InteliLite
NT
– AMF20/25, SW version 1.2, ©ComAp – March 2008 48
IL-NT-AMF-Reference Guide1.2.pdf
IDMT is “very inverse” generator over current protection. Reaction time is not constant but depends on
generator over current level according following formula.
Amps IDMT Del * Nomin Current
Reaction time =
Igen - Nomin Current
Hint:
Reaction time is limited up to 900 sec = 15 minutes. IDMT protection is not active for Reaction time
values longer than 15 minutes.
Igen is maximal value of all measured phases of generator current.
EXAMPLE of Reaction time for different over current levels. Values in column 200% are
IDMT Curr
Del.
Overcurrent
200 % =
IDMT Curr
Del
≤ 100 % 101 % 110 %
0,2 s
No action 20 s 2 s
2 s
No action 200 s 20 s
Reaction time
20 s
No action No action
(time > 900 s)
200 s
Igen
Nominal Current
Short Crct Sd
Amps IDMT Del
Maximal Reaction time
Reaction time
Amps Unbal Sd [%]
Threshold for generator current asymmetry (unbalance).
Step: 1% of Nominal current
Range: 1 – 200% of Nominal current
Amps Unbal Del [s]
Delay for generator current unbalance
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