CN111536892B - Underground pipeline monitoring system and monitoring method based on distributed optical fiber sensing - Google Patents
Underground pipeline monitoring system and monitoring method based on distributed optical fiber sensing Download PDFInfo
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- CN111536892B CN111536892B CN202010532139.6A CN202010532139A CN111536892B CN 111536892 B CN111536892 B CN 111536892B CN 202010532139 A CN202010532139 A CN 202010532139A CN 111536892 B CN111536892 B CN 111536892B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
- G01B11/18—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge using photoelastic elements
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
- G01K11/324—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres using Raman scattering
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Abstract
The invention provides an underground pipeline monitoring system and a monitoring method based on distributed optical fiber sensing, which utilize an armored photoelectric composite cable arranged outside an underground pipeline, a high-resolution optical camera with night vision function arranged along the underground pipeline, an automatic monitoring and early warning system and a DSS/DTS/DAS composite distributed optical fiber sensing modem instrument arranged in a monitoring station along the line, and a long-term real-time monitoring system based on distributed optical fiber sensing and distributed variation of temperature, vibration and strain along the underground pipeline. The underground pipeline and the oil gas conveying pipeline are effectively prevented from being stolen, excavated and damaged, prevented from being damaged by fire, prevented from being damaged by natural and geological disasters, and can effectively avoid or reduce loss, ensure long-term stable, safe and reliable work of the underground pipeline, and provide indispensable means, systems and methods for scientific management of the underground pipeline and improvement of the use efficiency.
Description
Technical Field
The invention belongs to the technical field of temperature, vibration and strain measurement, and particularly relates to an underground pipeline monitoring system and method based on distributed optical fiber sensing.
Background
Underground pipelines, particularly oil and gas conveying pipelines, are large arteries for energy transportation, bear the transmission task of a large amount of oil and gas resources of China, relate to national security, harmony and stability and development of economy and society, have the conventional pipeline 10 of China for tens of thousands of kilometers, and have the pipeline to pass through various different environments such as densely populated towns, villages, farmlands, rivers, swamps, deserts, roads, railways and the like along the way, and the safety of the underground pipelines is threatened at all times by various factors such as construction, artificial damage (such as perforation and oil theft) and natural disasters (such as natural earthquakes, floods, landslides, debris flows and the like) around the pipeline. Because of the hazards and pollution of the underground pipeline transportation medium, once leakage or collapse accidents occur, huge life and property losses and environmental pollution are caused. The underground pipeline and the oil gas conveying pipeline are effectively prevented from being stolen, excavated and damaged, prevented from being fire, prevented from being damaged by natural and geological disasters, and can effectively avoid or reduce loss. The existing part of pipelines and oil gas conveying pipelines are buried underground, and high technical requirements are required for on-line real-time monitoring and alarming of the pipelines due to the fact that the conveying distance is long and the environment is complex. The traditional monitoring method mainly comprises manual inspection and buried point type vibration detection alarm, and whether leakage occurs or not is judged through the change of parameters such as pipeline conveying pressure, flow, temperature change and the like. The mode is complex in operation, high in cost, labor and financial resources wasting, low in automation degree, poor in anti-interference capability, low in sensitivity to tiny leakage and alarming after leakage, and is influenced by factors such as material conveying characteristics and conveying working conditions; moreover, the phenomenon of missed inspection can occur in manual inspection, so that a plurality of hidden dangers which can be prevented cannot be treated in time, and the hidden dangers are increased until accidents occur. Therefore, an automatic monitoring and early warning system for underground pipelines, particularly underground oil and gas pipelines, is needed.
Optical fiber sensing technology began in 1977 and developed rapidly with the development of optical fiber communication technology, and the optical fiber sensing technology is an important sign for measuring the informatization degree of a country. The optical fiber sensing technology is widely applied to the fields of military, national defense, aerospace, industrial and mining enterprises, energy environmental protection, industrial control, medicine and health, metering test, construction, household appliances and the like, and has wide markets. There are hundreds of optical fiber sensing technologies in the world, such as sensing of different properties of physical quantities such as temperature, pressure, flow, displacement, vibration, rotation, bending, liquid level, speed, acceleration, sound field, current, voltage, magnetic field and radiation.
The distributed optical fiber temperature measurement system (DTS: distributed Temperature Sensing) is also called optical fiber temperature measurement, and temperature monitoring is realized according to the Optical Time Domain Reflection (OTDR) principle and the sensitivity of Raman (Raman) scattering effect to temperature. The distributed optical fiber temperature measurement system can be divided into three types according to the backscattering principle: based on Rayleigh scattering, based on Raman scattering and based on Brillouin scattering. At present, the development is mature, and a product is applied to engineering and is a distributed optical fiber temperature measurement system based on Raman scattering. The sensing principle is mainly based on optical time domain reflection of the optical fiber and the backward Raman scattering temperature effect of the optical fiber. The whole system adopts optical fibers as carriers for sensing sensitive information and transmitting signals, has the characteristics of continuous temperature measurement, distributed temperature measurement, real-time temperature measurement, electromagnetic interference resistance, intrinsic safety, remote monitoring, high sensitivity, simple installation, long service life and the like, and is widely applied to industries such as municipal comprehensive pipe racks, pipelines, tunnels, cables, petroleum and petrochemical industry, coal mines and the like.
