Abstract:The partial discharge (PD) phenomenon occurring in the air gap of epoxy resin insulation materials is a key factor leading to a decrease in insulation performance, and its detection and diagnosis are crucial for evaluating the insulation state of the material. Existing research has mostly focused on preparing artificial defect samples and exploring the phenomenon of partial discharge, but there is still a lack of in-depth exploration on the practical conformity of defect models and the specific relationship between partial discharge and air gap size. Therefore, this study proposes a practical method for simulating air gap defects inside insulation materials, and measures partial discharge through three types of sensors to analyze the influence of air gap size on the discharge process. The frequency of the discharge signal was analyzed using Fast Fourier Transform (FFT), revealing a significant correlation between the discharge amplitude and frequency and the size of the air gap. The research results not only provide a new perspective for understanding the influence of internal air gaps in epoxy resins on partial discharge characteristics, but also provide important theoretical basis for defect diagnosis and life prediction of insulation materials.