Impact of Inaccuracies in Defining the Transient Step Voltage Due to Impulse Currents on Grounding Grids

Abstract:
Electrical substations are susceptible to several electromagnetic surges. Short-period surges due to lightning strikes at or near the substation typically present fast transients. Thus, one concern in the studies investigating this stress is the definition of voltage used to ensure safety inside (and near) a substation under fast or very fast transient phenomena. This work deals with the electric field due to impulse currents injected in buried conductors and the difference between considering the traditional step voltage definition proposed by IEEE standards and a more rigorous definition (line integral of the total electric field, which corresponds to the vector sum of the conservative and non- conservative components). The current distribution and originated electric field are evaluated by using a well-established electromagnetic model. According to the results, significant differences can be found in the analyzed configurations for fast phenomena.