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. T
ypical 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. 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.
9.10 Stub protection STBPTOC (50STB)
IP14515-1 v3
9.10.1 Identification
M17108-1 v2
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Stub protection STBPTOC
SYMBOL-T V1 EN-US
50STB
9.10.2 Application
M12904-3 v5
In a breaker-and-a-half
switchyard the line protection and the busbar protection
normally have overlap when a connected object is in service. When an object is taken
out of service it is normally required to keep the diagonal of the breaker-and-a-half
switchyard in operation. This is done by opening the disconnector to the protected
object. This will, however, disable the normal object protection (for example the
distance protection) of the energized part between the circuit breakers and the open
disconnector.
1MRK 504 163-UUS A Section 9
Current protection
Transformer protection RET670 2.2 ANSI 575
Application manual
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