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Rejuvenation of power cables addresses water trees, voids, or electrical trees. Partial discharge (PD) in joints or terminations are addressed by the sustained pressure rejuvenation process, which replaces all terminations and joints. In this study, partial discharge inception voltage (PDIV) is found to increase by 27% for each 0.1%w in crease in fluid concentration in field-aged rejuvenated cable samples. The mechanism of rejuvenation is discussed in which PD mechanism is prevented by plasticizing the dielectric, filling the voids, smoothing electrical stress, and sequestering free electrons in field-aged cables. [ABSTRACT FROM AUTHOR]

The reliability of low-voltage inverter-fed motors is highly dependent on the inception of partial discharges. The effect of impulsive waveform parameters must be investigated to predict the repetitive partial discharge inception voltage (RPDIV) and define test procedures that can indicate properly the behavior in service of the insulation system. This paper focuses on the RPDIV of magnet wires using twisted pairs subjected to repetitive unipolar impulsive voltage waveforms. The effects of supply frequency (5 to 200 kHz) at pressure levels that are typical for aircraft (20 to 100 kPa) is examined. Results show that RPDIV steadily decreases with frequency up to 100 kHz where it reaches a plateau. This behavior is explained as an effect of the oscillations that inevitably exist in the applied voltage waveform. Therefore, a conservative estimate of the RPDIV could be achieved by raising the supply frequency well above the operation frequency. In the experiments, the RPDIV is decreasing linearly with pressure. If this behavior could be confirmed for other insulation systems, the design of systems working at pressures typical of aircraft would result relatively easy. [ABSTRACT FROM AUTHOR]