CN111442788A - Health monitoring method and system for overhead transmission line - Google Patents
Health monitoring method and system for overhead transmission line Download PDFInfo
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Abstract
A method for realizing the health monitoring of an overhead transmission line based on a phase-sensitive optical time domain reflectometer and a multi-core optical fiber uses the phase-sensitive optical time domain reflectometer phi-OTDR as a sensor, uses a multi-core optical fiber MCF as a signal transmission medium and a sensitive element of a system at the same time and follows the overhead transmission line; performing segmented interception on the Rayleigh scattering curve obtained by each detection pulse, namely performing segmented interception on optical signals of a plurality of cores acquired by the system, and extracting all strain values required by shape reconstruction at one time by using a data analysis system for phi-OTDR detection; and (3) calculating the curvature radius of the multi-core optical fiber in the shape change area according to a geometric method for describing a space curve, and obtaining each characteristic value of the shape reconstruction by solving a Frenet-Serret ordinary differential equation, namely determining the bending degree and the torsion degree of the cable to be measured. The comprehensive and real-time health monitoring of the waving change rule of the overhead transmission line is realized.
Description
Technical Field
The invention relates to a method and a system for health monitoring of an overhead transmission line, in particular to a sensing method and a sensing system for comprehensively monitoring information such as amplitude, frequency and galloping track of galloping based on a distributed optical fiber sensing technology, and belongs to the field of smart power grids.
Background
The high-voltage overhead transmission line is a main mode adopted by power transmission in China, but in the operation process, galloping disasters can be caused due to the action of natural weather such as wind, rain, snow and the like, the galloping easily causes the phenomena of conductor whip and arc burning or wire and strand breakage, and also easily causes severe abrasion, fracture and falling of hardware fittings, or the phenomena that insulator steel feet are fractured, and a tower is toppled to cause line tripping and other multiple faults.
Therefore, it is very necessary to monitor and warn the galloping in real time and to enable the plan to avoid economic loss. At present, the galloping monitoring mainly depends on technologies such as a video image method, an acceleration sensor, a grating sensor, a distributed sensor based on a single-core optical fiber and the like. The definition of an image acquired by a video image method is limited, and the output two-dimensional information is difficult to truly reflect the three-dimensional waving condition of a wire and is easily influenced by weather such as rain, snow and the like; the acceleration sensor can quantitatively analyze the conditions of up-and-down vibration and left-and-right swinging of a certain point of the power transmission line, but can only measure the amplitude and frequency of linear motion of a lead, the amplitude and frequency cannot be accurately measured for complex circular motion, and the lead is easy to loosen or even fall off when galloping is severe, so that unpredictable noise is increased, and the measured galloping track is seriously distorted; in addition, the above two technologies have limited power supply for long-term outdoor work. At present, a Grating (FBG) sensor can only carry out quantitative measurement on the wire galloping frequency and intensity, and the wire galloping track is difficult to estimate by using the strain variation of the FBG. The distributed sensor based on the single-core optical fiber is similar to the FBG technology, can only realize the measurement of the change frequency and the change intensity of conductor galloping, and cannot realize the monitoring of the space torsion and the longitudinal fluctuation wavelength of the conductor galloping.
The above techniques all have disadvantages in the galloping monitoring, so that a more comprehensive, accurate, continuous and reliable galloping monitoring technique is needed. The invention provides a fully distributed sensing technology which adopts a Phase Optical Time Domain reflectometry (phi-OTDR) to realize the comprehensive monitoring of galloping information in combination with a Multi-Core Fiber (MCF) and can monitor shape information of all points along the whole Optical Fiber.
The phi-OTDR can be regarded as a mobile interference type disturbance/vibration sensor to detect external signals in a sensing optical fiber, disturbance/vibration can cause linear change of interference optical phase at corresponding positions, interference signals at different moments of the positions are extracted and demodulated, signals such as disturbance/vibration and the like are detected by utilizing the phase of coherent Rayleigh scattering light instead of light intensity, the disturbance/vibration event intensity information can be provided by utilizing the phase change, quantitative acquisition of the disturbance/vibration event phase, frequency and position information can be realized by utilizing linear quantitative measurement values, and quantitative measurement of external physical quantities is realized. In addition, the vibration/disturbance frequency measurement range of the phi-OTDR technology is up to the kHz magnitude, dynamic strain can be measured quickly, quantitatively and accurately, safety early warning monitoring for a distance of 100 kilometers can be provided under the condition that power supply is not needed, and the phi-OTDR technology is particularly suitable for safety early warning of overhead transmission lines, high in warning sensitivity and accurate in positioning.
