•
Switch on test current.
•
If the starpoint current is available:
Read out the differential and restraint currents I-Diff; I-Rest under Measurement → Percent Values →
Differential and Restraint Currents.
–
The differential current of the restricted earth fault protection Ι
Diff REF
must be low, at least one scale
less than the test current.
–
The stabilisaing current Ι
Stab REF
corresponds to twice the test current.
– If the differential current is in the size of the restraint current (approximately twice the test current),
you may assume a polarity reversal of the single-phase current transformer. Check the polarity again
and compare it with the setting in address 711 EARTH IX1 AT if the auxiliary single-phase input
ΙX1 is under test (see also Section 2.1.4 Power System Data 1 under margin heading “Current Trans-
former Data for single-phase Auxiliary Current Inputs”), or accordingly the parameters for the actual
input under test.
– If there is a differential current which does not correspond to twice the test current, the matching
factor for the 1-phase input may be incorrect. Check the settings relevant for current matching.
These are mainly the data of the protected object and its current transformers (Section 2.1.4 Power
System Data 1):
– for power transformers addresses 313, 323 etc. (dependent on the tested winding), under margin
heading “Object Data with Transformers” and
– in all cases addresses 712, 713 or 722, 723 etc. (depending on the used 1-phase input), under
margin heading “Current Transformer Data for Single-phase Auxiliary Current Inputs”.
•
In all cases (whether or not the starpoint current is available):
Check the differential currents Ι
Diff L1
, Ι
Diff L2
, Ι
Diff L3
.
– The differential currents must be low, at least one scale less than the test current. If considerable
differential currents occur, re-check the settings for the starpoints:
– Starpoint conditioning of a transformer: addresses 313 STARPNT SIDE 1, 323 STARPNT SIDE 2,
etc. (depending on the tested winding) (Section 2.1.4 Power System Data 1, margin heading
“Object Data with Transformers”), as well as
– the assignment of the starpoint current transformer to the 1-phase current input under test: address
251, 252, etc. depending on the input under test, see Section 2.1.4 Power System Data 1 under
margin heading “Assignment of Auxiliary 1-phase Measuring Locations”.
–
Countercheck: The restraint currents of the differential protection Ι
RestL1
, Ι
RestL2
, Ι
Rest L3
are equally
small. If all tests have been successful until now, this should be ensured.
•
Finally, switch off the test source and the protected object (shut down the generator).
•
If parameter settings have been changed for the tests, reset them to the values necessary for operation.
Keep in mind that the previous tests must be repeated for each earthed side.
Current Tests for Busbar Protection
General
For single-phase busbar protection with one device per phase or with summation transformers, the same
checks have to be performed as described in Subsection Symmetrical Current Tests on the Protected
Object. Please observe the following four remarks:
•
Checks are often performed with operational currents or primary testing devices. Please take note of all
warnings you can find in the said section and be aware of the fact that you will require a backup protec-
tion at the supplying point.
•
Checks have to be performed for every current path, beginning with the supplying feeder.
3.3.10
Mounting and Commissioning
3.3 Commissioning
SIPROTEC 4, 7UT6x, Manual 383
C53000-G1176-C230-5, Edition 09.2016
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