ABB Relion REC670, Applications Manual

Page: 432 / 658

TR8ATCC (90) in adapt mode will continue the calculation of V
di
, but instead of
adding V
di
to the measured busbar voltage, it will compare it with the deadband
D
V.
The following control rules are used:
1. If V
di
is positive and its modulus is greater than
D
V, then initiate an VLOWER
command. Tapping will then take place after appropriate t1/t2 timing.
2. If V
di
is negative and its modulus is greater than
D
V, then initiate an VRAISE
command. Tapping will then take place after appropriate t1/t2 timing.
3. If V
di
modulus is smaller than
D
V, then do nothing.
The binary output signal ADAPT on the TR8ATCC (90) function block will be
activated to indicate that this TR8ATCC (90) is adapting to another TR8ATCC (90) in
the parallel group.
It shall be noted that control with adapt mode works as described under the condition
that only one transformer in the parallel group is set to manual mode via the binary
input MANCTRL or, the local HMI
Main menu/Control/Commands/
TransformerVoltageControl(ATCC,90)/TR8ATCC:x .
In order to operate each tap changer individually when the circulating current method
is used, the operator must set each TR8ATCC (90) in the parallel group, in manual.
Adapt mode (operation with the master follower method)
SEMOD159053-234 v5
When in master follower mode, the adapt situation occurs when the setting
OperationAdapt is Enabled , and the master is put in manual control with the followers
still in parallel master-follower control. In this situation the followers will continue to
follow the master the same way as when it is in automatic control.
If one follower in a master follower parallel group is put in manual mode, still with the
setting
OperationAdaptEnabled , the rest of the group will continue in automatic master
follower control. The follower in manual mode will of course disregard any possible
tapping of the master. However, as one transformer in the parallel group is now
exempted from the parallel control, the binary output signal ADAPT on TR8ATCC
(90) function block will be activated for the rest of the parallel group.
Plant with capacitive shunt compensation (for operation with the
circulating current method)
SEMOD159053-238 v4
If significant capacitive shunt generation is connected in a substation and it is not
symmetrically connected to all transformers in a parallel group, the situation may
require compensation of the capacitive current to the ATCC.
An asymmetric connection will exist if for example, the capacitor is situated on the LV-
side of a transformer, between the CT measuring point and the power transformer or at
a tertiary winding of the power transformer, see figure
177 . In a situation like this, the
capacitive current will interact in opposite way in the different ATCCs with regard to
Section 14
1MRK 511 401-UUS A
Control
426 Bay control REC670 2.2 ANSI
Application manual