This book focuses on numerical methods for grounding problems in substation grounding systems, which are rooted in horizontal multilayered earth models. The book discusses both theories and engineering applications and provides case studies to verify the accuracy of the methods introduced. Up to ten horizontal multilayered soil models were considered. This book employs numerical algorithms for Galerkin method, including Galerkin method of moments, Galerkin boundary element method, and hybrid algorithms based on a variety of basis functions that have emerged as a result of simplifying Galerkin method of moments. These numerical methods include both frequency and time domain algorithms that can be used to numerically simulate transient and steady state grounding problems in substation grounding grids. The most outstanding feature of this book is the incorporation of the frequency- and time-domain quasi-static complex imaging method (QSCIM) for point current sources in layered conducting media and its closed-form Green function, as well as analytical algorithms for calculating the spatial two-dimensional line integrals of mutual impedances and inductances into numerical algorithmic modeling of electromagnetic fields, which greatly improves computational speed and accuracy.