During the installation and commissioning, the behavior of the voltage control
functions for different tests may be governed by a parameter group, available
on the local HMI under Main menu/Settings/IED Settings/Control/
TransformerVoltageControl(ATCC,90)/TR1ATCC:x/TR8ATCC:x. These
parameter settings can cause a Total Block, Automatic Block or Alarm for a
variety of system conditions including over and under voltage, over current and
tap changer failure. It is important to review these settings and confirm the
intended response of the voltage control function for different secondary
injection tests.
Terminology
The busbar voltage U
B
is a shorter notation for the measured voltages UL1, UL2, UL3 or Uij,
where Uij is the phase-phase voltage, Uij = Ui -Uj, or Ui, where Ui is one single-phase-to-earth
voltage.
I
L
is a shorter notation for the measured load current; it is to be used instead of the three-
phase quantities IL1, IL2, IL3 or the two-phase quantities Ii and Ij, or single-phase current Ii.
Also note that for simplicity, the Parameter Setting menu structures included in
the following procedure are referred to universally as VCP1, for example, Main
menu/Settings/IED Settings/Control/
TransformerVoltageControl(ATCC,90)/TR1ATCC:x/TR8ATCC:x/Time/t1 and
t2l.
For cases where single-mode voltage control is implemented, the Parameter Setting menu
structure includes TR1ATCC:1 instead of the parallel designator TR8ATCC:1.
12.10.3.1
Secondary test
SEMOD175185-145 v5
The voltage control function performs basic voltage regulation by comparing a calculated load
voltage (U
L
) against a voltage range defined by setting
UDeadband (with upper and lower
limits U2 and U1 respectively). The calculated load voltage U
L
represents the secondary
transformer bus voltage U
B
adjusted for Load drop compensation (LDC) where enabled in
settings.
Note that when LDC is disabled, U
B
equals U
L
.
When the load voltage U
L
stays within the interval between U1 and U2, no action will be taken.
If U
L
< U1 or U
L
> U2, a command timer will start, which is constant time or inverse time
defined by setting
t1 and t1Use. The command timer will operate while the measured voltage
stays outside the inner deadband (defined by setting
UDeadbandInner).
If U
L
remains outside of the voltage range defined by
UDeadband and the command timer
expires, the voltage control will execute a raise or lower command to the transformer tap
changer. This command sequence will be repeated until U
L
is brought back within the inner
deadband range.
12.10.3.2
Check the activation of the voltage control operation
SEMOD175185-537 v9
1MRK 502 067-UEN B
Section 12
Testing functionality by secondary injection
213
Commissioning manual
