Lightning strike monitoring system and lightning strike monitoring method

Abstract

Provided is a lightning strike monitoring system wherein: the change over time in vibration intensity at measurement points set along an optical fiber which is provided along a power transmission line is acquired per frequency by distributed acoustic sensing (DAS); the location of occurrence and time of occurrence of a lightning strike are acquired from a lightning strike location system (LLS); a span having a measurement point that includes a mode of change over time in vibration intensity which is due to a lightning strike among changes over time in vibration intensity per frequency in a prescribed period before and / or after the time of occurrence is extracted as a lightning strike detection span; of the lightning strike detection span, a span that exists within a prescribed distance from the location of occurrence is specified as a nearby span; and when the changes over time in vibration intensity per frequency in a prescribed period before and / or after the time of occurrence at a measurement point of the nearby span include a mode of change over time in vibration intensity which is due to a direct lightning strike in the nearby span, information indicating that there has been a direct lightning strike in the nearby span is generated.

Description

Lightning monitoring system and lightning monitoring method

[0001] The present invention relates to a lightning monitoring system and a lightning monitoring method.

[0002] Patent Document 1 describes a fault detection and location system that locates the location of a fault that occurs in an overhead power transmission line having an optical fiber composite overhead ground wire (OPGW). When a fault detector installed on a steel tower supporting the overhead power transmission line detects a fault, the fault detection and location system applies mechanical shock or vibration to the OPGW using an impact / vibration application device, and detects changes in the state of light propagating through the optical fiber. The fault detection and location system locates the location of a lightning strike by detecting changes over time in the polarization state of light propagating through the optical fiber combined with the OPGW due to lightning current.

[0003] Patent Document 2 describes an abnormality detection device that generates vibration information for a frequency range including the natural frequency of the OPGW using an optical fiber vibration measurement system (DAS: Distributed Acoustic Sensing) that calculates vibrations caused by expansion and contraction of the optical fiber based on the time from when pulsed light is incident on the optical fiber of the OPGW until the backward Rayleigh scattered light returns, and the phase difference and intensity of the backward Rayleigh scattered light, and detects abnormalities in the power transmission equipment based on the generated vibration information.

[0004] JP 10-177055 A JP 2023-50257 A

[0005] "Investigation into the feasibility of measuring lightning impact on CFRP composite materials using optical fiber sensors", Akimatsu Yoshiaki, Kageyama Kazuo, Murayama Hideaki, Kanazawa Institute of Technology, Materials Systems Research Institute, [online], Internet <URL: https: / / www.jstage.jst.go.jp / article / zairyosystem / 34 / 0 / 34_51 / _article / -char / ja / >, retrieved October 20, 2023

[0006] Direct lightning strikes on power transmission and transformation equipment such as power lines, transmission towers, and substations can lead directly to accidents and breakdowns. Therefore, when maintaining power transmission equipment, it is necessary to monitor the lightning strike situation on power transmission equipment in real time, quickly understand the impact of a direct lightning strike, and, if necessary, take prompt action to restore the system.

[0007] The fault detection and location locating system described in Patent Document 1 locates the location of a lightning strike by detecting the time change in the polarization state of light propagating through the optical fiber of the OPGW due to the lightning current. However, this system requires the installation of fault detection devices and shock / vibration application devices on each steel tower, which is very costly.

[0008] Patent Document 2 describes detecting abnormalities in power transmission equipment based on vibration information generated using a fiber optic vibration measurement system (DAS). However, the document does not describe a mechanism for detecting whether or not a power transmission equipment has been directly struck by lightning or the effects of such a strike.

[0009] The Lightning Location System (LLS) is a system for obtaining real-time information on the date and time of lightning strikes, their location (latitude and longitude), the magnitude of the lightning current, the amount of charge, etc. However, the accuracy of the LLS in determining the location of lightning strikes is only a few hundred meters, and it is not always possible to accurately identify the location of lightning strikes.

[0010] The present invention has been made in consideration of the above background, and aims to provide a lightning monitoring system and a lightning monitoring method that can quickly and appropriately provide information regarding the impact of lightning strikes on power transmission equipment.

