ABB RELION REX640 Technical Manual page 1172

Protection related functions
CCBRBRF is initiated by operating different protection functions or digital logics
inside the protection relay. It is also possible to initiate the function externally
through a binary input.
CCBRBRF can be blocked by using an internally assigned signal or an external signal
from a binary input. This signal blocks the function of the breaker failure protection
even when the timers have started or the timers are reset.
The retrip timer is initiated after the start input is set to true. When the pre-defined
time setting is exceeded, CCBRBRF issues the retrip and sends a trip command, for
example, to the circuit breaker's second trip coil. Both a retrip with current check
and an unconditional retrip are available. When a retrip with current check is chosen,
the retrip is performed only if there is a current flow through the circuit breaker.
The backup trip timer is also initiated at the same time as the retrip timer. If
CCBRBRF detects a failure in tripping the fault within the set backup delay time,
which is longer than the retrip time, it sends a backup trip signal to the chosen
backup breakers. The circuit breakers are normally upstream breakers which feed
fault current to a faulty feeder.
The backup trip always includes a current check criterion. This means that the
criterion for a breaker failure is that there is a current flow through the circuit
breaker after the set backup delay time.
Figure 665: Typical breaker failure protection scheme in distribution substations
5.2.7 Signals
1172
REF 615
1MRS759142 F
REF 615
REF 615
Technical Manual
REF 615
REX640