Although the substation ground grid is to be located within a rectangle of 63 m ×84 m (5292 m2), for the initial design assessment it may be expedient to assume a square 70 m × 70 m grid with no ground rods. Consequently, the area occupied by such a grid is A = 4900 m2. An average soil resistivity of 400 Ω-m is assumed, based on soil resistivity measurements.