Frequency Dependent Characteristics of Grounding Systems

This paper presents models for the computation of frequency characteristics and transient response of power grounding systems. The methodology can accommodate any configuration of a grounding system comprising rectilinear conductors. The approach is based on transmission line concepts. Finite element analysis is employed to model the constituent parts of a grounding system. The grounding system is segmented into short lengths of earth embedded electrodes which are characterized as lossy transmission lines with distributed inductance, capacitance, series resistahce, resistance to earth, and mutual coupling to any other finite element of earth conductors. The parameters of the short earth embedded electrodes are computed by solution of Maxwell's equations and assuming quasi-static conditions. The paper presents a validation procedure which is based on comparison of analysis results to test results obtained at BPA. The model is applicable for transient phenomena comprising a wide range of frequencies. Results are presented which illustrate the properties of grounding systems to low as well as high frequency transients.