Primary Injection Testing; Transformer Voltage Control Atcc; Load Drop Compensation Function, Ldc - Hitachi Relion 670 Series Commissioning Manual

1MRK 511 403-UEN Rev. L
Section 12
A test with primary current through the protected zone is usually a final check that the current circuits
are correctly connected to the IED protection scheme. It is important to have an appropriate source,
which is able to inject sufficient current in the primary circuit in order to distinguish between noise and
real injected current. Therefore it is recommended that the injection current should be at least 10% of
rated CT primary current.
12.1

Transformer Voltage Control ATCC

12.1.1

Load drop compensation function, LDC

The load drop compensation function can be tested directly with operational currents, in other words,
with the power transformer in service and loaded.
When the system is carrying load there is a difference between the busbar voltage (UB) and the
voltage at the load point (UL). This difference is load dependent and can be compensated by the
ATCC function.
The load current is fed into the ATCC function where parameters corresponding to the line data for
resistance and inductance are set. The voltage drop calculated by the LDC is proportional to the
voltage drop in the system up to the load point.
In the IED, this voltage is subtracted from the measured busbar voltage (UB) and the result,
corresponding to the voltage at the load point (UL) is presented to the ATCC function for the
purposes of voltage regulation. This voltage will be lower (if resistive or inductive load current is
applied) than the Uset voltage and ATCC increases the voltage in order to achieve the correct
system voltage at the load point.
1. Confirm the PST settings for Rline and Xline.
If the function LDC is set to Zero, this test is omitted.
2. Open the voltage control display on the LHMI in Main Menu /Control /Commands /
TransformerVoltageControl (ATCC, 90) .
Bay control REC670
Commissioning manual

Primary injection testing

Whenever it becomes necessary to work on primary equipment, it is essential that all
the necessary switching, locking, earthing and safety procedures are observed and
obeyed in a rigid and formalized manner. Operating and testing procedures should
be strictly followed in order to avoid exposure to live equipment.
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Section 12
Primary injection testing
IP10812-1 v1
SEMOD65857-3 v3
SEMOD65857-8 v2
SEMOD176327-3 v3
SEMOD176327-117 v5
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