A method and system for detecting a gas pipeline leak

Abstract

The application discloses a kind of natural gas pipeline gas leakage detection method and system, the detection method includes the following steps: S1: build optical path measurement architecture on pipeline, whether there is gas leakage phenomenon in pipeline by optical path measurement architecture real-time monitoring→S2: when gas leakage, detection end is positioned to the gas leakage point of pipeline and positioning information is sent to processing end by moving on pipeline→S3: when no gas leakage, detection end is periodically moved on pipeline, detects the defect of inside and outside surface of pipeline, when pipeline exists defect, defect information is sent to processing end and early warning is carried out.The application detects pipeline by real-time monitoring whether there is gas leakage phenomenon, when monitoring gas leakage point, secondary detection is carried out to pipeline, avoids misjudgment while positioning, improves the monitoring accuracy of pipeline, when pipeline does not leak, whether defect exists in pipeline is detected periodically, and early warning is generated by defect, so that maintenance personnel can repair natural gas pipeline in advance, detection effect is good, guarantee the safe use of natural gas pipeline.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pipeline detection, and in particular to a natural gas pipeline leakage detection method and system. BACKGROUND

[0002] To meet the requirements of low-carbon development of national economy and society industry, the natural gas industry has developed rapidly, and the construction, operation, maintenance and protection of natural gas pipelines have gradually become the top priority in the field of energy construction. During the process of natural gas exploration, processing and gathering and transportation, when certain low temperature and high pressure conditions are met, natural gas hydrates will form and condense in the natural gas pipeline. Light interference with normal production may cause a decrease in the transportation capacity of the natural gas pipeline, and heavy interference may cause the shutdown of equipment such as wellbore, pipeline and valve, and even cause the rupture of the gas pipeline, causing safety accidents and resulting in serious economic, social and personnel losses. In addition, leakage events caused by corrosion or external intrusion may also cause serious economic losses and safety accidents.

[0003] A natural gas pipeline leakage detection method is disclosed in the technical field of pipeline detection in Chinese patent application No. 202110276874.X, which comprises the following steps: deploying a infrasound sensor to a natural gas pipeline, collecting infrasound waves in the natural gas pipeline by using the infrasound sensor, performing noise reduction processing on the infrasound wave signal by using an infrasound wave noise reduction algorithm, extracting infrasound wave waveform feature data collected by each sensor by using Fourier transform, using the infrasound wave waveform feature data as a training set to train a support vector machine, using the trained support vector machine to judge the leakage of the sensors on the pipeline to be monitored to obtain a basic probability distribution function on the output set, and comprehensively processing the basic probability distribution function of each sensor based on DS evidence theory. If P(leakage)>P(no leakage), it indicates that the current pipeline has leaked, otherwise the current pipeline has not leaked. The present application also provides a natural gas pipeline leakage detection system. The present application realizes the leakage detection of the natural gas pipeline.

[0004] The above-mentioned technology has the following disadvantages: the natural gas pipeline leakage detection system mainly performs online leakage monitoring on the pipeline, however, when the system detects a leakage point, it does not have positioning and secondary detection processing for the leakage point, which is not convenient for manual rapid searching of the leakage point, and there is a false detection phenomenon, and the system does not have defect detection and early warning processing for the pipeline, which cannot guarantee the safe use of the natural gas pipeline. SUMMARY

[0005] The purpose of the present application is to provide a natural gas pipeline leakage detection method and system to solve the problems in the background art.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical solution: a natural gas pipeline leakage detection method, the detection method comprising the following steps:

[0007] S1: build an optical path measurement architecture on the pipeline, and monitor whether the pipeline leaks in real time through the optical path measurement architecture, wherein the optical path measurement architecture comprises an ASE light source, an optical circulator, a photodetector, a Faraday rotator, a polarization controller, a phase modulator, a 2x2 optical coupler, a 1x2 optical coupler, a delay optical fiber, and a sensing optical fiber;

[0008] S2: when leaking, according to the leakage phenomenon monitored by the optical path measurement architecture, drive the detection end to move and position to the leakage point of the pipeline, and send the positioning information to the processing end;

[0009] S3: when not leaking, the detection end moves periodically on the pipeline to detect the defects on the inner and outer surfaces of the pipeline, and when the pipeline has defects, sends the defect information to the processing end for early warning.

