In searching process for new, advanced technologies which could be applied for on-site diagnostics of machine insulation this paper discuses the application of damped AC voltages to detect and to analyze the PD processes. Based on laboratory investigation on a full scale stator insulation system, as well as during field inspections on large motors, a comparison of PD behavior: the PD inception conditions and PD levels at 50Hz AC stresses and damped AC stresses has been performed. The applicability of PD detection at damped AC voltage has been discussed.@en