## 6 Conclusions  
The UV imaging method can be used to detect the surface discharge of charged equipment without contacting high-voltage electrical equipment. In the detection of the leakage of insulators by the method, the amount of leakage can be characterized by the facular area. In order to perform the imaging segmentation on different facular areas, we propose a segmentation algorithm for the facular area based on the Gaussian color mapping. Experiments prove that the segmentation algorithm is effective and robust. The expressions of the facular area and the shooting distance are analyzed experimentally,  
Figure 18: Parameter statistics chart. (**a**) Standard deviation. (**b**) Range. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Type** & **Sum** & **Maximum** & **Range** & **Standard Deviation** & **Average** \\ \hline Pollution & 1023.7 & 3376 & 2855 & 0.409 & 2.78 \\ Rough & 621.9 & 1031 & 585 & 0.169 & 0.94 \\ Crack & 1046.6 & 1631 & 1138 & 0.176 & 1.08 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Statistical characteristics of insulator facular area of different fault types. and the factors that affect the attenuation function coefficient of the light plate area are distinguished. Also, the scalar area's change trend in the defective insulators and polluted insulators is analyzed through an onsite inspection. The obtained information leads to the following conclusions:  
1. The image segmentation algorithm based on the Gaussian function color processing can segment the scalar area of different colors and effectively reduce the grayscale mixing degree between the scalar and the background. The grayscale ranges of facular, insulators, and background are clearly separated. In particular, the gray value decoupling between the facular and the background: facular is [210; 255], while the background is [115; 210]. At the same time, the gray value of the insulator is smoother, at 80. Experiments show that the differentiation between facular and background is increased, and the method is effective and robust. 2. Since the facular area taken by the UV imager changes with time, the mean value of the statistical characteristics of the spot area over a period of time can better characterize the changing trend of the facular area. 3. The discharge facular area increases with the voltage increasing, but they are not linearly related. It will reach saturation before the flashover occurs. The change range of facular area in the rough-surface insulators and shed-crack insulators is relatively small. The range and standard deviation of the facular area caused by the pollution discharge are obviously larger than those caused by three other defects. 4. The distance between the UV imager and the insulator is an important reference factor for detecting the facular area. In this paper, the qualitative law is obtained from the experiment, but the mathematical model is not formed. Project administration and funding acquisition, J.C.; data curation, G.Z. ; design and simulation of the algorithm, Y.G. ; writing--original draft preparation, S.Y. ; writing--review and editing, R.S. All authors have read and agreed to the published version of the manuscript. This research was funded by China Three Gorges Corporation Shanghai Investigation, Design & Research Institute Co., Ltd., grant number 2021 FD(8)-016. Not applicable. Restrictions apply to the availability of these data. Data was obtained from Shanghai Fengxian Bay wind farm and are available from the authors with the permission of Shanghai Fengxian Bay wind farm. The authors thank the Editor-in-Chief, Associate Editor, and Peer Reviewers for their valuable comments and suggestions. The authors also would like to thank the faculty in the Shanghai Investigation, Design & Research Institute Co., Ltd., China Three Gorges Corporation, and Shanghai University of Engineering Science for their support of data sampling. Authors [PERSON] and [PERSON] were employed by Shanghai Investigation, Design & Research Institute Co., Ltd., China Three Gorges Corporation.