Siemens siprotec SJ62 User Manual page 260

Logic
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
derived from the circuit breaker auxiliary contact must be fulfilled. Only in case the in-
formation retrieved by means of the auxiliary contact criterion is contradictory and
therefore erroneous, the current criterion will be used as unique criterion.
The current criterion is met if at least one of the three phase currents exceeds a set-
table threshold (BkrClosed I MIN) (see Section 2.1.3.2, margin heading "Current
Flow Monitoring"). This pickup threshold is also used by other protective functions.
Evaluation of the circuit breaker auxiliary contacts depends on the type of contacts,
and how they are connected to the binary inputs:
• Auxiliary contacts for circuit breaker "open" and "closed" are allocated,
• Only the auxiliary contact for circuit breaker "open" is allocated,
• Only the auxiliary contact for circuit breaker "closed" is allocated,
• No auxiliary contact is allocated.
Feedback information of the auxiliary contact(s) of the circuit breaker is evaluated, de-
pending on the allocation of binary inputs and auxiliary contacts. After a trip command
has been issued it is the aim to detect — if possible — by means of the feedback of
the circuit breaker's auxiliary contacts whether the breaker is open or in intermediate
position. If valid, this information can be used for a proper initiation of the breaker
failure protection function.
If breaker failure protection is initiated, an alarm message is generated and a settable
delay time is started. If once the time delay has elapsed, criteria for a pick-up are still
met, a trip signal is issued to a superordinate circuit breaker. Therefore, the trip signal
issued by the circuit breaker failure protection is configured to one of the output relays.
The following figure shows the logic diagram for the breaker failure protection function.
The entire breaker failure protection function may be turned on or off, or it can be
blocked dynamically via binary inputs.
If one of the criteria (current value, auxiliary contacts) that caused the breaker failure
scheme to pickup is no longer met when time delay elapses, pickup drops out and no
trip signal is issued by the breaker failure protection function.
To protect against spurious tripping due to excessive contact bounce, a stabilization of
the binary inputs for external trip signals takes place. This external signal must be
present during the entire period of the delay time, otherwise the timer is reset and no
tripping signal is issued.
2.16 Breaker Failure Protection 50BF
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