Siemens Bus Bar Protection 7SS5..

I am trying to simulate a bus zone fault on a distributed Siemens bus bar protection system with central unit type 7SS522..The bay units are Siprotec 3 devices.

I connected only one line bay to the bus bar; that is after closing the Bus bar dis-connector and the Circuit breaker.

I then injected single phase current into the bay unit assigned to the line connected to the bus bar. (This bus has a total of 5 bays including a bus section). The central unit accurately measures a differential current equal to the injected current; but then, blocks tripping with a message 'Error with Block'. The current supervision alarm comes up as well. It appears the bus bar system 'knows' the 'fault' is not real!

- Could it be some logic blocking the trip?

- Could it be that because it is only one bay connected to this bus, he system is blocking the trip command?

- Or could it be the bus bar protection is not functioning?