Operation Principle - ABB RELION REX640 Technical Manual

Section 4
Protection functions
4.12.5.4
1052
unbalance which results in non-zero neutral point voltage can be compensated
automatically on a continuous basis.
The function starts when the fundamental (DFT) component of the compensated
neutral unbalance voltage exceeds the set limit. CNUPTOV operates with the definite
time (DT) characteristics.
The function contains a blocking functionality. It is possible to block function outputs,
the definite timer or the function itself.

Operation principle

The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "on" and "off".
The operation of CNUPTOV can be described with a module diagram. All the
modules in the diagram are explained in the next sections.
U_A
U_B
U3P
U_C
U
U
URES
U
UNEUT
BLOCK
GUID-414D46A4-C5A2-4C15-B0E7-3FD0A6EEE1DD V1 EN
Figure 566: Functional module diagram
Natural unbalance compensation
This module calculates the natural unbalance compensation. Calculation for
compensation is initiated through the command Record unbalance, available under
the menu path Control/CNUPTOV. The function equates the operating signal to zero
and calculates from the available known quantities.
U
unb
. This memorized value is then used when calculating the operating quantity.
U ( ) m
unb
For more information, see the
If the positive-sequence voltage is available at the time of memorizing the
value, the positive-sequence voltage is also memorized as
applies the revised compensation voltage to account for change in bus voltages
between the moment of memorizing the compensation voltage and the time of
applying it.
Natural
unbalance Level
compensati detector
1
on
o
neutral
Blocking
logic
Operating quantity
1MRS759142 C
Timer
OPERATE
t
START
is memorized as
U
unb
section in this manual.
. The function then
U m ( )
1
Technical Manual
U m
( )
unb
REX640