GEK-106310AB F650 Digital Bay Controller 5-37
5 SETTINGS 5.4 PROTECTION ELEMENTS
5
5.4.2.2 IEC CURVES
This family of curves follows the European standard IEC 255-4, and the British standard BF142 for IEC Curves A, B and C,
IEC Long-Time Inverse and IEC Short-Time Inverse. The formulas that define these curves are as follows:
Where:
t = Operation time in seconds
Dial = multiplying factor
I = Input current
Itap = Current pickup value
K, E = constants defined by the standard
T
RESET
= reset time in seconds (assuming 100% of power capacity and that the reset is activated)
t
r
= characteristic constant.
Table 5–32: CONSTANTS FOR IEC CURVES
IEC CURVE SHAPE NAME K
E tr
IEC Curve A IEC Curve A 0.140
0.020 9.7
IEC Curve B IEC Curve B 13.500
1.000 43.2
IEC Curve C IEC Curve C 80.000
2.000 58.2
IEC Long-Time Inverse IEC Long-Time Inv 120.000
1.000 120.0
IEC Short-Time Inverse IEC Short-Time Inv 0.050
0.040 0.5
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