The function contains a blocking functionality. It is possible to block a set of
function outputs or the function itself, if desired.
10.4.4
Operation principle
The function can be enabled and disabled with the
Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of VSQVUB can be described with a module diagram. All the modules
in the diagram are explained in the next sections.
U3P
BLOCK
Average calculation
Voltage
unbalance
detector
AL_MN_IMB
AL_PCT_IMB
OBS_PR_ACT
Percentile
calculation
U_RMS_A
U_RMS_B
U_RMS_C
U1
U2
U0
RESET
BLK_ALARM
Figure 586: Functional module diagram
Average calculation
VSQVUB calculates two sets of measured voltage unbalance values, a three-second
and a ten-minute non-sliding average value. The three-second average value is
used for continuous monitoring. The ten-minute average is used for percentile
calculation for a longer period.
The Average calculation module uses five different methods for the average
calculation. The required method can be selected with the
Unb detection method
parameter.
When the "Neg Seq" mode is selected with
Unb detection method, the voltage
unbalance is calculated based on the negative-sequence voltage magnitude.
Similarly, when the "Zero Seq" mode is selected, the voltage unbalance is calculated
based on the zero-sequence voltage magnitude. When the "Neg to Pos Seq" mode
is selected, the voltage unbalance is calculated based on the ratio of the negative-
sequence voltage magnitude to the positive-sequence magnitude. When the "Zero
to Pos Seq" mode is selected, the voltage unbalance is calculated based on the ratio
of the zero-sequence voltage magnitude to the positive-sequence magnitude. When
the "Ph vectors Comp" mode is selected, the ratio of the maximum phase voltage
magnitude deviation from the mean voltage magnitude to the mean of the phase
voltage magnitude is used for voltage unbalance calculation.
1MRS757644 H
Power quality measurement functions
620 series
Technical Manual
1109
