ThetaInit
: Heat content before activation of the function. This setting can be set a little
below the alarm level. If the transformer is loaded before the activation of the
protection function, its temperature can be higher than the ambient temperature. The
start point given in the setting will prevent risk of no trip at overtemperature during the
first moments after activation.
ThetaInit:
is set in % of the trip heat content level.
Warning
: If the calculated time to trip factor is below the setting
Warning
a warning
signal is activated. The setting is given in minutes.
9.9
Breaker failure protection CCRBRF(50BF)
IP14514-1 v6
9.9.1
Identification
M14878-1 v5
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Breaker failure protection, 3-phase
activation and output
CCRBRF
3I>BF
SYMBOL-U V1 EN-US
50BF
9.9.2
Application
M13916-3 v7
In the design of the fault clearance system the N-1 criterion is often used. This means
that a fault needs to be cleared even if any component in the fault clearance system is
faulty. One necessary component in the fault clearance system is the circuit breaker. It
is from practical and economical reason not feasible to duplicate the circuit breaker for
the protected object. Instead a breaker failure protection is used.
Breaker failure protection, 3-phase activation and output (CCRBRF, 50BF) will issue a
back-up trip command to adjacent circuit breakers in case of failure to trip of the
“normal” circuit breaker for the protected object. The detection of failure to break the
current through the breaker is made by means of current measurement or as detection
of remaining trip signal (unconditional).
CCRBRF (50BF) can also give a re-trip. This means that a second trip signal is sent to
the protected circuit breaker. The re-trip function can be used to increase the
probability of operation of the breaker, or it can be used to avoid back-up trip of many
breakers in case of mistakes during relay maintenance and testing.
1MRK 504 163-UUS A
Section 9
Current protection
Transformer protection RET670 2.2 ANSI
571
Application manual
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