HVDC partial discharge mechanisms and flashover characteristics with charging activities on solid insulators in air

DC partial discharge (PD) characteristics with PD inception voltage are measured depending on the different electrode gap lengths and electrode configurations, with and without solid insulators as PMMA, in air. The charges deposited on solid insulators are measured by surface potential measurement systems. By using the FEM electric field analysis, we could estimate the Flashover (FO) voltages under charging conditions in air/solid composite systems and compare them with those obtained from experimental results. It was concluded that the DC-PD inception and flashover voltages are quantitatively determined by the DC applied electric field, PD space charges and deposited surface charge distributions, depending on the DC polarity of applied voltages.