Influence of rise time on dielectric parameters extracted from time domain spectroscopy in the context of generator stator insulation

The low-frequency dielectric response of generator stator winding insulation materials was calculated from high voltage time domain spectroscopy measurements. These results were used to calculate the theoretical response after the application of a voltage function consisting of a ramped voltage followed by a constant level voltage. The rate of rise of the ramped portion of the voltage function was shown to influence the well known and much used polarization index (PI) and insulation resistance (IR) parameters.