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.
