Research of Measurement on Insulator's Contact Angles Based on Image Processing

Abstract

The contamination flashover resistant performance of an insulator is due to the hydrophobicity on its surface. So measuring the hydrophobicity of insulators is an important way to evaluate their performance.This research proposes a method to auto-detect insulator's contact angles with image processing and curve fitting. According to the characteristic of water drop on insulator's surface, the median filter and the gray stretch are adopted to preprocess the water drop image. The edge detection algorithm with the Robert operator and the iterative arithmetic on optimized threshold for region partition are deployed to implement image segmentation. The proposed method combines iterative arithmetic for sketch extraction and the neighborhood arithmetic for outline tracking to find the corresponding water drop contour. Then, the polynomial fitting is deployed to fit the discrete points on the drop contour and the contact angles can be calculated by derivation from the polynomial deduced from the polynomial fitting. Experiments show that the method is feasible for detecting the accurate contact angles and the root mean square error is below 2％.