Foundations in power systems act as grounding elements

Steel used in concrete foundations acts as a ground electrode as the concrete in soil behaves like a semiconducting medium. In power systems, the steel in the foundations is not insulated from the metallic superstructures, which are grounded through a laid ground conductor. Thus, steel in the foundations becomes part of the grounding system. Results of computations of ground resistance for about 100 different foundations found in power systems are presented. Dimensions of the equivalent vertical cylindrical conductor for various types of foundation are also given and evaluated. The concrete foundations are shown to play an important role in lowering the effective ground resistance of the installed grounding systems. The concrete foundations can carry a substantial amount of leakage and fault currents. Taking into account the ground resistance offered by the foundations in the design of a grounding system should result in a system that is safe and economical