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This paper reviews results of partial discharge measurements and accelerated life tests performed on models of random and form wound insulation systems subjected to impulse voltage waveforms. The goal is to highlight how the features of the supply voltage affect the partial discharge activity and how this, eventually, reflects on the endurance of the insulation system. The most salient results are that, for both types of insulation systems, short rise times trigger PD of large magnitude, which are able to erode the insulation system faster than the partial discharges incepted using waveforms with longer rise times. In particular, failure times estimated by tests under sinusoidal voltages can be overly optimistic in assessing the long-term behavior of the insulation system subjected to impulse voltage waveforms. Frequency also is very important, as it controls the interplay between physical and chemical degradation rates. As a result, above partial discharge inception voltage the frequency acceleration rule does not hold, and can lead therefore to excessively optimistic results. [ABSTRACT FROM AUTHOR]

The dependence of endurance test results on repetitive square wave voltage waveform parameters is investigated in this paper focusing on crossed pair specimens made of polyamide-imide enameled wires. Endurance tests carried out on crossed pairs above partial discharge inception voltage using both sinusoidal and square wave voltages show that lifetimes can be influenced significantly by voltage waveform parameters (rise time and frequency). Partial discharge statistics, recorded from test beginning to breakdown, are used to explain the remarkable differences associated with voltage waveform parameters. According to this study, the influence of voltage waveform parameters should be carefully considered in order to obtain effective evaluation of inverter-fed motor insulation systems. [ABSTRACT FROM AUTHOR]