3.3 Commissioning
403
7UT613/63x Manual
C53000-G1176-C160-2
– If there are differential currents in the size of the restraint currents (approximately
twice the through-flowing test current), you may assume a polarity reversal of the
current transformer(s) at one side. Check the polarity again and set it right after
short-circuiting all six current transformers. If you have modified these current
transformers, repeat the angle test.
– If there are differential currents which are nearly equal in all three phases, match-
ing of the measured values may be erroneous. Wrong vector group of a power
transformer can be excluded because it should already have been detected
during the phase angle test. Re-check the settings for current matching. These
are mainly the data of the protected object (Power System Data 1, Section 2.1.4):
For all kinds of power transformers
, addresses 311 and 312 for side 1 under
„Object Data with Transformers“ and accordingly the parameters for the other
side(s) under test. Furthermore, addresses 512 and 513 for measuring location
M1 under „Current Transformer Data for 3-phase Measuring Locations“, and ac-
cordingly the parameters for the other measuring location(s) under test.
For generators
, motors, reactors, addresses 361 and 362 under „Object Data
with Generators, Motors or Reactors“, and addresses 512 and 513 for measur-
ing location 1 under „Current Transformer Data for 3-phase Measuring Loca-
tions“ and accordingly the parameters for the other measuring location(s) under
test.
For mini-busbars
(3-phase), address 372 under „Object Data with Mini-Busbars
or Short Lines" (3-phase)“ for feeder 1 and accordingly the parameters for the
other feeder(s) under test, and addresses 512 and 513 for measuring location 1
under „Current Transformer Data for 3-phase Measuring Locations“ and accord-
ingly the parameters for the other measuring location(s) under test.
For single-phase busbar protection
, address 381 under „Object Data with
Busbars (1-phase Connection) with up to 6 or 9 or 12 feeders“ and addresses
562 and 563 under „Current Transformer Data for single-phase Busbar Protec-
tion“ for feeder 1 and accordingly the parameters for the other feeders under test.
If interposed summation transformers are used, matching errors can be caused
by wrong connections at the summation CTs.
• Finally, switch off the test source and the protected object (shut down the genera-
tor).
• If parameter settings have been changed for the tests, reset them to the values nec-
essary for operation.
Please keep in mind that the previous tests must be repeated for each current path.
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