Space charge and soil ionization: an electro-kinetic approach

Abstract

This paper proposes an electro-kinetic model of soil ionization for concentrated electrodes submitted to impulse currents. This approach allows a better understanding of the dynamic response of earth rods. Since current density attains a sufficient value around the electrode, ionization appears in the soil and produces a transient reduction of the grounding resistance. Experimental results, obtained under well-controlled conditions in laboratory, indicate that the injected energy is the most important parameter in the transient resistance reduction, rather than the crest value of impulse currents. The meaning of this resistance reduction is interpreted by the electro-kinetic model that calculates the resistance-time variation by computing the energy required to arrange a distribution of space charge around the electrode. A practical conclusion of this energy-depending interpretation for grounding electrodes, is that with ionization it would be attended a significant and durable reduction of the transient resistance for long impulse currents.

Experimental impulse response of grounding systems

“…Two thousand five hundred points were calculated and in the sequence they were connected by line segments. The result was consistent with that from several studies that give the behavior presented due the ionization effect of the soil submitted to current impulses, as presented in [11,12,13,14].…”

A New Flexible Graphite Composite Electrical Grounding Material

“…Therefore, the withstand impulse current level becomes an important index. Three typical impulse currents have been applied, including the lightning impulse current, oscillatory impulse current, and short-circuit impulse current (Manna and Chowdhuri, 2007) (Diaz and Silva, 2011). Three samples were used for each impulse current.…”

“…A series of mechanical performance tests were conducted on FGCGM to analyze its mechanical property under external force quantitatively (Diaz and Silva, 2011). It contains bending, torsion, and tensile resistance.…”

Tower impulse grounding resistance measurement based on multiple frequency impedance

“…S. Sekioka proposed a current‐dependent grounding resistance model with consideration of soil ionization and explained the reason why the impulse response voltage lags behind the impulse lightning current [5]. R. R. Diaz studied the relationship between the impulse electromagnetic characteristics of grounding electrodes and lightning current energy, and pointed out that the impulse grounding resistance is mainly determined by the energy of lightning current [6]. R. Alipio proposed acceleration algorithms for the estimation of impulse grounding impedance, impulse coefficients and the effective length of grounding electrode [7].…”