ABB RELION Series, Technical Manual

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time mode. The set value depends on the selected curve type and the setting values
used. The user determines the curve scaling with the
Time multiplier setting.
The Minimum operate time setting defines the minimum operate time possible for the
IDMT mode. For setting a value for this parameter, the user should carefully study the
particular IDMT curve.
11.3.2.1 Standard inverse-time characteristics for undervoltage protection
The operate times for the standard undervoltage IDMT curves are defined with the
coefficients A, B, C, D and E.
The inverse operate time can be calculated with the formula:
t s
k A
B
U U
U
C
D
E

 

=
⋅
×
< −
<
−






+
GUID-4A433D56-D7FB-412E-B1AB-7FD43051EE79 V2 EN
(Equation 85)
t [s] operate time in seconds
U measured voltage
U< the set value of the
Start value setting
k the set value of the
Time multiplier setting
Table 711: Curve coefficients for standard undervoltage IDMT curves
Curve name A B C D E
(21) Inverse
Curve A
1 1 0 0 1
(22) Inverse
Curve B
480 32 0.5 0.055 2
1MRS758755 A
Section 11
General function block features
REC615 and RER615 753
Technical Manual