Analysis of the lightning behavior of an earthing system including ionization via the cell method

In this paper earthing systems under lightning conditions are studied by means of the cell method. Strong ionization and deionization phenomena are included together with their hysteretic behavior. The model of soil resistivity during ionization and deionization proposed by Liew and Darveniza is integrated into a 3D current field code. The simple test case of a hemispherical rod is used as a reference case for tuning space and time discretizations of the 3D approach. An earthing system including an horizontal square grid with four vertical rods at its corners is analyzed and the computed waveforms of earthing voltage and resistance are evaluated and compared with a linear model that neglects ionization phenomena.