ABB RELION RER670, Applications Manual

Page: 304 / 506

If the parameter MFMode is set to Follow Tap , then the followers will read the tap
position of the master and adopt to the same tap position or to a tap position with
an offset relative to the master, and given by setting parameter
TapPosOffs
(positive or negative integer value). The setting parameter tAutoMSF introduces a
time delay on URAISE/ULOWER commands individually for each follower when
setting
MFMode has the value Follow Tap .
Selecting a master is made by activating the input FORCMAST in TR8ATCC
function block. Deselecting a master is made by activating the input RSTMAST.
These 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
127 below is arranged with application configuration.
M
F
I
SNGLMODE
FORCMAST
RSTMAST
BIM/IOM TR8ATCC
IEC06000633-2-en.vsd
IEC06000633 V2 EN-US
Figure 127: Principle for a three-position switch Master/Follower/Single
Parallel control with the reverse reactance method
SEMOD159053-145 v4
Consider Figure 128 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.
Section 12
1MRK 506 375-UEN A
Control
298 Railway application RER670 2.2 IEC
Application manual