring device 70 inputs light from one end of the optical fiber 3, and measures and monitors the frequency characteristics, distortion, and intensity of the light based on the scattered light that returns to the one end, even when the optical fiber 3 is not straight, and detects vibrations related to excavation (particularly sounds generated during excavation work).

[0028] The monitoring device 70 performs optical sensing through the optical fiber 3 using, for example, an OTDR (Optical Time Domain Reflectometry).

[0029] The monitoring device 70 includes a light source unit that inputs light from one end 3a into the optical fiber 3, a coupler, a photodetector that detects backward scattered light from the one end via the coupler, a CPU that measures and analyzes the detection results of the photodetector, a storage unit, etc. The CPU acquires a waveform obtained by measuring the distribution of the optical fiber 3 based on the backward scattered light.

[0030] The monitoring device 70 monitors the scattered light (backward scattered light) returning to one end of the optical fiber 3 from which light is incident, and measures the longitudinal distribution of temperature and strain over the entire length of the optical fiber 3.

[0031] The monitoring device 70 observes the backscattered light as Rayleigh scattering, which is scattered light of the same wavelength as the light incident on the optical fiber 3, and Raman scattering and Brillouin scattering, which are scattered light of different wavelengths from the incident light, and senses the optical fiber 3 based on the properties of their respective intensities and frequencies. For example, the bend of the optical fiber 3 can be measured by Rayleigh scattering, the temperature can be measured by Raman scattering, and the strain can be measured by Brillouin scattering.

[0032] Based on the backward scattered light, the monitoring device 70 obtains the state of each portion extending in the longitudinal direction of the optical fiber 3 as a waveform, monitors this waveform as the waveform of the power cable 2 which is similarly arranged along the optical fiber 3, and detects sounds related to excavation work.

[0033] The monitoring device 70 monitors vibrations, including sounds related to excavation work, in the waveform acquired using the optical fiber 3, and determines at which part of the power cable 2 installed corresponding to the optical fiber 3 excavation work is being carried out. This also means detecting parts of the power cable 2 that may be damaged.

[0034] The monitoring device 70 monitors the waveform acquired using the optical fiber 3, and detects noise that may cause trauma, i.e., noise generated during excavation work. The monitoring device 70 stores, as waveform data, vibration characteristics of sounds generated during excavation work, such as sounds generated by driving vehicles, heavy machinery, and equipment, and sounds generated by working with tools.

[0035] FIG. 3 is a diagram illustrating a sound waveform having vibration characteristics related to excavation for trauma prevention. As examples of waveforms (sounds) used by the monitoring device 70 to determine the possibility of injury, Fig. 3A shows a waveform (sound) representing a truck while it is moving. Also, Fig. 3B shows a waveform (sound) representing a small vehicle (small truck) while it is moving. Fig. 3C shows a waveform (sound) representing a crawler vehicle, and Fig. 3D shows a waveform (sound) representing heavy machinery (e.g., a backhoe). Also, Fig. 3E shows a waveform (sound) representing excavation work with a shovel. In addition to these, the monitoring device 70 also has waveforms (sounds) of equipment, heavy machinery, vehicles, etc. used in construction work.

[0036] The monitoring device 70 compares the acquired waveform with pre-stored waveform (sound) data to monitor whether noise (excavation noise) that may cause damage to the buried power cable 2 is being emitted.

[0037] In addition to sound, the buried object preventive maintenance system 1 also focuses on the heat generation state of the power cable 2, and the monitoring device 70 also detects underground temperature changes (temperature gradient) that occur when a state in which some sand is continuously removed by excavation continues. That is, the monitoring device 70 detects underground temperature changes caused by excavation in the ground, that is, temperature changes at the excavation site, by using the backscattered light of the optical fiber 3.

[0038] This allows the monitoring device 70 to accurately detect the sound of excavating soil and sand at the detected position from vibrations, particularly the temperature gradient of the vibrations, and sound. In the buried object preventive maintenance system 1, when the monitoring device 70 determines that the noise (sound waveform) is one that may cause injury, it issues a warning to the worker working at the noise source via the alarm unit 74 to stop the work, thereby preventing damage to the power cable 2.

