Function Block - ABB 615 series Technical Manual

Section 10
Power quality measurement functions
10.4.2
10.4.3
10.4.4
1062

Function block

PQVUB
MN_UNB_AL
V_A
V_B PCT_UNB_AL
V_C OBS_PR_ACT
V
1
V
2
V
0
BLOCK
GUID-5248E9E7-BE34-4B9E-B402-611B2557E536 V2 EN
Figure 540: Function block
Functionality
The voltage unbalance function PQVUB monitors voltage unbalance conditions in power
transmission and distribution networks. It can be applied to identify a network and load
unbalance that can cause sustained voltage unbalance. PQVUB is also used to monitor the
commitment of the power supply utility of providing a high-quality, that is, a balanced
voltage supply on a continuous basis.
PQVUB uses five different methods for calculating voltage unbalance. The methods are
the negative-sequence voltage magnitude, zero-sequence voltage magnitude, ratio of the
negative-sequence voltage magnitude to the positive-sequence voltage magnitude, ratio
of the zero-sequence voltage magnitude to the positive-sequence voltage magnitude and
ratio of maximum phase voltage magnitude deviation from the mean voltage magnitude
to the mean of the phase voltage magnitude.
PQVUB provides statistics which can be used to verify the compliance of the power
quality with the European standard EN 50160 (2000). The statistics over selected period
include a freely selectable percentile for unbalance. PQVUB also includes an alarm
functionality providing a maximum unbalance value and the date and time of occurrence.
The function contains a blocking functionality. It is possible to block a set of function
outputs or the function itself, if desired.
Operation principle
The function can be enabled and disabled with the Operation setting. The corresponding
parameter values are "Enable" and "Disable".
The operation of PQVUB can be described with a module diagram. All the modules in the
diagram are explained in the next sections.
1MAC059074-MB A
615 series ANSI
Technical Manual