Creeping flashover phenomenon on ZnO element used for surge arrester

As one of destruction phenomena of zinc oxide (ZnO) surge arresters, a stripe-shaped destruction at the lateral face of a ZnO element is confirmed. To investigate such destruction mechanism, lightning impulse current was applied to a ZnO element. A melt puncture at the surface electrode edge was formed by excessive energy absorption, which induced a creeping flashover. Even if electric charge owing to a surge event was small, the plural applications of surge events caused temperature increase of a ZnO element. Such heat accumulation may also trigger a formation of a melt puncture and a creeping discharge.