Dynamic impulse conduction in ZnO arresters

In this paper, new fast-impulse test data obtained on ZnO surge arresters with a special coaxial test cell are presented. The time-to-peak of the discharge current was observed to become shorter as the magnitude was increased. An explanation for this phenomenon is suggested based on changing current paths within the material. To account for this dynamic behaviour, the authors propose an equivalent circuit which uses parallel paths with associated inductances and resistances to model the conduction process in the intergranular layer