Iec Curves; Constants For Iec Curves - GE Multilin F650 Instruction Manual

5.4 PROTECTION ELEMENTS
5.4.2.2

IEC CURVES

This family of curves follows European standard IEC 255-4, and 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 time in seconds (assuming 100% of power capacity and that the reset is activated)
RESET
5 t = characteristic constant.
r
Table 5–30: CONSTANTS FOR IEC CURVES
IEC CURVE SHAPE
IEC Curve A
IEC Curve B
IEC Curve C
IEC Long-Time Inverse
IEC Short-Time Inverse
5-30
NAME K
IEC Curve A 0.140
IEC Curve B 13.500
IEC Curve C 80.000
IEC Long-Time Inv 120.000
IEC Short-Time Inv 0.050
F650 Digital Bay Controller
5 SETPOINTS
E tr
0.020 9.7
1.000 43.2
2.000 58.2
1.000 120.0
0.040 0.5
GE Multilin