Power transmission tower vibration deformation measurement and early warning method based on ground-based synthetic aperture radar

Abstract

The power transmission tower vibration deformation measuring and early warning method based on the ground-based synthetic aperture radar comprises the steps that scanning imaging is conducted on a power transmission tower through the ground-based synthetic aperture radar, and a plurality of radar image sequences which cover a target tower body and are arranged according to the time sequence are obtained; processing the plurality of radar image sequences by adopting a permanent scatterer interference measurement method, extracting a plurality of permanent scatterer points attached to the key points of the power transmission tower, and obtaining a displacement time sequence of each permanent scatterer point along the sight line direction of the radar; decomposing the displacement time sequence along the radar sight line direction into deformation component time sequences in three orthogonal directions under a power transmission tower structure coordinate system; joint time-frequency analysis and modal parameter identification are carried out on the deformation component time sequence in each direction, and modal parameters of the power transmission tower are extracted; establishing a multi-level early warning mechanism, calculating the change indexes of the current modal parameter and the deformation component relative to the reference value, and automatically triggering different levels of power transmission tower structure state early warning.

Description

A method for measuring and early warning of vibration deformation of transmission towers based on ground-based synthetic aperture radar Technical Field

[0001] This invention belongs to the field of power transmission line safety monitoring and early warning technology, and relates to a method for measuring and warning of vibration deformation of power transmission towers based on ground-based synthetic aperture radar. Background Technology

[0002] As the backbone structure for power transmission, transmission towers are exposed to complex outdoor environments for extended periods, making them susceptible to vibration and deformation due to external excitations such as wind loads, icing, and earthquakes. Excessive vibration and cumulative deformation can lead to structural fatigue, component loosening, and even overall instability, seriously threatening power grid safety. Therefore, high-precision, continuous dynamic response monitoring and structural condition analysis of transmission towers are crucial.

[0003] Traditional methods for monitoring transmission tower deformation mainly include total station measurement, GPS monitoring, and inclinometer and accelerometer network measurement. Total station measurement offers high accuracy but is a single-point, discrete measurement with low automation and difficulty in capturing high-frequency dynamic responses. GPS enables continuous monitoring, but its accuracy is typically at the centimeter level, insufficient for monitoring minute deformations, and is susceptible to satellite signal blockage. Accelerometers can directly measure vibration, but require numerous sensors to be installed on the tower, leading to difficulties in installation and maintenance, complex power supply and data transmission, and susceptibility to lightning strikes, hindering large-scale deployment.

[0004] Ground-based synthetic aperture radar (SAR) is an emerging active microwave remote sensing technology with advantages such as non-contact, long-range, high precision, and large-area continuous scanning imaging. In recent years, research has applied it to deformation monitoring of bridges, dams, and mountain slopes. However, applying it to tall, flexible, and complex lattice structures like power transmission towers still faces unique challenges: the tower structure is complex, the effective scattering points are discretely distributed, and traditional differential interferometry (D-InSAR) techniques suffer from poor coherence, making it difficult to stably extract phase information. The radar line-of-sight displacement is a one-dimensional projection of the slant range direction, which cannot directly reflect the three-dimensional vibration pattern of the power transmission tower in space. Furthermore, the vibration signals of power transmission towers are typically non-stationary and multimodal, requiring effective separation and identification of modal parameters from the displacement time series.

[0005] Currently, there is a lack of a complete systematic solution for the structural characteristics of transmission towers, based on ground-based synthetic aperture radar, which includes data acquisition, high-precision displacement extraction, three-dimensional deformation decomposition, vibration mode analysis, and ultimately forms a health assessment system with clear quantitative early warning indicators. Summary of the Invention

[0006] To address the aforementioned technical problems, the purpose of this invention is to provide a method for measuring and early warning of vibration deformation of transmission towers based on ground-based synthetic aperture radar.

