2.14 Inverse time operation
2 Protection functions
Technical description
90
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VM59.EN001
Inverse time setting error signal
If there are any errors in the inverse delay configuration the
appropriate protection stage will use definite time delay.
There is a signal „Setting Error‟ available in output matrix,
which indicates three different situations:
1.
Settings are currently changed with VAMPSET or local
panel, and there is temporarily an illegal combination of
curve/delay/points. For example if previous settings were
IEC/NI and then curve family is changed to IEEE, the
setting error will activate, because there is no NI type
available for IEEE curves. After changing valid delay type
for IEEE mode (for example MI), the „Setting Error‟ signal
will release.
2.
There are errors in formula parameters A…E, and the
device is not able to build the delay curve
3.
There are errors in the programmable curve configuration
and the device is not able to interpolate values between the
given points.
Limitations
The maximum measured secondary phase current is 50xI
N
and
the maximum directly measured earth fault current is 10xI
0N
for residual current inputs. The full scope of inverse delay
curves goes up to 20 times the setting. At high setting the
maximum measurement capability limits the scope of inverse
curves according the following table.
Table 2.14-1
Current input
Maximum measured
secondary current
Maximum secondary
scaled setting
enabling inverse delay
times up to full 20x
setting
I
L1
, I
L2
, I
L3
and I
0Calc
250 A
12.5 A
I
01
5 A
50 A
2.5 A
I
01
1 A
10 A
0.5 A
I
01
0.2 A
2 A
0.1 A
