Protection relay testing and commissioning works are carried out to ensure the safe and correct operation of electrical systems from medium voltage to high voltage levels. During this process, relay settings, measurement accuracy, communication functions, and trip-close scenarios are verified through field and secondary injection tests. These tests guarantee that relays will trip the correct equipment at the right time during a fault, preventing nuisance tripping, unprotected operation conditions, and widespread power outages. By ensuring full system compatibility during the commissioning phase, the reliability, selectivity, and operational continuity of MV-HV facilities are enhanced.