**Abstract**

In recent years, the development of smart grids for power distribution and the increasing usage of 5G communication networks have played a large impact on the resilience and reliability of grounding systems. Unexpected electromagnetic coupling between a communication tower and the one used for the electric power networks may pose a threat to the suitable performance of either system as one must assure that electromagnetic compatibility together with unexpected transient issues is within reasonable parameters. This requires wideband modeling of a grounding system, typically carried out using numerical approaches based on the Method of Moments. This modeling is implied in numerous segments to represent the conductors involved and the numerical solution of a double integral for each one of these segments. The modified nodal formulation used to obtain system voltages and branch currents is first solved in the frequency domain, leading to a heavy computational burden and a time-consuming simulation. This chapter briefly reviews the procedure used to model grounding grids and presents some results to illustrate the typical behavior. Afterward, a more complex system comprising a case of electromagnetic coupling is then analyzed to illustrate the impact of nearby grounding grids.

**Keywords:** grounding systems, method of moments, frequency domain analysis, transient response, computational methods for electromagnetism

#### **1. Introduction**

This chapter focuses on the transient analysis of grounding systems and the impact that the associated responses might have with respect to the electromagnetic compatibility in nearby power apparatuses, installations, and people. It is assumed that the reader is familiar with the electromagnetic field theory in both frequency and time domains and some mathematical tools such as Method of Moments [1] and Numerical Laplace Transform [2–6].

The development of smart grids for electric power distribution and the widespread use of 5G communication networks will demand an accurate, efficient, and resilient grounding system to avoid electromagnetic compatibility issues such as interference or noise in apparatuses due to poor power quality, that is, harmonic distortion in voltages and currents. Furthermore, an injected current due to

**Figure 1.** *Schematic of an industrial facility with a simple bare conductor acting as the grounding system.*

lightning-related phenomena may lead to a ground potential rise (GPR) that could damage several devices and play an important aspect in the reduction of personal safety in the area surrounding the apparatuses. The most common approach to overcome these possible challenges is to design a feasible, reliable, and efficient grounding system. Therefore, it is of utmost importance to properly understand the transient behavior of a given grounding system in an electrical power or communication installation and its interaction with its surroundings, be it a sensitive electronic device, another grounding system, people, or even the induced voltage at ground level. In general terms, the main function of a grounding system is to provide a pathway with the lowest possible impedance for faulty currents, leading to the least possible voltage increase at the injection point and in its surrounding area. By faulty current, one may consider the one associated with phenomena such as lightning, switching, misoperation, and more recently, the combined harmonic currents related to the presence of power electronic converters in the electric power network.

To illustrate the general idea, consider the schematic presented in **Figure 1**, where a small facility has a rather simple grounding system. It consists of a bare horizontal conductor buried near the ground surface, for example, 0.5 m. The conductor should be long enough that its longitudinal current *IL* decays as smoothly as possible, preferably monotonically decreasing, and reaches to zero before reaching the end of the conductor. The bare conductor is open-ended at the far end. The shunt current *IT* represents the injected current in the soil, and it is the main contributor to the voltage increase in the surrounding area. Both currents are distributed in nature, and to account for their behavior, one must consider the frequency dependency of conductor and ground. Even in this simple scenario, one needs to divide the conductor into small segments so the Method of Moments can be applied, thus leading to a large order for all the matrices involved. The segmentation of any given conductor to very small segments is also needed for representing the electromagnetic propagation throughout the conductor and surrounding media.

In actual installations, the scenario is even direr as more complex configurations need to be considered. Transmission towers will demand a counterpoise configuration involving an arrangement of conductors that are not parallel for some extension of their lengths. In some scenarios, there are horizontal and vertical conductors to be considered. **Figure 2(a)** depicts the basic structure of a counterpoise for grounding a power transmission tower. Electric power substations demand a grounding grid, which is complex and large in dimensions, representing a challenge for an accurate simulation of transient behavior. **Figure 2(b)** shows a nonuniform grounding grid typically found in electric power substations.

*Modeling Grounding Systems for Electromagnetic Compatibility Analysis DOI: http://dx.doi.org/10.5772/intechopen.100454*

**Figure 2.**

*Two grounding grids configuration. (a) Counterpoise configuration for overhead line transmission towers and (b) nonuniform grounding grid.*

Although the grounding grid is an element to ensure equipment and people safety, it may have some drawbacks. For instance, an unexpected electromagnetic coupling between a communication tower and the one used for the power network may pose a threat for the suitable performance of electronic equipment as one must assure that electromagnetic compatibility, together with unexpected transient issues, is within reasonable parameters.

In the following sections, we present a mathematical approach based on the Method of Moments to accurately represent a given grounding system. It is a formulation suitable for the analysis related to electromagnetic compatibility issues, as well as the associated current and voltage transient analysis. It is based on the frequency domain formulation of a modified nodal admittance matrix with time responses being obtained using the Numerical Laplace Transform.
