Water supply pipeline temperature leakage detection method based on distributed optical fibers

Abstract

The invention discloses a distributed optical fiber-based water supply pipeline temperature leakage detection method, which comprises the following steps: S1, deploying a distributed optical fiber sensing system by adopting a DTS system, and laying temperature sensing optical fibers along a water supply pipeline; s2, temperature signal acquisition: continuously acquiring temperature signals around the pipeline through the temperature sensing optical fibers laid in the step S1; s3, processing the temperature signal acquired in the step S2; after denoising processing is conducted on the collected temperature signals, the temperature space gradient in the optical fiber direction is calculated, and a suspected leakage area is determined by recognizing sudden changes of the temperature space gradient; and S4, positioning a temperature abnormal point of the suspected leakage area based on an optical time domain reflection principle, and judging a leakage type by combining a temperature gradient size and a temperature abnormal area range so as to realize accurate positioning of the leakage point. The water supply pipeline leakage detection method based on the distributed optical fiber temperature signals has the advantages of being high in detection precision, high in anti-interference capacity, resistant to corrosion and flexible in arrangement.

Description

Technical Field

[0001] This invention relates to the field of water supply network detection technology, and in particular to a method for detecting leaks in water supply pipelines based on distributed optical fiber temperature. Background Technology

[0002] As a critical component of urban and industrial infrastructure, leaks in water supply networks not only waste significant amounts of water resources but can also lead to reduced water pressure, disrupting normal water supply and even causing safety incidents such as ground subsidence and road collapses. Traditional leak detection methods, such as manual inspections and leak detectors, suffer from poor real-time performance, low detection efficiency, and susceptibility to environmental interference, making them unsuitable for monitoring large-scale water supply networks.

[0003] However, existing pipe leak detection methods based on temperature signals lack sufficient precision in processing temperature signals and fail to fully explore the intrinsic correlation between temperature field changes and leaks, resulting in room for improvement in detection accuracy and reliability. This invention provides a temperature-based leak detection method for water supply pipelines based on distributed optical fibers to address the problems existing in the background technology. Summary of the Invention

[0004] In view of this, the present invention proposes a method for detecting leaks in water supply pipelines based on distributed optical fiber. It is applicable to real-time leak monitoring of water supply pipelines in various scenarios such as buried pipelines and pipe corridors. It can be widely used in the safety detection of urban water supply networks and industrial plant water supply pipelines, so as to solve the problems of poor real-time performance, low detection efficiency and great susceptibility to environmental interference in existing technologies.

[0005] The technical solution of this invention is implemented as follows: This invention provides a method for detecting leaks in water supply pipelines based on distributed optical fiber, comprising the following steps: S1. A distributed optical fiber sensing system is deployed using a DTS system, which uses temperature-sensing optical fibers laid along the water supply pipeline. S2. Temperature signal acquisition: The temperature signal around the pipeline is continuously acquired through the temperature-sensing optical fiber laid in step S1. S3. Process the temperature signal collected in step S2; after denoising the collected temperature signal, calculate the temperature spatial gradient along the fiber direction, and identify the suspected leakage area by identifying abrupt changes in the temperature spatial gradient. S4. Based on the principle of optical time-domain reflectometry, the temperature anomaly point in the suspected leak area is located. The leak type is determined by combining the magnitude of the temperature gradient and the range of the temperature anomaly area, so as to achieve accurate location of the leak point.

[0006] Further solution: In step S1, the DTS system comprises a pulsed laser, a wavelength division multiplexer (WDM), a temperature-sensing fiber, a photodetector, and a high-speed data acquisition card. The pulsed laser emits a 1550nm pulsed light signal; the WDM transmits the emitted pulsed light signal to the temperature-sensing fiber and separates the backscattered Raman light generated in the fiber; the temperature-sensing fiber is laid along the water supply pipeline, serving as a temperature sensing carrier to directly detect temperature changes around the pipeline; the photodetector converts the separated Raman scattered light signal into an electrical signal; and the high-speed data acquisition card acquires the electrical signal and transmits the acquired data to a terminal computer for processing and analysis.