[0011] One means for solving the above problem is a lightning monitoring system comprising an optical analysis unit and an information processing device, which acquires, using a Distributed Acoustic Sensing (DAS), the time change in vibration intensity for each frequency of an optical fiber at measurement points set along the optical fiber installed along a power transmission line, and acquires information indicating the location and time of the lightning strike from a communicatively connected Lightning Location System (LLS), extracts as lightning detection spans those spans having the measurement points where the time change in vibration intensity for each frequency during at least any specified period before or after the time of the strike includes the pattern of the time change in vibration intensity caused by the lightning strike, and of the extracted lightning detection spans, identifies spans that are within a specified distance from the location of the strike as nearby spans, and generates information indicating the identified nearby spans.

[0012] Other problems and solutions disclosed in the present application will be made clear in the detailed description and drawings.

[0013] According to the present invention, it is possible to provide information regarding the influence of lightning strikes on power transmission facilities promptly and appropriately.

[0014] FIG. 1 is a diagram showing a schematic configuration of a lightning strike monitoring system. FIG. 2 is a diagram explaining a mechanism for measuring vibration states using a DAS. FIG. 3 is a diagram showing an example of the positional relationship between a lightning strike occurrence point and power transmission equipment. FIG. 4 is an example of temporal changes in vibration intensity for each frequency of an optical fiber. FIG. 5 is a diagram showing the main configuration of a lightning strike monitoring device. FIG. 6 is a diagram showing the main functions of the lightning strike monitoring device. FIG. 7 is a flowchart explaining lightning strike monitoring processing. FIG. 8 is an example of a lightning strike information presentation screen.

[0015] The present invention will be described below in accordance with one embodiment with reference to the accompanying drawings. At least the following matters will become clear from the description of this specification and the accompanying drawings. In the following description, the letter "S" added before a reference numeral means a processing step.

[0016] 1 shows a schematic configuration of a lightning monitoring system 1 according to an embodiment of the present invention. The lightning monitoring system 1 includes a lightning monitoring device 100 installed in a substation 6 or the like, and a lightning location system (hereinafter referred to as "LLS 300").

[0017] The lightning monitor 100 is configured using an information processing device (computer). The lightning monitor 100 is communicably connected to the LLS 300 via a communication network (not shown). The communication network may be, for example, a local area network (LAN), a wide area network (WAN), the internet, a power line communication (PLC), a public communication network, or a dedicated line.

[0018] The lightning monitoring device 100 uses an optical fiber 4a of an OPGW4 (optical fiber composite overhead ground wire) installed on the power transmission line 3 as a vibration detection sensor, and acquires the vibration state at each of a plurality of measurement positions (hereinafter referred to as "measurement points") set along the optical fiber 4a by a technique (distributed acoustic sensing (DAS)) that measures the vibration state (vibration intensity, vibration frequency) due to the expansion and contraction of the optical fiber 4a at each of the measurement points. With DAS, the vibration state at each measurement point is acquired, for example, using the principle of a C-OTDR (coherent detection optical time domain reflectometer).

[0019] FIG. 2 illustrates how the lightning monitor 100 measures the vibration state at each measurement point using a DAS. As shown in the figure, the lightning monitor 100 incidents an optical pulse (laser pulse, hereinafter also referred to as "incident light") from the end face of the optical fiber 4a and measures the rate of change (≒ expansion / contraction frequency) of the phase difference of the backscattered light of the optical pulse at each measurement point. The phase difference is estimated from the intensity change due to interference between the backscattered light. Based on the measured rate of change, the lightning monitor 100 then determines the vibration frequency (e.g., vibration frequency in the range of up to 10 kHz) of the longitudinal and shear waves of the optical fiber 4a at each measurement point. The lightning monitor 100 also determines the vibration intensity (spectral intensity, vibration amplitude) at each measurement point based on the phase difference for each vibration frequency. The lightning monitor 100 also determines the position (distance from the end face) of each measurement point based on the elapsed time between when the incident light is incident on the end face and when the return light is received.

