Standard Inverse-Time Characteristics For Undervoltage Protection - ABB RELION REX640 Technical Manual

1MRS759142 C
11.3.2.1
REX640
Technical Manual
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.

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:
k A
t s ⋅
 
=
   
U U
< −
 
B C
⋅ −
 
U
<
 
GUID-0C319E46-5B93-4C24-8002-4104FFA6DF58 V1 EN
t [s] Operate time in seconds
U Measured voltage
Start value setting
U< Set value of the
k Set value of the Time multiplier setting
Table 1477: Curve coefficients for standard undervoltage IDMT curves
Curve name A
(21) Inverse 1
Curve A
(22) Inverse 480
Curve B
General function block features
D
+
E
B C
1 0
32 0.5
Section 11
(Equation 363)
D E
0 1
0.055 2
1699