At present, the phi-OTDR is generally applied in the field of single-core optical fiber sensing, but the shape sensing cannot be realized only by the existing phi-OTDR scheme; the invention utilizes phi-OTDR combined with MCF suitable for shape monitoring to be very suitable for measuring the change track of the galloping of the overhead line, breaks through the defects of the existing galloping monitoring technology, can comprehensively obtain the track of the galloping of the line on the basis of obtaining information such as galloping frequency, amplitude and the like, comprehensively obtains the galloping information of the overhead transmission line, and provides a reliable technical scheme for the comprehensive monitoring of the galloping of the long-distance overhead transmission line.
Disclosure of Invention
The invention aims to provide a health monitoring scheme of an overhead transmission line based on a Phase Optical time domain reflectometer (phi-OTDR) and a Multi-Core Fiber (MCF), and simultaneously, a galloping mode recognition artificial neural network model based on deep learning is constructed, so that a new technology for comprehensively, continuously and reliably monitoring the overhead transmission line is realized.
The purpose of the invention is realized as follows: a system for realizing the galloping monitoring of an overhead transmission line based on a phase-sensitive optical time domain reflectometer and a multi-core optical fiber comprises the phase-sensitive optical time domain reflectometer (phi-OTDR), a fan-in, the multi-core optical fiber (MCF) and a fan-out; in the galloping monitoring system, the phi-OTDR comprises a detection pulse transmitter and a signal receiver, and the MCF is simultaneously used as a signal transmission medium and a sensitive element of the phi-OTDR and follows an overhead transmission line, so that the galloping information of the overhead transmission line is comprehensively monitored; the detection signal of the phi-OTDR enters the MCF through a signal output port by fan-in, and a backward Rayleigh scattering signal generated in the MCF is received by the phi-OTDR; the rayleigh scatter signal (curve) obtained for each probe pulse includes strain information from multiple cores in the MCF.
The multi-core optical fiber can be a seven-core optical fiber, a four-core optical fiber or a three-core optical fiber; and a fan-shaped included angle formed by every two core-shifting optical fibers for shape sensing in the multi-core optical fiber and the circle center is 120 degrees.
The system light path connection mode is as follows: the detection signal output port of phi-OTDR is connected with one input end of a fan-in, the output end of the fan-in is connected with one end of an MCF, the other end of the MCF is connected with a fan-out, and three cores or four cores in the MCF are connected end to end in an S shape; each core in the MCF is coupled and led out by using a fan-in device and a fan-out device, three or four cores are connected in an S shape from head to tail, and then the MCF connected in the S shape is accessed into a system, so that a phi-OTDR system can obtain all strain results required by shape reconstruction at one time; using a phi-OTDR system to detect strain values along each core in the MCF in a distributed manner, and realizing the shape reconstruction of the object to be detected; the sensing system monitors strain information of the MCF by using the phi-OTDR, and extracts positions of optical fibers corresponding to the strain information respectively to obtain deformation information corresponding to each core.
And (2) carrying out segmented interception on the Rayleigh scattering curve obtained by each detection pulse (namely carrying out segmented interception on optical signals of a plurality of cores acquired by the system), and extracting all strain values required by shape reconstruction at one time by using a data analysis system of phi-OTDR. And obtaining the galloping track of the power transmission line by combining a shape reconstruction algorithm. The required strain value of the shape reconstruction can accurately calculate the curvature radius of the MCF shape change area according to a geometric method for describing a space curve, each characteristic value of the shape reconstruction, the curvature radius, a tangent vector, a normal vector and a secondary normal vector are obtained by solving a Frenet-Serret ordinary differential equation, and the torsion value of the MCF is obtained approximately, so that the three-dimensional shape of the MCF can be reconstructed according to the parameters. General data analysis for phi-OTDR has matured.
The three-dimensional shape reconstruction can also be realized by using other reconstruction schemes of mathematics and technical schemes; the three-dimensional shape reconstruction characteristic value is combined with parameters such as environment parameters temperature, humidity, wind power and wind direction to construct an artificial neural network for monitoring the galloping of the overhead transmission line, the artificial neural network is suitable for the galloping mode identification of the overhead transmission line based on deep learning training, the three-dimensional shape reconstruction characteristic value and the parameters convenient for the galloping mode identification are selected and used as input vectors of the galloping mode identification neural network of the overhead transmission line, and the parameters include but are not limited to: temperature, humidity, wind power, curvature of a wire, wire blocking distance, tower top displacement, wire torsion angle, tangent vector, normal vector and secondary normal vector of the wire and the like; the output vector of the neural network comprehensively contains the frequency, amplitude, initial phase, shape and vibration type of the waving, and the waving information is comprehensively obtained.
