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74TC - Trip Circuit Monitoring
TCM
The trip circuit monitoring is used for monitoring if the trip circuit is ready for opening operations. The monitoring can be
fulfilled by two ways. The first assumes only 52a is used in the trip circuit. The second assumes that, in addition to
52a, 52b is also used for the circuit monitoring. Two options either 52a only (or breaker closed) or both (52a and 52b)
are provided for the User to select based on use of the breaker status in the trip circuit. With 52a only in the trip circuit,
the monitoring is only effective when the breaker is closed while if both 52a and 52b are used, the trip circuit will be
monitored all time as long as the control power is on.
The trip circuit continuity is monitored through the digital inputs DI1 and DI2, and the breaker status 52a or 52b or both
must be monitored through the other digital inputs. Note that the digital inputs used for this purpose must be configured
properly based on the trip circuit control voltage and also that the de-bouncing times must be set to minimum. If the trip
circuit is detected broken, an alarm will be issued with a specified delay, which must be greater than a period from the
time when a trip contact is closed to the time when the breaker status is clearly recognized by the relay.
In this case, the trip circuit supply voltage serves also as supply voltage for the digital inputs and so the supply voltage
failure of a trip circuit can be detected directly.
In order to identify a conductor failure in the trip circuit on the supply line or in the trip coil, the off-coil has to be looped-
in to the supervision circuit.
The time delay is to be set in a way that switching actions cannot cause false trips in this module.
Slot 1 has two digital inputs, each of which has a separate root (contact
separation) for the trip circuit supervision.
EMR-5000
www.eaton.com
IM02602012E
838
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