Siemens Siprotec 7VK61 Manual page 146

Functions
2.7 Monitoring Function
Figure 2-53
Monitoring with two binary inputs not only detects interruptions in the trip circuit and loss of control voltage, it
also supervises the response of the circuit breaker using the position of the circuit breaker auxiliary contacts.
Depending on the conditions of the trip contact and the circuit breaker, the binary inputs are activated (logical
condition „H" in the following table), or short-circuited (logical condition „L").
A state in which both binary inputs are not activated („L") is only possible in intact trip circuits for a short tran-
sition period (trip relay contact closed but circuit breaker not yet open).
A continuous state of this condition is only possible when the trip circuit has been interrupted, a short-circuit
exists in the trip circuit, a loss of battery voltage occurs, or malfunctions occur with the circuit breaker mecha-
nism. Therefore, it is used as monitoring criterion.
Table 2-6 Condition table for binary inputs, depending on RTC and CB position
No Trip Contact
.
1 Open
2 Open
3 Closed
4 Closed
The conditions of the two binary inputs are checked periodically. A query takes place about every 500 ms. If
three consecutive conditional checks detect an abnormality, a fault indication is output (see Figure 2-54). The
repeated measurements determine the delay of the alarm message and avoid that an alarm is output during
short transition periods. After clearance of the failure in the trip circuit, the failure alarm automatically resets
with the same time delay.
146
Principle of trip circuit monitoring with two binary inputs
Circuit Breaker Aux 1
ON Closed
OFF Open
ON Closed
OFF Open
Aux 2 BI 1 BI 2 Dynamic State
Open H L
Closed H H
Open L L
Closed L H
C53000-G1176-C159-3, Release date 05.2009
Static State
Normal operation with circuit
breaker closed
Normal operation with circuit
breaker open
Transition or Malfunction
malfunction
TR has tripped successfully
SIPROTEC, 7VK61, Manual