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Bus zone protection is a unit protection (meaning a protection with a restricted zone, therefore does not need to be coordinated with other time based protections) specifically for MV/HV switchgear protection of Busbars and Circuit Breakers. Generally always Circuit Breakers are included in the zone of Busbar protection.
It provides stability in case of problems with disconnectors auxiliary contacts (stuck contacts or wiring problems). Ir relies on the feeder currents in the busbar.
Disconnectors positions are not required.
There is no selectivity using check zone. It's usefully because it prevents external faults to be considered as a busbar fault.
