2 Functions
394
7SD5 Manual
C53000-G1176-C169-1
Figure 2-170
Principle of the trip circuit supervision with one binary input
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 supervision does not operate during system faults. A momentary closed
tripping contact does not lead to a failure indication. If, however, other trip relay con-
tacts from different devices are connected in parallel in the trip circuit, the fault indica-
tion must be delayed by
Alarm Delay
(see also Figure 2-171). After the fault in the
trip circuit is removed, the alarm is reset automatically after the same time.
Figure 2-171
Logic diagram for trip circuit supervision with one binary input
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