Flashovers of Aged Oil-paper Insulation during DC Voltage Preloading

The study of the flashover characteristics of the aged oil-paper insulation under the AC-DC combined voltage demonstrates that the flashover phenomenon of the aged oil-paper samples along the surface of the insulating paper occurs during the preloading of the higher amplitude DC voltage. Flashover occurs when severely aged oil-paper insulation samples are preloaded with high-amplitude DC voltages. However, flashover is not observed with unaged or “non-severely-aged” samples preloaded with the same DC-voltage amplitude. Therefore, in this study, we examine the space charge, physical, and chemical characteristics of aged oil-paper insulation, in combination with its electric-field distribution characteristics, in the context of the electron-triggered polarization relaxation theory.