ABB RELION RET670, Applications Manual

Page: 772 / 1016

two inputs are pulse activated, and the most recent activation is valid that is, an
activation of any of these two inputs overrides previous activations. If none of these
inputs has been activated, the default is that the transformer acts as a follower (given of
course that the settings are parallel control with the master follower method).
When the selection of master or follower in parallel control, or automatic control in
single mode, is made with a three position switch in the substation, an arrangement as
in figure
366 below is arranged with application configuration.
Figure 366: Principle for a three-position switch Master/Follower/Single
Parallel control with the reverse reactance method
SEMOD159053-145 v4
Consider Figure 367 with two parallel transformers with equal rated data and similar
tap changers. The tap positions will diverge and finally end up in a runaway tap
situation if no measures to avoid this are taken.
Load
T1
I
L
T2
V
B
V
L
I
T1
I
T2
en06000486_ansi.vsd
ANSI06000486 V1 EN-US
Figure 367: 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 .
Section 15
1MRK 504 163-UUS A
Control
766 Transformer protection RET670 2.2 ANSI
Application manual