Functions
6-1317SA6 Manual
C53000-G1176-C156-2
Figure 6-75 Setting parameter characteristics in the logarithmic–inverse curve
Zero Sequence
Voltage Stage with
Inverse
Characteristic
For the zero sequence voltage controlled stage (address 131 Earth Fault O/C =
U0 inverse) the operating mode is initially set: address 3140 Op. mode 3I0p.This
stage can be set to operate
Forward (usually towards line) or Reverse (usually to-
wards busbar) or
Non-Directional (in both directions). If this stage is not required,
set its mode to
Inactive.
Address
3141 3I0p PICKUP indicates the minimum current value above which this
stageisrequiredtooperate.Thevaluemustbeexceededbytheminimumearthfault
current value.
The voltage-controlled characteristic is based on the following formula:
U
0
is the actual zero sequence voltage. U
0min
is the setting value U0inv. minimum
(Address 3183). Please take into consideration that the formulae is based on the zero
sequence voltage U
0
,noton3U
0
. The function is illustrated in the Technical Data Sec-
tion (10.5, Figure 10-5).
Figure 6-76 shows the most important parameters.
U0inv. minimum displaces the
voltage-controlled characteristic in direction of 3U
0
. The set value is the asymptote for
this characteristic (t
→ ∞). In Figure 6-76 a' shows an asymptote that belongs to the
characteristic
a.
The minimum voltage
3U0>(U0 inv) (address 3182) is the lower voltage threshold.
It corresponds to the line
c in Figure 6-76. In characteristic b the curve is cut by the
minimum voltage
3U0>(U0 inv) (line c).
An additional time
T forw. (U0inv) (address 3184) that is added to the voltage-
controlled characteristic can be set for directional-controlled tripping. The directional
additional time is usually not required and set to
0.
With the non-directional time
T rev. (U0inv) (Address 3185) a non-directional
back-up stage can be generated.
0
1
3I0p MaxT-DELAY
3I
0
/3I0p PICKUP
3I0p Time Dial
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