Ashida ADR241B, Instruction Manual

Page: 100 / 272

ADR241B
Doc ID : ADR241B-DO_IM_01
Ref ID : ADR241B/IM/PLF
Rev No. : 06
Page No. : 100 of 272
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Definite time Over current (C6)
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IEEE Moderately Inverse Curve (C7)
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IEEE Very Inverse Curve (C8)
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IEEE Extremely Inverse Curve (C9)
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IEEE Inverse Curve (C10)
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IEEE Short Time Inverse Curve (C11)
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User Define Curve (C12)
The over current, earth fault and negative sequence O/C function are programmable as per
IDMT characteristic based on IEC and IEEE/ANSI standards. The inverse time delay is
calculated with the following mathematical formula:
Where
t : Operation time
K : Constant (see the table)
I : Measured current
I
s
: Current threshold setting (also refer as Gs as IEC standard notation)
α : Constant (see the table)
L : ANSI/IEEE constant (zero for IEC curve)
T : Time multiplier setting (TMS) for IEC & IEEE curves
Description Standard K
α
L
IEC Standard Inverse 1 IEC 0.14 0.02 0
IEC Standard Inverse 2 IEC 0.06 0.02 0
IEC Very Inverse IEC 13.5 1 0
IEC Extremely Inverse IEC 80 2 0
IEC Long Time Inverse IEC 120 1 0
Definite Time - - - -
IEEE Moderately Inverse IEEE 0.0515 0.02 0.114
IEEE Very Inverse IEEE 19.61 2 0.491
IEEE Extremely Inverse IEEE 28.2 2 0.1217
IEEE Inverse IEEE 5.95 2 0.18
IEEE Short Time Inverse IEEE 0.0239 0.02 0.0169
User Define Curve - - - -
t = T*
K
I
Is
α
– 1
+ L