Functions
2.24 Monitoring Functions
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
440
Supervision 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 supervision criterion.
Table 2-18
Condition table for binary inputs, depending on RTC and CB position
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 2-215). 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.
Figure 2-215
Logic diagram of the trip circuit supervision with two binary inputs
Supervision with One Binary Input
According to Figure 2-216, the binary input is connected in parallel to the respective command relay contact of
the protection device. The circuit breaker auxiliary contact is bridged with a high-resistance bypass 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
Ctrl
> 2·U
BImin
). Since at least 19 V are needed for the binary input, the monitor can be used with
a system control voltage of over 38 V.
A calculation example for the bypass resistor R is shown in the configuration notes in Section „Mounting and
Connections“, margin heading „Trip Circuit Supervision“.
No
.
Trip Contact
Circuit Breaker
Aux 1
Aux 2
BI 1
BI 2 Dynamic State
Static State
1
Open
ON
Closed
Open
H
L
Normal operation with circuit
breaker closed
2
Open
OFF
Open
Closed
H
H
Normal operation with circuit
breaker open
3
Closed
ON
Closed
Open
L
L
Transition or
malfunction
Malfunction
4
Closed
OFF
Open
Closed
L
H
TR has tripped successfully
