This book deals with the basics of protection theories of electric circuits as it explains the methods and tools of protection using all types of relays such as electrodynamics, static, and digital relays and timers. The discrimination principles for relays or protective circuits or for protective systems and gears for a united power network are considered and the development of protection begins at small element passing by the complete circuits for a main element in the power system and ending at the adaptation of all circuits together for a whole power system. the motors and cables are...