[0007] This invention provides a method for measuring and early warning of vibration deformation of transmission towers based on ground-based synthetic aperture radar, comprising:

[0008] S1: Continuous scanning imaging of the target transmission tower is performed using ground-based synthetic aperture radar to obtain a sequence of complex radar images covering the target tower in chronological order;

[0009] S2: For complex radar image sequences, the permanent scatterer interferometry method based on the optimization selection of common master image is used to process them, identify and extract multiple permanent scatterer points attached to the tower body, crossarm and ground wire support of the transmission tower, and obtain the displacement time series of each permanent scatterer point along the radar line of sight.

[0010] S3: Based on the three-dimensional structural model of the transmission tower, combined with the phase center position and attitude parameters of the ground-based synthetic aperture radar antenna, the displacement time series along the radar line of sight is decomposed into the deformation component time series in three orthogonal directions under the coordinate system of the transmission tower structure.

[0011] S4: Perform joint time-frequency analysis and modal parameter identification on the time series of deformation components in each direction to extract the modal parameters of the transmission tower;

[0012] S5: Establish a multi-level early warning mechanism, calculate the changes in current modal parameters and deformation components relative to the benchmark value, and automatically trigger early warnings of different levels of transmission tower structural status.

[0013] The present invention provides a method for measuring and early warning of vibration deformation of transmission towers based on ground-based synthetic aperture radar, which has the following beneficial effects:

[0014] 1. Non-contact, long-distance, and safe: The method of this invention does not require the installation of any equipment on the high-voltage transmission tower, and personnel can operate it from a safe area on the ground, thus solving the risk and cost problems of sensor installation and maintenance.

[0015] 2. High precision, full-field measurement: The method of this invention utilizes advanced permanent scatterer interferometry technology, which can achieve sub-millimeter displacement monitoring accuracy and simultaneously acquire displacement information of dozens or even hundreds of points on the tower, realizing full-field monitoring from point to surface.

[0016] 3. Three-dimensional dynamic deformation perception: The method of this invention, by combining the structural model for coordinate transformation, breaks through the limitation of traditional ground-based synthetic aperture radar that can only provide one-dimensional line-of-sight displacement, and realizes synchronous three-dimensional calculation of the horizontal sway, longitudinal sway and vertical buoyancy vibration of the transmission tower.

[0017] 4. In-depth dynamic characteristic analysis: The method of this invention not only measures deformation, but also extracts key modal parameters such as natural frequency, damping ratio, and mode shape, providing data support for the structural health assessment of transmission towers based on dynamic characteristics.

[0018] 5. Continuous monitoring around the clock: Microwave signals are unaffected by light and common weather (rain, fog, snow), enabling 24 / 7 uninterrupted monitoring. They can effectively capture the dynamic response of transmission tower structures under extreme weather conditions (such as strong winds and icing), providing high early warning value.

[0019] 6. Tiered early warning: A three-tiered early warning indicator system based on multi-parameter fusion and quantification has been established, which transforms the complex structural response of transmission towers into intuitive early warning indicators, realizing a closed loop from "monitoring" to "assessment" and then to "early warning", thereby improving the initiative and accuracy of operation and maintenance. Attached Figure Description

[0020] Figure 1 is a flowchart of a method for measuring and early warning of vibration deformation of transmission towers based on ground-based synthetic aperture radar according to the present invention. Detailed Implementation

[0021] As shown in Figure 1, the present invention provides a method for measuring and warning of vibration deformation of transmission towers based on ground-based synthetic aperture radar, comprising:

[0022] S1: Use ground-based synthetic aperture radar to continuously scan and image the target transmission tower, and obtain a complex radar image sequence covering the target tower in chronological order.

[0023] The scanning strategy of ground-based synthetic aperture radar adopts a scanning mode that combines cross-track (vertical baseline) and along-track (time baseline) to optimize the spatial sampling of the three-dimensional structure of the transmission tower and improve the accuracy of subsequent three-dimensional deformation decomposition.

[0024] In practice, a ground-based synthetic aperture radar (GB-SAR) device (such as IBIS-FS) is mounted on a stable foundation approximately 500 meters from the target power transmission tower. Radar scanning parameters are set (scanning angle covering the entire tower, range resolution 0.5m, azimuth resolution 4.5mrad), and continuous scanning is performed at a rate of approximately 30 images per minute for 2 hours to acquire a complex image stack containing time information.

