ABB RELION REX640 Technical Manual page 1208

Section 6
Supervision functions
1202
(+)
Trip
coil
(-)
GUID-974518ED-AC8C-4F36-82F0-BA279F8CE6C7 V1 EN
Figure 653: 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.
R
ext
CB operating
mechanism
1MRS759142 C
IED
I
TCS
Technical Manual
REX640