Technical Reference Manual - ABB REU 610 Technical Reference Manual

REU 610
48
Voltage Relay

Technical Reference Manual

The trip-circuit supervision is based on a constant current injection principle: by
applying operating voltage for the circuit breaker, a constant current is forced to
flow through the external trip circuit. If the resistance of the trip circuit exceeds a
certain limit , 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
tc ext int s
U = operating voltage over the supervised trip circuit
tc
I = current flowing through the trip circuit, ~1.5 mA
tc
R = external shunt resistor
ext
R = internal shunt resistor, 1 kΩ
int
R = trip coil resistance
s
The external shunt resistor is used to enable trip-circuit supervision also when the
circuit breaker is open.
The resistance of the external shunt resistor is to be calculated so that it does not
cause malfunction of the trip-circuit supervision or affect the operation of the trip
coil. Too high resistance causes too high voltage drop, which in turn results in the
operation conditions not being fulfilled, whereas too low resistance may cause
faulty operation of the trip coil.
The following values are recommended for the external resistor, R
Table 5.1.5.-1 Recommended values for R
Operating voltage, U
tc
48 V DC
60 V DC
110 V DC
220 V DC
The circuit breaker is to be provided with two external contacts, one opening and
one closing contact. The closing contact is to be connected in parallel with the
external shunt resistor, which enables trip-circuit supervision when the circuit
breaker is closed. The opening contact, on the contrary, is to be connected in series
with the external shunt resistor, which enables trip-circuit supervision when the
circuit breaker is open; see Fig. 5.1.5.-1.
× ≥
I 20 V AC/DC
tc
Shunt resistor R
1.2 kΩ, 5 W
5.6 kΩ, 5 W
22 kΩ, 5 W
33 kΩ, 5 W
1MRS755769
:
ext
ext
ext
(5)