Impact of High Frequency Risks in Insulation Systems of Electric Machines

Abstract

Abstract: Exploitation stresses are causing degradation of high voltage insulation systems. The assessment of intensity and dynamics of these processes, being a consequence of local, working electric field strength is considered mainly at the sinusoidal voltage. However in applications where power electronics converters are used the voltage stress has usually a form of fast switching pulses composed of repetitive sequences. Such pulse trains pose usually a modulated width and fast rise- and fall-times. Such conditions have essential influence on inception and development of partial discharges in insulating systems subjected to non-sinusoidal stimulus. The insulation degradation mechanism is especially important for cables and electrical machines subjected to non-sinusoidal waveforms. The paper will present experimental results of application of non-sinusoidal waveforms on polymer cable insulation with special focus on rise time influence. The correlation with the spectral content will be also considered.