AC dissipation current waveform and space charge formation of water-tree-degraded polyethylene film

The possibility of the new diagnostic method of water tree degradation is examined by observing the high field AC dissipation current waveforms and the space charge formation in water-tree-degraded low-density polyethylene (LDPE) films. The AC dissipation current waveforms of water-tree-degraded LDPE film contains more higher harmonic components than those of undegraded films. Furthermore, the differences between undegraded and water-tree-degraded films were observed in their space charge distribution. It can be speculated that the space charge was formed by the carrier injection from the water-tree-degraded region rather than the effect of the impurity ions in the bulk of the materials. The distortion of the high field AC dissipation current waveforms in water-tree-degraded LDPE films is considered to have some correlation to the space charge formation.