Final Breakdown on Water Tree Degraded Polymer Insulation

  • Vu Thanh Hai
  • Nguyen Dinh Thang


This report deals with the mechanism of the final breakdown of polymeric power cables which have been degraded by water trees. Water treeing is one of the major degradation mechanisms in cable insulation. It has been believed that the final breakdown takes place when a water tree penetrates the insulation. In order to reproduce penetrating water trees in a film specimen, a double layer specimen with low-density polyethylene films was subjected to an aging test to generate water trees. After confirming that penetrating water trees had bridged across one layer of the ”double-layer” specimen, the breakdown test was performed with several kinds of combinations of degraded and non-degraded films by applying an AC voltage. It was concluded from the result that the penetrated water tree region would withstand relatively high voltage stresses if the ambient relative humidity was as low as 59 %, however, the breakdown voltage rapidly drops at higher humidities. Finally, it was suggested that, under less humid conditions, a water tree would extend until it bridges across the insulation without causing breakdown, however, the breakdown would likely take place when the ambient humidity turns to be higher.


Vu Thanh Hai
Journals of Science 70 Tran Hung Dao Str, Hanoi, Vietnam
điểm /   đánh giá
Materials Science