Abstract: Service conditions, electrical ratings, thermal ratings, and testing requirements are defined for relays and relay systems used to protect and control power apparatus. This standard establishes a common reproducible basis for designing and evaluating relays and relay. The teaching text describes complex procedures for parameterization of overcurrent, differential, and distance protection relays from the company SEL, a theoretical basis for protection relays, description, and connection of individual parts of protection relays. The following obtains instructional. Keywords: Radial feeder, Protective Relay, power system protection, over Current, Earth fault, Time Setting Multiplier (TSM), Plug Setting Multiplier (PSM). INTRODUCTION The function of protective relaying is to cause the quick removal from service of any element of a power system when it. Many important issues, such as coordination of settings, operating times, characteristics of relays, mutual coupling of lines, automatic reclosing, and use of communication channels, are examined. They play a key role in power system protection. It emphasizes the importance of impedance in determining relay actions during faults in transmission lines, and outlines the experimental setup and.