[0025] S2: For complex radar image sequences, a permanent scatterer interferometry method based on optimized selection of common master images is used for processing. Multiple permanent scatterer points attached to the transmission tower body, crossarm, and ground wire support are identified and extracted. The displacement time series of each permanent scatterer point along the radar line of sight is obtained, specifically:

[0026] S21: Select multiple main images from a complex radar image sequence based on the signal-to-noise ratio and spatiotemporal baseline distribution of the radar images.

[0027] In practice, the main image is selected according to the following criteria:

[0028] (1) The signal-to-noise ratio is quantified by calculating the amplitude deviation index or phase stability of the image. Several of the most stable radar images are selected from them, and images with higher signal-to-noise ratios are selected as the main images.

[0029] Images with a high signal-to-noise ratio record strong radar echo signals with low noise. Interferograms generated from these primary images have higher phase quality, can more reliably identify stable permanent scatterers, and provide a solid "anchor point" for the entire network.

[0030] (2) Ensure that the spatial baseline between the master images and the spatial baseline between the master image and the slave image are the shortest, so that the baseline length of most interference pairs in the differential interferogram network is below a critical value.

[0031] For discrete point targets such as transmission towers, the longer the spatial baseline, the more severe the geometric decoherence, the greater the interference phase noise, and even complete failure. Choosing a master image with a short spatial baseline can ensure that the interferogram paired with it has high coherence.

[0032] (3) Ensure that the time baseline between the main images and between the main images and the secondary images are evenly covered throughout the observation period.

[0033] It can avoid temporal decoherence caused by long time intervals; a uniform temporal distribution helps to separate the contributions of different phases such as deformation and atmospheric effects, and improves the accuracy of subsequent inversion.

[0034] S22: For each selected master image, pair it with all other slave images in the time series to form an interference pair. Perform complex conjugate multiplication on each interference pair to generate the corresponding differential interferogram. Combine the differential interferograms generated by all interference pairs into a dense interferogram network.

[0035] S23: Calculate the amplitude deviation index of each pixel in all original complex images, and its temporal coherence coefficient in all differential interferograms, and set the corresponding threshold.

[0036] S24: Perform initial pixel selection based on amplitude deviation index, and select candidate pixels whose amplitude deviation index is greater than the corresponding threshold; then select pixels from the candidate pixels whose temporal coherence coefficient is greater than the corresponding threshold and whose phase is stable in the time series, which are the permanent scattering points on the transmission tower structure.

[0037] S25: Through phase unwrapping and atmospheric phase correction, a high-precision line-of-sight displacement time series of each permanent scatterer point is finally obtained.

[0038] In practice, 20 images with high signal-to-noise ratios were selected as the main image set to generate an interferogram network. Through phase stability analysis, a total of 85 high-quality permanent scatterer points were identified on the tower. After phase unwrapping, atmospheric correction, and time series inversion, the line-of-sight (LOS) displacement time series of each permanent scatterer (PS) point with reference to the first image and a sampling interval of approximately 2 seconds was obtained.

[0039] S3: Based on the three-dimensional structural model of the transmission tower, and combined with the phase center position and attitude parameters of the ground-based synthetic aperture radar antenna, the displacement time series along the radar line of sight is decomposed into deformation component time series in three orthogonal directions under the coordinate system of the transmission tower structure, specifically:

[0040] S31: Based on the three-dimensional structural model of the transmission tower, the three-dimensional spatial coordinates of the permanent scatterer points are obtained by directly assigning values ​​through structural design drawings, by multi-angle observation inversion through ground-based synthetic aperture radar, or by obtaining the three-dimensional spatial coordinates of the permanent scatterer points through a laser scanner.

[0041] S32: Combining the phase center position and attitude parameters of the ground-based synthetic aperture radar antenna, construct a coordinate transformation model for each permanent scatterer point from the radar line-of-sight direction to the coordinate system of the transmission tower structure.

