ABB Relion 670 Series Applications Manual page 375

1MRK 511 401-UUS F
T1
V
B
V
L
ANSI06000486 V1 EN-US
Figure 179: Parallel transformers with equal rated data.
In the reverse reactance method, the line voltage drop compensation is used. The original of the
line voltage drop compensation function purpose is to control the voltage at a load point further
out in the network. The very same function can also be used here to control the voltage at a load
point inside the transformer, by choosing a negative value of the parameter
Figure 180, shows a vector diagram where the principle of reverse reactance has been introduced
for the transformers in figure 179. The transformers are here supposed to be on the same tap
position, and the busbar voltage is supposed to give a calculated compensated value V
coincides with the target voltage
ANSI06000485 V1 EN-US
Figure 180: Vector diagram for two transformers regulated exactly on target voltage.
A comparison with figure
reverse reactance control is made with a value with opposite sign on X
"reverse reactance" or "negative reactance". Effectively this means that, whereas the line voltage
drop compensation in figure
load point voltage V
(actually, by adjusting the ratio X
Bay control REC670
Application manual
T2
I
I
T2
T1
I L
Load
en06000486_ansi.vsd
V
B
I =I =(I +I )/2
T1 T2 T1 T2
177 gives that the line voltage drop compensation for the purpose of
177 gave a voltage drop along a line from the busbar voltage V
, the line voltage drop compensation in figure
L
L
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VSet .
R I =R I
L T1 L T2
jX I =jX I
L T1 L T2
en06000485_ansi.vsd
/R with respect to the power factor, the length of the vector V
L
Xline .
that
L
, hence the designation
L
180 gives a voltage increase
Section 14
Control
to a
B
L
369