A distributed optical fiber sound wave sensing (DAS) technology is a novel sensing technology capable of realizing vibration and sound field continuous distributed detection. The method utilizes the characteristic that coherent Rayleigh scattering excited by narrow linewidth single-frequency laser in the optical fiber is highly sensitive to strain change, and combines the reflectometer principle to sense the environmental vibration and sound field information interacted with the optical fiber in a long distance with high space-time precision. This unique information-awareness has led to a great deal of attention in both academia and industry. The DAS technical performance is continuously improved, the rapid development is applied, and the unique technical advantages and potential of the DAS are shown in the aspects of perimeter intrusion detection, railway safety online monitoring, geophysical exploration and the like.
The strain measurement is a basic task in mechanical property tests of materials and structures, is a basis for knowing deformation, damage and failure behaviors of the materials under the action of factors such as mechanical loads, and has important values for determining allowable values of structural design, predicting and evaluating service lives of the structures and the like. The strain measurement method mainly comprises the following steps: electrical measurement, optical measurement, acoustic emission, brittle coating, strain mechanical measurement, and the like. Among them, electrical and optical measurement methods are most widely used. The optical measurement method is a measurement method for researching mechanical quantities such as stress, strain and displacement in a structure by an experimental means by applying an optical principle. The optical measurement method comprises photoelastic, holographic interference, laser speckle interference, moire method and the like. The optical fiber strain measurement method uses an optical fiber as a sensing medium, and utilizes an optical principle and technology to measure the strain quantity of a measured object by detecting and measuring the change of optical parameters such as the intensity, the phase, the polarization state, the wavelength and the like of light due to the action of external factors (such as tension, pressure and the like).
With the development of optical technology, a quasi-distributed optical fiber sensor represented by an optical Fiber Bragg Grating (FBG) sensor and the like is also presented, however, the measuring point of the optical fiber bragg grating sensor is limited by the bandwidth of laser. Nowadays, the distributed optical fiber sensing technology is mature, and the distributed optical fiber sensor based on the back Rayleigh scattering has good precision, linearity and repeatability in the aspect of strain measurement and can have the potential of replacing the traditional resistance strain gauge and the fiber Bragg grating sensor in various fields. The distributed optical fiber sensor has the characteristics of extremely high measuring point density, controllable distance, small mass, corrosion resistance, electric insulation, high precision and good repeatability. In addition, it has better adaptability to the shape of the structural surface based on the soft and tough nature of the texture. Although quasi-distributed optical fiber sensors represented by Fiber Bragg Grating (FBG) sensors and the like can be used for strain measurement and real-time long-term monitoring along the underground pipeline, the measuring points of the fiber bragg grating sensors are limited by laser bandwidth, and are not suitable for high-density or high-spatial-resolution multi-measuring point strain measurement and real-time monitoring along the underground pipeline with ultra-long distance.
The traditional monitoring method for monitoring the existing underground pipeline mainly comprises manual inspection and buried point-type vibration detection alarm, and whether leakage occurs or not is judged through the change of parameters such as pipeline conveying pressure, flow and temperature change. The mode is complex in operation, high in cost, labor and financial resources wasting, low in automation degree, poor in anti-interference capability and low in sensitivity, is influenced by factors such as material conveying characteristics and conveying working conditions, is low in sensitivity to tiny leakage, and alarms after leakage. Moreover, the phenomenon of missed inspection can occur in manual inspection, so that a plurality of hidden dangers which can be prevented cannot be treated in time, and the hidden dangers are increased until accidents occur.
Disclosure of Invention
The invention provides an underground pipeline monitoring system based on distributed optical fiber sensing, which utilizes an armored photoelectric composite cable arranged on the outer side of an underground pipeline, a high-resolution optical camera with night vision function arranged along the underground pipeline, a monitoring and early warning system arranged in a monitoring station along the line and a DSS/DTS/DAS composite distributed optical fiber sensing modem instrument arranged in the monitoring station along the line to construct a long-term real-time monitoring system based on distributed optical fiber sensing and distributed change of temperature, vibration and strain along the underground pipeline.
The invention aims to overcome the defects of the traditional monitoring method used for monitoring the existing underground pipeline, and provides an automatic monitoring and early warning system which is arranged in a monitoring station along the pipeline and a DSS/DTS/DAS composite distributed optical fiber sensing modem instrument which is arranged in the monitoring station along the pipeline by combining a high-resolution optical camera which is arranged on the outside of the underground pipeline and has night vision function along the pipeline, so as to construct a long-term real-time monitoring system which is based on distributed optical fiber sensing and is used for monitoring the temperature, vibration and strain distribution change condition of the underground pipeline along the pipeline, timely find the abnormal section along the pipeline, automatically verify and identify and provide early warning or alarm in real time, and ensure the long-term stable, safe and reliable operation of the underground pipeline, particularly an oil gas conveying pipeline.