Further, a neural network model for rapidly identifying the galloping mode of the overhead transmission line is trained according to the existing environmental parameters, shape characteristic values and the like, and the galloping mode of the overhead transmission line is identified. So as to realize rapid and accurate galloping monitoring.
Further, when the system monitors the overhead transmission line, the system works in a continuous real-time monitoring state. The system can continuously monitor the galloping of the overhead transmission line, and can also realize the real-time monitoring of ice coating, vibration interference, climbing of people or animals and the like
The invention provides a method for realizing the galloping monitoring of an overhead transmission line based on phi-OTDR and MCF, which uses the phi-OTDR as a signal transmitting, receiving and processing system, and uses the MCF as a signal transmission medium and a sensitive element of the system at the same time and follows the overhead transmission line; the monitoring method and the monitoring system can realize comprehensive and real-time monitoring of the galloping frequency, the galloping amplitude, the galloping track and the galloping change rule of the overhead transmission line.
Furthermore, the invention carries out sectional interception on the Rayleigh scattering curve obtained by each detection pulse, namely, carries out sectional interception on the optical signals of a plurality of cores acquired by the system, and uses a data analysis system for phi-OTDR detection to extract all strain values required by shape reconstruction at one time; obtaining the galloping track of the power transmission line by combining a shape reconstruction algorithm; the required strain value of the shape reconstruction is calculated according to a geometric method for describing a space curve, the curvature radius of a region of the multicore fiber with the shape change is calculated, each characteristic value of the shape reconstruction is obtained by solving Frenet-Serret ordinary differential equation, the curvature radius, the tangent vector, the normal vector and the minor normal vector are approximate to obtain the torsion value of the MCF, and the three-dimensional shape of the MCF can be reconstructed according to the parameter reconstruction.
By adopting the technical scheme, the invention can produce the following beneficial effects: in the aspect of realizing the health monitoring of the overhead transmission line, the invention can accurately reconstruct the three-dimensional shape of the line galloping and comprehensively master the problem of galloping information, and can realize functions (such as ice coating, vibration interference, climbing of people or animals and the like) which can be realized by the traditional sensing system besides the galloping monitoring. Besides the phi-OTDR provided by the invention, the sensing system can also be used in other various distributed optical fiber sensing systems, such as a distributed optical fiber sensing system based on Brillouin scattering, an optical frequency domain analyzer and the like, so that the measurement accuracy of various physical quantity measurement of the waving amplitude, the waving frequency and the waving track can be realized. The realization of the invention is expected to develop a new method and a system for monitoring the health of the overhead transmission line, and further development of the smart grid is promoted.
Drawings
FIG. 1 is a schematic diagram of the arrangement and force-bearing of the cores within a seven-core MCF with respect to the neutral axis;
FIG. 2 is a schematic view of an internal 4-core S-shaped connection of an MCF;
FIG. 3 is a schematic diagram of a Rayleigh scattering curve of the MCF output;
FIG. 4 is a schematic view of a Rayleigh scattering curve for each core after segmentation;
FIG. 5 is a graphical illustration of strain information along each core;
FIG. 6 is a schematic representation of a reconstructed three-dimensional shape;
FIG. 7 a dance pattern recognition neural network;
Fig. 8 is a schematic diagram of an overhead transmission line galloping monitoring system.
Detailed Description
For a more clear and clear description of the present invention, the following description will be made by taking a phi-OTDR sensing system in combination with a seven-core optical fiber as an example, and the optical fiber sensing system that can be used in the present invention is not limited to the phi-OTDR system and the seven-core optical fiber, and the preferred embodiments of the present invention will be described with reference to the attached drawings.
FIG. 1 is a schematic structural view of a seven-core optical fiber used in a preferred embodiment of the present invention;
The system structure of the invention is shown in figure 2, and comprises a phi-OTDR system (1), a Fan-in (2), a multi-core fiber (3) and a Fan-out (4);
The invention uses fan-in and fan-out to respectively lead out seven cores in the MCF, uses four cores in the seven-core optical fiber, namely the core 2, the core 3, the core 4 and the core 7, or the core 1, the core 4, the core 5 and the core 6, to connect the four cores end to end through the fan-in and fan-out to form S-shaped connection. FIG. 2 is an example of a core 2, a core 3, a core 4 and a core 7, wherein four cores are led out through fan-in and fan-out and are connected end to end in an S shape; the seven-core optical fiber as a signal transmission medium and a sensitive element can be used as a core of the optical fiber composite overhead ground wire in a cable system or specially laid.
