In this paper, touch and step voltages of different arrangements of rods including single rod, double, triple and quadruple rods under lightning strikes are evaluated. In all analyses, an efficient modeling approach called improved multi-conductor transmission line is adopted. Also, two typical lightning currents namely first and subsequent stroke currents are injected to the mentioned grounding rods. This paper consists of two parts.
In the first part, the touch and step voltages of different arrangements of rods considering dispersion and ionization of lossy earth are computed. Firstly, sensitivity analyses show that from single rod to quadruple rods, both voltages are reduced especially in poorly resistive earths. The relative reduction percentage is on average 81.5% and 69.5% respectively for the touch and step voltages. In addition, when the arm length is increased, considerable reduction of both voltages especially in poorly resistive earths under subsequent stroke current is achieved so that the length variation from 10m to 40m, leads to the reduction of 85% and 91% respectively for the touch and step voltages on average. Depending on the earth resistivity and lightning waveform, after a starting length this reduction is slightly continued.
In the second part, the above analyses are extended to two-layer earth and sensitivity analysis versus the resistivity of the two layers is carried out. The simulation results show that both voltages have middle values between the counterparts in single-layer earths.