Siemens siprotec 7SA522 User Manual page 370

Functions
6.16.1.4 Trip Circuit Supervision
Monitoring with
Two Binary Inputs
6-222
The Distance Protection 7SA522 incorporates an integrated trip circuit supervision
function. Depending on the number of binary inputs with isolated control inputs that
are still available, a choice can be made between monitoring with one or with two bi-
nary inputs. If the allocation of the required binary inputs does not match the selected
monitoring mode, a corresponding alarm is issued ("7ULS& 3URJ)$,/" along with
the number of the faulty monitoring circuit). If two binary inputs are used, disturbances
of the trip circuit can be detected during all switching states. With only one binary input,
faults in the circuit breaker can not be detected. If single-pole tripping is possible, a
separate trip circuit supervision can be implemented for each circuit breaker pole pro-
vided the required binary inputs are available.
If two binary inputs are used, these are connected as shown in Figure 6-118. The one
binary input is connected in parallel to the corresponding trip relay contact of the pro-
tection while the other is connected in parallel to the circuit breaker auxiliary contacts.
A prerequisite for the implementation of the trip circuit supervision function is that the
control voltage of the circuit breaker is greater than the sum of the minimum voltage
drops across the two binary inputs (U
binary input, the monitoring can only be implemented if the plant control voltage is
greater than 38 V.
L
+
TR
Aux1
TC
CB
L
–
Figure 6-118 Trip circuit supervision operating principle with two binary inputs
The monitoring with two binary inputs not only detects interruptions of the trip circuit
and failure of the control voltage, but also monitors the reaction of the circuit breaker
by means of the switching state of the circuit breaker auxiliary contacts.
Depending on the switching state of the trip relay and circuit breaker, the binary inputs
are initiated (logic state "H" in Table 6-5) or short circuited (logic state "L").
The state where both binary inputs are not energized ("L") is only present during a
short transition phase (trip relay contact is closed, but the circuit breaker has not yet
opened) if the trip circuit is healthy.
> 2·U
C BImin
U
C
U
BI1
7SA522
U
BI2
Aux2
). As at least 19 V is necessary per
7SA522
>Trip C1 TripRel
>Trip C1 BKr.Rel
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)
U — control voltage (tripping voltage)
C
U — input voltage of the 1st binary input
BI1
U — input voltage of the 2nd binary input
BI2
Note: The circuit breaker is shown in closed position!
7SA522 Manual
C53000-G1176-C119-2