[0042] The coordinate system of the transmission tower structure is defined as follows: with the center of the tower foot as the origin O, the horizontal direction of the transmission line as the X-axis, the vertical direction of the transmission line as the Y-axis, and the vertical upward direction as the Z-axis; the coordinate transformation model is as follows:

[0043]

[0044]

[0045] in, These represent the deformation components of permanent scattering point i in the X, Y, and Z directions in the coordinate system of the transmission tower structure, respectively. Let θ be the line-of-sight displacement of permanent scatterer point i, and let A be the transformation matrix calculated based on radar geometry and the location of the scattering point. Let θ be the radar incident angle, representing the angle between the radar beam and the vertical direction. Let φ be the radar azimuth angle, representing the angle between the projection of the radar beam onto the horizontal plane and the reference direction.

[0046] S33: The coordinate transformation model is approximated by the following linear equation:

[0047]

[0048] in, and These are the radar incident angle and azimuth angle of permanent scatterer point i, respectively.

[0049] S34: Since there are multiple permanent scattering points, an overdetermined set of equations is constructed and solved using the least squares method. The displacement time series of each permanent scattering point along the radar line of sight is decomposed into the deformation component time series in three orthogonal directions under the coordinate system of the transmission tower structure.

[0050] S4: Perform joint time-frequency analysis and modal parameter identification on the time series of deformation components in each direction to extract the modal parameters of the transmission tower, specifically:

[0051] S41: Apply Hilbert-Huang transform or wavelet transform to the time series of deformation components in each direction to obtain their time spectrum, and analyze the time spectrum to obtain the frequency components and their variation with time.

[0052] S42: Using the random subspace identification method or frequency domain decomposition method, the modal parameters of the transmission tower are identified by utilizing the correlation of the responses at multiple measurement points, including the natural frequencies, damping ratios, and corresponding spatial modes.

[0053] S5: Establish a multi-level early warning mechanism, calculate the changes in current modal parameters and deformation components relative to the benchmark value, and automatically trigger early warnings of different levels of transmission tower structural status.

[0054] The modal parameters and deformation components in step S5, relative to the reference values, include the following indices: frequency drift rate. Damping ratio change rate Modal correlation coefficient (MAC) and dynamic deformation amplitude and cumulative static deformation ;

[0055]

[0056] in, For a certain natural frequency currently identified, The historical health baseline value for this frequency order is the long-term monitoring statistical average; the frequency drift rate is used as the metric. It reflects the overall stiffness change of the transmission tower structure.

[0057]

[0058] in, Given the current damping ratio, Historical baseline value; Damping ratio change rate It can reflect changes in the energy dissipation characteristics of the transmission tower structure.

[0059]

[0060] in, To identify the vibration mode, The MAC value is the reference mode shape; the closer it is to 1, the better the consistency. A decrease indicates that changes in the local stiffness of the structure have led to abnormal vibration patterns.

[0061] Dynamic deformation amplitude The value is the vibration envelope amplitude of a key monitoring point on the transmission tower structure at the dominant frequency. The dominant frequency refers to the frequency component with the most concentrated vibration energy identified from the deformation signal through time-frequency analysis.

[0062] The key monitoring points include: the tower top, the middle of the tower body, the ends of the crossarms, and the top of the ground wire support. The tower top, being the most free end of the structure, typically experiences the largest displacement amplitude and directly reflects the overall stiffness. The middle of the tower body, where structural stiffness may change, is prone to significant bending stress and is sensitive to damage. The ends of the crossarms directly bear the conductor tension and experience severe dynamic responses under conditions such as wind deflection and ice shedding. The top of the ground wire support bears the ground wire load and typically has relatively low stiffness, making it susceptible to significant wind-induced vibration.

[0063] Dynamic deformation amplitude It directly reflects the instantaneous response strength of the structure under dynamic loads and is a key indicator for judging whether the structure will experience instantaneous over-limit vibrations, leading to fatigue or instability risks. It directly reflects the response strength of the transmission tower structure under dynamic loads such as wind and ice; exceeding the limit may lead to fatigue or instability.

