ABB RELION REX640 Technical Manual page 814

Section 4
Protection functions
808
GUID-8BE5C57A-BC25-4BF1-BEF3-EC0585F73218 V1 EN
Figure 438: Operating time curves for the overexcitation IDMT curve ("OvExt
IDMT Crv1") for parameters a = 2.5, b = 115.0 and c = 4.886
Overexcitation IDMT curve 4
The base equation for the IDMT curve "OvExt IDMT Crv4" is:
k
0 18 .
t s d
( )
= +
2
( M 1 )
−
GUID-84045D19-EDDF-4514-89CB-051C6298854A V1 EN
t(s) Operate time in seconds
Constant delay setting in milliseconds
d
M Excitation value (U/f ratio or volts/hertz) in pu
Time multiplier setting
k
1MRS759142 C
(Equation 204)
REX640
Technical Manual