[0020] The measurement points are set, for example, along the optical fiber at predetermined intervals d (m) that are shorter than the span of the transmission tower 2 (0 (m), d (m), ..., N (m), N + d (m), N + 2d (m)). For example, as shown in Figure 1, if the predetermined interval d is 5 (m) and measurement points are set over a maximum range of 70 (km) of the power transmission line 3, approximately 14,000 measurement points will be set along the optical fiber. The lightning monitoring device 100 acquires information about the impact and vibration caused by lightning strikes at each measurement point based on the vibration state at each measurement point.

[0021] Returning to FIG. 1 , the LLS 300 acquires information (hereinafter referred to as "lightning information") about lightning strikes that occur in areas where power transmission facilities (such as the transmission tower 2, the power transmission line 3, and the substation 6) are located, and provides (transmits) the acquired lightning strike information to the lightning strike monitoring device 100 promptly (in real time). The LLS 300 captures the electromagnetic field generated by lightning strikes and acquires the lightning strike information using, for example, a time difference of arrival method. The lightning strike information includes information indicating the date and time of the lightning strike and its location (latitude and longitude). The location accuracy (location error) of the LLS 300 for the lightning strike location is on the order of several hundred meters.

[0022] 3A shows an example of the positional relationship between the point of lightning strike and power transmission equipment when lightning strikes an area around the power transmission equipment. The figure shows that lightning struck at point a near the power transmission towers 2 whose identifiers (hereinafter referred to as "tower IDs") are "19" to "23." When lightning strikes, vibrations (sounds) caused by the lightning strike (thunder) occur in the OPGWs 4 in the spans of the power transmission towers 2 located around the point of lightning strike.

[0023] 3B shows an example of the temporal change in vibration intensity for each frequency of the optical fiber 4a measured at specific measurement points on each of the spans with span identifiers (hereinafter referred to as "span IDs") "20_21," "21_22," "22_23," and "23_24" shown in FIG. 3A. In each graph, time flows from top to bottom on the page. The shades of color in the figure represent the vibration intensity (arbitrary units) for each frequency (the lighter the color, the greater the vibration intensity).

[0024] The vibrations (sounds) caused by lightning strikes begin a little before the strike and continue for a while after it occurs. Therefore, each graph in the figure shows that vibrations caused by lightning strikes are observed for at least a certain period (often several minutes) before or after the time when lightning struck point a.

[0025] As shown in the figure, strong vibration intensity (vibration intensity above a preset threshold) is observed at the same frequency (a frequency centered around 8.25 Hz) in at least a predetermined period before or after the lightning strike in the graphs for adjacent spans with span IDs "21_22" and "22_23" located close to point a. It has been found that when thunder has a sound pressure above a predetermined level, vibrations in the same frequency band are observed not only across one span but across multiple spans. Therefore, it can be determined that these vibrations are caused by the same lightning strike.

[0026] On the other hand, when a span is directly struck by lightning, it is known that multiple strong vibrations (vibration intensities greater than or equal to a preset threshold) are observed across multiple frequency bands during at least a predetermined period before or after the lightning strike. However, no such vibrations are observed in these graphs. Therefore, it can be concluded that no direct lightning strikes occurred on these spans.

[0027] Furthermore, in the graph for the span with span ID "23_24," strong vibrations are observed across a wide frequency range (5 to 7.5 Hz). However, no such vibrations are observed in the 8 to 9 Hz frequency band where strong vibrations are observed in the graphs for span IDs "21_22" and "22_23." Therefore, it can be determined that the strong vibrations observed in the graph for the span with span ID "23_24" are caused by a lightning strike different from the lightning strike that occurred at point a.

[0028] From the above perspective, the lightning monitoring device 100 provides information about lightning strikes that have occurred around the span and information about direct lightning strikes that have occurred on the span (power transmission equipment on the span) based on the time-dependent changes in the vibration state of the optical fiber 4a at each frequency obtained at the measurement points on each span.

