Voltage-Restrained Overcurrent Protection For Generator And Step-Up Transformer - ABB REG670 Applications Manual

Section 9
Current protection
9.14.3.2
9.14.3.3
398
UHighLimit: when the measured phase-to-phase voltage is higher than UHighLimit/
100*UBase, than the start level of the overcurrent stage is StartCurr/100*IBase. In
particular, in Slope mode it define the second point of the characteristic (StartCurr/
100*IBase ; UHighLimit/100*UBase).
Voltage-restrained overcurrent protection for generator and step-up
transformer
An example of how to use VRPVOC function to provide voltage restrained
overcurrent protection for a generator is given below. Let us assume that the time
coordination study gives the following required settings:
• Inverse Time Over Current IDMT curve: IEC very inverse, with multiplier k=1
• Start current of 185% of generator rated current at rated generator voltage
• Start current 25% of the original start current value for generator voltages below
25% of rated voltage
To ensure proper operation of the function:
1. Set Operation to On
2. Set GlobalBaseSel to the right value in order to select the Global Base Values
Group with UBase and IBase equal to the rated phase-to-phase voltage and the
rated phase current of the generator.
3. Connect three-phase generator currents and voltages to VRPVOC in the
application configuration.
4. Select Characterist to match the type of overcurrent curves used in the network
IEC Very inv.
5. Set the multiplier k = 1 (default value).
6. Set tDef_OC = 0.00 s, in order to add no additional delay to the trip time defined
by the inverse time characteristic.
7. If required, set the minimum operating time for this curve by using the parameter
tMin (default value 0.05 s).
8. Set StartCurr to the value 185%.
9. Set VDepMode to Slope (default value).
10. Set VDepFact to the value 25% (default value).
11. Set UHighLimit to the value 100% (default value).
All other settings can be left at the default values.
General settings
Operation: With the parameter Operation the function can be set On/Off.
Common base IED values for primary current (IBase), primary voltage (UBase) and
primary power (SBase) are set in Global base values for settings function GBASVAL.
Setting GlobalBaseSel is used to select a GBASVAL function for reference of base
values.
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
1MRK 502 071-UEN -
Application manual