simultaneously, and consequently they will blindly follow the master irrespective of their
individual tap positions. Effectively this means that if the tap positions of the followers were
harmonized with the master from the beginning, they would stay like that as long as all
transformers in the parallel group continue to participate in the parallel control. On the other
hand for example, one transformer is disconnected from the group and misses a one tap step
operation, and thereafter is reconnected to the group again, it will thereafter participate in the
regulation but with a one tap position offset.
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
154
below is arranged with application configuration.
M
F
I
SNGLMODE
FORCMAST
RSTMAST
BIM/IOM TR8ATCC
IEC06000633-2-en.vsd
IEC06000633 V2 EN-US
Figure 154: Principle for a three-position switch Master/Follower/Single
Parallel control with the reverse reactance method
SEMOD159053-145 v4
Consider Figure 155 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.
1MRK 511 358-UEN A Section 13
Control
305
Application manual
To Next Page
Loading...
