Fundamentals of Ground Grid Design

The grounding system is an essential part of both high- and low-voltage electrical power networks. Design of a ground grid is part of the overall design of a substation. The ground rods are driven in and the ground grid constructed before the surface layer of gravel is poured and the above-ground portions of the substation constructed. The most important factor in terms of overcurrent phenomena is the sizing of the ground grid conductors. The conductors of a ground grid should be designed for a particular maximum fault current, X/R ratio, and clearing time. This chapter illustrates a design data for ground grid example from IEEE standard 80. This calculation is performed using improved and more uniform calculation procedures than those used in the referenced standard.