ABB Relion SMU615 Technical Manual page 136

Section 5
Supervision functions
130
drop of the feeding auxiliary voltage system which can cause too low voltage values
over the TCS contact. In this case, erroneous alarming can occur.
At lower (<48 V DC) auxiliary circuit operating voltages, it is recommended to use the
circuit breaker position to block unintentional operation of TCS. The use of the
position indication is described earlier in this chapter.
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 V3 EN
Figure 89: Connection of a power output in a case when TCS is not used and the
internal resistor is disconnected
Incorrect connections and use 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 merging unit. 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 figure shows incorrect usage of a TCS circuit when only
one of the contacts is used.
1MRS758407 B
SMU615
Technical Manual