Water leakage detection system

Abstract

The present disclosure provides a water leakage detection system comprising an optical fiber that is disposed in the vicinity of a water pipeline, a vibration measuring instrument that outputs vibration data representing a variation over time in vibrations acting on at each point along the length direction of the optical fiber, and an analysis processing unit that analyzes the vibration data, wherein the analysis processing unit estimates a suspected water leakage point in the water pipeline by detecting vibrations unique to water leakage from the vibration data.

Description

Water Leak Detection System

[0001] The present disclosure relates to a water leak detection system that detects water leaks in a water pipeline using optical fibers arranged near the water pipeline.

[0002] There are over 650,000 km of water supply pipelines laid in Japan, and the pipelines that were installed during the first peak construction period in the late 1960s are due for replacement, but the replacement rate remains at around 0.7%. As water pipelines will continue to deteriorate in the future, it has become an important issue from the perspective of resource conservation to conduct regular leak inspections and find leak points early.

[0003] Water leak detection typically involves the use of sound-tuning rods or water leak detectors (Non-Patent Document 1). However, water leak detection using these technologies requires listening to sounds at locations every tens to 50 centimeters, which makes on-site investigations time-consuming. Furthermore, because engineers need the skills to distinguish between water leak sounds and other noises, there are issues with the cost and time required to train engineers, which can take several years or more.

[0004] Equipment "Investigation Stick," Housing Renovation and Dispute Resolution Center, Public Interest Foundation, Housing Dispute Resolution Technology Related Materials Collection, https: / / reference.chord.or.jp / sr / ks / kt / ocb.html

[0005] The present disclosure aims to enable remote detection of suspected water leak points in water pipelines.

[0006] The water leak detection system of the present invention comprises an optical fiber placed near a water pipeline, a vibration measuring device that outputs vibration data representing the time change in vibration applied to each point along the length of the optical fiber, and an analysis processing unit that analyzes the vibration data, and the analysis processing unit detects suspected leak points in the water pipeline by detecting vibrations specific to water leaks from the vibration data.

[0007] The analysis processing unit may calculate at least one of the amplitude intensity and frequency spectrum for each point in the optical fiber as an evaluation value, and detect suspected leak points by comparing the evaluation values ​​between adjacent points in the optical fiber.

[0008] The analysis processing unit may have healthy vibration data when the water pipeline is in a healthy state, and may detect suspected leak points by comparing the healthy vibration data with at least one of the amplitude intensity and frequency spectrum for each point obtained from the healthy vibration data.

[0009] The analysis processing unit may perform the comparison by calculating a correlation coefficient of a comparison target, and may use the correlation coefficient to detect a point where correlation deteriorates as a suspected water leak point.

[0010] The above disclosures can be combined as much as possible.

[0011] According to the present invention, it is possible to remotely detect a suspected water leak point in a water pipeline.

[0012] Fig. 1 is a configuration diagram showing a water leak detection system according to an embodiment of the present invention; Fig. 2 is a flowchart showing a first example of an analysis method; Fig. 3 is a flowchart showing a second example of an analysis method; Fig. 4 shows an example of a correlation coefficient for each point x in the length direction of an optical fiber cable; Fig. 5 shows an example of a correlation coefficient of a frequency spectrum at point x in the length direction of an optical fiber cable.

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0014] 1 is a block diagram showing a water leak detection system according to an embodiment of the present disclosure. The water leak detection system according to the embodiment of the present disclosure includes an optical fiber cable 91 arranged near a water pipeline 82 to be inspected for at least a certain distance, an optical fiber distributed vibration measuring device 11 that outputs vibration data representing the time change of vibration applied to each point along the length of the optical fiber cable 91, and an analysis processing unit 12 that analyzes the vibration data.

[0015] The vibration measuring device 11 is a device capable of measuring the time change of vibrations applied to each point along the length of the optical fiber cable 91, and can be, for example, a distributed acoustic sensing (DAS). Vibration measurement using a DAS allows vibration measurement at each point along the length of the optical fiber from one end of the optical fiber included in the optical fiber cable 91. In other words, because of its position-resolvable feature, the entire length of the optical fiber cable 91 does not need to be located near the water pipeline 82, as long as it is located along a certain distance. Therefore, the optical fiber cable 91 may be an optical fiber cable located in the water pipeline 82 exclusively for water leak detection, or it can be an underground optical fiber cable located for communication, for example, as long as it is located along the investigation section for a certain distance.

[0016] Vibration measurement using a DAS allows for positional resolution of vibrations along the length of the optical fiber cable 91, making it possible to set the area where vibrations caused by water leaks can be measured as the investigation section. The spatial resolution of the DAS allows for the investigation section to be set within a range of length that is equal to or less than the accuracy of identifying the suspected water leak point. The relationship between the distance information from the vibration measurement results and the position of the investigation section or investigation point can be identified by using the DAS to detect vibrations caused by known vibrations applied from the road, or by using the DAS to detect the location of a communication manhole close to the investigation point.

