Study on Edge Extraction Methods for Image-based Icing On-line Monitoring on Overhead Transmission Lines

A new method of measuring the icing thickness of transmission lines on-line is proposed in this paper. In this method, the pictures of transmission lines which are photoed by the camera on the iron tower are processed immediately to extract the edges of the transmission line conductor and transmission line insulators. The icing thickness can be gained by comparing the edges of the iced transmission line and uniced one. Two icing image edge extraction methods are described in detail, that is, a method based on the combination of wavelet transform and floating threshold and a method based on the combination of optimal threshold and mathematical morphology. The icing images from the artificial climatic chamber and transmission lines are used to test the methods above. The results show that the method based on wavelet transforms and floating threshold does well in the extraction of relatively smooth edges, such as glaze icing on conductor and icing on insulator; meanwhile, the method based on optimal threshold and mathematical morphology does well in the edge extraction of icing on conductor, especially the opaque rime icing on conductor with complicated edges.