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
StartCurr_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
UHighLimit_OC1
to value 100%
14. Set
ULowLimit_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.
10.1.3.6 Loss of excitation protection for a generator
M13088-182 v3
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
CurrentInput
to
PosSeq
3. Set parameter
VoltageInput
to
PosSeq
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
RCADir
to value -84 degree (that is, current lead voltage for this angle)
7. Set parameter
ROADir
to value 90 degree
8. Set parameter
LowVolt_VM
to value 5%
9. Enable one overcurrent step (for example, OC1)
10. Select parameter
CurveType_OC1
to value
IEC Def. Time
11. Set parameter
StartCurr_OC1
to value 38%
12. Set parameter
tDef_OC1
to value 2.0s (typical setting)
13. Set parameter
DirMode_OC1
to
Forward
14. Set parameter
DirPrinc_OC1
to
IcosPhi&U
15. Set parameter
ActLowVolt1_VM
to
Block
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. However it shall be noted that set
values for RCA & ROA angles will be applicable for OC2 step if directional feature is enabled for
this step as well. Figure
118 shows overall protection characteristic
Section 10 1MRK 505 370-UEN D
Multipurpose protection
236 Busbar protection REB670
Application manual
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