Electro-thermal-mechanical computations in ZnO arrester elements

Transient, nonlinear finite element analysis with coupled thermal and elect ric fields is employed to compute the electric and thermal field distributi ons in ZnO arrester elements, including both nonlinear electrical and nonli near thermal properties. Mechanical stress in the element is computed durin g post processing, based on the thermal field. The data indicate that a met allic protrusion from the sprayed electrode into the ZnO can cause substant ial temperature rise in a microscopic region around the defect. The effects of a delamination between the electrode and the ZnO surface are less sever e. Statistical computations have been undertaken to explore the effect of n onconducting grains on the disk conduction threshold voltage and disk nonli nearity. The computations yield similar results to those in the literature based on nonlinear circuit equations but are much less time consuming.