• 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.
9.14.3.3 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
286 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%.
1MRK 506 369-UEN B Section 9
Current protection
Line distance protection REL670 2.2 IEC 531
Application manual
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