ABB eVM1 Installation And Service Instructions Manual page 68

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14.7.2.1.2 Operation criteria
If the measured RMS current exceeds the setting threshold value (Start Value) for at least one
phase, the overcurrent protection function is started.
The protection function will remain in START status until there is at least one phase started. It will
return to passive status and the start signal will be cleared if the current falls below 95% of the
setting threshold value for all the phases.
After the protection has entered the start status and the preset operating time (Time) has elapsed,
the function goes into TRIP status and the trip signal is generated.
The protection function will exit the TRIP status, the trip signal and the counter will be cleared
when the measured current value for all the phases falls below 40% of the setting threshold value.
When the two overcurrent definite time functions are active simultaneously an overcurrent time-
step characteristic can be generated, as shown in the following figure.
Fig. 58 Schematic view of the definite time tripping steps
14.7.2.2 Overcurrent IDMT
One IDMT protection function is available in which one of the four current-time characteristics can
be activated at a time:
Normal inverse,
Very inverse,
Extremely inverse and
Long-term inverse.