In order to analyze the soil structure and to use the result to analyze the performance of grounding grids in substation, this paper presents a self adaptation sampling scheme when complex image method is used to approach Green s function in multi-layer soil.

By numerous calculations about grounding network in multi-layer soils with given suitable condition for simplification of soil model,and carrying out combined analysis about the grounding system design,the conclusion obtained was coincided with that concluded from simulation experiment in the laboratory.