Summarising the present day methods for the production, transmission and distribution of electric energy, this text identifies the four main areas of protection. After giving a comprehensive study of power system analysis, focusing on the relevant circuit theorems, the author then goes on to define and illustrate the design of commercial relays. This in-depth focus and mathematical explanation of commercial relays is followed by a detailed account of relay application in system protection. Written by an expert in the protection field, this book will present the latest information on modern protection relays and will bring readers up to date with all recent developments.