Contents I. Introduction
Substation ground system serves to safety of personnel and as major equipment during earth faults, which has already deserved a long history considerable attentions [1]–[18]. As defined in IEEE Std. 80–2000 [19], basic substation safety assessment quantities including ground grid resistance, mesh touch potential, step potential and ground potential rise (GPR), should be limited as constraints in design for the sake of safety. Previous optimal ground design only used numerical calculation or “trail-and-error” [9]–[13], then different optimization modeling with corresponding optimization methods had been studied to count both safeness and cost [14]–[18]. Several commercial software [20]–[22] or self-developed software had also been developed [23].