In order to achieve the above purpose, the specific technical scheme of the invention is as follows:
The underground pipeline monitoring system based on distributed optical fiber sensing comprises an underground pipeline, wherein an armored photoelectric composite cable is arranged along the outer side of the underground pipeline, and comprises an optical fiber and a plurality of metal wires with insulating layers;
On the ground, a line monitoring station and a high-resolution optical camera are arranged along the underground pipeline;
the high-resolution optical camera has a night vision function, is connected with a metal wire of the armored photoelectric composite cable, and is arranged on an attitude control motor capable of being controlled and adjusted remotely and in real time;
An automatic monitoring and early warning system and a DSS/DTS/DAS composite modem instrument are arranged in the line monitoring station; the DSS/DTS/DAS composite modem instrument is connected with an optical fiber in the armored photoelectric composite cable.
Further, the DSS/DTS/DAS composite modem instrument comprises distributed optical fiber strain sensing, distributed optical fiber temperature sensing and distributed optical acoustic wave sensing data acquisition and modem functions.
The armored photoelectric composite cable comprises an optical fiber and a plurality of metal wires with insulating layers, wherein the optical fiber comprises a single-mode optical fiber, a multimode optical fiber, a special strain sensitive optical fiber and a continuous grating optical fiber, and continuous metal tubules are sequentially packaged outside the optical fiber.
Further, the continuous metal tubule and the metal wire with the insulating layer are also wound with single-layer or multi-layer armoured steel wires.
Furthermore, the continuous metal tubule is also filled with optical fiber paste; at equidistant locations, the optical fiber is fixed to the inner wall of the continuous metal tubule with epoxy. In addition, before the continuous metal tubule is welded by laser, the continuous optical fiber and the inner wall of the continuous metal tubule are fixed together by epoxy resin at the equidistant (between 10 meters and 100 meters) position, so that the optical fiber can timely and sensitively detect the strain produced after the underground ground stress acts on the underground pipeline and the armored photoelectric composite cable.
Furthermore, the optical fiber arranged in the continuous metal tubule also comprises a high-sensitivity strain special optical fiber which is tightly wrapped by a high-strength composite material or is manufactured by wrapping a single-mode optical fiber by one-step molding of an injection molding machine, and the optical fiber is tightly adhered to and sealed in the continuous metal tubule.
Further, a plurality of high-resolution optical cameras with night vision function are arranged along the underground pipeline, the high-resolution optical cameras are connected with metal wires in the armored photoelectric composite cable, the metal wires are used for providing power for the high-resolution optical cameras and transmitting image data, and the high-resolution optical cameras are remotely controlled and adjusted in real time through an attitude control motor connected below the high-resolution optical cameras.
When strain/temperature measurements are made using distributed fiber optic sensors, the back Rayleigh scattering is measured using wavelength scanning interferometry and is used as a function of position on the fiber. Rayleigh scattering in an optical fiber occurs due to refractive index fluctuations along the length of the fiber. Scattering is random, but if the state of the fiber is unchanged for a given fiber, it always produces reflected light of the same wavelength, an inherent characteristic known as the inherent texture information of the fiber. If a certain position of the optical fiber is deformed by the influence of load or temperature, the reflected light wavelength at that position is only shifted, and it is possible to confirm at which position of the optical fiber the deformation occurs by comparing the reflected light before and after the deformation. In general, the drift of the spectrum of scattered light in an optical fiber is mainly caused by strain or temperature changes. The spectral shift is similar to the shift Deltaλ of the resonance wave or the spectral shift Deltav of the Bragg grating, which is obtained from the strain epsilon or the temperature t response, namely:
Δλ/λ＝-Δυ/υ＝KTΔt+Kεε
Wherein: lambda and v are the average wavelength and frequency, respectively; k T and K ε are temperature and strain standard constants, respectively, K T＝6.45μ℃-1,Kε =0.78 for most germanosilicate core fibers.
The gauge length (GaugeLength) of the distributed fiber optic sensor is adjustable, but the gauge length affects the spectral resolution and the signal-to-noise ratio of the measurement signal. Generally, the longer the gauge length, the higher the measurement accuracy. Aiming at different structural forms and strain states, strain measurement can be designed and carried out by using different gauge length, and when the gauge length is larger, the measurement accuracy is high and the noise is small; and when the gauge length is smaller, the measuring point density is high, and the detailed description of the strain field is complete.
