7SR242 Duobias Description Of Operation
©2010 Siemens Protection Devices Limited Chapter 1 Page 45 of 52
5.2 Trip/Close Circuit Supervision (74TCS/74CCS)
The relay provides six trip and six close circuit supervision elements, all elements are identical in operation and
independent from each other allowing 6 trip and 6 close circuits to be monitored.
One or more binary inputs can be mapped to 74TCS-n/74CCS-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 or 74CCS-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 Circuit Supervision element (e.g. 74TCS-n) allows the
user to realise several alternative monitoring schemes – see ‘Applications Guide’.
Figure 5-2 Logic Diagram: Trip Circuit Supervision Feature (74TCS)
&
≥1
NOTE: Diagram shows two binary inputs mapped
to the same Close Circuit Supervision element
Figure 5-3 Logic Diagram: Close Circuit Supervision Feature (74CCS)
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