ABB Relion 670 Series Applications Manual page 212

Section 8
Current protection
StartVolt : Operation phase-to-phase voltage level given in % of UBase for the under-voltage
stage. Typical setting may be, for example, in the range from 70% to 80% of the rated voltage
of the generator.
tDef_UV : Definite time delay. Since it is related to a backup protection function, a long time
delay (for example
activation of the start and the trip outputs.
EnBlkLowV : This parameter enables the internal block of the undervoltage stage for low
voltage condition; the voltage level is defined by the parameter
BlkLowVolt : Voltage level under which the internal blocking of the undervoltage stage is
activated; it is set in % of
setting can be very low, for example, lower than 10%.
VDepMode : Selection of the characteristic of the start level of the overcurrent stage as a
function of the phase-to-phase voltage; two options are available: Slope and Step. See
Technical Manual for details about the characteristics.
VDepFact : Slope mode : it is the start level of the overcurrent stage given in % of StartCurr
when the voltage is lower than 25% of
VDepFact * StartCurr /100* IBase ; 0.25* UBase ). Step mode : it is the start level of the
(
overcurrent stage given in % of
UBase .
100*
UHighLimit : when the measured phase-to-phase voltage is higher than UHighLimit /
UBase , than the start level of the overcurrent stage is StartCurr /100* IBase . In particular, in
100*
Slope mode it define the second point of the characteristic ( StartCurr /100* IBase ; UHighLimit /
UBase ).
100*
8.16.3.2 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
2. Set
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
inv.
5. Set the multiplier
6. Set
inverse time characteristic.
7. If required, set the minimum operating time for this curve by using the parameter
(default value 0.05 s).
8. Set
206
0.5 s or more) is typically used. Note that the value set is the time between
UBase . This setting must be lower than the setting StartVolt . The
Operation to On
GlobalBaseSel to the right value in order to select the Global Base Values Group with
Characterist to match the type of overcurrent curves used in the network IEC Very
k = 1 (default value).
tDef_OC = 0.00 s, in order to add no additional delay to the trip time defined by the
StartCurr to the value 185%.
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UBase ; so it defines the first point of the characteristic
StartCurr when the voltage is lower than UHighLimit /
1MRK 511 401-UEN Rev. K
BlkLowVolt .
GUID-263B960B-2280-461C-B455-F17B7D278F60 v8
tMin
Bay control REC670
Application manual