Figure. 5.3.9 - 108. Simplified function block diagram of the U< function.
Measured input
The function block uses analog voltage measurement values. The monitored magnitudes are equal
to RMS values. A -20 ms averaged value of the selected magnitude is used for pre-fault data
registering.
Table. 5.3.9 - 96. Measurement inputs of the U< function.
Signal
Description
Time base
U
L12
RMS
RMS measurement of voltage U
L12
/V
5ms
U
L23
RMS
RMS measurement of voltage U
L23
/V
5ms
U
L31
RMS
RMS measurement of voltage U
L31
/V
5ms
U
L1
RMS
RMS measurement of voltage U
L1
/V
5ms
U
L2
RMS
RMS measurement of voltage U
L2
/V
5ms
U
L3
RMS
RMS measurement of voltage U
L3
/V
5ms
Pick-up
The
U
set
setting parameter controls the pick-up of the U< function. This defines the minimum allowed
measured voltage before action from the function. The function constantly calculates the ratio
between the
U
set
and the measured magnitude (
U
m
) for each of the three voltages. The reset ratio of
103 % is built into the function and is always relative to the
U
set
value. The setting value is common for
all measured amplitudes, and when the
U
m
exceeds the
U
set
value (in single, dual or all voltages) it
triggers the pick-up operation of the function.
Table. 5.3.9 - 97. Pick-up settings.
Name
Description
Range
Step
Default
U
set
Pick-up setting
20.00…120.00%U
n
0.01%U
n
60%U
n
U Block
setting
Block setting. If set to zero, blocking is not in use. The operation is
explained in the next chapter.
0.00…100.00%U
n
0.01%U
n
10%U
n
A
AQ
Q-C213
-C213
Instruction manual
Version: 2.04
150