Considering economic aspects, Nezhad et al. [4] presented
an approach based on the particle swarm optimization (PSO)
method to design safety grounding system of a 200 150-m
substation with 21-kA fault current. Taking into account the
safety constraints related to the ground potential rise, step-andtouch voltages defined by the ANSI/IEEE Standard 80-2000, the
authors proposed a cost function, including diameter and space
between conductors; number, length and diameter of rods; depth
of grid burring; and different costs of material, excavation, and
welding effects.