ABB Relion 611 Series, Technical Manual

Page: 341 / 536

The circuit breaker coil current is normally cut by an internal contact of the circuit
breaker. In case of a circuit breaker failure, there is a risk that the protection relay trip
contact is destroyed since the contact is obliged to disconnect high level of
electromagnetic energy accumulated in the trip coil.
An auxiliary relay can be used between the protection relay trip contact and the circuit
breaker coil. This way the breaking capacity question is solved, but the TCS circuit in
the protection relay monitors the healthy auxiliary relay coil, not the circuit breaker
coil. The separate trip circuit supervision relay is applicable for this to supervise the
trip coil of the circuit breaker.
Dimensioning of the external resistor
Under normal operating conditions, the applied external voltage is divided between
the relay’s internal circuit and the external trip circuit so that at the minimum 20 V
(15...20 V) remains over the relay’s internal circuit. Should the external circuit’s
resistance be too high or the internal circuit’s too low, for example due to welded relay
contacts, a fault is detected.
Mathematically, the operation condition can be expressed as:
U R R I V AC DC
C ext int s c
− + + × ≥
(R ) / 20
A070986 V2 EN
(Equation 33)
U
c
Operating voltage over the supervised trip circuit
I
c
Measuring current through the trip circuit, appr. 1.5 mA (0.99...1.72 mA)
R
ext
external shunt resistance
R
int
internal shunt resistance, 1 kΩ
R
s
trip coil resistance
If the external shunt resistance is used, it has to be calculated not to interfere with the
functionality of the supervision or the trip coil. Too high a resistance causes too high
a voltage drop, jeopardizing the requirement of at least 20 V over the internal circuit,
while a resistance too low can enable false operations of the trip coil.
Table 366: Values recommended for the external resistor R
ext
Operating voltage U
c
Shunt resistor R
ext
48 V AC/DC 1.2 kΩ, 5 W
60 V AC/DC 5.6 kΩ, 5 W
110 V AC/DC 22 kΩ, 5 W
220 V AC/DC 33 kΩ, 5 W
Due to the requirement that the voltage over the TCS contact must be 20 V or higher,
the correct operation is not guaranteed with auxiliary operating voltages lower than 48
V DC because of the voltage drop in R
int
,R
ext
and the operating coil or even voltage
1MRS757454 D
Section 6
Supervision functions
611 series 335
Technical Manual