Overcurrent Protection With Undervoltage Seal-In - ABB RELION 670 Series Applications Manual

1MRK 504 152-UEN B
• 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
2. Set
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
inv.
5. Set the multiplier
6. Set
inverse time characteristic.
7. If required, set the minimum operating time for this curve by using the parameter
(default value 0.05 s).
8. Set
9. Set
10. Set
11. Set
All other settings can be left at the default values.
8.16.3.3

Overcurrent protection with undervoltage seal-in

To obtain this functionality, the IED application configuration shall include a logic in
accordance to figure
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
2. Set
UBase and IBase equal to the rated phase-to-phase voltage and the rated phase current of
the generator.
3. Set
4. Set
5. Set
6. Set
stage is constant, irrespective of the magnitude of the generator voltage.
7. Set
8. Set
9. Set
10. Set
undervoltage stage.
Application manual
Operation to On
GlobalBaseSel to the right value in order to select the Global Base Values Group with
Characterist to match the type of overcurrent curves used in the network IEC Very
k = 1 (default value).
tDef_OC = 0.00 s, in order to add no additional delay to the trip time defined by the
StartCurr to the value 185%.
VDepMode to Slope (default value).
VDepFact to the value 25% (default value).
UHighLimit to the value 100% (default value).
276 and, of course, the relevant three-phase generator currents and
Operation to On .
GlobalBaseSel to the right value in order to select the Global Base Values Group with
StartCurr to the value 150 %.
Characteristic to IEC Def. Time .
tDef_OC to 6000.00 s, if no trip of the overcurrent stage is required.
VDepFact to the value 100 % in order to ensure that the start value of the overcurrent
Operation_UV to On to activate the undervoltage stage.
StartVolt to the values 70 %.
tDef_UV to 3.0 s.
EnBlkLowV to Off (default value) to disable the cut-off level for low-voltage of the
Section 8
Current protection
tMin
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