Voltage-Restrained Overcurrent Protection For Generator And Step-Up Transformer - ABB RELION RET670 Applications Manual

Section 9
Current protection
9.17.3.2
9.17.3.3
610
Voltage-restrained overcurrent protection for generator and step-up
transformer
An example of how to use VRPVOC (51V) 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
• Pickup current of 185% of generator rated current at rated generator voltage
• Pickup current 25% of the original pickup current value for generator voltages
below 25% of rated voltage
To ensure proper operation of the function:
1. Set Operation to Enabled
2. Set GlobalBaseSel to the right value in order to select the Global Base Values
Group with VBase 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 (51V) 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
t_MinTripDelay (default value 0.05 s).
8. Set PickupCurr to the value 185%.
9. Set VDepMode to Slope (default value).
10. Set VDepFact to the value 25% (default value).
11. Set VHighLimit 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 294
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:
and, of course, the relevant three-phase generator currents and
1MRK 504 163-UUS A
GUID-263B960B-2280-461C-B455-F17B7D278F60 v8
GUID-B58E1CD6-F9AE-4301-ABE7-90DBFC987D69 v6
Transformer protection RET670 2.2 ANSI
Application manual