VAMP 265 - 2.13.1. Standard Inverse Delays Iec, Ieee, Ieee2, Ri; Default Chapter; Standard Inverse Delays IEC, IEEE, IEEE2, RI

2.13 Inverse time operation
2 Protection functions
Technical description
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VM265.EN011
2.13.1. Standard inverse delays IEC, IEEE, IEEE2, RI
The available standard inverse delays are divided in four
categories IEC, IEEE, IEEE2 and RI called delay curve
families. Each category of family contains a set of different
delay types according the following table.
Inverse time setting error signal
The inverse time setting error signal will be activated, if the
delay category is changed and the old delay type doesn't exist
in the new category. See chapter 2.13 for more details.
Limitations
The minimum definite time delay start latest, when the
measured value is twenty times the setting. However, there are
limitations at high setting values due to the measurement
range. See chapter 2.13 for more details.
Table 2.13.1-1 Available standard delay families and the
available delay types within each family.
Delay type
Curve family
DT
IEC
IEEE
IEEE2
RI
DT
Definite time
X
NI1
Normal inverse
X
X
VI
Very inverse
X
X
X
EI
Extremely inverse
X
X
X
LTI
Long time inverse
X
X
LTEI
Long time extremely inverse
X
LTVI
Long time very inverse
X
MI
Moderately inverse
X
X
STI
Short time inverse
X
STEI
Short time extremely inverse
X
RI
Old ASEA type
X
RXIDG
Old ASEA type
X
IEC inverse time operation
The operation time depends on the measured value and other
parameters according Equation 2.13.1-1. Actually this equation
can only be used to draw graphs or when the measured value I
is constant during the fault. A modified version is implemented
in the relay for real time usage.