A comparison among eight different techniques to achieve an optimum estimation of electrical grounding parameters in two-layered earth

This paper intends to compare the performance of eight techniques, based on five different methods, used to find the electrical grounding parameters of a two-layered earth (resistivities and thickness) corresponding to a specific mathematical model. Parameter estimation is carried out in such a way as to obtain an optimum fitting between the set of resistivity values measured in the field by means of Wenner´s Method, and those calculated from the mathematical model using such parameters. Firstly, the paper presents a review of the mathematical basis of five optimization methods used for the implementation of the different techniques subject to comparison. Secondly, the paper defines the implementation of the algorithms for the eight techniques. Three of them are of first order gradient type, one more of second order (Newton-method), the fifth one is based on the Levenberg-Marquardt method, the sixth one on the generalized inverse method, the seventh one on a quasi-Newton method and the last one on a mixed Newton-generalized inverse method. Algorithms are applied to six test cases and comparison of the results is shown. Furthermore, new algorithms to improve existing procedures are presented