[0007] Further scheme: Temperature signal acquisition in step S2: When the light pulse emitted by the pulsed laser propagates in the temperature-sensing optical fiber, photons interact with the fiber molecules, producing Raman scattering, including Stokes scattering and anti-Stokes scattering; the intensity of anti-Stokes scattering light is significantly affected by temperature, while the intensity of Stokes scattering light is less affected by temperature, and the intensity ratio of the two satisfies the following relationship: ; Where I(T) is the intensity ratio of the anti-Stokes beam to the Stokes beam; Φ AS It is the luminous flux of the anti-Stokes scattered light; Φ S It is the luminous flux of Stokes scattered light; v AS It is the frequency of the anti-Stokes scattered light; v s It is the frequency of Stokes scattered light; e is the natural constant; It is Planck's constant; The frequency of the Raman phonon; is Boltzmann's constant; T is the thermodynamic temperature; the temperature information of each segment of the optical fiber can be obtained from the intensity ratio of the two.

[0008] Further solutions: The temperature signal processing in step S3 includes the following methods: 1) Denoising: The original temperature data is smoothed by using a repeated averaging denoising algorithm. Specifically, the average value of temperature data collected multiple times at the same location is taken to reduce the interference of random noise on the temperature signal, making the temperature curve smoother and facilitating subsequent temperature gradient calculation; 2) Temperature gradient type judgment calculation and suspected area identification: The ratio of the temperature difference to the distance between adjacent sampling points along the fiber direction is calculated, i.e., the temperature gradient ΔT / ΔL. When the temperature gradient ΔT ≥ 1.0℃ / m, the area is marked as a suspected leak area; to avoid misjudgment, when the temperature gradient ΔT of 3 or more consecutive sampling points is ≥ 1.0℃ / m, the area is confirmed as a suspected leak area; 3) Location calculation: The temperature anomaly point in the suspected leak area is located by the principle of optical time domain reflection (OTDR); when the optical signal is transmitted in the optical fiber, it is scattered after reaching a certain position and returns to the data acquisition module. According to the round-trip time t of the optical signal, combined with the propagation speed v of the light in the optical fiber; v=c / n, where c is the propagation speed of light in vacuum and n is the refractive index of the fiber core, the position L of the scattering point is calculated. The calculation formula is L=vt / 2, thereby determining the position of the temperature anomaly point, that is, the position of the suspected leak point.

[0009] Further solution: Temperature anomaly point location. Location logic: The location of the point with the largest temperature gradient in the suspected leak area is taken as the center location of the leak point. The location error range is determined by combining the spatial resolution (1m) of the DTS system. The error of the final location result is ≤1m.

[0010] Further solutions: Temperature gradient type calculation and suspected area identification: 1) Minor leak: Temperature gradient is 1-3℃ / m, the temperature anomaly area is small (≤2m), and the temperature change is relatively gentle. This is mainly due to the small amount of leakage, which has a limited impact on the surrounding temperature field; 2) Moderate leak: Temperature gradient is 3-5℃ / m, the temperature anomaly area is moderate (2-5m), the temperature change is more obvious, the leakage amount is moderate, and the impact on the surrounding temperature field is larger than that of a minor leak; 3) Severe leak: Temperature gradient >5℃ / m, the temperature anomaly area is large (>5m), the temperature change is drastic, the leakage amount is large, and the impact on the surrounding temperature field is significant.

[0011] The water supply pipeline temperature detection and leakage method based on distributed optical fiber of the present invention has the following advantages over the prior art: 1. High detection accuracy: Through optimized temperature signal processing algorithms, based on the characteristics of temperature gradient abrupt changes and the principle of optical time-domain reflectometry, the location is achieved with an error of ≤1m, and leaks with a diameter of ≥2mm can be identified; This invention further improves the efficiency of water supply pipeline leak detection based on a single temperature signal by optimizing the temperature signal acquisition, processing and analysis process. 2. Simple system structure: Detection can be completed solely by the DTS system, without the need for other sensing systems, thus reducing system complexity and cost; 3. It has the advantages of strong anti-interference ability, corrosion resistance and flexible deployment. Through repeated averaging denoising algorithm and continuous multi-point temperature gradient judgment, it effectively eliminates interference factors such as slow fluctuation of ambient temperature and local heat sources. 4. Strong real-time performance: Signal acquisition and processing delay <10s, enabling rapid response to leakage events, facilitating timely repair measures, and reducing losses; 5. The optical signal of the pulsed laser wavelength experiences less attenuation when transmitted in optical fiber, making it suitable for long-distance monitoring. Attached Figure Description

