Functionality - ABB RELION REX640 Technical Manual

Section 10
Power quality measurement functions
10.4.3
10.4.4
1642

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 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.
VSQVUB contains a blocking functionality. It is possible to block a set of function
outputs or the function itself.
Analog channel configuration
VSQVUB has one analog group input which must be properly configured.
Table 1463: Analog inputs
Input
U3P
See the preprocessing function blocks in this document for the
possible signal sources.
There are a few special conditions which must be noted with the configuration.
Table 1464: Special conditions
Condition
U3P connected to real measurements
Description
Three-phase voltages
Description
The function can work with any two voltage
channels connected but it is recommended to
connect all three voltage channels.
VT connection is "Delta" in that
Further, if
Unb detection
particular UTVTR, the
method cannot be set to "Zero Seq" or "Zero to Pos
Seq".
1MRS759142 C
REX640
Technical Manual