The monitoring method of the underground pipeline monitoring system based on distributed optical fiber sensing comprises the following steps:
(a) Laying an armored photoelectric composite cable along the underground pipeline, wherein the armored photoelectric composite cable can be fixed on the top of the underground pipeline, can be fixed on two sides or the bottom of the underground pipeline, and can be buried beside the underground pipeline;
(b) Placing an automatic monitoring and early warning system and a DSS/DTS/DAS composite modem instrument in the line monitoring station;
(c) A high-resolution optical camera with night vision function is arranged along the underground pipeline, and a gesture control motor capable of performing remote real-time control and adjustment is connected below the high-resolution optical camera;
(d) Connecting the high-resolution optical camera and the gesture control motor with a metal wire in the armored photoelectric composite cable;
(e) Respectively connecting a DSS/DTS/DAS composite modem instrument with special strain sensitive optical fibers, 2 multimode optical fibers or 2 high-density continuous grating optical fibers and single-mode optical fibers which are arranged in the armored photoelectric composite cable;
(f) The data output end of the DSS/DTS/DAS composite modem instrument is connected with an automatic monitoring and early warning system;
(i) Modulating and demodulating a DSS signal, a DTS signal and a DAS signal which are continuously measured by a DSS/DTS/DAS composite modulation and demodulation instrument, converting DSS output data into strain generated by any local stress acting on an armored photoelectric composite cable along an underground pipeline, converting DTS output data into distribution data of any local temperature change along the underground pipeline, and converting DAS output data into distribution data of any local vibration change along the underground pipeline;
(j) The automatic monitoring and early warning system processes and analyzes the distribution data of any local temperature change along the underground pipeline in real time, when the situation that any local part along the underground pipeline is abnormal in high temperature is found, a high-resolution optical camera which is monitoring the high-temperature abnormal section of the underground pipeline is adjusted to timely focus and shoot a high-resolution photo or video of the high-temperature abnormal section of the underground pipeline, the high-resolution photo or video is transmitted back to the automatic monitoring and early warning system for real-time display, and operators on duty along the monitoring station process in real time or immediately alarm according to the actual situation of the high-temperature abnormal section of the underground pipeline;
(k) The automatic monitoring and early warning system processes and analyzes the distribution data of any local vibration change along the underground pipeline in real time, when the vibration abnormality of any local part along the underground pipeline is found, a high-resolution optical camera which is monitoring the vibration abnormality zone of the underground pipeline is adjusted to timely focus and shoot a high-resolution picture or video of the vibration abnormality zone of the underground pipeline, and the high-resolution picture or video is transmitted back to the automatic monitoring and early warning system to be displayed in real time, and operators on duty along the monitoring station process or immediately alarm according to the actual condition of the vibration abnormality zone of the underground pipeline;
(l) Based on the temperature data along the underground pipeline monitored and measured by the DTS system, the formula is utilized:
Δλ/λ＝-Δυ/υ＝KTΔt+Kεε
wherein lambda and upsilon are average light wavelength and frequency respectively; k T and K ε are temperature and strain standard constants, respectively;
Correcting DSS measured data by using the temperature value of a specific measuring position to carry out drift of scattered light spectrum in the optical fiber caused by temperature change, so as to obtain a real strain value of the outer wall of the underground pipeline, wherein the temperature influence is eliminated;
(m) solving the differential of the strain quantity of the outer wall of the underground pipeline, which is monitored and measured in real time for a long time, to time so as to obtain the change rate of the strain quantity along with time;
And (n) analyzing the strain quantity and the strain rate of the outer wall of the underground pipeline, which are monitored and measured in real time for a long time, and timely giving an early warning or an alarm when the local strain quantity and the strain rate of the underground pipeline are found to exceed the threshold value and a section which possibly causes local deformation damage of the underground pipeline according to the strain quantity and the strain rate threshold value standard of the underground pipeline, which are set by pipeline engineering.
The optical fiber strain measurement method uses an optical fiber as a sensing medium, and utilizes an optical principle and technology to measure the strain quantity of a measured object by detecting and measuring the change of optical parameters such as the intensity, the phase, the polarization state, the wavelength and the like of light due to the action of external factors (such as tension, pressure and the like).
The distributed optical fiber strain detection technology based on Brillouin optical time domain reflection (BOTDR: reflector Domain Time Optical Brillouin) has the advantages of single-ended input, long measurement distance, measurable break points, full distributed detection and the like, and can be effectively applied to structural health state monitoring of large-scale basic engineering. The strain detector based on BOTDR combines a coherent detection method and a microwave heterodyne sweep method to realize detection of the Brillouin scattering signal, and utilizes the advantage of high-speed operation of the FPGA to realize noise reduction of the Brillouin scattering signal and demodulation of a Brillouin gain spectrum so as to improve real-time performance of strain detection. The strain quantity and the strain rate along the underground pipeline which are monitored or detected for a long time can effectively ensure the long-term stable, safe and reliable work of the underground pipeline in an early warning or alarming mode.
