Electro-thermal-mechanical computations in ZnO arrester elements

Transient, nonlinear finite element analysis with coupled thermal and electric fields is employed to compute the electric and thermal field distributions in ZnO arrester elements, including both nonlinear electrical and nonlinear thermal properties. Mechanical stress in the element is computed during post processing, based on the thermal field. The data indicate that a metallic protrusion from the sprayed electrode into the ZnO can cause substantial temperature rise in a microscopic region around the defect. The effects of a delamination between the electrode and the ZnO surface are less severe. Statistical computations have been undertaken to explore the effect of nonconducting grains on the disk conduction threshold voltage and disk nonlinearity. The computations yield similar results to those in the literature based on nonlinear circuit equations but are much less time consuming.