High-Frequency Metal-Oxide Varistor Modeling Response to Early-time Electromagnetic Pulses

The electric power grid is one of the most critical infrastructures in the modern world, and the continued protection and resilience of this system from threats is of significant concern. One such set of threats is nanosecond-scale transient effects generated by high-altitude electromagnetic pulses, for which the effect on the power grid is still being studied. Lightning surge arresters serve as the current grid protection against fast transients but are designed and modeled for protection against lightning and switching transients. Surge arrester response to faster transients is not well known. This work defines a scalable metal-oxide surge arrester model with specific consideration to frequencies attributed to fast transient overvoltages from electromagnetic pulses. Measurements using vector network analyzer sweeps at low and high bias as well as high-voltage I-V curve traces are presented to define arrester behavior and to parameterize it from measurement data. The proposed model is compared to the standard IEEE model for lightning arresters in this paper. Furthermore, model parameters are defined by scalable terms to be easily implemented for transmission-level devices. The scalable model enables enhanced assessment of protection levels and grid susceptibility against fast transients.