[0029] 4A is a diagram showing the main components of the lightning monitoring device 100. As shown in the figure, the lightning monitoring device 100 includes a processor 101, a main memory device 102 (memory), an auxiliary memory device 103 (external memory device), an input device 104, an output device 105, a communication device 106, and an optical analysis unit 107. These are communicatively connected via a bus, a communication cable, or the like. Note that all or part of the lightning monitoring device 100 may be realized using virtual information processing resources, such as a virtual server provided by a cloud system.

[0030] The processor 101 is configured using, for example, a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a GPU (Graphics Processing Unit), an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), an AI (Artificial Intelligence) chip, etc.

[0031] The main memory device 102 is a memory device used when the processor 101 executes a program, and is, for example, a read-only memory (ROM), a random access memory (RAM), or a non-volatile memory (NVRAM).

[0032] The auxiliary storage device 103 is a device that stores programs and data, and can be configured, for example, with an SSD (Solid State Drive), a hard disk drive, or an optical storage device (CD (Compact Disc), DVD (Digital Versatile Disc), etc.). Programs and data can be read into the auxiliary storage device 103 from other information processing devices equipped with non-transitory recording media or non-transitory storage devices via a recording medium reading device or a communication device 106. The programs and data stored in the auxiliary storage device 103 are read into the main storage device 102 as needed.

[0033] The input device 104 is an interface that accepts input of information from the outside, and is, for example, a keyboard, a mouse, a touch panel, a voice input device, or the like.

[0034] The output device 105 is an interface that outputs various information such as processing progress and processing results to the outside. The output device 105 is, for example, a display device (liquid crystal monitor, LCD (Liquid Crystal Display) or the like) that visualizes the various information, a device that converts the various information into audio (audio output device (speaker or the like)), or a device that converts the various information into text (printer or the like). Note that, for example, the information processing device 10 may be configured to input and output information to and from other devices via the communication device 106.

[0035] The input device 104 and the output device 105 constitute a user interface that realizes interactive processing with the user (receiving information, providing information, etc.).

[0036] The communication device 106 is a device that realizes communication with other devices via a communication network (such as a local area network (LAN), a wide area network (WAN), the Internet, a public communication network, or a dedicated line). The communication device 106 is a wired or wireless communication interface that realizes communication with other devices via a communication medium, such as a network interface card (NIC), a wireless communication module, or a universal serial bus (USB) module.

[0037] The optical analyzing unit 107 is a device that measures the vibration state of a measurement point using a DAS and includes a vibration measuring device using a C-OTDR and a signal processing circuit. The optical analyzing unit 107 includes a CW (continuous wave) laser light source that generates an optical pulse (laser light) to be input to the end face of the optical fiber 4a, an optical pulse generator, an optical amplifier, optical devices (photodetector, optical interferometer), a signal processing circuit (phase calculation circuit, etc.), etc. The optical analyzing unit 107 and the optical fiber 4a are connected, for example, by optically connecting the output of the laser light source of the optical analyzing unit 107 to a connection port (socket) of the core wire of an OPGW installed in a substation. Therefore, the connection does not cause any impact on the power system, such as a power outage.

[0038] The lightning monitoring device 100 may be equipped with, for example, an operating system, a file system, a DBMS (DataBase Management System) (relational database, NoSQL, etc.), a KVS (Key-Value Store), etc.

[0039] The various functions of the lightning monitoring device 100 are realized by the processor 101 reading and executing programs stored in the main memory device 102, or by the hardware (FPGA, ASIC, AI chip, etc.) that constitutes the lightning monitoring device 100. The lightning monitoring device 100 stores various pieces of information (data), for example, as tables in a database or files managed by a file system.

[0040] 4B is a block diagram illustrating the main functions of the lightning monitor 100. As shown in the figure, the lightning monitor 100 includes a memory unit 110, a vibration state measurement unit 120, a lightning information acquisition unit 125, a lightning detection span extraction unit 130, a nearby span identification unit 132, a direct lightning hit determination unit 135, an equipment abnormality determination unit 140, a response information generation unit 145, and a lightning information presentation unit 150.

[0041] Of the above functions, the memory unit 110 stores vibration status for each measurement point 111, lightning strike information 112, lightning strike detection span 113, nearby span 114, direct lightning strike presence / absence determination result 115, equipment abnormality presence / absence determination result 116, response information 117, and power transmission equipment information 118.

