## 5 Conclusions  
This study conducted measurements and research on the photon count and spot area during corona discharge in relation to different sizes of smooth, stainless-steel conductors under positive DC voltage using a mini corona cage and further explored the variation patterns of the photon count and spot area during the corona discharge process. Additionally, this study analyzed the changes in photon count and spot area with respect to the UV imaging device gain and observation distance, and formulas were fitted to correct the actual measurement data to the reference measurement standard. The main conclusions are as follows:  
1. The photon count and the spot area both exhibited a quadratic relationship with the conductor voltage, and they exhibited a close linear relationship with the corona current. Therefore, the ultraviolet photon count and the area of the light spot can be used to quantify the discharge intensity.
2. The photon count and spot area both decrease exponentially with an increasing observation distance. Under the conditions of ensuring a complete observation of the discharge area and maintaining a safe observation distance, the smaller the observation distance, the better the measurement results. The photon count exhibited a more complex relationship with the gain. As the gain increased, the photon count did not monotonically increase but underwent a process of initial increase, followed by a decrease, and then another increase. For the UV imager used in this study, the detection effect was best when the gain was 60%. On the other hand, the spot area showed an exponential increase with the gain. In practical engineering applications, the gain and observation distance can be adjusted according to the actual situation. Then, the calibration formula summarized in this paper can be used to correct the measurement parameters, which is convenient to compare the measured results under a unified standard and better evaluate the corona discharge intensity.
3. Both the photon count and the spot area can be used to describe the intensity of corona discharge. The photon count provides a more intuitive measure, while the spot area requires some image processing techniques. By using a combination of both UV detection parameters, it is possible to identify and characterize corona discharge phenomena in power transmission lines more accurately and comprehensively.  
Conceptualization, Y.D., Z.Z. and Z.D.; methodology, Z.Z., D.J. and Y.W.; software, Y.D.; validation, Y.D.; formal analysis, Y.D. and Z.Z.; investigation, Y.D.; resources, Y.W.; data curation, Y.D.; writing--original draft preparation, Y.D. and Z.Z.; writing--review and editing D.J., Z.D. and Y.W.; visualization, Y.D.; supervision, Z.Z. and Z.D.; project administration, Z.Z.; funding acquisition, D.J. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the National Natural Science Foundation of China (No. 52007011).  
Not applicable.  
The data that support the findings of this study are available from the corresponding author upon reasonable request.  
Author [PERSON] was employed by the company \"Chengdu Power Supply Company\". The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.