ABB REB670 Applications Manual page 211

1MRK 505 337-UUS -
Application manual
Protection
operate time
Normal t
Retrip delay t1
The fault
occurs
Trip and Pickup
CCRBRF
(50BF)
ANSI05000479 V3 EN
Figure 90: Time sequence
t2MPh: Time delay of the back-up trip at multi-phase initiate. The critical fault clearance
time is often shorter in case of multi-phase faults, compared to single phase-to-ground
faults. Therefore there is a possibility to reduce the back-up trip delay for multi-phase
faults. Typical setting is 90 – 150 ms.
t3: Additional time delay to t2 for a second back-up trip TRBU2. In some applications
there might be a requirement to have separated back-up trip functions, tripping different
back-up circuit breakers.
tCBAlarm: Time delay for alarm in case of indication of faulty circuit breaker. There is a
binary input 52FAIL from the circuit breaker. This signal is activated when internal
supervision in the circuit breaker detect that the circuit breaker is unable to clear fault. This
could be the case when gas pressure is low in a SF6 circuit breaker, of others. After the set
time an alarm is given, so that actions can be done to repair the circuit breaker. The time
delay for back-up trip is bypassed when the 52FAIL is active. Typical setting is 2.0
seconds.
tPulse: Trip pulse duration. This setting must be larger than the critical impulse time of
circuit breakers to be tripped from the breaker failure protection. Typical setting is 200 ms.
cbopen
t after re-trip
cbopen
t
BFPreset
Minimum back-up trip delay t2
Critical fault clearance time for stability
Section 7
Current protection
Margin
Time
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