Siemens Siprotec 7VK61 Manual page 147

Figure 2-54
Supervision with One Binary Input
The binary input is connected in parallel to the respective command relay contact of the protection device ac-
cording to Figure 2-55. The circuit breaker auxiliary contact is bridged with a high-ohm substitute resistor R.
The control voltage for the circuit breaker should be at least twice as high as the minimum voltage drop at the
binary input (U
a system control voltage of over 38 V.
A calculation example for the equivalent resistor R is shown in the configuration notes in Section „Mounting and
Connections", margin heading „Trip Circuit Supervision".
Figure 2-55
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 2-56). After clearance
of the failure in the trip circuit, the fault message automatically resets with the same time delay.
SIPROTEC, 7VK61, Manual
C53000-G1176-C159-3, Release date 05.2009
Logic diagram of the trip circuit monitoring with two binary inputs
> 2·U ). Since at least 19 V are needed for the binary input, the monitor can be used with
Ctrl BImin
Principle of trip circuit monitoring with one binary input
Functions
2.7 Monitoring Function
147