Master Follower (Mf) Method - ABB RET670 Commissioning Manual

1MRK 504 165-UEN A
12.1.4
Transformer protection RET670 2.2 IEC
Commissioning manual
the controlled voltage. In the opposite case, that is, the voltage is close to the
lower limit of UDeadband, the tap changer at T1 will not try to decrease the
controlled 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 Comp.
10. Set the Comp parameter for T2 and T3 in the same manner as for T1.
According to 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.

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 OVPartBK and UVPpartBK in Main
menu/Settings/General settings/Control/
TransformerVoltageControl(ATCC,90)/TR8ATCC:x/Voltage/
Umax,Umin.
2. Check that MFMode is set to Follow Tap or Follow Cmd in Main menu/
Settings/General settings/Control/TransformerVoltageControl(ATCC,
90)/TR8ATCC:x/MFMode.
If this setting is Follow Tap, all Follower transformers shall match the actual
tap setting of the Master, while Follow Cmd requires that Follower
transformers follow the RAISE 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/Setting group N/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 Manual for each transformer in the parallel control
group
6. Open the test display for Transformer Voltage Control on the LHMI in Main
menu/Test/Function status/Control/TransformerVoltageControl (ATCC,
90).
Section 12
Primary injection testing
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