The distributed optical fiber temperature measurement system (DTS) is used for measuring temperature change along the underground in real time, and the principle is that the space temperature distribution information is obtained by the Raman scattering and Optical Time Domain Reflection (OTDR) principle generated when light is transmitted in an optical fiber. After the high-power narrow-pulse-width laser pulse LD is incident on the sensing optical fiber, weak back scattering light is generated, and the light is respectively Rayleigh (Rayleigh), anti-Stokes (Anti-Stokes) light and Stokes (Stokes) light according to different wavelengths. DTS is the most widely used distributed temperature monitoring technique that can accurately measure the temperature per decimeter on an optical fiber, with a maximum operating temperature up to 300 ℃, precisely to 0.1 ℃ and a resolution of 0.01 ℃. Because the scattered light spectrum in the optical fiber can drift due to the change of the temperature and the strain along the underground pipeline, the temperature change value of the abnormal area of the underground pipeline needs to be monitored or measured by using the strain to correct the temperature influence on the drift of the scattered light spectrum in the optical fiber caused by the strain or the temperature change, so that only the strain caused by the change of the stress field along the underground pipeline is finally obtained, and the accuracy of the strain monitoring or the measurement is improved.
A distributed optical fiber sound wave sensing (DAS) technology is a novel sensing technology capable of realizing vibration and sound field continuous distributed detection. The method utilizes the characteristic that coherent Rayleigh scattering excited by narrow linewidth single-frequency laser in the optical fiber is highly sensitive to strain change, and combines the reflectometer principle to sense the environmental vibration and sound field information interacted with the optical fiber in a long distance with high space-time precision. This unique information-awareness has led to a great deal of attention in both academia and industry. The DAS technical performance is continuously improved, the rapid development is applied, and the unique technical advantages and potential of the DAS are shown in the aspects of perimeter intrusion detection, railway safety online monitoring, geophysical exploration and the like.
The underground pipeline monitoring system based on distributed optical fiber sensing and the monitoring method thereof provided by the invention are a low-cost, high-precision and high-reliability dynamic monitoring method and technology for the temperature, vibration and strain distribution change along the underground pipeline. The invention provides an underground pipeline monitoring system based on distributed optical fiber sensing, which utilizes an armored photoelectric composite cable arranged on the outer side of an underground pipeline, a high-resolution optical camera with night vision function arranged along the underground pipeline, an automatic monitoring and early warning system and a DSS/DTS/DAS composite distributed optical fiber sensing modem instrument arranged in a monitoring station along the line, and a long-term real-time monitoring system based on distributed optical fiber sensing and distributed change of temperature, vibration and strain along the line, so that the long-term stable, safe and reliable work of the underground pipeline is effectively ensured, and an indispensable means, system and method are provided for scientific management and improvement of the service efficiency of the underground pipeline.
Drawings
Fig. 1 is a schematic diagram of the system configuration of the present invention.
Fig. 2 is a schematic view of the layout position of the underground pipeline and the armored photoelectric composite cable of the invention.
Fig. 3 is a schematic cross-sectional view of an armored photoelectric composite cable of the present invention.
Fig. 4 is a schematic cross-sectional view of an armored photoelectric composite cable of the present invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but they are not to be construed as limiting the invention, but merely as exemplifications, and are intended to provide advantages of the invention as more clearly and more readily understood.
The specific implementation mode of the underground pipeline monitoring system based on distributed optical fiber sensing is as follows:
As shown in fig. 1, the underground pipeline monitoring system based on distributed optical fiber sensing comprises an underground pipeline 1, an armored photoelectric composite cable 2 arranged outside the underground pipeline, a high-resolution optical camera 3 arranged on the underground pipeline along the line with night vision function, an attitude control motor 6 capable of being controlled and adjusted remotely and in real time, and an automatic monitoring and early warning system 4 arranged in a monitoring station along the line;
the system also comprises a DSS/DTS/DAS composite modem instrument 5 which is arranged in the monitoring station along the line; the DSS/DTS/DAS composite modem instrument 5 is respectively connected with an optical fiber 21 arranged in the photoelectric composite cable 2.
The DSS/DTS/DAS composite modem instrument 5 comprises distributed optical fiber strain sensing, distributed optical fiber temperature sensing and distributed optical fiber acoustic wave sensing data acquisition and modem functions.
As shown in fig. 2, the armored photoelectric composite cable 2 includes an optical fiber 21 and a plurality of metal wires 23 with insulating layers, the optical fiber 21 includes a single-mode optical fiber, a multimode optical fiber, a special strain sensitive optical fiber, and a continuous grating optical fiber, and the optical fiber 21 is sequentially packaged with a continuous metal tubule 22.
The continuous metal tubule 22 and the metal wire 23 with insulating layer are also wound with single or multi-layer armoured steel wires 25.
As shown in fig. 3, the continuous metal tubule 22 is also impregnated with optical fiber paste; before the metal tubule 22 is welded by laser, the optical fiber 21 and the inner wall of the continuous metal tubule 22 are fixed together by epoxy resin 24 at equidistant (between 10 meters and 100 meters) positions, so that the optical fiber 21 in the armored photoelectric composite cable 2 can timely and sensitively detect the strain produced after the stress acts on the armored photoelectric composite cable 2.
The optical fiber 21 arranged in the continuous metal tubule 22 also comprises a high-sensitivity strain special optical fiber which is tightly wrapped by a high-strength composite material or is manufactured by wrapping a single-mode optical fiber by one-step molding of an injection molding machine, and the optical fiber 21 is tightly adhered and sealed in the continuous metal tubule 22.
