Chapter 7 - 7SR157 Applications Guide
© 2016 Siemens Protection Devices Limited
Chapter 7 - Page 9 of 14
Section 3: Supervision Functions
3.1
Close Circuit Supervision (74CCS)
Binary Inputs may be used to monitor the integrity of the CB close circuit wiring. A small current flows through the
BI and the circuit. This current operates the BI confirming the integrity of the auxiliary supply, CB coil, auxiliary
switch, C.B. secondary isolating contacts and associated wiring. If monitoring current flow ceases the BI drops off
and if it is user programmed to operate one of the Binary Outputs, this can provide a remote alarm. In addition, an
LED on the relay can be programmed to operate. A user text label can be used to define the operated LED e.g.
“Close CCT Fail”.
The relevant Binary Input is mapped to
74CCS-n
in the INPUT CONFIG>INPUT MATRIX menu. To avoid giving
spurious alarm messages while the circuit breaker is operating, the input is given a 0.4s Drop-off Delay, which is
found in the SUPERVISION>CLOSE CIRCUIT SUPERVISION menu.
To provide an alarm output, a normally-open Binary Output is mapped to
74CCS-n
.
3.1.1
Close Circuit Supervision Connections
R
BI
+ve
-ve
+
BO 1
BO n
Remote
Alarm
BO
R
CLOSE
COIL
52b
52a
-
Circuit
Breaker
H5 Scheme Notes:
BI = 19V (30, 48, 110, 220V supply)
BI = 88V (110, 220V supply)
R = 3K3 typical
CLOSE CCT n FAIL
Figure 3-1 Close Circuit Supervision Scheme
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