Voltage-Restrained Overcurrent Protection For Generator And Step-Up Transformer - ABB REC670 Applications Manual

1MRK 511 401-UEN A
8.16.3.2
8.16.3.3
Bay control REC670 2.2 IEC
Application manual
UHighLimit: when the measured phase-to-phase voltage is higher than
UHighLimit/100*UBase, than the start level of the overcurrent stage is StartCurr/
100*IBase. In particular, in Slope mode it define the second point of the
characteristic (StartCurr/100*IBase ; UHighLimit/100*UBase).
Voltage-restrained overcurrent protection for generator and step-up
transformer
An example of how to use VRPVOC function to provide voltage restrained
overcurrent protection for a generator is given below. Let us assume that the time
coordination study gives the following required settings:
• 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.
Overcurrent protection with undervoltage seal-in
To obtain this functionality, the IED application configuration shall include a logic
in accordance to figure
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:
94 and, of course, the relevant three-phase generator
Section 8
Current protection
GUID-263B960B-2280-461C-B455-F17B7D278F60 v8
GUID-B58E1CD6-F9AE-4301-ABE7-90DBFC987D69 v6
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