[0010] In a preferred embodiment, the optical path measurement architecture comprises an ASE light source, an optical circulator, a photodetector, a Faraday rotator, a polarization controller, a phase modulator, a 2x2 optical coupler, a 1x2 optical coupler, a delay optical fiber, and a sensing optical fiber.

[0011] In a preferred embodiment, in step S1, the optical path measurement architecture operates and comprises the following steps:

[0012] S1.1: the light emitted by the ASE light source enters the No. 1 port of the optical circulator;

[0013] S1.2: and then output from the No. 3 port of the optical circulator, and enter the 2x2 optical coupler 1;

[0014] S1.3: the optical signal that passes through the optical coupler 1 is divided into two optical signals with a coupling ratio of 50:50;

[0015] S1.4: the two optical signals propagate along four optical paths respectively.

[0016] In a preferred embodiment, the optical signal propagates along the path, first passes through the phase modulator, and then passes through the leakage point. The optical signal passes through the leakage point twice and is modulated twice, and the expression is:

[0017]

[0018] In the formula, E1 is the amplitude of the light, is the leakage point signal, is the leakage point modulation amplitude, ω s is the leakage point modulation frequency, ω c is the optical wave angular frequency, τ1 and τ2 are the first and second times of the light passing through the leakage point along path one, is the modulation signal amplitude, ωm is the modulation signal frequency; τ m1 is the time for path one light to reach the phase modulator; δ1 is the phase of path one light.

[0019] In a preferred embodiment, when the optical signal propagates along path two, it is modulated twice by the leakage point and modulated by the phase modulator, and the expression after modulation is:

[0020]

[0021] wherein E2 is the amplitude of light, is the leakage point signal, is the leakage point modulation amplitude, ω s is the leakage point modulation frequency, ω c is the optical wave angular frequency, τ3 and τ4 are respectively the time for the first and second time of path two light passing through the leakage point, is the modulation signal amplitude, ω m is the modulation signal frequency, τ m2 are respectively the time for path two light to reach the phase modulator, δ2 is respectively the phase of path two light.

[0022] In a preferred embodiment, when the natural gas pipeline leaks, the detection end moves on the pipeline and is positioned to the leakage point of the pipeline, and when the natural gas pipeline does not leak, the detection end moves on the pipeline periodically to detect the defects on the inner and outer surfaces of the pipeline, and specifically comprises the following steps:

[0023] (1) magnetize the natural gas pipeline;

[0024] (2) the magnetic induction lines of the pipeline at the defect are hindered by the pipeline defect, and the magnetic induction lines at the defect are distorted;

[0025] (3) part of the magnetic induction lines passes out from the inner and outer surfaces of the pipeline to form a leakage magnetic field;

[0026] (4) detect the leakage magnetic field leaked out by the magnetic sensitive element to judge the size and shape of the defect.

[0027] In a preferred embodiment, the leakage magnetic field is analyzed by a point magnetic dipole model, comprising the following steps:

[0028] (1) the point magnetic dipole model solves the leakage magnetic field of hole, pit and point pipeline defects;

[0029] (2) let m be a point charge in space, P(x, y) be any point in space, and the magnetic field generated by m at P point has a size of:

[0030]

[0031] Wherein, r is the distance from point P(x, y) to point magnetic charge m.

[0032] In a preferred embodiment, the calculation formula between the magnetic induction intensity B and the magnetic field intensity H after the pipeline is added with the magnetic field is:

[0033] B = μ * H

[0034] Wherein, μ is the magnetic permeability of the material, and μ changes with the change of the magnetic field intensity H.

[0035] The application also provides a natural gas pipeline leakage detection system, which is used to realize a natural gas pipeline leakage detection method, and comprises a monitoring module, a detection module and a control module.

[0036] When the monitoring module detects a leakage point, the driving module drives the detection module to move for secondary detection of the leakage point, and the positioning module is used to position the leakage point and send a leakage signal; when there is no leakage point, the driving module regularly drives the detection module to move to detect the natural gas pipeline, and when a defect exists in the natural gas pipeline, an early warning signal is sent; the control module receives the leakage signal and the early warning signal and sends them to a remote computer through the Internet of Things.

