Voltage Restrained Overcurrent Protection For Generator And Step-Up Transformer - ABB 650 series Applications Manual

Section 6
Multipurpose protection
6.1.3.5
86
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 StartCurr_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 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 StartCurr_OC1 to value 185%
10. Set VCntrlMode_OC1 to On
11. Set VDepMode_OC1 to Slope
1MRK 511 423-UEN A
M13088-158 v4
Bay control REC650 2.2 IEC
Application manual