Calculating Grounding-Electrode Impedance Using Fall-of-Potential and Impedance Methods

This example provides a real-world application (which could be measured in practice) for students in a numerical analysis class studying the finite-difference methods. The Impedance Method is very similar to the classical finite-difference method. In this paper, it is used to model single- and double-grounding electrode systems for residential construction in various types of soil. These models are used to conduct a numerical electrode-potential test, and to calculate the Earth impedance of simple or dual-grounding electrode systems in two dimensions to determine the theoretical efficacy of the grounding system. Depending on the type of soil and the distance between the grounding electrodes, the second electrode mayor may not sufficiently ground the system. Since many of our students have some experience with residential or agricultural electrical systems, this application provides motivation and interest. It also provides an opportunity to introduce the National Electrical Code in an electrical-engineering context.