A new deterministic model for tree growth in polymers with barriers

The growth of electrical trees in heterogeneous solid dielectrics was investigated by means of two-dimensional numerical simulations. In contrast to conventional approaches the introduced newly developed algorithm is based on a deterministic model together with a spatial distribution of the electrical breakdown strength. With standard needle plane geometries, two main types of treeing, bush-like and branch-like, were simulated correctly in respect to their shape and the general voltage dependency. The tree propagation in homogeneous dielectrics as well as the effect of barriers upon treeing was simulated. This tree formation was compared to tree growth in epoxy resin with an embedded glass-mica layer. The effect of electrically weak interfaces between the polymer and the barrier was investigated and the mean time to breakdown was compared for different set-ups. From this comparison it was concluded that only barriers with intact interface zones, whose breakdown strength is not weakened, lead to an optimum of tree resistance