Short Circuit Unit. B6000 generator protection system is designed for protection of parallel working AC generators. Besides reverse power and overload protection, this system also includes short circuit protection. Optionally, the system can be equipped with frequency detection. The relay can be provided with two extra overcurrent/time units which can be used for alarms and/or tripping of non-essential load. It is also possible to obtain normally energized or normally de-energinzed output relay functions for each of the output relays. Short circuit unit. by Littelfuse | Gross Automation