I< current set
0.5 to 4
&
I> current set
0.5 to 4
&
&
CB Fail 3 timer
0 to 10 secs
CB Fail 4 timer
0.04 to 10 secs
CB Fail 4 timer - CB Fail 3 timer
Back trip terminal-
a
ssociated adjacent
zone if CB failure is
bus coupler
V00702
Key:
&AND gate
Setting cell
Setting value
Timer
CBF Retrip Tn
L
ocal retrip
CBF Bcktrip Tn
CBF Bcktrip Zn
E
xternal CBF trip Zx
Ext CBF Zn
E
xternal trip signal
Ext CBF Init Tn
Internal DDB
E
xternal DDB
Figure 37: CBF initiated by external signal
If the faulty circuit breaker is on a feeder, a local retrip can be issued if CBF Retrip Tn is mapped to an
appropriate output in the PSL. This may not be necessary if the external protection provides CBF.
If the fault is on a busbar coupler circuit breaker, the protection tries to clear the fault by asserting the CBF
Bktrip Tn
signals to trip all adjacent circuit breakers. If this fails to clear the fault, trip all zones by mapping
the CBF Bktrip Zn DDBs to appropriate outputs in the PSL.
4.3 CB FAIL SETTINGS
Menu Text Col Row Default Setting Available Options
Description
GROUP 1
CB FAIL & I<
45 00
This column contains settings for Circuit Fail and Under Current.
BREAKER FAIL 45 01
The settings under this sub-heading relate to Circuit Breaker Fail (CB Fail) settings
CB Fail 1 Status 45 02 Enabled 0 = Disabled or 1 = Enabled
This setting enables or disables the first stage of the CB Fail protection.
CB Fail 1 Timer 45 03 0.2 From 0s to 50s step 0.01s
This setting sets the first stage CB Fail timer in which the CB opening must be detected.
CB Fail 2 Status 45 04 Disabled 0 = Disabled or 1 = Enabled
This setting enables or disables the second stage of the CB Fail protection.
CB Fail 2 Timer 45 05 0.4 From 0s to 50s step 0.01s
This setting sets the second stage CB Fail timer in which the CB opening must be detected.
Volt Prot Reset 45 06 CB Open & I<
0=I< Only
1=CB Open & I<
2=Prot Reset & I<
MiCOM P747 Chapter 5 - Protection Functions
P747-TM-EN-1 113
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