ABB REG670 Applications Manual page 570

Section 15
Control
564
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 OperHoming = On for that 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 U
of a single transformer. The "disconnected transformer" will then automatically
initiate URAISE or ULOWER commands (with appropriate t1 or t2 time delay)
in order to keep the LV side of the 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 = On, 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 OperationAdapt must be set On,
then the control mode for one TR8ATCC 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 are left in "Automatic". TR8ATCCs 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.
TR8ATCC in adapt mode will continue the calculation of U
to the measured busbar voltage, it will compare it with the deadband DU. The
U
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following control rules are used:
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
1MRK 502 071-UEN -
for control
set
, but instead of adding
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Application manual