[0039] The notification unit 74 communicates with the monitoring device 70 wirelessly, and may communicate wirelessly or by wire. If the notification unit 74 is located at a construction site away from the monitoring device 70, it can quickly notify a user at the construction site of the determination of the monitoring device 70 or a warning issued by the monitoring device 70. In this way, the buried object preventive maintenance system 1 can quickly suspend construction work and ensure the maintenance of the power cable, which is a buried object. Furthermore, the monitoring device 70 may have a notification function.

[0040] <Preventive maintenance of power cables using buried object preventive maintenance system 1> Fig. 4 is a diagram showing an example of preventive maintenance performed in a buried object preventive maintenance system, and Fig. 5 is a diagram showing an example of a waveform measured in the buried object preventive maintenance system. In Fig. 5, the vertical axis shows the strength of the amplitude, and the horizontal axis shows time = distance from the monitoring device 70, and the monitoring device 70 detects (senses) and monitors in real time the state of light propagation in the optical fiber, that is, various vibrations acting on the power cable.

[0041] As shown in Fig. 4, in the buried object preventive maintenance system 1, it is assumed that construction work for water, gas, etc., by another company is being carried out by heavy machinery (backhoe) 9 on the ground 30 where the power cable 2 is buried underground 12. At this time, vibrations (specifically, sounds made during construction, including excavation sounds) K are generated around the power cable 2 due to the operation, excavation, etc. of the heavy machinery 9.

[0042] Then, in the monitoring device 70 connected to one end 3a of the optical fiber 3, a light source causes light to be incident on the optical fiber 3 from one end 3a, and a photodetector detects the backward scattered light that passes through the optical fiber 3 and exits from the one end 3a. In this way, the monitoring device 70 obtains a real-time waveform 15 in the optical fiber 3 shown in FIG. 5 as a waveform indicating the state of the power cable 2.

[0043] When the monitoring device 70 detects noise 15a in the real-time waveform (see Figure 5) 15 acquired using the optical fiber 3, it compares the waveform 15 with a pre-set and stored waveform (see Figure 3) indicating excavation work, and determines that the noise is vibration generated by excavation work.

[0044] Furthermore, if the monitoring device 70 can determine that the noise includes sounds generated by other construction works, the accuracy of the location of the excavation work at the noise source position can be further improved.

[0045] In addition, the monitoring device 70 detects, from the backscattered light or waveform 15, a change in soil temperature (temperature gradient) caused by a state in which a portion of soil and sand is continuously removed by excavation (continues over time).

[0046] In this way, the monitoring device 70 can pinpoint the location of the excavation work using sound and temperature changes, and can accurately and precisely identify it. The monitoring device 70 may use AI to determine the location of the excavation work using sound and temperature changes. This allows the location of the excavation work to be easily and precisely identified, and can warn workers and managers at the excavation work site by radio or other means that the power cable 2 is buried underground. This allows measures to be taken, such as stopping the work or changing the content of the work, to prevent damage to the power cable 2 underground.

[0047] <Action and effect> The buried object preventive maintenance system 1 includes a long power cable 2 and an optical fiber 3 buried in the ground, and a monitoring device 70. The optical fiber 3 is disposed in a pipeline 5 together with the power cable 2 and buried in the ground, and is disposed along the extending direction of the power cable 2. The monitoring device 70 is connected to one end 3a of the optical fiber 3, and monitors the backscattered light emitted from the one end 3a of the optical fiber 3 to which light is incident from the one end 3a, and identifies vibrations caused by excavating the ground based on the backscattered light. Then, the monitoring device 70 can detect a part of the power cable 2 corresponding to the location of the identified excavation vibration. In this way, the buried object preventive maintenance system 1 can detect and notify the excavation position corresponding to the power cable 2 (underground buried object) with high accuracy and precision, with a simple configuration.

[0048] According to the buried object preventive maintenance system 1, it is possible to prevent damage to power cables, which are buried underground and thus have been conventionally performed by after-the-fact maintenance, in a preventive manner.

[0049] Furthermore, according to the buried object preventive maintenance system 1, by detecting (detecting) changes in underground sounds that indicate temperature changes in addition to vibrations (sounds), the accuracy of the excavation position can be improved. In addition, by monitoring continuously 24 hours a day, the system constantly remembers and learns changes in the light propagation conditions in the optical fiber, and stores them as a database. By using the data appropriately in response to the events that occur, the system can increase the number of samples when identifying specific locations, thereby improving the accuracy of identifying excavation work.

