As an important part of the power system,overhead lines play an important role in transmitting power.The sag exerts decisive effects on the transmission line operation.This paper proposed a method of sag measurement that combined three-dimensional direct linear transformation (DLT) and two-dimensional DLT.Three-dimensional DLT was applied to solve the projection matrix,and the two-dimensional space coordinates of the conductor point were calculated by two-dimensional DLT.This method can cope with the problem of selecting calibration points by using two-dimensional DLT method as well as reducing calculation compared with the three-dimensional DLT.In order to avoid double edge and fracture,this paper adopts morphological method to deal with the image of the conductor edge detection,and the single conductor is easy to extract by using this method.Based on the theory of chain code tracking,this paper provides a method of line extraction by controlling the direction of searching in the case of conductor crossing.The results of test show that the method proposed in this paper can rapidly measure sag in daily inspection,and the error is about 13cm,which is of high accuracy.In addition,this method is flexible to shoot and easy to operate with low cost and high efficiency,which is of great significance in engineering practices.%架空导线作为电力系统的重要组成部分,肩负着传输电能的重要使命,弧垂直接影响输电线路的安全稳定运行.提出了一种三维DLT和二维DLT相结合的弧垂测量方法,采用三维DLT求解投影矩阵,然后运用二维DLT计算导线序列点的二维空间坐标.避免二维DLT方法标定点选取困难的问题,与三维DLT相比计算量大大减小.使用形态学方法处理导线边缘检测图像,避免出现双边缘和断裂现象,便于单根导线的提取.基于链码跟踪原理,提供了一种通过控制搜索方向在交叉情形下进行导线提取的方法.试验结果表明,在日常巡检时便可采用本文方法实现输电线路弧垂的快速测量,测量误差约为13 cm,具有较高的测量精度,且拍摄角度灵活、操作简单、成本低、效率高,具有重要的工程应用价值.
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