[0037] In a preferred embodiment, the driving module comprises guide wheels and supports clamped on both sides of the pipeline, the guide wheels are driven to run by a motor, and the positioning module is a GPS positioning chip which is used to position the position of the detection module.

[0038] In the above technical solution, the application has the following technical effects and advantages:

[0039] 1. The application can monitor whether the pipeline leaks in real time, and when a leakage point is detected, the pipeline is subjected to secondary detection, the positioning is performed while avoiding false detection, the monitoring accuracy of the pipeline is improved, when the pipeline does not leak, the pipeline is regularly detected for defects, and the defects generate early warnings, so that the maintenance personnel can repair the natural gas pipeline in advance, the detection effect is good, and the safe use of the natural gas pipeline is ensured.

[0040] 2. The application improves the optical path architecture, the improved optical path measurement architecture has simple structure and convenient optical fiber laying, the sensing signal loss is reduced, the sensing ability for weak sensing signals is enhanced, and the overall performance of the optical path measurement architecture is improved.

[0041] 3. The application judges the defects according to the detected magnetic leakage signals, when the natural gas pipeline leaks, a defect exists at the leakage position, the detection end is positioned at the defect position after detecting the defect, and positioning information is sent after confirming the leakage, and when the pipeline has defects that may cause leakage, early warning is performed in time during the regular detection. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only represent some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art based on these drawings.

[0043] Figure 1 The working flow chart of the detection method of the present application.

[0044] Figure 2 The system module diagram of the present application.

[0045] Figure 3 The optical path measurement architecture diagram of the present application.

[0046] Figure 4 The path diagram of light propagation in the present application.

[0047] Figure 5 The magnetic induction line distribution diagram for detecting defects in the pipeline in the present application.

[0048] Figure 6 The magnetization intensity selection curve diagram in the present application. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be described clearly and completely in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, not all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0050] It should be noted that when an element is referred to as being "fixed" to another element, it can be directly on the other element or there can be an intervening element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements can be present.

[0051] Embodiment 1

[0052] Please refer to Figure 1 The detection method of the natural gas pipeline leakage detection method described in the present embodiment includes the following steps:

[0053] The light path measurement architecture is built on the pipeline, the light path measurement architecture is used to monitor whether the pipeline leaks in real time, when the pipeline leaks, the detection end moves on the pipeline and is positioned to the leakage point of the pipeline, and the positioning information is sent to the processing end, when the pipeline does not leak, the detection end moves on the pipeline regularly to detect the defects on the inner and outer surfaces of the pipeline, when the pipeline has defects, the defect information is sent to the processing end for early warning, the detection method can monitor whether the pipeline leaks in real time, when the leakage point is monitored, the pipeline is detected again, the positioning is realized while the false detection is avoided, the monitoring accuracy of the pipeline is improved, when the pipeline does not leak, whether the pipeline has defects is detected regularly, and the early warning is generated through the defects, so that the maintenance personnel can repair the natural gas pipeline in advance, the detection effect is good, and the safe use of the natural gas pipeline is ensured.

[0054] In the embodiment, the light path measurement architecture is built on the pipeline, the light path measurement architecture is used to monitor whether the pipeline leaks in real time, the light path measurement architecture combines the zero optical path difference of the Mach-Zehnder architecture and the Sagnac architecture, the low requirement for the coherent length of the light source, and the advantages of the mixed interferometer, and the disadvantages of the single interferometer are avoided.

[0055] Please refer to Figure 3 As shown in the figure, the light path measurement architecture mainly comprises an ASE light source, an optical circulator, an optical detector, a Faraday rotating mirror, a polarization controller, a phase modulator, a 2*2 optical coupler, a 1*2 optical coupler, a delay optical fiber and a sensing optical fiber.

[0056] Among them,

[0057] (1) The ASE light source is adopted, on the one hand, because it has sufficient output optical power, which can meet the requirement of the detection system on the optical power output of the long natural gas pipeline leakage detection; on the other hand, the ASE light source has a wide spectrum, which can reduce the coherent backscattering noise of the system, the phase noise caused by the fiber Rayleigh scattering and the phase zero drift caused by the optical Kerr effect, and the signal-to-noise ratio of the detection system is improved as a whole.

