This study evaluates the response of a horizontal grounding electrode against impulsive currents whose waveforms and time front is typical of lightning. The electrode is found buried in soil with different resistivity values and whose conductivity and permittivity vary with spectrum frequency of lightning according four formulations exists in literature. It was possible to observe the intense propagation effects responsible for the grounding impedance values significantly different from the resistance at low frequency and also difference according to each formulation, which has decreased the potential, the impedance impulsive and impulsive coefficient compared to traditional data from the technical literature specialist.Index Terms--Variation of conductivity and permittivity of soils, electromagnetic transients, frequency dependence, grounding model.

Some data of currents of lightning events measured in Morro do Cachimbo Station during the period 2008-2012 are presented, comprising 9 downward negative first strokes (4 of them pertaining to multiple-stroke flashes), 8 unconnected upward leaders developed in response to downward negative leaders approaching the ground and 5 negative upward lightning. The current waves of all negative upward lightning are presented along with an example of representative waves for first stroke and unconnected upward leader currents. Parameters of such currents are summarized.

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