_Applied_  
_sciences_  
_Article_  
A Fast Calculation of Partially Corroded, Grounding-Resistive Electrode Electrical Parameters  
**[PERSON], [PERSON] \({}^{\star}\)\({}^{\copyright}\), [PERSON] \({}^{\copyright}\) and [PERSON]**  
Escuela Tecnica Superior de Ingenieria y Diseno Industrial, Universidad Politecnica de Madrid,  
20012 Madrid, Spain  
\({}^{\star}\) Correspondence: [EMAIL_ADDRESS]  
**Featured Application: The proposed model can be applied to the assessment of the electrical parameters of non-perfect conducting grounding electrodes that are partially affected by corrosion. **  
**Abstract: The calculation of the grounding resistance of electrodes built with partially oxidized non-perfect conductors is addressed in this paper. A model based on circuit analysis to account for internal resistance is used, while the oxidation or partial coating of the conductor surface is modeled using the concept of the equivalent radius of the coated electrode. From the proposed model, the values of the electrical parameters of the grounding electrodes, such as the grounding resistance and the step and touch potentials, are calculated for real electrodes affected by coating or corrosion and compared with those values under ideal conditions. The results show significant differences in certain configurations that may compromise the safety margins established by current regulations. **  
**Keywords: non-perfect conducting grounding electrodes; coated electrode equivalent radius; partially corroded electrode**  
**1. Introduction**  
Grounding systems are elements of an electrical installation of great importance for the protection of people and equipment [1]. When there is an electrical fault, the step and contact potentials must not exceed the values given in the current regulations, and the grounding resistance must be adjusted to the value of the potential acquired by the electrode in the case of a unitary fault current [2]. At the design stage, calculations are made taking into account several simplifying assumptions. Firstly, it is assumed that the conductors that are part of the grounding electrodes are perfect electrical conductors (PEC), that is, they do not have internal resistance. Second, the surface of these conductors is in intimate contact with the soil, so that it is treated as the interface between an ideal conducting medium, with no resistivity, and a conducting medium with a finite value of resistivity. Common additional assumptions are, for example, that the ground is semi-infinite and electrically homogeneous, the conductors that form part of the grounding electrode have a constant radius, or the fault current leaking to the ground does so at low frequency, called industrial frequency [3]. This paper embodies two substantial improvements to the most popular models to evaluate the electrical parameters of grounding electrodes, namely, the inclusion into the calculation of the internal resistance of conductors and the possible oxidation or coating of part of them. While the first does not present special difficulties to be taken into account in the well-known models, the second entails a formidable complication in the calculations unless some simple procedure makes it possible to evaluate the effect produced by the electrode coating. The necessary modifications on an initial model based on the Charge Simulation Method (CSM) are presented in this paper. These modifications take into account both the internal resistance of the conductors [4] and their possible affectation, in part or in its entirety, by corrosion [5]. The oxidation is modeled as a layer of a conductive material with high resistivity that completely covers part of the conductors. Additionally, the new model can also evaluate the effect of coating conductors with a layer of any conductive material with arbitrary resistivity. If the conductors are considered as cylindrical rods, the oxidation or coating effect of these conductors is modeled by replacing their geometric radius by the so-called Coated Electrode Equivalent Radius (CEER) [6].