[0058] (2) The optical circulator is added between the light source and the optical coupler 1, mainly to avoid the light emitted by the light source returning to the light source through the Faraday rotating mirror, thereby causing damage to the light source; in addition, the addition of the optical circulator can reduce the additional loss of the optical signal of the light path architecture.

[0059] (3) In order to reduce the polarization state fading phenomenon of the whole optical path, the polarization controller is added on the side of the phase modulator between the two couplers, the polarization state angle of the two lights in the interferometer is made as small as possible by adjusting the polarization controller, the display of the zero frequency is clearer, the identification is better, and the positioning effect is also better.

[0060] (4) The optical coupler 2 in the measurement architecture uses a 1x2 optical coupler instead of a 2x2 optical coupler, reducing the additional loss of the sensing signal, and also simplifying the structure of the detection system.

[0061] Referring to Figure 4 As shown in the figure, the optical path measurement architecture operation includes the following steps:

[0062] (1) The light emitted by the ASE light source enters the No. 1 port of the optical circulator;

[0063] (2) Then output from the No. 3 port of the optical circulator, into the 2x2 optical coupler 1;

[0064] (3) The optical signal that comes out of the optical coupler 1 is divided into two optical signals with a coupling ratio of 50:50;

[0065] (4) The two optical signals propagate along four optical paths respectively.

[0066] According to the Sagnac interference principle, only the two optical signals propagating along path one and path two satisfy the zero optical path difference condition of the Sagnac interferometer, so only these two optical signals interfere in the optical path measurement architecture, and the optical signal generated by interference is used as the detection signal of the leakage point.

[0067] Assuming that the leakage point signal is represented as is the modulation amplitude of the leakage point, ω s is the modulation frequency of the leakage point, the light propagating along path one first passes through the phase modulator, then passes through the leakage point, and due to the action of the Faraday rotating mirror, the light passes through the leakage point twice and is modulated twice, and its expression is:

[0068]

[0069] When the optical signal propagates along path two, it is modulated twice by the leakage point first, and then modulated by the phase modulator, and the expression after modulation is:

[0070]

[0071] where E1 and E2 are the amplitudes of the light; ω c is the optical angular frequency; τ1 and τ2 are the first and second times of the light in path one passing through the leakage point, respectively, and τ3 and τ4 are the first and second times of the light in path two passing through the leakage point, respectively; is the modulation signal amplitude, ω m is the modulation signal frequency; τ m1 , τ m2The time of the path one and two light reaching the phase modulator respectively; δ1, δ2 are the phase of the path one and two light respectively, so that the leakage point position can be calculated.

[0072] The improved optical path measurement architecture has simple structure, convenient fiber laying, reduced sensing signal loss, enhanced sensing ability for weak sensing signals, and improved overall performance of the optical path measurement architecture.

[0073] Embodiment 2

[0074] In the above embodiment 1, when the natural gas pipeline leaks, the detection end moves on the pipeline and is positioned to the leakage point of the pipeline, and when the natural gas pipeline does not leak, the detection end moves on the pipeline periodically to detect the defects on the inner and outer surfaces of the pipeline.

[0075] When the natural gas pipeline is magnetized, the magnetic induction lines at the defect of the pipeline are hindered by the pipeline defect, and the magnetic induction lines at the defect are distorted, at this time some magnetic induction lines will pass out from the inner and outer surfaces of the pipeline to form a magnetic leakage field. The magnetic leakage field leaked out is detected by a magnetic sensitive element (Hall sensor), so as to judge the size, shape and the like of the defect. A GPS positioning chip is also arranged on the detection end, and the positioning chip is used to position the position of the detection end.

[0076] The movement of the detection end is realized by guide wheels clamped on both sides of the pipeline, and the guide wheels are driven to run by a motor.

