The reliability of the power cables strongly depends on the single or multiple stresses that could develop within their insulation system. The electric stresses as overvoltages, dips, harmonics and inter-harmonics contribute to a drastically reduction of the insulation lifetime, damaging the insulation of cables mainly through partial discharges (PD) and charge accumulation. This paper deals with the influence of different applied voltage waveforms on partial discharge activity within the insulating material of power cable. The PD activity was investigated under sinusoidal, DC-step and bipolar rectangular testing voltage waveforms at the frequency of 50 Hz and 0.1 Hz, applied to the micro-cavity embedded in cross-linked polyethylene. Using the step-up voltage test method, the characteristics of PD were assessed. The results show that the sinusoidal waveforms at 0.1 Hz generally provide the lowest partial discharge inception voltage (PDIV) values. The PDIV increases slightly with frequency.

Keywords: Partial discharge, Inception voltage, Step-up voltage test method, Sinusoidal waveform, DC step waveform; Bipolar rectangular waveform