CYG PRS-7367 - Page 80

Protection Functions
72 PRS-7367
When the external mechanical equipment has checked the CB is failure, it means that when the
50BF_CBF=1 and last for 50BF_Fault_T, the 50BF_Alm signal will be sent. A typical value of
50BF_Fault_T is 5 s.
3.7.2.8 Current Detector Logic
The current detector function is used to check the non-directional instantaneous overcurrent relay pickup
and resetting condition. The setting 50BF_QuickRet_Ena can be used and enabled to test fast-resetting
function.
Ia>50BF_Cur_StrANA
Ib>50BF_Cur_StrANA
Ic>50BF_Cur_StrANA
1
I0>50BF_ResCur_StrANA
&
SET
50BF_CurRes_Ena
I2>50BF_NegCur_StrANA
&
SET
50BF_CurNeg_Ena
1ms
5ms
SIG50BF_CurDet
Ia>50BF_DeaCur_StrANA
Ib>50BF_DeaCur_StrANA
Ic>50BF_DeaCur_StrANA
1
50BF_DZTrBu_Ena
SET
&
Figure 3.7-8 Current detection logic
3.7.2.9 Time delay setting note
The 50BF time delay should consider the CB physical condition, the characteristic should be DF.
The minimum time delay for the all trip can be estimated as:
CBOpen BF_Reset Margin
50BF_ ReTr _ T t +t +t
CBOpen BF_Reset Margin
50BF_ _ T t +t +tBFTr 
ReTr CBOpen BF_Reset Margin
50BF_ BFTrBu _T t +t +t +t
CBOpen BF_Reset Margin
51BF_ DZTrBu _ t +t +tT 
Circuit breaker operating time (t
CBOpen
), which is the time between activating the trip command for
the circuit breaker trip coil and CB reaching the open position
• Reset time (t
BF_Reset
) of current detection, which is the time between the moment when the circuit