Functionality - ABB RELION Series Technical Manual

1MRS758755 A
10.4.3
10.4.4
REC615 and RER615
Technical Manual

Functionality

The voltage unbalance function VSQVUB 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. VSQVUB 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.
VSQVUB 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.
VSQVUB 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. VSQVUB 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 "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
U_RMS_A
U_RMS_B
U_RMS_C
BLOCK
BLK_ALARM
RESET
GUID-6D371A54-607F-4073-A604-F8C86B1EDB43 V1 EN
Figure 372: Functional module diagram
Power quality measurement functions
U1
U2
U0
Average calculation
Section 10
AL_MN_IMB
Voltage
unbalance
detector
AL_PCT_IMB
Percentile
calculation
OBS_PR_ACT
699