Voltage Control Of Parallel Transformers - Hitachi Relion 670 Series Commissioning Manual

Section 12
Primary injection testing
3. In this view, check the following settings:
3.1. Check that Control Mode is set to Manual.
3.2. Operate the tap changer so that the Load Voltage corresponds to the Voltage Set Point.
3.3. Check that neither the Raise or the Lower command are operating. Voltage Deviation
3.4. Compare the values of Bus Voltage and Load Voltage.
For inductive load, the Bus Voltage should be higher than the Load Voltage. If not, current circuits are
incorrect and must be reversed. Incorrect current polarity may be an issue with physical wiring or the
current direction convention selected for the CT analogue input as part of the setting in the PST
setting.
12.1.2

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/IED Settings /Control/
TransformerVoltageControl(90, U↕) /TR8ATCC(90, U↕||):x/ParCtrl . General parallel arrangement
208
should be less than 100%.
UL can be obtained by a vector calculation where IL is the load current and values for RL
and XL are the settings given in primary system ohms.
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Commissioning manual
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