Diagnostic study of electrical treeing in underground XLPE cables using acoustic emission technique

Electrical trees were generated experimentally in samples from a 33 kV underground XLPE cable material under AC voltages. The formation of tree like structure and a bush type of tree structure was observed near the defect site of the insulation structure. To understand the point of inception and propagation of electrical trees, an acoustic emission technique was adopted in the present study. A characteristic change in the frequency content of the acoustic signal is observed as and when the tree propagates in the insulation structure. The partial power measurement used in the study provides an indication of the growth of electrical trees and of the imminent failure of polymer insulation material due to electrical treeing.