2 Functions
158
7UM61 Manual
C53000-G1176-C127-3
If the binary input of the circuit breaker auxiliary contact is inactive, only the current
criterion is effective. The breaker failure protection cannot become active with a trip-
ping signal if the current is below the CIRC. BR. I> threshold.
Two-Channel
Feature
To increase security and to protect against possible disturbance impulses the binary
input for an external trip signal is stabilized. This signal must be present during the
entire period of the delay time, otherwise the timer is reset and no tripping signal is
issued. A redundant binary input “>ext.start2 B/F” is linked to further enhance
the security against unwanted operation. This means that no initiation is possible
unless both binary inputs are activated. The two-channel feature is also effective for
an “internal” initiation.
Logic If breaker failure is initiated, an alarm message is generated and a settable delay time
is started. If the pickup criteria are still fulfilled on expiration of this time, a redundant
source evaluation before fault clearing is initiated via a further AND combination
through a higher level circuit breaker.
A pickup drops off and no trip command is produced by the breaker failure protection if
• an internal start condition (CFC or BO3) or ">ext.start1 B/F" or ">ext.start2 B/F",
causing the pickup, drops off.
• a tripping signal of the protective functions still exists, whereas the current criterion
and the auxiliary contact criterion drop out.
The following figure shows the logic diagram for the breaker failure protection function.
The overall breaker failure protection can be enabled or disabled via parameters and
also blocked dynamically via binary input “>BLOCK BkrFail” (e.g. during a machine
protection check).
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