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Table. 5.4.14. - 131. Analog magnitudes used by the VUB function.
Signal
Description
Time base
U
1
RMS
Fundamental RMS measurement of voltage U
1
/V
5 ms
U
2
RMS
Fundamental RMS measurement of voltage U
2
/V
5 ms
U
3
RMS
Fundamental RMS measurement of voltage U
3
/V
5 ms
In fundamental frequency RMS value the pre-fault condition is presented with 20 ms averaged history
value from -20 ms of Start or Trip event.
Pick-up characteristics
Pick-up of the VUB function is controlled by Uset setting parameter, which de nes the maximum or
minimum allowed calculated U1 or U2 voltage before action from the function. The function constantly
calculates the ratio in between of Uset and calculated U1 or U2 magnitude (Uc). The monitored
voltage is chosen in the INFO-page with the parameter Measured magnitude.
Table. 5.4.14. - 132. Measured magnitude selection.
Name
Description
Range
Default
Measured magnitude
Decision which calculated voltage is supervised
U1 Pos seq.Volt
U2 Neg seq.Volt
U1 Pos seq.Volt
Reset ratio of 97% in over voltage applications is inbuilt in the function and is always related to the
Uset
value. Reset ratio of 103 % in under voltage applications is inbuilt in the function and is always related
to the Uset value. When Uc exceed/decrease above/below the Uset value will cause pick-up operation
of the function.
Table. 5.4.14. - 133. Pick-up characteristics setting
Name
Description
Range
Step
Default
Pick-up
terms
Decision if the function will pick-up when the monitored voltage is under
or over the set pick-up value.
Over >
Under<
-
Over>
Uset
Pick-up setting
5.00…
150.00%Un
0.01%Un 105%Un
Ublk
Under voltage blocking (visible when Pick-up term is Under<)
0.00…
80.00%Un
0.01%Un 5%Un
The pick-up activation of the function is not directly equal to start-signal generation of the function.
Start signal is allowed if blocking condition is not active.
Using Block setting to prevent nuisance trips
In case “Under <” is the chosen tripping condition to prevent the relay from tripping in a situation where
the network is de-energized it is advised to use the
Under block setting Ublk
parameter. When the
measured voltage drops below the set value relay will not give a tripping signal. If the measured voltage
has dropped below the
Under block setting Ublk
the blocking will persist until all of the line voltages
have risen over the U< pick-up setting. Please see the image for a visualization of this function. If block
level is set to zero, blocking is not in use.
AQ-F255
Instruction manual
Version: 2.00
143
© Arcteq Relays Ltd