绝缘子污秽等级红外热像检测的视角影响分析

为了提高绝缘子污秽等级红外热像检测的准确性,提出利用绝缘子红外热像污秽等级分类特征的对比分析确定最佳成像角度的方法。该法采用直方图均衡化增强原始红外热像对比度,人工截取绝缘子盘面图像区域;基于盘面图像直方图包络线提取分割阈值,对阈值分割后的二值图像进行形态学滤波,得到绝缘子盘面图像;应用统计理论从绝缘子盘面图像提取最高温度、最低温度、平均温度、温度分布方差等10个红外热像污秽等级分类特征;运用Fisher准则对特征进行对比分析。瓷绝缘子人工污秽试验红外图像分析结果表明:成像角度变化显著的改变所得绝缘子表面热场;下盘面特征比上盘面特征有更好的分类性能。推荐绝缘子污秽等级红外成像检测应以下盘面为准。

Analysis of Visual Angle Influence on Infrared Thermal Image Detecting of Insulator Contamination Grades

In order to improve the accuracy of detecting insulator contamination grade by infrared imaging,a method to determine the best visual angle using comparative analysis of pollution grade classification features Abstracted from insulator infrared images is proposed. The image region of the ceramic piece surface of insulator is intercepted manually after the contrast of the original thermal image was enhanced by histogram equalization. The intercepted image is binarizated according to the segmentation threshold extracted from the histogram envelope line. The ceramic piece surface image of insulator is extracted through morphological filtering on the binarizated image. From which ten pollution grade classification features are extracted statistically,such as the highest temperature,the lowest temperature,the mean temperature,the temperature variance of the insulator surface. The Fisher criterion is applied to comparative analysis. The analytical result of porcelain insulator infrared thermal image from artificial pollution test indicates that the thermal field of insulator surface significantly changes with the angle of view,and the features of lower surface have better classification performance than the uppers. It is recommended that the visual angle should aim at the lower surface for detecting insulator contamination grades by infrared imaging.