Voltage Restrained Overcurrent Protection For Generator And Step-Up Transformer; Loss Of Excitation Protection For A Generator - ABB Relion REC670 Applications Manual

Section 10
Multipurpose protection
10.1.3.5 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 insure proper operation of the function:
1. Connect three-phase generator currents and voltages to one CVGAPC instance (for
example, GF05)
2. Set
3. Set
shall be used for restraining. Alternatively, positive sequence voltage can be used for
restraining by selecting
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
8. If required set minimum operating time for this curve by using parameter
(default value 0.05s)
9. Set
10. Set
11. Set
12. Set
13. Set
14. Set
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.
10.1.3.6

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:
• Maximum generator capability to contentiously absorb reactive power at zero active
loading 38% of the generator MVA rating
• Generator pull-out angle 84 degrees
This functionality can be achieved by using one CVGAPC function. The following shall be done
in order to insure proper operation of the function:
1. Connect three-phase generator currents and three-phase generator voltages to one
CVGAPC instance (for example, GF02)
2. Set parameter
3. Set 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. Set parameter
210
CurrentInput to value MaxPh
VoltageInput to value MinPh-Ph (it is assumed that minimum phase-to-phase voltage
PosSeq for this setting parameter)
CurveType_OC1 to value ANSI Very inv
StartCurr_OC1 to value 185%
VCntrlMode_OC1 to On
VDepMode_OC1 to Slope
VDepFact_OC1 to value 0.25
UHighLimit_OC1 to value 100%
ULowLimit_OC1 to value 25%
CurrentInput to PosSeq
VoltageInput to PosSeq
RCADir to value -84 degree (that is, current lead voltage for this angle)
1MRK 511 358-UEN A
M13088-158 v3
tMin_OC1
M13088-182 v3
Application manual