Section 11
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.
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.
11.1
Transformer Voltage Control ATCC
11.1.1
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)
.
1MRK 511 360-UEN A
Section 11
Primary injection testing
Bay control REC670 2.1 IEC
191
Commissioning manual
