ABB RELION Series Technical Manual page 520

Section 6
Supervision functions
514
A070970 V3 EN
Figure 267: Improved connection for parallel trip contacts where the test current
flows through all wires and joints
Several trip circuit supervision functions parallel in circuit
Not only the trip circuit often have parallel trip contacts, it is also possible that the
circuit has multiple TCS circuits in parallel. Each TCS circuit causes its own
supervising current to flow through the monitored coil and the actual coil current is a
sum of all TCS currents. This must be taken into consideration when determining the
resistance of R .
ext
Setting the TCS function in a protection relay not-in-use does not
typically affect the supervising current injection.
Trip circuit supervision with auxiliary relays
Many retrofit projects are carried out partially, that is, the old electromechanical
relays are replaced with new ones but the circuit breaker is not replaced. This creates
a problem that the coil current of an old type circuit breaker can be too high for the
protection relay trip contact to break.
1MRS758755 A
REC615 and RER615
Technical Manual