Study on Field Distortion and Surface Flashover Characteristics of Epoxy Glass Fiber under Low‐Temperature Gradient

The terminal insulation of superconducting power equipment operates in environments characterized by low temperatures and large temperature gradients, making its surface flashover characteristics a critical factor that limits system reliability. In this study, a low‐temperature gradient flashover test platform was developed to investigate the flashover voltage and its underlying trends in glass‐fiber‐reinforced epoxy (GFRP) across various temperature differences (ΔT = 0–100 K). A charge migration model, previously validated in our work on trap characteristics, was employed to aid in interpreting the experimental results. The results indicate that low temperatures inherently suppress flashover; specifically, the isothermal flashover voltage at 193 K is 16.15% higher than that at 293 K. However, the introduction of a temperature gradient significantly reduces the flashover voltage. At ΔT =100 K, the flashover voltage drops to merely 75.13% of its isothermal counterpart, and the partial discharge inception voltage decreases by 24.62%. Simulation analysis reveals that this reduction is due to severe electric field distortion at the high‐voltage terminal: 80.67% of the total voltage drops within the first 2 mm, and the tangential surface electric field is amplified eightfold. These findings provide quantitative experimental data and mechanistic insight for the insulation design of superconducting terminals. © 2026 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.