The grounding grid plays a vital role in the safe and stable operation of an electrical system. To reduce the equipment damage and electric shock risks, an effective ground grid design for the system is necessary. In this paper, the PEEC method for the lossy ground is adopted to give a comprehensive analysis of the electric potential distribution around grounding grids under ground-fault conditions. The influence of the grounding structure, ground depth, and soil conductivity is discussed. The relationship between grounding grids structure and the step/transfer voltage are studied. This will benefit the grounding system design to guarantee electrical safety.