Circuit Breaker Failure Protection
127
7SS52 V4 Manual
C53000-G1176-C182-1
BF I< The parameter BF I< (XX16/CU) is used to activate and deactivate the low-current
mode.
With setting ON the low-current mode is activated.
With setting OFF the low-current mode is deactivated.
The low-current mode can be used together with the following settings:
• BF BI MODE (XX14/CU) with and without supervision
• BF OP MODE (XX15/CU) Breaker failure operating mode, in the settings:
− I> query
− TRIP repetition/I> query:
− Unbalancing
− TRIP repetition/Unbalancing
The low-current mode cannot be used together with the following setting external
of the parameter BF OP MODE (XX15/CU).
TRIP REP. MODE The parameter TRIP REP. MODE (XX17/CU) is used to select the operating mode
for TRIP repetition with 1-pole initiation.
With setting single-channel the 1-pole TRIP repetition will be generated. The
feeder current of the initiating phase and the earth fault current must exceed for this
the threshold I> BF-EF (XX19/CU) (ILx & IE).
With setting 3pole a 3-pole TRIP repetition will be generated. The feeder current of
the initiating phase and the earth fault current must exceed for this the threshold I>
BF-EF (XX19/CU) (ILx & IE).
A prerequisite for a TRIP repeat is that the curcuit breaker is ready for operation. That
means a binary input ">CB not ready" (FNo. 7619/BU) is not active.
T-BF-1P The parameter T-BF-1P (XX20/CU) is used to delay for 1-pole faults the TRIP com-
mand and the transfer trip signal issued by the breaker failure protection.
It is recommended for the single-stage breaker failure protection to set this parameter
to twice the circuit breaker trip time.
With two-stage breaker failure protection two time stages pick up: T-TRIP repeat
(XX25/CU) and T-BF-1P (XX20/CU). The tripping of the affected bus zone takes
place after the second stage has been processed. The parameter T-BF-1P (XX20/
CU) is then to be set higher than the sum of the delay times set with parameters T-
TRIP repeat (XX25/CU) and Tmin TRIP (6106/CU) in order to avoid premature
or unnecessary trippings of the bus zone.
T-BF-mP The parameter T-BF-mP (XX21/CU) is used to delay for multipole faults the TRIP
command and the transfer trip signal issued by the breaker failure protection.
It is recommended for the single-stage breaker failure protection to set this parameter
to twice the circuit breaker trip time.
With two-stage breaker failure protection two time stages pick up: T-TRIP repeat
(XX25/CU) and T-BF-mP (XX21/CU). The tripping of the affected bus zone takes
place after the second stage has been processed. The parameter T-BF-mP (XX21/
CU) is then to be set higher than the sum of the delay times set with parameters T-
TRIP repeat (XX25/CU) and Tmin TRIP (6106/CU) in order to avoid premature
or unnecessary trippings of the bus zone.
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