2 Functions
218
7SD610 Manual
C53000-G1176-C145-4
Figure 2-92 Principle of the trip circuit supervision with one binary input
TR Trip relay contact
CB Circuit breaker
TC Circuit breaker trip coil
Aux1 Circuit breaker auxiliary contact (NC contact)
Aux2 Circuit breaker auxiliary contact (NO contact)
U-CTR Control voltage for trip circuit
U-BI Input voltage of binary input
R Equivalent resistor
UR Voltage across the equivalent resistor
During normal operation, the binary input is activated (logical condition „H“) when the
trip contact is open and the trip circuit is intact, because the supervision circuit is
closed either by the circuit breaker auxiliary contact (if the circuit breaker is closed) or
through the equivalent resistor R. Only as long as the trip contact is closed, the binary
input is short-circuited and thereby deactivated (logical condition „L“).
If the binary input is permanently deactivated during operation, an interruption in the
trip circuit or a failure of the (trip) control voltage can be assumed.
The trip circuit monitoring does not operate during system faults. A momentary closed
tripping contact does not lead to a fault indication. If, however, other trip relay contacts
from different devices are connected in parallel in the trip circuit, the fault indication
must be delayed by Alarm Delay (see also Figure 2-93). After clearance of the
failure in the trip circuit, the fault message automatically resets with the same time
delay.
Figure 2-93 Logic diagram for trip circuit supervision with one binary input
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