ABB REC670 Applications Manual page 392

Section 14
Control
386
Line voltage drop
The purpose with the line voltage drop compensation is to control the voltage, not
at the power transformer low voltage side, but at a point closer to the load point.
Figure 172 shows the vector diagram for a line modelled as a series impedance
with the voltage U at the LV busbar and voltage U
B
current on the line is I , the line resistance and reactance from the station busbar to
L
the load point are R and X
L
current, is j. If all these parameters are known U
vector calculation.
Values for R and X are given as settings in primary system ohms. If more than
L L
one line is connected to the LV busbar, an equivalent impedance should be
calculated and given as a parameter setting.
The line voltage drop compensation function can be turned On/Off by the setting
parameter OperationLDC. When it is enabled, the voltage U
Automatic voltage control for tap changer function, TR1ATCC for single control
and TR8ATCC for parallel control for voltage regulation instead of U
TR1ATCC or TR8ATCC will still perform the following two checks:
1. The magnitude of the measured busbar voltage U
range, (setting Umin and Umax). If the busbar voltage falls-out of this range
the line voltage drop compensation calculations will be temporarily stopped
until the voltage U
B
2. The magnitude of the calculated voltage U
such that it is only allowed to be equal to or smaller than the magnitude of U
otherwise U will be used. However, a situation where U
B
by a capacitive load condition, and if the wish is to allow for a situation like
that, the limitation can be removed by setting the parameter OperCapaLDC to
On.
~
U
L
IEC06000487 V2 EN-US
Figure 172: Vector diagram for line voltage drop compensation
. The angle between the busbar voltage and the
L
comes back within the range.
L
R X
L
L
U
B
U
B
jX I
L L
Re
R I
L L
IEC06000487-2-en.vsd
1MRK 511 401-UEN A
at the load center. The load
L
can be obtained by simple
L
will be used by the
L
. However,
B
, shall be within the security
B
at the load point, can be limited
>U can be caused
L B
Bay control REC670 2.2 IEC
Application manual
SEMOD159053-105 v6
,
B