Failure mechanisms and recent improvements in ZnO arrester elements

ZnO arrester elements can fail by a number of mechanisms, including electrothermal instability and thermal stress-induced mechanical cracking in this brittle ceramic. Breakdown channels at the edge of the electrode are among the most common failure mechanisms at high currents. Such failures take the form of a melt puncture of the element from the electrode edge to the opposite electrode or to the edge of the disk. This failure mechanism limits the energy absorption capability of ZnO arrester elements.