Siemens 7SC80 Manual page 319

Feedback information of the auxiliary status of the circuit breaker is evaluated, depending 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 inter-
mediate position. If valid, this information can be used for a proper initiation of the breaker failure protection
function.
The logic diagram illustrates the monitoring of the circuit breaker's auxiliary contacts.
[7sj80-erzeug-svs-int-sign, 1, en_US]
Figure 2-106
Logic
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 pickup are still met, a trip signal is issued to a superordinate
circuit breaker. Therefore, the trip signal issued by the 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 the criteria that led to the pickup are no longer met when the time delay has elapsed, such pickup thus
drops out and no trip signal is issued by the breaker failure protection function.
To protect against nuisance 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 trip signal is issued.
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017
Logic diagram for breaker failure protection, monitoring of the circuit-breaker auxiliary
contacts
Functions
2.18 Breaker Failure Protection 50BF
319