Protection is the branch of electric power engineering concerned with the principles of design and operation of equipment (called "relays" or "protective relays") which detect abnormal power system conditions and initiate corrective action as quickly as possible in order to. Protection is the branch of electric power engineering concerned with the principles of design and operation of equipment (called "relays" or "protective relays") which detect abnormal power system conditions and initiate corrective action as quickly as possible in order to. Protection Measurements and Controls This chapter presents some basic control configurations for protective systems. The method of connecting protective devices into the power system are presented, and some of the problems of making accurate observations of system conditions will be explored. It functions as a watchdog by constantly surveying multiple system components including voltage, current, frequency, and phase angle. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. They are activated by means which are not dependent on a continual AC supply. They include both mechanical induction disks in older systems, and more. Power System Protective Relays: Principles & Practices Protective Relays - Technical Seminar Nov 2016 - Copyright: IEEE 1 Power System Protective Relays: Principles & Practices Presenter: Rasheek Rifaat, P. Eng, IEEE Life Fellow IEEE/IAS/I&CPSD Protection & Coordination WG Chair Jacobs Canada. An electrically operated switch like a relay plays a key role in controlling an electrical circuit through an independent low-power signal, otherwise used where a number of circuits should be controlled through the single signal.