[0077] Please refer to Figure 5 When the surface of the pipeline has a defect, the defect area is filled with air, and since the magnetic resistance of the air is much greater than that in the pipeline, part of the magnetic induction lines will pass through the defect; according to the refraction law, another part of the magnetic induction lines will enter the air substantially perpendicularly from the surface of the pipeline, and after bypassing the defect, they will return to the pipeline to form a magnetic leakage field. The change of the magnetic leakage field can be detected by a detection circuit composed of magnetic sensors, and then the defect is judged according to the detected magnetic leakage signal. When the natural gas pipeline leaks, there is a defect at the leakage point, and the detection end is positioned at the defect position after detecting the defect, and sends the positioning information after confirming the leakage. During the periodic detection, when the pipeline has a defect (such as a small crack or a groove pit on the inner and outer surfaces of the pipeline) that may cause leakage, a timely warning is given.

[0078] The essence of the defect magnetic leakage field is an electromagnetic field, and the analysis of the electromagnetic field is generally completed by solving Maxwell's equations. At present, the commonly used methods for magnetic field analysis are mainly analytical method and numerical method. The analytical method mainly uses a simplified point magnetic dipole model to solve the magnetic leakage field at the defect, and the numerical method is to discretize the region formed by the solution of Maxwell's equations at the defect into a plurality of subspaces, and to solve the control equation by using an approximate condition.

[0079] wherein,

[0080] The point magnetic dipole model is used to solve the magnetic leakage field of pipeline defects such as holes, pits and points. Assuming that m is a point charge in space and P(x, y) is any point in space, then according to the relevant knowledge of static magnetism, the magnetic field generated by m at P is:

[0081]

[0082] In the formula, r is the distance from point P(x, y) to point magnetic charge m. The point magnetic dipole model plays a great role in promoting the study of defect magnetic leakage field.

[0083] When defect detection is performed using the principle of magnetic leakage field, whether the magnetic leakage generated at the defect can be detected by the detection end is greatly related to the magnetization intensity. If the magnetic field intensity is too small, the detection end is not easy to capture the magnetic leakage signal at the defect, affecting the reliability of pipeline defect detection. If the magnetic field intensity is too large, the detection end is easy to remain magnetic in the pipeline, affecting the service life of the pipeline.

[0084] Please refer to Figure 6 As shown, after a magnetic field is applied to the measured pipeline, the relationship between its magnetic induction intensity B and magnetic field intensity H is as follows: B = μ * H. The magnetic permeability μ of the material changes with the magnetic field intensity H, as shown in the μ-H curve in Figure 6 , the change of B and H is a nonlinear change, as shown in the B-H curve in Figure 6 . The pipeline magnetized by the permanent magnet conforms to the magnetization law of the curve.

[0085] Please refer to Figure 6 As shown, the entire curve is divided into three regions. In region 1, the curve slowly rises, which describes the slow increase of the magnetic induction intensity B with the change of the magnetic field intensity H. In region 2, the curve continues to rise, and the change is more dramatic than region 1. The curve is steep, and the magnetic induction intensity B increases dramatically with the change of the magnetic field intensity H. The maximum value of the magnetic permeability μ max appears in this region. In region 3, the curve tends to be flat and almost does not change, indicating that after this region, the magnetic induction intensity B almost does not change with the magnetic field intensity H.

[0086] Example 3

[0087] Please refer to Figure 2 As shown, the natural gas pipeline leakage detection system described in this embodiment includes a monitoring module, a detection module, a driving module, a positioning module and a control module.

[0088] Among them,

[0089] The monitoring module is used to monitor whether there is a gas leakage phenomenon in the pipeline in real time.

[0090] The detection module: when the monitoring module detects the air leakage point, the driving module drives the detection module to move to detect the air leakage point again, and the positioning module positions the air leakage point and sends an air leakage signal; when there is no air leakage point, the driving module periodically drives the detection module to move to detect the natural gas pipeline, and sends a warning signal when a defect is detected in the natural gas pipeline.

[0091] The control module: for receiving the air leakage signal and the warning signal, after data storage, the air leakage signal and the warning signal are sent to a remote computer through the Internet of Things.

[0092] The driving module includes guide wheels and supports clamped on both sides of the pipeline, and the guide wheels are driven to run by a motor.

[0093] The positioning module is a GPS positioning chip, which is used to position the position of the detection module.

