VAMP 59 - Standard Inverse Delays IEC, IEEE, IEEE2, RI

Technical description
2 Protection functions
2.14 Inverse time operation
VM59.EN001
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Example 1 of limitation
CT = 750/5
CT
0
= 100/1 (cable CT is used for residual current)
The CT
0
is connected to a 1 A terminals of input I
01
.
For overcurrent stage I> the table above gives 12.5 A. Thus the
maximum setting for I> stage giving full inverse delay range is
12.5 A / 5 A = 2.5 xI
N
= 1875 A
PRIMARY
.
For earth fault stage I
0
> the table above gives 0.5 A. Thus the
maximum setting for I
0
> stage giving full inverse delay range is
0.5 A / 1 A = 0.5 xI
0N
= 50 A
PRIMARY
.
2.14.1. 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 2.14 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 2.14 for more details.