[0042] The vibration state measurement unit 120 uses the DAS to measure the time-series data of the vibration state (vibration intensity, vibration frequency) at each measurement point on each span, and manages the measurement results as the vibration state for each measurement point 111. The vibration state for each measurement point 111 includes, for example, the information shown in each graph in FIG. 3B .

[0043] The lightning strike information acquisition unit 125 receives lightning strike information from the LLS 300 and manages the received lightning strike information as lightning strike information 112. The lightning strike information 112 includes information indicating at least the location (latitude and longitude) of the lightning strike and the date and time of the lightning strike. The lightning strike information 112 includes, for example, the information displayed in FIG. 3A .

[0044] The lightning detection span extraction unit 130 extracts spans (hereinafter referred to as "lightning detection spans") that contain vibration states due to lightning strikes based on the vibration states for each measurement point 111, and manages the span IDs of the extracted spans as lightning detection spans 113. For example, the lightning detection span extraction unit 130 extracts spans having measurement points that contain a pattern of time-varying vibration intensity due to lightning strikes in the time-varying vibration intensity for each frequency during at least any predetermined period before and after the time of the lightning strike as lightning detection spans. The pattern of time-varying vibration intensity due to lightning strikes is, for example, that vibrations of magnitude equal to or greater than a predetermined threshold are observed at the same frequency (same frequency range) for at least any predetermined period before and after the time of the lightning strike (a predetermined period that takes into account the time it takes for sound waves from the lightning strike to reach the power transmission equipment) for the measurement points of each of a plurality of adjacent spans.

[0045] The nearby span identification unit 132 determines whether or not there is a span (hereinafter referred to as a "neighboring span") among the lightning detection spans that is located near the lightning strike location indicated by the lightning strike information 112, and if so, manages the span ID of the span as the nearby span 114. The nearby span identification unit 132 obtains, for example, information indicating the location of each span from the power transmission facility information 118, and identifies spans that are located within a predetermined distance (e.g., 1.5 km) from the lightning strike location as nearby spans. The power transmission facility information 118 includes tower IDs and information on power transmission facilities associated with the span IDs (such as the location of the power transmission tower 2 and information on the power transmission facilities installed in the vicinity of the power transmission tower 2).

[0046] The direct lightning hit determination unit 135 determines whether the power transmission equipment in the nearby span has been hit by direct lightning based on the vibration state of the nearby span, and if so, manages information indicating this as the direct lightning hit determination result 115. For example, the direct lightning hit determination unit 135 determines that the nearby span has been hit by direct lightning when the time change in vibration intensity for each frequency during at least any predetermined period before or after the occurrence of the lightning at the measurement point in the nearby span includes a time change pattern of vibration intensity caused by a direct lightning hit to the nearby span. The time change pattern of vibration intensity caused by a direct lightning hit to the nearby span is, for example, when multiple vibrations having magnitudes equal to or greater than a predetermined threshold are observed across multiple frequency bands during at least any predetermined period before or after the lightning strike.

[0047] When the direct lightning hit determination unit 135 determines that the power transmission equipment in the nearby span has been hit by a direct lightning strike, the equipment abnormality determination unit 140 determines whether an abnormality (such as a broken wire or partial deformation) has occurred in the power transmission equipment and manages the determination result in the equipment abnormality determination result 116. The equipment abnormality determination unit 140 determines whether an abnormality has occurred in the power transmission equipment in the nearby span, for example, by comparing the natural frequency of the optical fiber 4 a determined from the vibration intensity for each frequency after the time of the lightning strike at the measurement point in the nearby span with the natural frequency of the optical fiber 4 a determined from the vibration intensity for each frequency in the nearby span under normal conditions (before the direct lightning hit) that have been stored in advance. For example, the equipment abnormality determination unit 140 determines that an abnormality has occurred in the power transmission equipment in the nearby span when a predetermined number or more natural frequencies different from the natural frequency under normal conditions are observed.

