1MDU07212-YN Rev. D Section 4
Protection and Control Function
REF601 / REJ601 / REM601 17
Application Manual
Table 5: Setting ranges Non-directional overcurrent protection, High stage 3I>>, 50-1
Setting range of pick-up current I>>
0.2...25 x In in steps 0.001, infinite for CT variant
0.2…20 x In in steps 0. 001, infinite for sensor variant
Operate time delay (DMT) t >>
0.04...64 sec in steps of 0.01
Table 6: Setting ranges Non-directional overcurrent protection, Instantaneous stage 3I>>>, 50-2
Setting range of pick-up current I>>>
0.5...25 x In in steps 0.001, infinite for CT variant
0.5…20 x In in steps 0. 001, infinite for sensor variant
Operate time delay (DMT) t >>>
0.03...64 sec in steps of 0.01
4.2 Earth Fault Protection
4.2.1 Functionality
The earth-fault protection function is used as non-directional earth-fault protection
for feeders.
The earth current can be calculated internally or measured externally by core
balance current transformer.
The operate time characteristics for low stage can be selected to be either definite
time (DT) or inverse definite minimum time (IDMT). The high stage always
operates with the definite time (DT) characteristics.
4.2.2 Principle of Operation
The earth fault protection function continuously measures the neutral current of the
protected object. The current is evaluated by the low stage (I0> / 51N) and high
stage (I0>> / 50N) of earth fault over current functions.
On occurrence of fault, fulfilling the trip condition of respective stage, the LED
“Trip” and “Trip Io” will be activated. Additionally the output relays (Trip and
signalization) will be activated according the binary output configuration.
Each of the stages could be blocked by settings or via binary input of the relay.
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