The protection relay is the first line of defense in a substation, ensuring the stability, reliability, and safety of the power system. From basic overcurrent relays to advanced digital devices, each type plays a unique role in fault detection and isolation. When it detects abnormal conditions—such as overcurrent, short circuit, or voltage instability—it sends a trip signal to the circuit breaker, isolating the faulted. To ensure the reliability and efficiency of substations, various types of relays and control/monitoring equipment are used. Types of Protective Relays: Protective relays are categorized by their mechanism (electromagnetic, static, mechanical) and function. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. : 4 The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as. A protection relay is a crucial component of electrical systems that safeguard infrastructure, employees, and equipment from electric problems and malfunctions. It functions as a watchdog by constantly surveying multiple system components including voltage, current, frequency, and phase angle. Its main purpose is to safeguard electrical equipment like transformers, generators, and transmission lines from damage due to.