controlled in a parallel group with the reverse reactance method and with no circulation
(for example, assume two equal transformers on the same tap position). The load
current lags the busbar voltage V
B
with the power factor j and the argument of the
impedance Rline and Xline is designated j1.
V
B
jI
T
*Xline
V
L
Xline
Rline
Zline
I
T
I
T
*Rline
j
j
1
j
2
DV
en06000626_ansi.vsd
ANSI06000626 V1 EN
Figure 288: Transformer with reverse reactance regulation and no circulating current
The voltage DV=V
B
-V
L
=I
T
*Rline+j I
T
*Xline has the argument j2 and it is realised
that if j2 is slightly less than -90°, then V
L
will have approximately the same length as
V
B
regardless of the magnitude of the transformer load current I
T
(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, V
B
as well as V
L
and also the dashed line could all be said to be on the target value.
Assume that we want to achieve that j
2
= -90°, then:
0
1 1
( )
90
0
1
0
1
90
90
j j j
j
j j
j j
+
-
D = ´
ß
D = ´ =
ß
- = +
ß
= - -
j j
j j
V Z I
Ve Ze Ie ZIe
EQUATION1983-ANSI V1 EN (Equation 429)
If for example cosj = 0.8 then j = arcos 0.8 = 37°. With the references in figure 288, j
will be negative (inductive load) and we get:
1MRK504116-UUS C Section 3
IED application
691
Application manual
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