[0094] The monitoring module includes an ASE light source, an optical circulator, a photodetector, a Faraday rotating mirror, a polarization controller, a phase modulator, a 2×2 optical coupler, a 1×2 optical coupler, a delay optical fiber and a sensing optical fiber.

[0095] The monitoring module includes the following steps:

[0096] (1) the light emitted by the ASE light source enters the No. 1 port of the optical circulator;

[0097] (2) then output from the No. 3 port of the optical circulator, enter the 2×2 optical coupler 1;

[0098] (3) the optical signal coming out of the optical coupler 1 is divided into two optical signals with a coupling ratio of 50:50;

[0099] (4) the two optical signals propagate along four optical paths respectively.

[0100] The detection module detects the defects on the inner and outer surfaces of the pipeline, including the following steps:

[0101] (1) magnetize the natural gas pipeline;

[0102] (2) the magnetic induction lines of the pipeline at the defect are hindered by the pipeline defect, and the magnetic induction lines at the defect are distorted;

[0103] (3) part of the magnetic induction lines pass out from the inner and outer surfaces of the pipeline, forming a magnetic leakage field;

[0104] (4) the magnetic leakage field leaked out is detected by a magnetic sensitive element to judge the size and shape of the defect.

[0105] Among them,

[0106] The magnetic leakage field is analyzed by point magnetic dipole model, including the following steps:

[0107] (1) Point magnetic dipole model is used to solve the magnetic leakage field of pipeline defects such as holes, pits and points;

[0108] (2) Let m be a point charge in space, and P(x, y) be an arbitrary point in space. The magnetic field generated by m at point P has a magnitude of:

[0109]

[0110] In the formula, r is the distance from point P(x, y) to point magnetic charge m.

[0111] The above embodiments can be realized wholly or partially by software, hardware, firmware or any combination thereof. When realized by software, the above embodiments can be realized wholly or partially in the form of a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, the processes or functions described in the embodiments of the present application are wholly or partially generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network or other programmable devices. The computer instructions can be stored in a computer-readable storage medium or transferred from one computer-readable storage medium to another, for example, the computer instructions can be transferred from one website, computer, server or data center to another by wired (such as infrared, wireless, microwave, etc.) mode. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server, data center and the like containing one or more available medium sets. The available medium can be a magnetic medium (such as a floppy disk, a hard disk, a magnetic tape), an optical medium (such as a DVD) or a semiconductor medium. The semiconductor medium can be a solid state disk.

[0112] It should be understood that the term "and / or" herein merely describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, and B exists alone, where A and B can be singular or plural. In addition, the character " / " herein generally represents that the associated objects before and after are an "or" relationship, but can also represent an "and / or" relationship, which can be understood according to the context before and after.

[0113] In this application, "at least one" means one or more, "multiple" means two or more. "At least one of the following (one)" or the like means any combination of these items, including any combination of single or multiple items. For example, at least one of a, b, or c can mean a, b, c, a-b, a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0114] It should be understood that the size of the sequence of the above processes in various embodiments of the present application does not mean the order of execution, and the execution order of the processes should be determined by its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0115] Those of ordinary skill in the art can realize that the units and algorithm steps of the examples described in conjunction with the embodiments disclosed herein can be realized in electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0116] Those skilled in the art can clearly understand that, for the convenience and brevity of the description, the specific working process of the above-described system, device and unit can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0117] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the above-described device embodiments are only schematic, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the shown or discussed units can be indirect coupling or communication connection through some interface, device or unit, which can be electrical, mechanical or other form.

[0118] The units described as separate components can or can not be physically separated, and the components shown as units can or can not be physical units, i.e. they can be located in one place or distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment.

[0119] In addition, each function unit in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit.

[0120] The functions, if implemented in the form of software function units and sold or used as independent products, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application, essentially or in part, or parts of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), magnetic disk or optical disk, and various other media that can store program codes.