[0064] Static deformation accumulation The value is the long-term trend displacement after deducting dynamic components from the key points. It reflects permanent deformation caused by foundation settlement, component creep, damage accumulation, etc.

[0065] The cumulative amount of static deformation The method for obtaining the value is as follows: For the three-dimensional deformation component time series of any key point obtained in step S3 (such as the x-direction displacement of the tower top), the long-term trend term is separated using signal processing techniques. Specifically, high-frequency dynamic components caused by wind-induced vibrations can be filtered out using digital high-pass filtering, or the long-term trend in the displacement sequence can be directly fitted using mathematical models (such as polynomial fitting or moving average). The displacement amount of the separated or fitted low-frequency trend term is the accumulated static deformation. It is used to assess permanent deformations caused by foundation settlement, component creep, etc.

[0066] In step 5, a three-level transmission tower status early warning system is established based on change indicators: blue observation-level early warning, yellow attention-level early warning, and red action-level early warning.

[0067] (1) The triggering condition for the blue observation level warning is: the frequency drift rate of the first 3 dominant modes. Within the range of 5% to 10%, or the rate of change of damping ratio It is in the range of 20% to 40%, or the mode shape correlation coefficient (MAC) is in the range of 0.85 to 0.90.

[0068] For blue observation-level warnings, the transmission tower's status is marked as "observation" in the monitoring platform, and the sampling frequency of monitoring data is increased to strengthen data tracking. A status report is generated and saved, indicating "minor anomalies in parameters, close monitoring recommended," and a list of abnormal parameters is attached.

[0069] Manual response recommendations: Data analysts should review monitoring data and reports; compare environmental data (wind speed, wind direction, temperature, icing conditions) with data from the same period to determine whether it is a normal environmental load response; and include it in the observation list for the next regular inspection.

[0070] (2) The triggering condition for a yellow alert is: the frequency drift rate of the first 3 dominant modes. Within the range of 10% to 15%, or the rate of change of damping ratio Or the mode shape correlation coefficient (MAC) is in the range of 0.75 to 0.85.

[0071] For yellow alert level warnings, the status of the transmission tower is marked as "attention" in the monitoring platform, an alarm notification is issued and a special analysis (such as a preliminary damage location algorithm) is initiated; a diagnostic report is generated to conduct a preliminary analysis of possible causes of the anomaly (e.g., "suspected loose connection node in the middle of the tower body", "basin stability needs attention").

[0072] Manual response recommendations: Remote data verification and preliminary diagnosis must be completed within the specified time (e.g., 24 hours); a targeted on-site inspection plan should be developed and implemented, focusing on checking the structural parts corresponding to abnormal parameters; consider adjusting the power grid operation mode to reduce the load on the tower.

[0073] (3) The triggering condition for a red action-level warning is: the frequency drift rate of the first three dominant modes. Or the modal correlation coefficient MAC < 0.75, or the dynamic deformation amplitude Exceeding the design allowable value.

[0074] For red-level action warnings, the status of the transmission tower is marked as "dangerous" in the monitoring platform, and the highest level of audible and visual alarms, alarm SMS and emails are sent to the operation and maintenance manager and safety supervisor; the complete original data and processing results before and after the abnormal moment are automatically locked and backed up; an emergency assessment report is generated, clearly indicating the risk location, possible failure modes and emergency response priorities.

[0075] The following actions must be taken in a manual response: immediately activate the emergency plan; coordinate with the dispatching department to take necessary electrical safety measures for the affected lines (such as load transfer, current limiting, or even emergency power outage); and immediately dispatch a professional maintenance team to the site for emergency investigation and handling.

