Technical description
2 Protection functions
2.14 Intermittent transient earth fault
protection I0T> (67NT)
VM50.EN004
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73
Parameter Value
Unit Description
Note
Io>>
Io>>>
Io>>>>
pu
Pick-up setting relative to the
parameter "Input" and the
corresponding CT value
Set
t> s
Definite operation time (for
definite time only)
Set
Input Io1
IoCalc
X1-7,8,9. See chapter 8.
IL1 + IL2 + IL3
Set
For details of setting ranges see chapter 9.3.
Set = An editable parameter (password needed)
C = Can be cleared to zero
F = Editable when force flag is on
Recorded values of the latest eight faults
There is detailed information available of the eight latest earth
faults: Time stamp, fault current, elapsed delay and setting
group.
Recorded values of the undirectional earth fault stages (8
latest faults) I
0
>, I
0
>>, I
0
>>>, I
0
>>>> (50N/51N)
Parameter Value Unit
Description
yyyy-mm-dd
Time stamp of the recording, date
hh:mm:ss.ms
Time stamp, time of day
Flt
pu
Maximum earth fault current
EDly
%
Elapsed time of the operating time
setting. 100% = trip
SetGrp 1
2
Active setting group during fault
2.14.
Intermittent transient earth fault
protection I
0T
> (67NT)
NOTE! This function is available only when voltage measurement modes is U
0
.
The directional intermittent transient earth fault protection is
used to detect short intermittent transient faults in
compensated cable networks. The transient faults are self
extinguished at some zero crossing of the transient part of the
fault current I
Fault
and the fault duration is typically only 0.1
ms ... 1 ms. Such short intermittent faults can not be correctly
recognized by normal directional earth fault function using only
the fundamental frequency components of I
0
and U
0
.
Although a single transient fault usually self extinguishes
within less than one millisecond, in most cases a new fault
happens when the phase-to-earth voltage of the faulty phase
has recovered (Figure 2.14-1).