超高压输电铁塔结构微形变特征主要受导线挂载产生的应力和环境温度等因素影响, 准确分析微形变周期性变化特征对铁塔结构稳定性评估和安全监测至关重要。该文首先利用国产C波段涪城一号高分辨率合成孔径雷达(synthetic aperture radar, SAR)卫星升降轨时间序列数据, 提取了500 kV超高压输电铁塔整体结构微形变产生的干涉相位变化, 并分析了环境温度和干涉基线等因素对铁塔结构微形变的影响规律; 其次, 提出了输电铁塔永久散射体(permanent scatterer, PS)点仿真和干涉高程相位计算方法, 并基于雷达距离Doppler方程和真实地理坐标系下的输电铁塔三维模型点云数据, 实现了铁塔PS点像元的亚像元级精度定位和干涉高程相位仿真; 最后, 以重庆市渝北区的超高压输电线路为试验对象, 开展了算法验证和铁塔主体结构PS点区域的时序差分干涉相位分析。结果表明: 该文所提铁塔PS点仿真算法生成的散射强度仿真图像与铁塔真实SAR影像纹理吻合良好, 生成的干涉高程相位图谱与真实干涉条纹趋势相同; 布设的4个人工角反射器形变监测精度小于1 mm, 且能为涪城SAR数据提供亚像元级几何定标; 铁塔PS点区域差分干涉结构的小提琴图时序分析结果显示, 存在较多与温度年周期趋势不一致的现象, 可能与导线应力变化等因素相关。该文验证了米级分辨率SAR卫星在输电铁塔结构形变监测中的可行性, 研究结果可为评估地质灾害、地震、台风等诱发的大尺度结构形变提供参考。

Objective: Ultra-high voltage (UHV) transmission towers play an important role in long-distance power delivery, and their safe operation directly affects the stability and resilience of power systems. Under normal conditions, these towers are susceptible to deformation caused by stress induced by conductor suspension as well as geological hazards, extreme weather, etc. Current methods of routine inspection, including human inspection, unmanned aerial vehicle surveys, and in situ sensors, are costly and inefficient. Spaceborne synthetic aperture radar (SAR) provides large-area coverage and millimeter-level deformation sensitivity for landslide hazard assessment around power towers widely used by the State Grid. Methods: This study developed a high-resolution SAR-based approach to accurately extract the small structural deformation trend of UHV transmission towers. A novel SAR imaging intensity simulation and interferometric phase estimation method for transmission towers was developed. This method integrated three-dimensional light detection and ranging (LiDAR)-derived tower point cloud models with the radar range-Doppler equation to simulate the elevation phase of tower structures containing persistent scatterer (PS) points. To address the multiscattering effects and vertical occlusions inherent in lattice steel towers, a weighted sum model was developed for both intensity and phase simulations. Ascending and descending SAR data acquired by the China C-band Fucheng-1 satellite were processed over 8 months. In total, 39 SAR scenes covering two 500 kV transmission lines in Yubei District, Chongqing, were analyzed to conduct algorithm verification. To achieve subpixel accuracy in SAR geocoding, four corner reflectors (CRs) were deployed near a tower, with their positions precisely measured by a global navigation satellite system. After geometric calibration using CRs, the LiDAR point cloud data in the Fucheng-1 SAR imagery achieved a positioning accuracy within ±0.2 pixels, while the interferometric phase for strong scatterers, such as CRs, reached the sub-millimeter level. CR-based analysis further revealed a gradual settlement of approximately 8 mm over 8 months at one reflector site, highlighting the importance of stable benchmarks for long-term deformation monitoring. Results: Simulation experiments demonstrated that the proposed tower imaging model could reproduce key structural features, including the hollow lattice geometry and the scattering contributions of insulator strings. With a resolution of greater than 0.6 m, the simulated area with the power tower PS points showed favorable agreement with the hollow lattice texture of the power tower. Time-series analysis confirmed that PS points located on the tower structures maintained high coherence throughout the observation period, thereby enabling reliable extraction of deformation signals. Based on simulated tower interferometric phases, differential interferometry was performed without height-induced errors. Violin plots were used for statistically characterizing PS point deformation, and comparative analyses between strain-type and straight-type towers revealed structural differences. Comparative results indicated that strain-type towers exhibited a relatively stable condition, whereas time-series results revealed that straight-type towers exhibited more frequent and pronounced small deformation trend events. The correlation between environmental temperature variations and small deformation trends in transmission towers was weak. Interferograms with large temperature differences did not show an obvious trend in power tower structural deformation either. This trend might be influenced by multiple factors, including structural stiffness, insulator configuration, conductor tension, and external loading. Conclusions: This study verifies the feasibility of using high-resolution China C-band SAR satellites to monitor the small structural deformation trend of UHV transmission towers in time series datasets. Future work should incorporate structural temperature variations, power line stress conditions, and wind loads to develop physical mechanism-based models for explaining power tower deformation trends. Ultimately, the methodology presented in this study provides a foundation for analyzing such trends. It can be applied to assess structural stability under extreme events, such as geological hazards, earthquakes, and typhoons across different regions of China.