Title :
On tree-inhibition in polyethylene
Author_Institution :
AEG-Telefunken Forschungsinstitut, Frankfurt/Main, Germany
fDate :
6/1/1978 12:00:00 AM
Abstract :
For a better understanding of the basic mechanisms of electrical treeing in polymer insulations the dependence of the DC-conductivity of polyethylene (with and without additives) on temperature and field strength was examined. Here we found that all additives, and especially acetophenone which is a favorite additive against treeing, substantially increase the conductivity. Due to the low conductivity of insulators, in the case of an AC-voltage load generally there is a capacitative voltage division. This leads to enormous stress concentrations at the site of impurities, which finally may lead to the start of a tree. Considerations using the results of the DCconductivity measurements showed that these local stress concentrations can be diminished to a certain extent by the fielddependent conductivity of the polymer even for 50 or 60 IIz AC-voltage, thus leading to an improved resistance to treeing. The experimental proof for the relevance of this field-grading mechanism is given by the results of treeing-experiments with polyethylene containing specific additives. Furthermore tree-inception voltages of XLPE containing various amounts of acetophenone show a dependence on temperature and frequency as expected in case a mutual capacitativeconductive voltage division is taken into account.
Keywords :
"Conductivity","Additives","Resistance","Polyethylene","Stress","Electric fields","Insulation"
Conference_Titel :
Electrical Insulation, 1978 IEEE International Conference on
Print_ISBN :
978-1-5090-3121-4
DOI :
10.1109/EIC.1978.7463611