[0048] The correspondence information generation unit 145 generates information indicating nearby spans that have been directly struck by lightning (span IDs of the nearby spans) and information indicating actions that should be taken by a power transmission equipment manager (such as a maintenance worker) for the nearby spans (power transmission equipment in the nearby spans) (hereinafter referred to as "response information"), and manages the generated response information as response information 117. The response information generation unit 145 acquires information necessary for generating the response information from the power transmission equipment information 118. For example, the response information generation unit 145 manages the response information in association with span IDs in the power transmission equipment information 118, and generates the response information by comparing the span IDs of nearby spans that have been directly struck by lightning with the power transmission equipment information 118.

[0049] The lightning strike information presentation unit 150 presents to the administrator (for example, by displaying on a display device) the contents of the correspondence information 117. For example, the lightning strike information presentation unit 150 generates a screen (for example, a lightning strike information presentation screen 600 described later) that describes the contents of the correspondence information 117 and presents it to the administrator.

[0050] 5 is a flowchart illustrating the process (hereinafter referred to as "lightning monitor process S500") performed by the lightning monitor device 100. The lightning monitor process S500 will be described below with reference to FIG.

[0051] It is assumed in the following explanation that the LLS 300 generates lightning strike information immediately upon the occurrence of a lightning strike and transmits the generated lightning strike information to the lightning strike monitoring device 100 (it may also be possible for the lightning strike monitoring device 100 to access the LLS 300 and for the lightning strike monitoring device 100 to read (acquire, receive) the lightning strike information from the LLS 300). It is also assumed that the vibration state measuring unit 120 of the lightning strike monitoring device 100 measures the time change in the vibration state (vibration intensity, vibration frequency) of each measurement point on each span in real time using DAS, and manages the latest vibration state of each measurement point as the vibration state per measurement point 111.

[0052] As shown in the figure, the lightning strike information acquisition unit 125 waits in real time to receive lightning strike information from the LLS 300 (S511: No). When the lightning strike information acquisition unit 125 receives lightning strike information from the LLS 300 (S511: Yes), the lightning strike information acquisition unit 125 manages the received lightning strike information as lightning strike information 112.

[0053] In S512, the lightning detection span extraction unit 130 extracts a lightning detection span based on the vibration state for each measurement point 111, and manages information indicating the extracted span as the lightning detection span 113.

[0054] In S513, the nearby span identification unit 132 determines whether or not there is a nearby span for the lightning strike location indicated by the lightning strike information 112 received in S511. If it is determined that there is a nearby span (S513: Yes), the nearby span identification unit 132 manages the information indicating the nearby span as the nearby span 114, and then the process proceeds to S514. On the other hand, if the nearby span identification unit 132 determines that there is no nearby span (S513: No), the process returns to S511.

[0055] In S514, the direct lightning hit determination unit 135 determines whether the nearby span (the power transmission equipment) has been hit by direct lightning based on the vibration state of the nearby span identified in S513 (the vibration state acquired from the measurement point vibration state 111 for the identified nearby span). If the direct lightning hit determination unit 135 determines that the nearby span has been hit by direct lightning (S514: Yes), the process proceeds to S515. On the other hand, if the direct lightning hit determination unit 135 determines that the nearby span has not been hit by direct lightning (S514: No), the process returns to S511.

[0056] In S515, the equipment abnormality determination unit 140 determines whether an abnormality has occurred in the power transmission equipment in the nearby span identified in S513. If the equipment abnormality determination unit 140 determines that an abnormality has occurred in the power transmission equipment in the nearby span identified in S513 (S515: Yes), information indicating the determination result is managed in the equipment abnormality determination result 116, and then the processing proceeds to S516. On the other hand, if the equipment abnormality determination unit 140 determines that no abnormality has occurred in the power transmission equipment in the nearby span identified in S513 (S515: No), the processing proceeds to S517.

[0057] In S516, the correspondence information generation unit 145 generates correspondence information for the nearby span in which it is determined that an abnormality has occurred, and manages the generated correspondence information as the correspondence information 117.

[0058] In S517, the lightning strike information presentation unit 150 presents to the administrator the contents of the lightning strike information 112, information (span ID, etc.) about the nearby span determined to have been hit by direct lightning in S514, the contents of the correspondence information 117, etc.

