In the ever-evolving field of protective relay technology, an engineer's personal preference and professional judgment are as important to power system protection as the physical relays used to detect and isolate abnormal conditions. This valuable reference was written by an expert who uses his insight to focus on probable power system failure modes and important characteristics of the protective relays used to detect these postulated failures. It presents useful new concepts in a way that is easier to understand because they are equally relevant to older, electromechanical and solid-state relays, and newer, more versatile microprocessor-based relays. This versatile text is ideal for new engineers to use as a tutorial before they open instruction manuals that accompany multifunction microprocessor-based relays. This book includes practical examples for many applications and offers guidance for more unusual ones.