Siemens SIPROTEC 4 7UT6 Series Manual page 377

•
Read out the differential and restraint currents under Measured Values → Percentage → Measured
Values Ι Diff; Ι Stab.
In "Web-Monitor" the differential and restraint currents are displayed as a graph in a characteristics
diagram (2.22.9.1
–
The differential currents
than the through-flowing test currents.
– The restraint currents
test currents.
– If there are differential currents in the size of the restraint currents (approximately twice the
throughflowing 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, matching of the meas-
ured 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 (Section
Data
For all kinds of power transformers, addresses 311 and 312 for side 1 under "Object Data with Trans-
formers" 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 accordingly 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 measuring location 1 under "Current Trans-
former Data for 3- phase Measuring Locations" and accordingly the parameters for the other meas-
uring 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 Loca-
tions" and accordingly the parameters for the other measuring location(s) under test.
For single-phase busbar protection, address 381 under "Object Data with Busbars (1-phase Connec-
tion) with up to 6 or 9 or 12 feeders" and addresses 562 and 563 under "Current Transformer Data
for singlephase Busbar Protection" 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 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 current path.
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016
Web-Monitor).
Diff L1: , Diff L2: , Diff L3: must be low, i.e. at least one scale less
Res. L1: , Res. L2: , Res. L3: correspond to twice the through-flowing
1):
Mounting and Commissioning
3.3 Commissioning
2.1.4 Power System
377