ABB REF615 Applications Manual page 198

Section 7
Supervision functions
192
Using power output contacts without trip-circuit supervision
If TCS is not used but the contact information of corresponding power outputs are
required, the internal resistor can be by-passed. The output can then be utilized as a
normal power output. When bypassing the internal resistor, the wiring between the
terminals of the corresponding output X100:16-15(PO3) or X100:21-20(PO4) can be
disconnected. The internal resistor is required if the complete TCS circuit is used.
GUID-0560DE53-903C-4D81-BAFD-175B9251872D V1 EN
Figure 95: Connection of a power output in a case when TCS is not used and
the internal resistor is disconnected
Incorrect connections and usage of trip-circuit supervision
Although the TCS circuit consists of two separate contacts, it must be noted that those
are designed to be used as series connected to guarantee the breaking capacity given
in the technical manual of the IED. In addition to the weak breaking capacity, the
internal resistor is not dimensioned to withstand current without a TCS circuit. As a
result, this kind of incorrect connection causes immediate burning of the internal
resistor when the circuit breaker is in the close position and the voltage is applied to
the trip circuit. The following picture shows incorrect usage of a TCS circuit when
only one of the contacts is used.
1MRS756378 D
REF615
Application Manual