The ABB 1SDA051369R1 is a high-current, high-density feeder protection relay from ABB's Relion® product family, specifically a member of the REF615 series (or the closely related RET615 transformer protection series). The part number is a spare part/order code for a fully configured protection IED (Intelligent Electronic Device). It is engineered as a compact, versatile feeder management unit for comprehensive protection, control, measurement, and monitoring of medium-voltage (MV) distribution feeders in utility, industrial, and commercial power systems.