Modeling on the failure of MOV for high-voltage arresters by Voronoi network simulation

The effects of microstructural disorder parameters, such as grain sizes and grain boundaries, on puncture fails in ZnO varistors are simulated by calculating the current densities and energy absorption capabilities in Voronoi networks of which can be described by nonlinear electrical characteristics. By comparison the effect of Joule heating and the current localization with conditions of impulse surge energy applying to ZnO varistors, the mechanism of puncturing fail can be analysed quantitatively. Current localization increases with increasing applied voltage, as the successive breakdown of barriers enables the current to be drawn into the preferred paths. Eventually a maximum localization is reached in the upturn region of the I-V curve. The longer the pulse, the greater the temperature increase at a given voltage and the delay in returning to the upturn region behavior. The temperature localization that accompanies the current localization is seen by comparing the temperature in the path with the highest current with that in the adjacent path.