ABB RELION 620 Series Technical Manual page 683

1MRS757644 F
620 series
Technical Manual
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Figure 342: 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:
d 0 18 . k
t s ( )
= +
2
1000
( M 1 )
−
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t(s) Operate time in seconds
Constant delay setting in seconds
d
M Excitation value (U/f ratio or volts/hertz) in pu
Time multiplier setting
k
Section 4
Protection functions
(Equation 135)
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