ABB RET650 Applications Manual page 234

Section 11
Control
228
Rline
j
1
Xline Zline
j
IEC06000626 V1 EN-US
Figure 82: Transformer with reverse reactance regulation and no circulating
current
The voltage DU=U
-U
B L
that if j2 is slightly less than -90°, then U
length as U regardless of the magnitude of the transformer load current I
B
(indicated with the dashed line). The automatic tap change control regulates the
voltage towards a set target value, representing a voltage magnitude, without
considering the phase angle. Thus, U
all be said to be on the target value.
Assume that we want to achieve that j
D = ´
U Z I
ß
0
j
- j
j 90 j j
D = ´
Ue Ze Ie
1
ß
0
j j
- = +
90
1
ß
0
j j
= - -
90
1
EQUATION1938 V1 EN-US
If for example cosj = 0.8 then j = arcos 0.8 = 37°. With the references in
figure 82, j will be negative (inductive load) and we get:
j = - -
- = -
0 0
( 37 ) 90
1
EQUATION1939 V1 EN-US
I
T
*Xline has the argument j2 and it is realised
=I *Rline+j I
T T
will have approximately the same
L
as well as U
B
= -90°, then:
2
j j
+
j ( )
=
ZIe
1
0
53
1MRK 504 169-UEN A
U
L
jI
T
DU
U
j
B
en06000626.vsd
T
and also the dashed line could
L
(Equation 55)
(Equation 56)
Transformer protection RET650 2.2 IEC
Application manual
I *Rline
T
*Xline
2