Voltage endurance of electrical components supplied by distorted voltage waveforms

The increased diffusion of power-electronic drives in electrical plants and networks is worsening the quality of energy supply, particularly voltage-waveform distortion. The harmonic content of voltage and current has been shown to contribute to accelerated degradation of insulation systems and, thus, to premature failure of electrical components. This paper focuses on life performance of insulation systems (capacitors and induction motors) supplied with nonsinusoidal voltage. The results of life tests under sinusoidal and distorted voltage waveforms are presented and discussed on the basis of the Voltage Endurance Coefficient of the life lines, considering various reference factors, such as voltage peak, peak-to-peak and rms. In particular, the distorted waveforms are obtained considering either low-frequency harmonics (typically present on supply ac lines) or high-frequency harmonics (affecting insulation systems of power-electronics controlled loads). It is shown that the main acceleration factor should be associated to the increase of voltage peak and supply-waveform frequency, while waveshape and rms value can play a minor role