This book is based on the research conducted by the authors over a substantial period in the field of power-switching apparatuses. It encompasses recent advances and future development trends. Considering practical experience, this book focuses on theoretical studies to establish a framework for computing methodology for switchgear by accurately modeling the key functional components of switchgear products. The book provides case studies closely related to practical engineering applications. The book consists of seven chapters. Chapters 1 to 4 focus on developing mathematical models and their relevant theories and solution methods for arc simulation. These chapters focus particularly on the post-arc period and the calculation and experimental verification of material properties used directly in arc simulation. Chapters 5 and 6 introduce methods for analyzing processes related to thermal performance, mechanical stability due to the Lorentz force, and the operation of switchgear operating mechanisms. Chapter 7 provides case studies relating to switching arcs. This book is intended for R&D engineers of power switching apparatuses, as well as for academics and postgraduate researchers in the fields of electrical discharges, thermal plasmas, gas-based switching technology, and other relevant disciplines.