Voltage Control Of Parallel Transformers; Minimum Circulating Current (Mcc) Method - ABB RET670 Installation And Commissioning Manual

Section 14
Primary injection testing
14.1.1.3
14.1.1.4
208

Voltage control of Parallel Transformers

Parallel transformer voltage control can be achieved through two methods,
Minimum Circulating Current (MCC – refer to section
Current (MCC) method") and Master Follower (MF – refer to section
Follower (MF) method").
Parallel transformer control can be achieved via:
• a single IED with application configuration for the necessary data transfer, for
up to four transformers, or
• multiple IEDs (with up to 8 VCTR functions in total) communicating via
Goose messages on station bus IEC 61850-8-1
The parallel control functions can be tested directly with operational currents, that
is, with the power transformer in service and loaded.

Minimum Circulating Current (MCC) method

The method is used when two or more transformers are to be parallel controlled. A
maximum of four transformers can be controlled simultaneously.
To use this method, each transformer protection IED must be connected to the
station communication bus, to exchange data. The following test procedure will
assume that the necessary pre-configuration in the Parameter Setting tool and the
Signal Matrix tool has occurred to enable data exchange between IEDs or between
instances of voltage control in the same IED.
Procedure
1. Confirm or set the correct USet and UDeadband in service values.
2. Set the correct overcurrent blocking level (Iblock) in service value.
3. Set the circulating current blocking (OperCCBlock) to On, and the correct
settings for circulating current limit (CircCurLimit) and time delay for
circulating current blocking (tCircCurr) in service value.
4. Set Rline and Xline to Zero.
5. For parallel operation, it is also recommended that settings are confirmed for
parallel group membership, governed by the TnRXOP setting in the Parameter
Setting tool under Main menu/Settings/Setting group N/Control/
TransformerVoltageControl(ATCC,90)/VCPx/ParCtrl
In the Parameter Setting, 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 IED 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
1MRK 504 088-UEN C
"Minimum Circulating
"Master
Installation and commissioning manual