[0076] In this embodiment, the monitored first-order frequency is 0.45Hz, the historical baseline value is 0.44Hz, and the calculated Δf ≈ 2.3%, which is far below the 5% blue alert threshold. All other indicators are within the normal range. Therefore, the system determines that the tower is currently in a healthy state, generates a "normal status" report, and no alert needs to be triggered.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the ideas of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for measuring and early warning of vibration deformation of transmission towers based on ground-based synthetic aperture radar, characterized in that, include: S1: Continuous scanning imaging of the target transmission tower is performed using ground-based synthetic aperture radar to obtain a sequence of complex radar images covering the target tower in chronological order; S2: For complex radar image sequences, a permanent scatterer interferometry method based on optimized selection of common master images is used to process the data, identify and extract multiple permanent scatterer points attached to the tower body, crossarms, and ground wire supports, and obtain the displacement time series of each permanent scatterer point along the radar line of sight. S3: Based on the three-dimensional structural model of the transmission tower, combined with the phase center position and attitude parameters of the ground-based synthetic aperture radar antenna, the displacement time series along the radar line of sight is decomposed into deformation component time series in three orthogonal directions under the transmission tower structural coordinate system. S4: Joint time-frequency analysis and modal parameter identification are performed on the deformation component time series in each direction to extract the modal parameters of the transmission tower. S5: A multi-level early warning mechanism is established to calculate the changes in the current modal parameters and deformation components relative to the reference values, automatically triggering different levels of transmission tower structural status early warning.

2. The method for measuring and early warning of transmission tower vibration deformation based on ground-based synthetic aperture radar according to claim 1, characterized in that, In step S1, the scanning strategy of the ground-based synthetic aperture radar adopts a scanning mode that combines cross-track and along-track scanning.

3. The method for measuring and early warning of transmission tower vibration deformation based on ground-based synthetic aperture radar according to claim 1, characterized in that, Step S2 specifically comprises: S21: Selecting multiple main images from the complex radar image sequence based on the signal-to-noise ratio and spatiotemporal baseline distribution of the radar images; S22: For each selected main image, pairing it with all other secondary images in the time series to form an interferometric pair, performing complex conjugate multiplication on each interferometric pair to generate a corresponding differential interferogram, and constructing a dense interferogram network from the differential interferograms generated by all interferometric pairs; S23: Calculating the amplitude deviation index of each pixel in all original complex images and its temporal coherence coefficient in all differential interferograms, and setting a corresponding threshold; S24: Performing initial pixel selection based on the amplitude deviation index, selecting candidate pixels with amplitude deviation indices greater than the corresponding threshold; then selecting pixels with temporal coherence coefficients greater than the corresponding threshold and stable phase in the time series from the candidate pixels, which are the permanent scattering points on the transmission tower structure; S25: Through phase unwrapping and atmospheric phase correction, finally retrieving the high-precision line-of-sight displacement time series of each permanent scattering point.

4. The method for measuring and early warning of transmission tower vibration deformation based on ground-based synthetic aperture radar according to claim 3, characterized in that, In step S21, the main image is selected according to the following criteria: (1) The signal-to-noise ratio is quantified by calculating the amplitude deviation index or phase stability of the image, and the most stable radar images are selected as the main images; (2) Ensure that the spatial baseline between the main images and the spatial baseline between the main image and the slave image are the shortest, so that the baseline length of most interference pairs in the differential interferogram network is lower than a critical value; (3) Ensure that the temporal baseline between the main images and the temporal baseline between the main image and the slave image uniformly cover the entire observation period.

5. The method for measuring and early warning of transmission tower vibration deformation based on ground-based synthetic aperture radar according to claim 1, characterized in that, The specific steps of step S3 are as follows: S31: Based on the three-dimensional structural model of the transmission tower, the three-dimensional spatial coordinates of the permanent scatterer points are obtained by directly assigning values ​​through structural design drawings, by multi-angle observation inversion through ground-based synthetic aperture radar, or by laser scanner; S32: Combining the phase center position and attitude parameters of the ground-based synthetic aperture radar antenna, a coordinate transformation model of each permanent scatterer point from the radar line of sight to the coordinate system of the transmission tower structure is constructed. The coordinate system of the transmission tower structure is defined as follows: with the center of the tower foot as the origin O, the horizontal direction of the transmission line as the X-axis, the vertical direction of the transmission line as the Y-axis, and the vertical upward direction as the Z-axis; the coordinate transformation model is as follows: in, These represent the deformation components of permanent scattering point i in the X, Y, and Z directions in the coordinate system of the transmission tower structure, respectively. Let be the line-of-sight displacement of permanent scatterer point i; A is the transformation matrix calculated based on radar geometry and the location of the scattering point; θ is the radar incident angle, representing the angle between the radar beam and the vertical direction; φ is the radar azimuth angle, representing the angle between the projection of the radar beam onto the horizontal plane and the reference direction; S33: The coordinate transformation model is approximated by the following linear equation: in, and S1 and S2 are the radar incident angle and azimuth angle of permanent scatterer point i, respectively; S34: Since there are multiple permanent scatterer points, an overdetermined set of equations is constructed and solved using the least squares method. The displacement time series of each permanent scatterer point along the radar line of sight is decomposed into the deformation component time series of three orthogonal directions in the coordinate system of the transmission tower structure.