[0017] The surveyed section may be close or far away from one end of the optical fiber cable 91 (e.g., a communications station) where the DAS is installed, as long as vibrations caused by water leakage can be measured. In practice, attempting to measure all sections to be surveyed in a distributed manner using a single DAS would require a long, continuous optical fiber cable 91, which would be economically inefficient. Therefore, measurements are performed multiple times a day by periodically circulating the optical fiber from one end of the optical fiber cable 91 where the DAS is installed toward multiple routes while switching the optical fiber. In this case, if the elapsed time for one measurement is T seconds (T is sufficiently longer than the reciprocal of the lowest frequency of the vibration to be observed), then a total of TN seconds of vibration data for the same section can be obtained by circulating N times.

[0018] The analysis processing unit 12 analyzes the vibration data in the optical fiber length direction acquired by the vibration measuring instrument 11 and detects vibrations specific to water leaks from the vibration data, thereby detecting suspected water leak points in the water pipeline 82. The vibrations specific to water leaks can be detected by calculating the frequency spectrum for each point in the optical fiber cable 91 as an evaluation value. Figure 2 shows the first analysis method, and Figure 3 shows the second analysis method.

[0019] (First Analysis Method) In the first analysis method, the analysis processing unit 12 detects a suspected water leak point by comparing frequency spectra of adjacent investigation points on the optical fiber cable 91 .

[0020] Vibration data in the length direction of the optical fiber acquired by the vibration measuring device 11 is acquired (S11), the investigation section is identified from the time waveform of the vibration obtained from the vibration data (S12), and the vibration data of the investigation section is used to identify a point x included in the investigation section. ０ ~x ｚ Frequency spectrum f ０ ~f ｚ is analyzed (S13).

[0021] The analysis processing unit 12 ａ－１ Frequency spectrum at point x ａ Correlation coefficient y with the frequency spectrum at ａ－１・ａ This process is repeated for each point x (S14). FIG. 4 shows an example of the correlation coefficient for each point x.

[0022] The analysis processing unit 12 compares the correlation coefficients of adjacent points to check the increase or decrease in the correlation coefficient for each point (S15), and finds a point x that satisfies the following formula: ａ is detected as a suspected water leak point (S16). ａ－２・ａ－１ >y ａ－１・ａ Kats Y ａ・ａ＋１ <y ａ＋１・ａ＋２ (1)

[0023] In addition, in formula (1), the point where the correlation coefficient is the smallest is determined as the suspected leak point, but it is not limited to the smallest, and the point where the correlation deteriorates can also be determined as the suspected leak point. Furthermore, the comparison is not limited to adjacent points, and nearby points can also be compared.

[0024] (Second Analysis Method) In the second analysis method, healthy vibration data when the water pipeline is in a healthy state is stored in the analysis processing unit 12. In this case, the analysis processing unit 12 may detect a suspected water leak point by comparing the frequency spectrum obtained from the healthy vibration data with the frequency spectrum obtained from the healthy vibration data.

[0025] For example, when the analysis processing unit 12 acquires vibration data measured by the vibration measuring instrument 11 (S21), it identifies the investigation section from the time waveform of the vibration data (S22), extracts vibration data for the investigation section, and acquires healthy vibration data for the investigation section in a healthy state (S23).

[0026] The analysis processing unit 12 performs a correlation analysis between the vibration data of the survey target and the healthy vibration data measured by the vibration measuring device 11 for each point (S24). For example, the analysis processing unit 12 performs a correlation analysis between the vibration data of the survey target and the healthy vibration data of the survey target at point x included in the survey section. ０ ~x ｚ Frequency spectrum f ０ ~f ｚ Then, the analysis processing unit 12 calculates the location x of the survey target. Ｎ Vibration data frequency spectrum and point x Ｎ＋１ The correlation coefficient (where N is an integer between 0 and Z) obtained by analyzing the correlation of the vibration data frequency spectrum of point x in the healthy vibration data is Ｎ Vibration data frequency spectrum and point x Ｎ＋１ The correlation coefficient obtained by analyzing the correlation of the vibration data frequency spectrum is calculated for each point. This process is repeated for each point x. ａ An example of the correlation coefficient y in

[0027] The analysis processing unit 12 compares the correlation coefficient y of the vibration data under investigation with the correlation coefficient y of the healthy vibration data to examine the difference in correlation coefficient for each point (S25), and detects points with large differences in correlation coefficient as suspected leak points (S26).

