The mechanical damage theory of water treeing-a status report

The author outlines the mechanical damage theory and the electrochemical theory of water treeing. A selection of experimental results is then reviewed, mainly based on work done in the author´s laboratory to examine the validity of the mechanical damage theory. It is noted that, even though no single experiment can prove or disprove this theory, many experiments have led to results which are in agreement with it. This is particularly true for the initiation of water trees. It is possible that chemical or electrochemical reactions play a more important role in the growth phase, mainly because of their influence on the hydrophobicity and the mechanical properties of the material