6. The method for measuring and early warning of transmission tower vibration deformation based on ground-based synthetic aperture radar according to claim 1, characterized in that, The specific steps of step S4 are as follows: S41: Apply Hilbert-Huang transform or wavelet transform to the time series of deformation components in each direction to obtain their time spectrum, and analyze the time spectrum to obtain the frequency components and their time variation law; S42: Use the random subspace identification method or frequency domain decomposition method to identify the modal parameters of the transmission tower by utilizing the correlation of the multi-measurement point response, including the natural frequencies, damping ratios and corresponding spatial vibration modes of each order.

7. The method for measuring and early warning of transmission tower vibration deformation based on ground-based synthetic aperture radar according to claim 1, characterized in that, The changes in modal parameters and deformation components relative to the reference value in step S5 include: frequency drift rate. Damping ratio change rate Modal correlation coefficient (MAC) and dynamic deformation amplitude and cumulative static deformation ； in, For a certain natural frequency currently identified, The historical health baseline value for this frequency level is the long-term monitoring statistical mean. in, Given the current damping ratio, This is the historical baseline value; in, To identify the vibration mode, The reference mode shape; the closer the MAC value is to 1, the better the consistency; dynamic deformation amplitude. The value is the vibration envelope amplitude at the dominant frequency of key monitoring points on the transmission tower structure; the key monitoring points include: the top of the tower, the middle of the tower body, the end of the crossarm, and the top of the ground wire support; the dominant frequency refers to the frequency component with the most concentrated vibration energy identified from the deformation signal through time-frequency analysis; the cumulative static deformation is also considered. The value is the displacement of the long-term trend term after deducting the dynamic components from the key points.

8. The method for measuring and early warning of transmission tower vibration deformation based on ground-based synthetic aperture radar according to claim 7, characterized in that, In step 5, a three-level transmission tower status early warning system is established based on change indicators: blue observation level early warning, yellow attention level early warning, and red action level early warning. The trigger condition for the blue observation level early warning is the frequency drift rate of the first three dominant modes. Within the range of 5% to 10%, or the rate of change of damping ratio If the frequency shift rate is between 20% and 40%, or the modal correlation coefficient (MAC) is between 0.85 and 0.90; the trigger condition for a yellow alert level is: the frequency shift rate of the first three dominant modes. Within the range of 10% to 15%, or the rate of change of damping ratio Or the mode shape correlation coefficient (MAC) is in the range of 0.75 to 0.85; the trigger condition for a red action-level warning is: the frequency drift rate of the first 3 dominant modes. Or the modal correlation coefficient MAC < 0.75, or the dynamic deformation amplitude Exceeding the design allowable value.

9. The method for measuring and early warning of transmission tower vibration deformation based on ground-based synthetic aperture radar according to claim 8, characterized in that, When different levels of transmission tower status warnings are triggered in step 5, the following operations are performed: For the blue observation level warning, the status of the transmission tower is marked as "observation", and the sampling frequency of monitoring data is increased to strengthen data tracking; for the yellow attention level warning, the status of the transmission tower is marked as "attention", an alarm notification is issued and a special analysis is initiated; for the red action level warning, the status of the transmission tower is marked as "danger", the highest level audible and visual alarm is issued, emergency alarm information is pushed, and abnormal data is locked.

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