ABB ret650, Applications Manual

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Load
T1
I
L
T2
U
B
U
L
I
T1
I
T2
en06000486.vsd
IEC06000486 V1 EN-US
Figure 75: 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
Xline .
Figure 76 , shows a vector diagram where the principle of reverse reactance has
been introduced for the transformers in figure 75 . The transformers are here
supposed to be on the same tap position, and the busbar voltage is supposed to give
a calculated compensated value U
L
that coincides with the target voltage USet .
IEC06000485_2_en.vsd
U
B
R
L
I
T1
=R
L
I
T2
jX
L
I
T1
=jX
L
I
T2
I
T1
=I
T2
=(I
T1
+I
T2
)/2
U L1
=U
L2
=U
Set
IEC06000485 V3 EN-US
Figure 76: Vector diagram for two transformers regulated exactly on target
voltage.
A comparison with figure 73 gives that the line voltage drop compensation for the
purpose of reverse reactance control is made with a value with opposite sign on X
L
,
Section 11
1MRK 504 169-UEN A
Control
202 Transformer protection RET650 2.2 IEC
Application manual