t1=180
t1=150
t1=120
t1=90
t1=60
t1=30
IEC06000488_2_en.vsd
IEC06000488 V2 EN-US
Figure 152: Inverse time characteristic for TR1ATCC and TR8ATCC
The second time delay,
t2
, will be used for consecutive commands (commands in the same
direction as the first command). It can have a definite or inverse time characteristic according
to the setting
t2Use
(Constant/Inverse). Inverse time characteristic for the second time delay
follows the similar formulas as for the first time delay, but the
t2
setting is used instead of
t1
.
Line voltage drop
SEMOD159053-105 v6
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
153 shows the vector diagram for a line modelled as a series impedance with the
voltage U
B
at the LV busbar and voltage U
L
at the load center. The load current on the line is I
L
,
the line resistance and reactance from the station busbar to the load point are R
L
and X
L
. The
angle between the busbar voltage and the current, is j. If all these parameters are known U
L
can be obtained by simple vector calculation.
Values for R
L
and X
L
are given as settings in primary system ohms. If more than 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
L
will be used by the Automatic voltage control
for tap changer function, TR1ATCC for single control and TR8ATCC for parallel control for
voltage regulation instead of U
B
. However, TR1ATCC or TR8ATCC will still perform the
following two checks:
1. The magnitude of the measured busbar voltage U
B
, shall be within the security 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
comes back
within the range.
2. The magnitude of the calculated voltage U
L
at the load point, can be limited such that it is
only allowed to be equal to or smaller than the magnitude of U
B
, otherwise U
B
will be used.
However, a situation where U
L
>U
B
can be caused 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
.
Section 13 1MRK 511 358-UEN A
Control
302
Application manual
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