ABB RELION 620 Series Technical Manual page 586

Section 6
Supervision functions
580
A051097-ANSI V2 EN
Figure 291: Operating principle of the trip-circuit supervision with an external resistor.
The TCM blocking switch is not required since the external resistor is
used.
If TCM is required only in a closed position, the external shunt resistance can be omitted.
When the circuit breaker is in the open position, the TCM sees the situation as a faulty
circuit. One way to avoid TCM operation in this situation would be to block the
supervision function whenever the circuit breaker is open.
1MAC504801-IB E
620 series ANSI
Technical Manual