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0013] Figure 1 This is a flowchart of the water supply pipeline temperature detection and leakage method based on distributed optical fiber according to the present invention. Detailed Implementation

[0014] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example 1:

[0015] This invention provides a method for detecting leaks in water supply pipelines based on distributed optical fiber, comprising the following steps: S1, deploying a distributed optical fiber sensing system using a DTS system, and using temperature-sensing optical fibers laid along the water supply pipeline. S2. Temperature signal acquisition: The temperature signal around the pipeline is continuously acquired through the temperature-sensing optical fiber laid in step S1. S3. Process the temperature signal collected in step S2; after denoising the collected temperature signal, calculate the temperature spatial gradient along the fiber direction, and identify the suspected leakage area by identifying abrupt changes in the temperature spatial gradient. S4. Based on the principle of optical time-domain reflectometry, the temperature anomaly point in the suspected leak area is located. The leak type is determined by combining the magnitude of the temperature gradient and the range of the temperature anomaly area, so as to achieve accurate location of the leak point.

[0016] The DTS system comprises a pulsed laser, a wavelength division multiplexer (WDM), a temperature-sensing fiber optic cable, a photodetector, and a high-speed data acquisition card. The pulsed laser emits a 1550nm pulsed light signal. The WDM transmits the emitted pulsed light signal to the temperature-sensing fiber optic cable and separates the backscattered Raman light generated within the cable. The temperature-sensing fiber optic cable is laid along the water supply pipeline, serving as the temperature sensing carrier to directly detect temperature changes around the pipeline. The photodetector converts the separated Raman scattered light signal into an electrical signal. The high-speed data acquisition card acquires the electrical signal and transmits the acquired data to a terminal computer for processing and analysis. The temperature-sensing fiber optic cable is laid parallel to the water supply pipeline, with a distance of 5-10cm between the fiber optic cable and the outer wall of the pipeline. The burial depth of the fiber optic cable matches the burial depth of the pipeline, ensuring accurate detection of temperature changes around the pipeline. The DTS system parameters are set as follows: sampling rate of 1kHz, spatial resolution of 1m, and pulse period of 10μs emitted by the pulsed laser, ensuring precise capture of the spatial distribution and temporal changes in temperature.

[0017] Temperature signal acquisition is based on Raman scattering: a pulsed laser emits light pulses at a set period (10μs), and temperature distribution data is collected every 10s across the entire fiber. The backscattered Raman light is separated by a wavelength division multiplexer, converted into an electrical signal by a photodetector, acquired by a high-speed data acquisition card, and transmitted to a computer for processing. When the light pulses emitted by the pulsed laser propagate through the temperature-sensitive fiber, photons interact with fiber molecules, producing Raman scattering phenomena, including Stokes scattering (photons release energy, and the scattered light frequency is lower than the incident light frequency) and anti-Stokes scattering (photons absorb energy, and the scattered light frequency is higher than the incident light frequency). The intensity of anti-Stokes scattering is significantly affected by temperature, while the intensity of Stokes scattering is less affected by temperature. The intensity ratio of the two satisfies the following relationship: ; Where I(T) is the intensity ratio of the anti-Stokes beam to the Stokes beam; Φ AS It is the luminous flux of the anti-Stokes scattered light; Φ S It is the luminous flux of Stokes scattered light; v AS It is the frequency of the anti-Stokes scattered light; v s It is the frequency of Stokes scattered light; e is the natural constant; It is Planck's constant; The frequency of the Raman phonon; is Boltzmann's constant; T is the thermodynamic temperature; the temperature information of each segment of the optical fiber can be obtained from the intensity ratio of the two.

