Similar values are stated for overhead lines. A suitable setting can be about 15°C
(59°F) below the trip value.
ReclTemp: Temperature where lockout signal LOCKOUT from the protection is
released. When the thermal overload protection trips a lock-out signal is activated.
This signal is intended to block switch in of the protected circuit as long as the
conductor temperature is high. The signal is released when the estimated temperature
is below the set value. This temperature value should be chosen below the alarm
temperature.
6.9 Breaker failure protection 3-phase activation and
output CCRBRF
6.9.1 Identification
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Breaker failure protection, 3-phase
activation and output
CCRBRF
SYMBOL-U V1 EN
50BF
6.9.2 Application
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 component. Instead a breaker failure protection is used.
Breaker failure protection, 3-phase activation and output (CCRBRF) 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 component. 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 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 test.
1MRK 505 291-UEN A Section 6
Current protection
133
Application manual
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