Partial Discharge Characteristics and Mechanism of Medium Voltage Power Cable Defects under Different Voltage Stresses

Abstract

Off‐line partial discharge (PD) diagnosis, which requires an additional power supply has been accepted as an essential step in ensuring the integrity of power cable systems during commissioning testing. Many types of energizing voltage sources (e.g., alternating current resonance, damped alternating current, very low frequency [VLF] sine, and VLF‐cosine rectangular) have been developed, which are used in practice. However, choosing the optimal energizing voltage waveforms for PD testing is still controversial because their capability to motivate PD activities is still unclear. Accordingly, this paper compares the PD ignition capacity of the aforementioned power sources on six well‐designed PD defects in real cable joints. The influence of test voltage frequencies and waveforms are verified. The results show that the PD inception voltage and PD magnitudes in the cable joint defects do not change significantly as a function of the sinusoidal voltage frequency and the VLF‐cosine rectangular voltage exhibits excellent PD ignition capability with a low PD inception voltage and large PD magnitude. Moreover, the dynamic behavior of space charge in a PD defect caused by a gap is analyzed in order to explain the obtained results. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.