Siemens SIPROTEC 7SJ62 Instruction Manual page 296

Functions
Monitoring with
One Binary Input
6-156
The conditions of the two binary inputs are checked periodically. A check takes place
about every 600 ms. If three consecutive conditional checks detect an abnormality (af-
ter 1.8 s), an annunciation is reported (see Figure 6-65). This is used to avoid the an-
nunciation for brief transition periods. When the fault in the trip circuit has been
cleared, the annunciation is automatically reset.
AÆ %'$!
>74 TC trip rel.
AÆ %'$"
>74 TC brk rel.
Figure 6-65 Logic Diagram for Trip Circuit Monitoring with Two Binary Inputs
The binary input is connected according to figure 6-66 in parallel with the associated
trip contact. The circuit breaker auxiliary contact 52-b is connected in series with a
high-ohm resistor R.
The control voltage for the circuit breaker should be about two times the value of the
minimum voltage drop at the binary input (V
to activate a binary input is 17 V, a DC voltage supply of 35 V or higher is required.
V
St
V+
RTC
52TC
52a
52
V–
Figure 6-66 Principle of Trip Circuit Monitoring with One Binary Input
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 monitoring circuit is closed
by either the 52a circuit breaker auxiliary contact (if the circuit breaker is closed) or
through the replacement resistor R by the 52b circuit breaker auxiliary contact. Only
as long as the trip contact is closed, the binary input is short circuited and thereby de-
activated (logical condition "L").
If the binary input is continuously de-activated during operation, this leads to the con-
clusion, there is an interruption in the trip circuit or loss of control voltage.
The trip circuit monitor does not operate during system faults. A momentary closed
tripping contact does not lead to a failure message. If, however, tripping contacts from
other devices operate in parallel with the trip circuit, then the failure annunciation must
be delayed (see also Figure 6-67). The conditions of the binary input are, therefore,
&
> n
n . ..... Number of Condition Checks (= 3)
(Measurement Repetition Occurs every 600 ms)
> 2 ⋅ V
St
V
BI
7SJ62
R
52b
AÆ %'%$
FAIL: Trip cir.
). Since the minimum voltage
BImin
7SJ62
AÆ %'$!
>74 TC trip rel.
Legend:
RTC — Trip Contact
52 — Circuit Breaker
52TC — Circuit Breaker Trip Coil
52a — Circuit Breaker Auxiliary Contact
(closed when 52 is closed)
52b — Circuit Breaker Auxiliary Contact
(closed when 52 is open)
V — Control Voltage
St
V — Input Voltage for Binary Input
BI
Note: The above diagram refers to a closed circuit
breaker position
7SJ62 Manual
C53000-G1140-C121-1