•
Inverse Time Over Current IDMT curve: IEC very inverse, with multiplier k=1
•
Start current of 185% of generator rated current at rated generator voltage
•
Start current 25% of the original start current value for generator voltages below 25% of
rated voltage
To ensure proper operation of the function:
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.
Connect three-phase generator currents and voltages to VRPVOC in the application
configuration.
4. Select
Characterist to match the type of overcurrent curves used in the network IEC Very
inv.
5. Set the multiplier
k = 1 (default value).
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.
8.14.3.3
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
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.
Section 8
1MRK 505 343-UEN B
Current protection
464
Application manual
Summary of Contents for Relion 670 series
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