Explanation Of The Setting Parameters; Voltage-Restrained Overcurrent Protection For Generator And Step-Up Transformer - ABB RELION 670 Series Applications Manual

1MRK 505 343-UEN B
8.14.3.1

Explanation of the setting parameters

Operation : Set to On in order to activate the function; set to Off to switch off the complete
function.
StartCurr : Operation phase current level given in % of IBase .
Characterist : Selection of time characteristic: Definite time delay and different types of inverse
time characteristics are available; see Technical Manual for details.
tDef_OC : Definite time delay. It is used if definite time characteristic is chosen; it shall be set
0 s if the inverse time characteristic is chosen and no additional delay shall be added. Note
to
that the value set is the time between activation of the start and the trip outputs.
k : Time multiplier for inverse time delay.
tMin : Minimum operation time for all inverse time characteristics. At high currents the inverse
time characteristic might give a very short operation time. By setting this parameter the
operation time of the step can never be shorter than the setting.
Operation_UV : it sets On / Off the operation of the under-voltage stage.
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
100* UBase .
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 /
UBase ).
100*
8.14.3.2 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:
Application manual
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
UBase ; so it defines the first point of the characteristic
StartCurr when the voltage is lower than UHighLimit /
Current protection
GUID-9B777E6D-602B-4214-9170-A44ED2D725BF v3
BlkLowVolt .
GUID-263B960B-2280-461C-B455-F17B7D278F60 v8
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