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Intermittent transient
earth fault protection
I
> (67NT)
0T
Recorded Values of the Latest Eight Faults
Detailed information is available on the eight latest earth faults: Time
stamp, fault current, elapsed delay and setting group.
Table 3.20 – Parameters of the Undirectional Earth Fault Stages
(8 latest faults) I
>, I
>>, I
>>>, I
0
0
0
Parameter
Value
yyyy-mm-dd
hh:mm:ss.ms
Flt
EDly
1
SetGrp
2
NOTE: This function is available only in voltage measurement
1
modes
, which include direct -U0 measurement like for example
2U
+U
, but not for example in mode 3U
LL
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
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
and U
.
0
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 3.20).
Figure 3.20 – Typical phase to earth voltages
Protection Functions
>>>> (50N/51N)
0
Unit
Description
Time stamp of the recording, date
Time stamp, time of day
pu
Maximum earth fault current
%
Elapsed time of the operating time setting.
100% = trip
Active setting group during the fault
.
LN
Fault
857-UM001A-EN-P – July 2009
3-35
and the fault
Note: Residual current
of the faulty feeder and
the zero sequence
voltage U
during two
0
transient earth faults in
phase L1. In this case the
network is compensated.
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