Effect of repetitive impulsive and square wave voltage frequency on partial discharge features

To ensure the reliability of rotating machines driven by power electronics, partial discharge inception voltage (PDIV) tests at repetitive impulsive voltages are required to be performed on insulation systems of inverter-fed motors. Different from many off-the-shelf instruments used for PD tests under sinusoidal voltage conditions, there is few commercial instruments based on mature technologies specially used for PD tests under repetitive voltages with fast rise times. Moreover, it is of importance to consider carefully the influence of voltage parameters on PD features when performing PD tests using impulsive voltages to choose generators with appropriate parameters and thus, increase test sensitivity. To investigate the effects of repetitive impulse voltage frequency on PD events in this study, PD tests were carried out on three types of insulation models (i.e. crossed wires, twisted wires, turn insulation of Type II motors) by using two high voltage generators, which can produce repetitive square wave voltages and short time impulse voltages with continuously adjustable frequencies, respectively. Experimental show that with increasing square wave voltage and impulsive voltage frequency, PD magnitude and delay time will decrease significantly. Accordingly, relatively lower frequency is recommended to obtain higher sensitivity and objective PDIV values when performing PDIV tests on insulation systems to increase signal to noise ratio.