[0059] FIG. 6 shows an example of a screen (hereinafter referred to as a "lightning strike information presentation screen 600") that the lightning strike information presentation unit 150 presents to the administrator.

[0060] As shown in the figure, the lightning strike information presentation screen 600 shown as an example has a display field 611 for lightning strike information, a display field 612 for direct lightning strike information, and a display field 613 for corresponding information.

[0061] Of these, the lightning strike information display field 611 displays the content of the lightning strike information acquired (received) by the lightning strike information acquisition unit 125 from the LLS 300 in S511 of FIG. 5, for example, in the format shown in FIG. 3A.

[0062] The direct lightning strike information display field 612 displays information (span ID) indicating nearby spans that the direct lightning strike determination unit 135 determined to have been hit by direct lightning in S514 of Fig. 5. By referring to the contents of the direct lightning strike information display field 612, the administrator can easily identify nearby spans that may be affected by lightning.

[0063] Response information is displayed in the response information display field 613. By referring to the contents of the response information display field 613, the administrator can quickly confirm the response that should be taken for the nearby span that was directly struck by lightning, and can take the necessary response efficiently.

[0064] As described above, the lightning monitoring system 1 of this embodiment can quickly provide the manager with information on the impact of a direct lightning strike on the power transmission equipment and information indicating the response to be taken for power transmission equipment in a nearby span that is determined to have been hit by direct lightning, based on the lightning strike information acquired from the LLS 300 and the information acquired using the DAS. The information provided by the lightning monitoring system 1 allows the manager to quickly and appropriately grasp the impact of a lightning strike on the power transmission equipment, and to efficiently perform patrols, inspections, and maintenance work on the power transmission equipment.

[0065] Furthermore, the lightning monitoring system 1 of this embodiment can be easily implemented by utilizing the mechanism of an optical fiber vibration measurement system (DAS) without providing any special device on the transmission tower 2 or the like.

[0066] The above-described embodiments are provided to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit thereof, and equivalents thereof are also included in the present invention.

[0067] For example, the lightning strike position may be estimated from the difference in the time when vibrations caused by thunder were observed for each span, thereby improving the accuracy of estimating the lightning strike position.

[0068] Also, for example, the lightning strike information presentation unit 150 may receive a span (span ID) designation from the administrator, and present the contents of the vibration state at each measurement point 111 corresponding to the received span to the administrator (for example, in the form shown in FIG. 3B ).

[0069] Furthermore, for example, extraction of lightning detection spans by the lightning detection span extraction unit 130 and determination of whether or not a direct lightning strike has occurred at a power transmission facility in a nearby span by the direct lightning strike determination unit 135 may be performed using a machine learning model that has been trained to output a determination result of whether or not a direct lightning strike has occurred at the lightning detection span or the nearby span when feature quantities extracted by performing image recognition processing on the graph (image) shown in Figure 3B are input as explanatory variables.

[0070] Furthermore, for example, the lightning monitoring device 100 may acquire information about the lightning strike power from the vibration state acquired by the DAS, and present (for example, on the lightning strike information presentation screen 600) the acquired information and information about the reliability of the information (consistency with the charge amount and current value acquired from the LLS 300) (for information on acquiring lightning strike power, see, for example, Non-Patent Document 1, "Investigation into the feasibility of measuring lightning impact on CFRP composite materials using optical fiber sensors," by Akimatsu Yoshiaki, Kageyama Kazuo, Murayama Hideaki, Materials Systems Research Institute, Kanazawa Institute of Technology).

