In power system operation and maintenance, the safety monitoring of transmission lines has always been a major challenge. Traditional manual inspections are inefficient and risky, while drone-based optical inspections are often limited by weather and lighting conditions. Now, a cutting-edge technology originating from aerospace remote sensing—airborne synthetic aperture radar (SAR)—is bringing revolutionary changes to the monitoring of potential hazards in transmission lines.
I. A "Health Checkup" for Transmission Lines: Why is SAR Needed?
Transmission lines are exposed to the natural environment year-round, facing multiple safety hazards:
• Ground subsidence: Leading to instability in tower foundations
• Landslides: Threatening the safety of the transmission line corridor
• Tree growth: Potentially causing short-circuit accidents
• Equipment aging: Affecting power supply reliability
II. Core Principles: How Does SAR "Diagnose" Transmission Lines?
2.1 The "Virtual Megalens" of Synthetic Aperture
The core of SAR technology lies in the principle of "synthetic aperture":
• The aircraft continuously transmits microwave signals during flight.
• Through signal processing technology, the echoes from multiple small antennas are "synthesized" into the effect of a large antenna.
• Achieving high-resolution imaging with centimeter-level accuracy.
2.2 The "Millimeter-Scale Ruler" of Differential Interferometry (D-InSAR)
This is the core technology of SAR for monitoring surface deformation:
• Imaging the same area multiple times at different times.
• By comparing phase differences, precisely measuring minute changes on the surface at the millimeter level.
• Like using a precise ruler to measure whether the foundation of an iron tower has settled.
2.3 The "Multi-Dimensional Perspective" of Polarization Technology
Fully polarimetric SAR can acquire four polarization types: HH, HV, VV, and VH:
• Different ground features respond differently to different polarization modes.
• It can more accurately distinguish vegetation, buildings, and exposed surfaces.
• It provides multi-dimensional data support for identifying safety hazards within power line corridors.
III. Practical Applications: Hard Verification of SAR Technology
In real power grid operation and maintenance, airborne SAR inspections are gradually replacing and participating in existing power line inspection methods.
Current Power Line Inspection Methods:
Currently, mainstream power line inspection methods include manual inspection, UAV optical inspection, helicopter inspection, and satellite remote sensing monitoring, etc. Manual inspections rely on on-site verification by personnel, which is inefficient and difficult to cover complex terrain. Unmanned aerial vehicle (UAV) optical inspections collect line information using visible light and infrared sensors, but are limited by weather and vegetation obstructions, unable to penetrate clouds or dense canopies. Furthermore, to obtain high-definition images, UAVs operate at close range, resulting in a small coverage area and low efficiency. Helicopter inspections are suitable for large-scale, rapid inspections, but are costly and have limited flight capabilities. Satellite remote sensing can monitor large-area surface changes, but its spatial resolution and revisit frequency are insufficient for detailed monitoring needs.
In comparison, what are the advantages of airborne SAR?
Airborne SAR uses microwaves as its detection method, possessing all-weather, all-time imaging capabilities. It can penetrate clouds, vegetation, and even shallow surfaces, and is unaffected by lighting and weather conditions. Compared to traditional methods, it can accurately capture millimeter-level surface deformation, penetrate dense vegetation to locate guide wires, and quickly identify minute defects in equipment. It also has a wide coverage area and rich data dimensions (such as polarization information and phase information). Meanwhile, small drones such as Keweitai, Zongheng, and DJI fly at altitudes of over 300 meters, far away from power towers and power lines, so they will not damage the power lines. Furthermore, the resolution of SAR imaging is not affected by distance.
3.1 Surface Deformation Monitoring
Pain Point: Transmission towers are often located in areas of frequent geological activity. Slow subsidence (e.g., a few millimeters per year), imperceptible to the naked eye, can easily lead to tower collapse and power line breakage.
Advantages of Airborne SAR: Airborne SAR relies on Synthetic Aperture Radar Interferometry (InSAR) technology. Utilizing the phase difference information from multi-temporal SAR images, it can achieve millimeter-level or even sub-millimeter-level accuracy in monitoring surface deformation.
3.2 Vegetation Intrusion Monitoring
Pain Point: Traditional optical methods struggle to penetrate dense vegetation to clearly see power lines.
Advantages of Airborne SAR: Airborne SAR employs multi-polarization (e.g., fully polarized, dual-polarized) microwave imaging technology. Utilizing the differences in scattering characteristics between vegetation and power lines under different polarization modes, it can penetrate dense canopy layers, achieving accurate inversion of power line location and vegetation height. This overcomes the bottlenecks of traditional optical remote sensing, limited by vegetation obstruction and lighting conditions.
3.3 Equipment Status Monitoring
Pain Point: Rapidly locating minute missing components (such as cotter pins and vibration dampers) along vast power lines is a major challenge.
Advantages of Airborne SAR: Airborne SAR systems integrate high-resolution imaging (down to sub-meter level) with target detection algorithms (such as YOLO and Faster R-CNN based on deep learning), enabling high-precision imaging and feature extraction of minute components (such as cotter pins, vibration dampers, and insulators) on power transmission lines. By establishing a feature library for these components, and then using a series of methods combined with artificial intelligence for automatic identification and classification, the system can be effectively utilized.
IV. Relevant Application Cases from Our Company
Our miniature SAR system, mounted on a multi-rotor UAV, has been used for field tests in typical power corridor areas such as Kunshan Zhouzhuang, Hebei, Beijing, and Henan. It employs a dual-frequency modulated continuous wave radar in the X-band (8-12GHz) and Ka-band (26.5-40GHz) bands, supporting single-polarization (e.g., VV) and full-polarization (e.g., HH/HV/VH/VV) imaging modes. Based on high-resolution SAR images, it is possible to accurately identify changes in the shape of power lines (such as sag shift and broken strands), structural features of power towers (tower base settlement and tower tilt), and intrusion of surrounding foreign objects (such as construction machinery and hanging objects), providing centimeter-level precision all-weather monitoring data for the safe operation and maintenance of transmission lines.
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Single polarization monitoring results |
Full polarization monitoring results |
V. Airborne Miniature SAR System
Suzhou Tianjing Yunhu Intelligent Technology Co., Ltd. (hereinafter referred to as Tianjing Yunhu) is committed to becoming a leading global provider of synthetic aperture radar (SAR) solutions, offering users customized radar equipment, SAR data acquisition services, and radar data products. Leveraging years of R&D experience and professional technical accumulation, Tianjing Yunhu has launched SAR products with multiple bands and various capabilities, including frequency-modulated continuous wave (FM) and pulse systems. Currently, Tianjing Yunhu has coverage across multiple bands, including X, Ku, K, Ka, C, W, and L, and its product systems support single-polarization, full-polarization, strip, spotlight, interferometric, and single-pulse search modes. The products feature real-time imaging, GMTI, and deformation monitoring functions. Tianjing Yunhu SAR products can be mounted on multi-rotor/fixed-wing UAVs, manned aircraft, satellites, and vehicle-mounted platforms.
