Research On Sag Measurement Of "Three-Span" Overhead Lines Based On Image Processing

With the high-quality development of the national economy and the in-depth construction of the State Grid’s "Three Types and Two Networks,World Class" strategic goals,the power grid level and transportation infrastructure have been constantly upgraded,and the mutual influence between transmission lines,highways,high-speed railways and other facilities has become a normal trend.In order to improve the operational safety level of the "three-span" transmission line and strong intelligent monitoring technology,it is of great significance to study the method and technology of sag detection for spanning sections.Based on the theory of image vision,this paper has carried out related research on the measurement method of "three-span" overhead line sagging:(1)Aiming at the small curvature of the overhead line of the "three-span" span and the complex surrounding environment,a method for identifying and extracting overhead line images is proposed based on the Hough transform theory,namely,the eight-connected domain clustering Hough transform line group Fitting method.This method first performs an eight-connected-domain clustering analysis of the overhead line edge features detected by Canny to eliminate the linear interference noise of the image background.Then,Hough straight line detection is performed on the edges of different overhead lines marked by the area of the connected domain to solve the problem of missing detection of overhead line edges.Finally,straight line grouping and least squares fitting are used to connect and reorganize the Hough straight line segments.In summary,the overhead line recognition and extraction under the "three-span" complex background is completed.(2)Three-dimensional reconstruction and image correction of "three-span" overhead line based on binocular vision principle.By studying the influence of binocular structural parameters on measurement accuracy,a moving single-camera binocular structural model that satisfies the constraint relationship between the baseline distance B and the safe shooting distance d is proposed.Based on the analysis of the binocular 3D reconstruction theory,the cross geometry characteristics between the overhead line and the epipolar line are used for target matching.Furthermore,the principal component analysis(PCA)was used to reduce the dimensionality of the 3D coordinate point cloud of the overhead line to obtain the 2D overhang fitting plane where the overhead line is located.Finally,the plane was rotated and transformed to complete the image correction.(3)Aiming at the different spanning methods of the "three-span" transmission line,the static analysis of the catenary segment is performed after the correction of the image of the conductor segment.Then,three-dimensional catenary fitting models spanning high-speed buses,railways,and important transmission channels,which are characterized by image geometric parameters,are established.Then,a crossover line model was established under laboratory conditions,and the "three-span" overhead line sag measurement method based on image processing based on this paper was used to calculate the headroom at the crossing point.Then the calculated results are compared with the measured values of the artificial scale to verify the correctness of the method in this paper,and the measurement error factors in the measurement system and curve fitting method are further analyzed.