Functions
2.10 Monitoring Functions
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010
172
The conditions of the two binary inputs are checked periodically. A check takes place about every 600 ms. If
three consecutive conditional checks detect an abnormality (after 1.8 s), an annunciation is reported (see
Figure 2-53). The repeated measurements determine the delay of the alarm message and avoid that an alarm
is output during short transition periods. After the malfunction in the trip circuit is cleared, the fault annunciation
is reset automatically after the same time period.
Figure 2-53 Logic diagram of the trip circuit supervision with two binary inputs
Supervision with One Binary Input
The binary input is connected according to the following figure in parallel with the associated trip contact of the
protection relay. The circuit breaker auxiliary contact is bridged with a bypass resistor R.
Figure 2-54 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 monitoring circuit is closed by either the 52a circuit breaker auxiliary contact
(if the circuit breaker is closed) or through the bypass resistor R by the 52b circuit breaker auxiliary contact.
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 continuously deactivated during operation, this leads to the conclusion that there is an in-
terruption in the trip circuit or loss of control voltage.
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