ABB REB670 Series Applications Manual page 193

1MRK 505 370-UEN D
The fault
occurs
IEC18000908 V1 EN-US
Figure 106: Time sequence
t3 : Additional time delay to t2 for a second backup trip TRBU2. In some applications there
might be a requirement to have separated backup trip functions, tripping different backup
circuit breakers.
tCBAlarm : Time delay for alarm in case of indication of faulty circuit breaker. There is a binary
input CBFLT 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. After the set time an alarm is given, so that
action can be done to repair the circuit breaker. The time delay for backup trip is bypassed
when the CBFLT 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.
tStartTimeout : When one of the two "Follow Modes" is used, there is a settable timer
tStartTimeout which will block the external START input signal when it times-out. This will
automatically also reset the
command. At the same time the STALARM output from the function will have logical value one.
To reset that condition external START signal shall be removed. This is done in order to
prevent unwanted operation of the breaker failure function for cases where a permanent
START signal is given by mistake (e.g.due to a fault in the station battery system). Note that
any backup trip command will inhibit running of
Busbar protection REB670
Application manual
Protection
operate time
Normal t
cbopen
Retrip delay t1 t
cbopen
Minimum back-up trip delay t2
Critical fault clearance time for stability
Trip and Start
CCSRBRF
t1 and t2 timers and consequently prevent any backup trip
after re-trip
t
BFPreset
Margin
tStartTimeout timer.
Current protection
Time
IEC18000908-1-en.vsdx
Section 7
187