ABB 615 Series ANSI, Technical Manual, Page: 439 / 713

Section 6
1MAC050144-MB C
Supervision functions
432 615 series ANSI
Technical Manual
The
BLOCK
input can be controlled with a binary input, a horizontal communication input
or an internal signal of the relay program. The activation of the
BLOCK
input prevents the
ALARM
output to be activated.
6.2.5 Application
TCM detects faults in the electrical control circuit of the circuit breaker. The function can
supervise both open and closed coil circuits. This kind of monitoring is necessary to find
out the vitality of the control circuits continuously.
The following figure shows an application of the trip-circuit monitoring function usage.
The best solution is to connect an external R
ext
shunt resistor in parallel with the circuit
breaker internal contact. Although the circuit breaker internal contact is open, TCM can
see the trip circuit through R
ext
. The R
ext
resistor should have such a resistance that the
current through the resistance remains small, that is, it does not harm or overload the
circuit breaker's trip coil.
Figure 225: 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 the TCM is required only in a closed position, the external shunt resistance may 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
monitoring function whenever the circuit breaker is open.