Abstract
When the distance between an obstacle and a power line is less than the discharge distance, a discharge arc can be generated, resulting in the interruption of power supplies. Therefore, regular safety inspections are necessary to ensure the safe operation of power grids. Tall vegetation and buildings are the key factors threatening the safe operation of extra high voltage transmission lines within a power line corridor. Manual or laser intensity direction and ranging (LiDAR) based inspections are time consuming and expensive. To make safety inspections more efficient and flexible, a low-altitude unmanned aerial vehicle (UAV) remote-sensing platform, equipped with an optical digital camera, was used to inspect power line corridors. We propose a semi-patch matching algorithm based on epipolar constraints, using both the correlation coefficient (CC) and the shape of its curve to extract three dimensional (3D) point clouds for a power line corridor. We use a stereo image pair from inter-strip to improve power line measurement accuracy by transforming the power line direction to an approximately perpendicular to epipolar line. The distance between the power lines and the 3D point cloud is taken as a criterion for locating obstacles within the power line corridor automatically. Experimental results show that our proposed method is a reliable, cost effective, and applicable way for practical power line inspection and can locate obstacles within the power line corridor with accuracy better than ±0.5 m.
Highlights
The expansion of the 500 kV extra high voltage (EHV) transmission line system for inter-provincial and large-span area power-supply tasks is presently a major project underway in China
A fixed wing unmanned aerial vehicle (UAV) with a Nikon D810 camera was adopted for low-altitude photography of the power line corridor; images were shot from a fix distanced
We focused on solving three problems; 3D reconstruction of the ground surface of the power line corridor, measurement of the power line, and automatic recognition of obstacles
Summary
The expansion of the 500 kV extra high voltage (EHV) transmission line system for inter-provincial and large-span area power-supply tasks is presently a major project underway in China. Existing research shows that airborne LiDAR point clouds yield more accurate and less subjective inspection results than manual inspection [2], expensive airborne LiDAR systems have high maintenance costs [3] in practical operation This seriously restricts the application and popularization of this method. Semi patch matching based on epipolar constraints (SPMEC) was proposed to extract the dense point clouds for the 3D reconstruction of ground objects in a power line corridor. It adapts to ground conditions with dense vegetation and can successfully extract tree canopies and rooftops stably and reliably. A power line is used as a bus bar, and a buffer space analysis is carried out according to the safety distance set in specification code so obstacles can be detected automatically
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