ABB REF610 Feeder Protection RelayDescription The REF610 is primarily used for the protection of incoming and outgoing feeders in distribution substations. It is suitable for resistance earthed and solidly earthed power systems and can also be employed in marine and offshore environments. Its compact, plug in design facilitates easy installation, commissioning, and maintenance. Specifications Protection Functions: Overcurrent protection (low set, high set, and instantaneous stages).