ABB RET670 Applications Manual page 568

Section 3
IED application
562
1. Connect three-phase currents from the protected object to one CVGAPC instance
(for example, GF03)
2. Set CurrentInput to value UnbalancePh
3. Set EnRestrainCurr to On
4. Set RestrCurrInput to MaxPh
5. Set RestrCurrCoeff to value 0.97
6. Set base current value to the rated current of the protected object in primary amperes
7. Enable one overcurrent step (for example, OC1)
8. Select parameter CurveType_OC1 to value IEC Def. Time
9. Set parameter PickupCurr_OC1 to value 5%
10. Set parameter tDef_OC1 to desired time delay (for example, 2.0s)
Proper operation of 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 restrain current and its coefficient will as well be applicable
for OC2 step as soon as it is enabled.
Furthermore the other built-in protection elements can be used for other protection and
alarming purposes. For example, in case of generator application by enabling OC2 step
with set pickup to 200% and time delay to 0.1s simple but effective protection against
circuit breaker head flashover protection is achieved.
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 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)
1MRK504116-UUS C
Application manual