2.11.2 Circuit Breaker Fail Logic
CB Fail Enable
If in1 is less than
In1<
Ext CBF Initiated
Any Trip
If I in all Phase is
less than I<
52(B)
Protection Reset
1
S
Q
RD
&
&
&
CBF Timer
&
CBF Reset
Figure 11: CB Fail Logic
CBF elements CB Fail Timer can be configured to operate for trips triggered by protection elements
within the device or via an external protection trip. The latter is achieved by allocating one of the opto-
isolated inputs to CBF Init signal using the I/O Mask feature.
It is possible to reset the CBF from a breaker open indication from a protection reset. In these cases
resetting is only allowed provided the undercurrent elements have also been reset. The resetting
options are summarised in the following table:
CBF function Reset options
CBF function will reset when the phase currents and earth current is less than
set current
CB Open + I<
CBF function will reset when both conditions are satisfied:
• CB is open (i.e. CB(52B) status is active)
• The phase currents and earth current is less than set current
Prot Reset + I<
CBF function will reset when both conditions are satisfied:
• Protection is reset
• Phase currents and earth current is less than set current
CB Open CBF function will reset when CB is open (i.e. CB(52B) status is active)
The Remove I> Start and Remove IN> Start settings are used to remove starts issued from the
overcurrent and earth elements respectively following a breaker fail time out. The start is removed
when the cell is set to 'Enabled'.
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