Icicle Characteristics And Surface Flashover On Ice-Covered Suspension Insulators Based On Image Processing Method

With the development of power grid technology in China,theboard construction of high voltage power transmission network,the continuous development of the world highest operating voltage and transmission capacity represent the highest technical level of the strongest UHV ac and dc power transmission and transformation projects.The insulator as the basis equipment for the development of UHV line equipment,the reliability is essential to the safety and stability of power system.The ice-coveredinsulator is one of the main reasons causing the flashover accident,which is of great research significance and the practical significance.This paperproposes the image processing methods for the icing characteristics of ice-covered insulators.Firstly,in view of the ice at the scene of the high image noise and the background of fuzzy characteristics,the weighted average method of image gray level is selected for the image pre-processing.Then,by using the direct equalization and gray stretch,the grayscale image of ice-covered insulatoris enhanced to improve the image contrast and to sharpen the image edge.For the image noise,the wiener filtering and median filtering methodsare conducted for the noise reduction,which is a foundation for the further processing of ice-covered insulator images.Aiming at theshed icicle and airgap characteristicsof ice-covered insulator surface,a processing method for theimage isput forward to extract the air-gap length,number of air gaps and other characteristics for analyzing the ice characteristics of ice-covered insulator to accurately estimate the reliability ofice-covered insulator.Firstly,by choosing the maximum entropy threshold segmentation algorithm,the image grey value distribution and the average grey value distribution within the target pixel neighborhood are carried out for the image threshold segmentation,obtaining the binary images of insulator and its surface ice image from the background.Then,the improved Canny edge detection operator is used for the ice image edge detection,obtaining the edge of the non-ice-covered insulator image.Combined with the binary image processing results,the air-gap length,number of air gaps and other characteristics are extracted as the judgment of ice-covered insulator.Finally,based on the image processing results,the icing process on outdoorinsulators can be divided into two stages: icicle bridged and non-bridged.Combined with the insulator parameters on icicle length,the formulas of calculating the icicle length is obtained to predict the ice characteristics during the icing process,such as the icicle growth length and the air gap length.For analyzing the flashover on ice-covered insulators,the discharge images of ice-covered insulator duringthe flashoverare analyzed for the characteristics extraction based on the image processing method.Asdifferent characteristics can be foundfor the discharge characteristics of ice-covered insulator under different conditions.The flashover process of ice-covered insulator can be divided into stages to extract the image grey value and the arc length as the characteristic value for the flashover prediction.The quantitative analysisof GI(the ratio ofTotal gray value to length of Image)and LI(the ratio oflength of Surface charge arc to length of Image)are put forward as therisk value of ice-covered insulator flashover.Once the GI and LI values exceedthe threshold value,the higherflashover risk of ice-covered insulator can be obtained.