ABB Relion REC670, Applications Manual

Page: 431 / 658

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
OperHoming = Enabled 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 V
set
for control of
a single transformer. The “disconnected transformer” will then automatically
initiate VRAISE or VLOWER 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)
SEMOD159053-216 v3
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
SEMOD159053-219 v2
Adapt mode (operation with the circulating current method)
SEMOD159053-221 v5
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
Enabled , then 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.
1MRK 511 401-UUS A
Section 14
Control
Bay control REC670 2.2 ANSI 425
Application manual