The specific implementation steps of the invention when used for sensing are as follows:
The system optical path connection mode is as follows: an input end of a detection signal port Fan-in (2) of a phi-OTDR system (1), an output end of the Fan-in (2) is connected with a multi-core optical fiber (3), a multi-core optical fiber (3) is connected with a Fan-out (4), and a core 2, a core 3, a core 4 and a core 7 in the multi-core optical fiber (3) are used as an example to connect four cores in an S shape, as shown in figure 2.
The sensing process comprises the following steps:
Step 1, a detection optical signal enters a core 2, a core 3, a core 4 and a core 7 of a multi-core optical fiber (3) through Fan-in (2), and a generated Rayleigh scattering signal is received by phi-OTDR;
And 3, intercepting the Rayleigh scattering signals in a segmented manner, and extracting all strain values required by shape reconstruction at one time by using a data analysis system of phi-OTDR as shown in figure 4, and extracting all strain values required by shape reconstruction at one time as shown in figure 5.
To calculate the curvature radius, a local coordinate system is first defined to calculate θ iThe values of (a) are shown in the example of fig. 1, which shows a 7-core fiber cross-sectional structure distribution, a 7-core fiber bending axis and a neutral axis thereof. In the example of fig. 1 in which core 3 is under tension and cores 2 and 7 are under compression, the relationship between the radius of curvature resulting from stress applied to the cross section and the strain value of each core can be given by the expressions (1), (2):
R＝r2/2,4＝r3/3,4(1)
R＝r2/2,4＝r7/7,4(2)
Wherein R is the bending radius, R 2、r3、r7Respectively the distances of core 2, core 3, core 7 to the neutral axis, 2,4、3,4、7,4The strain differences of core 2, core 3, core 7 and core 4, respectively. According to r in FIG. 1 2、r3、r7Trigonometric function relationship with r, and θ 2、θ3、θ7The phase relation of 2 pi/3 of phase difference between the included angles can be calculated 2、r3、r7The value of (c). Finally, r is added 2、r3、r7The curve radius of the MCF shape change area can be accurately calculated by substituting in the formulas (1) and (2), and the bending degree of the measured object can be determined. The shape reconstruction feature value is obtained by solving the Frenet-Serret ordinary differential equation (3)). Assume initial conditions (T) 0，N0，B0，R0) Wherein T is a unit tangent vector, N is a unit normal vector, B is a unit minor normal vector, R is a curvature radius, kappa is the curvature of the curve, and tau is the flexibility of the curve. According to the key parameters, the MCF torsion value can be obtained, and the shape of the line to be measured is obtained by using a three-dimensional shape reconstruction algorithm, and a schematic shape diagram is shown in fig. 6.
And 5, selecting typical parameters convenient for the galloping mode identification as input vectors of the neural network by using an artificial neural network facing the galloping monitoring of the overhead transmission line, wherein the parameters comprise: temperature, humidity, wind power, curvature of the wire, wire pitch, tower top displacement, wire torsion angle, tangent vector, normal vector and secondary normal vector of the wire, and the like. According to the purpose of the overall monitoring of the line galloping, the output vector of the line galloping monitoring system is the frequency, the amplitude, the initial phase, the shape and the vibration type of the line galloping, namely the overall information of the galloping.
And 6, when the system monitors the overhead transmission line, the system is in a continuous real-time monitoring state. The system can continuously monitor the galloping of the overhead transmission line and can also realize the real-time monitoring of icing and vibration interference.
An application site schematic diagram for realizing the galloping monitoring of the overhead transmission line based on the phi-OTDR fusion MCF is shown in FIG. 8.
A neural network model for rapidly identifying the galloping mode of the overhead transmission line is trained according to existing environmental parameters, shape characteristic values and the like, and the method for identifying the galloping mode of the overhead transmission line can refer to the prior art [1, witch crystal, application of the neural network in a transmission line galloping monitoring and diagnosis system [ J ]. North China power technology, 1998(09):3-5+44.2, a crack shape inversion method [ P ], CN201010022673.9, Shanghai engineering technology university, 2010 ].
The above embodiments are only preferred embodiments of the present invention, but the scope of the present invention is not limited to the above embodiments, and any modifications and partial substitutions within the knowledge of those skilled in the art without departing from the spirit and scope of the present invention should be covered by the scope of the present invention.
