Technical description
2 Protection functions
2.23 Inverse time operation
VM50.EN004
VAMP 24h support phone +358 (0)20 753 3264
109
2.23.2.
Free parameterization using IEC, IEEE and
IEEE2 equations
This mode is activated by setting delay type to ‘Parameters’,
and then editing the delay function constants, i.e. the
parameters A ... E. The idea is to use the standard equations
with one’s own constants instead of the standardized constants
as in the previous chapter.
Example for GE-IAC51 delay type inverse:
k
=
0.50
I
=
4
pu
I
pickup
= 2 pu
A
=
0.2078
B
=
0.8630
C
=
0.8000
D
=
0.4180
E
=
0.1947
37
.
0
8
.
0
2
4
1947
.
0
8
.
0
2
4
4180
.
0
8
.
0
2
4
8630
.
0
2078
.
0
5
.
0
3
2
t
The operation time in this example will be 0.37 seconds.
The resulting time/current characteristic of this example
matches quite well with the characteristic of the old
electromechanical IAC51 induction disc relay.
Inverse time setting error signal
The inverse time setting error signal will become active, if
interpolation with the given parameters is not possible. See
chapter 2.23 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 2.23 for more details.