[0121] The above is merely specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which shall be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A method for detecting leaks in natural gas pipelines, characterized in that: The detection method includes the following steps: S1: Construct an optical path measurement architecture on the pipeline to monitor for leaks in real time. This architecture includes an ASE light source, an optical circulator, a photodetector, a Faraday rotator, a polarization controller, a phase modulator, a 2×2 optical coupler, a 1×2 optical coupler, a delay fiber, and a sensing fiber. Step S1 involves the following steps in operating the optical path measurement architecture: S1.1: The light emitted by the ASE light source enters port 1 of the optical circulator; S1.2: The output from port 3 of the optical circulator then enters the 2×2 optical coupler; S1.3: The optical signal coming out of the 2×2 optical coupler is split into two optical signals with a coupling ratio of 50:50; S1.4: The two optical signals propagate along four different optical paths. The optical signal first passes through the phase modulator, then through the leakage point. The optical signal passes through the leakage point twice and is modulated twice. The expression for this is: ； In the formula, The amplitude of light. This is a leak point signal. Modulation amplitude for the leak point, Modulate the frequency for the leakage point. It is the angular frequency of the light wave. , These represent the times when light from path one passes through the leak point for the first and second time, respectively. For the amplitude of the modulated signal, The frequency of the modulation signal; The time it takes for light along path one to reach the phase modulator; The phase of the path light; When the optical signal propagates along optical path two, it is modulated twice at the leakage point, and then modulated again by the phase modulator. The expression after modulation is: ； in, The amplitude of light. This is a leak point signal. Modulation amplitude for the leak point, Modulate the frequency for the leakage point. It is the angular frequency of the light wave. , These represent the times when light from path two passes through the leak point for the first and second time, respectively. For the amplitude of the modulated signal, For modulating signal frequency, These represent the times when the two beams from the path arrive at the phase modulator. These represent the phases of the two beams along the path; S2: When there is a leak, based on the leak phenomenon detected by the optical path measurement architecture, the detection end is driven to move on the pipeline and locate the leak point in the pipeline, and the location information is sent to the processing end. S3: When there is no air leakage, the detection end moves on the pipeline periodically to detect defects on the inner and outer surfaces of the pipeline. When defects are found in the pipeline, the defect information is sent to the processing end for early warning.

2. The method for detecting gas leaks in a natural gas pipeline according to claim 1, characterized in that: When a natural gas pipeline leaks, the detection end moves along the pipeline and locates the leak point. When the natural gas pipeline is not leaking, the detection end moves along the pipeline periodically to detect defects on the inner and outer surfaces of the pipeline. The specific steps include: (1) Magnetized natural gas pipeline; (2) The magnetic field lines at the defect point of the pipeline are blocked by the pipeline defect, and the magnetic field lines at the defect point are distorted; (3) Some magnetic field lines emerge from the inner and outer surfaces of the pipe, forming a leakage magnetic field; (4) The leakage magnetic field is detected by the magnetic sensitive element to determine the size and shape of the defect.

3. The method for detecting gas leaks in a natural gas pipeline according to claim 2, characterized in that: The leakage magnetic field is analyzed using a point magnetic dipole model, including the following steps: (1) The leakage magnetic field of holes, pits and point pipe defects is solved by the point magnetic dipole model; (2) Let m be a point charge in space, For any point in space, exist The magnitude of the magnetic field generated at point is: ； In the formula, For point Point magnetic charge The distance.

4. The method for detecting gas leaks in a natural gas pipeline according to claim 3, characterized in that: After a magnetic field is applied to the pipe, the magnetic induction intensity With magnetic field strength The calculation formula between the two is: ； In the formula, Let be the magnetic permeability of the material, and With magnetic field strength Change with change.

5. A natural gas pipeline leak detection system, said detection system being used to implement the natural gas pipeline leak detection method according to any one of claims 1-4, characterized in that: It includes a monitoring module, a detection module, and a control module; When the monitoring module detects a leak, the drive module moves the detection module to detect the leak point a second time. The positioning module locates the leak point and sends a leak signal. When there is no leak, the drive module periodically moves the detection module to detect the natural gas pipeline. When a defect is detected in the natural gas pipeline, an early warning signal is issued. The control module receives the leak signal and the early warning signal and sends them to a remote computer via the Internet of Things.

6. A natural gas pipeline leak detection system according to claim 5, characterized in that: The drive module consists of guide wheels and a bracket clamped on both sides of the pipe. The guide wheels are driven by a motor. The positioning module is a GPS positioning chip, which is used to locate the position of the detection module.

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