Claims (7)
1. A method for realizing the health monitoring of an overhead transmission line based on a phase-sensitive optical time domain reflectometer and a multi-core optical fiber is characterized in that the phase-sensitive optical time domain reflectometer phi-OTDR is used as a sensor, and a multi-core optical fiber MCF is simultaneously used as a signal transmission medium and a sensitive element of a system and follows the overhead transmission line; the comprehensive and real-time health monitoring of the galloping frequency, the galloping amplitude, the galloping track and the galloping change rule of the overhead transmission line is realized.
2. The method for realizing the health monitoring of the overhead transmission line based on the phase-sensitive optical time domain reflectometer and the multi-core optical fiber according to claim 1, wherein the rayleigh scattering curve obtained by each detection pulse is segmented, that is, the optical signals of a plurality of cores acquired by the system are segmented, and a data analysis system for phi-OTDR detection is used for extracting all strain values required for shape reconstruction at one time; the curvature radius of the multi-core optical fiber in the shape change area is calculated according to a geometric method for describing a space curve, all characteristic values of shape reconstruction, the curvature radius, a tangent vector, a normal vector and a secondary normal vector are obtained by solving a Frenet-Serret ordinary differential equation, and the torsion value of the optical fiber is obtained, namely the bending degree and the torsion degree of the cable to be measured can be determined.
3. A system for realizing the health monitoring of an overhead transmission line based on a phase-sensitive optical time domain reflectometer and a multi-core fiber is characterized in that the galloping monitoring system of the overhead transmission line comprises the phase-sensitive optical time domain reflectometer phi-OTDR, a fan-in, the multi-core fiber MCF and a fan-out; in the galloping monitoring system, the phi-OTDR comprises a detection pulse transmitter and a signal receiver, and the MCF is simultaneously used as a signal transmission medium and a sensitive element of the phi-OTDR and follows an overhead transmission line, so that the galloping information of the overhead transmission line is comprehensively monitored; the detection signal output port of the phi-OTDR is connected with the input end of the fan-in, the output end of the fan-in is connected with one end of the MCF, the other end of the MCF is connected with the fan-out, and three cores or four cores in the MCF are sequentially connected with the corresponding lead-out ports of the fan-out device end to form S-shaped connection; the generated backward Rayleigh scattering signal in the MCF is received by the phi-OTDR; the rayleigh scatter signal obtained from each probe pulse includes strain information from multiple cores in the MCF.
4. The system of claim 3, wherein the multi-core fiber uses a seven-core fiber, a four-core fiber, a three-core fiber; and a fan-shaped included angle formed by every two core-shifting optical fibers for shape sensing in the multi-core optical fiber and the circle center is 120 degrees.
5. The system of claim 3, wherein the system optical path is connected in a manner that: the detection signal output port of the phase-sensitive optical time domain reflectometer is connected with one input end of the fan-in, the output end of the fan-in is connected with one end of the multi-core optical fiber, the other end of the multi-core optical fiber is connected with the fan-out, and three cores or four cores in the multi-core optical fiber are connected end to end in an S shape one by one; each core in the multi-core optical fiber is coupled and led out of each core in the multi-core optical fiber by using a fan-in device and a fan-out device, three or four cores in the multi-core optical fiber are connected in an S shape from head to tail, and then the MCF connected in the S shape is accessed into a system, so that a phi-OTDR system can obtain all strain results required by shape reconstruction at one time; using a phi-OTDR system to detect strain values along each core in the MCF in a distributed manner, and realizing the shape reconstruction of the object to be detected; the sensing system monitors strain information of the multi-core optical fiber by using the phi-OTDR, and respectively extracts positions of the optical fibers corresponding to the strain information to obtain deformation information corresponding to each section of MCF.
6. The system of claim 3, wherein the system operates in a continuous real-time monitoring mode while monitoring the overhead transmission line. The system can continuously monitor the galloping of the overhead transmission line and also realize the real-time monitoring of icing and vibration interference.
7. The system of claim 3, wherein the galloping data analysis uses an artificial neural network oriented to the galloping monitoring of the overhead transmission line, and the shape reconstruction characteristic values, including curvature of the conductor, conductor step distance, tower top displacement, conductor torsion angle, tangent vector, normal vector and sub-normal vector of the conductor, are combined with environmental parameters, namely temperature, humidity, wind power and wind direction, as input vectors of the galloping pattern recognition neural network of the overhead transmission line; the output vector of the neural network comprehensively contains the frequency, amplitude, initial phase, shape and vibration type of the galloping, and the galloping information of the overhead transmission line is comprehensively obtained.
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