ABB Relion 670 series - Voltage Restrained Overcurrent Protection for Generator and Step-Up Transformer

12.1.3.5 Voltage restrained overcurrent protection for generator and step-up
transformer
Example will be given how to use one CVGAPC function to provide voltage restrained
overcurrent protection for a generator. Let us assume that the time coordination study
gives the following required settings:
• Inverse Time Over Current TOC/IDMT curve: ANSI very inverse
• 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
This functionality can be achieved by using one CVGAPC function. The following shall
be done in order to ensure proper operation of the function:
1. Connect three-phase generator currents and voltages to one CVGAPC instance (for
example, GF05)
2. Set CurrentInput to value MaxPh
3. Set VoltageInput to value MinPh-Ph (it is assumed that minimum phase-to-phase
voltage shall be used for restraining. Alternatively, positive sequence voltage can be
used for restraining by selecting PosSeq for this setting parameter)
4. Set base current value to the rated generator current primary amperes
5. Set base voltage value to the rated generator phase-to-phase voltage in kV
6. Enable one overcurrent step (for example, OC1)
7. Select CurveType_OC1 to value ANSI Very inv
8. If required set minimum operating time for this curve by using parameter tMin_OC1
(default value 0.05s)
9. Set PickupCurr_OC1 to value 185%
10. Set VCntrlMode_OC1 to On
11. Set VDepMode_OC1 to Slope
12. Set VDepFact_OC1 to value 0.25
13. Set VHighLimit_OC1 to value 100%
14. Set VLowLimit_OC1 to value 25%
Proper operation of the CVGAPC function made in this way can easily be verified by
secondary injection. All other settings can be left at the default values. Furthermore the
other built-in protection elements can be used for other protection and alarming purposes.
12.1.3.6 Loss of excitation protection for a generator
Example will be given how by using positive sequence directional overcurrent protection
element within a CVGAPC function, loss of excitation protection for a generator can be
achieved. Let us assume that from rated generator data the following values are calculated:
1MRK 506 369-UUS - Section 12
Multipurpose protection
Line distance protection REL670 2.2 ANSI 613
Application manual