Fixed particles in coaxial SF6 arrangements at various voltage stresses

With special respect to HVDC transmission, an artificial protrusion is investigated experimentally in compressed sulphur hexafluoride (SF
6
) gas. Varied test parameters are voltage waveform and gas pressure. Corona inception and breakdown voltages are measured at DC and AC. Lightning and switching impulse breakdown voltages are evaluated at repeated constant amplitude stress. Composite voltage stress consisting of lightning impulse superimposed to DC bias is further examined. In this case, no significant reduction of lightning impulse breakdown voltage was observed at high gas pressure.