71
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
ext
:
Table 5.1.5.-1 Recommended values for R
ext
Operating voltage, U
c
Shunt resistor R
ext
48 V DC 1.2 kΩ,5W
60 V DC 5.6 kΩ,5W
110 V DC 22 kΩ,5W
220 V DC 33 kΩ,5W
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.
Trip-circuit supervision can be selected either via the HMI or with SPA parameter
V113.
Feeder Protection Relay
Technical Reference Manual
REF 610REF 610
1MRS755310
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