7SR11 & 7SR12 Description Of Operation
Chapter 1 Page 78 of 88 ©2017 Siemens Protection Devices Limited
5.5 Trip/ Close Circuit Supervision (74TCS & 74CCS)
The relay provides three trip and three close circuit supervision elements, all elements are identical in operation
and independent from each other allowing 3 trip and 3 close circuits to be monitored.
One or more binary inputs can be mapped to 74TCS-n. The inputs are connected into the trip circuit such that at
least one input is energised when the trip circuit wiring is intact. If all mapped inputs become de-energised, due to
a break in the trip circuit wiring or loss of supply an output is given.
The 74TCS-n Delay setting prevents failure being incorrectly indicated during circuit breaker operation. This delay
should be greater than the operating time of the circuit breaker.
The use of one or two binary inputs mapped to the same Trip Circuit Supervision element (e.g. 74TCS-n) allows
the user to realise several alternative monitoring schemes.
TCS-n
Enabled
Disabled
&
74TCS
-n
74TCS-n
74TCS-n Delay
≥1
74TCS
-n
NOTE: Diagram shows two binary inputs mapped
to the same Trip Circuit Supervision element
Figure 5-6 Logic Diagram: Trip Circuit Supervision Feature (74TCS)
CCS-n
Enabled
Disabled
&
74CCS-n
74CCS-n Delay
≥1
74CCS-n
NOTE: Diagram shows two binary inputs mapped
to the same Close Circuit Supervision element
74CCS-n
Figure 5-7 Logic Diagram: Close Circuit Supervision Feature (74CCS)
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