Electrical and water treeing: a chairman's view

The essentials of the reports on electrical and water treeing presented at the 3rd ICPADM are summarized. Starting from these findings and including generally accepted facts of the phenomena as well as results published recently, the corresponding model concepts of the two phenomena are described. It becomes evident that bond scission is the decisive point in both deterioration mechanisms. In the case of electrical treeing very high electric fields create hot electrons and/or high energetic photons that cleave molecular bonds and produce radicals. Small voids and tree channels are generated in which gas discharges occur. In the case of water treeing the precipitation of water droplets leads to a local mechanical overstressing of the neighboring polymer chains and finally to their disruption. Depending on the availability of foreign substances, e.g., oxygen, additional chemical reactions may occur and influence further development of the trees.>