Voltage Control Of Parallel Transformers; Minimum Circulating Current (Mcc) Method - ABB rec670 Commissioning Manual

1MRK 511 360-UEN A
11.1.2
11.1.3
Bay control REC670 2.1 IEC
Commissioning manual

Voltage control of Parallel Transformers

In parallel operation, each transformer protection IED must be connected to the station
communication bus for data exchange. The following procedure assumes that the
necessary pre-configuration in the Parameter Setting tool and the Signal Matrix tool
has been performed and tested to enable data exchange between IEDs or between
instances of voltage control in the same IED.
For parallel operation, it is also recommended to confirm the setting for the general
parallel arrangement of transformers in Main menu/Settings/Setting group N/
Control/TransformerVoltageControl(ATCC,90)/TR8ATCC: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 On except the parameter corresponding to the IED itself. For
example, do not set T1RXOP to On in IED T1 or T2RXOP to On in IED T2.
For example, if IEDs T1, T2 and T3 are connected,
• In instance 1 of TR8ATCC, set T2RXOP and T3RXOP to On.
• In instance 2 of TR8ATCC, set T1RXOP and T3RXOP to On.
• In instance 3 of TR8ATCC, set T1RXOP and T2RXOP to On.

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
(UB) 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 UB values is
calculated. The resulting value UBmean is then used in each IED instead of UB for the
voltage regulation.
1. Check the overcurrent blocking level (Iblock) in Main menu/Settings/General
settings/Control/TransformerVoltageControl(ATCC,90)/TR8ATCC: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/General settings/Control/
TransformerVoltageControl(ATCC,90)/TR8ATCC:x/ParCtrl/
CircCurrLimit.
Section 11
Primary injection testing
193