This presentation reviews the established principles and the advanced aspects of the selection and application of protective relays in the overall protection system, multifunctional numerical devices application for power distribution and industrial systems, and addresses. This presentation reviews the established principles and the advanced aspects of the selection and application of protective relays in the overall protection system, multifunctional numerical devices application for power distribution and industrial systems, and addresses. Engineering use: Relays are used on feeders, transformers, buses, motors, generators, and transmission lines to protect equipment and improve system reliability. What controls it: Relay performance depends on the protected zone, CT/PT inputs, pickup settings, time delay, breaker clearing time, trip. This Modern Power System Protective Relaying training course has been designed to provide a clear and perfect understanding of power system protection schemes and devices, including protection relays, fuses, circuit breakers, and other protective devices. In modern power systems, nowadays. To introduce all kinds of circuit breakers and relays for protection of Generators, Transformers and feeder bus bars from Over voltages and other hazards. To describe neutral grounding for overall protection. They are intended to quickly identify a fault and isolate it so the balance of the system continue to run under normal conditions. This prevents damage to equipment, reduces downtime, and safeguards. Protective relays can be classified based on their operating principle, construction, or function: 1. Based on Operating Principle Electromechanical Relays: Work using moving parts and electromagnetic forces (traditional relays). Static Relays: Use electronic components without moving parts.