Minimum Circulating Current (Mcc) Method - ABB Relion 670 Series Commissioning Manual

1MRK 511 403-UUS Rev. K
For parallel operation, it is also recommended to confirm the setting for the general parallel arrangement
of transformers in Main menu /Settings/IED Settings /Control/TransformerVoltageControl(90, U↕) /
TR8ATCC(90, U↕||):x/ParCtrl . General parallel arrangement of transformers are defined by setting
TnRXOP to On or Off. The following rules are applicable for the settings of T1RXOP – T8RXOP.
• In each instance of TR8ATCC, set all TnRXOP parameters corresponding to the connected IEDs to
Enabled except the parameter corresponding to the IED itself. For example, do not set T1RXOP to
Enabled in IED T1 or T2RXOP to Enabled in IED T2.
For example, if IEDs T1, T2 and T3 are connected,
• In instance 1 of TR8ATCC (90), set T2RXOP and T3RXOP to Enabled.
• In instance 2 of TR8ATCC (90), set T1RXOP and T3RXOP to Enabled.
• In instance 3 of TR8ATCC (90), set T1RXOP and T2RXOP to Enabled.
12.1.3

Minimum Circulating Current (MCC) method

Voltage control of parallel transformers with the circulating current method means minimizing the
circulating current at a given voltage target value. The busbar voltage (VB) is measured individually for
each transformer in the parallel group by its associated TR8ATCC function. These measured values are
then exchanged between the transformers, and in each TR8ATCC block, the mean value of all VB values
is calculated. The resulting value VBmean is then used in each IED instead of VB for the voltage
regulation.
1. Check the overcurrent blocking level (Iblock) in Main menu /Settings/IED Settings /Control/
TransformerVoltageControl(90, U↕) /TR8ATCC(90, U↕||):x/TCCtrl/Iblock.
2. Check that the circulating current blocking (OperCCBlock) is set On, and the check the correct
settings for circulating current limit (CircCurLimit) in Main menu/Settings /IED Settings/Control /
TransformerVoltageControl(90, U↕)/TR8ATCC(90, U↕||):x/ParCtrl/CircCurrLimit .
3. Connect all transformers in the parallel group to the same busbar on the secondary side.
4. Open the test display for Transformer Voltage Control on the LHMI in Main menu /Test/Function
status /Control/TransformerVoltageControl(90, U↕) .
5. Manually execute Raise commands to step up the tap changer for transformer T1 to two steps
above the setting for the other transformers in the parallel group.
6. Check that the value of IPRIM is below the overcurrent blocking level (Iblock)
7. Check that the value of ICIRCUL is below the circulating current limit (CircCurLimit).
Bay control REC670
Commissioning manual
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IEC13000252-1-en.vsd
Section 12
Primary injection testing
SEMOD176327-195 v5
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