Partial discharges measurements on conventional and nanocomposite enameled wires varying the ambient conditions

Stator motor windings of low voltage rotating electrical machines are usually insulated by organic enamel. If during the normal operation partial discharges incept, degradation phenomena and in particular erosion, due to partial discharges, could take place leading the insulating system to breakdown conditions. In this research activity, conventional and nanocomposite enamels have been analyzed: suitable twisted pair specimens insulated by the considered enamels have been prepared and tested. The specimens have been subjected to electrical aging varying the ambient conditions and in particular varying the relative humidity level. The specimens have been subjected to different 50 Hz sinusoidal voltage waveforms having amplitude level higher than the partial discharges inception voltage in order to operate in presence of partial discharges activity. During the aging, digital partial discharges acquisition has been performed in order to obtain useful information about the degradation processes. The time to breakdown of the tested specimens have been collected: analyzing and comparing the obtained results in terms of both time to breakdown and partial discharges activity it has been possible to evidence the different behavior between the considered enamels when subjected to the erosion effects.