An investigation on the distribution of ions and water in water trees by FTIR microspectroscopy

Water treeing is an important degradation phenomenon which takes place in the polymeric insulation of electrical cables, under the action of an ac field and in the presence of moisture. The water tree consists of microvoids more or less connected by microchannels or tracks, the density of microvoids (number/volume unit) decreasing from the root to the front of the water tree. The microvoids contain the water and ions which have penetrated the polymer under the action of the electric field. The mechanisms involved are not yet really well understood. Until now, water and ions in the water tree had been examined separately, by different methods, such as infrared spectroscopy, neutron activation analysis or X-ray analysis. In this communication, we present a study of water and ions distribution in the same water tree by FTIR microspectroscopy and we try to correlate our results with the proposed mechanisms for the growth of water trees.