6. Set
tDef_OC
=
0.00
s, in order to add no additional delay to the trip time defined by the
inverse time characteristic.
7. If required, set the minimum operating time for this curve by using the parameter
tMin
(default value 0.05 s).
8. Set
StartCurr
to the value 185%.
9. Set
VDepMode
to
Slope
(default value).
10. Set
VDepFact
to the value 25% (default value).
11. Set
UHighLimit
to the value 100% (default value).
All other settings can be left at the default values.
7.16.3.3 Overcurrent protection with undervoltage seal-in
GUID-B58E1CD6-F9AE-4301-ABE7-90DBFC987D69 v6
To obtain this functionality, the IED application configuration shall include a logic in
accordance to figure 78 and, of course, the relevant three-phase generator currents and
voltages shall be connected to VRPVOC. Let us assume that, taking into account the
characteristic of the generator, the excitation system and the short circuit study, the following
settings are required:
• Start current of the overcurrent stage: 150% of generator rated current at rated generator
voltage;
• Start voltage of the undervoltage stage: 70% of generator rated voltage;
• Trip time: 3.0 s.
The overcurrent stage and the undervoltage stage shall be set in the following way:
1. Set
Operation
to
On
.
2. Set
GlobalBaseSel
to the right value in order to select the Global Base Values Group with
UBase
and
IBase
equal to the rated phase-to-phase voltage and the rated phase current of
the generator.
3. Set
StartCurr
to the value
150
%.
4. Set
Characteristic
to
IEC Def. Time
.
5. Set
tDef_OC
to
6000.00
s, if no trip of the overcurrent stage is required.
6. Set
VDepFact
to the value
100
% in order to ensure that the start value of the overcurrent
stage is constant, irrespective of the magnitude of the generator voltage.
7. Set
Operation_UV
to
On
to activate the undervoltage stage.
8. Set
StartVolt
to the values
70
%.
9. Set
tDef_UV
to
3.0
s.
10. Set
EnBlkLowV
to
Off
(default value) to disable the cut-off level for low-voltage of the
undervoltage stage.
The other parameters may be left at their default value.
1MRK 511 358-UEN A Section 7
Current protection
173
Application manual
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