Study on Aging Rate of XLPE and its Nanocomposites under Nonstandard Voltage Stresses

Long-term aging tests of XLPE and 1wt%, 3wt%, and 5wt% XLPE-Al2O3 nanocomposites under two different types of electric stresses were carried out. The first stress type represented the ideal sinusoidal waveform, whereas the second one represented a waveform polluted by supraharmonics. The obtained data were treated by Weibull statistics per IEC 62539 / IEEE 930 standard to obtain characteristic lifetimes. Subsequently, the lifetime electric stress data points were fitted by lifelines using the inverse power law. The results indicated that the 1wt% and 3wt% nanoXLPE samples degraded faster than the unmodified XLPE, especially under the nonstandard supraharmonic stress. Conversely, the 5wt% nano-XLPE seemingly degraded slower. No significant increase in the aging rate of the unmodified XLPE samples was observed at lower stress levels under the supraharmonic electric stress.