ABB Relion 670 Series Applications Manual page 379

1MRK 511 401-UUS F
transformers have equal magnitude of V
one is going to tap first.
Avoidance of simultaneous tapping (operation with the master follower method)
A time delay for the follower in relation to the command given from the master can be set when
the setting
without an offset) of the master. The setting parameter
VRAISE/VLOWER commands individually for each follower, and effectively this can be used to
avoid simultaneous tapping.
Homing
Homing (operation with the circulating current method)
This function can be used with parallel operation of power transformers using the circulating
current method. It makes possible to keep a transformer energized from the HV side, but open on
the LV side (hot stand-by), to follow the voltage regulation of loaded parallel transformers, and
thus be on a proper tap position when the LV circuit breaker closes.
For this function, it is needed to have the LV VTs for each transformer on the cable (tail) side (not
the busbar side) of the CB, and to have the LV CB position hardwired to the IED.
In TR8ATCC block for one transformer, the state "Homing" will be defined as the situation when
the transformer has information that it belongs to a parallel group (for example, information on
T1INCLD=1 or T2INCLD=1 ... and so on), at the same time as the binary input DISC on TR8ATCC
block is activated by open LV CB. If now the setting parameter
transformer, TR8ATCC will act in the following way:
• The algorithm calculates the "true" busbar voltage, by averaging the voltage measurements of
the other transformers included in the parallel group (voltage measurement of the
"disconnected transformer" itself is not considered in the calculation).
• The value of this true busbar voltage is used in the same way as V
transformer. The "disconnected transformer" will then automatically initiate VRAISE or
VLOWER commands (with appropriate
transformer within the deadband of the busbar voltage.
Homing (operation with the master follower method)
If one (or more) follower has its LV circuit breaker open and its HV circuit breaker closed, and if
OperHoming = Enabled , this follower continues to follow the master just as it would have made
with the LV circuit breaker closed. On the other hand, if the LV circuit breaker of the master opens,
automatic control will be blocked and TR8ATCC function output MFERR will be activated as the
system will not have a master.
Adapt mode, manual control of a parallel group
Adapt mode (operation with the circulating current method)
When the circulating current method is used, it is also possible to manually control the
transformers as a group. To achieve this, the setting
the control mode for one TR8ATCC (90) shall be set to "Manual" via the binary input MANCTRL or
the local HMI under Main menu/Control/Commands/TransformerVoltageControl(ATCC,90)/
TR8ATCC:x whereas the other TR8ATCCs (90) are left in "Automatic". TR8ATCCs (90) in automatic
mode will then observe that one transformer in the parallel group is in manual mode and will then
automatically be set in adapt mode. As the name indicates they will adapt to the manual tapping
of the transformer that has been put in manual mode.
Bay control REC670
Application manual
MFMode is Follow Tap that is, when the follower follows the tap position (with or
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then there is a predetermined order governing which
di
tAutoMSF then introduces a time delay on
OperHoming = Enabled for that
t1 or t2 time delay) in order to keep the LV side of the
OperationAdapt must be set Enabled , then
Section 14
Control
SEMOD159053-197 v2
SEMOD159053-200 v2
SEMOD159053-205 v3
for control of a single
set
SEMOD159053-216 v3
SEMOD159053-219 v2
SEMOD159053-221 v5
373