[0018] Temperature signal processing; 1) Denoising: The original temperature data is smoothed by using a repeated averaging denoising algorithm. Specifically, the average value of temperature data collected multiple times at the same location is taken to reduce the interference of random noise on the temperature signal, making the temperature curve smoother and facilitating subsequent temperature gradient calculation; 2) Temperature gradient type judgment calculation and suspected area identification: The ratio of the temperature difference to the distance between adjacent sampling points along the fiber direction is calculated, i.e., temperature gradient ΔT / ΔL. When the temperature gradient ΔT ≥ 1.0℃ / m, the area is marked as a suspected leak area. To avoid misjudgment, the data processing software in the computer first uses a repeated averaging denoising algorithm to denoise the original temperature data. The average value of the data collected 10 times consecutively at each sampling point is taken. Then, the temperature gradient of adjacent sampling points along the fiber direction is calculated. When the temperature gradient ΔT of 3 or more consecutive sampling points is ≥ 1.0℃ / m, the area is confirmed as a suspected leak area. 3) Location calculation: The temperature anomaly point in the suspected leak area is located by the principle of optical time domain reflection (OTDR). When the optical signal is transmitted in the optical fiber, it is scattered after reaching a certain position and returns to the data acquisition module. Based on the round-trip time t of the optical signal, combined with the propagation speed v of the optical fiber, v = c / n, where c is the propagation speed of light in a vacuum and n is the refractive index of the fiber core, the position L of the scattering point is calculated. The calculation formula is L = vt / 2, thereby determining the position of the temperature anomaly point, that is, the position of the suspected leak point.

[0019] Temperature anomaly point location, location logic: take the location of the point with the largest temperature gradient in the suspected leak area as the center location of the leak point, and combine it with the spatial resolution (1m) of the DTS system to determine the location error range. The error of the final location result is ≤1m; within the suspected leak area.

[0020] Temperature gradient type determination: Based on the magnitude of the temperature gradient and the extent of the temperature anomaly area, and referring to the classification criteria (minor leak, moderate leak, and severe leak), determine the type of leak. 1) Minor leak: Temperature gradient is 1-3℃ / m, the temperature anomaly area is small (≤2m), and the temperature change is relatively gradual. This is mainly due to the small leak volume, resulting in a limited impact on the surrounding temperature field. 2) Moderate leak: Temperature gradient is 3-5℃ / m, the temperature anomaly area is moderate (2-5m), the temperature change is more significant, the leak volume is moderate, and the impact on the surrounding temperature field is larger than that of a minor leak. 3) Severe leak: Temperature gradient >5℃ / m, the temperature anomaly area is large (>5m), the temperature change is drastic, the leak volume is large, and the impact on the surrounding temperature field is significant.

[0021] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting leaks in water supply pipelines based on distributed optical fiber temperature signals, characterized in that: Includes the following steps: S1. A distributed optical fiber sensing system is deployed using a DTS system, which uses temperature-sensing optical fibers laid along the water supply pipeline. S2. Temperature signal acquisition: The temperature signal around the pipeline is continuously acquired through the temperature-sensing optical fiber laid in step S1. S3. Process the temperature signal collected in step S2; after denoising the collected temperature signal, calculate the temperature spatial gradient along the fiber direction, and identify the suspected leakage area by identifying abrupt changes in the temperature spatial gradient. S4. Based on the principle of optical time-domain reflectometry, the temperature anomaly point in the suspected leak area is located. The leak type is determined by combining the magnitude of the temperature gradient and the range of the temperature anomaly area, so as to achieve accurate location of the leak point.

2. The water supply pipeline leakage detection method based on distributed optical fiber temperature signal according to claim 1, characterized in that: In step S1, the DTS system comprises a pulsed laser, a wavelength division multiplexer, a temperature-sensing fiber, a photodetector, and a high-speed data acquisition card. The pulsed laser emits a 1550nm pulsed light signal. The wavelength division multiplexer transmits the emitted pulsed light signal to the temperature-sensing fiber and separates the backscattered Raman light generated in the fiber. The temperature-sensing fiber is laid along the water supply pipeline, serving as a temperature sensing carrier to directly sense temperature changes around the pipeline. The photodetector converts the separated Raman scattered light signal into an electrical signal. The high-speed data acquisition card acquires the electrical signal and transmits the acquired data to a terminal computer for processing and analysis.