The underground pipeline monitoring system based on distributed optical fiber sensing is provided with a plurality of high-resolution optical cameras 3 with night vision function, the high-resolution optical cameras 3 with the night vision function are arranged along the underground pipeline, the high-resolution optical cameras 3 with the night vision function are connected with a metal wire 23 in the armored photoelectric composite cable 2, the metal wire 23 is used for providing power for the high-resolution optical cameras 3 with the night vision function, transmitting image data, and remotely controlling and adjusting the high-resolution optical cameras 3 in real time through an attitude control motor 6 connected below the high-resolution optical cameras 3.
A distributed optical fiber sound wave sensing (DAS) technology is a novel sensing technology capable of realizing vibration and sound field continuous distributed detection. The method utilizes the characteristic that coherent Rayleigh scattering excited by narrow linewidth single-frequency laser in the optical fiber is highly sensitive to strain change, and combines the reflectometer principle to sense the environmental vibration and sound field information interacted with the optical fiber in a long distance with high space-time precision.
When strain/temperature measurements are made using distributed fiber optic sensors, the back Rayleigh scattering is measured using wavelength scanning interferometry and is used as a function of position on the fiber. Rayleigh scattering in an optical fiber occurs due to refractive index fluctuations along the length of the fiber. Scattering is random, but if the state of the fiber is unchanged for a given fiber, it always produces reflected light of the same wavelength, an inherent characteristic known as the inherent texture information of the fiber. If a certain position of the optical fiber is deformed by the influence of load or temperature, the reflected light wavelength at that position is only shifted, and it is possible to confirm at which position of the optical fiber the deformation occurs by comparing the reflected light before and after the deformation. In general, the drift of the spectrum of scattered light in an optical fiber is mainly caused by strain or temperature changes. The spectral shift is similar to the shift Deltaλ of the resonance wave or the spectral shift Deltav of the Bragg grating, which is obtained from the strain epsilon or the temperature t response, namely:
Δλ/λ＝-Δυ/υ＝KTΔt+Kεε
Wherein: lambda and v are the average wavelength and frequency, respectively; k T and K ε are temperature and strain standard constants, respectively, K T＝6.45μ℃-1,Kε =0.78 for most germanosilicate core fibers.
The gauge length (GaugeLength) of the distributed fiber optic sensor is adjustable, but the gauge length affects the spectral resolution and the signal-to-noise ratio of the measurement signal. Generally, the longer the gauge length, the higher the measurement accuracy. Aiming at different structural forms and strain states, strain measurement can be designed and carried out by using different gauge length, and when the gauge length is larger, the measurement accuracy is high and the noise is small; and when the gauge length is smaller, the measuring point density is high, and the detailed description of the strain field is complete.
The monitoring method of the underground strain distribution monitoring system based on distributed optical fiber sensing comprises the following steps:
1. Laying the armored photoelectric composite cable 2 along the underground pipeline 1, wherein the armored photoelectric composite cable 2 can be fixed on the top of the underground pipeline 1, can be fixed on two sides or the bottom of the underground pipeline 1, and can be buried beside the underground pipeline 1 as shown in fig. 4;
2. An automatic monitoring and early warning system 4 and a DSS/DTS/DAS composite modem instrument 5 of the underground pipeline 1 are arranged in a monitoring station along the underground pipeline 1;
3. A high-resolution optical camera 3 with night vision function is arranged along the underground pipeline 1, and an attitude control motor 6 capable of performing remote real-time control adjustment is connected below the high-resolution optical camera 3;
4. connecting the high-resolution optical camera 3 and the attitude control motor 6 with the metal wire 23 in the armored photoelectric composite cable 2;
5. the DSS/DTS/DAS composite modem instrument 5 arranged in the monitoring station along the line is respectively connected with special strain sensitive optical fibers, 2 multimode optical fibers or 2 high-density continuous grating optical fibers and single-mode optical fibers which are arranged in the photoelectric composite cable 2;
6. The data output end of the DSS/DTS/DAS composite modem instrument 5 is connected with an automatic monitoring and early warning system 4;
7. the DSS signal, the DTS signal and the DAS signal which are continuously measured by the DSS/DTS/DAS composite modem instrument 5 are modulated and demodulated, DSS output data are converted into strain generated by any local stress acting on the armored photoelectric composite cable 2 along the underground pipeline 1, DTS output data are converted into distribution data of any local temperature change along the underground pipeline 1, and DAS output data are converted into distribution data of any local vibration change along the underground pipeline 1;
8. The automatic monitoring and early warning system 4 processes and analyzes the distribution data of any local temperature change along the underground pipeline 1 in real time, when the situation that any local part along the underground pipeline 1 is abnormal at high temperature is found, a high-resolution optical camera 3 which is monitoring the high-temperature abnormal section of the underground pipeline 1 is adjusted to timely focus and shoot a high-resolution photo or video of the high-temperature abnormal section of the underground pipeline 1, and the high-resolution photo or video is transmitted back to the automatic monitoring and early warning system 4 to be displayed in real time, and operators on duty of the underground pipeline 1 along the monitoring station process in real time or immediately alarm according to the actual situation of the high-temperature abnormal section of the underground pipeline 1;
