Section 4 1MDU07212-YN Rev. D
Protection and Control Function
34 REF601 / REJ601 / REM601
Application Manual
Table 21: Setting ranges Phase reversal protection
0.1…1.5 x Ib, in steps of 0.01
Operate delay time, ‘tI2R>’
0.1 … 300 sec, in steps of 0.1
Block the negative phase sequence
protection
3% of set value or ± 30ms
4.11 Under current protection
4.11.1 Functionality
The under current protection is used to detect a sudden loss of load which is
considered as a fault condition. Function starts when the current is less than the set
limit. It operates with the definite time (DT) characteristics i.e. function operates
after a predefined operate time and resets when the fault current disappears
4.11.2 Principle of operation
The measured three phase current is compared to the set 3I< value. If the measured
value is less than the set 3I< value, in all the three phases the level detector
activates the timer module and will activate binary output 3I< Start. The level
detector is enabled only after all three phase currents are above the set 3I< value
for at least 5sec before the comparison is initialized.
The function is blocked internally when current in all three phases are below
0.12xIn (which is considered as stopped condition)
The time characteristic is according to Definite Time (DT). When the operation
timer has reached the value set by the t 3I< value, the 3I< Trip output is activated.
If the fault disappears before the module operates, the reset timer is activated. It is
a fixed timer of 40msec, when the timer reaches 40msec, the operate timer resets.
The protection could be blocked by settings or via binary input of the relay.
The START output of the function can be configured at alarm
LEDs, however activation of START output will not result into
activation of START LED or any event logging.
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