[0071] REFERENCE SIGNS LIST 1 Lightning monitoring system 2 Transmission tower 3 Power transmission line 4 OPGW 4a Optical fiber 100 Lightning monitoring device 107 Optical analysis unit 110 Storage unit 111 Vibration state at each measurement point 112 Lightning information 113 Lightning detection span 114 Nearby span 115 Direct lightning hit presence / absence determination result 116 Equipment abnormality presence / absence determination result 117 Correspondence information 118 Power transmission equipment information 120 Vibration state measurement unit 125 Lightning information acquisition unit 130 Lightning detection span extraction unit 132 Nearby span identification unit 135 Direct lightning hit presence / absence determination unit 140 Equipment abnormality presence / absence determination unit 145 Correspondence information generation unit 150 Lightning information presentation unit S500 Lightning monitoring process 600 Lightning information presentation screen

Claims

1. A lightning monitoring system comprising an optical analysis unit and an information processing device, which acquires, using a Distributed Acoustic Sensing (DAS), the time change in vibration intensity for each frequency of an optical fiber at measurement points set along the optical fiber installed along a power transmission line, acquires information indicating the location of the lightning strike and the time of the lightning strike from a communicatively connected Lightning Location System (LLS), extracts as a lightning detection span a span having the measurement point where the time change in vibration intensity for each frequency during at least any specified period before or after the time of the strike includes a pattern of the time change in vibration intensity caused by the lightning strike, and identifies, of the extracted lightning detection spans, spans that are within a specified distance from the location of the strike as nearby spans, and generates information indicating the identified nearby spans.

2. A lightning monitoring system as described in claim 1, wherein the lightning detection span is extracted based on the fact that vibrations of a magnitude equal to or greater than a preset threshold value are observed at the same frequency during at least any specified period before or after the occurrence time at the measurement points of each of a plurality of adjacent spans.

3. A lightning monitoring system as described in claim 1, which generates information indicating that a direct lightning strike has occurred on the nearby span when the change in vibration intensity over time for each frequency during at least any specified period before or after the time of occurrence of the measurement point on the nearby span includes a pattern of change in vibration intensity over time resulting from a direct lightning strike on the nearby span.

4. A lightning monitoring system as described in claim 3, which determines whether or not there has been a direct lightning strike in the nearby span based on the observation of multiple vibrations having a magnitude equal to or greater than a preset threshold across multiple frequency bands during at least any specified period before or after the time of the lightning strike.

5. A lightning monitoring system as described in claim 3, which determines whether or not an abnormality has occurred in the power transmission equipment in the nearby span by comparing the natural frequency of the optical fiber determined from the vibration intensity for each frequency after the occurrence time at the measurement point in the nearby span with the natural frequency of the optical fiber determined from the vibration intensity for each frequency in the nearby span under normal conditions that has been stored in advance, and generates information indicating the result of the determination.

6. A lightning monitoring system according to claim 1, wherein information indicating the nearby span is output via a user interface.

7. A lightning monitoring system according to claim 3, wherein information indicating that a direct lightning strike has occurred on the nearby span is output via a user interface.

8. A lightning monitoring system as claimed in claim 5, wherein, if it is determined that an abnormality has occurred in the power transmission equipment in the nearby span, information indicating that fact is output via a user interface.

9. A lightning monitoring system as claimed in claim 3, which stores information indicating the action to be taken in the event of a direct lightning strike for each span, and outputs, via a user interface, information indicating the action to be taken for the nearby span determined to have been struck by direct lightning.

10. A lightning monitoring method in a lightning monitoring system including an optical analysis unit and an information processing device, wherein the information processing device executes the following steps: acquiring the time change in vibration intensity for each frequency of an optical fiber at measurement points set along an optical fiber attached along a power transmission line using a distributed acoustic sensing (DAS); acquiring information indicating the location of the lightning strike and the time of the lightning strike from a communicatively connected lightning location system (LLS): extracting, as a lightning detection span, a span having the measurement point where the time change in vibration intensity for each frequency during at least any specified period before or after the time of the strike includes a pattern of the time change in vibration intensity caused by the lightning strike; and identifying, from among the extracted lightning detection spans, spans that are within a specified distance from the location of the strike as nearby spans, and generating information indicating the identified nearby spans.

11. A lightning monitoring method as described in claim 10, further comprising the step of: generating information indicating that a direct lightning strike has occurred on the nearby span when the change in vibration intensity over time for each frequency during at least any specified period before or after the time of occurrence of the measurement point on the nearby span includes a pattern of change in vibration intensity over time resulting from a direct lightning strike on the nearby span.

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