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8.14.3.1
Explanation of the setting parameters
GUID-9B777E6D-602B-4214-9170-A44ED2D725BF v3
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
to
0 s if the inverse time characteristic is chosen and no additional delay shall be added. Note
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
0.5 s or more) is typically used. Note that the value set is the time between
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.
BlkLowVolt: Voltage level under which the internal blocking of the undervoltage stage is
activated; it is set in % of
UBase. This setting must be lower than the setting StartVolt. The
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
UBase; so it defines the first point of the characteristic
(
VDepFact*StartCurr/100*IBase ; 0.25*UBase). Step mode: it is the start level of the
overcurrent stage given in % of
StartCurr when the voltage is lower than UHighLimit/
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/
100*
UBase).
8.14.3.2
Voltage-restrained overcurrent protection for generator and step-up
transformer
GUID-263B960B-2280-461C-B455-F17B7D278F60 v8
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:
1MRK 505 343-UEN B
Section 8
Current protection
463
Application manual
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