[0050] If the optical fiber 3 has already been buried, the buried object preventive maintenance system 1 can be constructed using a system that uses the existing optical fiber and the already installed cable.

[0051] According to the buried object preventive maintenance system 1, by switching the monitoring line with the change-over switch 72, it is possible to monitor many power cables 2-1 to 2-6, which are power transmission lines, with one system.

[0052] Furthermore, if the buried object preventive maintenance system 1 is configured to transmit information to designated locations and contact devices (such as mobile phones) 24 hours a day when it detects an abnormality in the power cables 2-1 to 2-6, it will be possible to request a rapid response. The power cable in the buried object preventive maintenance system 1 may be a power cable laid on the seabed.

[0053] Furthermore, according to the buried object preventive maintenance system 1, for example, if there is a damage to a power cable, which is an underground buried object, the position of the damage to the power cable can be pinpointed by determining the bending of the optical fiber 3 at the corresponding position. This makes it unnecessary to carry out repair work at unnecessary positions, and simplifies and saves labor in repair work.

[0054] The above describes the embodiment of the present invention. Note that the above description is an example of a preferred embodiment of the present invention, and the scope of the present invention is not limited thereto. In other words, the description of the configuration of the above device and the shape of each part are examples, and it is clear that various modifications and additions to these examples are possible within the scope of the present invention. [Industrial Applicability]

[0055] The buried object preventive maintenance system of the present invention has the effect of being able to detect and notify the excavation position at any point of a buried object with high accuracy and precision with a simple configuration in order to prevent external damage to underground buried objects, and is useful for use with underground cables. [Explanation of symbols]

[0056] 1 Buried object preventive maintenance system 2, 2-1, 2-2, 2-3, 2-4, 2-5, 2-6 Power Cable 3, 3-1, 3-2, 3-3, 3-4, 3-5, 3-6 Optical fiber 3a One end 5 conduit 6, 7 Manhole 9 Heavy Machinery 12 underground 15 Waveform 15a Noise 30 ground 70 Monitoring equipment 72 Changeover switch 74 Notification Department K vibration

Claims

1. A plurality of long buried objects buried in the ground; A plurality of optical fibers that are buried in the ground together with each of the buried objects and are disposed adjacent to each of the buried objects along the extending direction of the buried objects, and are used for both preventive maintenance sensors and communications; A monitoring device that is connected to one end of the optical fiber and that discriminates vibrations caused by excavation based on backscattered light emitted from the one end of the optical fiber to which light is incident from the one end; a changeover switch that can freely switch the connection between the plurality of optical fibers and the monitoring device, and by this changeover, selects the optical fiber for use as the preventive maintenance sensor and connects it to the monitoring device; a notification unit that notifies a portion of the buried object corresponding to a location where vibrations are generated by the excavation as an excavation position; having Preventive maintenance system for buried objects.

2. The buried object is a power cable. The buried object preventive maintenance system according to claim 1.

3. The monitoring device compares a waveform indicating the optical propagation state of the optical fiber acquired based on the backscattered light with a waveform indicating the vibration related to the excavation, and determines the vibration related to the excavation.

3. A buried object preventive maintenance system according to claim 2.

4. The vibration of the excavation is a sound generated during excavation, The monitoring device determines a portion of the buried object corresponding to a portion of the optical fiber where the sound is generated based on the sound. The buried object preventive maintenance system according to claim 1.

5. the monitoring device monitors a temperature change in the ground caused by the excavation based on the backscattered light. The buried object preventive maintenance system according to any one of claims 1 to 4.

6. A method for preventive maintenance of buried objects, which prevents damage caused by excavation to a plurality of buried objects buried underground, comprising the steps of: an optical fiber for both a preventive maintenance sensor and communication is provided adjacent to each of the buried objects over the entire length of each of the buried objects; A plurality of the optical fibers are selected and switched, and light is input from one end of the switched optical fiber, and based on the backscattered light output from the one end, vibrations due to excavation are discriminated, and the portion of the buried object corresponding to the location where the discriminated vibrations due to excavation are generated is notified as an excavation position. Preventive maintenance methods for buried objects.

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