9. The automatic monitoring and early warning system 4 processes and analyzes the distribution data of any local vibration change along the underground pipeline 1 in real time, when any local vibration abnormality of the underground pipeline 1 is found, a high-resolution optical camera 3 which is monitoring the vibration abnormality zone of the underground pipeline 1 is adjusted to timely focus and shoot a high-resolution picture or video of the vibration abnormality zone of the underground pipeline 1, and the picture or video is transmitted back to the automatic monitoring and early warning system 4 for real-time display, and an attendant of a monitoring station along the underground pipeline 1 processes or immediately alarms according to the actual condition of the vibration abnormality zone of the underground pipeline 1 in real time;
10. Based on the temperature data along the underground pipeline 1 monitored and measured by the DTS system, the formula is used:
Δλ/λ＝-Δυ/υ＝KTΔt+Kεε
wherein lambda and upsilon are average light wavelength and frequency respectively; k T and K ε are temperature and strain standard constants, respectively;
correcting DSS measured data by using the temperature value of a specific measuring position to carry out drift of scattered light spectrum in the optical fiber caused by temperature change, so as to obtain a real strain value of the outer wall of the underground pipeline 1 without temperature influence;
11. The differential of the strain quantity of the outer wall of the underground pipeline 1, which is monitored and measured in real time for a long time, is obtained, and the change rate of the strain quantity along with time is obtained;
12. Analyzing the strain quantity and the strain rate of the outer wall of the underground pipeline 1, which are monitored and measured in real time for a long time, and according to the strain quantity and the strain rate threshold standard of the underground pipeline 1 set by pipeline engineering, when the local strain quantity and the strain rate of the underground pipeline 1 are found to exceed the threshold and the local deformation damage section of the underground pipeline 1 is possibly caused, timely giving an early warning or an alarm.
The underground pipeline monitoring system and the monitoring method based on the distributed optical fiber sensing provided by the embodiment are low-cost, high-precision and high-reliability dynamic monitoring methods and technologies for temperature, vibration and strain distribution changes along the underground pipeline. The invention provides an underground pipeline monitoring system based on distributed optical fiber sensing, which utilizes an armored photoelectric composite cable arranged on the outer side of an underground pipeline, a high-resolution optical camera with night vision function arranged along the underground pipeline, an automatic monitoring and early warning system and a DSS/DTS/DAS composite distributed optical fiber sensing modem instrument arranged in a monitoring station along the line, and a long-term real-time monitoring system based on distributed optical fiber sensing and distributed change of temperature, vibration and strain along the underground pipeline is constructed. Effectively ensures the long-term stable safe and reliable work of the underground pipeline, and provides an indispensable means, system and method for scientific management of the underground pipeline and improvement of the use efficiency.
Claims (1)
1. The monitoring method of the underground pipeline monitoring system based on the distributed optical fiber sensing comprises an underground pipeline (1), wherein an armored photoelectric composite cable (2) is arranged along the outer side of the underground pipeline (1), and the armored photoelectric composite cable (2) comprises an optical fiber (21) and a plurality of metal wires (23) with insulating layers;
on the ground, a line monitoring station and a high-resolution optical camera (3) are arranged along the underground pipeline (1);
The high-resolution optical camera (3) has a night vision function, the high-resolution optical camera (3) is connected with a metal wire (23) of the armored photoelectric composite cable (2), and the high-resolution optical camera (3) is arranged on a gesture control motor (6) capable of being controlled and adjusted remotely and in real time;
An automatic monitoring and early warning system (4) and a DSS/DTS/DAS composite modem instrument (5) are arranged in the line monitoring station; the DSS/DTS/DAS composite modem instrument (5) is connected with an optical fiber (21) in the armored photoelectric composite cable (2);
the DSS/DTS/DAS composite modem instrument (5) comprises distributed optical fiber strain sensing, distributed optical fiber temperature sensing and distributed optical fiber acoustic wave sensing data acquisition and modem functions;
The optical fiber (21) comprises a single-mode optical fiber, a multimode optical fiber, a special strain sensitive optical fiber and a continuous grating optical fiber, and a continuous metal tubule (22) is packaged outside the optical fiber (21);
The continuous metal tubule (22) and the metal wire (23) with an insulating layer are also wound with a single-layer or multi-layer armoured steel wire (25);
The continuous metal tubule (22) is also filled with optical fiber paste; fixing the optical fiber (21) on the inner wall of the continuous metal tubule (22) at equidistant positions by using epoxy resin (24);
the optical fiber (21) also comprises a high-sensitivity strain special optical fiber which is tightly wrapped by a high-strength composite material or is manufactured by wrapping a single-mode optical fiber by one-step molding of an injection molding machine, and the optical fiber (21) is tightly adhered and sealed in the continuous metal tubule (22);