3. The water supply pipeline leakage detection method based on distributed optical fiber temperature signal according to claim 1, characterized in that: In step S2, temperature signals are acquired. When the light pulse emitted by the pulsed laser propagates in the temperature-sensitive optical fiber, photons interact with the fiber molecules, producing Raman scattering phenomena, including Stokes scattering and anti-Stokes scattering. The intensity of anti-Stokes scattering light is significantly affected by temperature, while the intensity of Stokes scattering light is less affected by temperature. The intensity ratio of the two satisfies the following relationship: ； Where I(T) is the intensity ratio of the anti-Stokes beam to the Stokes beam; Φ AS It is the luminous flux of the anti-Stokes scattered light; Φ S It is the luminous flux of Stokes scattered light; v AS It is the frequency of the anti-Stokes scattered light; v s It is the frequency of Stokes scattered light; e is the natural constant; It is Planck's constant; The frequency of the Raman phonon; is Boltzmann's constant; T is the thermodynamic temperature; the temperature information of each segment of the optical fiber can be obtained from the intensity ratio of the two.

4. The water supply pipeline leakage detection method based on distributed optical fiber temperature signal according to claim 1, characterized in that: The temperature signal processing in step S3 includes the following methods: S11: Denoising: The original temperature data is smoothed by using a repeated averaging denoising algorithm. Specifically, the average value of temperature data collected multiple times at the same location is taken to reduce the interference of random noise on the temperature signal, making the temperature curve smoother and facilitating subsequent temperature gradient calculation. S12: Temperature gradient type judgment and suspected area identification: Calculate the ratio of temperature difference to distance between adjacent sampling points along the fiber direction, i.e., temperature gradient ΔT / ΔL; when the temperature gradient ΔT ≥ 1.0℃ / m, mark the area as a suspected leak area; to avoid false judgment, when the temperature gradient ΔT of 3 or more consecutive sampling points is ≥ 1.0℃ / m, the area is confirmed as a suspected leak area; S13: Location Calculation: The temperature anomaly point in the suspected leak area is located using the principle of optical time-domain reflectometry. When the optical signal is transmitted in the optical fiber, it is scattered after reaching a certain position and returns to the data acquisition module. Based on the round-trip time t of the optical signal, combined with the propagation speed v of light in the optical fiber; v=c / n, where c is the propagation speed of light in a vacuum and n is the refractive index of the fiber core, the position L of the scattering point is calculated. The calculation formula is L=vt / 2, thereby determining the location of the temperature anomaly point, i.e., the location of the suspected leak point.

5. A method for detecting leaks in water supply pipelines based on distributed optical fiber temperature signals according to claim 4, characterized in that: In step S13, the abnormal temperature point is located using the following logic: the location of the point with the maximum temperature gradient in the suspected leak area is taken as the center location of the leak point, and the location error range is determined by combining the spatial resolution of the DTS system. The error of the final location result is ≤1m.

6. A method for detecting leaks in water supply pipelines based on distributed optical fiber temperature signals according to claim 4, characterized in that: Temperature gradient type and suspected area identification: 1) Minor leakage: The temperature gradient is 1-3℃ / m, the temperature anomaly area is small, the temperature change is relatively gentle, and due to the small leakage amount, the impact on the surrounding temperature field is limited. 2) Moderate leakage: The temperature gradient is 3-5℃ / m, the temperature anomaly area is moderate, the temperature change is relatively obvious, the leakage amount is moderate, and the impact on the surrounding temperature field is larger than that of minor leakage. 3) Severe leakage: Temperature gradient > 5℃ / m, large area of ​​temperature anomaly, drastic temperature changes, large leakage volume, and significant impact on the surrounding temperature field.

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