Influence of AC voltage prestressing on AC electrical-tree inception of deteriorated LDPE with dried water-tree

In order to improve the accuracy of degradation diagnosis for CV power cables, it is important to clarify the inception and propagation mechanisms of electrical tree degradation from water tree degradation. This paper presents the influence of AC voltage prestressing on the inception voltage of AC electrical-tree in the deteriorated LDPE with dried water-tree. The experiment was carried out with a small LDPE-block (3 mm×10 mm×15 mm) with the needle-plane electrode system, in which the inception voltage of AC electrical-tree of LDPE without water tree was from 5 kV_rms to 8kV_rms. The prestressing conditions, i.e. the ambient temperature, the voltage amplitude and the voltage duration time, were varied. The results suggest that the degradation under AC voltage application is enhanced by the existence of water-tree degradation and affects AC electrical-tree inception.