the metal wire (23) is used for providing power for the high-resolution optical camera (3), transmitting image data and remotely controlling and adjusting the high-resolution optical camera (3) in real time through the gesture control motor (6);
The method is characterized by comprising the following steps:
(a) Laying an armored photoelectric composite cable (2) along the underground pipeline (1), wherein the armored photoelectric composite cable (2) is fixed on the top of the underground pipeline (1), or is fixed on two sides or the bottom of the underground pipeline (1), or is buried beside the underground pipeline (1);
(b) An automatic monitoring and early warning system (4) and a DSS/DTS/DAS composite modem instrument (5) are arranged in the underground pipeline (1) along the monitoring station;
(c) A high-resolution optical camera (3) is arranged along the underground pipeline (1), and an attitude control motor (6) capable of performing remote real-time control adjustment is connected below the high-resolution optical camera (3);
(d) Connecting the high-resolution optical camera (3) and the attitude control motor (6) with a metal wire (23) in the armored photoelectric composite cable (2);
(e) The DSS/DTS/DAS composite modem instrument (5) is respectively connected with an optical fiber (21) arranged in the armored photoelectric composite cable (2);
(f) The data output end of the DSS/DTS/DAS composite modem instrument (5) is connected with an automatic monitoring and early warning system (4);
(i) Modulating and demodulating DSS signals, DTS signals and DAS signals which are continuously measured by a DSS/DTS/DAS composite modem instrument (5), converting DSS output data into strain generated by any local stress acting on an armored photoelectric composite cable (2) along an underground pipeline (1), converting DTS output data into distribution data of any local temperature change along the underground pipeline (1), and converting DAS output data into distribution data of any local vibration change along the underground pipeline (1);
(j) The automatic monitoring and early warning system (4) processes and analyzes the distribution data of any local temperature change along the underground pipeline (1) in real time, when the underground pipeline (1) is found to have high-temperature abnormality along any local part, a high-resolution optical camera (3) which is monitoring the high-temperature abnormal section of the underground pipeline (1) is adjusted to timely focus and shoot a high-resolution photo or video of the high-temperature abnormal section of the underground pipeline (1) and transmit the high-resolution photo or video back to the automatic monitoring and early warning system (4) for real-time display, and operators on the line monitoring station process or immediately alarm in real time according to the actual condition of the high-temperature abnormal section of the underground pipeline (1);
(k) The automatic monitoring and early warning system (4) processes and analyzes the distribution data of any local vibration change along the underground pipeline (1) in real time, when any local vibration abnormality of the underground pipeline (1) is found, a high-resolution optical camera (3) which is monitoring the vibration abnormality section of the underground pipeline (1) is adjusted to timely focus and shoot a high-resolution photo or video of the vibration abnormality section of the underground pipeline (1) and transmit the high-resolution photo or video back to the automatic monitoring and early warning system (4) for real-time display, and operators on duty of the underground pipeline (1) along the monitoring station process in real time or immediately alarm according to the actual condition of the vibration abnormality section of the underground pipeline (1);
(l) According to the temperature data along the underground pipeline (1) monitored and measured by the DTS system, the formula is utilized:
Δλ/λ=−Δυ/υ=KTΔt+Kεε
wherein lambda and upsilon are average light wavelength and frequency respectively; k T and K ε are temperature and strain standard constants, respectively;
Correcting DSS measured data by using the temperature value of a specific measuring position to carry out drift of scattered light spectrum in the optical fiber caused by temperature change, so as to obtain a real strain value of the outer wall of the underground pipeline (1) without temperature influence;
(m) obtaining the differential of the strain quantity of the outer wall of the underground pipeline (1) monitored and measured in real time for a long time to obtain the change rate of the strain quantity along with the time;
And (n) analyzing the strain quantity and the strain rate of the outer wall of the underground pipeline (1) which are monitored and measured in real time for a long time, and according to the strain quantity and the strain rate threshold standard of the underground pipeline (1) which are set by pipeline engineering, when the local strain quantity and the strain rate of the underground pipeline (1) are found to exceed the threshold value and the local deformation damage section of the underground pipeline (1) is possibly caused, timely giving an early warning or an alarm.
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| CN113484912A (en) * | 2021-08-02 | 2021-10-08 | 中油奥博(成都)科技有限公司 | Shale oil gas optical fiber intelligent geophysical data acquisition system and acquisition method |
| CN113990053B (en) * | 2021-11-11 | 2023-05-30 | 华东桐柏抽水蓄能发电有限责任公司 | Online evaluation system for hydraulic working gate of pumped storage power station |
| TWI810777B (en) * | 2022-01-05 | 2023-08-01 | 國立中央大學 | Stratum deformation monitoring device, system and method |
| CN115950461B (en) * | 2022-11-30 | 2024-04-05 | 无锡布里渊电子科技有限公司 | Building safety monitoring system based on optical fiber sensing technology and monitoring method thereof |
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