Development of a new methodology for measurements of earth resistance, touch and step voltages within urban substations

This paper discusses the development of a new methodology for measurements of earth resistance and touch and step voltages in ground mesh of urban power substations. The main challenge of the work is to find a feasible solution for performing earth resistance measurements from short distances, given that this is the condition actually found in the majority of urban substations. A test field with four ground mesh units of different geometric configurations was implemented and used for performing numerous measurement tests. Based on all the data collected and analysis of the measurement results, a mathematical model was developed to estimate and predict the correct distance in order to obtain earth resistance measurements from short distances, the PRED Method - Polynomial Regression from Database Method. A discussion of the proposed method, as well as analysis of its accuracy and susceptibility to external interference is performed, in addition to its validation in real substations, so as to prove the efficiency and applicability of the proposed method. (C) 2017 Elsevier B.V. All rights reserved.