Trip-Circuit Supervision - ABB REM 610 Technical Reference Manual

REM 610 REM 610
5.1.5.
62
Motor Protection Relay
Technical Reference Manual - ANSI Version
Table 5.1.4.13.-11 CBFAIL
Feature
Set operate time
Phase-current threshold for external
triggering of the CBFAIL
pick-up/drop-off
*
The accuracies apply only when the FLA secondary scaling factor has
been set to 1.

Trip-circuit supervision

The trip-circuit supervision (TCS) detects open circuits, both when the circuit
breaker is open and closed, and trip-circuit supply failure.
The trip-circuit supervision includes:
Current limiter including the necessary hardware
*
Software-based function in the self-supervision system
*
The trip-circuit supervision is based on a constant current injection principle: by
applying an external voltage, a constant current is forced to flow through the
external trip circuit. If the resistance of the trip circuit exceeds a certain limit for
more than 21 seconds, due to oxidation or a bad contact, for instance, the trip-circuit
supervision is activated and a warning appears on the LCD together with a fault
code. The warning signal from the trip-circuit supervision can also be routed to SO2
by setting switch SGF1/8 to 1.
Under normal operating conditions, the applied external voltage is divided between
the relay's internal circuit and the external trip circuit so that at least 20 V remains
over the relay's internal circuit. If the external trip circuit's resistance is too high or
the internal circuit's too low, due to welded relay contacts, for instance, the voltage
over the relay's internal circuit falls below 20 V (15...20 V), which activates the trip-
circuit supervision.
The operation condition is:
( )
− + + ×
U R R R I
c e xt int s inj
U = operating voltage over the supervised trip circuit
c
I = current flowing through the trip circuit, ~1.5 mA
inj
R = external shunt resistor
ext
R = internal shunt resistor, 1 kΩ
int
R = trip coil resistance
s
Value
0.10...60.0 s
0.13/0.11 x FLA
≥
20 V ac/dc
1MRS755537
(3)