Siemens siprotec 7SA6, Manual

Page: 473 / 876

Functions
6-283
7SA6 Manual
C53000-G1176-C156-2
Figure 6-146 Operating principle of the trip circuit supervision with one binary input
During normal operation there is an input signal on the binary input when the trip relay
contact is open and the trip circuit is healthy (logic state “H”), because the monitoring
circuit is closed via the auxiliary contact (while circuit breaker is closed) or via the sub-
stitute resistance R. The binary input is only short circuited and thereby not picked up
(logic state “L”) while the trip relay is closed.
If the binary input is continuously not picked up, this indicates an interruption of the trip
circuit or loss of the (tripping) control supply voltage.
As the trip circuit supervision is not in service during a system fault, the closed trip re-
lay contact does not cause an incorrect alarm. If however other trip relay contacts from
different devices are connected in parallel in the trip circuit, the failure alarm must be
delayed by
Alarm Delay
(refer also to Figure 6-147). After clearance of the failure
in the trip circuit, the failure alarm automatically resets with the same time delay.
Figure 6-147 Logic diagram of the trip circuit supervision with one binary input
6.21.1.5 Response to Failures
Depending on the nature of the detected failure, an alarm is issued, the processor sys-
tem is rebooted or the device is taken out of service. Following three unsuccessful re-
start attempts, the device is also taken out of service. The device healthy relay (live)
also resets and alarms the failure state of the relay with its normally closed contact. In
addition the red LED “ERROR” on the front plate of the device is illuminated if the in-
ternal auxiliary supply is available, and the green LED “RUN” is extinguished. If the
internal auxiliary supply also fails all LEDs are extinguished. In Table 6-13 a summary
of the monitoring functions and the response of the device to detected failures is
L
–
L
+
TR
Aux2 Aux1
U
BI
U
C
7SA6
7SA6
TC
CB
Legend:
TR — trip relay contact
CB — circuit breaker
TC — circuit breaker trip coil
Aux1 — circuit breaker auxiliary contact
(normally open)
Aux2 — circuit breaker auxiliary contact
(normally closed)
R — substitute resistor
U
C
— control voltage (tripping voltage)
U
BI
— input voltage of the binary input
Note: The circuit breaker is shown in closed position!
R
>Trip C1 TripRel
&
Power System fault
Tr T
4003 Alarm Delay
>Trip C1 TripRel
FAIL: Trip cir.
FNo 6865
FNo 6854
Tr approx. 1 to 2 s