Loss Of Excitation Protection For A Generator - Hitachi Relion 670 Series Applications Manual

1MRK511407-UUS Rev. N
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.
11.1.4.6

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, CVGAPC:2)
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 PickupCurr_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&V
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
77 shows overall protection characteristic
Furthermore the other build-in protection elements can be used for other protection and alarming
purposes.
Phasor measurement unit RES670
Application manual
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Section 11
Multipurpose protection
M13088-182 v4
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