[0028] In steps S14 and S24, the correlation coefficient between frequency spectra may be calculated by partially extracting a frequency band, or the correlation coefficient for each frequency may be calculated for the entire frequency spectrum and the sum of the correlation coefficients may be used as the correlation coefficient. Alternatively, the evaluation value in steps S14 and S24 is not limited to the frequency spectrum, and at least one of the amplitude intensity and the frequency spectrum may be used.

[0029] The water leak detection system of the present disclosure executes the above steps, making it possible to remotely detect vibrations characteristic of water leaks, thereby enabling the detection of suspected water leak points. The analysis processing unit 12 may output the suspected water leak points in the water pipeline 82. For example, the analysis processing unit 12 may reference a table that associates the distance of the optical fiber cable 91 with the position of the water pipeline 82, and output the geographical location of the suspected water leak point in the water pipeline 82. This makes it possible to automatically display the geographical location of the suspected water leak point in the water pipeline 82 on a map.

[0030] The frequency of vibrations caused by water leakage from the water pipeline 82 changes slightly over a period of years, but can be considered constant within a time frame of about one day. On the other hand, above ground where the water pipeline 82 is buried, there are many vibration phenomena, such as vehicle traffic and human activity, whose presence or absence of vibration changes over a period of less than one day, and these vibration phenomena become noise in the leak detection process using conventional technology.

[0031] In the present invention, it is noted that vibrations due to water leakage are constant over time, and the vibration measurement time is set to be sufficiently long compared to the time for which noise that changes over time increases or decreases. Also, since vibrations whose vibration generation position moves over time are not vibrations due to water leakage, vibration components whose vibration generation position moves over time are regarded as noise and removed in steps S11 and S21. Then, in steps S15 and S25, the correlation coefficient with the comparison object is derived, and the increase or decrease in the correlation coefficient is examined for each point, and the point x where the correlation deteriorates is determined. ａ is detected as a suspected leak point.

[0032] The optical fiber cable 91 laid for communication purposes is connected to a vibration measuring device 11 installed in a communication building. It is also desirable that the optical fiber cable 91 be laid in a communication conduit 81 that is laid as close as possible to the water pipe 82 that is the object of leak detection and that runs parallel to the water pipe 82.

[0033] Furthermore, the optical fiber is usually housed in an optical fiber cable 91 laid in an underground communication conduit 81. The communication conduit 81 is generally made of polyvinyl chloride or metal, and if the distance from the water conduit 82 is about the same, a polyvinyl chloride communication conduit 81 is selected. Also, a flexible pipe (inner pipe) is laid within the communication conduit 81 to lay multiple optical fiber cables 91 in the same conduit, and the optical fiber cable 91 may be housed in the flexible pipe, but since this makes it difficult to obtain water leakage vibrations, an optical fiber cable 91 laid directly in the conduit is selected.

[0034] As described above, the water leak detection system of the present invention comprises an optical fiber arranged so that vibrations are applied at multiple points on a water distribution pipe, an optical fiber vibration measuring instrument that measures the vibrations applied to each point along the length of the optical fiber, and an analysis processing unit 12 that analyzes the measurement results of the vibration measuring instrument 11.The analysis processing unit 12 calculates a correlation coefficient between adjacent investigation points for the vibration intensity or frequency spectrum obtained at each point along the length of the optical fiber from the measurement results, and uses the correlation coefficient to detect points where the correlation has deteriorated as suspected water leak points.

[0035] The analysis processing unit 12 of the present invention can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network.

[0036] 11: Vibration measuring device 12: Analysis processing unit 81: Communication pipe 82: Water pipe 91: Optical fiber cable

Claims

1. A water leak detection system comprising: an optical fiber placed near a water pipeline; a vibration measuring device that outputs vibration data that represents the change over time in vibration applied to each point along the length of the optical fiber; and an analysis processing unit that analyzes the vibration data, wherein the analysis processing unit detects vibrations specific to water leaks from the vibration data, thereby detecting suspected leak points in the water pipeline.

2. The water leak detection system according to claim 1, wherein the analysis processing unit calculates at least one of the amplitude intensity and the frequency spectrum for each point in the optical fiber as an evaluation value, and detects suspected water leak points by comparing the evaluation values ​​between adjacent points in the optical fiber.

3. The leak detection system of claim 1, wherein the analysis processing unit has healthy vibration data when the water pipeline is in a healthy state, and detects suspected leak points by comparing at least one of the amplitude intensity and frequency spectrum for each point obtained from the healthy vibration data.

4. The water leakage detection system according to claim 2 or 3, wherein the analysis processing unit performs the comparison by calculating a correlation coefficient of the objects to be compared, and detects points where correlation deteriorates using the correlation coefficient as suspected water leakage points.

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