Transition of MOV distribution arresters from capacitive to resistive during steep-front impulses

The current responses of MOV (metal oxide varistor) distribution arresters to steep-front rectangular voltage pulses were measured in the voltage range where the arresters were converting from dielectric to resistive behavior. At the lowest voltages, a purely capacitive current response was measured, with current pulses only during the rising and falling portions of the voltage pulse. At higher voltages, the current response had an initial spike followed by a conduction current. In the transition region, random delays in turn-on of the arrester currents were observed. This delayed turn-on phenomenon possibly reveals that a dynamic instability of the current-voltage characteristic of the MOV arrester material may exist in the breakdown region during a steep-front voltage impulse