Securing protection relays is no longer just a best practice; it's absolutely essential for ensuring the resilience of both transmission and distribution power grids. Substations are critical nexus points in the power grid, transforming high-voltage electricity to ensure its safe and efficient delivery from power plants to millions of end-users. At the core of a modern substation lies the protection relay: an intelligent electronic device (IED) that plays a. The global energy transition is ushering in a new era of power electronic-dominated grids (PEDGs), to complement the increase in the widespread integration of renewable sources like wind and solar. Fingrid's application guideline for relay protection presents the operating principles of the relay protection in Fingrid's 110, 220 and 400 kV power networks and the requirements for operation of the. A protective relay is an intelligent device that senses abnormal electrical conditions, such as overcurrent, under-voltage, or frequency deviations. It initiates the operation of circuit breakers to isolate the affected section. This prevents damage to equipment, reduces downtime, and safeguards. Generator protection covers: phase-to-phase short circuits in stator windings, stator ground faults, inter-turn short circuits in stator windings, external short circuits, symmetrical overload, stator overvoltage, single- and double-point grounding in the excitation circuit, and loss of excitation.