ABB RET670 - Page 217

RAISE and LOWER commands executed by the Master in the local HMI
under Main menu/Settings/General settings/Control/
TransformerVoltageControl(ATCC,90)/VCPx/MFMode
Note that the maximum difference in tap positions for parallel
transformers will be determined by the setting in the
Parameter Setting tool under Main menu/Settings/Setting
group N/Control/TransformerVoltageControl(ATCC,90)/
VCPx/ParCtrl/MFPosDiffLim and that tap differences
exceeding that setting can produce system alarms or blocking
of the VCTR.
5. For parallel operation, it is also recommended to confirm settings for parallel
group membership, of the setting TnRXOP in the Parameter Setting tool
under Main menu/Settings/Setting group N/Control/
TransformerVoltageControl(ATCC,90)/VCPx/ParCtrl
In the Parameter Setting tool, the general parallel arrangement of transformers
are defined by setting TnRXOP to On or Off. The following rules are
applicable on the settings T1RXOP - T4RXOP.
If terminal T1 and T2 are connected,
• T1RXOP shall be set to On in instance 2 of TR8ATCC, and
• T2RXOP shall be set to On in instance 1 of TR8ATCC.
If T1 - T3 are available,
• T1RXOP
and T2RXOP shall be set to On in instance 3 of TR8ATCC, and
• T2RXOP and T3RXOP shall be set to On in instance 1 of TR8ATCC,
and so on.
The parameter corresponding to the own IED must not be set.
T1RXOP should thus not be set in IED T1, T2RXOP not in
IED T2, and so on.
6. Set the parallel operation (OperationPAR) to Off for each transformer.
7.
On the local HMI, set the control mode to Manual for each transformer in the
parallel control group.
8. Undertaking switching operations to connect all transformers to the same bus
on the secondary side.
9. Set OperationPAR to MF for all transformers in the parallel group and
confirm that the lowest transformer number in the group is set as Master.
Allow the issue of RAISE and LOWER commands so that the secondary bus
voltage stabilizes at USet.
10. Change USet in the Master transformer T1 so that it is 1% below the
measured bus voltage value on the local HMI and set all transformers to
automatic control mode using the local HMI.
11. The Master in the parallel group will issue a LOWER command after time
delay t1, which will also be repeated by the Follower transformers in the group.
12. Return USet for T1 to its normal in the service value.
1MRK 504 088-UEN C Section 14
Primary injection testing
211
Installation and commissioning manual