A protective relay operates by continuously monitoring electrical parameters, detecting abnormalities, making decisions, and triggering circuit breakers to isolate faulty sections. This process helps protect equipment, maintain power system stability, and ensure safety for. Protective relays and devices have been developed over 100 years ago to provide “lastline”of defense for the electrical systems. They are intended to quickly identify a fault and isolate it so the balance of the system continue to run under normal conditions. Three fundamental components required for each circuit breaker. Types of Protective Relays: Protective relays are categorized by their mechanism (electromagnetic, static, mechanical) and function. Relion protection and control relays for several application reduce complexity.