Master Follower (Mf) Method - ABB Relion 670 Series Commissioning Manual

Section 12
Primary injection testing
Comp is a setting for circulating current Compensating Factor, and it is effectively a
multiplier value to change the sensitivity of the voltage regulation function to measured
values of circulating current. A nominal value of 200 for
achieve sensitive voltage regulation. Smaller values may lead to a normal state where tap
changers for parallel transformers are well out of step, and values significantly higher will
cause over-sensitivity in the voltage control function and tap changer hunting behavior. It
is an important outcome of the testing process that the compensating factor is checked
for each transformer to ensure sensitive but stable operation for circulating currents.
For example, if there are three transformers connected in parallel, and the tap changer of
transformer T1 is two steps over the tap changer of T2 and T3, the circulating current
detected by the VCTR for T1 will be the sum (with opposite sign) of the current measured
at T2 and T3. The currents measured at T2 and T3 will ideally be about the same values. If
the voltage is close to the upper limit of the
decrease the controlled voltage. In the opposite case, that is, the voltage is close to the
lower limit of
voltage. The tap changer for T2 and T3 will not operate due to the fact that the detected
circulating current will be half of the current detected at T1. The setting of the parameter
Comp then might need to be increased a little. At least one tap changer step difference
between the different transformers should be allowed in order to avoid the tap changers
to operate too often. If the allowed difference is, for example, two steps, the tap changer
shall be stepped up three steps when setting the parameter
10. Set the
described procedure when the tap changer of one transformer is two steps above the
others, it shall automatically step down. When there are only two transformers in the
group either shall one step down or the other step up depending on the voltage level at
the ATCC.
12.1.4

Master Follower (MF) method

The Master Follower method requires a Master to be nominated in a parallel group. It is
responsible for measuring secondary bus voltage and executing commands to raise and lower
tap changers, which are repeated by Follower transformers in the group.
1. Confirm the voltage blocking levels
Settings/IED Settings/Control/TransformerVoltageControl(ATCC,90)/TR8ATCC:x/
Voltage/Umax,Umin.
2. Check that
Settings/Control/TransformerVoltageControl(ATCC,90)/TR8ATCC:x/MFMode.
If this setting is
of the Master, while
and LOWER commands executed by the Master.
3. Confirm the maximum difference in tap positions for parallel transformers. The number
of taps is determined by the setting in the Parameter Setting tool under Main menu/
Settings/IED Settings/Control/TransformerVoltageControl(ATCC,90)/TR8ATCC:x/
ParCtrl/MFPosDiffLim
4. Connect all transformers in the parallel group to the same busbar on both the primary
and secondary sides.
5. Set the control mode to
6. Open the test display for Transformer Voltage Control on the LHMI in Main menu/Test/
Function status/Control/TransformerVoltageControl (ATCC, 90).
192
UDeadband , the tap changer at T1 will not try to decrease the controlled
Comp parameter for T2 and T3 in the same manner as for T1. According to the
MFMode is set to Follow Tap or Follow Cmd in Main menu/Settings/IED
Follow Tap , all Follower transformers shall match the actual tap setting
Follow Cmd requires that Follower transformers follow the RAISE
Manual for each transformer in the parallel control group
© Copyright 2017 ABB. All rights reserved
Comp should be appropriate to
UDeadband , the tap changer of T1 will try to
OVPartBK and UVPpartBK in Main menu/
1MRK 511 403-UEN E
Comp .
SEMOD176327-244 v4
Bay control REC670
Commissioning manual